DE102015001228A1 - Antenna module with two combined antennas for a method for state detection of exhaust aftertreatment components using microwaves - Google Patents

Abstract

The invention relates to a device for coupling and decoupling microwaves in an exhaust gas catalytic converter or filter, characterized in that it is designed as a single antenna module containing two individual antennas. The use of the invention improves the microwave-based catalyst state recognition.

Description

Technical area

The invention relates to a device for detecting the state of an exhaust gas catalytic converter or an exhaust gas filter by means of microwaves.

Technical background

Stoichiometrically or super-powered internal combustion engines currently use only indirect methods for condition detection of gas, liquid or solids laden exhaust aftertreatment components in mass production.

Oxygen-storing three-way catalysts (eg, with stabilized ceria as the oxygen storage component) are usually monitored and controlled by gas sensors located upstream and downstream of the catalyst and measuring the combustion air ratio λ [1]. To a rough approximation, the three-way catalyst requires a stoichiometric combustion air ratio (λ = 1) for optimal conversion of both the oxidizing and the reducing exhaust gas components. The degree of loading of the oxygen storage, which compensates for operational fluctuations in transient operation, can not be determined directly via gas sensors. Instead, sensor-based balancing of the oxygen takes place by means of a model. One of the many examples can be found in the Scriptures DE 10 2009 039929 ,

Nitrogen oxide-storing catalysts for engines operated with excess air store the nitrogen oxides (NO _x ), which are increasingly produced in the presence of excess air (lean, superstoichiometric) in a storage material which is present as carbonate before being stored and after storage as nitrate. Once the reservoir is filled, a memory regeneration is necessary, which is due to a short-term operating state with lack of air (rich, stoichiometric) and is associated with increased fuel consumption. The storage degree of the catalyst can be determined model-based from a NO _x balance only indirectly with known mass flow and known NO _x concentration before catalyst, wherein NO _x sensors downstream only a NO _x signal will indicate when the catalyst is already filled and a NO _x breakthrough is present [2].

Ammonia SCR catalysts (SCR: selective catalytic reduction), i. A. For excess-pressure engines, use ammonia as the NO _x reduction agent. The required ammonia is z. B. provided from a entrained urea water solution and must be stored before the NO _x reduction in the SCR catalyst. The function of the catalyst is monitored indirectly downstream via NO _x sensors which, on the one hand, detect the increase in nitrogen oxides in the case of too little conversion and, on the other hand, in the event of an overdose of ammonia, also recognize this by their cross-sensitivity to the latter [3].

The degree of loading of particulate filters, for example with soot or ash, is indirectly determined model-supported with the help of differential pressure sensors [2]. If this increases above a threshold value due to the increased loading of solids, then regeneration, which is associated with increased fuel consumption, must be initiated. Therefore, it is advantageous to keep the number of regeneration processes as low as possible. To achieve this, the soot or ash charge in the particulate filter must be known as well as possible.

By a purely indirect determination of the state of the catalytic converters or filters, the obvious disadvantage that no direct control is possible and so in order to ensure a sufficient turnover in transient processes, the catalysts must be oversized as a rule. Thus, it is possible to dimension the exhaust aftertreatment components better by means of a high-frequency-based state sensor system and to save expensive and rare material as well as installation space and costs. Likewise, differential pressure sensors for particulate filters are not able to distinguish between soot and, for example, ashes.

State of the art with respect to the microwave-based measurement technology in automobile exhaust

An alternative way to determine the loading (or the state) of such exhaust aftertreatment devices, provides the microwave-based measurement technology in automobile exhaust. Revelations that represent the state of the art for this, are found, for. B. in the DE 10358495 , of the DE 10 2008 012050 , of the DE 10 2010 034983 , of the DE 10 2011 018226 or the DE 10 2011 107784 , For diesel particulate filters one can see the extensive patent family of US 2013 0127478 A1 consult.

In the microwave-based method, the electrically conductive metallic cladding ("canning") of the catalysts or filters serves as the boundary of a waveguide or cavity resonator. By coupling electromagnetic waves by means of one or more coupling elements (often also referred to simply as antennas) z. B. resonance modes excited, in which the resonance frequency and / or the quality are evaluated. As a measuring effect serves a change in the dielectric properties of the Catalyst materials during storage or release of gaseous exhaust gas constituents, for example oxygen, nitrogen oxides or ammonia, or in filters the accumulation of lossy media, such as soot, whereby the formation of the resonances is affected.

According to the prior art, the system can be operated with only one antenna in a pure reflection mode or with two antennas in a reflection and / or transmission mode with a maximum of four simultaneously evaluable parameters, the antennas can be designed as a capacitive pin coupler or as inductive loop antennas , An exemplary schematic representation from the literature [4] with two capacitive antennas can be found in 1 , The exhaust gas catalytic converter or filter of length L _W is here introduced into a cavity additionally defined with wire meshes (length L _R ), wherein the wire meshes are not absolutely necessary. As microwave feed two coaxial antennas (capacitive pin couplers) are present here. If two antennas are used, these antennas may be arranged on different sides of the catalyst (as in FIG 1 ) or are also on the same page.

Disadvantages of the prior art

For condition detection of catalytic converters or filters with microwaves, it has been found that operation with two antennas, that is, the performance of four-parameter measurements, has advantages over single-antenna operation. In particular, the evaluation of the transmission parameters have great advantages due to a better signal-to-noise ratio and therefore provide a more stable signal. The disadvantage here is hitherto that usually an arrangement with two separate antennas must be made, that is, there are several attachments in the exhaust aftertreatment system necessary.

