System consisting of a pressure measuring cell and a closure body, pressure sensor, method for producing a system, and use

Abstract

The invention relates to a system (1) consisting of a pressure measuring cell (2) and a closure body (3), wherein the pressure measuring cell (2) has a main part (4) and a ceramic measuring membrane (6) which is connected to the main part (4) by means of a first joint (5), the pressure (p1) of the medium (9) can be applied to the measuring membrane (6), a pressure chamber (7) is provided between the measuring membrane (6) and the main part (4), the main part (4) has a reference air opening (8) connected to the pressure chamber (7), the closure body (3) is connected, by means of a second joint (11), to an end face (10) of the main part (4) facing away from the measuring membrane (6), and the closure body (3) is situated relative to the main part (4) in such a way that the reference air opening (8) is exposed or the reference air opening (8) is closed by the closure body (3). The invention further relates to a pressure sensor and to a method.

Description

[0001] System consisting of a pressure measuring cell and a closure body, pressure sensor, method for manufacturing a system and use

[0002] The invention relates to a system comprising a pressure measuring cell and a closure body, a pressure sensor, a method and a use.

[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, where the prevailing atmospheric pressure in the vicinity of the gauge serves as the reference pressure.

[0004] Pressure sensors have a pressure-sensitive measuring element, on whose first and second surfaces pressure is applied. In the case of relative or absolute pressure sensors, the pressure of the process medium to be measured 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 sensors, a first and a second pressure of the process medium are applied to each surface. The measuring element bends depending on the relative pressure, which is 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, among other things, between capacitive and piezoresistive pressure sensors.A large number of such pressure sensors are manufactured and distributed by companies of the Endress+Hauser Group.

[0005] A ceramic pressure sensor, for example, comprises a ceramic base and a ceramic measuring diaphragm, which is pressure-tightly connected to the base using an active brazing alloy, forming a pressure chamber. The pressure sensor also typically includes a transducer for converting the pressure-dependent deformation of the measuring diaphragm into a primary electrical signal, as well as a primary signal path extending through the base. The transducer can be, for example, a capacitive or a resistive transducer. The primary signal path usually includes at least one electrical feedthrough through the base. To determine a relative pressure, a reference air vent in the base is required, through which ambient pressure is provided in the pressure chamber. For determining an absolute pressure, however, the pressure chamber must be pressure-tight from the environment.Therefore, different base bodies are needed for the production of absolute and relative pressure measuring cells.

[0006] It is therefore an object of the present invention to provide a system which can be used for the manufacture of both an absolute and a relative pressure measuring cell.

[0007] The problem is solved according to the invention by a system according to claim 1, a pressure sensor according to claim 7, a method according to claim 9 and a use according to claim 10.

[0008] With regard to the system, the problem is solved according to the invention by a system comprising a pressure measuring cell and a closure body, wherein the pressure measuring cell has a base body, in particular a ceramic one, and a ceramic measuring membrane connected to the base body by means of a first joining point, wherein the measuring membrane can be subjected to the pressure of the medium, wherein a pressure chamber is arranged, in particular enclosed, between the measuring membrane and the base body, wherein the base body has a reference air opening connected to the pressure chamber, wherein the closure body is connected to an end face of the base body facing away from the measuring membrane by means of a second joining point, wherein the closure body is arranged relative to the base body such that the reference air opening is free or that the reference air opening is closed by the closure body.

[0009] In particular, if the system is designed for determining and / or monitoring a relative pressure, the closing element is arranged relative to the base body in such a way that the reference air opening is free, and if the system is designed for determining and / or monitoring an absolute pressure, the closing element is arranged relative to the base body in such a way that the closing element closes the reference air opening.

[0010] Depending on the orientation of the sealing element relative to the base body, either an absolute pressure measuring system or a relative pressure measuring system is formed. This eliminates the need for different base bodies for absolute and relative pressure applications. Consequently, the same components—the pressure measuring cell with reference air orifice and the sealing element—are advantageously used for both absolute and relative pressure measuring systems, simplifying their manufacture. In the case of the relative pressure measuring system, the exposed reference air orifice is not covered or sealed by the sealing element.

