DE102016107235B3 - Differential pressure measuring cell - Google Patents

Abstract

The invention relates to a differential pressure measuring cell, wherein at least one of two counter-bodies (41; 42), between which a measuring diaphragm (2) is pressure-tight, connected to an adjacent support body (51; 52) to form a hydraulic support chamber (8) the hydraulic support chamber (8) has a support (81) with contact surfaces (Fk) between the counter body (41; 42) and support body (51; 52) and between the support (81) extending and communicating with the measuring chamber (61; 62) compensation channel (82), and wherein the hydraulic support chamber (8) is structured so that the contact surfaces (Fk) of the support (81) and the compensation channel (82) are evenly distributed in the hydraulic support chamber (8). The equalization channel (82) of the hydraulic support chamber (8) distributes the pressure (p1; p2) evenly. By the support (81) of the hydraulic support chamber (8) of the counter body (41, 42) on the support body (51, 52) is supported.

Description

The invention relates to a differential pressure measuring cell.

Differential pressure measuring cells have to measure the difference between two static pressures p1 and p2 on a measuring diaphragm, which is arranged to form two hermetically separated measuring chambers between two counter-bodies. The measuring chambers are each acted upon by the pressures p1 and p2 via pressure channels introduced into the counter-bodies. A deflection of the measuring diaphragm is thus a measure of the pressure difference | p1 - p2 |, whereby the deflection of the diaphragm is converted by means of a transducer into an electronic measuring signal. For example, forms in capacitive differential pressure measuring cells, the measuring diaphragm together with a measuring membrane facing and parallel to the measuring membrane and conductive plane of the counter body a capacitor. Thus, the deflection of the measuring diaphragm determines the distance between the condenser, so that the differential pressure acting on the measuring diaphragm can be converted into a measuring signal by means of capacitance measurements. Such a pressure difference measuring cell is for example in the patent DE 103 93 943 B3 described. Pressure difference 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 designs.

Since differential pressure cells are designed to measure small pressure differences p1 - p2 with high static pressures p1, p2 at the same time, the right balance between sensitivity and overload resistance is of key importance. For example, for the measuring range of the pressure difference | p1 - p2 | the following relationship applies: | p1 - p2 | / p1 <1%. Not applicable in a process plant of one of the two pressures (eg p2) reaches | p1 - p2 | / p1 almost 100%. In this case, the differential pressure measuring cell is thus loaded with more than 100 times the measuring range, which corresponds to a very high unilateral pressure load. For differential pressure cells with a very fine measuring range of | p1 - p2 | ~ 10 mbar is the one-sided pressure load in relation to the measuring range correspondingly higher at a typical process pressure of 160 bar. Various designs for designing a differential pressure measuring cell are known in the prior art in order to withstand such a high single-sided pressure load.

A known embodiment is the use of overload membranes, which are hydraulically coupled to the measuring chamber by a further hydraulic channel and a transmission fluid. The pressures are introduced by means of a separation membranes in the hydraulic channels. Due to the overload diaphragm, the maximum pressure acting on the measuring diaphragm can be limited to a limit value for overpressure. Examples of differential pressure cells with overload membranes are in the EP 1 299 701 B1 , of the DE 10 2006 040 325 A1 and the DE 10 2006 057 828 A1 disclosed. A disadvantage of the known solution is that the volume stroke of the transfer fluid requires a large separation membrane area, which in turn leads to increased device dimensions and thus ultimately to increased production costs.

An alternative known embodiment for protecting the differential pressure measuring cell at high pressure on one side therefore represents the use of a membrane bed, on which the measuring membrane can cling to when exceeding a limit value for a one-sided overpressure. Thus, the measuring diaphragm is supported and thus prevents the bursting voltage of the measuring diaphragm is reached in a further increase in pressure. In this case, aspheric membrane beds which approximate the bending line of the measuring membrane at the limit value for the overpressure are particularly suitable. Examples of aspheric membrane beds are in US 4,458,537 A. or the DE 10 2009 046 229 A1 disclosed.

A very high pressure load can also lead to a deformation of the counter body itself. As a result, the stability of the differential pressure measuring cell is significantly influenced, for example by the support function of the membrane beds is impaired. In the context of construction and connection technology of a differential pressure measuring cell, it is therefore intended to enclose the counter-body between two support body, wherein the support body is used for stabilization and can counteract a deformation of the counter body. Typically, the support body is made of a material having a modulus of elasticity which is at least as great as that of the counter body. Thereby, the counter-body can be additionally supported in the case of a one-sided high pressure load, in particular also at such loads which emanate from high unilateral pressures of the opposite measuring chamber (ie the measuring chamber arranged between the opposing counter-body and the measuring diaphragm). Thus, a deformation of the counter body is counteracted. For the best possible support of the counter body on the support body, it is advantageous if there is a stiff connection between the counter body and support body. Examples of a stiffening of the support body / counter body interface are in the JP 57040626 A1 or the DE 10 2012 113 033 A1 disclosed.

