Method for operating a sensor for determining at least one proportion of a gas in a measurement gas space - Patents.com

Abstract

A method is proposed for operating a sensor (100) for determining at least one proportion of a gas in a measurement gas space, in particular a sensor (100) for detecting at least one proportion of a molecular measurement gas component and / or a measurement gas component having oxygen bound thereto. The sensor (100) comprises a sensor element (110) for detecting at least one proportion of a gas in a measurement gas space, a heating element (148) for heating the sensor element (110) and a heating voltage (U) applied to the heating element (148). H and a voltage source (152) for applying a first heating voltage (U) when a first temperature measurement is valid at a first time. H1 ) and applying a second heating voltage (U H2 ), and applying a third heating voltage (U H3 ) when the temperature of the sensor element (110) is below a predetermined threshold, applying a first heating voltage (U H1 ), the second heating voltage (U H2 ) and / or the third heating voltage (U H3 ) is applied.

Description

[Technical Field]

[0001] Conventional technology In the following, the present invention will be described with reference to a method and an apparatus that is used to quantitatively and / or qualitatively detect at least one proportion of a gas in a measurement gas space, without limiting other possible configurations. [Background technology]

[0002] For example, the gas may be the exhaust gas of an internal combustion engine, in particular in the automotive field. The measurement gas space may be, for example, an exhaust pipe. The sensor element may be, for example, a lambda sensor, in particular a binary jump sensor or a wideband lambda sensor. Lambda sensors are described, for example, in "Robert Bosch GmbH: Sensoren im Kraftfahrzeug, 1.Auflage 2010" (Robert Bosch: Sensors in Automotive Vehicles, 1st Edition, 2010), pp. 160 to 165.

[0003] The gas proportions can be, for example, components of the target gas, such as oxygen and / or nitrogen and / or nitrogen oxides and / or hydrocarbons and / or other types of gases. Basically, the sensor element can be connected to other sensors, such as NO xThe lambda sensor may be a sensor. Sensor elements of the above-mentioned type may be based, in particular, on the use of one or more solid electrolytes, i.e., on the use of solids, especially ceramic solids, that have ion-conducting, especially oxygen-ion-conducting, properties. Examples of such solid electrolytes are solid electrolytes based on zirconium dioxide, for example, yttrium-stabilized zirconium dioxide (YSZ) and / or scandium-doped zirconium dioxide (ScSZ). In the case of lambda sensors, especially wideband lambda sensors, the amount of oxygen (O2) and / or rich gases diffusing into the cavity during measurement can be measured, for example, based on a limiting current, especially in individual cells, and / or based on a pumping current required for closed-loop control of the cavity concentration to λ=1, especially in double cells. For example, the flowing measurement current can be proportional to the O2 content and / or rich gas content in the exhaust gas. The measurement of the cavity concentration can be performed based on determining the Nernst voltage between a Nernst electrode in the cavity and an oxygen-purged and / or air-purged reference electrode in the reference space. The linear relationship between the limiting current and the oxygen partial pressure allows the measurement of the oxygen partial pressure in the exhaust gas.

[0004] Furthermore, so-called particulate sensors are known. In particulate sensors, the concentration of particles, such as soot or dust particles, in exhaust gas is measured using two electrodes arranged on a ceramic. This can be done, for example, by measuring the electrical resistance of the ceramic material separating the two electrodes. More precisely, the current flowing between the electrodes is measured when a voltage is applied to the electrodes. Due to electrostatic forces, soot particles accumulate between the electrodes and over time form a conductive bridge between the electrodes. As this bridge increases, the measured current also increases. Therefore, short circuits at the electrodes increase.

[0005] Furthermore, sensors are known that detect the proportion of at least one measurement gas component having bound oxygen in a gas mixture, in particular in the exhaust gas of an internal combustion engine, by detecting the proportion of oxygen produced by reduction of the measurement gas component having bound oxygen in the presence of molecular oxygen.

