Pressure gauge for determining a first pressure of a medium

Abstract

The invention relates to a pressure gauge (1) for determining a first pressure (p1) of a medium (2), having - a sensor bushing (3) with an interior (4), which is designed to fix a pressure sensor (5) in one position, - the pressure sensor (5) having a base body (6) and a measuring diaphragm (7) connected thereto, wherein the measuring diaphragm (7) can be subjected to the first pressure (p1), wherein the pressure sensor (5) is arranged in an end region (4a) of the interior (4), - a rear space (12), which is arranged radially between the sensor bushing (3) and the pressure sensor (5), - a housing bushing (8) having a contact surface (9), wherein the housing bushing (8) surrounds the sensor bushing (3) at least in the end region (4a), so that an intermediate space (10) is formed between the sensor bushing (3) and the housing bushing (8), - the sealing element (11), which is arranged between the contact surface (9) and the pressure sensor (5) and is designed to seal the intermediate space (10) and the rear space (12) from the medium (2), wherein at least one bore (13) is made in the housing bushing (8) and at least one recess (14) is made in the sensor bushing (3), which are arranged and designed in such a way that the rear space (12) can be ventilated with ambient air by means of the at least one bore (13), the intermediate space (10) and the at least one recess (14).

Description

[0001] Pressure sensor for determining a first pressure of a medium

[0002] The invention relates to a pressure sensor for determining a first pressure of a medium.

[0003] In pressure measurement technology, absolute pressure, differential pressure, and gauge pressure sensors are known. Absolute pressure sensors determine the prevailing pressure of a process medium absolutely, i.e., relative to a vacuum, while differential pressure sensors determine the difference between two different pressures of the process medium or media. With gauge pressure sensors, the pressure of the process medium to be measured is determined relative to a reference pressure, with the atmospheric pressure prevailing in the vicinity of the gauge pressure sensor serving as the reference pressure.

[0004] Pressure transducers have a pressure-sensitive measuring element, the so-called pressure sensor, with a pressure applied to its first and second surfaces. In the case of relative or absolute pressure transducers, the pressure of the process medium to be determined acts on the first surface of the pressure sensor, while an absolute or reference pressure acts on the second surface. In the case of differential pressure transducers, a first pressure and a second pressure of a process medium are applied to both surfaces. The measuring element bends depending on the existing relative pressure, which is calculated from the difference between the pressures applied to the two surfaces. This bending is converted by an electronic unit into an electrical signal dependent on the relative pressure, which is then available for further processing or evaluation. A distinction is made between capacitive and piezoresistive pressure sensors, among others.A large number of such pressure sensors are manufactured and distributed by companies in the Endress+Hauser Group.

[0005] A ceramic pressure sensor, for example, comprises a ceramic

[0006] A base body and a ceramic measuring diaphragm, which is pressure-tightly connected to the base body by means of an active brazing alloy, forming a measuring chamber. Furthermore, the pressure sensor typically includes a transducer for converting a pressure-dependent deformation of the measuring diaphragm into an electrical primary signal, as well as a primary signal path extending through the base body. The transducer can be a capacitive or resistive transducer, for example. The primary signal path usually includes at least one electrical feedthrough through the base body. Instead of ceramic pressure sensors, silicon chips, which are usually bonded to a silicon substrate, are also known as pressure sensors.

[0007] Ceramic pressure sensors, in particular, are often inserted into the housing of the pressure transducer using a sealing element, so that the interior of the housing is sealed against the medium. Typically, sealing rings made of an elastomer are used as sealing elements. Due to their elastic properties, these can compensate for the different linear expansions of the pressure sensor and the housing when temperatures change, thereby reducing mechanical stresses in the area of ​​the measuring diaphragm and maintaining high measurement accuracy even during temperature changes. A disadvantage of such elastomer sealing rings, however, is their low impermeability to certain gaseous media, such as hydrogen. These media can penetrate such a sealing ring into the interior of the housing and damage the internal components to such an extent that the pressure transducer fails over time.

[0008] The object of the present application is therefore to provide a pressure sensor which has a long service life, particularly in hydrogen-containing media.

