RELATIVE-PRESSURE SENSOR COMPRISING A REFERENCE-PRESSURE SUPPLY

Abstract

The present disclosure relates to a relative-pressure sensor for determining a pressure of a medium in relation to an atmospheric pressure, the sensor comprising a housing; a measuring element arranged in the housing, wherein the pressure to be measured acts upon an outer surface of the measuring element, said surface being in contact with the medium; a reference-pressure supply, which supplies an inner surface of the measuring element with atmospheric pressure in the form of ambient air; an evaluation unit, which determines the pressure of the medium from a variable determined using the measuring element; and at least one drying chamber arranged in the housing for taking up atmospheric humidity from the ambient air supplied through the reference-pressure supply. Here, a bushing is provided, which can be pressed into the housing and has a capillary-type groove, which is helical at least in sections and runs around the bushing.

Claims

1-11. (canceled)

12. A relative-pressure sensor for determining a pressure of a medium in relation to an atmospheric pressure, comprising a housing; a measuring element arranged in the housing, wherein the pressure to be measured acts upon an outer surface of the measuring element, said surface being in contact with the medium; a reference-pressure supply, which supplies the atmospheric pressure in the form of ambient air to an inner surface of the measuring element; an evaluation unit, which determines the pressure of the medium from a variable determined using the measuring element; and at least one drying chamber arranged in the housing for taking up atmospheric humidity from the ambient air supplied through the reference-pressure supply, wherein an opening for the reference-pressure supply is provided in an outer wall of the housing, wherein a cylindrical bushing for the receiving and feeding-through of the connecting lines of the electronics and of the reference-pressure supply is provided, wherein the bushing is designed such that it can be pressed into the housing, wherein the bushing has, in an outer wall facing the inner wall of the housing, a capillary-type groove which is helical at least in sections and runs around the bushing, wherein the groove is arranged with respect to the housing such that the reference-pressure supply from the opening of the housing to the interior of the bushing takes place exclusively along the groove.

13. The relative-pressure sensor of claim 12, wherein the groove starts in an end section of the bushing and ends in an opposite end section of the bushing.

14. The relative-pressure sensor of claim 12, wherein the groove has a length and a cross-section, wherein the groove has such a volume that, when the entire air volume within the reference-pressure supply is compressed as a result of a temperature reduction, the groove is only partially filled with new ambient air from the environment of the relative-pressure sensor.

15. The relative-pressure sensor of claim 12, wherein the bushing is made of brass or bronze.

16. The relative-pressure sensor of claim 12, wherein the housing is made of stainless steel.

17. The relative-pressure sensor of claim 12, wherein the bushing is connected to the housing by press-fitting.

18. The relative-pressure sensor of claim 12, wherein a section with an enlargement of the outer diameter of the bushing is arranged on an end region, facing the measuring element, of the bushing, wherein the housing has a section with an enlargement of the inner diameter which corresponds to the section with the enlargement of the outer diameter of the bushing, wherein the corresponding sections of the enlargement of the outer diameter of the bushing and of the enlargement of the inner diameter of the housing engage in a gas-tight manner with one another after the introduction of the bushing into the housing.

19. The relative-pressure sensor of claim 12, wherein a bottom surface is arranged on the end region, facing the measuring element, of the bushing and closes the bushing perpendicularly to the longitudinal axis of the bushing, wherein the bottom surface has at least one opening for the feeding-through of the connecting lines of the electronics and of the reference-pressure supply.

20. The relative-pressure sensor of claim 19, wherein the bottom surface of the bushing is designed as a cast or a glass feedthrough.

21. The relative-pressure sensor of claim 20, wherein the reference-pressure supply is designed in sections as a humidity-permeable tube, wherein the tube is inserted into the at least one opening of the bottom surface in such a way that the reference-pressure supply from an interior of the bushing through the drying chamber to the measuring element takes place exclusively through the tube.

22. The relative-pressure sensor of claim 12, wherein the drying chamber has a drying module for receiving a humidity-adsorbing material or a molded body comprising a polymer matrix and zeolite.

Description

[0027] The invention is explained in greater detail with reference to the following drawings, FIGS. 1-2. The following are shown:

[0028] FIG. 1 an embodiment of the relative-pressure sensor according to the invention with the bushing, which is arranged in the housing, and

[0029] FIG. 2 an embodiment of the groove before and after the bushing is pressed into the housing.

[0030] The present invention is applicable to a variety of relative-pressure sensors which are based upon different measuring principles. Relative-pressure sensors are used for determining a pressure p1 of a medium in relation to an atmospheric pressure p2, the sensors comprising a housing; a measuring element arranged in the housing, wherein the pressure p1 to be measured acts upon an outer surface of the measuring element, said surface being in contact with the medium; a reference-pressure supply, which supplies an inner surface of the measuring element with atmospheric pressure p2 in the form of ambient air; an evaluation unit, which determines the pressure p1 of the medium from a variable determined using the measuring element; and at least one drying chamber arranged in the housing for taking up atmospheric humidity from the ambient air supplied through the reference-pressure supply. Corresponding relative-pressure sensors are manufactured and marketed by the applicant, e.g., under the names, “Cerabar” and “Ceraphant.”