[0006] NO x Sensors for detecting the proportion of at least one measured gas component having bound oxygen in a gas mixture, which may also be referred to as sensors or nitrogen oxide sensors for short or simplified purposes, are described, for example, in "Reif, K., Deitsche, KH. et al., "Kraftfahrtechnisches Taschenbuch (Automotive Technology Handbook)", Springer Vieweg, Wiesbaden, 2014, pp. 1338 to 1347.

[0007] Nitrogen oxide sensors (NO x The nitrogen oxide sensor (NO 2 ) functions according to the limiting current principle, similar to oxygen sensors, for example lambda sensors. Such nitrogen oxide sensors consist of a Nernst concentration cell, also called a reference cell, a modified oxygen pumping cell, and another modified oxygen pumping cell, the so-called NO 2 . x The oxygen pumping cell includes an outer pumping electrode exposed to the exhaust gas and an inner pumping electrode in a first hollow chamber separated from the exhaust gas by a diffusion barrier. A Nernst electrode is also disposed in the first hollow chamber, and a reference electrode is disposed in the reference gas chamber, forming a Nernst or reference cell together with the Nernst electrode. x The cell is NO x It includes a pumping electrode and a counter electrode. x The pumping electrode is disposed in a second cavity connected to the first inner cavity and separated from the first inner cavity by a diffusion barrier. The counter electrode is disposed in the reference gas chamber. All of the electrodes in the first and second cavity have a common feedback conductor.

[0008] During operation of the nitrogen oxide sensor, oxygen is removed from a first cavity in the so-called O2 cell, which is connected to the exhaust gas via a diffusion barrier. The resulting pumping current is proportional to the oxygen content of the ambient air in the measuring gas stream or the exhaust gas stream. x Nitrogen oxide is pumped into the cell. Nitrogen oxide NO in the atmosphere in the second cavity. x is reduced or decomposed by applying a constant pumping voltage. The oxygen, preferably nitrogen oxide NO, produced by the reduction or decomposition of the measurement gas component in the second cavity is x The oxygen resulting from the reduction of NO is pumped into the reference gas chamber. x Cell resistance and nitrogen oxides NO x The pumping current, i.e., nitrogen oxides NO, x The NO content is proportional to the oxygen content. x A pumping current is generated that represents the measurement signal.

[0009] In systems with internal combustion engines, complex exhaust gas aftertreatment systems are used to comply with emission limits. In diesel systems, this includes multiple sensors to measure oxygen and nitrogen oxide concentrations. In particular, NO x The sensor measures both O2 and NO x These sensors typically consist of a sensor element as a measuring sensor and a small control unit (SCU). The measuring sensor measures the O2 concentration and NO2 concentration by an electrochemical process. x The SCU converts the O2 concentration and NO2 concentration into current signals. x It calculates the concentrations and sends them to the engine control unit (ECU) via a CAN interface.

[0010] The above-mentioned exhaust gas sensors are equipped with heating elements to ensure their respective functioning. The heater of a particle sensor, for example, is used to regenerate the sensor element, which burns off soot during regeneration. In this case, the heater is only driven transiently. Other sensors only function at a sufficiently high operating temperature of the sensor ceramic and are therefore continuously heated to a specific target temperature.

[0011] The particle sensor has a built-in temperature measuring element with a measurement range of -40°C to 950°C to allow precise control of regeneration. x In sensors and lambda sensors, the temperature of the sensor element is determined via the internal resistance of the sensor ceramic. This internal resistance can only be measured once an elevated temperature has been reached, depending on the sensor element and the evaluation logic used (analog circuitry or ASIC). The sampling rate for the internal resistance of the sensor ceramic when using an ASIC is typically 5 ms. For example, in the case of analog circuits used in binary lambda sensors, the sampling rate is 300 ms to 600 ms. Due to the significantly lower sampling rate, closed-loop control of the temperature is carried out via a calibratable pre-regulation component (MAP control) and a closed-loop control component (PID control). Additionally, the actual sampling rate can be significantly lower, since measurements based on unfavorable physical conditions must be discarded.