Basic idea of the invention

The invention relates to a single antenna module which is inserted into the metallic hollow body around the exhaust gas catalytic converter or filter and couples microwaves as a coupling element, but represents two antennas in one and thus enables a four-parameter measurement characterized by the advantageous evaluation of the transmission , In an advantageous embodiment, the outer conductor of the first antenna at the same time assumes the function of the inner conductor of the second antenna.

Advantages of the invention

The invention offers the advantage that, when only one coupling element is used, condition measurements can be carried out on exhaust-gas aftertreatment components which were hitherto possible only with two coupling elements. This has the clear advantage that an improvement of the measurement signal takes place while keeping the overall system simple. In particular, only one supply line and only one installation position are needed.

Embodiments of the invention

An embodiment of the invention is characterized in that two antennas are combined to form a module, that the outer conductor of a coaxially arranged antenna acts as an inner conductor of the second antenna.

This is in 2 outlined. 2 represents the antenna module 1 in a capacitive antenna arrangement. The arrangement takes place from the inside to the outside: inner conductor 2 the first antenna, coaxially arranged outer conductor 3 the first and at the same time inner conductor of the second antenna and coaxially arranged outer conductor 4 the second antenna. The outer conductor of the second antenna ends at the surface 5 the exhaust pipe (which could be regarded as a waveguide or cavity resonator), the inner conductor of the second and the outer conductor of the first antenna protrudes into the exhaust pipe (ie into the cavity) 6 and the inner conductor of the first antenna projects further than its outer conductor into the cavity (the exhaust pipe). In 2 The inner pin and the middle cylinder form the first port 7 and the middle and outer cylinders the second port 8th ,

The following are the three leaders 2 . 3 and 4 referred to as inner, middle and outer conductor and no longer provided with a reference numeral.

Another possible execution, as in 3 described, is characterized in that the inner conductor is a loop antenna 9 forms the middle one 10 or outer conductor 11 can touch or not, z. B. position 12 or 13 , This is a mixture of a capacitive and an inductive antenna arrangement.

Another embodiment of the invention is in 4 shown. This is characterized in that two individual, mutually arranged antennas are installed as an antenna module. Both antennas can be used as capacitive pin couplers 14 , one antenna as pin coupler and one as inductive loop antenna 15 or both antennas as loop antennas 16 be executed.

To simplify the supply lines to two separate antennas and only one cable 17 These can also be used as in 5 represented, from an inner, middle and outer Head, for example, where the coaxial cable for port 1 from the inner and middle conductor and the coaxial cable for port 2 from the middle and outer conductor is shown. This form of feed can also be used if both antennas are arranged further apart from each other 18 ,

In 6 is shown how additional temperature sensor in the antenna module 1 can be installed. The function of the temperature sensor can be based for example on a resistive measuring principle or the thermoelectric effect. For the design with pin antennas, the temperature sensors can be integrated into the inner conductor 19 or show it completely 21 , Temperature sensors could z. B. thin jacket thermocouples. In addition, it is possible to integrate one or more further temperature sensors in the central conductor, which also protrudes into the cavity (into the exhaust pipe) 20 , In an embodiment of the inner conductor as a loop antenna, the temperature sensor via the inner conductor 22 , the middle ladder 23 or the outer conductor 24 to get integrated.

Quoted non-patent literature

• [1] J. Riegel, H. Neumann, H.-M. Wiedenmann, Exhaust gas sensors for automotive emission control, Solid State Ionics, 152-153 (2002) 783-800
• [2] UG Alkemade, B. Schumann, Engines and exhaust after treatment systems for future automotive applications, Solid State Ionics 177 (2006) 2291-2296
• [3] M. Shost, J. Noetzel, M. Wu, T. Sugiarto, T. Bordewyk, G. Fulks, GB Fisher, Monitoring, Feedback, and Control of Urea SCR Dosing Systems for NOx Reduction: Utilizing to Embedded Model and Ammonia Sensing, SAE Technical Paper 2008-01-1325 (2008)
• [4] R. Moos, M. Sporl, G. Hagen, A. Gollwitzer, M. Wedemann, G. Fischerauer, TWC: lambda control and OBD without lambda sample - an initial approach, SAE paper 2008-01-0916 (2008)

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

• DE 102009039929 [0003]
• DE 10358495 [0008]
• DE 102008012050 [0008]
• DE 102010034983 [0008]
• DE 102011018226 [0008]
• DE 102011107784 [0008]
• US 20130127478 A1 [0008]

Claims (10)

Device for coupling and decoupling microwaves into an exhaust gas catalytic converter or filter, characterized in that the device is designed as a single antenna module which contains two individual antennas. Apparatus according to claim 1, wherein the two antennas are designed so that the outer conductor of the internally arranged first antenna simultaneously acts as an inner conductor of the externally arranged second antenna. Apparatus according to claim 1, wherein the two antennas are arranged directly next to one another. Apparatus according to claim 1, characterized in that both or one of the antennas are designed as capacitive pin antennas. Apparatus according to claim 1, characterized in that both or one of the antennas are designed as inductive loop antennas. Device according to one of the preceding claims, characterized in that the antenna module, viewed from the inside to the outside, consists of the inner conductor, the coaxially arranged central conductor and the outer conductor arranged coaxially therearound. The device of claim 5, wherein the inner conductor protrudes further than the central conductor into the resonator and the outer conductor terminates at the wall of the metallic hollow body. Device according to one of the preceding claims, characterized in that the inner conductor terminates in one embodiment as a loop antenna on the middle or on the outer conductor or that he ends before or that he does not form a completely closed loop. The device of claim 3, wherein the feed line between the antennas and the meter is characterized by being formed by a single cable made up of outer, middle and inner conductors, the outer and middle conductors being a conduit and the central one and inner conductors form the other line. Device according to one of the preceding claims, characterized in that in at least one of the conductors in addition a temperature sensor is integrated.

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