DE102009056881A1 - Device for acquisition of hydrogen concentration in exhaust gas in vent pipe of polymer electrolyte membrane fuel cell system in car, has sealing element arranged between heating element and adaptor and/or hydrogen sensor and element - Google Patents

Abstract

The device has a heating element connected with a hydrogen sensor (3) for indirectly heating a hydrogen containing gaseous mixture in a region of the hydrogen sensor, and an adapter (7) for connecting the heating element with a tube element (1) i.e. vent pipe. A planar sealing element (8) is arranged between the heating element and the adaptor and/or between the hydrogen sensor and the heating element, and a thermally insulated material surrounds the hydrogen sensor and/or the heating element in relation to environment.

Description

The invention relates to a device for detecting the hydrogen concentration in a hydrogen-containing gas mixture in a line element of a fuel cell system, according to the closer defined in the preamble of claim 1.

The US 2004/0182705 A1 shows a gas sensor for measuring gas concentrations. The structure of the gas sensor is shown in cross section in this document. It is extremely complex with several sealing rings, which ensure a proper sealing of the individual parts with each other. This extremely complex design of the sensor is unsuitable for safe and reliable installation, as errors can easily occur during assembly and individual elements can not be installed or installed incorrectly.

Hydrogen sensors, as they are known from the general state of the art, also show a rather complex structure and consist of the actual hydrogen sensor and a heating element, which is designed for example as an electric heater, as explained in the later WO 2008/116474 A1 is described. This structure of hydrogen sensor and heater, which is then attached via a counter flange to a conduit element, is also still relatively complex. Both the surface of the counter flange facing the heater and the two surfaces of the heater facing the counter flange on the one hand and the hydrogen sensor on the other must have a correspondingly high quality and, for example, are lapped in current designs. The same applies to the surface of the hydrogen sensor, which faces the heater. In the area of these sealing surfaces, circumferential grooves are typically introduced into which O-rings are inserted during assembly. These are greased to ensure a long service life and a corresponding tightness. This has the disadvantage that the grease attaches very easily dust, so that the assembly can only be done under very clean environmental conditions.

In particular, during assembly of the assembly of heating element and hydrogen sensor on the arranged on the line element mating flange, which often takes place, for example, in the final assembly of a equipped with the fuel cell system vehicle under normal production conditions, this is a serious drawback, as this registered dirt in the range of the hydrogen sensor which could affect its functionality. In addition, the structure with the O-ring to be lubricated and the highly dimensionally stable surfaces to be machined both during assembly and during manufacture is complicated and expensive.

Another disadvantage is that in the structure, which is for example screwed in the assembled state can not be determined whether an O-ring is inserted and whether this was greased and properly assembled, so that in case of failure, a complete disassembly of the construction is necessary.

From the WO 2008/116474 A1 Furthermore, a sensor for detecting a measured variable of a process gas is known. In order to prevent moisture from the gas mixture, in which a size is to be detected, settling in the region of a sensor and thus affecting the measured values of the sensor, the sensor is combined as a device for detecting a measured variable in the process gas with a heating element due to the elevated temperature, condensation of liquid in the region of the sensor can be prevented.

However, it has now been found that, especially when used in fuel cell systems, which are used in vehicles, this structure is not sufficient for the safe functioning of a hydrogen sensor. Rather, it comes through the condensation of water in the sensor inside again and again to incorrect measurements. These can lead to an emergency shutdown of the fuel cell system in extreme cases, since, for example, a much higher water concentration is detected as permissible in an exhaust gas stream from hydrogen-containing gas mixture. This is to be seen as a serious disadvantage in terms of reliability and user-friendly design of such a system.

It is therefore an object of the present invention to provide a device for detecting the hydrogen concentration in a hydrogen-containing gas mixture in a line element of a fuel cell system, which is simple and inexpensive to manufacture and enables easy, safe and reliable installation.

According to the invention, this object is achieved by a device for detecting the hydrogen concentration in a hydrogen-containing gas mixture with the features in the characterizing part of claim 1.