[0012] Although the sensors and methods for operating such known sensors known from the prior art have advantages, they still have room for improvement. Here, closed-loop control components are typically limited to about 2.5 V to prevent the sensor from overheating despite low sampling rates. With typical preconditioning components of less than 8 V, a maximum effective heating voltage of 10.5 V can be required in closed-loop control operation. However, most manufacturers allow a maximum effective heater voltage of 12 V. This often results in the heater temperature not being able to dynamically track ambient conditions, and the sensor tends to operate at a lower temperature than necessary for maximum signal accuracy in oxygen measurement. [Prior art documents] [Non-patent literature]

[0013] [Non-Patent Document 1] Robert Bosch GmbH: Sensoren im Kraftfahrzeug, 1.Auflage 2010 (Robert Bosch: Sensors in the Automotive Industry, 1st Edition, 2010), pp. 160-165 [Non-patent document 2] Reif, K., Deitsche, KH. et al., "Kraftfahrtechnisches Taschenbuch (Handbook of Automotive Technology)", Springer Vieweg, Wiesbaden, 2014, pp. 1338-1347 Summary of the Invention [Problem to be solved by the invention]

[0014] Disclosure of the Invention Thus, a method is proposed for operating a sensor that identifies at least one proportion of gas in the measurement gas space, which at least largely avoids the drawbacks of known methods for operating sensors and enables faster heating of the sensor, more dynamic closed-loop control operation with faster temperature tracking, and heating with an effective maximum allowable heating voltage (corresponding to the sensor specifications) taking into account component protection. [Means for solving the problem]

[0015] Therefore, in a first aspect of the present invention, a method for operating a sensor for determining at least one proportion of a gas in a measurement gas space, in particular a sensor for detecting at least one proportion of a molecular measurement gas component and / or a measurement gas component having oxygen bound thereto, is proposed. The sensor comprises a sensor element for detecting at least one proportion of a gas in the measurement gas space, a heating element for heating the sensor element, and a voltage source for applying a heating voltage to the heating element. The method comprises the following steps: applying a first heating voltage if a first temperature measurement is valid at a first time point; applying a second heating voltage if the second temperature measurement is invalid at a second time point subsequent to the first time point; applying a third heating voltage if the third temperature measurement is invalid at the second time point and at least one third time point subsequent to the second time point; preferably in the above order, wherein the first heating voltage, the second heating voltage and / or the third heating voltage are applied when the temperature of the sensor element is below a predetermined threshold.

[0016] The method exploits the knowledge that the sensor temperature at the time of the temperature measurement is accurately known. When queried by the closed-loop control algorithm, the sensor is allowed to heat up with the maximum permissible heating voltage for a short period of time. If the most recent temperature measurement is missing, the heating voltage must be reduced. The sensor is driven for a relatively long period within the temperature range (close to the target value) specified by the manufacturer. This reduces the aging phenomenon of the sensor ceramic. Furthermore, the signal measurement accuracy can be increased, which leads to lower exhaust gas emissions. The sensor temperature can be adjusted more dynamically, which better avoids cooling the sensor even in the case of relatively cold exhaust gases.

[0017] It should be noted that the magnitude of each heating voltage is not fixed to a single value. Temperature control is essentially performed via a PID control circuit. The applied heating voltage therefore depends on the control deviation, the temperature-time profile, and the selected parameters. The first through third heating voltages correspond to the respective upper limits of the control circuit output for component protection reasons, and in the case of the first heating voltage, to the manufacturer's specifications. In other words, the magnitude of each heating voltage can be adjusted to the deviation of the actual temperature from the setpoint temperature.

[0018] The first heating voltage may be greater than the second heating voltage, which may be greater than the third heating voltage, and accordingly, the heating voltages are reduced in steps or continuously if the temperature measurement is invalid.

[0019] The first heating voltage may be the maximum permissible heating voltage. The second heating voltage may be a predetermined limited heating voltage. The third heating voltage may be a pre-adjusted heating voltage. The sensor is driven for a relatively long period within a temperature range (close to a target value) specified by the manufacturer. This reduces the aging phenomenon of the sensor ceramic. Furthermore, the signal measurement accuracy can be increased, which leads to lower exhaust gas emissions. The sensor temperature can be controlled more dynamically in a closed loop, which can better avoid cooling of the sensor in the case of relatively cold exhaust gases.