At the same time, in addition to increasing the stability in the case of one-sided pressure loading, it is desirable to achieve a high compressive strength overall, ie a high stability with high pressure on both sides. It has been shown that in this case, a remaining notch stress in the region of the connection or joint between measuring diaphragm and counter-body is problematic. To minimize this notch stress is in the DE 10 2014 109 491 A1 proposed to form in each case an additional hydraulic chamber in the connection of counter-body and support body, which communicates via a compensation channel with the measuring chamber. The hydraulic chamber extends in a plane parallel to the measuring diaphragm plane and causes the respective process pressure not only from the measuring chamber on the counter body, but also on the back, namely acting from the hydraulic chambers, acting on the counter body. Since in each case the same pressure prevails in the measuring chamber and the hydraulic chamber, the same pressure acts on the counter body from the end face facing away from the measuring diaphragm and the end face facing the measuring diaphragm. The end face of the mating body and the supporting body is substantially in a plane parallel to the measuring diaphragm plane. In this way, a pressure-dependent deflection of the counter body is significantly reduced and eliminated the problem of notch stresses at the diaphragm stiffeners at a high overload pressure on both sides as far as possible. The achieved by the hydraulic chambers isobaric storage of the counter body thus leads to an increase in pressure resistance.

An embodiment similar to this embodiment is in the American patent specification US 9274 016 B2 disclosed. However, the arrangements disclosed therein are - in contrast to those in the DE 10 2014 109 491 A1 disclosed embodiments - all asymmetrical. Because of this asymmetry, the embodiments disclosed in the American patent are unsuitable for reducing the influence of the static pressure p1, p2 on the measuring signal of the differential pressure measuring cell.

A disadvantage of this in the DE 10 2014 109 491 A1 disclosed hydraulic chamber, however, is that in the hydraulic chamber, a complete hydraulic contact between the counter body and the support body takes place. Thus, the support body can not support the counter body in this area in the case of a one-sided pressure load. Thus, the support body can not counteract any deformation of the counter body here. In order to achieve support at a high one-sided pressure load, but should be provided in particular in the region of the connecting plane between the support body and counter-body, which overlaps with the level of the measuring chamber, supporting elements.

In summary, the solutions known from the prior art each aim at either an optimization of the compressive strength, ie. H. the accuracy and stability of double-sided high pressure load or to increase the stability in one-sided high pressure load.

The invention is therefore based on the object to provide a differential pressure measuring cell, which at the same time has a high stability with both sides and with one-sided pressure load.

• – wobei die Messmembran zwischen dem ersten Gegenkörper und dem zweiten Gegenkörper angeordnet und mit beiden Gegenkörpern druckdicht verbunden ist,
• – wobei zwischen der Messmembran und dem ersten Gegenkörper eine erste Messkammer und zwischen der Messmembran und dem zweiten Gegenkörper eine zweite Messkammer gebildet ist,
• – wobei der erste Gegenkörper und erste Stützkörper und der zweite Gegenkörper und zweite Stützkörper jeweils einen Druckkanal aufweisen, durch den die erste Messkammer mit einem ersten Druck und die zweite Messkammer mit einem zweiten Druck beaufschlagbar ist und
• – wobei der Wandler dazu ausgestaltet ist, ein elektrisches Messsignal aus einer durch die Differenz zwischen dem ersten Druck und dem zweiten Druck bedingte Verformung der Messmembran zu erzeugen;

wobei jeweils die der Messmembran abgewandte Stirnfläche des Gegenkörpers mit der der Messmembran zugewandten Stirnfläche des Stützkörpers druckdicht verbunden ist,
wobei mindestens einer der beiden Gegenkörper mit dem angrenzenden Stützkörper unter Bildung einer hydraulischen Stützkammer verbunden ist,
wobei die hydraulische Stützkammer,

• – eine Abstützung mit Kontaktflächen zwischen Stützkörper und Gegenkörper und
• – einen zwischen der Abstützung verlaufenden und mit der Messkammer kommunizierenden Ausgleichskanal aufweist,

und wobei die hydraulische Stützkammer so strukturiert ist, dass die Kontaktflächen der Abstützung und der Ausgleichskanal gleichmäßig in der hydraulischen Stützkammer verteilt angeordnet sind.The object is achieved by a differential pressure measuring cell, comprising: a measuring diaphragm, a transducer, a first and a second counter body, and a first and a second supporting body,

