Manufacturing of adiabatic diaphragms for pressure sensors, pressure sensors with adiabatic diaphragms, and pressure sensors with adiabatic diaphragms.

Abstract

To provide an insulated diaphragm for a pressure sensor, a pressure sensor equipped with an insulated diaphragm, and a method for manufacturing a pressure sensor equipped with an insulated diaphragm. [Solution] The present invention relates to an insulated diaphragm 2 for a pressure sensor 1 for determining the pressure of a fluid medium F, comprising a diaphragm 3 and a coating 5, wherein when the insulated diaphragm 2 is in use, the diaphragm surface 6 of the diaphragm 3 faces the fluid medium F. The coating 5 comprises a lamellar structure 7, wherein for most of the lamellars 9, the longitudinal extension DL of the lamellars 9 normal to the diaphragm plane XY is at most half the transverse extension DQ of the lamellars 9 parallel to the diaphragm plane XY.

Description

Technical Field

[0001] The present invention relates to a heat-insulating diaphragm for a pressure sensor, a pressure sensor including the heat-insulating diaphragm, and a method of manufacturing a pressure sensor including the heat-insulating diaphragm. The heat-insulating diaphragm includes a diaphragm and a coating.

Background Art

[0002] A diaphragm separates a fluid medium in a first chamber from a second chamber. In the field of pressure measurement technology, a pressure sensor often includes a measuring device, for example, a measuring device, and a diaphragm that separates the measuring device from a fluid medium of a determined pressure, for example, a gaseous measurement medium and / or a liquid measurement medium. The diaphragm usually includes a diaphragm surface facing the fluid medium.

[0003] In the case of a pressure sensor, the pressure of the fluid medium acting on the area of the diaphragm is transmitted to the measuring device with as little loss as possible. At the same time, the measuring device can be located directly on the side of the diaphragm facing outward from the fluid medium, or can be connected to the diaphragm by an additional element, for example, a fixed piston or a fluid medium or a gel that transmits a pressure or a proportional force to the measuring device.

[0004] When sensors are used in environments with high-temperature fluid media, such as internal combustion engines or furnaces, melting furnaces, or applications with process heat such as chemical and industrial processes, high temperatures can damage the measuring device. In this case, thermal energy from the fluid media is transmitted to the measuring device through the diaphragm, potentially destroying the device or at least interfering with pressure determination. For example, many piezoelectric measuring devices have a pyroelectric effect, which, in addition to mechanically induced piezoelectric charge separation, causes further pyroelectric charge separation that detrimentally distorts pressure measurements. The temperature at which the measuring device is damaged depends on the type of measuring device. This can be solved by placing the measuring device at a greater distance, for example, by using a very long piston or long hydraulic line for pressure transmission. However, such solutions require an excessive amount of space. In addition, long pistons or long hydraulic lines affect the sensor's natural frequency.

[0005] In particular, the occurrence of temperature peaks can potentially damage the measuring device.

[0006] European Patent No. 0145146 describes a pressure sensor comprising a diaphragm having a surface that faces a fluid medium in a combustion region and deflects in response to the adjacent pressure level. A second diaphragm is positioned apart from a first diaphragm and deflects in response to the deflection of the first diaphragm. The second diaphragm is designed to generate a signal indicating the deflection of the second diaphragm. A force transmission means or pressure transmission means, which can be a fluid or piston, between the first and second diaphragms transmits the movement of the first diaphragm to the second diaphragm, reducing heat transfer from the first to the second diaphragm by a large geometric space. The drawback here is that the pressure sensor has significantly larger dimensions than a corresponding sensor that does not have a first diaphragm and force transmission means. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] European Patent No. 0145146 [Non-patent literature]

[0008] [Non-Patent Document 1] Boettinger, W., Kattner, U., Moon, K., and Perepezko, J. (2006), NIST Recommended Practice Guide: DTA and Heat-Flux DSC Measurements of Alloy Melting and Freezing, Elsevier, Kidlington. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] An object of the present invention is to improve the diaphragm so as to reduce the aforementioned drawbacks. Another object of the present invention is to provide a diaphragm that delays the inflow of thermal energy through the diaphragm. [Means for solving the problem]

[0010] This objective is resolved by the features of the independent claim.

[0011] The present invention relates to an adiabatic diaphragm for a pressure sensor for determining the pressure of a fluid medium in a first space, the adiabatic diaphragm being designed to separate the first space from a second space. The adiabatic diaphragm is designed to be substantially parallel to the diaphragm plane. The diaphragm plane is defined by a first spatial axis and a second spatial axis. The first and second spatial axes are linearly independent and form a two-dimensional coordinate system. A third spatial axis is positioned normal to the diaphragm plane. The first, second, and third spatial axes form a three-dimensional coordinate system. The adiabatic diaphragm comprises a diaphragm and a coating. When the adiabatic diaphragm is used, the diaphragm surface of the diaphragm faces the fluid medium. The coating is positioned on the diaphragm surface.

