Method for connecting a hydraulic channel in a pressure sensor, and pressure sensor comprising such a connection of a hydraulic channel

Abstract

The invention relates to a method for connecting a hydraulic channel (12) in a pressure sensor (1), wherein a first part of the hydraulic channel (12.1) is formed in a first component, and a second part of the hydraulic channel (12.2) is formed in a second component of the pressure sensor (5.1). The method has the following steps: - introducing a tube (14) into one of the two parts of the channel (12.1, 12.2), said tube (14) having a higher melt viscosity than the two components of the pressure sensor (2, 5.1) at least at a welding temperature required for welding the two components; - arranging the two components (2, 5.1) relative to each other such that the two joint surfaces (13.1, 13.2) adjoin each other and the tube (14) protrudes or is introduced into the other part of the channel (12.2); and - welding the two components (2, 5.1) such that a welding seam (15) extends through the channel (12) and the tube (14) without having to close the hydraulic channel (12).

Description

[0001] Method for connecting a hydraulic channel in a pressure sensor and pressure sensor comprising such a connection of a hydraulic channel

[0002] The invention relates to a method for, in particular, a pressure-tight and / or gas-tight connection of a hydraulic channel in a pressure sensor and to a pressure sensor.

[0003] Pressure sensors are used to measure pressure and / or to control, regulate, and / or automate a process occurring within a plant. Pressure sensors are used in automation technology in a wide variety of industries, such as the chemical and food industries, to name just a few important applications.

[0004] A pressure sensor typically comprises a pressure measuring cell and sensor electronics connected to the pressure measuring cell. The pressure measuring cell includes an electromechanical transducer that converts the response of a pressure-sensitive element into an electrical signal, which is recorded by the sensor electronics and accessible for further evaluation and / or processing.

[0005] The pressure sensor can be designed as an absolute pressure sensor, a relative pressure sensor, or a differential pressure sensor. While an absolute pressure sensor measures the pressure to be measured in absolute terms, i.e., as a pressure difference relative to the vacuum, a relative pressure sensor measures the pressure of a process medium relative to a reference pressure. The reference pressure is usually the atmospheric pressure prevailing at the installation location of the pressure sensor.

[0006] A differential pressure sensor, on the other hand, measures the difference between two measuring pressures of the process medium. Differential pressure sensors are used, for example, in tanks for level measurement or in pipelines for flow measurement.

[0007] While the measuring pressure of the process medium is applied via the separating diaphragm to the surface of the pressure-sensitive element facing the process, the surface of the pressure-sensitive element facing away from the process is subjected to vacuum, the atmospheric relative pressure or, in the case of a differential pressure sensor, another measuring pressure.

[0008] To transmit the measured pressure(s) of the process medium to the pressure-sensitive element, hydraulic channels filled with a pressure transmission fluid are implemented in the pressure sensor. The pressure transmission fluid typically comprises an oil, such as silicone oil. Due to manufacturing constraints, the hydraulic channels cannot be implemented in a single component of the pressure sensor; therefore, a hydraulic channel can consist of two parts, with each part of the channel implemented in a different component of the pressure sensor. The entire hydraulic channel is then created by joining the two components. Welding is typically used as the joining method.

[0009] The disadvantage of this is that joining the two components can lead to the hydraulic channel becoming blocked.

[0010] The invention is therefore based on the object of showing a possibility of how two components of a pressure sensor, in each of which a part of a hydraulic channel is realized, can be joined without the hydraulic channel being closed.

[0011] The object is achieved according to the invention by the method according to patent claim 1 and the pressure sensor according to patent claim 8.

[0012] The method according to the invention for the particularly pressure- and / or gas-tight connection of a hydraulic channel in a pressure sensor, wherein a first part of the hydraulic channel is formed in a preferably metallic first component of the pressure sensor and ends at a first joining surface of the first component and a second part of the hydraulic channel is formed in a preferably metallic second component of the pressure sensor and ends at a second joining surface of the second component, provides the following steps:

[0013] Inserting a tube into one of the two parts of the channel in such a way that the tube is partially inserted at the corresponding joining surface parallel to a joining axis in such a way that the tube both projects into the part of the channel and projects out of the corresponding joining surface, wherein the tube has a higher melt viscosity than at least one, preferably both, components of the pressure sensor at least at a welding temperature required for welding the two components, so that the tube at least reduces the ingress of melt into the hydraulic channel in the region of the tube during welding;

[0014] Positioning / arranging the two components relative to each other in such a way that the two joining surfaces are adjacent to each other and the tube protrudes or is inserted into the other part of the channel;

[0015] Welding the two components in such a way that the hydraulic channel and the tube are welded over in such a way that a weld seam extends through the channel and the tube without closing the hydraulic channel.

