Pressure gauge for determining first pressure of medium

Abstract

The invention relates to a pressure gauge (1) for determining a first pressure (p1) of a medium (2), comprising:-a pressure sensor (3) having a ceramic body part (4) and having a ceramic measuring diaphragm (6) which is connected to the ceramic body part by means of a joint (5), the first pressure (p1) being applicable to the measuring diaphragm (6); -a housing sleeve (7) having an interior (8) and having a contact surface (9), the pressure sensor (3) being arranged in the interior (8) and being supported on the contact surface (9) in an edge region (6a) of the measuring diaphragm (6); and-a first sealing element (10) and a second sealing element (11) arranged between the contact surface (9) and the pressure sensor (3), the second sealing element (11) surrounding the first sealing element (10) such that an intermediate space (12) is formed between the first sealing element (10) and the second sealing element (11); and-at least one ventilation opening (13) which is designed and arranged in the housing sleeve (7) in such a way that a gas exchange occurs between the intermediate space (12) and the surroundings (14) of the pressure gauge (1).

Description

Technical Field

[0001] The present invention relates to a pressure gauge for determining a first pressure of a medium. Background Technology

[0002] In pressure measurement techniques, absolute pressure gauges, differential pressure gauges, and relative pressure gauges are known. An absolute pressure gauge determines the dominant pressure of a process medium absolutely (i.e., relative to a vacuum), while a differential pressure gauge determines the difference between two different pressures of a process medium. In the case of a relative pressure gauge, the pressure of the process medium to be measured is determined relative to a reference pressure, where the dominant atmospheric pressure in the environment surrounding the relative pressure gauge is used as the reference pressure.

[0003] A pressure gauge has a pressure-sensitive measuring element, a so-called pressure sensor, to which pressure is applied, respectively, to a first surface and a second surface. In the case of a relative or absolute pressure gauge, the pressure of the process medium to be determined acts on the first surface of the pressure sensor, while the absolute pressure or reference pressure acts on the second surface. In the case of a differential pressure gauge, a first pressure and a second pressure of the process medium are applied to the two surfaces, respectively. The measuring element bends according to the existing relative pressure, which is formed by the difference between the pressures applied to the two surfaces. This bend is converted into an electrical signal by an electronic unit, which depends on the relative pressure and can then be used for further processing or evaluation. In this case, capacitive pressure sensors and piezoresistive pressure sensors can be particularly distinguished. Endress+Hauser Group manufactures and sells various such pressure gauges.

[0004] Ceramic pressure sensors include, for example, a ceramic body and a ceramic measuring diaphragm, which is pressure-sealed to the body using an active hard solder to form a measuring chamber. Furthermore, the pressure sensor typically includes a transducer for converting the pressure-dependent deformation of the measuring diaphragm into a raw electrical signal, and a raw signal path extending through the body. The transducer can be, for example, a capacitive transducer or a resistive transducer. The raw signal path typically includes at least one electrical feedthrough through the body. Besides ceramic pressure sensors, silicon chips are also referred to as pressure sensors, and they are typically bonded to a silicon substrate.

[0005] Specifically, ceramic pressure sensors are typically inserted into the pressure gauge housing using sealing elements, which seal the interior of the housing relative to the medium. Typically, sealing rings made of elastomers are used as sealing elements. Due to their elastic properties, these can compensate for the different linear expansion of the pressure sensor and housing during temperature changes, thereby reducing mechanical stress in the area of ​​the measuring diaphragm and maintaining high measurement accuracy even under temperature variations. However, a drawback of such elastic sealing rings is their poor sealing performance relative to certain gaseous media such as hydrogen. These media can penetrate the housing's interior through such sealing rings and damage internal components, ultimately causing the pressure gauge to fail over time.

[0006] Therefore, the object of the present invention is to provide a ceramic pressure gauge that has a long service life, especially in hydrogen-containing media. Summary of the Invention

[0007] According to the present invention, this objective is achieved by a pressure gauge for determining a first pressure of a medium, the pressure gauge comprising: - A pressure sensor having a ceramic body portion and a ceramic measuring diaphragm connected to the ceramic body portion by means of a joint, wherein a first pressure can be applied to the measuring diaphragm. - A housing sleeve having an interior and a contact surface, wherein the pressure sensor is disposed within the interior and supported on the contact surface in the edge region of the measuring diaphragm, and A first sealing element and a second sealing element are disposed between the contact surface and the pressure sensor, wherein the second sealing element surrounds the first sealing element, such that an intermediate space is formed between the first sealing element and the second sealing element. - At least one ventilation opening is designed and disposed in the housing sleeve to allow gas exchange between the intermediate space and the surrounding environment of the pressure gauge.