According to the invention, a planar sealing element is arranged between the heating element and the counter flange and / or between the hydrogen sensor and the heating element. Such a planar sealing element, which covers, for example, the entire surface of the two mutually mounted elements, has the crucial Advantage that it is able to compensate for any inaccuracies in the area of the surface of the mutually mounted elements, so that a much lower cost in terms of the processing of the surfaces in the manufacture of the elements is necessary. In addition, over such flat sealing elements a very simple assembly can be achieved, since they do not have to be inserted into a prefabricated groove, such as O-rings, but can be easily inserted flat between the elements to be sealed. Should the flat sealing element be slightly incorrectly positioned during assembly, then a sufficient sealing surface is still available, so that no functional disadvantage for the device arises as a result.

In a particularly favorable and advantageous development of the construction according to the invention, it is now provided that the hydrogen sensor is arbitrarily sealed with respect to the heating element, wherein the planar sealing element is arranged between the heating element and the counter flange. In this structure, the hydrogen sensor and the heating element, for example, continue to be sealed against each other as before via an O-ring. This is comparatively easy, since the assembly of these two elements typically takes place outside the actual production of the fuel cell system. In such a pre-assembly can be relatively clean and accurate work, so here the structure with an O-ring and two pressed against each other typically metallic surfaces is easier. In addition, the contact of the metallic surfaces next to the sealing O-ring ensures a direct heating of the hydrogen sensor by the heating element, so that a safe and reliable heating of both the hydrogen sensor and the heating element typically enclosed space is ensured for the gas mixture to be detected. The assembly of this preassembled unit of heating element and hydrogen sensor on the mating flange of the line element is then typically in the production, for example, equipped with the fuel cell system vehicle by this sensor or the structure of sensor and heating element on an exhaust duct, similar to an exhaust, in a vehicle must be mounted with internal combustion engine. Accuracy and cleanliness in the assembly are not as easy to follow as in the pre-assembly of the other two elements. Therefore, it is particularly important here to achieve over the flat sealing element according to the invention a simple and reliable installation of the two components against each other, which ensures a reliable and reliable seal with comparatively low demands on the surface quality of the surfaces to be joined.

In addition, the use of the planar sealing element in this area between the heating element and the mating flange has the additional advantage that it thermally insulated the heating element from the mating flange and thus from the line element which carries the gas mixture. The registered heating power thus benefits only the hydrogen sensor or the region with the gas mixture to be detected. It does not lead to a dissipation of heat through the mating flange and the line element itself. Thus, with comparatively low heating power, a reliable operation of the hydrogen sensor can be ensured in which by a suitable temperature level, the condensation of water vapor typically contained in the gas mixture can be avoided.

In a further very favorable and advantageous embodiment of this idea, it may further be provided that the hydrogen sensor and / or the heating element are surrounded with a thermally insulating material relative to the environment.

This also helps to keep the heat introduced by the heating element in the region of the heating element and the hydrogen sensor and thus to save heating power or to increase the safe functionality of the hydrogen sensor with the same heating power.

In a further very favorable and advantageous embodiment of the device according to the invention, it is additionally provided that the surfaces of the heating element, the counter-flange and / or the hydrogen sensor facing the sealing element have projecting sections. These projecting portions are configured such that they can be pressed into the planar sealing element, which in a particularly favorable and advantageous embodiment has a substantially planar surface configuration and is made of an elastic material. This ensures a secure and reliable fixing of the elements in the plane having the sealing surface to each other.

According to a very favorable and advantageous development of the device according to the invention, these projections are formed in the sections in one or more circulating passages around the opening to be sealed. The projecting portions thus have the shape of, for example, a closed ring, rectangle or the like. This ensures that in all areas around the sealed opening a closed projecting portion is present, which presses correspondingly in the sealing material during assembly. As a result, the tightness of the structure is further increased.

