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
  • G01N27/4067—Means for heating or controlling the temperature of the solid electrolyte
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
  • G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
  • G01K7/183—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer characterised by the use of the resistive element
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
  • G01K7/26—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being an electrolyte
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/19—Control of temperature characterised by the use of electric means
  • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
  • G05D23/24—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor
  • G05D23/2401—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor using a heating element as a sensing element
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K2205/00—Application of thermometers in motors, e.g. of a vehicle
  • G01K2205/04—Application of thermometers in motors, e.g. of a vehicle for measuring exhaust gas temperature

Definitions

• the invention is based on a method according to the preamble of independent claim 1.
• the invention also provides a computer program and a computer program product with a program code which is stored on a machine-readable carrier for carrying out the method.
• the determination of the operating temperature of the sensor due to the internal resistance of the Nernst measuring cell is only possible to a limited extent, since the temperature characteristic of the resistance of the electrolyte forming the sensor due to their course only within a limited temperature range a precise Measurement allows. In addition, this characteristic has a varying offset due to the lead resistance. The characteristic is also subject to errors due to printing inaccuracies.
• the inventive method with the features of claim 1 has the advantage that a determination of the temperature of a probe for determining an oxygen concentration in gas mixtures over a wide temperature range with high precision is possible.
• the internal resistance of the Nernst measuring cell is determined in a first temperature range and from this the temperature of the Nernst measuring cell is concluded, and that in a second temperature range the internal resistance of the heating device is determined and from this to the temperature of the Nernst measuring cell is closed.
• the determination of the internal resistance of the heater and the closing of this internal resistance to the temperature of the Nernst measuring cell in the second temperature range when the heater is switched off can always be used in which the heating is not subjected to a voltage / current.
• the two temperature ranges do not overlap, but are separated from each other.
• the first temperature range ends below the operating temperature of the probe, whereas the second temperature range begins above the operating temperature of the probe.
• the temperature of the probe is determined based on a determination of the internal resistance of the heater. This is based on the idea that the characteristic of the internal resistance of the heater is linear and also in the range at higher temperatures has a slope that allows a sufficiently large resolution.
• the temperature ranges overlap.
• the temperature of the Nernst measuring cell is determined both from the determination of the internal resistance of the Nernst measuring cell and from the determination of the internal resistance of the heating device.
• the internal resistance of the Nernst measuring cell is preferably used, the lead proportion is compensated, as in the above-mentioned DE 198 38 456 Al, to which reference is made, is explained.
• the second temperature value is used to check the plausibility of this value.
• both the inner Resistance of the Nernst measuring cell and the resistance of the heater are determined and calibrated by comparing the internal resistance of the Nernst measuring cell with the resistance of the heater, the absolute value of the temperature characteristic of the resistance of the heater.
• the calibration takes place in a temperature range in which a very precise temperature determination is possible by determining the internal resistance of the Nernst cell.
• This calibration is new when new, it is stored and used over the life of the probe. In that regard, it is possible to compensate for the error caused by the aging of the internal resistance of the Nernst measuring cell, since the internal resistance of the heating device is known here.
• a separation of an offset error and a proportional error falsifying the characteristic can be made by comparing the internal resistance of the switched-on heating device with the internal resistance of the switched-off heating device to the Ratio of the meander resistance of the meandering heater applied to the supply line resistance can be closed.
• the offset error can be separated from the proportional error and, since the offset error is eliminated by the calibration, the proportional error of the linear characteristic can also be compensated.
• Fig. 2a schematically shows the internal resistance of the Nernst cell above the temperature
• Fig. 2b shows schematically the internal resistance of the heater over the
• FIG. 3 schematically shows the method according to the invention for controlling the temperature of a sensor on the basis of the temperature characteristics of the resistance of the Nernst cell shown in a diagram and of the internal resistance of the heating device;
• Fig. 4 shows schematically a circuit for detecting the internal resistance of the heater
• Fig. 5 shows schematically another circuit for detecting the internal resistance of the heater.
• FIG. 1 shows a measuring sensor 10 in a sectional view through a measuring head.
• the sensor 10 is designed as a planar broadband sensor and consists of a number of individual, superposed layers, which can be structured, for example, by film casting, stamping, screen printing, laminating, cutting, sintering or the like.