[0020] The method may further include applying a first heating voltage if the second temperature measurement is valid at the second time point, and correspondingly, extending the duration of application of the first heating voltage.

[0021] The method may further include applying the first heating voltage until a second time point during which the second temperature measurement is invalid, and correspondingly, the first heating voltage may be applied until a valid measurement is calculated.

[0022] The method may further include applying the first heating voltage if a third temperature measurement is valid at a third time point or if a fourth temperature measurement is valid at a fourth time point subsequent to the third time point. Correspondingly, the heating voltage may be increased (again) as soon as a valid temperature measurement is obtained.

[0023] The first heating voltage may be applied for a predetermined period of time between 200 ms and 2000 ms, preferably between 300 ms and 1800 ms, and more preferably between 400 ms and 1200 ms, such that operation at the maximum allowable heating voltage is only possible for a relatively short time, thereby avoiding damage to the sensor.

[0024] The sampling rate for temperature measurements may be at least 4 ms. Temperature measurements are thus taken as needed or according to the circuitry within the control device.

[0025] The first heating voltage may be in the range of 12V to 14V. The second heating voltage may be in the range of 9.0V to 11.5V. The third heating voltage may be 9V or less. For example, the third heating voltage may be in the range of 5V to a maximum of 9V. In this case, the magnitude of the heating voltage may be increased as the predetermined time for applying the heating voltage is shortened. Thus, the shorter the voltage application time, the higher the voltage may be.

[0026] Also proposed is a computer program arranged to carry out the steps of the method according to the invention.

[0027] Furthermore, an electronic storage medium is proposed which stores a computer program for implementing the method according to the invention.

[0028] Furthermore, an electronic control unit is proposed, which comprises an electronic storage medium according to the invention containing the above-mentioned computer program for implementing the method according to the invention.

[0029] Finally, the present invention provides a sensor for determining at least one proportion of a gas in a measurement gas space, in particular a sensor for detecting at least one proportion of a molecular measurement gas component and / or a measurement gas component having oxygen bound thereto, the sensor comprising a sensor element for detecting at least one proportion of a gas in the measurement gas space, a heating element for heating the sensor element, and a voltage source for applying a heating voltage to the heating element, the sensor further comprising: applying a first heating voltage when a first temperature measurement is valid at a first time point; applying a second heating voltage if the second temperature measurement is invalid at a second time point subsequent to the first time point; applying a third heating voltage if the third temperature measurement is invalid at the second time point and at least one third time point subsequent to the second time point; The sensor is further configured to apply a first heating voltage, a second heating voltage, and / or a third heating voltage when the temperature of the sensor element is below a predetermined threshold.

[0030] The sensor may further include a control device according to one of the embodiments described above or below.

[0031] Within the scope of the present invention, a solid electrolyte is to be understood as a body or object having electrolytic properties, i.e., ion-conducting properties. In particular, a solid electrolyte may be a ceramic solid electrolyte. This also includes raw materials of solid electrolytes, and therefore also includes so-called green or brown sheets that only become solid electrolytes after sintering. In particular, a solid electrolyte can be formed as a solid electrolyte layer or can be formed from multiple solid electrolyte layers. Within the scope of the present invention, a layer is to be understood as a mass that is located above, below, or between other elements and has a planar extension at a certain height.

[0032] Within the scope of the present invention, an electrode is generally understood to be an element capable of contacting a solid electrolyte such that a current can be maintained between the solid electrolyte and the electrode. Thus, an electrode may comprise an element capable of introducing ions into the solid electrolyte and / or removing ions from the solid electrolyte. Typically, the electrode comprises a noble metal electrode, which can be deposited on the solid electrolyte, for example, as a metal-ceramic electrode, or can be connected to the solid electrolyte in another way. A typical electrode material is a platinum cermet electrode. However, in principle, other noble metals, such as gold or palladium, can also be used.