[0011] The first joint may have an active brazing alloy. The end face of the base body facing away from the measuring membrane may be circular or elliptical. The base body may be cylindrical. The base body is connected to the measuring membrane, in particular in a pressure-tight manner. At least two electrodes may be arranged in the pressure chamber, forming a capacitive transducer.

[0012] In one embodiment, an electronic unit is arranged on the end face. The electronic unit is, in particular, electrically connected to the capacitive transducer and can, for example, be configured for data transmission and / or processing of an electrical signal received by the transducer.

[0013] In one embodiment, the base body is connected to the closure body at a circumferential edge.

[0014] In one embodiment, the base body is gas-tightly connected to the closure body.

[0015] In one embodiment, the locking element partially covers the front surface. In another embodiment, the locking element does not completely cover the front surface.

[0016] In one embodiment, the closure body is rectangular or hollow cylindrical. However, the closure body can also have any other shape, such as elliptical, circular, polygonal, etc.

[0017] In one embodiment, the closure body has an opening, wherein, if the system is designed for determining and / or monitoring a relative pressure, the closure body is arranged relative to the base body such that the opening overlaps with, and in particular aligns with, the reference air opening. In particular, if the system is designed for determining and / or monitoring an absolute pressure, the closure body is arranged relative to the base body such that the opening does not overlap with the reference air opening. The opening may be configured as a bore. In one embodiment, the closure body is configured as a hollow cylinder with a wall, and the opening is arranged in the wall. The opening is, in particular, aligned parallel to a longitudinal axis of the hollow cylinder.

[0018] In one embodiment, the closure body is designed as a hollow cylinder with a bulge, and the opening is arranged in the bulge. The bulge can be located in an interior space of the hollow cylinder. The bulge is, in particular, aligned parallel to a longitudinal axis of the hollow cylinder.

[0019] In one embodiment, the locking body has a recess. The recess can be arranged in the locking body such that an electronic unit located on the end face is positioned within the recess. The locking body can have either a recess or an opening. Alternatively, the electronic unit can be positioned within the opening.

[0020] In one embodiment, the closure element is designed as a pressure-resistant ring. The pressure-resistant ring can be arranged between the pressure measuring cell and the housing of a pressure sensor. The pressure-resistant ring can be designed to mechanically decouple the pressure measuring cell.

[0021] In one embodiment, the closure body is made of a ceramic, Kovar® or Invar®.

[0022] In one embodiment, the locking body and the base body each have at least one coupling element, wherein the coupling elements are configured to correspond with each other, such that two coupling elements engage with each other. For example, the locking body has at least one alignment element, wherein the base body has at least one receiving element corresponding to the alignment element, and wherein the at least one alignment element and the at least one receiving element are arranged and configured such that the at least one alignment element can be received into the at least one receiving element. Alternatively, it is also possible that the locking body has at least one receiving element and the base body has at least one alignment element.

[0023] In one embodiment, at least one alignment element is a nose, a raised section and / or a projection.

[0024] In one embodiment, the at least one receiving element is a groove, a recess, and / or a notch. In one embodiment, the first joining point and / or the second joining point are solder joints.

[0025] With regard to the pressure sensor, the problem is further solved by a pressure sensor for determining and / or monitoring the pressure of a medium, with a system according to one of the previous embodiments, a housing in which the pressure measuring cell is installed.

[0026] The sealing element can be designed as a spacer between the pressure sensor and the housing. In particular, the sealing element can be designed to decouple the pressure sensor from the housing.

[0027] In one embodiment, the sealing element is designed as a pressure-resistant ring and is arranged between the housing and the pressure measuring cell. In particular, a connecting element, such as a threaded ring, is arranged between the sealing element and the housing. The pressure-resistant ring serves to mechanically decouple the pressure measuring cell from the housing. The pressure-resistant ring can have an opening in its wall which, if the pressure measuring cell is designed as a relative pressure measuring cell, overlaps with, and in particular aligns with, the reference air opening. The system can be an absolute or relative pressure measuring system.

