PRESSURE SEAL AND PRESSURE TRANSDUCER WITH SUCH A PRESSURE SEAL

Description

[0001] The present invention relates to a pressure transmitter and a pressure transducer with such a pressure transmitter. Generic pressure transmitters for transmitting pressure comprise a metallic pressure transmitter body, a separating membrane having a first side and a second side facing away from the first side, wherein the first side of the separating membrane can be subjected to a pressure to be transmitted; a separating membrane chamber closed by the separating membrane, wherein the second side of the separating membrane faces the separating membrane chamber in order to subject the separating membrane chamber to the pressure to be transmitted; a hydraulic channel communicating with the separating membrane chamber to transmit the pressure prevailing in the separating membrane chamber, wherein the hydraulic channel and the separating membrane chamber are filled with a transmission fluid, wherein the hydraulic channel extends at least partially through the pressure transmitter body.a filling channel in the diaphragm seal body, which communicates with the hydraulic channel; and a closure body, which closes the filling channel, wherein the closure body is inserted into the filling channel with a fit, in particular a transition fit or press fit, and is welded to the diaphragm seal body. Patent DE 197 44 208 C1 discloses such a diaphragm seal. Patent DE 10 2020 110 728 A1 also discloses a diaphragm seal. It has been shown that high temperatures, such as those that can occur during welding of the closure body, make it necessary for the long-term stability of the transmission fluid that it is not exposed to excessive temperatures during welding of the closure body. It is therefore the object of the present invention to provide a diaphragm seal and a pressure transducer with such a diaphragm seal.The manufacturing process reliably prevents excessive temperatures of the transmission fluid. This object is achieved according to the invention by the pressure transmitter according to independent claim 1 and the pressure transducer according to independent claim 14.

[0002] The invention further develops the generic pressure seal in that the pressure seal body comprises a first material with a first degree of hardness, and the closure body comprises a second material with a second degree of hardness that differs from the first degree of hardness by at least 10% of the lower of the two degrees of hardness. The first material and the second material can also comprise the same base material, with one of the materials having a different treatment state. For example, by Kolsterizing to achieve a higher hardness, or by annealing to achieve a lower hardness.

[0003] According to a further development of the invention, the hardness levels are specified in Brinell hardness (HB). The different hardness levels allow a defined deformation of one of the press-fit partners to be achieved, allowing the closure body to be inserted into the filling channel while displacing the transfer fluid to such an extent that overheating of the transfer fluid during the subsequent welding of the closure body is avoided.

[0004] In a further development of the invention, the second degree of hardness is greater than the first degree of hardness. This allows for an even more precise pressing of the closure body.

[0005] In a further development of the invention, the first material comprises an austenitic steel, in particular 1.4404, wherein the second material comprises a martensitic steel, in particular 1.4418.

[0006] In a further development of the invention, the second degree of hardness is 266-325 HB, and the first degree of hardness is 149-208 HB.

[0007] In a further development of the invention, the closure body is welded to the diaphragm seal body by means of spot welding, in particular pulse welding.

[0008] The selected welding processes allow the energy input to occur very quickly, which limits the heat flow to the transfer fluid sufficiently to prevent it from overheating.

[0009] In a further development of the invention, spot welding, in particular pulse welding, is carried out with a maximum power of not more than 2 kW, in particular not more than 1.5 kW.

[0010] In a further development of the invention, the maximum energy input during welding was not more than 2.5 kJ, in particular not more than 1.8 kJ.

[0011] In a further development of the invention, a welding depth of not less than 0.35 mm is achieved by means of spot welding or pulse welding.

[0012] In a further development of the invention, the closure body has a substantially cylindrical portion over which the press fit extends, wherein the length of the cylindrical portion is not more than 5 mm, in particular not more than 4 mm, and preferably not more than 3.5 mm. According to a further development of the invention, the length of the cylindrical portion is not less than 2 mm, in particular not less than 2.5 mm.