[0031] The relative-pressure sensor 1 in FIG. 1 comprises a housing 3, a drying chamber 7, a reference-pressure supply 5, a measuring element 4, and an evaluation unit 6. Located in the outer wall of the housing 3 is an opening 8 for the reference-pressure supply 5, which allows the ambient air to enter the interior of the relative-pressure sensor 1. The opening 8 leads into the capillary-type groove 11, which is helical at least in sections, in the outer wall, which faces the housing 3, of the cylindrical bushing 9, which is pressed into the housing 3. Connecting lines of the electronics 10 also extend through the bushing 9. In FIG. 1, the groove 11 has a completely helical design. Other possibilities for the design of the groove 11 with respect to its shape and length are therefore not ruled out. In addition, the groove 11 begins in an end region of the bushing 9 and ends in the opposite end region of the bushing 9, so that the largest possible length of the groove 11 is achieved. The ambient air is guided exclusively through the opening 8 and along the groove 11 from the environment into the interior of the bushing 9.

[0032] The length and the cross-section of the groove 11 are important for slowing the entry of the humidity into the interior of the relative-pressure sensor 1, but also in the case of a large drop in temperature. In the case of a temperature reduction, the ambient air is compressed within the relative-pressure supply 5, and new ambient air is thus additionally taken up from the environment. The groove 11 is therefore designed in such a way that ambient air already present in the groove 11 is never completely aspirated into the interior of the relative-pressure sensor 1 in the case of any temperature drop within the operating range of the relative-pressure sensor 1.

[0033] In FIG. 1, the bushing 9 is made of brass or bronze, and the housing 3 is made of stainless steel in order to be able to particularly easily press the bushing 9 into the housing 3. Other embodiments of bushing 9 and housing 3 are therefore not ruled out. The bushing 9 made of brass or bronze is connected to the housing 3 by means of joining by thermal expansion.

[0034] The bushing 9 also has a section with an enlargement of the outer diameter 12a, which faces the measuring element 4. The housing 3 has a section 12b corresponding to this section of the bushing 12a and having an enlargement of the inner diameter. In FIG. 1, the corresponding sections 12a, b are each designed as a shoulder, wherein other embodiments are also possible. After pressing the bushing 9 into the housing 3, the two corresponding shoulders 12a, b join each other in a gas-tight manner.

[0035] In an end region in the direction of the measuring element 4, the bushing 9 is closed perpendicularly to its longitudinal axis with a bottom surface 13. In FIG. 1, the bottom surface 13 is designed as a glass feedthrough, but a cast or other form of a bottom surface 13 is also conceivable. Two openings 14 for the feeding-through of the connecting lines of the electronics 10 and of the reference-pressure supply 5 are provided in the bottom surface 13. A humidity-permeable tube 15 is inserted into an opening 14 of the bottom surface 13, wherein the reference-pressure supply 5 from an interior of the bushing 9 through the drying chamber 7 to the measuring element 4 takes place exclusively through the tube 15.

[0036] The drying chamber 7 has a molded body, which comprises a polymer matrix and zeolite, or a drying module for receiving a humidity-adsorbing material. The tube 15 leads through the drying chamber 7 to the measuring element 4. Through the humidity-permeable wall of the tube 15, the humidity diffuses from the reference-pressure supply 5 and is adsorbed by the drying chamber 7.

[0037] FIGS. 2a and 2b show a possible embodiment of the helical section of the groove 11. The groove 11 in FIG. 2a is designed as a thread. When the bushing 9 is pressed into the housing 3, the outer wall of the bushing 9 is deformed, which leads to a flattening of the outer wall of the thread (FIG. 2b). The flattened section of the outer wall now ensures hermetic tightness between the housing 3 and the bushing 9 in the region of the flattening. As a result, the ambient air can enter the interior of the bushing 9 only along the groove 11.

LIST OF REFERENCE SIGNS

[0038] 1 Relative-pressure sensor [0039] 2 Medium [0040] 3 Housing [0041] 4 Measuring element [0042] 5 Reference-pressure supply [0043] 6 Evaluation unit [0044] 7 Drying chamber [0045] 8 Opening in the housing [0046] 9 Bushing [0047] 10 Connecting lines of the electronics [0048] 11 Groove [0049] 12a Section of the bushing with an enlargement of the outer diameter [0050] 12b Section of the housing with an enlargement of the inner diameter [0051] 13 Bottom surface [0052] 14 Opening in the bottom surface [0053] 15 Tube