[0028] With regard to the method, the problem is further solved by a method for manufacturing a system consisting of a pressure measuring cell and a closure body, wherein the method comprises at least the following steps:

[0029] Providing multiple pressure measuring cells and multiple closure bodies, wherein the pressure measuring cell comprises a base body and a ceramic measuring diaphragm connected to the base body by means of a first joining point, wherein the measuring diaphragm can be subjected to the pressure p1 of the medium, wherein a pressure chamber is arranged between the measuring diaphragm and the base body, wherein the base body has a reference air opening connected to the pressure chamber; manufacturing a relative pressure measuring system: o Aligning the closure body and the pressure measuring cell to each other such that the reference air opening is unobstructed, o Joining the pressure measuring cell to the closure body, wherein the closure body is connected to an end face of the base body facing away from the measuring diaphragm by means of a second joining point;

[0030] Manufacturing an absolute pressure measuring system: o Aligning the closure body and pressure measuring cell to each other in such a way that the closure body closes the reference air opening, o Joining the pressure measuring cell to the closure body, whereby the closure body is connected to an end face of the base body facing away from the measuring diaphragm by means of a second joining point.

[0031] The embodiments of the system and the pressure sensor according to the invention apply mutatis mutandis to the method according to the invention and vice versa.

[0032] Depending on whether the system is intended for determining and / or monitoring absolute or relative pressure, the sealing element is aligned with the pressure sensor so that it either closes the reference air port or leaves the reference air port open. After alignment, the pressure sensor and sealing element are joined. This joining process may involve applying solder to a mating surface of the pressure sensor and / or the sealing element, followed by heating the system to a soldering temperature.

[0033] The alignment and joining process steps for an absolute pressure measuring system must be carried out in a vacuum, so that the pressure chamber is evacuated. The absolute pressure in the pressure chamber of the absolute pressure measuring system is zero, whereby the term "zero absolute pressure" as used in the application refers to a technically feasible vacuum with a pressure of less than 100 mbar and, in particular, less than 1 x 10⁻⁶ m / s, achieved with reasonable effort. 3 mbar is to be understood.

[0034] With regard to its use, the problem is further solved by using a kit for manufacturing absolute and relative pressure measuring systems, wherein the kit comprises a pressure measuring cell and a closure element, wherein the pressure measuring cell comprises a base body and a ceramic measuring diaphragm connected to the base body by means of a first joining point, wherein the measuring diaphragm can be subjected to the pressure p1 of the medium, wherein a pressure chamber is arranged between the measuring diaphragm and the base body, wherein the base body has a reference air opening connected to the pressure chamber, wherein, in the case of manufacturing a relative pressure measuring system, the closure element is arranged relative to the base body such that the reference air opening is unobstructed, and wherein the closure element is connected to an end face of the base body facing away from the measuring diaphragm by means of a second joining point.and wherein, in the case of the manufacture of an absolute pressure measuring system, the closure body is arranged relative to the base body such that the reference air opening is closed by the closure body and wherein the closure body is connected to an end face of the base body facing away from the measuring diaphragm by means of a second joining point.

[0035] The embodiments of the system, the methods and the pressure sensor according to the invention apply mutatis mutandis to the use according to the invention and vice versa.

[0036] The present invention will now be explained in more detail with reference to the following figures. They show:

[0037] Fig. 1 : a first embodiment of the pressure sensor according to the invention.

[0038] Fig. 2a-b: a first embodiment of the system according to the invention.

[0039] Fig. 3a-b: a second embodiment of the system according to the invention.

[0040] Fig. 4a-b: a third embodiment of the system according to the invention.

[0041] The system 1 according to the invention comprises a pressure measuring cell 2 and a sealing element 3. The pressure measuring cell 2 has a base body 4 and a measuring diaphragm 6, which are connected to each other by means of a first joining point 5 and enclose a pressure chamber 7. The measuring diaphragm 6 can be pressurized with the pressure of the medium 9. A reference air opening 8 is also arranged in the base body 4, through which ambient pressure can be supplied to the pressure chamber 7. The reference air opening 8 can be configured as a bore. For an absolute pressure measurement, the pressure chamber 7 is evacuated and the reference air opening 8 is closed. For a relative pressure measurement, the reference air opening is open and in contact with ambient air. The system 1 can be arranged in a housing 19 of a pressure sensor 18.