[0012] According to the present invention, the coating comprises a lamellar structure. For most of the lamellae, the longitudinal extension of the lamellar normal to the diaphragm plane is at most half the transverse extension of the lamellar parallel to the diaphragm plane. As a result, the transverse-to-longitudinal ratio of the lamellar is at least 2, where the transverse direction is parallel to the diaphragm plane and the longitudinal direction is parallel to a third spatial axis.

[0013] A lamellar structure is considered to be a structure that primarily contains lamellae. Lamellars are flat particles having a transverse-to-length ratio of at least 2, mainly separated from other lamellae by boundaries, such as cavities. For example, cavities contain one or more hollow spaces or one or more gaps between lamellae. Therefore, coatings can be described as hybrid materials having cavities and lamellae.

[0014] Being predominantly lamellar means that at least 50% of the particles are in lamellar form. Being predominantly separated means that more than 50% of the surface area of ​​a lamellar is separated from other lamellae by a boundary, thereby allowing the lamellae to at least partially contain material bonding and / or force-fitting and / or shape-fitting connections with one another. The term "and / or" is understood as non-exclusive separation, also known as "inclusive or inclusive." In a lamellar structure, lamellae are superimposed on each other so that their longer extensions are as parallel as possible. Nearly parallel is understood as the directional deviation of the longer extensions of the lamellae being less than 30°.

[0015] Lamellar structures are characterized by low thermal conductivity, at least 50% lower than that of coated diaphragms. Thermal conductivity is standardized to a unit of length, in units of W·(mK). -1 It is expressed in watts per meter per Kelvin. Thermal conductivity is not specified for a single layer, but refers to a macroscopic object.

[0016] In hybrid materials, heat spreads primarily along the longer dimensions of the lamellae within the lamellar structure. Therefore, the hybrid material with a lamellar structure has directional thermal conductivity, which conducts heat better along the longer dimensions of the lamellae than along the shorter dimensions. However, the hybrid material has significantly lower overall thermal conductivity in all directions than a solid body made from the same material as the lamellae. The solid body is understood to have the same chemical composition as the lamellae but lacks the lamellar structure with its cavities.

[0017] Therefore, an insulating diaphragm, i.e., a diaphragm with a coating having a lamellar structure on the diaphragm surface facing the fluid medium, has slower heat intrusion to the side of the diaphragm facing outward from the fluid medium than an uncoated diaphragm of the same material and dimensions. This allows the diaphragm to protect the side facing outward from the fluid medium from high temperatures over long periods that could damage elements on that side. This extends the service life of these elements, such as measuring devices like piezoelectric crystals or ceramics, piezoresistive materials or strain gauges, as well as electronic components, insulators, or other elements particularly installed within pressure sensors, compared to an uncoated diaphragm. In addition, undesirable temperature dependence of the measurement signal, such as that caused by the pyroelectric effect of some piezoelectric measuring elements, is reduced. The coating with a lamellar structure also protects the diaphragm material itself from temperature peaks. The coating also has the advantage of slowing heat intrusion to the diaphragm itself.

[0018] A coating with a lamellar structure is more flexible than the corresponding solid body made of the same material. This makes it possible to use the coating on flexible elements such as diaphragms for pressure sensors without significantly reducing the flexibility of the insulating diaphragm, especially compared to a diaphragm with the same thickness made of a solid body of the same material. It is preferable that the elastic modulus of the coating and the elastic modulus of the diaphragm are of similar magnitudes.

[0019] Advantageously, the lamellae are largely separated from each other. The coating contains cavities. The cavities are hollow spaces, gaps, or cracks / microcracks having extensions of at least 0.2 μm and separating the lamellae from each other at least partially. The cavities may contain air or another fluid medium, or may have a different chemical composition from the lamellae. Separation is achieved at least partially by the cavities in the coating. The cavities separate the individual lamellae from each other, thereby reducing heat conduction from one lamellae to the next compared to the corresponding solid body.

[0020] As a rule for diaphragms for pressure sensors, the insulating diaphragm is usually a flat element along the diaphragm plane. A third axis normal to the diaphragm plane is also referred to as the longitudinal axis. The lamellar structure of the coating is characterized by the fact that most of the lamellae are designed to be flat. The protruding transverse extension of the flat lamellae on the diaphragm plane (extension along the transverse direction, i.e., parallel to the diaphragm plane) is at least twice the protruding longitudinal extension of the lamellae on the third axis (longitudinal axis). The transverse extension and the longitudinal extension are determined in accordance with ASTM E3 (Standard Guide for Preparation of Metallographic Specimens) in combination with microscopy techniques such as optical microscopes and scanning electron microscopes (SEM).

