ELECTROCHEMICAL GAS SENSOR

Description

[0001] The invention relates to an electrochemical gas sensor with a housing comprising a tank and a lid, with a stacked arrangement of at least one first electrode and a second electrode, each arranged on a support membrane, and a separator arranged between the electrodes, wherein a gas conduit path is formed between the first electrode and the second electrode and the gas conduit path is formed within the installation space defined by the electrodes.

[0002] Such gas sensors are known and are used, for example, to measure CO and H2.

[0003] Up to now, it has been common practice to pass the gas components through the support membrane on which catalysts for an electrochemical reaction are arranged.

[0004] These support membranes of the first and second electrodes, i.e., a measuring electrode and an auxiliary electrode, overlap on the outside of the circumference and form a gas conduction path on the outer circumference of the electrodes.

[0005] EP 3 719 487 A1 describes a gas detection device and a method for measuring humidity using an electrochemical gas sensor. The gas detection device comprises an electrolyte-based electrochemical gas sensor and a controller configured to measure the average humidity level in an environment over a specified period. The average ambient humidity level over time is determined based on the average rate of change of the electrolyte concentration in the electrolyte gas sensor of the gas detection device over time and the average ambient temperature over time. The gas detection device can be configured to transmit the average ambient humidity level to a second electrochemical gas sensor or a second gas detection device in the same environment.

[0006] WO 2005 / 015195 A1 describes an electrochemical gas sensor for detecting at least one gas species present in an atmosphere. The gas sensor comprises: a first gas sensor electrode configured to detect at least one first target gas species; a first gas path for directing the gas to the first gas sensor electrode; a second gas sensor electrode configured to detect at least one second target gas species, the first and second gas sensor electrodes being located on opposite sides of an electrolyte-containing area; a second gas path between the atmosphere and the second electrode, the gas path bypassing the first gas sensor electrode; and a counter electrode.

[0007] EP 3 674 701 A1 describes various embodiments of an electrochemical gas sensor. The electrochemical gas sensor can have a sensor cap with one or more fixed features arranged on a surface of the sensor cap. The electrochemical gas sensor can include a counter electrode configured to generate a gas during use. The electrochemical gas sensor can include a venting assembly designed to release at least a portion of the gas generated at the counter electrode from the electrochemical gas sensor. The venting assembly can comprise a vent line and a vent membrane that defines a passage for the gas flowing from an extended section of the counter electrode, through the vent membrane, to the vent line for release from the electrochemical gas sensor.

[0008] EP 2 871 472 A1 describes a sensor comprising a sensor housing or body, a table made of plastic arranged in the sensor housing, and a counter electrode attached to a first end of the table.

[0009] The invention is based on the objective of creating a more compact arrangement.

[0010] This problem is solved according to the invention by an electrochemical sensor having the features of claim 1.

[0011] Accordingly, the electrochemical sensor according to the invention is characterized in that at least one through-opening is arranged in the separator, through which the gas conduction path is formed, and that the first electrode is designed as a ring and is the sensor electrode.

[0012] In the current state of the art, the gas flow path typically runs around the circumference of the electrodes. This requires a lot of installation space, especially for small sensors, thus preventing further miniaturization.

[0013] The arrangement of the gas flow path within the electrode installation space according to the invention creates an internal gas flow path, so that no additional installation space is required at the circumference. This makes it possible to manufacture significantly smaller sensors than with a conventional gas flow path. According to the invention, this gas flow path is formed by arranging at least one through-opening in the separator. In this way, an internal gas flow path can be easily produced.

[0014] In one embodiment, at least one through-hole is additionally arranged in the carrier membrane of the first electrode. This allows the gas pipeline path to be defined more precisely.

[0015] The through-hole in the separator and / or the carrier membrane can thus be easily produced, for example by punching. The diffusion rate can be adapted to different applications or sensors by using different through-holes. In principle, several through-holes can also be present, defining a common gas flow path.