[0042] The pressure measuring cell 2 can include an electromechanical transducer for detecting pressure-dependent deformation of the measuring diaphragm 6. The transducer can be designed as a capacitive transducer with at least one capacitor, wherein the capacitor has a capacitance that varies depending on the pressure-induced deflection of the measuring diaphragm 6. The at least one capacitor 24 is formed by a measuring electrode mounted on the base body 4 facing the measuring diaphragm 6 and a counter electrode mounted on an end face of the base body 4 facing the measuring diaphragm 6. The at least one pressure-dependent capacitance of the capacitor 24 is detected by measuring electronics (not shown) which are 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 to make it available for further evaluation and / or processing.

[0043] The sealing element 3 is connected to an end face 10 of the base body 4 facing away from the measuring diaphragm 6, for example by means of a second joining point 11. Depending on whether the system is intended to enable absolute or relative pressure measurement, the sealing element 3 is arranged relative to the base body 4 such that the reference air opening 8 is either exposed or closed by the sealing element 3. The sealing element 3 can partially cover the end face 10 and / or be rectangular or hollow cylindrical. In particular, the sealing element 3 has an opening 12 that overlaps with the reference air opening 8 if the system is designed as a relative pressure measuring system. The sealing element 3 can also have a recess designed to accommodate electronics on the end face of the pressure measuring cell. The recess can also be the interior of a hollow cylinder.

[0044] Figures 2a-4b show various embodiments of the system 1 according to the invention in more detail.

[0045] Figures 2a-b show a first embodiment of the system 1 according to the invention. The closure body 3 is designed as a hollow cylinder with an interior 22, which has a bulge 14. Depending on the orientation of the closure body 3 relative to the pressure measuring cell 2, the reference air opening 8 overlaps with the interior 22 or is closed by the closure body 3 or the bulge 14. A joining surface 21 is also shown, to which the end face 10 and the closure body are joined. An electronic unit, optionally arranged on the end face 10, can be accommodated in the interior 22.

[0046] Figures 3a-b show a second embodiment of the system 1 according to the invention. The closure body 3 is designed as a hollow cylinder with an interior 22, which has an opening 12 in its wall 13. Depending on the orientation of the closure body 3 relative to the pressure measuring cell 2, the reference air opening 8 overlaps with the opening 12 or is closed by the closure body 3 or the wall 13. Figures 4a-b show a third embodiment of the system 1 according to the invention. The closure body 3 is designed as a rectangular plate with an opening 12. Optionally, the closure body 3 and the pressure measuring cell 2 each have at least one coupling element 15, which are designed such that two coupling elements 15 engage with each other, in particular such that a position of the closure body 3 relative to the pressure measuring cell 2 is fixed.For example, the closure body 3 can have an alignment element 16, such as a nose, and the base body 4 can have a receiving element 17, such as a recess. The alignment element 17 and the receiving element 17 are arranged and designed such that the at least one alignment element 16 can be received into the at least one receiving element 17.

[0047] As shown in Fig. 1, the closure body 3 can be designed as a pressure-resistant ring, which is arranged, in particular via a connecting element 25, between the housing 19 and the end face 10. The pressure-resistant ring

[0048] The closure body 3 can have a bulge 14 or an opening 12, as shown in Figs. 2-3.

[0049] Reference symbol list

[0050] 1 system

[0051] 2 pressure measuring cells

[0052] 3 locking bodies

[0053] 4 basic shapes

[0054] 5 first joint

[0055] 6 measuring membrane

[0056] 6a End range of the measuring membrane

[0057] 7 Pressure chamber

[0058] 8 Reference air opening

[0059] 9 Medium

[0060] 10 Front surface

[0061] 11 second joint

[0062] 12 Opening

[0063] 13 Wall

[0064] 14 Bulge

[0065] 15 coupling element

[0066] 16 alignment element

[0067] 17 Recording element

[0068] 18 pressure sensors

[0069] 19" enclosure

[0070] 21 joining surface

[0071] 22 Interior

[0072] 23 Sealing element

[0073] 24 electrodes

[0074] 25 Connecting element

Claims

Patent claims 1. System (1) comprising a pressure measuring cell (2) and a closure body (3), wherein the pressure measuring cell (2) has a base body (4) and a ceramic measuring membrane (6) connected to the base body (4) by means of a first joining point (5), wherein the measuring membrane (6) can be subjected to the pressure (p1) of the medium (9), wherein a pressure chamber (7) is arranged between the measuring membrane (6) and the base body (4), wherein the base body (4) has a reference air opening (8) connected to the pressure chamber (7), wherein the closure body (3) is connected to an end face (10) of the base body (4) facing away from the measuring membrane (6) by means of a second joining point (11), wherein the closure body (3) is arranged relative to the base body (4) such that the reference air opening (8) is free or that the reference air opening (8) is closed by the closure body (3).