[0013] The length of the cylindrical section refers to the distance from the front end of the cylindrical section to the rear end of the cylindrical section. The rear end of the cylindrical section may be fused to the diaphragm seal body by welding. In this case, the thickness of the welded area in the axial direction of the cylindrical section at the circumference of the cylindrical section is added to the length of the cylindrical section.

[0014] In a further development of the invention, the closure body has a diameter of not more than 3.0 mm, in particular not more than 2.6 mm and preferably not more than 2.1 mm in the region of the press fit.

[0015] In a further development of the invention, the closure body has a surface area delimited by the press fit, which is wetted with the transfer fluid, wherein a maximum temperature in the surface area during welding of the closure body has remained below a decomposition temperature of the transfer fluid, so that the transfer fluid is free of thermal decomposition products.

[0016] The transfer fluid may include, for example, silicone oils, vegetable oils, glycols, propylene glycol and polyalphaolefins.

[0017] The specific temperature value, which depends on the transfer fluid used, is irrelevant in this case. As long as the transfer fluid is free of decomposition products, it can be concluded that the decomposition temperature has not been reached.

[0018] In a further development of the invention, the closure body has a surface area delimited by the press fit, which is wetted with the transfer fluid, wherein a maximum temperature in the surface area during welding of the closure body was not more than 200°C.

[0019] In a further development of the invention, the diaphragm seal body has a contour formed, in particular, by a recess that concentrically surrounds the joint of the closure body. This contour enables the centering of a tool relative to the closure body, wherein the tool comprises, in particular, a welding electrode.

[0020] A pressure transmitter according to the invention can be a stand-alone component for pressure transmission, or it can be integrated into a pressure transducer for measuring absolute pressure, relative pressure or differential pressure.

[0021] A pressure sensor according to the invention comprises at least one pressure transmitter according to one of the preceding claims; and a pressure transducer which can be subjected to a pressure to be measured via the hydraulic channel.

[0022] The invention will now be explained in more detail with reference to the exemplary embodiments illustrated in the drawings. It shows: Fig. 1a : a schematic representation of an embodiment of a pressure transmitter according to the invention; Fig. 1b : a schematic representation of an embodiment of a pressure measuring sensor according to the invention with a second embodiment of a pressure transmitter according to the invention; Fig. 1c : a schematic representation of a second embodiment of a pressure measuring sensor according to the invention with a third embodiment of a pressure transmitter according to the invention; Fig. 1d : a schematic representation of a third embodiment of a pressure measuring sensor according to the invention with a fourth embodiment of a pressure transmitter according to the invention; Fig. 2 : a schematic diagram of a closed filling channel of an embodiment of a pressure transmitter according to the invention;

[0023] The Fign. 1a, 1b, 1c und 1d The embodiments shown 1; 101; 201; 301 relate to pressure transmitters as standalone components or pressure measuring sensors with integrated pressure transmitters. For ease of understanding, corresponding elements in this series of drawings have reference numerals with the same two positions.

[0024] The embodiment of a pressure transmitter 1 according to Fig. 1a comprises a substantially partially cylindrical metallic diaphragm seal body 10 through which a bore extends in the axial direction, forming a section of a hydraulic channel 12. The diaphragm seal 1 further comprises a metallic separating membrane 17, shown only schematically here, which is attached to the end face of the diaphragm seal body 10 with a circumferential joint, whereby a separating membrane chamber 15 is formed between the diaphragm seal body 10 and the separating membrane 17, into which the hydraulic channel 12 opens. The separating membrane comprises, for example, a stainless steel with a material thickness of a few 10 µm to 200 µm and a diameter of a few cm. In addition, the separating membrane has an embossed contour (not shown here) in order to increase its volumetric stroke.The diaphragm seal 1 further comprises a capillary line 13, which is connected to the axial bore on the end face of the diaphragm seal body 10 facing away from the separating diaphragm 17, in order to form a further section of the hydraulic channel 12. For filling the diaphragm seal 1, in particular the hydraulic channel 12 and the separating diaphragm chamber 15, with a transmission fluid, the diaphragm seal body 10 has a filling channel 14 that extends from a lateral surface of the diaphragm seal body 10 to the hydraulic channel. For filling, the hydraulic channel and the separating diaphragm chamber can be evacuated via the filling channel in order to then allow a transmission fluid, for example a silicone oil, to flow in via the filling channel. The filling channel 14 is closed with a closure body 20, which, after filling, is press-fitted into the filling channel 24 and welded to the diaphragm seal body by means of pulse welding.