[0016] According to the invention, the insertion or introduction of a tube into two parts or subsections of a hydraulic channel at a joint where the two components, each of which contains a part or subsection of the hydraulic channel, are joined, is proposed in order to prevent the melt from entering the region of the channel during welding of the two components. Inserting the tube into the two parts of the channel also offers the advantage that the tube can be used to center the components relative to one another.

[0017] An advantageous embodiment of the method according to the invention provides that the positioning / arranging of the two components relative to one another is carried out in such a way that the two components are moved relative to one another along the joining axis until the joining surfaces adjoin one another and the tube protrudes or is inserted into the other part of the channel.

[0018] A further advantageous embodiment of the method according to the invention provides for welding to be carried out using a beam welding method, in particular a laser beam welding method in a vacuum or an electron beam welding method. In particular, the method can provide for welding of the two components to be carried out in such a way that a welding beam is guided within a range of approximately ± 45° to a normal vector of the outer surface.

[0019] A further advantageous embodiment of the method according to the invention provides that the first component and the second component have a substantially rotationally symmetrical outer contour at least in the region of the joining surfaces and the two components are welded radially circumferentially.

[0020] Yet another advantageous embodiment of the method according to the invention provides that the welding of the two components is carried out in such a way that the weld seam does not extend over the entire cross-sectional area. In particular, the method can also provide that the welding of the two components is carried out in such a way that the weld seam does not extend over the entire cross-sectional area, but only to a predetermined depth of approximately 1 / 2, preferably approximately 1 / 3, particularly preferably approximately 1 / 4 of a diameter of the entire cross-sectional area.

[0021] The invention further relates to pressure sensors for determining the pressure of a process medium, comprising a cup-shaped housing component in which a pressure measuring cell with a pressure-sensitive element is arranged, and a base body component to which at least one separating membrane is attached to form a pressure chamber, wherein at least one hydraulic channel filled with a transmission fluid is provided, via which the pressure chamber is connected to the pressure-sensitive element in order to transmit a medium pressure, wherein the hydraulic channel has a first part formed in the cup-shaped housing component and ends at a first joining surface of the cup-shaped housing component, and a second part formed in the base body component and ends at a second joining surface of the base body component, wherein the cup-shaped housing component and the base body component are arranged relative to one another in such a way thatthat the two joining surfaces adjoin one another, and a tube is arranged in the hydraulic channel such that it extends partially in the first part of the channel and partially in the second part of the channel, wherein the tube comprises a material which, at least at a welding temperature required for welding the two components, has a higher melt viscosity than at least one, preferably both, components of the pressure sensor, and wherein the cup-shaped housing component and the base body component are welded such that the hydraulic channel and the tube are welded over and a weld seam extends through the channel and the tube without closing the hydraulic channel.

[0022] An advantageous embodiment of the pressure sensor according to the invention provides that the cup-shaped housing component and the base body component have a substantially rotationally symmetrical outer contour at least in the region of the joining surfaces and the two components are welded radially circumferentially.

[0023] A further advantageous embodiment of the pressure sensor according to the invention provides that the weld seam does not extend over the entire cross-sectional area, but in particular only to a predetermined depth of approximately 1 / 3, preferably approximately 1 / 4 of a diameter of the entire cross-sectional area.

[0024] The invention is explained in more detail with reference to the following drawings. It shows:

[0025] Fig. 1 : a sectional view through a pressure sensor for determining the pressure of a process medium with a hydraulic pressure transmission channel, and

[0026] Fig. 2: a section of the hydraulic pressure transmission channel with the tube inserted according to the invention. Fig. 1 shows a sectional view through a pressure sensor for determining the pressure of a process medium. In the present embodiment, the pressure sensor 1 is designed as a differential pressure sensor for determining a differential pressure between a first and a second medium pressure p1, p2. Nevertheless, the invention is not limited to differential pressure sensors, but can also be applied to relative and / or absolute pressure sensors.

[0027] The pressure sensor 1 comprises a cup-shaped housing component 2, preferably made of metal, particularly preferably made of stainless steel, in which a pressure measuring cell with a pressure-sensitive element is arranged, and a base body component 5.1, 5.2 formed from two halves.