[0016] In one embodiment, an insert is placed into a through-opening in the separator and / or in the support membrane of the first electrode, for example, the one already mentioned. This ensures gas contact and / or gas flow between the first and second electrodes. The insert preferably has the same shape as the through-opening and fills its entire surface.

[0017] In one embodiment, the separator and / or the carrier membrane has at least two through-openings, each through-opening forming a separate gas path within the installation space defined by the electrodes. In this way, for example, two or more separate sensors can be arranged within a single housing, each sensor having its own gas path.

[0018] There are no further restrictions on the arrangement of the one or more through-holes, other than that they are located within an electrode. This ensures efficient gas conversion and allows for a compact design.

[0019] In one embodiment, the at least one through-hole is arranged centrally and / or coaxially, or substantially centrally and / or coaxially, to the electrodes. In particular, a single through-hole can be located at the geometric center of an electrode. Multiple through-holes are preferably arranged symmetrically to the geometric center.

[0020] In one embodiment, the stacked arrangement of the sensor is rotationally symmetrical. For this purpose, the support membrane and the electrodes can preferably be circular or ring-shaped, or in the form of a regular polygon.

[0021] In one version, the separator is designed as a glass fiber membrane and / or the support membrane consists of polytetrafluoroethylene, PTFE, and / or the electrodes consist of platinum.

[0022] According to the invention, the first electrode is the sensor electrode and is designed as a ring. The inner diameter of the ring is preferably adapted to the through-hole of the separator.

[0023] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings.

[0024] It shows: Fig. 1: a schematic cross-section of a sensor according to the invention in a first embodiment, Fig. 2: a schematic cross-section of a sensor according to the invention in a second embodiment, Fig. 3: a schematic cross-section of a sensor according to the invention in a third embodiment with two independent gas paths, Fig. 4: an exploded view of a sensor according to the invention, and Fig. 5: various shapes for passage openings.

[0025] The Fig. 1Figure 1 schematically shows an electrochemical gas sensor 1 according to the invention with a stacked arrangement of the electrodes according to a first embodiment. For clarity, the housing is not shown in the schematic representation. In the example shown, the gas sensor 1 has...

[0026] The following layers are arranged in order from top to bottom: a first support membrane 2, a first electrode 3 (sensor electrode), a first separator 4, a second support membrane 5, a second electrode (auxiliary electrode) 6, a second separator 7, a shielding membrane 8, a third separator 7, a third electrode (counter electrode), a fourth electrode 9' (reference electrode) 9, a third support membrane 10 and a fourth separator 7.

[0027] The support membranes 2, 5 and 10, for example, consist of polytetrafluoroethylene (PTFE). The separators 4 and 7, for example, consist of a glass fiber composite material.

[0028] In this example, the gas sensor has a rotationally symmetrical structure. The layers shown are therefore either circular or ring-shaped.

[0029] The four electrodes 3, 6, 9 and 9' are each arranged directly on the corresponding support membrane 2, 5 and 10. The third electrode 9 and the fourth electrode 9' are arranged on the same support membrane 10 and each only enclose approximately half a circular ring.

[0030] Electrodes 3, 6 and 9 with 9' have the same diameter among themselves, but this diameter is smaller than the diameter of the support membranes 2, 5 and 10. The diameter of the support membranes 2, 5 and 10, however, is smaller than the diameter of the separators 4 and 7 and the shielding membrane 8.

[0031] However, the decisive feature of the invention is that the first separator 4 has a larger diameter than the adjacent carrier membranes 2 and 5 and that the first separator 4 has a through-opening 11.

[0032] This through-hole 11 is arranged coaxially in the center of the first separator 4 in this example and is also circular in shape. The rotationally symmetrical design of the stack arrangement allows for simple assembly and a fault-tolerant design. This enables more precise calibration.

[0033] This arrangement of the first separator 4 according to the invention forms a central, middle gas conduit path 14. This means that gas diffusion from the first electrode 3 to the second electrode 6 takes place through this conduit opening 11 and not, as in the prior art, at the circumference of the sensor.