[0008] According to the invention, a gaseous medium or gaseous components of the medium entering the intermediate space through the first sealing element can escape from the intermediate space into the surrounding environment of the pressure gauge through the at least one vent opening. Due to the gas permeability coefficient of the second sealing element, a gaseous medium or gaseous components of the medium penetrating the space through the first sealing element will typically only slowly enter the rear space of the housing sleeve. The first and second sealing elements are in particular made of or comprise elastomers. The at least one vent opening ensures such a high gas exchange between the intermediate space and the surrounding environment that the entry and accumulation of gaseous medium or gaseous components in the rear space of the housing sleeve is largely avoided. The term "rear space of the housing sleeve" refers to the portion of the interior of the housing sleeve located on the side opposite to the intermediate space of the second sealing element. This ensures a long service life of the pressure gauge, especially in the case of media containing hydrogen. The first and / or second sealing elements are particularly annular.

[0009] In particular, the intermediate space is annular.

[0010] In the development of the pressure gauge according to the invention, the first sealing element is disposed facing the medium, and the second sealing element is disposed facing away from the medium. Specifically, the first sealing element is in contact with the medium, and the second sealing element is disposed on the side of the first sealing element facing away from the medium.

[0011] In one embodiment, the inner diameter of the second sealing element is larger than the outer diameter of the first sealing element.

[0012] In another embodiment, the first sealing element and the second sealing element are made of different materials. The first sealing element may, for example, be designed to have a low permeability coefficient to the liquid and / or solid components of the medium.

[0013] Another embodiment specifies that the second sealing element has a lower gas permeability coefficient than the first sealing element. This ensures that the gaseous medium or gaseous components in the medium pass through the second sealing element into the rear space or intermediate space at a slower speed than they pass through the first sealing element, such that the gaseous medium or gaseous components can escape from the intermediate space through the at least one ventilation opening at a faster speed than they can pass through the second sealing element into the rear space.

[0014] Advantageously, at least one ventilation opening is sealed using a membrane that allows gas to pass through but not moisture. The membrane allows gas exchange between the intermediate space and the surrounding environment while preventing liquids and solids from entering the intermediate space. Such a semi-permeable membrane is made, for example, of a polymer, particularly Gore-Tex®.

[0015] Specifically, the diaphragm is installed within or at the end region of the at least one ventilation opening. The diaphragm can be configured such that it closes the at least one ventilation opening from either the side of the housing sleeve facing the pressure sensor or from the side of the housing sleeve away from the pressure sensor. The diaphragm can be attached, for example, to the outer or inner wall of the housing sleeve. The diaphragm can also be installed within the at least one ventilation opening. Adhesive, welding, or other joining techniques can be used to attach the diaphragm.

[0016] Preferably, the pressure gauge includes multiple ventilation openings. For the purposes of this application, multiple ventilation openings mean providing two or more ventilation openings. By introducing multiple ventilation openings, the gas exchange rate between the intermediate space and the surrounding environment is increased, thereby further reducing the accumulation of the gaseous medium or gaseous components in the rear space. Advantageously, two ventilation openings are arranged opposite each other. In this way, the gas exchange is increased for gaseous media or gaseous components that are lighter or heavier than air, regardless of the installation orientation of the pressure gauge.

[0017] In particular, the plurality of ventilation openings are arranged in a circular pattern. This is especially advantageous in the case of a circular central space.

[0018] In one embodiment, the pressure gauge has a support ring designed to define a defined distance between the first sealing element and the second sealing element. The support ring is disposed within the intermediate space. Aging effects can cause changes in the inner and outer diameters of the first and second sealing elements. Therefore, the support ring prevents the intermediate space from shrinking or expanding, while simultaneously ensuring that the intermediate space corresponds to the at least one ventilation opening. Specifically, the support ring is circular. For example, the support ring comprises or is made of metal.

[0019] In another embodiment, the support ring has at least one axially arranged through hole. By inserting the support ring into the intermediate space, the intermediate space is divided into a side facing the at least one ventilation opening and a side facing away from the at least one ventilation opening. Gas exchange is possible within the intermediate space, i.e., between the side of the intermediate space facing the at least one ventilation opening and the side of the intermediate space facing away from the at least one ventilation opening, thanks to the at least one axially arranged through hole. Preferably, a plurality of through holes are provided in the support ring.