In a further very advantageous embodiment of the structure according to the invention, it is also provided that the flat sealing element in the assembled state extends laterally on at least one side to the boundary of the hydrogen sensor, the heating element and / or the counter flange. This construction with a planar sealing element, which covers substantially the entire surface to be sealed, makes it possible to easily tolerate slight deviations in the assembly, since a sufficient sealing surface is still available. In addition, it can be detected from the outside in the assembled state, whether a sealing element has been inserted or inserted reasonably appropriate. This makes it very easy and quick to achieve a quality assurance of the assembly, so that a higher reliability can be achieved in the assembled device.

Further advantageous embodiments of the device according to the invention will become apparent from the remaining dependent subclaims and will be apparent from the embodiment, which is described below with reference to the figures.

Showing:

1 a first possible construction of the device according to the invention in cross section in an assembled state;

2 a further possible construction of the device according to the invention in cross section in a disassembled state;

3 an exemplary sealing surface in a plan view; and

4 another possible structure of the device according to the invention.

In the presentation of the 1 is a conduit element 1 to recognize, in which a hydrogen-containing gas mixture flows. The pipe element 1 In this case, it may in particular be a line element in the region of a fuel cell system which is used in a vehicle. In such fuel cell systems as used in vehicles, PEM fuel cells are typically operated with air for the cathode side and hydrogen or a hydrogen-containing gas on the anode side. The hydrogen is circulated around the anode side and ideally completely consumed. The air passes to the fuel cell system directly or via other components, such as a turbine, in the area of the environment. The pipe element 1 can now be exemplified such an exhaust pipe 1 of such a fuel cell system in a vehicle. In this exhaust duct 1 under normal conditions, only exhaust air depleted of oxygen and product water contained in this exhaust air should flow out of the region of the fuel cell. Now it can come by appropriate leaks in the field of fuel cell or by discharged from the anode circuit of the fuel cell gas containing radicals of hydrogen, in the region of the exhaust air to an increased concentration of hydrogen. As soon as such a hydrogen concentration exceeds a critical value, action must be taken here, for safety reasons alone. This can typically be done by switching off the fuel cell system. To such a emergency shutdown of a fuel cell system, which is in particular for the operator of a vehicle, when the fuel cell system is used in a vehicle is rather uncomfortable and with respect to the restart comparatively expensive to really only have to perform, if this is absolutely necessary, are to Reliability of detecting the concentration levels of hydrogen in the hydrogen-containing gas stream in the conduit element 1 to set high requirements.

For detecting the hydrogen concentration is in the region of the line element 1 now a fluidic with the interior of the conduit element 1 connected device 2 arranged to detect the hydrogen concentration. The device 2 comprises, as is known from the prior art mentioned above, a hydrogen sensor 3 and a heating element 4 , The hydrogen sensor 3 typically will have an evaluation, which via here symbolically indicated electrical line elements 5 is connected to a controller of the fuel cell system in the vehicle. The heating element 4 is preferred in the embodiment shown here as an electric heater 4 be educated. This is also symbolically indicated here electrical line elements 6 connected to a corresponding power source, which allows its heating. As far as the device corresponds 2 essentially the device known from the aforementioned prior art.

The device 2 is on the conduit element 1 via a counterflange 7 attached, which fluidly connects to the interior of the conduit member 1 having. That in the conduit element 1 flowing gas mixture can thus through the mating flange 7 or an opening in the wall of the conduit element 1 and the counterflange 7 in the area of the electric heater 4 flow in and thus reaches the hydrogen sensor 3 in the area where the hydrogen sensor 3 detects the concentration of hydrogen in the gas mixture. In the construction, as in 1 is shown, it is now so that between the mating flange 7 and the heating element 4 a flat sealing element 8th can be seen. This flat sealing element is during assembly, for example by screwing the heater 4 on the counterflange 7 , where the screws are not shown here, so between the heater 4 and the counterflange 7 pressed that they are sealingly engaged with each other and the gas space formed in the openings, with the gas mixture to be detected for the hydrogen sensor 3 , is sealed from the environment.