[0021] Such a coating can preferably be applied by a thermal spraying process. In the thermal spraying process, thermally at least partially molten particles of the material collide with the diaphragm surface, whereby they are mechanically deformed into flat lamellae on the diaphragm surface or on previously applied lamellae. Adding at least partially molten particles to already solidified lamellae results in a force fit / shape fit connection caused by cavities such as gaps or voids that separate most of the lamellae from each other rather than a material bond connection. Thus, the cavities mainly run parallel to the diaphragm plane. The particles have a particle size between 5 μm and 120 μm, whereby the particle size is determined by laser diffraction.

[0022] In particular, thermal spraying refers to plasma spraying according to DIN EN ISO14917:2017 Thermal spraying - Terminology, Classification (ISO14917:2017).

[0023] Advantageously, the diaphragm is made of a metallic material. Metallic materials usually have a substantially higher temperature resistance. It is particularly advantageous if the diaphragm is made of a nickel-based or cobalt-based alloy, as is common in pressure sensors used to determine high temperatures. The diaphragm has a particularly advantageous chromium content of 15% by weight (15 weight percent).

[0024] The coating advantageously has a coating thickness of at least 100 μm. The coating thickness, i.e., the layer thickness of the coating or what is simply referred to as the thickness, is determined in the direction normal to the diaphragm plane. Usually, the coating thickness of the coating is understood to be in the direction normal to the coated surface. Such a coating delays the ingress of heat from the fluid medium to the outer-facing side, i.e., into the second space, by at least 10% compared to the same uncoated diaphragm.

[0025] In one embodiment of the heat-insulating diaphragm, the coating comprises a metallic material, preferably a nickel-based self-fluxing alloy. Nickel-based self-fluxing alloys and equivalent self-fluxing alloys in the field of thermal spraying are described in DIN EN ISO14920:2015. The coating is preferably made according to the ratio equation in weight percent (empirical formula) of nickel, chromium, silicon, and boron, particularly preferably Ni 76 Cr 15 Si5B4. Alternatively, the coating comprises a nickel alloy with nickel as the main component and having a high proportion of oxide formers such as aluminum, chromium, and yttrium, or a cobalt alloy with cobalt as the main component and having a high proportion of oxide formers such as aluminum, chromium, and yttrium.

[0026] In a further alternative embodiment of the insulating diaphragm, the coating comprises a ceramic material, preferably yttrium oxide-stabilized zirconium oxide. The yttrium oxide-stabilized zirconium oxide comprises at least 90% by weight of zirconium oxide (ZrO2) and 6% to 8% by weight of yttrium oxide (Y2O3).

[0027] Alternatively, the coating of the insulating diaphragm may also include the metallic material and the ceramic material mentioned above. This can be produced, for example, by allowing particles of the metallic material and the ceramic material, which are at least partially molten, to collide with the surface to be coated, referred to as the coating surface, and solidify therein.

[0028] In one embodiment of the insulating diaphragm, an adhesion-promoting layer is preferably placed between the diaphragm surface and the coating. The adhesion-promoting layer comprises a nickel-based and / or cobalt-based and / or iron-based alloy, the nickel-based and / or cobalt-based and / or iron-based alloy comprising additional elements having a high affinity for oxygen, such as aluminum and refractory metals. The standard molar enthalpy of formation of the additional elements (standard enthalpy of formation of solid oxides at 298.15 K and 1 atm) must have a high affinity for oxygen less than -150 kJ / mol. The standard molar enthalpy of formation and affinity for oxygen are based on published data from Boettinger, W., Kattner, U., Moon, K., and Perepezko, J. (2006), NIST Recommended Practice Guide: DTA and Heat-Flux DSC Measurements of Alloy Melting and Freezing, Elsevier, Kidlington. For example, the adhesion-promoting layer is applied by thermal spraying and has a largely anisotropic structure. The adhesion-promoting layer is advantageous because it improves the adhesion of the coating to its lamellar structure compared to an insulating diaphragm where the coating is applied directly to the diaphragm. For example, the adhesion-promoting layer can reduce the deviation in the coefficient of thermal expansion between the insulating layer and the diaphragm.

[0029] Preferably, the diaphragm is 8-10 -6 K -1 from 15.10 -6 K -1The coating has a linear thermal expansion coefficient, or more simply, a diaphragm expansion coefficient, within a temperature range of 20°C to 100°C. Furthermore, it is preferable that the coating's linear thermal expansion coefficient, or coating expansion coefficient, deviates from the diaphragm expansion coefficient by less than 40%. This is advantageous because a linear thermal expansion coefficient that differs by more than 40% can create high stress between the diaphragm and the coating, especially when the diaphragm is exposed to significantly different temperatures, such as storage temperatures compared to high-temperature applications. This stress can cause delamination of the coating, potentially negatively impacting the insulation of the adiaphragm or even damaging it. Therefore, matching the diaphragm expansion coefficient with the coating expansion coefficient within a maximum deviation of 40% is advantageous for the coating's temperature resistance.