[0020] In its development, the support ring has at least one circumferential recess. Specifically, the at least one recess is a radially circumferential recess. The at least one circumferential recess can be designed as a circumferential groove. The at least one recess is specifically designed for gas exchange along the intermediate space.

[0021] Specifically, the at least one circumferential recess is provided on the side of the support ring facing the at least one ventilation opening and / or on the side facing away from the at least one ventilation opening. Specifically, the at least one circumferential recess is configured such that gas exchange occurs between the at least one recess and the at least one ventilation opening. If the at least one circumferential recess is provided on the side of the support ring facing the at least one ventilation opening, the at least one circumferential recess can be configured and designed to overlap with the at least one ventilation opening. If the at least one circumferential recess is provided on the side of the support ring facing away from the at least one ventilation opening, the at least one axial through-hole can be additionally provided in the support ring to allow gas exchange between the side of the support ring facing away from the at least one ventilation opening and the surrounding environment. Attached Figure Description

[0022] The following is a reference appendix. Figure 1 Figure 8 illustrates the invention in more detail. In the figures: Figure 1 A schematic diagram of a pressure gauge according to the present invention is shown.

[0023] Figure 2 A schematic diagram of a pressure gauge connected to a container according to the present invention is shown.

[0024] Figure 3 : A schematic diagram showing the front view of a pressure gauge according to the present invention.

[0025] Figure 4 An embodiment of a pressure gauge with a diaphragm according to the present invention is shown.

[0026] Figure 5 Another embodiment of a pressure gauge with a diaphragm according to the present invention is shown.

[0027] Figure 6 Another embodiment of a pressure gauge with a diaphragm according to the present invention is shown.

[0028] Figure 7 An embodiment of a pressure gauge with a support ring according to the present invention is shown.

[0029] Figures 8a-8b A schematic diagram of the support ring is shown. Detailed Implementation

[0030] The pressure gauge 1 according to the present invention can be designed as a relative pressure gauge, an absolute pressure gauge, or a differential pressure gauge. Figure 1 The pressure gauge 1 shown has a pressure sensor with a ceramic body portion 4 and a ceramic measuring diaphragm 6. The body portion 4 and the measuring diaphragm 6 are connected to each other by a joint 5, particularly in a pressure-sealed manner, wherein a pressure chamber 22 is enclosed between the body portion 4 and the measuring diaphragm 6.

[0031] The pressure sensor 3 specifically includes an electromechanical transducer (not shown) for detecting pressure-related deformation of the measuring diaphragm 6. This transducer can be designed as a capacitance transducer having at least one capacitor, wherein the capacitance varies according to the deflection caused by the pressure on the measuring diaphragm 6. The at least one capacitor is formed by a measuring electrode on the side of the measuring diaphragm 6 facing the body portion 4 and a counter electrode on the end face of the body portion 4 facing the measuring diaphragm. The pressure-related capacitance of the capacitor is measured via measuring electronics (not shown) connected to the measuring electrode and the counter electrode. The measuring electronics can be designed to convert this capacitance into a pressure-related measurement signal, making it usable for further evaluation and / or processing.

[0032] The pressure gauge 1 also has a housing sleeve 7, which includes an interior 8 and a contact surface 9. The housing sleeve 7 has a cylindrical shape. The contact surface 9 is specifically designed as a protrusion or step. The pressure sensor 3 is disposed in the interior 8 and supported in the edge region 6a of the measuring diaphragm 6 on the contact surface 9 by means of a first sealing element 10 and a second sealing element 11. The first sealing element 10 and the second sealing element 11 are disposed between the contact surface 9 and the pressure sensor 3. In particular, the first sealing element 10 is configured to face or contact the medium 2. The second sealing element 11 surrounds the first sealing element 10, such that an intermediate space 12 is formed between the two sealing elements 10 and 11. This intermediate space is, for example, annular. The inner diameter of the second sealing element 11 may be larger than the outer diameter of the first sealing element 10. In particular, the first sealing element 10 and the second sealing element 11 are disposed in the same plane. The first sealing element 10 and the second sealing element 11 may be made of or include an elastomer. The two sealing elements 10 and 11 may be made of different materials. For example, the material of the second sealing element 11 can be selected to have a lower gas permeability coefficient than that of the first sealing element 10.