[0034] The gas line path 14 therefore does not require any installation space on the circumference of the sensor 1. This allows the overall diameter of the sensor to be reduced without compromising the minimum dimensions of the electrodes.

[0035] Alternatively, the through-hole 11 can also be located off-center. However, it is important that it is positioned within the installation space defined by the electrodes 3, 6. Therefore, it must not be located in the circumferential area 13 of the carrier membrane 2, 5 that extends beyond the electrodes 3, 6.

[0036] The through-hole 11 can also have a different shape, such as square or elliptical. The through-hole 11 enables a reliably reproducible adjustment of the gas diffusion to the second electrode, especially in miniaturized sensors.

[0037] In the example, an insert 12 is also inserted into the through-opening 11. This insert 12 is also made of PTFE and ensures gas contact and / or gas flow between the first electrode 3 and the second electrode 6 through the separator 4. The insert 12 has essentially the same shape as the

[0038] through-hole 11 and fills its surface area.

[0039] The third electrode 9 serves as a reference electrode. The fourth electrode 9' serves as a counter electrode. The second and third separators 7 and the shielding membrane 8 ensure that no gas diffuses from the second electrode 6 to the third electrode 9 and fourth electrode 9'. It is therefore important that no gas conduction path 14 is formed here.

[0040] The Fig. 2 Figure 1 shows an alternative embodiment of a gas sensor according to the invention. The structure, in particular the layer sequence, is identical to the Fig. 1 Identical parts are therefore marked with the same reference numbers and are not explained again. The only difference to the version of the Fig. 1 consists in the fact that the first carrier membrane 2 also has a passage opening 11, which is preferably identical to the passage opening 11 of the first separator 4.

[0041] The Fig. 3 shows a further embodiment of a gas sensor 1 according to the invention, the layer sequence of which is identical to the embodiments of the Figures 1 and 2Identical parts are therefore designated with the same reference numerals and are not explained again. This embodiment, however, has two independent gas paths 14. For this purpose, the first carrier membrane 2, the first electrode 3 (sensor electrode), and the first separator 4 each have two through-openings 11. In addition, two second electrodes (auxiliary electrodes) 6 and 6' are present, effectively forming two different sensors. The two second electrodes 6 and 6' can, for example, be semicircular or semi-ring-shaped. In this way, several different gases can be detected within a single housing.

[0042] The Fig. 4Figure 1 shows an exploded view of a gas sensor 1 according to the invention. In this example, the gas sensor 1 has a square tank 18. The sensor is a carbon monoxide sensor, and the tank contains 40% sulfuric acid. Tubular projections 19 extend from the bottom of the tank, through which electrical contacts for the four electrodes are routed. The electrical contacts have platinum wires 20 that are connected to the respective electrodes.

[0043] A table 17, which supports the layered structure of the sensor 1, is placed on the tubular projections 19. The table 17 has two rectangular openings 21 approximately in the center through which a staple-shaped wick 16 is guided. The two ends of the wick 16 are immersed in the sulfuric acid in the tank and convey the sulfuric acid to the third electrode 9 and fourth electrode 9'.

[0044] A separator 7 is initially arranged on table 17. The carrier membrane 10, with the third electrode 9 and the fourth electrode 9', rests on this separator. Electrodes 9 and 9' are followed by another separator 7. A shielding membrane 8 rests on this separator 7.

[0045] Above the shielding membrane 8, from bottom to top, are in this order: a separator 7, a second electrode (auxiliary electrode) 6, a separator 4 and a first electrode 2. The separator 4 and the first electrode 2 have a central through-hole 11, which is closed by an insert plate 12.

[0046] The sensor arrangement is closed by a cover 15, in which openings 22 for gas passage are arranged.