2. System (1) according to claim 1, wherein the closure body (3) is rectangular or hollow cylindrical.

3. System (1) according to one of the preceding claims, wherein the closure body (3) has an opening (12), wherein, in the case that the system (1) is designed to determine and / or monitor a relative pressure, the closure body (3) is arranged relative to the base body (4) such that the opening (12) overlaps with the reference air opening (8).

4. System (1) according to claim 3, wherein the closure body (3) is designed as a hollow cylinder with a wall (13) and the opening (12) is arranged in the wall (13).

5. System (1) according to claim 3, wherein the closure body (3) is designed as a hollow cylinder with a bulge (14) and the opening (12) is arranged in the bulge (14).

6. System (1) according to one of the preceding claims, wherein the closure body (3) and the base body (4) each have at least one coupling element (15), wherein the coupling elements (15) are configured to correspond with each other, such that two coupling elements (15) engage with each other.

7. Pressure sensor (18) for determining and / or monitoring a pressure (p1) of a medium (9), comprising a system (1) according to one of the preceding claims, a housing (19) in which the pressure measuring cell (2) is inserted.

8. Pressure sensor (18) according to claim 7, wherein the closure body (3) is designed as a pressure-resistant ring and is arranged between the housing (19) and the pressure measuring cell (2).

9. Method for manufacturing a system consisting of a pressure measuring cell (2) and a closure body (3), wherein the method comprises at least the following steps: Providing several pressure measuring cells (2) and several closure bodies (3), wherein the pressure measuring cell (2) has a base body (4) and a ceramic measuring membrane (6) connected to the base body (4) by means of a first joining point (5), wherein the measuring membrane (6) can be subjected to the pressure (p1) of the medium (9), wherein a pressure chamber (7) is arranged between the measuring membrane (6) and the base body (4), wherein the base body (4) has a reference air opening (8) connected to the pressure chamber (7), Manufacture of a relative pressure measuring system: o Align the closure body (3) and the pressure measuring cell (2) to each other such that the reference air opening (8) is unobstructed, o Join the pressure measuring cell (2) to the closure body (3), wherein the closure body (3) is connected to an end face (10) of the base body (4) facing away from the measuring membrane (6) by means of a second joining point (11); Manufacture of an absolute pressure measuring system: o Align the closure body (3) and the pressure measuring cell (2) to each other such that the closure body (3) closes the reference air opening (8), o Join the pressure measuring cell (2) to the closure body (3), wherein the closure body (3) is connected to an end face (10) of the base body (4) facing away from the measuring diaphragm (6) by means of a second joining point (11).

10. Use of a kit for the manufacture of absolute and relative pressure measuring systems, wherein the kit comprises a pressure measuring cell (2) and a closure body (3), wherein the pressure measuring cell (2) comprises a base body (4) and a connection to the base body (4) by means of a first a ceramic measuring membrane (6) connected at a joint (5), wherein the measuring membrane (6) can be subjected to the pressure (p1) of the medium (9), wherein a pressure chamber (7) is arranged between the measuring membrane (6) and the base body (4), wherein the base body (4) has a reference air opening (8) connected to the pressure chamber (7), wherein, in the case of a relative pressure measuring system, the closure body (3) is arranged relative to the base body (4) such that the reference air opening (8) is unobstructed, and wherein the closure body (3) is connected to an end face (10) of the base body (4) facing away from the measuring membrane (6) by means of a second joint (11), and wherein, in the case of an absolute pressure measuring system, the closure body (3) is arranged relative to the base body (4) such thatthat the reference air opening (8) is closed by the closure body (3) and wherein the closure body (3) is connected to an end face (10) of the base body (4) facing away from the measuring membrane (6) by means of a second joining point (11).

Images