[0009] According to the invention, the object is achieved by a pressure sensor for determining a first pressure p1 of a medium, with

[0010] - a sensor socket with an interior space, which is designed to fix a pressure sensor in a position,

[0011] - the pressure sensor with a base body and a measuring membrane connected thereto, wherein the measuring membrane can be subjected to the first pressure, wherein the pressure sensor is arranged in an end region of the interior space,

[0012] - a rear space which is arranged radially between the sensor socket and the pressure sensor,

[0013] - a housing bushing with a support surface, wherein the housing bushing surrounds the sensor bushing at least in the end region, so that a gap is formed between the sensor bushing and the housing bushing,

[0014] - a sealing element which is arranged between the support surface and the pressure sensor and is designed to seal the intermediate space and the rear space against the medium, wherein at least one bore is made in the housing socket and at least one recess is made in the sensor socket, which are arranged and designed such that the rear space can be ventilated with ambient air by means of the at least one bore, the intermediate space and the at least one recess.

[0015] Holes in the housing bushing have traditionally been used to detect leaks of liquid media. If the sealing element develops a leak and liquid media enters the gap, it can escape from the pressure sensor through the hole, allowing supervisory personnel to detect the leak. The liquid media can also enter the rear chamber, which generally does not affect the determination of the initial pressure. However, if hydrogen-containing gas enters the rear chamber, it can cause permanent damage to internal components of the pressure sensor.

[0016] The at least one bore, the intermediate space, and the at least one recess ensure that gas, in particular hydrogen-containing gas, that has entered the rear space can escape into the environment of the pressure sensor via the at least one recess, the intermediate space, and the at least one bore and can be exchanged for ambient air. The rear space and the intermediate space each border the sealing element or are delimited by a wall of the sealing element facing away from the medium.

[0017] The housing bushing and / or the sensor bushing in particular have a cylindrical base body or are essentially designed as a hollow cylinder. The base body of the pressure sensor can also be cylindrical. The sensor bushing is designed to fix or hold the pressure sensor in a, in particular, predetermined, position. For this purpose, the sensor bushing can have a support surface in the end region against which the pressure sensor rests. A holding device can also be arranged in the interior, which is designed to fix the pressure sensor in position. Furthermore, the sensor bushing can have a holding surface designed to hold the sealing element on the outside.

[0018] Both the sensor socket and the housing socket can have an inner and outer wall, with the gap being located between the inner wall of the housing socket and the outer wall of the sensor socket. Both the base body and the measuring diaphragm are preferably ceramic. The measuring diaphragm is elastically deformable depending on pressure. The sealing element is arranged in particular in the edge area of ​​the measuring diaphragm.

[0019] In particular, four initial holes are drilled into the housing bushing. This ensures a particularly reliable exchange of the gas or gas mixture present in the rear chamber with the ambient air.

[0020] Advantageously, several bores are provided, with two bores arranged opposite each other along a radius of the housing bushing. This ensures that, regardless of the installation position of the pressure sensor, hydrogen or another gas or gas mixture that is lighter than air that has entered the rear chamber can escape from the pressure sensor through the at least one bore. In one embodiment, the at least one recess is designed as a through-bore with a round or rectangular cross-section.

[0021] In particular, four recesses are incorporated into the sensor socket. This ensures a particularly reliable exchange of the gas or gas mixture present in the rear chamber with the ambient air.

[0022] Advantageously, several recesses are provided, with two recesses arranged opposite each other along a radius of the sensor socket. This ensures that, regardless of the installation position of the pressure sensor, hydrogen or another gas or gas mixture that is lighter than air that has entered the rear chamber can escape from the pressure sensor or at least enter the intermediate space through the at least one recess.

[0023] In a further embodiment, the rear space surrounds the pressure sensor radially.

[0024] A further embodiment provides that the rear space is formed by a side surface of the pressure sensor, a side of the sealing element facing away from the medium and the sensor bushing.

[0025] In one embodiment, the intermediate space surrounds the sensor socket radially.

[0026] In a further development, at least one groove is introduced into the sensor socket, which groove opens into the at least one recess and which is designed to guide a gas from the rear space to the at least one recess.

[0027] In particular, the at least one groove is a groove that runs radially around the sensor bushing at least in sections.

[0028] The present invention will be explained in more detail below with reference to the following figures, Fig. 1-4. They show: Fig. 1: an embodiment of a pressure sensor according to the invention in longitudinal section.

[0029] Fig. 2: a further embodiment of a pressure sensor according to the invention in longitudinal section.

[0030] Fig. 3: a cross-sectional view of a pressure sensor according to the invention.

[0031] Fig. 4: a further embodiment of a pressure sensor according to the invention in cross section.