• Wherein the measuring diaphragm is arranged between the first counter-body and the second counter-body and is pressure-tightly connected to both counter-bodies,
• Wherein a first measuring chamber is formed between the measuring diaphragm and the first counterbody and a second measuring chamber is formed between the measuring diaphragm and the second counterbody,
• - Wherein the first mating body and first support body and the second mating body and second support body each having a pressure channel through which the first measuring chamber with a first pressure and the second measuring chamber can be acted upon with a second pressure, and
• - wherein the transducer is adapted to generate an electrical measurement signal from a caused by the difference between the first pressure and the second pressure deformation of the measuring diaphragm;

wherein each of the measuring membrane facing away from the end face of the counter body is pressure-tightly connected to the measuring membrane facing end face of the support body,
wherein at least one of the two counter-bodies is connected to the adjacent supporting body to form a hydraulic supporting chamber,
the hydraulic support chamber,

• - A support with contact surfaces between the support body and the counter body and
• - Has a running between the support and communicating with the measuring chamber compensation channel,

and wherein the hydraulic support chamber is structured so that the contact surfaces of the support and the compensation channel are arranged distributed uniformly in the hydraulic support chamber.

The hydraulic support chamber of the differential pressure measuring cell according to the invention combines in a simple manner hydraulic and supporting share in the connection plane between the mating body and the support body. Thus, the differential pressure cell of high stability at high pressure on one side and at the same time high stability and accuracy with high pressure on both sides.

The hydraulic components of the hydraulic support chamber ensure that the same pressure acts on the counter body from the rear side (that is, from the side facing away from the measuring diaphragm) from the side of the counter body as from the measuring chamber. Via the compensation channel of the hydraulic support chamber, which runs in the connection plane between the support body and the counter body, a uniform pressure transfer over the entire surface of the hydraulic support chamber is achieved, which ultimately leads to a substantially uniform pressure distribution within the hydraulic support chamber. Since this is important for high stability at high pressure on both sides, this results in a high compressive strength.

Furthermore, the abovementioned isobaric bearing of the counter body leads to a reduction of a systematic error in the measuring signal. A systematic error could, for example in the case of a capacitive differential pressure measuring cell, be caused by a pressure-related increase in the electrode measuring diaphragm distance and an associated shift in the zero point and / or change in the sensitivity.

The support of the hydraulic support chamber leads to contact surfaces between the support body and the mating body. The contact surfaces allow a power transmission from the counter body to the support body in the region of the hydraulic support chamber. This causes the support that is supported at a high one-sided pressure of the counter body on the support body, so that is not deformed at a high one-sided pressure load of the counter body. Thus, for example, a bulging of the counter body is prevented. As a result, the bursting stability of the differential pressure sensor is increased at high one-sided pressure.

As a rule, the measuring chamber has at least one common axis of symmetry with the supporting body and / or counter-body around which the measuring chamber is symmetrically arranged. The axis of symmetry may be, for example, the mirror axis of a mirror symmetry, or else the axis of rotation of a rotational symmetry. The symmetry axis can lie in the plane of the end face of the counter body and / or support body, or be perpendicular to the end face of the counter body and / or support body. Therefore, it is advantageous if the hydraulic support chamber is arranged substantially symmetrically about this common axis of symmetry. Thus, the forces emanating from the measuring chamber act essentially in opposite areas of the counter body as the forces emanating from the hydraulic support chamber.

The entire cross-sectional area of the hydraulic support chamber is divided into supporting and hydraulic areas. A compromise should be found between supporting and hydraulic parts of the hydraulic support chamber. Ideally, the proportion of the compensation channel to the cross-sectional area of the hydraulic support chamber (hydraulic portion) should be equal to the proportion of the support on the cross-sectional area of the hydraulic support chamber (supporting portion). One possibility, for example, is that the hydraulic and the supported parts differ by a maximum of 20%. In extreme cases, however, the supported portion (support) can be substantially larger than the hydraulic (channel) and vice versa.

In one embodiment, certain area proportions should not be exceeded or undershot. In a preferred embodiment of the invention, therefore, the proportion of the support is at least 10% of the cross-sectional area of the hydraulic support chamber and the proportion of the compensation channel at least 10% of the cross-sectional area of the hydraulic support chamber.