[0033] Within the scope of the present invention, a heating element is understood to mean an element used to heat the solid electrolyte and electrodes at least to their functional temperature, preferably to their operating temperature. The functional temperature is the temperature above which the solid electrolyte becomes ionically conductive, which is approximately 350°C. The operating temperature is the temperature at which the sensor element is typically operated, which is to be distinguished from the functional temperature. The operating temperature can be, for example, 700°C to 950°C. The heating element can include a heating region and at least one lead wire. Within the scope of the present invention, a heating region is understood to mean a region of the heating element that overlaps with the electrodes in a layered structure along a direction perpendicular to the surface of the sensor element. The heating region is typically heated more strongly during operation than the lead wire, and therefore the heating region and the lead wire can be distinguished. For example, different heating can be achieved by the heating region having a higher electrical resistance than the lead wire. The heating region and / or the lead wire are, for example, formed as an electrically resistive path and heated by applying a voltage. The heating element can be made, for example, from a platinum cermet.

[0034] Within the scope of the present invention, a measurand is to be understood as basically any physical and / or chemical quantity and a signal that represents this quantity equivalently, i.e., an equivalent signal. Preferably, the measurand is at least one measurement signal of a sensor element. Preferably, the measurand can be at least one pumping current, for example, a limiting current. For example, the measurand can be a quantity that depends on the pumping current. For example, the measurand can be a pumping voltage and / or a converted charge. In this context, the expression "detected" within the scope of the present invention is to be understood as meaning that the measurand is output from the sensor element, for example as a measurement signal, and / or that the measurand is processed and / or evaluated and / or stored by a control device.

[0035] A diffusion barrier can be understood as, for example, a layer made of a material that inhibits the flow of gases and / or liquids and / or gas mixtures and / or gas components, while the layer promotes the diffusion of gases and / or liquids and / or gas mixtures and / or gas components and / or ions.

[0036] A cavity can be understood to mean a space in the sensor element that is structurally separated from the measurement gas space, but to which gas components and / or gas mixtures and / or gases from the measurement gas space can be supplied, for example, via at least one gas inlet and / or diffusion barrier. The cavity can be, for example, a chamber. The device can have at least one reference gas chamber and / or at least one reference gas passage. The solid electrolyte can preferably be an ionically conductive solid electrolyte. Gas exchange, in particular of gases and / or at least part of them, can be preferably by diffusion through the diffusion barrier, in particular towards the cavity.

[0037] The numerical designations "first", "second", etc. are used merely as designations and terminological distinctions of components and features, and these designations do not convey any information regarding, in particular, order, weight, or whether, for example, there are further components or other features of that type.

[0038] Further optional details and features of the invention will become apparent from the following description of a preferred embodiment, which is illustrated diagrammatically in the drawings. [Brief explanation of the drawings]

[0039] [Figure 1] 1 is a diagram showing the basic structure of a sensor according to the present invention; [Figure 2] FIG. 1 is a block diagram illustrating signal processing for compensating for sensor aging according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0040] Embodiments of the invention FIG. 1 shows the basic structure of a sensor 100 according to the invention, which is particularly suitable for carrying out the method according to the invention.

[0041] The sensor 100 is configured to determine the proportion of at least one gas in a measurement gas space. By way of example only, the sensor 100 may determine the proportion of a molecular measurement gas component and / or a measurement gas component having bound oxygen (hereinafter referred to as nitrogen oxide NO ) in a gas mixture, for example in the exhaust gas of an internal combustion engine. x To this end, the sensor 100 includes a sensor element 110. The sensor element 110 has a first pumping cell 112 arranged between an outer pumping electrode 114 and an inner pumping electrode 116, where the pumping electrodes 114, 116 are interconnected by a solid electrolyte 117. In this case, the outer pumping electrode 114, which is separated from the surroundings of the sensor 100 by a porous aluminum oxide layer 118, has a first conductive connection 120 via which a first pumping current I is generated in the first pumping cell 112. P1 is generated. For this purpose, the conductive connection 120 is connected to a terminal P1 of an electronic control device 122. The control device 122 may be part of the sensor 100 or may be connected to the sensor 100. In order to complete the current circuit, the inner pumping electrode 116 likewise has a conductive connection 124 leading to a common terminal COM of the electronic control device 122. The first pumping cell 112 is located adjacent to a first cavity 126, which is located inside the sensor element 110 and is connected to the measurement gas. A first pumping current I P1 By generating a diffusion barrier 128, a first proportion of oxygen ions formed from the molecular oxygen of the gas mixture are transported between the first cavity 126 and the ambient of the sensor 100. Two diffusion barriers 128 are provided in the inlet path from the ambient to the first cavity 126.