[0028] The pressure measuring cell 3 with the pressure-sensitive element 4 arranged in the direction of the process is positioned in the cup-shaped housing component 2. While the surface of the pressure-sensitive element 4 facing the base body component 5.1, 5.2 is subjected to a first media pressure of the process medium p1, a second pressure p2 is applied to the surface of the pressure-sensitive element 4 facing away from the base body component. In the case of a differential pressure sensor, a media pressure is also applied to the surface of the pressure-sensitive element 4 facing away from the base body component 5.1, 5.2. In the case of a relative or absolute pressure sensor, an atmospheric pressure from the environment of the pressure sensor or a vacuum is applied.

[0029] The deflection of the pressure-sensitive element 4, which is preferably a silicon chip, is detected via a measuring circuit 7. The cup-shaped housing component 2 can be a component that is essentially rotationally symmetrical with respect to its outer contour. In particular, the cup-shaped housing component 2 can be a so-called glass-metal feedthrough. This can have a metallic, in particular stainless steel, base body 2.4 and a plurality of metallic contact pins 2.1 glazed into the metallic base body 2.4 for electrically contacting the pressure measuring cell 3. The metallic base body can be in the shape of a cup or pot.

[0030] The base body component 5.1, 5.2 encloses an overload chamber 6, which is divided into two separate sub-chambers 6.1, 6.2 by a substantially disc-shaped overload diaphragm 8. The first half of the base body component 5.1 can be manufactured, for example, as a cast part, in particular as an investment casting. The second half of the base body component 5.2 can be manufactured, for example, from a steel, in particular a steel bar. Furthermore, the pressure sensor 1 comprises two separating membranes 9.1, 9.2 which can be acted upon from the outside with the respective pressure p1, p2, of which a first separating membrane 9.1 is fastened on the outside to the first half of the base body component 5.1 in such a way that a first pressure receiving chamber 10.1 is formed and of which a second separating membrane 9.2 is fastened on the outside to the second half of the base body component 5.2 in such a way that a second pressure receiving chamber 10.2 is formed.

[0031] In addition, the base body component comprises a first pressure transmitter which can be subjected to the first pressure p1 and via which the surface of the pressure-sensitive element facing the base body component 5.1, 5.2 can be subjected to the first pressure p1 via a first hydraulic pressure transmission channel 11, and a second pressure transmitter which can be subjected to the second pressure p2 and via which the surface of the pressure-sensitive element 4 facing away from the base body component can be subjected to the second pressure p2 via a second hydraulic pressure transmission channel 12.

[0032] Both pressure transmission channels 11, 12 are each filled with a pressure-transmitting fluid, e.g., a silicone oil, through which the pressure p1, p2 acting on the respective pressure transmitter is transmitted to the pressure-sensitive element 4. To fill the pressure transmission channels 11, 12, axial bores can be passed through the end face of the cup-shaped housing component 2, into each of which a filling tube 2.2 can be inserted, particularly welded.

[0033] To minimize the volume available to the pressure-transmitting fluid, a cylindrical filler body 17 may be provided in the cup-shaped housing component 2. The filler body 17 or oil displacement body may be made of a non-conductive material and may preferably be made of a temperature-resistant plastic that is chemically inert to the transmission fluid.

[0034] In terms of manufacturing technology, at least one of the two hydraulic pressure transmission channels 11, 12 is designed such that it comprises at least two parts or subsections 12.1, 12.2, wherein a first part 12.1 is formed in a first component of the pressure sensor 2 and a second part 12.2 is formed in a second component of the pressure sensor 5.1, 5.2. In the present exemplary embodiment, the first part 12.1 of the second hydraulic pressure transmission channel 12 is formed in the cup-shaped housing component 2 and the second part 12.2 of the second hydraulic pressure transmission channel 12 is formed in the first half of the

[0035] Main body component 5.1 is formed. The two parts 12.1, 12.2 are each formed in the corresponding component in such a way that they are located at a joining surface at which the two components are welded together during production. The first part 12.1 of the hydraulic channel 12 ends at a first joining surface 13.1 of the cup-shaped housing component 2. In particular, the first part 12.1 of the channel is arranged in the cup-shaped housing component 2 in such a way that it extends parallel to a joining axis 13, according to which the cup-shaped housing component 2 is to be joined to the first half of the main body component 5.1. Accordingly, the second part 12.2 of the hydraulic channel 12 ends at a second joining surface 13.2 of the first half of the main body component 5.1. In particular, the second part 12.2 of the channel is arranged in the first half of the main body component 5.1 such that it also extends parallel to the joining axis 13. The two parts 12.1, 12.2 can be produced, for example, by corresponding bores in the cup-shaped housing component 2 or the first half of the base body component 5.1.