[0025] A first embodiment of a pressure sensor 101 according to the invention with integrated pressure transmitter according to Fig. 1b comprises a substantially cylindrical metallic diaphragm seal body 110, into which extends in the axial direction a bore to a sensor chamber 119, wherein the bore forms a hydraulic channel 112. The diaphragm seal further comprises a metallic separating membrane 117, shown only schematically here, which is attached to the end face of the diaphragm seal body 110 with a circumferential joint, whereby a separating membrane chamber 115 is formed between the diaphragm seal body 110 and the separating membrane 117, into which the hydraulic channel 112 opens. The separating membrane comprises, for example, a stainless steel with a material thickness of a few 10 µm to 200 µm and a diameter of a few cm. In addition, the separating membrane has an embossed contour (not shown here) in order to increase its volumetric stroke.The pressure transducer 101 further comprises a pressure transducer 140, here a piezoresistive semiconductor pressure transducer, which is inserted into the sensor chamber 119 from the end face of the diaphragm seal body 110 facing away from the separating diaphragm 117. To fill the diaphragm seal 101, in particular the hydraulic channel 12 of the sensor chamber 119 and the separating diaphragm chamber 15, with a transmission fluid, the diaphragm seal body 110 has a filling channel 114 that extends from a lateral surface of the diaphragm seal body 110 to the hydraulic channel 112. For filling, the hydraulic channel 112, the sensor chamber 119, and the separating diaphragm chamber 115 can be evacuated via the filling channel, in order to then allow a transmission fluid, for example, a silicone oil, to flow in via the filling channel.The filling channel 114 is closed with a closure body 120, which is press-fitted into the filling channel 124 after filling and is welded to the diaphragm seal body by means of pulse welding.

[0026] A second embodiment of a pressure sensor 201 according to the invention for measuring pressure differences according to Fig. 1c comprises two pressure seals in a substantially cylindrical metallic pressure seal body 210, into which a bore extends from each end face in the axial direction to a sensor chamber 219, wherein the bores each form a hydraulic channel 212a, 212b. The two pressure seals furthermore each have a metallic separating membrane 217a, 217b, shown only schematically here, which is each attached to the pressure seal body 210 at its end face with a circumferential joint, whereby a separating membrane chamber 215a, 215b is formed between the pressure seal body 210 and the separating membranes 217a, 217b, into which one of the hydraulic channels 212a, 212b opens. The separating membranes 217a, 217b each have, for example, a stainless steel with a material thickness of a few 10 µm to 200 µm and a diameter of a few cm.In addition, the separating diaphragms have a stamped contour (not shown here) to increase their volumetric displacement. The pressure transducer 201 further comprises a pressure transducer 240, in this case a piezoresistive semiconductor pressure transducer, which is inserted into the sensor chamber 219 and is supplied with the pressure prevailing in the separating diaphragm chamber 215a, 215b located on that side via the hydraulic channels 212a, 212b from opposite sides. For this purpose, the pressure transducer 240 divides the sensor chamber 219 into two parts, each of which communicates with one of the hydraulic channels. For filling the pressure seals, in particular the hydraulic channels 212a, 212b, the sensor chamber 219 and the separating membrane chambers 215a, 215b with a transmission fluid, the pressure seal body 210 has two filling channels 214a, 214b, each of which extends from a lateral surface of the pressure seal body 210 to one of the hydraulic channels 212a, 212b.For filling, the hydraulic channels 212a, 212b, the sensor chamber 219, and the separating membrane chambers 215a, 215b can be evacuated via the filling channels 214a, 214b, in order to then allow a transfer fluid, such as silicone oil, to flow in via the filling channels. The filling channels 214a, 214b are each closed with a closure body 220a, 220b, which, after filling, is press-fitted into one of the filling channels 214a, 214b and welded to the diaphragm seal body by pulse welding.