[0032] Fig. 1 shows an embodiment of a pressure measuring transducer 1 according to the invention with a sensor socket 3, a housing socket 8 and a pressure sensor 5. The pressure sensor 5 comprises a base body 6 and a measuring membrane 7 which is connected to the base body 6, in particular by means of a joint 20 and which can be subjected to the pressure p1 of the medium 2.

[0033] The pressure transducer 1 can be configured as an absolute, relative, or differential pressure transducer and can accordingly use, for example, a vacuum, ambient pressure, or another pressure of the medium 2 as a reference pressure. The pressure sensor 5 has an electromechanical transducer (not shown) for detecting a pressure-dependent deformation of the measuring diaphragm. The transducer can be configured as a capacitive transducer with at least one capacitor, wherein the capacitor has a capacitance that changes depending on the pressure-induced deflection of the measuring diaphragm. The at least one capacitor is formed by a measuring electrode applied to the side of the measuring diaphragm facing the base body and a counter electrode applied to an end face of the base body facing the measuring diaphragm.The pressure-dependent capacitance of the capacitor is measured by measuring electronics (not shown) connected to the measuring electrode and the counter electrode. The measuring electronics can be configured to convert the capacitance into a pressure-dependent measurement signal and provide it for further evaluation and / or processing.

[0034] The pressure sensor 5 is arranged in an end region 4a of the interior 4 of the sensor socket 3. The sensor socket 3 is designed to fix the pressure sensor 5 in a position. For example, the sensor socket 3 has a holding device 17 provided for this purpose. A radially arranged rear space 12 is present between the sensor socket 3 and the pressure sensor 5. In particular, the rear space 12 radially surrounds the pressure sensor 5. The rear space 12 can be formed by a side surface 15 of the pressure sensor 5, a side of the sealing element 11 facing away from the medium 2, and the sensor socket 3, in particular an inner wall 3b of the sensor socket 3.

[0035] The housing bushing 8 surrounds the sensor bushing 3 at least in the end region 4a, so that an intermediate space 10 is formed between the sensor bushing 3 and the housing bushing 8, which in particular radially surrounds the sensor bushing 3. The intermediate space 10 borders in particular on a side of the sealing element 11 facing away from the medium 2. The intermediate space 10 can be arranged between an inner wall 8b of the housing bushing 8 and an outer wall 3a of the sensor bushing 3.

[0036] The sealing element 11 is arranged between the support surface 9 and the pressure sensor 5. Optionally, the sensor socket 3 can have a holding surface 18 for securing the sealing element 11. The pressure sensor 5 can be supported on a support surface 19 of the sensor socket 3 and / or fixed in the sensor socket 3 by means of the holding device 17. The sealing element 11 is further designed to seal the rear chamber 12 and the intermediate chamber 10 from the medium 2.

[0037] In the event of a leak in the sealing element 11, the medium 2 can enter the rear chamber 12 and / or the intermediate space 10. In particular, the entry of a medium 2 containing hydrogen gas into the rear chamber 12 can lead to damage to other components arranged in the sensor socket 3 or the differential pressure sensor 1, such as an evaluation unit, which ultimately leads to a failure of the pressure sensor 1.

[0038] To prevent an accumulation of hydrogen gas or a hydrogen gas-containing medium 2 in the rear chamber 12, at least one recess 14 is provided in the sensor socket 3 and at least one bore 13 is provided in the housing socket 8. The at least one bore 13 and the at least one recess 14 can be aligned with one another, although this is not absolutely necessary. The at least one recess 14 can be designed as a through-bore with a round or rectangular cross-section. The at least one recess 14 and the at least one bore 13 are arranged and designed such that the rear chamber 12 can be ventilated with ambient air by means of the at least one bore 13, the intermediate space 10, and the at least one recess 14.By fluidically coupling the rear chamber 12 to the ambient air of the pressure sensor 1 by means of the at least one recess 14, the intermediate space 10 and the at least one bore 13, an exchange of the hydrogen gas contained in the medium 2 in the rear chamber 12 with the ambient air can take place and thus a failure of the pressure sensor 1 can be avoided.