• the achievement of the layer structure should not be discussed in the context of the present description, since this is known.
• the sensor 10 is used to determine an oxygen concentration in exhaust gases of internal combustion engines to a control signal for adjusting a fuel-air mixture with which the internal combustion engine operated is going to get.
• the sensor 10 has a Nernst measuring cell 12 and a pumping cell 14.
• the Nernst measuring cell 12 has a first electrode 16 and a second electrode 18, between which a solid electrolyte 20 is arranged.
• the electrode 16 is exposed to the exhaust gas 24 to be measured via a diffusion barrier 22.
• the measuring sensor 10 has a measuring opening 26, which can be acted upon by the exhaust gas 24. At the bottom of the measuring opening 26, the diffusion barrier 22 extends, wherein it leads to the formation of a cavity 28 within which the electrode 16 is arranged.
• the electrode 18 of the Nernst measuring cell 12 is arranged in a reference air channel 30 and exposed to a reference gas, for example air, in the reference air channel 30.
• a reference gas for example air
• the solid electrolyte 20 is yttria-stabilized zirconia, while the electrodes 16 and 18 are platinum and zirconia, for example.
• the measuring sensor 10 is connected to a circuit arrangement 32, which is merely indicated here, and which serves to evaluate signals from the measuring sensor 10 and to control the measuring sensor 10.
• the electrodes 16 and 18 are in this case connected to inputs 34 and 36, respectively, against which a detection voltage UD of the Nernst measuring cell 12 is applied.
• the pumping cell 14 consists of a first electrode 38 and a second electrode 40, between which a solid electrolyte 42 is arranged.
• the solid electrolyte 42 in turn consists, for example, of a yttria-stabilized zirconium oxide, while the electrodes 38 and 40 may in turn consist of platinum and zirconium oxide.
• the electrode 38 is likewise arranged in the cavity 28 and thus likewise exposed to the exhaust gas 24 via the diffusion barrier 22.
• the electrode 40 is covered with a protective layer 44 which is porous so that the electrode 40 is directly exposed to the exhaust gas 24.
• the electrode 40 is connected to an input 46 of the circuit arrangement 32, while the electrode 38 is connected to the electrode 16 and lies together therewith at the input 34 of the circuit arrangement 32.
• the sensor 10 further comprises a heater 50, which is formed by a so-called Bankfeldander and is connected to inputs 52 and 54 of the circuit 32. At the inputs 52 and 54, a heating voltage UH can be applied by means of a control circuit 56
• the exhaust gas 24 is above the measuring opening 26 and the diffusion barrier 22 in the cavity 28 and thus at the electrodes 16 of the Nernst measuring cell 12 and the electrode 38 of the pumping cell 14 at. Due to the oxygen concentration present in the exhaust gas to be measured, an oxygen concentration difference between the electrode 16 and the electrode 18 exposed to the reference gas is established. Via the connection 34, the electrode 16 is connected to a current source of the circuit arrangement 32, which supplies a constant current. Due to an existing difference in oxygen concentration at the electrodes 16 and 18, a certain detection voltage (Nernst voltage) UD is established. The Nernst measuring cell 12 in this case operates as a lambda probe, which detects whether a high oxygen concentration or a low oxygen concentration is present in the exhaust gas 24. Based on the oxygen concentration, it is clear whether the fuel-air mixture with which the internal combustion engine is operated is a rich or a lean mixture. When changing from the rich to the lean region or vice versa, the detection voltage UD drops or increases.
• the detection voltage UD is used for determining a pumping voltage UP, with which the pumping cell 14 is acted upon between its electrodes 38 and 40, respectively.
• the pumping voltage UP is negative or positive, so that the electrode 40 is connected either as a cathode or anode.
• a pump current IP which can be measured via a measuring device of the circuit arrangement 32, is established.
• oxygen ions are pumped from the electrode 40 to the electrode 38 or vice versa.
• the measured pumping current IP serves to activate tion of a device for adjusting the fuel-air mixture with which the internal combustion engine is operated.
• the heating voltage UH can be applied to the outputs 54 and 52 of the circuit 32 via the regulating device 56, so that the heating device 50 can be switched on or off.
• the sensor 10 can be brought to an operating temperature of about 780 0 C. Due to speed fluctuations of the exhaust gas 24 and / or temperature fluctuations of the exhaust gas 24, the sensor 10 is acted upon by the exhaust gas 24 with a certain fluctuating heat energy. Depending on the heating of the sensor 10 via the exhaust gas 24 is a connection or disconnection of the heater 50 is necessary.
• the circuit arrangement 32 has a measuring circuit 58, via which an alternating internal resistance of the Nernst measuring cell 12 including its supply lines to the circuit arrangement 32 can be measured.
• the AC internal resistance of the Nernst measuring cell 12 is temperature-dependent, so that the Nernst measuring cell 12 can be used to determine the operating temperature by the measured AC internal resistance. Depending on the determined operating temperature, the measuring circuit 58 provides a signal 60 for the heating control 56.
• the determination of the AC internal resistance of the Nernst measuring cell 12 is known per se and is evident, for example, from DE 198 38 456, there column 4, lines 57 to column 6, line 10, to which reference is made in full herein.
• the measurement via the electrolyte resistance Ri of the Nernst measuring cell 12 takes place using the NTC effect.