[0027] A third embodiment of a pressure sensor 301 according to the invention with integrated pressure transmitter according to Fig. 1d comprises a substantially cylindrical metallic diaphragm seal body 310, into which extends in the axial direction a bore 316a to a sensor chamber 319 in the diaphragm seal body 310, wherein the bore forms a portion of a hydraulic channel 312. The pressure transducer 301 further comprises a substantially cylindrical metallic separating diaphragm chamber body 311, through which extends an axial bore 316b, which is hydraulically connected to the bore 316a in the axial direction through the diaphragm seal body 310 via a capillary line 313 to form a hydraulic channel 312.

[0028] The pressure sensor 301 further comprises a metallic separating diaphragm 317, shown only schematically here, which is attached to the separating diaphragm chamber body 311 at its end face with a circumferential joint, whereby a separating diaphragm chamber 315 is formed between the separating diaphragm chamber body 311 and the separating diaphragm 317, into which the hydraulic channel 312 opens. The separating diaphragm comprises, for example, a stainless steel material with a material thickness of a few 30 µm to 200 µm and a diameter of a few cm. In addition, the separating diaphragm has an embossed contour (not shown here) to increase its volumetric displacement. The pressure sensor 301 further comprises a pressure transducer 340, here a piezoresistive semiconductor pressure transducer, which is inserted into the sensor chamber 319 from the end face of the diaphragm seal body 310 facing away from the capillary line 313.To fill the diaphragm seal 301, in particular the hydraulic channel 312 of the sensor chamber 319 and the separating diaphragm chamber 35, with a transmission fluid, the diaphragm seal body 310 has a filling channel 314 that extends from a lateral surface of the diaphragm seal body 310 to the hydraulic channel 312. For filling, the hydraulic channel 312, the sensor chamber 319, and the separating diaphragm chamber 315 can be evacuated via the filling channel, in order to then allow a transmission fluid, for example, a silicone oil, to flow in via the filling channel. The filling channel 314 is closed with a closure body 320, which, after filling, is press-fitted into the filling channel 324 and welded to the diaphragm seal body by pulse welding.

[0029] In all embodiments, the pressure transmitter bodies 10; 110; 210; 310 have a contour 18; 118; 210a, 218b; 318 around the closure bodies 20; 120; 210a, 220b; 320, which is formed in particular by a recess and serves for positioning a tool, in particular for positioning a welding electrode when closing the filling channel.