[0033] like Figure 2 As shown, the pressure gauge 1 according to the invention can be attached to a container 21 via a process connection 20. The container 21 includes a medium 2, which is, for example, gaseous or includes at least one gaseous component, particularly hydrogen. The gaseous medium 2 or gaseous components of the medium 2 can pass to some extent through the first sealing element 10 into the intermediate space 12. The second sealing element 11 initially ensures that the gaseous medium 2 or gaseous components do not immediately enter the rear space 19 of the housing sleeve. To prevent the gaseous medium 2 or gaseous components from accumulating in the space 12 over time and penetrating into the rear space 19, the pressure gauge 1 has at least one ventilation opening 13. The at least one ventilation opening 13 is designed and provided in the housing sleeve 7 such that gas exchange occurs between the intermediate space 12 and the surrounding environment 14 of the pressure gauge 1. In particular, the at least one ventilation opening 13 is provided such that the at least one ventilation opening 13 overlaps with the intermediate space 12. Through the at least one ventilation opening 13, the intermediate space 12 can be ventilated such that the accumulation of the gaseous medium 2 or gaseous components is largely avoided. The at least one ventilation opening 13 can be provided in the area of ​​the contact surface 9.

[0034] In addition to the embodiments shown (each with two sealing elements 10, 11), more than two sealing elements and more than one intermediate space can be used to prevent the gaseous medium 2 or gaseous components from accumulating in the rear space 9. For example, the second sealing element 11 can be surrounded by a third sealing element (not shown), thereby forming another intermediate space between the second and third sealing elements, which exchanges gas with the surrounding environment of the pressure gauge via additional ventilation openings.

[0035] Replacement Figure 1 and Figure 2 The pressure gauge 1 may have multiple ventilation openings 13, as shown in the single ventilation opening 13. This arrangement of the ventilation openings 13... Figure 3 The diagram shows a front view of the pressure gauge 1 or a plan view of the measuring diaphragm 6. For better understanding, the outlines of the pressure sensor 3, the first sealing element 10, and the second sealing element 11 are shown in dashed lines. In the example shown, a vent opening 13 is provided along the intermediate space 12, i.e., between the first sealing element 10 and the second sealing element 11.

[0036] To prevent moisture from entering the intermediate space 12, a membrane 15 that is permeable to gas but impermeable to moisture can be provided. The membrane 15 is configured to close at least one ventilation opening 13. For example, the membrane 15 is disposed in the end region 13a of at least one ventilation opening 13. Figure 4 As shown. If there are multiple ventilation openings 13, a single diaphragm 15 can close multiple ventilation openings 13, or multiple diaphragms 15 can be provided to close one or more ventilation openings 13. Figure 5 Another arrangement of the diaphragm 15 is shown, which is disposed in the end region 13a of the ventilation opening 13, and... Figure 4 Relatively speaking, the diaphragm 15 can be installed on the outer or inner wall of the housing sleeve 7. Figure 6 The arrangement of the diaphragm 15 within at least one ventilation opening 13 is shown.

[0037] Optionally, the pressure gauge 1 may have a support ring 16, particularly an annular one, such as... Figure 7 - As shown in Figure 8. The support ring 16 is designed to define a defined distance between the first sealing element 10 and the second sealing element 11. The support ring 16 can be designed to prevent changes in the spatial range of the intermediate space 12. The support ring 16 is specifically disposed within the intermediate space 12. For example, the support ring 16 is designed as a separate component inserted into the intermediate space 12. The support ring 16 can also be designed as part of the housing sleeve 7. In particular, the support ring is made of a material that is less prone to deformation compared to an elastomer, such as metal, especially stainless steel or ceramic.

[0038] The support ring 16 may have at least one axially arranged through hole 17. The through hole 17 is specifically designed to allow gas exchange to occur within the two portions of the intermediate space 12 formed by the support ring 16. Figure 7 As can be seen, the intermediate space 12 is divided into two parts by the support ring 16: the upper part, which exchanges gas with the surrounding environment 14 through the ventilation opening 13; and the lower part, which does not exchange gas with the surrounding environment 14 without the axial through hole 17.

[0039] Furthermore, the support ring 16 may have at least one circumferential recess 18. The at least one circumferential recess 18 is specifically designed to improve gas exchange within the intermediate space 12. By introducing at least one recess 18, the gas volume in the intermediate space 12 is increased. For example, at least one recess 18 may be provided on the side of the support ring 16 facing at least one ventilation opening 13 and / or on the side away from at least one ventilation opening 13. The support ring 16 may, for example, be designed such that, after assembly, it fills the entire height between the measuring diaphragm 6 and the housing sleeve 7. In particular, in this case, at least one circumferential recess 18 improves gas exchange within the intermediate space 12. The at least one circumferential recess 18 is particularly annular.