In a preferred embodiment of the invention, the hydraulic support chamber has an at least partially round cross-sectional area with a maximum diameter. The cross-sectional area is preferably an ellipse or a circular area, the diameter deviating at most 20% from the diameter of the measuring diaphragm (ie the diameter of the measuring diaphragm in the area of the measuring chamber). Preferably, the diameter of the hydraulic support chamber is equal to the diameter of the measuring diaphragm. By virtue of the at least partially round cross-sectional area in this embodiment, a uniform pressure distribution without stress peaks in the edge regions of the hydraulic support chamber is achieved in a simple manner. If the cross-sectional area of the hydraulic support chamber is adapted to the diameter of the measuring diaphragm (ie deviates by no more than 20% of it), the uniform pressure distribution translates into a balance of forces. This means that the forces acting on the counter-body from the end face facing the measuring diaphragm are substantially equal to the forces acting on the counter-body from the end face facing away from the measuring diaphragm. Thus prevail in the Essentially no resulting forces on the counter body.

In one embodiment of the invention, the contact surface between the mating body and the support body is designed as a loosely fitting contact surface. In the compensation channel of the hydraulic support chamber, a filling oil is usually provided, which can penetrate into the loosely fitting contact surfaces between the mating body and the support body of the hydraulic support chamber. The layer thickness of the filling oil should not exceed a certain thickness in the loosely fitting contact surface. In this embodiment of the invention, therefore, the loosely fitting contact surfaces between the mating body and support body of the hydraulic support chamber are designed so that filling oil penetrating from the compensation channel into the loosely fitting contact surfaces reaches a maximum layer thickness d0 of 100 nanometers. In a preferred development of this embodiment, the maximum layer thickness d0 is 50 nanometers. In a particularly preferred development of this embodiment, the maximum layer thickness d0 is 20 nanometers.

In an alternative embodiment, the contact surface between the mating body and the support body is firmly joined. In this embodiment, the running between the firmly joined contact surfaces of the support channel provides the required pressure transfer within the hydraulic chamber.

The hydraulic support chamber can be formed in various ways, for example, by the counter-body and / or the support body is processed.

In one embodiment of the invention, the support is part of the counter body, and the compensation channel is formed by an introduced into the counter body structuring. In this embodiment, the hydraulic support chamber is thus formed by a structuring of the counter body

In a further embodiment of the invention, the support is part of the support body, and the compensation channel is formed by an introduced into the support body structuring. In this embodiment, the hydraulic support chamber is thus formed by a structuring of the support body.

In a further embodiment of the invention, the support and the compensation channel are formed by a structured inlay introduced into the connection between the support body and the counterbody.

In one development of the invention, the compensation channel is introduced into the support body and / or counterbody with a predeterminable depth in a direction substantially perpendicular to the measurement diaphragm plane. The depth of the equalization channel is greater than 20 microns and less than 200 microns. Preferably, the depth of the compensation channel should be between 50 and 100 microns. The predeterminable depth of the compensation channel depends on the choice of filling oil. The depth should be chosen so that the filling oil is flowable. This depends on the specific choice of filling oil. Typically, in differential pressure measuring cells filling oils are used, which are flowable from a layer thickness of the filling oil of about 20 micrometers. Therefore, an embodiment of the invention provides a depth of the compensation channel between 50-100 microns.

In a particularly advantageous embodiment, a surrounding the hydraulic support chamber edge region of the connection between the support body and the mating body is designed as a fully available and rigid connection. In this embodiment, in the surrounding the hydraulic support chamber edge region as rigid as possible connection between the mating body and the support body.

In this case, a joining material is provided for joining the edge region surrounding the hydraulic support chamber, for example a glass solder, a metallic solder or an adhesive.

In an advantageous development of the invention, in the region surrounding the hydraulic support chamber of the connection between the support body and the mating body, the support body is offset from the support of the hydraulic support chamber in a direction perpendicular to the measuring diaphragm plane and away from the measuring diaphragm by a predeterminable offset (a). As a result of the offset, the joining material can be received in the fully enclosed and rigidly connected edge region surrounding the hydraulic support chamber. In this development, no additional gap is formed by the introduction of the joining material, so that the optimum power transmission is ensured via the contact surfaces in the hydraulic support chamber between the support body and the counter body. The predefinable offset depends on the joining material or should correspond to the thickness of the joining material. Typical value ranges for joining material thicknesses are 5-50 micrometers. In the case of the glass solder, joining material thicknesses of 10-20 micrometers are common.

In a particularly preferred embodiment of the invention, both counter-bodies are connected to the adjacent support body to form a hydraulic support chamber. In this particularly preferred embodiment, for the typical application that both process pressures are very high, a particularly high compressive strength or stability can be achieved at high pressure on both sides.

In a development of this preferred embodiment, the two hydraulic support chambers are designed substantially identical.

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

In a further embodiment, the support body, the counter body and / or the support consists essentially of silicon (Si), of an amorphous or crystalline oxide (SiO 2), carbide (SiC) and / or nitride (Si 3 N 4) of the silicon and / or an amorphous or crystalline oxide (Al 2 O 3) and / or nitride of aluminum (AlN). The carbide of silicon, which can be present in many energetically almost equivalent polytopes, is suitable because of its high hardness. On the other hand, silicon nitride has a slightly lower hardness, but has a high breaking strength in combination with a low coefficient of thermal expansion and a relatively small elastic modulus.