[0036] According to the invention, a tube 14 is arranged in the hydraulic channel 12 in such a way that it extends into both parts 12.1, 12.2 of the second hydraulic pressure transmission channel 12. The tube 14 comprises a material which, at least at a welding temperature required for welding the two components, has a higher melt viscosity than at least one, preferably than both components, so that during the welding process, melt in the region of the join is prevented from falling into the hydraulic pressure transmission channel 12 and closing it off. The welding is carried out in such a way that the hydraulic pressure transmission channel 12 and the tube 14 are welded over, i.e. that a weld seam 15 extends through the pressure transmission channel (without closing it off) and the tube 14 in the direction of a central axis 16 of the pressure sensor 1.

[0037] Fig. 2 shows a section, marked with an "A" in Fig. 1, from the area of ​​the hydraulic pressure transmission channel with the inserted tube 14, which are welded over. The weld seam 15 preferably extends only from the outer surface of the pressure sensor 1 to a predetermined depth and not over an entire cross-sectional area in which the first and second joining surfaces 13.1, 13.2 lie. Particularly preferably, the weld seam 15 extends only to approximately 1 / 3, very particularly preferably only to approximately 1 / 4 of the diameter of the cross-sectional area of ​​the cup-shaped housing component 2 or half of the base body component 5.1 at the joint.

[0038] During the production of pressure sensors 1 according to the invention, the method for the particularly pressure-tight and / or gas-tight connection of a hydraulic channel is carried out in such a way that the tube 14 is first introduced into one of the two parts 12.1, 12.2 of the channel 12 of the corresponding component, e.g. the cup-shaped housing component 2. Subsequently, the two components 2, 5.1, in each of which a part 12.1, 12.2 of the pressure transmission channel 12 is formed, are aligned or positioned relative to one another in such a way that the two joining surfaces 13.1, 13.2, at which the respective part of the channel ends with an opening, adjoin one another and the tube 14 also projects into the other part of the pressure transmission channel 12. The alignment or positioning is preferably carried out in such a way that the two components 2, 5.1 are moved relative to each other along the joining axis 13 until the joining surfaces 13.1, 13.2 adjoin one another and the tube 14 projects into or is inserted into the other part of the channel. The two components 2, 5.1 are then welded at the first and second joining surfaces 13.1, 13.2. The welding is carried out in such a way that the hydraulic pressure transmission channel 12 and the tube itself are welded over, i.e. that a weld seam 15 extends radially inwards from an outer surface of the first or second component through the channel and the tube without closing the hydraulic channel. Fig. 2 shows an example of such a weld seam 15. For welding, for example, a beam welding process can be used. In particular, a laser beam welding process in a vacuum or an electron beam welding process can be used. The two components 2, 5.1 are preferably welded radially all the way around by means of a welding beam 16, which is preferably in a range of approx.± 45° to a normal vector of the outer surface.