[0047] The Fig. 5Figure 3 shows exemplary embodiments for through-openings 11 in a first separator 4, which in this example is circular. The first separator 4 can also have a different shape, but this does not affect the shape of the through-openings. The through-openings shown can also be arranged in a first support membrane 2. Figure 3(a) shows a circular through-opening 11 arranged coaxially with the separator 4. Figure 3(b) shows a square through-opening 11 arranged centrally / coaxially with the separator 4. Figure 3(c) shows two approximately clamp-shaped through-openings 11 separated by a bridge.

[0048] Fig. 3(d) shows an elliptical through-opening 11 arranged centrally / coaxially to the separator 4. Fig. 3(e) shows a plus sign-shaped through-opening 11 arranged centrally / coaxially to the separator 4. Fig. 3(f) shows three circular through-openings 11 arranged symmetrically to the center of the separator 4. Fig. 3(g) shows a Pacman-shaped separator 4 with a triangular through-opening 11 arranged around the circumference of the separator 4. Fig. 3(h) shows a separator 4 with two circular segment-shaped through-openings 11 separated by a bridge, forming a prohibition sign-shaped separator 4. Fig. 3 (i) shows a separator 4 with two circular through-holes 11, which, however, have different diameters.

[0049] In all versions, the arrangement, size and / or number of the passage openings 11 can be varied to achieve a specific and defined gas diffusion rate.

[0050] In another version, the versions of the Fig. 5 (c), (f), (h) and (i) Each through-hole 11 defines a separate gas pipeline path 14, as for example in Fig. 3 shown. Reference symbol list

[0051] 1 Sensor 2 First support membrane 3 First electrode (sensor electrode) 4 First separator 5 Second support membrane 6, 6' Second electrode (auxiliary electrode) 7 Separator 8 Shielding membrane 9 Third electrode (counter electrode) 9' Fourth electrode (reference electrode) 10 Third support membrane 11 Through-hole 12 Insert 13 Circumferential area 14 Gas line path 15 Lid 16 Wick 17 Table 18 Tank 19 Tubular projection 20 Platinum wire 21 Opening in table 22 Opening in lid

Claims

1. Electrochemical gas sensor (1) having a housing comprising a tank (18) and a lid (15), having a stacked arrangement, arranged in the housing, of at least a first electrode (3) and a second electrode (6), which are each arranged on a supporting membrane (2, 5), and having a separator (4) arranged between the electrodes (3, 6), wherein a gas conduction path (14) is formed between the first electrode (3) and the second electrode (6), and the gas conduction path (14) is formed within the space defined by the electrodes (3, 6), characterized in that the separator (4) has a larger diameter than the respectively adjacent supporting membranes (2, 5), in that at least one feed-through opening (11) is arranged in the separator (4), through which the gas conduction path (14) is formed, and in that the first electrode (3) is in the form of a ring and is the sensor electrode.

2. Electrochemical gas sensor (1) according to claim 1, characterized in that at least one feed-through opening (11) is arranged in the supporting membrane (2) of the first electrode.

3. Electrochemical gas sensor (1) according to claim 1 or 2, characterized in that an insert part (12) is inserted into the or a feed-through opening (11) in the separator (4) and / or in the supporting membrane (4) of the first electrode (3).

4. Electrochemical gas sensor (1) according to one of claims 1 to 3, characterized in that the separator (4) and / or an insert part (12) has / have at least two feed-through openings (11) and a separate gas conduction path (13) is formed through each feed-through opening (11) within the space defined by the electrodes (3, 6).

5. Electrochemical gas sensor (1) according to one of claims 1 to 4, characterized in that the at least one feed-through opening (11) is arranged substantially centrally and / or coaxially with respect to the electrodes (3, 6).

6. Electrochemical gas sensor (1) according to one of the preceding claims, characterized in that the stacked arrangement is designed to be rotationally symmetrical.

7. Electrochemical gas sensor (1) according to one of the preceding claims, characterized in that the separator (4) is designed as a glass fiber membrane and / or in that the supporting membranes (2, 5) consist of polytetrafluoroethylene, PTFE, and / or in that the electrodes (3, 6) consist of platinum.