[0030] Advantageously, the coating has both thermal conductivity in the diaphragm plane and thermal conductivity perpendicular to the diaphragm plane. Preferably, the thermal conductivity in the diaphragm plane is greater than the thermal conductivity perpendicular to the diaphragm plane. Therefore, in addition to the reduction in thermal conductivity due to cavities in the lamellar structure, heat transfer to the second space is also slowed down due to the fact that thermal energy is mainly dissipated laterally along the diaphragm plane and is not efficiently conducted to the diaphragm along the longitudinal axis.

[0031] Typically, diaphragms also possess thermal conductivity. The thermal conductivity of a diaphragm is greater than that of any coating.

[0032] The present invention also relates to a sensor for determining the pressure of a fluid medium. The sensor has an embodiment of the adiabatic diaphragm described. The sensor has a pressure-side end facing the fluid medium. The sensor comprises a housing. In addition, the sensor comprises a measuring device. The fluid medium exerts pressure on the adiabatic diaphragm, and the adiabatic diaphragm is operably connected to the measuring device. The adiabatic diaphragm slows heat transfer from the fluid medium into the internal space of the housing, which is typically a second space separated by the diaphragm from a first space containing the fluid medium.

[0033] Advantageously, the insulating diaphragm is positioned at the pressure-side end of the sensor (1) facing the fluid medium. The measuring device is airtightly isolated from the fluid medium by the insulating diaphragm. This is advantageously achieved by a material bonding connection between the housing and the insulating diaphragm. The housing may have at least partially a housing coating, which is identical to and merges with the coating of the insulating diaphragm. This has the advantage that heat transfer through the housing into the second chamber, or through the portion of the housing facing the fluid medium, is also slowed. The coating is applied to the housing surface as needed. Similar to the corresponding embodiment of the insulating diaphragm, an adhesion-promoting layer can be pre-applied to the housing surface.

[0034] The sensor according to the present invention is manufactured, for example, by performing at least the following steps. However, this manufacturing is not limited to the manufacturing method described and can also be carried out using techniques other than thermal spraying, such as 3D printing, laser cladding, etc.

[0035] The manufacture of a sensor with an insulating diaphragm includes at least the following substeps: providing a housing comprising the diaphragm positioned at the pressure end of the sensor; determining the coating surface, wherein the coating surface includes at least the diaphragm surface; the coating surface may be pre-roughened by sandblasting, glass bead blasting, or a similar process, depending on the surface condition; and applying a coating to the coating surface by thermal spraying. Metal or ceramic particles are moved toward the coating surface. The particles are at least partially melted and impact the coating surface in an at least partially molten state. The particles are deformed into a lamellar shape by their kinetic energy upon impact. The majority of the particles solidify into a lamellar shape, forming lamellae of the lamellar structure of the coating.

[0036] Optionally, the manufacture of a sensor having an insulating diaphragm may also include a step in which the coated surface includes at least a portion of the housing surface referred to as the housing surface.

[0037] Optionally, the manufacture of a sensor having an insulating diaphragm may also include the step of providing at least partially a binder layer primarily on the coating surface, wherein the adhesion-promoting layer corresponds to the adhesion-promoting layer of the corresponding embodiment of the insulating diaphragm.

[0038] The present invention will be described in more detail below with reference to the figures, using exemplary embodiments. [Brief explanation of the drawing]

[0039] [Figure 1] This is a schematic diagram of a sensor equipped with an insulated diaphragm. [Figure 2] This is a schematic cross-sectional view of a sensor comprising a first embodiment of an insulating diaphragm. [Figure 3] This is a schematic cross-sectional view of a sensor comprising another embodiment of an insulated diaphragm. [Figure 4]This is a schematic cross-sectional view of a sensor comprising another embodiment of an insulated diaphragm. [Figure 5] This is a schematic cross-sectional view of a sensor comprising another embodiment of an insulated diaphragm. [Figure 6] This figure shows detail A of an embodiment of the insulating diaphragm as shown in Figure 2 or Figure 3. [Figure 7] This figure shows detail B of an embodiment of the insulating diaphragm as shown in Figure 4 or Figure 5. [Figure 8] This figure shows detail C of the insulated diaphragm. [Figure 9] This is a schematic diagram of the manufacturing process for an insulating diaphragm. [Figure 10] This figure shows a further embodiment of the insulating diaphragm, detail B, as shown in Figure 4 or Figure 5. [Figure 11] This is a schematic cross-sectional view of a sensor comprising another embodiment of an insulated diaphragm. [Figure 12] This is a schematic cross-sectional view of a sensor comprising another embodiment of an insulated diaphragm. [Modes for carrying out the invention]