On the basis of the choice of materials, the modulus of elasticity of the components of the differential pressure measuring cell can be influenced. In one development of the invention, the modulus of elasticity of the support body (Es) is adjusted so that it is equal to or greater than the modulus of elasticity of the counterpart body (Eg). As an upper limit, the modulus of elasticity of the support body (Es) in this development should be at most three times as large as the modulus of elasticity of the counterpart body (Eg). In this embodiment, the support body is thus at least as stable as the counter body.

In summary, the invention relates to a differential pressure measuring cell, wherein at least one of two counter-bodies (between which a diaphragm is pressure-sealed) is connected to an adjacent support body to form a hydraulic support chamber, wherein the hydraulic support chamber a support with contact surfaces between the counter body and the support body and one between the Support extending and communicating with the measuring chamber compensation channel, and wherein the hydraulic support chamber is structured so that the contact surfaces of the support and the compensation channel are arranged distributed uniformly in the hydraulic support chamber. Through the compensation channel of the hydraulic support chamber, the pressure p1; p2 evenly distributed. By supporting the hydraulic support chamber of the counter body is supported evenly on the support body.

The invention will be explained in more detail with reference to the following figures. It shows:

1 : A schematic side view of a cross section of the differential pressure measuring cell according to the invention

2a , b, c: A plan view of the hydraulic support chamber of the differential pressure measuring cell according to the invention.

1 is a schematic side view of a cross section of the differential pressure measuring cell according to the invention 1 , In this embodiment, the particularly advantageous embodiment with two hydraulic support chambers 8th , each between counter-body 41 . 42 and supporting body 51 . 52 are shown. Nonetheless, the components described below may also be part of a differential pressure measuring cell according to the invention 1 with only one hydraulic support chamber 8th between the opposing body 41 ; 42 and supporting body 51 ; 52 be. It should be noted that the schematic representation shown here is by no means true to scale.

The measuring membrane 2 , which has a diameter dM, is between the two counter bodies 41 . 42 arranged. The opposing bodies 41 . 42 are with the measuring diaphragm 2 forming the measuring chambers 61 . 62 pressure-tight connected to each other. The two measuring chambers 61 . 62 can each have a pressure channel 7 with the pressures p1 and p2 be applied.

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

For detecting the static pressure p1, p2, at least one further capacitive transducer can be provided, which in each case has an electrode at the measuring diaphragm 2 opposite end face 12a . 12b of the opposite body 41 . 42 or the measuring membrane 2 facing end face 13a . 13b of the support body 51 . 52 having. Similarly, a resistive transducer for detecting the static pressure p1, p2 may be provided, wherein the support body 51 . 52 or counterbody 41 . 42 in this case has deformation-dependent resistance elements. The latter may for example comprise strain gauges, wherein in the case of a differential pressure measuring cell 1 comprising a semiconductor material, piezoresistive resistive elements are preferable.

On the of the measuring membrane 2 facing away faces 12a . 12b the opposing body 41 . 42 is the support body 51 . 52 with the counter body 41 . 42 forming the hydraulic support chamber according to the invention 8th connected. The diameter dS of the hydraulic support chamber 8th is approximately the same size as that of the measuring diaphragm dM, or in a preferred embodiment should not deviate more than 20% from the measuring membrane diameter dM. Ideally, both diameters are essentially the same, so that dS ≅ dM applies.

The hydraulic support chamber 8th has a hydraulic component. The one with the measuring chamber 61 ; 62 connected equalization channel 82 conducts the pressure p1, p2 over the entire cross-sectional area Fq of the hydraulic support chamber 8th further. In the equalization channel 82 the hydraulic support chamber 8th is a filling oil 9 intended. The equalization channel 82 Thus, it runs in a plane parallel to the diaphragm plane ME. At the same time, there is over the entire cross-sectional area Fq of the hydraulic support chamber 8th distributes areas of support 81 where the support 81 through the equalization channel 82 is broken. The support 81 the hydraulic support chamber 82 lead to a contact surface Fk between the opposing body 41 . 42 and supporting body 51 . 52 , The contact surfaces Fk allow a power transmission from the counter body 41 . 42 on the support body 51 . 52 in the area of the hydraulic support chamber 8th ,

The contact surfaces Fk can be loosely fitting or firmly joined. It is possible that in loosely fitting contact surfaces Fk between the counter body 41 . 42 and supporting body 51 . 52 the filling oil 9 which can penetrate. For this reason, the configuration is particularly advantageous in which a remaining gap between the support body and the counter body by the loosely fitting contact surface Fk is so narrow that the filling oil 9 there can reach a maximum layer thickness d0 of less than 100 nanometers.