[0042] The sensor element 110 further comprises an electrical reference cell 130 having a Nernst electrode 132 and a reference electrode 134. The Nernst electrode 132 has a conductive connection 124 to the common terminal COM together with the inner pumping electrode 116, while the reference electrode 134 has a separate conductive connection 136 to a terminal Vs for a Nernst voltage Vs of the external electronic control device 122. The reference cell 130 is located adjacent to a reference gas chamber 138. A second proportion of oxygen ions from the measurement gas space 126 and / or from the surroundings of the sensor 100 is transported to the reference gas chamber 138 by applying a reference pumping current between terminal Vs and the common terminal COM, the value of which is set so that a defined proportion of oxygen ions is formed in the reference gas chamber 138. Preferably, in this regard, a first pumping current I P1 is also set to produce a defined ratio between a first proportion of oxygen ions in the measurement gas space 126 and a second proportion of oxygen ions in the reference gas space 138.

[0043] Further contained in the gas mixture are measurement gas components with bound oxygen, namely nitrogen oxides NO x is hardly affected by diffusion, and the "NO x The second pumping cell 140, sometimes referred to as the "pumping cell," x Pumping electrode 142 and NO x The sensor element 110 has a counter electrode 144 and is positioned adjacent to a second cavity 145 inside the sensor element 110. The second cavity 145 is separated from the first cavity 126 by one of a plurality of diffusion barriers 128. At least one of the two electrodes, i.e., the NO x Pumping electrode 142 and / or NO x When a voltage is applied to the counter electrode 144, the measurement gas component NO x Further molecular oxygen can be produced in the second pumping cell 140 by catalytic action from the

[0044] NOx The pumping electrode 142 does not have a conductive connection to the common terminal COM, but x The counter electrode 144 is connected to a second pumping current I P2 The second pumping cell 140 has a conductive connection 146 through which a second pumping current I can be applied to the second pumping cell 140. For this purpose, the conductive connection 146 is connected to a terminal P2 of the external electronic control device 122. P2 is applied to the second pumping cell 140, a predetermined percentage of additional oxygen ions formed from the additional molecular oxygen are transported into the reference gas chamber 138.

[0045] The sensor element 110 further comprises a heating element 148, which is connected by two leads 150 to the terminals HTR+ and HTR- of the control device 122, via which a heating current can be introduced into the heating element 148, which generates a heating power to bring the sensor element 110 to the desired temperature. For this purpose, the sensor 100 supplies the heating element 148 with a heating voltage U H The voltage source 152 is open-loop or closed-loop controlled by the controller 122 and is connected to the controller 122 for this purpose.

[0046] During operation of the sensor 100, the first pumping current I of the first pumping cell 112 P1 and the voltage U applied to the first pumping cell 112 P1 The measurement signal of the sensor element 110, which indicates the measurement gas component with bound oxygen, is detected by the second pumping current I of the second pumping cell 140. P2 It is calculated based on the following.

[0047] In the following, a method for operating the sensor is described, which method can be computer-implemented. It is expressly emphasized that the subsequent method steps are executed when the temperature of the sensor element falls below a predetermined threshold. In other words, in particular, when the temperature of the sensor element 110 falls below a predetermined threshold, i.e. when an interrogation is made by the closed-loop control algorithm of the heating element 148, a heating voltage U H In this case, the temperature regulation of the sensor element 110 is performed by closed-loop control. In this case, the closed-loop control component is typically limited to about 2.5 V. With a typical pre-regulation component of less than 8 V, a predetermined limited heating voltage U of 10.5 V is applied in closed-loop control operation. Hlim In addition, the effective heating voltage U of 12V, for example, can be requested to correspond to most of the manufacturer's settings. Hmax is acceptable. Here, the temperature is measured periodically. For example, the sampling rate for temperature measurement is at least 4 ms. When an ASIC is used, the sampling rate for the internal resistance of the sensor ceramic is typically 5 ms. For example, for analog circuits used in binary lambda sensors, the sampling rate is 300 ms to 600 ms.