[0040] Figure 1 shows a schematic diagram of a sensor 1 equipped with an adiaphragm 2. The sensor 1 is designed to determine the pressure of a fluid medium F in a first chamber R1. The sensor 1 has a pressure-side end 10 facing the fluid medium F. In addition, the sensor 1 is equipped with a housing 12. Although not visible in Figure 1, inside the sensor, the sensor 1 is equipped with a measuring device 13. The measuring device is located in a second chamber R2 within the housing 12. The adiaphragm 2 is located at the pressure-side end 10. The sensor extends along a third axis Z, also referred to as the longitudinal axis Z. The adiaphragm 2 is designed to be substantially parallel to the diaphragm plane (XY), so that the diaphragm plane XY is defined by a first spatial axis X and a second spatial axis Y, the second spatial axis extending into the figure plane. The adiaphragm is shown as a diaphragm 3 with a coating 5 (shown as a dotted line).

[0041] Figure 2 shows a schematic cross-sectional view of the details of a sensor 1 having a first embodiment of the insulated diaphragm 2. The insulated diaphragm 2 comprises a diaphragm 3 and a coating 5. When the insulated diaphragm 2 or sensor 1 is in use, the diaphragm surface 6 of the diaphragm 3 faces the fluid medium F. The coating 5 is disposed on the diaphragm surface 6.

[0042] All embodiments shown in the figures are schematic diagrams. Dimensions, particularly thickness, coating thickness, and length, are selected for illustrative purposes only and should not be understood as specifications for element dimensions or the relative dimensions of elements.

[0043] Figure 2 shows a schematic cross-sectional view of a sensor 1 comprising a first embodiment of the insulated diaphragm 2. The schematic cross-sectional view shows sections of the partial view of the sensor 1 from Figure 1 along the first axis X and the third axis Z. The measuring device 13 is located in a second chamber R2 within the housing 12. For example, the measuring device comprises a piezoelectric crystal or piezoelectric ceramic, or other piezoelectric resistance material or strain gauge operably connected to the diaphragm 3 and generating a measurable electrical signal when force or pressure is applied. The insulated diaphragm 2 comprises a diaphragm 3 and a coating 5. As is typical for the sensor 1, the diaphragm 3 is located at the pressure-side end 10 of the sensor 1 and connected to the sensor housing 12 by material bonding connections 11, such as welded joints or soldered joints. However, the diaphragm 3 may also be designed integrally with the housing 12, and the present invention is not limited to a two-piece design but explicitly includes an integrally formed assembly of the diaphragm 3 and housing 12. The insulated diaphragm 2 is designed to transmit the pressure of the fluid medium F in the first chamber R1 to the measuring device 13. Thus, the insulated diaphragm 2 is operably connected to the measuring device 13. In this embodiment, the coating 5 extends both over the diaphragm 2 and over a portion of the housing 12, transitioning seamlessly from the diaphragm 2 to the portion of the housing. The lamellae 9, as shown in Figures 6 and 8, are each aligned such that their longer transverse extensions DQ are substantially parallel to the coated surface 15, and it is understood that the spatial alignment of the transverse dimensions changes at the transition from the diaphragm surface 6 to the surface of the housing 12. The transverse dimensions of the lamellae 9 on the diaphragm surface are substantially parallel to the first axis X and the second axis Y (normal to the plane in the figure 2), and the transverse dimensions of the lamellae 9 on the housing 12 coating are substantially parallel to the third axis Z.

[0044] In this embodiment and later embodiments of the insulating diaphragm 2, the same reference numerals indicate the same elements within the embodiment.

[0045] Figure 3 shows a schematic cross-sectional view of sensor 1 with a further embodiment of the insulating diaphragm 2. This embodiment differs from the embodiment in Figure 2 only in the coating 5. In this embodiment of Figure 3, the coating 5 extends to the diaphragm surface 6. The housing 12 does not contain a coating. This is particularly advantageous for front-sealing sensors where the fluid medium does not come into contact with the housing 12, or only comes into contact with it slightly, when the sensor 1 is in use.

[0046] Figure 4 shows a schematic cross-sectional view of sensor 1 with a further embodiment of the insulating diaphragm 2. Similarly, in this embodiment of the insulating diaphragm 2, the same reference numerals refer to the same elements as in the previously shown embodiment. In this embodiment, an additional adhesion-promoting layer 4 is added between the coating 5 and the diaphragm. The adhesion-promoting layer 4 improves the adhesion of the coating 5 to the diaphragm 2. The adhesion-promoting layer 4 is optional and can be omitted for economic reasons if the adhesion of the coating 5 to the diaphragm 2 is sufficient for the individual application. In this embodiment, the adhesion-promoting layer 4 extends across both the diaphragm surface 6 and the housing surface 16. Thus, the adhesion-promoting layer 4 is positioned between the coating surfaces 6, 15 and the coating 5.