The structure with a flat sealing element 8th is compared to the conventional structures with high precision manufactured, for example, lapped sealing surfaces and optionally arranged in the region of the sealing surface O-ring comparatively simple in terms of assembly and construction, since components with significantly lower manufacturing tolerances can be used. The flat sealing element 8th is between the mating flange 7 and the heater 4 compressed and can compensate for any bumps. In addition, a comparatively large area is available which ensures a tightness in the assembly of the two components against each other.

In the presentation of the 2 Now is a structure to recognize, in which the components are shown in the disassembled state to each other. On the representation of the pipe element 1 was omitted, so that the lowest in the presentation of 2 to be recognized component of the counter flange 7 is. Between the flange 7 and the electric heater 4 is again the flat sealing element 8th , For example, a plate of sponge rubber, a sealing material comparable to an O-ring or the like shown. In addition to the passage openings for the supply of the gas mixture to be detected to the hydrogen sensor 3 , which is also shown here in the disassembled state, the screw connections of the components are also indicated by two dot-dash lines. The design shows that the hydrogen sensor 3 over an O-ring 9 with the electric heater 4 connected is. This construction with the O-ring 9 which is typically used greased is in the assembly of the hydrogen sensor 3 on the electric heater 4 comparatively unproblematic, since these components are typically supplied as a preassembled unit. The pre-assembly of the generally greased O-ring 9 during assembly of the two components 3 . 4 is thus generally under very clean conditions, so here the risk that dust or the like adheres to the grease and is introduced into the structure is relatively low. This setup is then typically at a production of the fuel cell system, for example, when installing the fuel cell system in a vehicle in a vehicle production, on the exhaust duct 1 or the counterflange 7 on the exhaust pipe 1 attached. In this case, significantly more difficult installation conditions are prevalent, as in the pre-assembly of the hydrogen sensor 3 and the electric heater 4 , Therefore, here is about the flat sealing element 8th to achieve a clear advantage in terms of assembly.

In the presentation of the 2 It can also be seen that the surface facing the counterflange 10 the heater 4 as well as the electric heater 4 facing surface 11 of the counterflange 7 not completely flat, but projecting sections 12 exhibit. These protruding sections 12 are here on average exemplified in the form of two trains, which preferably circumferentially around the opening in both the counter flange 7 as well as in the electric heater 4 are arranged. These orbital features of the projecting sections 12 are in the plan view of an exemplary area, here the area 11 of the counterflange 7 to recognize. In the example shown here, two oval webs are arranged around the opening in the mating flange.

During assembly, the flat sealing element is now 8th , which is formed on its surfaces substantially planar, between the two surfaces 10 . 11 inserted. When the surfaces are braced against each other, the projecting portions press 12 in the material of the flat sealing element and thus ensure a secure positioning of the electric heater 4 opposite the counterflange 7 and a very good seal, as this increased surface pressure between the sealing element 8th and component 4 . 7 is formed circumferentially around the opening, and so further increase the tightness of the structure.

In the presentation of the 1 and 2 can also be seen that the flat sealing element 8th laterally to the boundary of the surfaces 11 respectively 10 of the counterflange 7 or the electric heater 7 zoom ranges. In the assembled state, the flat sealing element 8th therefore recognizable, so even from outside the construction of the device 2 To recognize whether this is safe and using the sealing element 8th on the counterflange 7 has been mounted. This offers corresponding advantages in terms of quality assurance, since it can be assumed in the event of a fault that this sealing point, if the flat sealing element 8th is visible from the side, correctly mounted.

In the presentation of the 4 is now also a structure to recognize, in addition to the structure described so far, which analogous to the representation in 1 To understand is a thermal insulation 13 shows. As mentioned above, the electric heater 4 provided to the gas mixture to be detected or the hydrogen sensor 3 at least indirectly so far to heat that no water vapor condenses out and the quality of the measured data of the hydrogen sensor 3 negatively influenced. By the flat sealing element 8th can now also be achieved that the electric heater 4 through the sealing element 8th , For example, when using a foam rubber or a correspondingly thick sheet-like sealing element 8th , comparatively good thermally against the mating flange 7 and thus with respect to the conduit element 1 is executed in isolation. About the electric heater 4 registered heat is therefore not through the line element 1 derived, so no unnecessarily high heating power to ensure the measurement quality of the sensor 3 necessary is. Through the use of thermal insulation 13 as exemplified in the presentation of 4 can be seen, and here by way of example both the electric heater 4 as well as the hydrogen sensor 3 sheathed, this effect can be further enhanced, since a heat dissipation to the environment can be minimized.

