Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/403—Cells and electrode assemblies
  • G01N27/406—Cells and probes with solid electrolytes
  • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
  • G01N27/4071—Cells and probes with solid electrolytes for investigating or analysing gases using sensor elements of laminated structure

Definitions

• the present invention relates to a sensor element for determining different proportions of gas in a measurement gas, in particular in an exhaust gas of an internal combustion engine.
• Sensor elements for determining gas fractions in a measurement gas are known from the prior art in various configurations.
• lambda probes are known which measure the oxygen content in the exhaust gas in order to carry out a regulation of the combustion process based on the measurement result.
• Such sensor elements are arranged in the hot exhaust gas stream, wherein they are exposed to very high temperatures.
• Modern sensor elements are designed as electrochemical solid-state electrolyte sensors and have a heater to heat the sensor element to temperatures of about 750 ° C. In order to enable a further improved efficiency of the internal combustion engine and a reduction of exhaust gases, however, it is necessary to determine not only the oxygen content of the exhaust gas but also further gas components in the exhaust gas.
• the sensor element according to the invention with the features of claim 1 has the advantage that it can determine different gas fractions in a measuring gas, in particular in an exhaust gas of an internal combustion engine.
• the sensor element comprises on the one hand, a lambda probe for determining the oxygen content in the measurement gas and at least one semiconductor gas sensor for determining at least one further gas content in the measurement gas.
• the sensor element comprises a multiplexer, which is connected to the semiconductor gas sensor. The use of the multiplexer enables on-site signal conditioning and thus significantly reduces the susceptibility of the sensor element.
• the multiplexer allows the saving of signal lines, since it has only one output at a plurality of inputs preferably.
• the multiplexer thus reduces the number of sensor terminals of the sensor element. As a result, a particularly cost-effective production of the sensor element is possible.
• the semiconductor gas sensor is designed as a multi-gas sensor and has at least one gas-sensitive gate on a semiconductor component for each gas component to be determined in the measurement gas.
• a multiplicity of separate semiconductor gas sensors could also be provided, each of which can only determine one gas component in the measurement gas.
• such an arrangement requires a relatively large space, so that the formation of the semiconductor gas sensor is preferred as a multi-gas sensor for manufacturing reasons and because of their compactness.
• the multiplexer is integrated in the semiconductor gas sensor.
• a particularly compact design can be realized and, in particular, separate connection lines between the semiconductor gas sensor and the multiplexer are dispensed with.
• the multiplexer and the semiconductor gas sensor are each a separate component. This makes it possible for example for the multiplexer, the use of standard components.
• a predetermined for the operation of the multiplexer clock (clock) for switching the measurement signals at the inputs to the one or more outputs is preferably generated by a multiplexer arranged in the clock generating circuit.
• a clock to be preset for the multiplexer is generated by an external, clock-predetermining device.
• the external, clock-generating device is a clock-generating device for a heating device of the sensor element.
• This clock-generating device is, for example, a pulse width modulation of the heating device of the sensor element, which is heated by the heater periodically clocked.
• the semiconductor gas sensor is manufactured with high-temperature semiconductors, in particular SiC, GaN or GaAlN. This results in no material-related problems with the semiconductor gas sensor even at high exhaust gas temperatures above 300 ° C.
• a monoflop circuit is arranged between the external clocking device for the multiplexer and the multiplexer.
• a delay between the multiplexer switching and the clock pulses can be set. This is particularly advantageous when the external clock generator for the heating device of the sensor element is used for the multiplexer, in which the risk exists that the current or the voltage for the heater are coupled into the sensor signals.
• the sensor element according to the invention is particularly preferably used in vehicles for determining different proportions of gas in the exhaust gas of the vehicle.
• FIG. 1 shows a schematic sectional view of a sensor element according to a first exemplary embodiment of the invention
• Figure 2 is a schematic representation of a clock sequence of a pulse width modulation for a heating device of the sensor element and Figure 3 is a schematic sectional view of a sensor element according to a second embodiment of the invention.
• the sensor element 1 comprises a lambda probe 2 for determining the oxygen content in the exhaust gas of an internal combustion engine.
• the lambda probe 2 is constructed conventionally and shown only schematically in FIG.
• the lambda probe 2 comprises a sensor unit 3, which is arranged on a base material 4, in particular a solid electrolyte, such as zirconium oxide.