[0030] Details on closing the filling channel are now shown in the Fign. 2a und 2b explained, the reference numerals used correspond to the embodiment according to Fig. 1a correspond. However, the following explanations apply to all embodiments of the invention. The filling channel 14 extends from a surface of the diaphragm seal body 10 into its interior, wherein the diaphragm seal body 10 has a contour 18 in the vicinity of the filling channel, which contour is formed by the edge of a depression in the surface of the diaphragm seal body and which surrounds the opening of the filling channel 18, in particular coaxially. The filling channel has a diameter DF, which can be a few mm, for example not more than 2.5 mm. After the diaphragm seal has been filled with transmission fluid, a partially cylindrical, metallic closure body 10 is introduced into the filling channel 14, which has a length LK of not more than 10 mm, for example approximately 6 mm.The closure body 20, with a total length LK, has a cylindrical guide section 22 whose diameter is not greater than the diameter DF of the filling channel 14, and in particular is equal to the diameter DF of the filling channel 14, so that the guide section can be easily inserted into the filling channel, in particular with a clearance fit. The closure body further has a rear-side press section 24 whose diameter DP is greater than the diameter DF of the filling channel. With a diameter DF of the filling channel of 2.00 mm, the diameter DP of the press section 24 can be, for example, 2.05 mm. In this respect, the press section 24 can only be inserted into the filling channel 24 with a press fit.In this case, any transfer fluid that remains on the wall of the filling channel 24 after filling is reliably displaced in the area of ​​the press fit. However, it cannot be ruled out that transfer fluid may still be present on the walls of the filling channel or the outer surface of the closure body 20 in the area of ​​the guide section 22. In order to protect the transfer fluid, its decomposition temperature must not be reached there when the closure body is welded. To this end, the length LP of the press section 24 can be kept as large as possible, although there are limits to this parameter: firstly, the energy required to press the closure body increases with the length of the press fit, and secondly, the length of the filling channel and the total material required for the diaphragm seal therefore increases. Secondly, the energy input during welding can be optimized. Both approaches are utilized here.

[0031] By using steels with different hardnesses for the diaphragm seal body 10 and the closure body 20, the closure body is pressed together with a defined deformation of the less hard component. This allows a sufficient press fit length LP to be achieved in a reproducible manner. In this case, the closure body 20 comprises a martensitic steel, in particular 1.4418, which is harder than an austenitic steel, in particular 1.4404, used for the diaphragm seal body 10.

[0032] Furthermore, the welding of the closure body 20 to the diaphragm seal body 10 is carried out by spot welding, in particular pulse welding with a single, short energy input, which causes the joining partners to melt to the required welding depth Ts of, for example, 0.35 mm for a pressure-retaining closure, before too much energy has dissipated through heat conduction. The power during welding in the welding section is, for example, approximately 600 W with a power input of approximately 2.5 s.

[0033] To ensure good reproducibility in the manufacturing process, precise centering and spacing of a welding electrode with respect to the pressed-in closure body 14 is required. For this purpose, a Fig. 2a indicated ceramic, rotationally symmetrical centering device Z, which rests with its outer surface on the contour 18 and positions the welding electrode at a defined distance of approximately 1.5 mm. The result of the welding is shown in Fig. 2b shown, which has a Fig. 2aThe area marked B is shown schematically on an enlarged scale after the welding process. It can be seen that material of the closure body 20 and the diaphragm seal body 10 has fused together in an area 26 which borders on the rear end face of the closure body 26. As a result, the closure body 20 and the diaphragm seal body 10 are pressure-bearingly connected to one another with a welding depth Ts, wherein the welding depth designates the weakest connection between the joining partners, which is to be measured at the diameter DP of the press section 24. A subsequent measurement of the length LP of the press section 24, for example in a sectional view, proves to be difficult in that the rear area of ​​the press section 24 is fused to material of the diaphragm seal body 10, and the solidified material may have a meniscus.At the diameter DP of the pressing area, a final length L'P of the pressing area is measured, modified by the thickness M of the meniscus. However, based on the shape of the meniscus and the value of the final length L'P of the pressing section, the length LP of the pressing section 24 can be determined. This length defines the distance of the transfer fluid from the rear of the closure body 10 at the beginning of the welding process and thus, to a certain extent, a thermal safety distance for the transfer fluid. The length LP of the pressing section is at least 1.5 mm, no more than 5 mm, and for example, 3 mm. In combination with the described welding process, this reliably prevents thermal decomposition of the transfer fluid when closing the diaphragm seal.