The thermally insulating material 13 provides thermal insulation, which at comparable heat output of the electric heater 4 a correspondingly higher temperature in the area of the hydrogen sensor 3 allowed. Even after switching off the electric heater 4 a much slower cooling of the hydrogen sensor takes place 3 as without the thermal insulation. The thermal insulation material 13 can, as it is in the presentation of the 4 can be seen, closely fitting around the area of the hydrogen sensor 3 and the electric heater 4 be educated. This allows the device 2 for example, when used on an exhaust pipe 1 a fuel cell system in a vehicle without further housing elements or the like to install. The thermally insulating material 13 then takes over in addition to the thermal insulation also protection against splashing water, dirt, stone chipping and the like. The structure of the thermally insulating material 13 In particular, it must ensure the thermally insulating properties and prevent the penetration of liquid or vaporous water. Therefore, it is preferable to select a suitable material, in particular for automotive use, which is insensitive to the ingress of water vapor and liquid and, for example, has a closed-pore surface. The material should also have a high temperature resistance and should preferably be heat resistant, so withstand temperatures above 120 ° C. In addition, it is preferable to select a nonflammable, vibration resistant, and at least for the life of a vehicle, age resistant material. Also, a resistance to chemicals and the like makes sense, since especially when used without further housing the spray water can be contaminated during winter operation with deicing salt and the like.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2004/0182705 A1 [0002]
• WO 2008/116474 A1 [0003, 0006]

Claims (10)

Device for detecting a hydrogen concentration in a hydrogen-containing gas mixture in a line element of a fuel cell system, in particular in a vehicle, with a hydrogen sensor and with a connected to the hydrogen sensor heating element which at least indirectly heated the gas mixture in the region of the hydrogen sensor, wherein the heating element via a counter flange with connected to the conduit element, characterized in that between the heating element ( 4 ) and the counterflange ( 7 ) and / or between the hydrogen sensor ( 3 ) and the heating element ( 4 ) a flat sealing element ( 8th ) is arranged. Apparatus according to claim 1, characterized in that only between the heating element ( 4 ) and the counterflange ( 7 ) the flat sealing element ( 8th ) is arranged. Device according to claim 1 or 2, characterized in that the hydrogen sensor ( 3 ) and / or the heating element ( 4 ) relative to the environment with the thermally insulating material ( 13 ) are surrounded. Device according to claim 1, 2 or 3, characterized in that the sealing element ( 8th ) facing surface of the hydrogen sensor ( 3 ) projecting sections ( 12 ) having. Device according to one of claims 1 to 4, characterized in that the sealing element ( 8th ) facing surface ( 10 ) of the heating element ( 4 ) projecting sections ( 12 ) having. Device according to one of claims 1 to 5, characterized in that the sealing element ( 8th ) facing surface ( 11 ) of the counterflange ( 7 ) projecting sections ( 12 ) having. Apparatus according to claim 4, 5 or 6, characterized in that the projecting portions ( 12 ) are formed in one or more circulating trains around the sealed opening. Device according to one of claims 1 to 7, characterized in that the sealing element ( 8th ) is formed substantially flat on its surfaces. Device according to one of claims 4 to 8, characterized in that the projecting portions ( 12 ) in the mounted state in the flat sealing element ( 8th ). Device according to one of claims 1 to 9, characterized in that the flat sealing element ( 8th ) in the assembled state laterally on at least one side to the boundary of the surfaces ( 10 . 11 ) of the hydrogen sensor ( 3 ), of the heating element ( 4 ) and / or the counterflange ( 7 ) enough.

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