[0040] Of particular advantage, the support ring 16 has at least one axial through hole 17 in addition to at least one circumferential recess 18. Figure 8 shows this arrangement with two circumferential recesses 18, which are provided on the side of the support ring 16 facing at least one ventilation opening 13 and / or on the side away from at least one ventilation opening 13. Figure 8a A support ring 16 with five axial through holes 17 is shown in plan view. The straight line between two points A and B represents the cross-section of the support ring 16, as shown below. Figure 8b As shown. At point B, two circumferential recesses 18 are shown, while at point A, in addition to the two circumferential recesses 18, an axial through hole 17 can also be seen in the cross-section.

[0041] List of reference numerals

[0042] 1. Pressure gauge

[0043] 2. Medium

[0044] 3. Pressure sensor

[0045] 4. Main Body

[0046] 5. Joint

[0047] 6. Measuring the diaphragm

[0048] 6a. Measuring the edge region of the diaphragm.

[0049] 7. Housing sleeve

[0050] 8. Inner cavity

[0051] 9. Contact Surface

[0052] 10 First sealing element

[0053] 11 Second sealing element

[0054] 12 Intermediate Space

[0055] 13 Ventilation openings

[0056] 14 Surrounding Environment

[0057] 15. Membrane

[0058] 16 Support rings

[0059] 17 Through Holes

[0060] 18. Depression

[0061] 19 Rear Space

[0062] 20 Process Adapters

[0063] 21 Containers

[0064] 22 Pressure chambers

Claims

1. A pressure gauge (1) for determining a first pressure (p1) of a medium (2), comprising: - A pressure sensor (3) having a ceramic body portion (4) and a ceramic measuring diaphragm (6) connected to the ceramic body portion by means of a joint (5), wherein a first pressure (p1) can be applied to the measuring diaphragm (6). - A housing sleeve (7) having an interior (8) and a contact surface (9), wherein the pressure sensor (3) is disposed in the interior (8) and supported on the contact surface (9) in the edge region (6a) of the measuring diaphragm (6), and - A first sealing element (10) and a second sealing element (11), the first sealing element (10) and the second sealing element (11) being disposed between the contact surface (9) and the pressure sensor (3), wherein the second sealing element (11) surrounds the first sealing element (10) such that an intermediate space (12) is formed between the first sealing element (10) and the second sealing element (11), and - At least one ventilation opening (13) is designed and provided in the housing sleeve (7) to allow gas exchange between the intermediate space (12) and the surrounding environment (14) of the pressure gauge (1).

2. The pressure gauge (1) according to any one of the preceding claims, in, The intermediate space (12) is annular.

3. The pressure gauge (1) according to any one of the preceding claims, in, The first sealing element (10) is disposed facing the medium (2), and the second sealing element (11) is disposed away from the medium (2).

4. The pressure gauge (1) according to any one of the preceding claims, in, The inner diameter of the second sealing element (11) is larger than the outer diameter of the first sealing element (10).

5. The pressure gauge (1) according to any one of the preceding claims, in, The first sealing element (10) and the second sealing element (11) are made of different materials.

6. The pressure gauge (1) according to any one of the preceding claims, in, The second sealing element (11) has a lower gas permeability coefficient than the first sealing element (10).

7. The pressure gauge (1) according to any one of the preceding claims, in, The at least one ventilation opening (13) is closed by a membrane (15) that allows gas to pass through but not moisture.

8. The pressure gauge (1) according to any one of the preceding claims, in, The diaphragm (15) is attached to the at least one ventilation opening (13) or to the end region (13a) of the at least one ventilation opening (13).

9. The pressure gauge (1) according to any one of the preceding claims, in, The pressure gauge (1) includes multiple ventilation openings (13).

10. The pressure gauge (1) according to any one of the preceding claims, in, The plurality of ventilation openings (13) are arranged in a circular pattern.

11. The pressure gauge (1) according to any one of the preceding claims, in, The pressure gauge (1) has a support ring (16) designed to set a defined distance between the first sealing element (10) and the second sealing element (11).

12. The pressure gauge (1) according to claim 11, in, The support ring (16) has at least one axially arranged through hole (17).

13. The pressure gauge (1) according to any one of claims 11-12, in, The support ring (16) has at least one circumferential recess (18).

14. The pressure gauge (1) according to any one of claims 11-13, in, The at least one circumferential recess (18) is provided on the side of the support ring (16) facing the at least one ventilation opening (13) and / or on the side away from the at least one ventilation opening (13).

Images