Claims

1. A diaphragm seal (1) for hydraulically transferring a pressure, comprising: A metal diaphragm seal body (10); a separating membrane (17) with a first side and a second side, which faces away from the first side, wherein a pressure to be transferred can be applied to the first side of the separating membrane (17); a separating membrane chamber (15) which is sealed by the separating membrane (17), wherein the second side of the separating membrane (17) faces toward the separating membrane chamber (15) so that the pressure to be transferred is applied to the separating membrane chamber (15); a hydraulic duct (12) which communicates with the separating membrane chamber (15) in order to transfer the pressure present in the separating membrane chamber (15), wherein the hydraulic duct (12) and the separating membrane chamber (15) are filled with a transfer fluid, wherein at least sections of the hydraulic duct (12) run through the diaphragm seal body (10), a filling duct (14) in the diaphragm seal body (10) which communicates with the hydraulic duct (12); and a sealing body (20) which seals off the filling duct (14), wherein the sealing body (20) is inserted into a fit, in particular a transition fit or press fit, in the filling duct (14) and is welded to the diaphragm seal body (10); characterized in that the diaphragm seal body (10) has a first material with a first degree of hardness, and the sealing body (20) has a second material with a second degree of hardness, which differs from the first degree of hardness by at least 10% of the lower of the two degrees of hardness.

2. The diaphragm seal (1) as claimed in claim 1, wherein the second degree of hardness is greater than the first degree of hardness.

3. The diaphragm seal (1) as claimed in claim 1 or 2, wherein the first material comprises an austenitic steel, in particular 1.4404, and wherein the second material comprises a martensitic steel, in particular 1.4418.

4. The diaphragm seal (1) as claimed in claim 1, 2 or 3, wherein the second degree of hardness is equal to 266-325 HB and the first degree of hardness is equal to 149-208 HB.

5. The diaphragm seal (1) as claimed in one of the preceding claims, wherein the sealing body (20) is welded to the diaphragm seal body (10) by means of spot-welding, in particular pulsed-current welding.

6. The diaphragm seal (1) as claimed in claim 5, wherein spot-welding, in particular pulsed-current welding, is performed with a maximum power not exceeding 2 kW, in particular not exceeding 1.5 kW.

7. The diaphragm seal (1) as claimed in claim 5 or 6, wherein the energy input during welding is not more than 2.5 kJ, in particular not more than 1.8 kJ.

8. The diaphragm seal (1) as claimed in one of claims 5 to 7, wherein a welding depth of not less than 0.35 mm is achieved by means of spot-welding, in particular by means of pulsed-current welding.

9. The diaphragm seal (1) as claimed in one of the preceding claims, wherein the sealing body (20) has a mostly cylindrical section over which the press fit extends, wherein the length of the cylindrical section is not more than 5 mm, in particular not more than 4 mm, and preferably not more than 3.5 mm.

10. The diaphragm seal (1) as claimed in one of the preceding claims, wherein the sealing body (20) has a diameter of not more than 3.0 mm, in particular not more than 2.6 mm, and preferably not more than 2.1 mm, in the area of the press fit.

11. The diaphragm seal (1) as claimed in one of the preceding claims, wherein the sealing body (20) has a surface area limited by the press fit, which is wetted with the transfer fluid, wherein a maximum temperature in the surface area remained below a decomposition temperature of the transfer fluid when welding the sealing body (20) so that the transfer fluid is free from thermal decomposition products.

12. The diaphragm seal (1) as claimed in one of the preceding claims, wherein the sealing body (20) has a surface area limited by the press fit, which is wetted with the transfer fluid, wherein a maximum temperature in the surface area does not exceed 200 °C when welding the sealing body (20).

13. The diaphragm seal (1) as claimed in one of the preceding claims, wherein the diaphragm seal body (10) has a contour (18), in particular a recess, which concentrically surrounds the joint of the sealing body (20).

14. A pressure transducer, comprising at least one diaphragm seal (1) as claimed in one of the preceding claims; and a pressure measuring transducer (40) which can have a pressure to be measured applied to it via the hydraulic duct (12).