In the embodiment shown here, the hydraulic support chamber 8th by a structuring of the support body 51 . 52 educated. In alternative embodiments, but also the counter body 41 . 42 be structured, or the compensation channel 82 and the support 81 are formed by the introduction of an inlay.

The equalization channel 82 protrudes with a predetermined depth b in the support body 51 . 52 into it. The depth b of the compensation channel 82 the hydraulic support chamber 8th should be chosen so that the filling oil 9 (which for simplicity is not shown here) can flow. This depends on the specific choice of filling oil 9 from. Typically, in differential pressure cells 1 such filling oils 9 used, starting from a layer thickness of the filling oil 9 of about 20 microns are flowable. Therefore, an embodiment of the invention provides a depth b of the compensation channel 82 between 50-100 microns ago.

By doing that, the equalization channel 82 the hydraulic support chamber 8th with the measuring chamber 61 . 62 communicates, is the side of the measuring chamber 61 . 62 on the counter body 41 . 42 acting pressure p1, p2 identical to the back, from side of the hydraulic support chamber 8th on the counter body 41 . 42 acting pressure p1, p2. This means, especially in the case of the same diameter of the hydraulic support chamber 8th and the measuring diaphragm dS ≅ dM, that there is a balance of power. In this way, approximately no resulting forces act on the opposing body 41 . 42 ; even in the case of high static pressures p1, p2.

At the same time Fk is between counter-body through the contact surfaces 41 . 42 and supporting body 51 . 52 in the area of the hydraulic support chamber 8th which by the support 81 be provided, the possibility of supporting the counter body 41 . 42 on the support body 51 . 52 given. This will cause a deformation of the mating body 41 ; 42 counteracted in the region of the hydraulic support chamber, so that, for example, an outward arching of the counter body 41 is prevented at high one-sided pressure p2.

In the case that the hydraulic support chamber 8th surrounding edge region RB is designed as a fully available and rigid connection is in this edge region RB, the interface between the counter body 41 . 42 and supporting body 51 . 52 a particularly stiff connection. In a further embodiment, in addition, this edge region RB is a predefinable offset a with respect to the support 81 discontinued. This can be done in the border area RB the joining material FM (for example an adhesive, a glass solder, or a metallic solder) required for the fully loaded rigid connection can be accommodated. The edge area RB receiving the joining material FM is shown here as a hatched area.

A top view of the in 1 shown in the side view hydraulic support chamber 8th is in 2a shown. For better orientation is in 1 and 2a a straight line AB (dashed line) is shown, which in both the sectional plane of the side view in 1 as well as in the sectional plane of supervision in 2a lies.

In the in 1 in the side view and in 2a In the embodiment shown in the plan view, the channel-like hydraulic and supporting structures of the hydraulic support chamber 8th each of concentric circles, the concentric circles of the support 81 each with the concentric circles of the compensation channel 82 alternate. Here are the concentric circles of the compensation channel 82 each connected to each other. This is made possible, for example, by the fact that in the concentric circles of the support 81 each a recess is introduced, so that the support 81 is broken through; Another option is additional, in concentric support 81 radially extending channels.

In this way, only a single, coherent equalization channel becomes 82 in the hydraulic support chamber 8th formed, which with the measuring chamber 61 . 62 over the pressure channel 7 in the center of the hydraulic support chamber 8th communicated. The filling oil 9 can thus over the entire cross-sectional area Fq of the hydraulic support chamber 8th spread evenly. The filling oil 9 leading equalization channel 82 is in 2a C each represented by the undulating pattern while the support 81 is shown as a black area. There is a homogeneous distribution of the pressure p1, p2 over the entire cross-sectional area of the hydraulic support chamber 8th reached.

On the other hand is the support 81 over the entire cross-sectional area Fq of the hydraulic support chamber 8th equally distributed. Due to the thus structured hydraulic support chamber 8th are evenly distributed hydraulic and supporting shares available, so that a high compressive strength while supporting the counter body 41 . 42 on the support body 51 . 52 is guaranteed. For the sake of simplicity, the equalization channel 82 and the support 81 each shown as approximately equal in size; Of course, it is within the scope of the invention also possible, the compensation channel 82 and / or the support 81 sections of different width and / or interpreted deep, as long as a total uniform distribution of the supporting shares or the support 81 and the hydraulic components or the compensation channel 82 is present.