[0039] List of reference symbols

[0040] Pressure sensor cup-shaped housing component

[0041] Contact pins

[0042] Filling tube

[0043] Metallic base body

[0044] Pressure measuring cell pressure-sensitive element

[0045] Halves of the base body component

[0046] Overload chamber

[0047] Subchambers

[0048] Measuring circuit

[0049] Overload diaphragm

[0050] Separation membrane

[0051] Pressure receiving chambers

[0052] First pressure transmission channel

[0053] Second pressure transmission channel

[0054] First part of the second pressure transmission channel

[0055] Second part of the second pressure transmission channel

[0056] Joining axis

[0057] First joining surface of the cup-shaped housing component

[0058] Second joining surface of the first half of the base body component

[0059] tube

[0060] Weld seam

[0061] welding beam

[0062] Packing or oil displacement body

Claims

Patent claims 1 . A method for the particularly pressure- and / or gas-tight connection of a hydraulic channel (12) in a pressure sensor (1), wherein a first part of the hydraulic channel (12.1) is formed in a preferably metallic first component of the pressure sensor (2) and ends at a first joining surface (13.1) of the first component (2) and a second part of the hydraulic channel (12.2) is formed in a preferably metallic second component of the pressure sensor (5.1) and ends at a second joining surface (13.2) of the second component (5.1), the method comprising the following steps: Inserting a tube (14) into one of the two parts of the channel (12.1 , 12.2) such that the tube (14) at the corresponding joining surface (13.1 , 13.2) is partially inserted parallel to a joining axis (13) in such a way that the tube (14) protrudes both into the part of the channel (12.1) and also protrudes from the corresponding joining surface (13.1), wherein the tube (14) has a higher melt viscosity than at least one, preferably both, components of the pressure sensor (2, 5.1), at least at a welding temperature required for welding the two components, so that the tube (14) at least reduces the ingress of melt into the hydraulic channel (12) in the region of the tube during welding; positioning / arranging the two components (2, 5.1) relative to one another in such a way that the two joining surfaces (13.1, 13.2) adjoin one another and the tube (14) protrudes or is inserted into the other part of the channel (12.2); Welding the two components (2, 5.1) in such a way that the hydraulic channel (12) and the tube (14) are welded over in such a way that a weld seam (15) extends through the channel (12) and the tube (14) without closing the hydraulic channel (12).

2. Method according to one or more of the preceding claims, wherein the positioning / arranging of the two components (2, 5.1) relative to one another is carried out in such a way that the two components (2, 5.1) are moved relative to one another along the joining axis (13) until the joining surfaces (13.1, 13.2) adjoin one another and the tube (14) projects into or is introduced into the other part of the channel (12.2).

3. Method according to one or more of the preceding claims, wherein the welding is carried out by means of a beam welding method, in particular a laser beam welding method in a vacuum or an electron beam welding method.

4. Method according to the preceding claim, wherein the welding of the two components is carried out in such a way that a welding beam in a range of approx. ± 45° to a normal vector of the outer surface.

5. Method according to one or more of the preceding claims, wherein the first component (2) and the second component (5.1) have a substantially rotationally symmetrical outer contour at least in the region of the joining surfaces (13.1, 13.2) and the two components (2, 5.1) are welded radially circumferentially.

6. Method according to one or more of the preceding claims, wherein the welding of the two components (2, 5.1) is carried out in such a way that the weld seam (15) does not extend over the entire cross-sectional area.

7. Method according to the preceding claim, wherein the welding of the two components (2, 5.1) is further carried out in such a way that the weld seam (15) does not extend over the entire cross-sectional area, but only to a predetermined depth of approximately 1 / 2, preferably approximately 1 / 3, particularly preferably approximately 1 / 4 of a diameter of the entire cross-sectional area.

8. Pressure sensor (1) for determining the pressure of a process medium, comprising a cup-shaped housing component (2) in which a pressure measuring cell (3) with a pressure-sensitive element (4) is arranged, and a base body component (5.1, 5.2) to which at least one separating membrane (9.1, 9.2) is fastened to form a pressure chamber (10.1, 10.2), wherein at least one hydraulic channel (11, 12) filled with a transmission fluid is provided, via which the pressure chamber (10.1, 10.2) is connected to the pressure-sensitive element (4) in order to transmit a medium pressure (p1, p2), wherein the hydraulic channel has a first part (12.1) which is formed in the cup-shaped housing component (2) and ends at a first joining surface (13.1) of the cup-shaped housing component (2), and a second part (12.2) which is formed in the Base body component (5.1, 5.2) is formed and on a second joining surface (13.2) of the base body component, wherein the cup-shaped housing component (2) and the base body component (5.1, 5.2) are arranged relative to one another in such a way that the two joining surfaces (13.1, 13.2) adjoin one another, and a tube (14) is arranged in the hydraulic channel (12) in such a way that it extends partly in the first part of the channel (12.1) and partly in the second part of the channel (12.2), wherein the tube (14) comprises a material which, at least at a welding temperature required for welding the two components (2, 5.1), has a higher melt viscosity than at least one, preferably than both components of the pressure sensor (1), and wherein the cup-shaped housing component (2) and the base body component (5.1, 5.2). are welded in such a way that the hydraulic channel (12) and the tube (14) are welded over and a weld seam (15) extends through the channel (12) and the tube (14) without closing the hydraulic channel.

9. Pressure sensor according to the preceding claim, wherein the cup-shaped The housing component (2) and the base body component (5.1, 5.2) have a substantially rotationally symmetrical outer contour, at least in the region of the joining surfaces (13.1, 13.2), and the two components are welded radially around their circumference.

10. Pressure sensor according to one of claims 8 or 9, wherein the weld seam (15) does not extend over the entire cross-sectional area, but in particular only to a predetermined depth of approximately 1 / 2, preferably approximately 1 / 3, particularly preferably approximately 1 / 4 of a diameter of the entire cross-sectional area.

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