[0047] Figure 5 shows a schematic cross-sectional view of the sensor 1 with a further embodiment of the insulating diaphragm 2. Similarly, in this embodiment of the insulating diaphragm 2, the same reference numerals refer to the same elements as in the embodiments shown in Figures 2 to 4. The embodiment in Figure 5 differs from the embodiment in Figure 4 only in the coating 5 and the adhesion-promoting layer 4. In this embodiment in Figure 5, both the adhesion-promoting layer 4 and the coating 5 extend onto the diaphragm surface 6. The housing 12 does not contain a coating. As with the embodiment of the insulating diaphragm 2 in Figure 3, this is particularly advantageous for front-sealing sensors where the fluid medium does not come into contact with the housing 12, or comes into only minimal contact, when the sensor 1 is in use.

[0048] Figure 6 schematically shows detail A of coating 5, illustrating the coating 5 in both the embodiment of the insulating diaphragm 2 according to Figure 2 and the embodiment of the insulating diaphragm 2 according to Figure 3. Therefore, the section of detail A is shown in both Figure 2 and Figure 3. The lamellae 9 shown in Figures 6 and 8 are arranged on the diaphragm 3. Note that this is a schematic diagram and neither the number of lamellae 9 nor the transverse extensions DQ or longitudinal extensions DL, nor their ratio to each other, constitutes a limitation. According to the present invention, the ratio of transverse extensions DQ to longitudinal extensions DL for most of the lamellae 9 is at least 2. The coating 5 comprises cavities 8 that largely limit the lamellae 9 to each other. The coating 5 is shown with a coating thickness 17 measured from the diaphragm 3 in the direction normal to the coating surface.

[0049] Figure 7 schematically shows detail B of coating 5, illustrating both the coating 5 of the embodiment of the insulating diaphragm 2 according to Figure 4 and the coating 5 of the embodiment of the insulating diaphragm 2 according to Figure 5. Therefore, the section of detail B is shown in both Figure 4 and Figure 5. The lamellae 9 shown in Figures 7 and 8 are arranged on the diaphragm 3. Note that this is a schematic diagram and neither the number of lamellae 9 nor the transverse or longitudinal extensions, nor their ratios to each other, constitutes a limitation. According to the present invention, the ratio of transverse extension DQ to longitudinal extension DL for most of the lamellae is at least 2. The coating 5 comprises cavities 8 that largely limit the lamellae 9 to each other. The cavities 8 are, for example, hollow spaces 8 or gaps 8 as schematically shown in Figure 7. An adhesion-promoting layer 4 is arranged between the coating 5 and the diaphragm 3. The diagrams of the adhesion-promoting layer 4 and the cavities 8 are also schematic and are not intended to represent any dimensions or size ratios to the diaphragm 3 or lamellae 9. In the diagram in Figure 7, the adhesion-promoting layer 4 also has a lamellar structure. The adhesion-promoting layer 4 can also be added by thermal spraying in the same manner as the coating 5, and differs from the coating 5 only in its material. The mere schematic diagram in Figure 7 does not allow for any definitive conclusions about size ratios. The coating 5 is shown using a coating thickness 17 measured from the adhesion-promoting layer 4 in the direction normal to the coating surface. The coating thickness 17 is understood to be the average thickness of the coating 5. The adhesion-promoting layer thickness 18 can be measured and determined in the same manner as the coating thickness 17.

[0050] An alternative adhesion-promoting layer 4 is schematically shown in Figure 10. The adhesion-promoting layer does not have a lamellar structure and can be added, for example, by vapor deposition, other physical vapor deposition techniques, or laser cladding, or it can be produced by sintering a thermally sprayed laser of a self-flowing alloy.

[0051] Naturally, it should be noted that at least one additional layer may be placed between the adhesion-promoting layer 4 and the diaphragm 3 shown in Figures 4, 5, 7, and 10. The adhesion-promoting layer 4 does not necessarily need to be in direct contact with the diaphragm 3.

[0052] Figure 8 schematically shows detail C of coating 5, illustrating both the coating 5 of all embodiments of the insulating diaphragm 2 according to Figure 6 and the coating 5 of all embodiments of the insulating diaphragm 2 according to Figure 7. Therefore, the section of detail C is shown in both Figure 6 and Figure 7. Figure 8 schematically shows how the longitudinal extension DL and transverse extension DQ of the lamella 9 should be determined. Figure 8 shows the lamella 9 of the lamella coating 5 in a cross-sectional view. However, the transverse extension DQ of the lamella 9 is substantially the same in all sections parallel to the diaphragm plane XY. The lamella 9 has a substantially flattened circular shape with the transverse extension DQ being the longer dimension. The longitudinal extension DL is determined perpendicular to the coating surface 15. The transverse extension DQ is determined parallel to the coating surface 15. When the coating 5 is placed on the diaphragm surface 6 together with the intermediate adhesion promoting layer 4, the transverse dimension is parallel to the diaphragm plane XY, and the longitudinal dimension is parallel to the third axis Z, also referred to as the longitudinal axis Z.