An alternative embodiment, by which such a structured hydraulic support chamber according to the invention 8th is achieved, is the supervision of the 2 B shown. In this variant of the invention, there is the compensation channel 82 from radial channel sections, which are connected to each other in the center, so that here too a single, continuous compensation channel 82 is formed. The support 81 consists of segments of the circular cross-sectional area Fq, which lie between the channel sections, wherein the segments of the support 81 preferably the same size.

Another possibility, such a structured hydraulic support chamber 8th is training in 2c shown. In this case, there is the support 81 from cylindrical columns. Because the cylindrical pillars of the support 81 are arranged on concentric circles, the in 2c Case shown very similar to that 2a ,

Further embodiments according to the invention for structuring the hydraulic support chamber 8th are possible. There are no further restrictions on the special configuration or structuring. In principle, a design can also be carried out with the aid of computer-aided component simulations, for example by using the finite element method (FEM) to optimize the geometry with regard to the most uniform possible pressure distribution. It is advantageous, the most uniform possible pressure distribution under the boundary condition of the most economical use of the filling oil 9 to reach. This is desirable on the one hand to the influence of variable process conditions, the volume stroke of the filling oil 9 influence (such as temperature fluctuations) limit. On the other hand, the filling oil should 9 For that reason alone, they are used sparingly to ensure chemical-physical interactions of the filling oil 9 with the counter body 41 . 42 and / or the support body 51 . 52 low, depending on the material and filling oil used 9 the filling oil 9 such as by chemisorption and / or physisorption, the stability of the differential pressure measuring cell 1 can influence.

LIST OF REFERENCE NUMBERS

1

Differential pressure measuring cell

2

measuring membrane

41

first counter body

42

second counter body

51

first support body

52

second support body

61

first measuring chamber

62

second measuring chamber

7

pressure channel

8th

hydraulic support chamber

81

support

82

compensation channel

9

Füllöll

10a

measuring electrode

10b

measuring electrode

11a

the measuring membrane facing end face of the first counter body

11b

the measuring membrane facing end face of the second counter body

12a

the measuring membrane facing away from the end face of the first counter body

12a

the measuring membrane facing away from the end face of the second counter body

13a

the measuring diaphragm facing end face of the first support body

13b

the measuring membrane facing end face of the second support body

14a

membrane electrode

14b

membrane electrode

p1

first pressure

p2

second pressure

Fk

contact surfaces

fq

Cross-sectional area of the hydraulic support chamber

dS

maximum diameter of the cross-sectional area of the hydraulic support chamber

dm

Diameter of the measuring diaphragm

d0

maximum layer thickness of the filling oil

b

predeterminable depth of the compensation channel

ME

Measuring membrane level

RB

the hydraulic support chamber surrounding edge region

FM

Add material

a

predefinable offset

It

Elastic modulus of the support body

Ea

Young's modulus of support

Eg

Young's modulus of the counter body

Claims (18)