• the lambda probe 2 comprises a heating device 5.
• two terminals 2a, 2b, for the lambda probe 2 are also shown.
• the heating device 5 likewise comprises two connections 5a, 5b, the heating device 5 being heated by means of a pulse width modulation method or a fixed periodically clocked method.
• the heater 5 ensures that the lambda probe the necessary temperature of about 750 ° C during operation. This can be done for example by measuring the internal resistance of the terminals 2a and 2b.
• the sensor element 1 further comprises a semiconductor gas sensor 6, which is arranged on the lambda probe 2.
• the semiconductor gas sensor 6 includes a plurality of sensor units to determine various other gas contents in the exhaust gas.
• the sensor units are made of high-temperature semiconductors such. SiC, GaN or GaAlN.
• the semiconductor gas sensor 6 is likewise arranged in the exhaust gas stream. For each type of gas to be determined from the measurement gas, the semiconductor gas sensor 6 thus also has a semiconductor component, such as e.g. one
• Each of these sensor units on the semiconductor gas sensor 6 supplies at least one electrical signal, which is used for the determination of the gas concentration to be measured.
• the sensor element 1 furthermore comprises a multiplexer 7, which is likewise arranged on the lambda probe 2.
• the multiplexer 7 is an electrical circuit which switches the signals from a plurality of sensor units coming from the semiconductor gas sensor 6 sequentially into a predetermined clock to one or a few output channels.
• the multiplexer 7 has a single output 7a.
• the multiplexer 7 is connected to the semiconductor gas sensor 6 via a plurality of connection lines 9, more specifically to the individual sensor units of the semiconductor gas sensor.
• a supply line to the semiconductor gas sensor 6 is designated by the reference numeral 6a in FIG.
• the sensor element 1 has a very compact overall structure.
• the multiplexer 7 and the semiconductor gas sensor 6 are arranged on an outer side of the lambda probe 2.
• FIG. 2 schematically shows a possible embodiment of the clock signal in the form of a pulse width modulation.
• the clock signal has a fixed basic clock, wherein successive pulses do not overlap.
• This clock T for the heater 5 is thus also used as a clock for the multiplexer 7.
• an external clock for converting the parallel signals arriving at the multiplexer into serial signals for the output 7a of the multiplexer 7 is specified for the multiplexer 7.
• the output 7a of the multiplexer is connected to an evaluation circuit (not shown).
• the multiplexer 7 thus enables a reduction in the number of terminals of the sensor element. Since the multiplexer 7 as clock (clock) uses the clock of the heater 5, a particularly simple structure. If pulse width modulation is used as the clock for operating the heating device 5, care must be taken, however, that the maximum pulse width does not become as large as the basic clock, ie that two consecutive pulses are still separated in time. This can be achieved for example by inserting a break of a few microseconds to milliseconds.
• the multiplexer is operated in such a way that e.g. responded to the rising edge of the clock T for the heater. It should also be noted that in principle an unperiodic signal can also be used as clock generator for the multiplexer 7.
• the lambda probe 2 can be any type of lambda probe.
• the lambda probe can be for example a jump probe or a pure amperometric limit current probe without reference electrode or pump probe or an amperometric limit current probe with reference electrode or broadband probe.
• only two further connections 6a, 7a are thus provided by the additional function of the sensor element 1 according to the invention for the determination of still further gas types.
• the multiplexer 7 can alternatively also be designed such that it has more than just one output 7a.
• the sensor element 1 of the second exemplary embodiment comprises an integrated component 10, which comprises the semiconductor gas sensor 6 and the multiplexer 7.
• the multiplexer 7 is integrated in the semiconductor gas sensor 6, so that an integrated component 10 is provided.
• the plurality of connecting lines 9 between the semiconductor gas sensor 6 and the multiplexer 7 can be dispensed with.
• this embodiment corresponds to the previous embodiment, so that reference can be made to the description given there.

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• Chemical & Material Sciences (AREA)
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• Health & Medical Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
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• General Health & Medical Sciences (AREA)
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• Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)

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• 2005
  • 2005-12-13 DE DE102005059434A patent/DE102005059434A1/de not_active Ceased
• 2006
  • 2006-11-16 WO PCT/EP2006/068556 patent/WO2007068548A1/de active Application Filing
  • 2006-11-16 EP EP06819536A patent/EP1963841A1/de not_active Withdrawn
  • 2006-11-16 JP JP2008544920A patent/JP4878374B2/ja not_active Expired - Fee Related
  • 2006-11-16 US US12/086,326 patent/US8033160B2/en not_active Expired - Fee Related

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