[0053] The adhesion-promoting layer 4 in the embodiment shown in Figure 7 is almost identical to the coating 5 in Figure 8, differing mainly in the choice of material.

[0054] In all illustrated embodiments, the majority of the lamellae 9 is flat, and thereafter, the projecting transverse extension DQ of the flat lamellae 9 onto the diaphragm plane XY is at least twice the projecting longitudinal extension DL of the lamellae onto a third axis Z, also referred to as the longitudinal axis (Z).

[0055] In all embodiments of the illustrated thermal insulation diaphragm 2, the coating 5 includes a coating thickness 17 of at least 100 μm. The coating thickness 17 of the coating 5 is measured normal to the coating surface 15. For the coating 5 on the diaphragm surface 5, this is normal to the diaphragm plane XY, and for the coating on the housing 12, this is normal to the respective housing surface 16.

[0056] The coating 5 in all embodiments of the insulated diaphragm 2 shown may be applied by a thermal spraying process, as schematically shown in Figure 9.

[0057] The manufacture of the sensor 1 having an insulating diaphragm according to any of the embodiments described comprises at least the following substeps, some of which are schematically shown in Figure 9. Figure 9 shows a provided diaphragm 3, which is positioned at the pressure-side end 10 of the sensor 1 (similar to that in Figure 1, though not shown). A coating surface 15 is defined, and in this exemplary example, the coating surface includes at least the diaphragm surface 6. The coating 5 is applied to the coating surface 15 by thermal spraying, thereby moving metal or ceramic particles P in the direction of the coating surface 15 as indicated by arrows on the particles P. The particles P are at least partially melted and collide with the coating surface 15 in an at least partially melted state. Due to their kinetic energy upon impact, the particles P are deformed into a lamellar shape and mostly solidify in a lamellar shape to form lamellae 9 of the lamellar structure 7 of the coating 5.

[0058] Naturally, the embodiments of the insulating diaphragm 2 disclosed herein can be combined with each other. This document also expressly includes embodiments having combinations of properties described herein.

[0059] In particular, as schematically shown in Figure 11, an embodiment of the sensor 1 having an insulating diaphragm 2 is also possible in which an adhesion-promoting layer 4 is placed between the diaphragm 3 and the coating 5, but no adhesion-promoting layer 4 is placed between the housing 12 or housing surface 16 and the coating 5. Alternatively, as schematically shown in Figure 12, an embodiment of the sensor 1 having an insulating diaphragm 2 is also possible in which an adhesion-promoting layer 4 is placed between the housing 12 or housing surface 16 and the coating 5, but no adhesion-promoting layer 4 is placed between the diaphragm 3 and the coating 5. [Explanation of Symbols]

[0060] 1. Sensor, pressure sensor 2. Insulated diaphragm 3 diaphragm 4 Adhesion promotion layer 5 Coating 6 Diaphragm surface 7 Lamellar structure 8. Cavity, hollow space, gap 9 Lamella 10 Pressure side end 11. Material bonding 12 Housing 13 Measuring devices, sensors 14 Housing Coating 15. Coated surface 16 Housing surface 17 Coating thickness, layer thickness, thickness 18. Adhesion-promoting layer thickness DQ Transverse Extension DL Longitudinal Extension F Fluid medium P particles R1 First Chamber R2 Second Chamber X First spatial axis, first transverse axis XY diaphragm plane Y: Second spatial axis, second transverse axis Z is the third spatial axis, the longitudinal axis.

Claims

1. An insulated diaphragm (2) for a pressure sensor (1) for determining the pressure of a fluid medium (F) in a first chamber (R1), wherein the insulated diaphragm (2) is positioned to separate the first chamber (R1) from a second chamber (R2), and the insulated diaphragm (2) is designed to be substantially parallel to a diaphragm plane (XY), the diaphragm plane (XY) being given by a first spatial axis (X) and a second spatial axis (Y), and a third spatial axis (Z) being positioned normal to the diaphragm plane (XY), and the insulated diaphragm (2) comprises a diaphragm (3) and a coating (5), In an insulating diaphragm, when the insulating diaphragm (2) is used, the diaphragm surface (6) of the diaphragm (3) faces the fluid medium (F), and a coating (5) is disposed on the diaphragm surface (6), wherein the coating (5) comprises a lamellar structure (7), the coating includes lamellae (9), and for most of the lamellae (9), the longitudinal extension (DL) of the lamellae (9) normal to the diaphragm plane (XY) is at most half of the transverse extension (DQ) of the lamellae (9) parallel to the diaphragm plane (XY).

2. The insulating diaphragm (2) according to claim 1, characterized in that the coating comprises cavities (8) in the form of, for example, hollow spaces (8), the lamellae (9) are largely separated from each other, and the separation is at least partially achieved by the cavities (8) within the coating (5).