Differential pressure measuring cell ( 1 ), comprising: a measuring membrane ( 2 ); a transducer, a first and a second counter body ( 41 . 42 ), and a first and a second support body ( 51 . 52 ), - whereby the measuring membrane ( 2 ) between the first counterbody ( 41 ) and the second counter body ( 42 ) and with both counter bodies ( 41 . 42 ) is connected pressure-tight, - wherein between the measuring diaphragm ( 2 ) and the first counterbody ( 41 ) a first measuring chamber ( 61 ) and between the measuring membrane ( 2 ) and the second counter body ( 42 ) a second measuring chamber ( 62 ), wherein the first counterbody ( 41 ) and the first support body ( 51 ) and the second counter body ( 42 ) and the second support body ( 52 ) each have a pressure channel ( 7 ) through which the first measuring chamber ( 61 ) with a first pressure (p1) and the second measuring chamber ( 62 ) is acted upon with a second pressure (p2) and - wherein the transducer is configured to an electrical measurement signal from a by the difference between the first pressure (p1) and the second pressure (p2) caused deformation of the measuring diaphragm ( 2 ) to create; each of the measuring membrane ( 2 ) facing away from the end face ( 12a . 12b ) of the counterbody ( 41 ; 42 ) with the measuring membrane ( 2 ) facing end face ( 13a . 13b ) of the supporting body ( 51 ; 52 ) is connected pressure-tight, wherein at least one of the two counter-body ( 41 ; 42 ) with the adjacent support body ( 51 ; 52 ) to form a hydraulic support chamber ( 8th ), wherein the hydraulic support chamber ( 8th ), - a support ( 81 ) with contact surfaces (Fk) between support body ( 51 ; 52 ) and counterbody ( 41 ; 42 ) and - one between the support ( 81 ) and with the measuring chamber ( 61 ; 62 ) communicating equalization channel ( 82 ), and wherein the hydraulic support chamber ( 8th ) is structured so that the contact surfaces (Fk) of the support ( 81 ) and the equalization channel ( 82 ) evenly in the hydraulic support chamber ( 8th ) are arranged distributed. Differential pressure measuring cell ( 1 ) according to claim 1, wherein the proportion of the support ( 81 ) at least 10% of the cross-sectional area (Fq) of the hydraulic support chamber ( 8th ), the share of the equalization channel ( 82 ) at least 10% of the cross-sectional area (Fq) of the hydraulic support chamber ( 8th ) is. Differential pressure measuring cell ( 1 ) according to claim 1 or 2, wherein the hydraulic support chamber ( 8th ) has an at least partially round cross-sectional area (Fq) with a maximum diameter (dS), and wherein the diameter (dS) is at most 20% of the diameter (dM) of the measuring membrane ( 2 ) deviates. Differential pressure measuring cell ( 1 ) according to claim 2 or 3, wherein the cross-sectional area (Fq) is an ellipse or a circular area. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein the diameter (d) of the hydraulic support chamber ( 8th ) equal to the diameter (dM) of the measuring membrane ( 2 ). Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims 1-5, wherein the contact surface between (Fk) between counter-body ( 41 ; 42 ) and supporting body ( 51 ; 52 ) is designed as a loosely fitting contact surface. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims 1-5, wherein the contact surface between (Fk) between counter-body ( 41 ; 42 ) and supporting body ( 51 ; 52 ) is firmly attached. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein the support ( 81 ) Part of the counterbody ( 41 ; 42 ) and the equalization channel ( 82 ) through a into the counter body ( 41 ; 42 ) introduced structuring is formed. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein the support ( 81 ) Part of the support body ( 51 ; 52 ) and the equalization channel ( 82 ) by a in the supporting body ( 51 ; 52 ) introduced structuring is formed. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein the support ( 81 ) and the equalization channel ( 82 ) by a in the connection between counter body ( 41 ; 42 ) and supporting body ( 51 ; 52 ) introduced, structured inlay are formed. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein the compensation channel ( 82 ) with a predeterminable depth (b) in a direction perpendicular to the measuring membrane plane (ME) in the counter body ( 41 ; 42 ) and / or supporting body ( 51 ; 52 ), wherein the depth (b) is greater than 20 micrometers and less than 200 micrometers. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein a hydraulic support chamber ( 8th ) surrounding edge region (RB) of the connection between the counterbody ( 41 ; 42 ) and supporting body ( 51 ; 52 ) is designed as a fully available and rigid connection. Differential pressure measuring cell ( 1 ) according to claim 12, in which the hydraulic support chamber ( 8th ) surrounding edge region (RB) the connection between the counter body ( 41 ; 42 ) and supporting body ( 51 ; 52 ) in a direction perpendicular to the measuring diaphragm level (ME) and of the measuring diaphragm ( 2 ) facing away by a predetermined offset (a) relative to the support ( 81 ) of the hydraulic support chamber ( 8th ) for receiving the joining material (FM) in which the hydraulic support chamber ( 8th ) surrounding, fully loaded and rigidly connected edge region (RB). Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein in each case both counter-bodies ( 41 . 42 ) with the adjacent support body ( 51 . 52 ), each forming a hydraulic support chamber ( 8th ) are connected. Differential pressure measuring cell ( 1 ) according to claim 14, wherein the two hydraulic support chambers ( 8th ) are configured identically. Differential pressure measuring cell ( 1 ) according to at least one of the preceding claims, wherein the counterbody ( 41 ; 42 ), the supporting body ( 51 ; 52 ) and / or the support ( 81 ) consists of a ceramic material. Differential pressure measuring cell according to at least one of the preceding claims, wherein the counter body ( 41 ; 42 ), the supporting body ( 51 ; 52 ) and / or the support ( 81 - of silicon (Si), - of an amorphous or crystalline oxide of silicon (SiO ₂ ), of an amorphous or crystalline carbide (SiC) of silicon and / or of an amorphous or crystalline nitride (SiN) of silicon, - and or consists of an amorphous or crystalline oxide of aluminum (Al ₂ O ₃ ) and / or nitride of aluminum (AlN). Differential pressure measuring cell according to at least one of the preceding claims, wherein the modulus of elasticity (Es) of the supporting body ( 51 ; 52 ) and / or the modulus of elasticity (Ea) of the support ( 81 ) equal to or greater than the modulus of elasticity (Eg) of the counterpart body ( 41 ; 42 ), wherein the elastic modulus (Es) of the supporting body ( 51 ; 52 ) and / or the modulus of elasticity (Ea) of the support ( 81 ) at most three times as large as the elastic modulus (Eg) of the counter body ( 41 ; 42 ).

Images