[0048] If at a first time a first temperature measurement is valid and therefore the temperature of the sensor element 110 is known, then the first heating voltage U H1 is applied. The first heating voltage U H1 is the maximum allowable heating voltage U Hmax , i.e., the heating voltage having a value indicated as the maximum allowable by the manufacturer of the sensor 100. For example, the first heating voltage U H1 is 12V. The first heating voltage U H1 is applied for a short predetermined period of time between 200 ms and 2000 ms, preferably between 300 ms and 1800 ms, more preferably between 400 ms and 1200 ms, for example for a short predetermined period of time of 600 ms.

[0049] At a second point in time subsequent to the first, if the second temperature measurement is invalid, for example due to a fault, the second heating voltage U H2 is applied. The first heating voltage U H1 is the second heating voltage U H2 The second heating voltage U H2 is the predetermined limited heating voltage U Hlim For example, the second heating voltage U H2 is 10.5V resulting from a maximum pre-regulation component of 8V and a closed loop control component of 2.5V.

[0050] If the second temperature measurement is valid at a second time point, the first heating voltage U H1 That is, as long as the second temperature measurement is invalid until the second time point, the first heating voltage U H1 is applied.

[0051] If the third temperature measurement is invalid at the second time point and at least one third time point subsequent to the second time point, the third heating voltage U H3 is applied. The second heating voltage U H2 is the third heating voltage U H3 The third heating voltage U H3 is the preset heating voltage U Hmap is the heating voltage corresponding to the pre-conditioning component. The third heating voltage U H3 is, for example, 8V or less.

[0052] In this method, when a third temperature measurement is valid at a third time point or when a fourth temperature measurement is valid at a fourth time point subsequent to the third time point, the first heating voltage U H1 can be (again) applied.

[0053] In this case, the practical limit for the heating voltage according to the prior art is U Hlim = 10.5V. Maximum allowable heating voltage U HMax and U limWhen the time ratio of t = 1:1, the effectively achievable energy input E using the method of the present invention can be calculated as follows: E tot =(E max *0.5+E lim *0.5) / E lim =(12 2 *0.5+10.5 2 *0.5) / 10.5 2 =1.153 It can be increased by 15%, as given by: where E tot is the total energy input, E max is the maximum allowable energy input, and E limit is the limit on energy input.

[0054] The conversion is performed by a different time debouncing that is reset with each new temperature measurement. Depending on how much time has passed since the last measurement, the closed-loop control of the heating voltage is limited to correspond to calibratable limits. More than two steps are possible, according to the following example:

[0055] An exemplary heating voltage characteristic is shown in Figure 2. On the X-axis 154, time is plotted in s. On the Y-axis 156, heating voltage is plotted in V. Curve 158 is an exemplary heating voltage characteristic over time. In a first range 160, for example, every other temperature measurement is valid. Therefore, in the method according to the invention, a first heating voltage U H1 That is, the maximum allowable heating voltage U Hmax and the second heating voltage U H2 That is, a predetermined limited heating voltage U Hlim In the second range 162, all measured values ​​are valid. Therefore, the first heating voltage U H1 is applied to the heating element 148. In the third range 164, there are no new valid measurements for a relatively long time. Therefore, the heating voltage is first increased to the second heating voltage U H2and then the third heating voltage U H3 That is, the pre-adjusted heating voltage U Hmap In a fourth range 166, which corresponds to the first valid temperature measurement after the heating voltage is reduced, the first heating voltage U H1 The (re)increase will be made up to