• the temperature is determined and the heating power is adjusted accordingly, so that the probe is regulated to operating temperature. If the probe is not heated internally, but only by the exhaust gas, the ambient or exhaust gas temperature can be determined via the resistance measurement. However, this measurement is only available in a limited Temperature range up to about 800 ° C possible. A measurement above this temperature is not readily possible.
• the metallic resistance of the heater 50 shows a linear increase shown in FIG. 2b and a steep increase in temperature in the higher temperature range of 800.degree.
• the internal resistances of the heater 50 are about one order of magnitude lower than the internal resistances of the Nernst cell 12, so that an unknown offset, for example, by a lead resistance, leads to an increased error of the correlation of internal resistance of the heater 50 and ambient or exhaust gas temperature.
• a determination of the temperature by means of the internal resistance R 1 of the Nernst cell 12 and a determination of the temperature based on the internal resistance R 1 of the heater to a second temperature range, as shown schematically in Fig. 3.
• a first temperature range denoted by I
• the determination of the temperature of the sensor is determined by determining this internal resistance.
• Il in which the internal resistance of the Nernst cell 12 exceeds the temperature. temperature changes only slightly, the determination of the temperature of the sensor is carried out by determining the internal resistance of the heater 50th
• the calibration of the temperature characteristic of the internal resistance of the heater 50 is now carried out such that at a temperature T ⁇ due to the temperature characteristic 210 of the internal resistance of the Nernst cell 12 a precise temperature determination is made. Based on this measurement or several such measurements, the characteristic of the internal resistance of the heater 50 is now calibrated with respect to its absolute value. At high temperatures in the region II, the determination of the temperature is now based on the thus calibrated temperature characteristic of the internal resistance of the heater 50th
• the above-described temperature measurement takes place when the heating device is switched off. In a clocked controlled heater, it always takes place in the time intervals in which the heater is not acted upon by a current / voltage.
• the detection can take place, for example, when - as shown in Fig. 4 - the heater is not acted upon by the battery voltage U Bat , but is connected by an example electronic switch 410 with a measuring circuit that includes a shunt resistor R Sh u n t at which the voltage drop across it is measured by a voltmeter 420 and thus the internal resistance is determined.
• the shunt resistor R Sh u n t may have a value of 3 ohms, which enables a very accurate resistance determination, for example, as in the case of the switched off heating also at a larger shunt resistor R Shun t no emerging through the resistance loss reduces the power of the heating device.
• the ratio of the meander resistance to the lead resistance can be concluded that the ratio of the meander resistance to the lead resistance.
• an error 240 attributable to the heating meander can be distinguished from an error 250 (see FIG. 2b) to be assigned to the supply lines.
• the resistance of the heater is in fact formed by the supply and meander resistance, with the meander resistance in particular showing a dependence on the temperature. Now, if the resistance is measured at two temperatures, for example, immediately after the start of the vehicle and at a time during which the operating temperature of the sensor is already reached from 780 0 C, the resistance change of the heater 50 and from the meandering resistance, the proportional for resistance change is to be determined.
• the proportion of the supply lines can be determined from the resistance of the heating device 50. This also makes it possible to distinguish an offset error from a proportional error. Compensation of the offset error and the proportional error may also be due to two or more measurement points at two or more temperatures. The prerequisite for this is the above-described calibration of the characteristic curve 220 at a point T K due to the exact temperature determination by the temperature characteristic 210 of the internal resistance of the Nernst cell 12.
• a measurement of the internal resistance R H of the heating device 50 can also be carried out by a circuit shown schematically in Fig. 5 via a shunt, which is connected in parallel to a current-free output of a field effect transistor 510.
• This shunt Rs h u n t 2 has a value of, for example, a kilo-ohms in this case. In this case, there is no need to switch between a switched on and a switched off heating.
• the method described above can be implemented, for example, as a computer program on a computing device, in particular a control device of an internal combustion engine, and run there.
• the program code may be stored on a machine-readable medium that the controller may read.

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• General Physics & Mathematics (AREA)
• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Analytical Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Molecular Biology (AREA)
• Automation & Control Theory (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Measuring Oxygen Concentration In Cells (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)

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• 2006
  • 2006-11-15 DE DE102006053808.0A patent/DE102006053808B4/de not_active Expired - Fee Related
• 2007
  • 2007-10-23 US US12/374,362 patent/US8201998B2/en not_active Expired - Fee Related
  • 2007-10-23 RU RU2009122509/28A patent/RU2453834C2/ru not_active IP Right Cessation
  • 2007-10-23 CN CN2007800423625A patent/CN101535799B/zh not_active Expired - Fee Related
  • 2007-10-23 JP JP2009511532A patent/JP4814996B2/ja not_active Expired - Fee Related
  • 2007-10-23 WO PCT/EP2007/061322 patent/WO2008058834A1/de active Application Filing
  • 2007-10-23 EP EP07821686A patent/EP2092317A1/de not_active Withdrawn

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