3. The thermal insulation diaphragm (2) according to claim 1 or 2, characterized in that the majority of the lamella (9) is designed to be flat, and so that the protruding transverse extension (DQ) of the flat lamella (9) onto the diaphragm plane (XY) is at least twice the protruding longitudinal extension (DL) of the lamella onto the third axis (Z) referred to as the longitudinal axis (Z).

4. The insulating diaphragm (2) according to any one of claims 1 to 3, characterized in that the coating (5) is applied by a thermal spraying process.

5. The heat insulating diaphragm (2) according to any one of claims 1 to 4, characterized in that the diaphragm (3) is made of a metal material, or the diaphragm (3) is made of a nickel-based or cobalt-based alloy, and the diaphragm (3) has a chromium content of more than 15% by weight.

6. The insulating diaphragm (2) according to any one of claims 1 to 5, characterized in that the coating (5) has a coating thickness (17) of at least 100 μm, which is simply referred to as thickness (17), and the coating thickness (17) of the coating (5) is normal to the diaphragm plane (XY).

7. The insulating diaphragm (2) according to any one of claims 1 to 6, characterized in that the coating (5) includes a metallic material, preferably a nickel-based self-fluxing alloy, or a nickel alloy having a high proportion of oxide formers such as aluminum, chromium, and yttrium, or a cobalt alloy having a high proportion of oxide formers such as aluminum, chromium, and yttrium.

8. The insulating diaphragm (2) according to any one of claims 1 to 7, characterized in that the coating (5) comprises a ceramic material, such as yttrium oxide-stabilized zirconium oxide, or the coating (5) comprises a metal material and a ceramic material.

9. An insulating diaphragm (2) according to any one of claims 1 to 8, wherein an adhesion promoting layer (4) is disposed between the diaphragm surface (6) and the coating (5), and the adhesion promoting layer (4) comprises a nickel-based and / or cobalt-based and / or iron-based alloy, and the nickel-based and / or cobalt-based and / or iron-based alloy comprises additional elements having a high affinity for oxygen, such as aluminum and refractory metals, and the standard enthalpy of formation of the additional elements having a high affinity for oxygen must be less than -150 kJ / mol.

10. The diaphragm (2) is 8.10 －６ K －１ From 15.10 －６ K －１ The insulating diaphragm (2) according to any one of claims 1 to 9, wherein the coating (5) has a linear thermal expansion coefficient in the temperature range of 20°C to 100°C, or more simply, a diaphragm expansion coefficient, and the coating (5) has a linear thermal expansion coefficient that is more simply called a coating expansion coefficient, and the coating expansion coefficient deviates from the diaphragm expansion coefficient by less than 40%.

11. The insulating diaphragm (2) according to any one of claims 1 to 10, characterized in that the coating (5) has thermal conductivity in the diaphragm plane (XY), the coating (5) has thermal conductivity perpendicular to the diaphragm plane (XY), and the thermal conductivity in the diaphragm plane (XY) is greater than the thermal conductivity perpendicular to the diaphragm plane (XY).

12. The insulating diaphragm (2) according to any one of claims 1 to 11, characterized in that the coating (5) has thermal conductivity in the diaphragm plane (XY), the coating has thermal conductivity perpendicular to the diaphragm plane (XY), the diaphragm (3) has thermal conductivity, and the thermal conductivity of the diaphragm (3) is greater than any thermal conductivity of the coating (5).

13. A sensor (1) for determining the pressure of a fluid medium (F), wherein the sensor (1) comprises a pressure-side end (10) facing the fluid medium (F), a housing (12), and a measuring device (13), characterized in that the sensor (1) comprises an insulating diaphragm (2) as described in any one of claims 1 to 12.

14. The sensor (1) according to claim 13, characterized in that the insulating diaphragm (2) is positioned at the pressure side end (11) of the sensor (1), hermetically separating the measuring device from the fluid medium (F), the housing (12) and the insulating diaphragm (2) are connected by a material bond (11), the housing (12) comprises at least a portion of a housing coating (14), the housing coating is designed in the same way as the coating (5) of the insulating diaphragm (2) and merges into the coating.

15. Manufacturing of a sensor (1) according to claim 13 or 14, wherein the manufacturing comprises at least the following substeps: a substep of providing a housing (12) having a diaphragm (3) positioned at the pressure side end (10) of the sensor (1); a substep of determining a coating surface (15) wherein the coating surface (15) includes at least the diaphragm surface (6); and a substep of applying a coating (5, 14) to the coating surface (15) by thermal spraying, wherein metal or ceramic particles (P) are moved toward the coating surface (15), the particles (P) are at least partially melted, the particles (P) collide with the coating surface (15) in the at least partially melted state, the particles (P) are deformed into a lamellar shape by their kinetic energy upon impact, the majority of the particles (P) solidify into a lamellar shape, forming lamellae (9) of the lamellar structure (7) of the coating.

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