[0039] Since the orientation of the at least one bore 13 and the at least one recess 14 depends on the installation position of the pressure sensor 1, it may happen that the at least one bore 13 is oriented downwards, i.e. towards the floor. In this case, escape of the hydrogen gas from the at least one bore 13 is made more difficult. To avoid such a case, a plurality of bores 13, in particular four bores 13, can be made in the housing bushing 8. For similar reasons, a plurality of recesses 14, in particular four, can also be made in the sensor bushing 3. Of the plurality of bores 13 and / or the plurality of recesses 14, two bores 13 or two recesses 14 can be arranged opposite one another on a radius of the housing bushing 8 or the sensor bushing 3, as shown in Figures 2-3. Figure 4 shows a cross-section of a pressure sensor according to the invention.In order to guide the gas, in particular the hydrogen-containing gas, out of the rear chamber 12, at least one groove 16 can be introduced into the sensor bushing 3, which opens into the at least one recess 14. By introducing the groove 16, the hydrogen gas still rising upwards collects in the at least one groove 16 and is guided along it to the recess 14. The at least one groove 16 can radially encircle the sensor bushing 3 at least partially or even completely.

[0040] List of reference symbols

[0041] 1 pressure sensor

[0042] 2 Medium

[0043] 3 Sensor socket

[0044] 3a Outer wall of the sensor socket

[0045] 3b Inner wall of the sensor socket

[0046] 4 Interior

[0047] 4a End area

[0048] 5 Pressure sensor

[0049] 6 basic bodies

[0050] 7 measuring membrane

[0051] 8 Housing socket

[0052] 8a Outer wall of the housing socket

[0053] 8b Inner wall of the housing socket

[0054] 9 Support surface

[0055] 10 space

[0056] 11 Sealing element

[0057] 12 backcourt

[0058] 13 Hole

[0059] 14 Recess

[0060] 15 side surface

[0061] 16 grooves

[0062] 17 Holding device

[0063] 18 Holding surface

[0064] 19 Support surface

[0065] 20 joints

Claims

Patent claims 1 . Pressure sensor (1 ) for determining a first pressure (p1 ) of a medium (2), with - a sensor socket (3) with an interior (4) which is designed to fix a pressure sensor (5) in a position, - the pressure sensor (5) with a base body (6) and a measuring membrane (7) connected thereto, wherein the measuring membrane (7) can be subjected to the first pressure (p1), wherein the pressure sensor (5) is arranged in an end region (4a) of the interior space (4), - a rear space (12) which is arranged radially between the sensor bushing (3) and the pressure sensor (5), - a housing bushing (8) with a bearing surface (9), wherein the housing bushing (8) surrounds the sensor bushing (3) at least in the end region (4a), so that an intermediate space (10) is formed between the sensor bushing (3) and the housing bushing (8), - the sealing element (11) which is arranged between the support surface (9) and the pressure sensor (5) and is designed to seal the intermediate space (10) and the rear space (12) against the medium (2), wherein at least one bore (13) is made in the housing bushing (8) and at least one recess (14) is made in the sensor bushing (3), which are arranged and designed such that the rear space (12) can be ventilated with ambient air by means of the at least one bore (13), the intermediate space (10) and the at least one recess (14).

2. Pressure sensor (1) according to claim 1, wherein four bores (13) are introduced into the housing bushing (8).

3. Pressure sensor (1) according to one of the preceding claims, wherein a plurality of bores (13) are introduced and two bores (13) are arranged opposite one another on a radius of the housing bushing (8).

4. Pressure sensor (1) according to one of the preceding claims, wherein the at least one recess (14) is designed as a through-bore with a round or rectangular cross-section.

5. Pressure sensor (1) according to one of the preceding claims, wherein four recesses (14) are introduced into the sensor socket (3).

6. Pressure sensor (1) according to one of the preceding claims, wherein a plurality of recesses (14) are introduced and two recesses (14) are arranged opposite one another on a radius of the sensor socket (8).

7. Pressure transducer (1) according to one of the preceding claims, wherein the rear space (12) radially surrounds the pressure sensor (5).

8. Pressure measuring sensor (1) according to one of the preceding claims, wherein the rear space (12) is formed by a side surface (15) of the pressure sensor (5), a side of the sealing element (11) facing away from the medium (2) and the sensor socket (3).

9. Pressure sensor (1) according to one of the preceding claims, wherein the intermediate space (10) radially surrounds the sensor socket (3).

10. Pressure measuring sensor (1) according to one of the preceding claims, wherein at least one groove (16) is introduced into the sensor socket (3), which groove opens into the at least one recess (14) and which is designed to guide a gas from the rear space (12) to the at least one recess (14).

11. Pressure sensor (1) according to claim 10, wherein the at least one groove (16) is a groove which runs radially around the sensor bushing (3) at least in sections.

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