Claims

1. 1. A method for operating a sensor (100) for detecting a proportion of at least one molecular measurement gas component and / or a measurement gas component having bound oxygen in a measurement gas space, the method comprising: The sensor (100) comprises a sensor element (110) for detecting at least one proportion of gas in the measurement gas space, a temperature calculation circuit for performing temperature measurement by calculating the temperature of the sensor element (110) via the internal resistance of the sensor element (110), a heating element (148) for heating the sensor element (110), and a heating voltage (U) applied to the heating element (148). Ｈ and a voltage source (152) applying a voltage The method comprises: a first heating voltage (U Ｈ１ ) and At a second time point subsequent to the first time point, if a second temperature measurement is invalid due to a malfunction of the temperature calculation circuit, a second heating voltage (U H1 ) is generated that is smaller than the first heating voltage (U H1 ). Ｈ２ ) and, if the second temperature measurement is valid at the second time, applying the first heating voltage (U H1 ); a third heating voltage (U H2 ) that is smaller than the second heating voltage (U H2 ) if a third temperature measurement is invalid due to a malfunction of the temperature calculation circuit at the second time point and at least one third time point subsequent to the second time point; Ｈ３ ) and, if the third temperature measurement is valid at the third time, applying the first heating voltage (U H1 ); Including, When the temperature of the sensor element (110) is below a predetermined threshold, the first heating voltage (U Ｈ１ ), the second heating voltage (U Ｈ２ ) and / or the third heating voltage (U Ｈ３ ) is applied.

2. The first heating voltage (U Ｈ１ ) is the maximum allowable heating voltage, and the second heating voltage (U Ｈ２ ) is a predetermined limited heating voltage, and the third heating voltage (U Ｈ３ ) is the pre-adjustment heating voltage, The method of claim 1.

3. The method comprises: When a fourth temperature measurement is valid at a fourth time point subsequent to the third time point, the first heating voltage (U Ｈ１ ) further comprising applying The method of claim 1.

4. The first heating voltage (U Ｈ１ ) is applied for a predetermined period of time between 200 ms and 2000 ms; The method of claim 1.

5. The sampling rate for temperature measurements is at least 4 ms. The method of claim 1.

6. The first heating voltage (U Ｈ１ ) is 12V to 14V, and the second heating voltage (U Ｈ２ ) is 9.0V to 11.5V, and the third heating voltage (U Ｈ３ ) is 9V or less, The method of claim 1.

7. A computer program product which, when executed on a computer, causes the computer to carry out the steps of the method of claim 1.

8. An electronic storage medium storing the computer program according to claim 7.

9. An electronic control unit (122) comprising an electronic storage medium according to claim 8.

10. A sensor (100) for detecting a proportion of at least one molecular measurement gas component and / or a measurement gas component having bound oxygen in a measurement gas in a measurement gas space, the sensor comprising: The sensor (100) comprises a sensor element (110) for detecting at least one proportion of gas in the measurement gas space, a temperature calculation circuit for performing temperature measurement by calculating the temperature of the sensor element (110) via the internal resistance of the sensor element (110), a heating element (148) for heating the sensor element (110), and a heating voltage (U) applied to the heating element (148). Ｈ a voltage source (152) for applying a voltage a first heating voltage (U Ｈ１ ) is applied, At a second time point subsequent to the first time point, if a second temperature measurement is invalid due to a malfunction of the temperature calculation circuit, a second heating voltage (U H1 ) is generated that is smaller than the first heating voltage (U H1 ). Ｈ２ ) and, if the second temperature measurement is valid at the second time, applying the first heating voltage (U H1 ); a third heating voltage (U H2 ) that is smaller than the second heating voltage (U H2 ) if a third temperature measurement is invalid due to a malfunction of the temperature calculation circuit at the second time point and at least one third time point subsequent to the second time point; Ｈ３ ) and, if the third temperature measurement is valid at the third time, apply the first heating voltage (U H1 ). It is structured as follows: The sensor (100) further comprises: a first heating voltage (U) when the temperature of the sensor element (110) is below a predetermined threshold; Ｈ１ ), the second heating voltage (U Ｈ２ ) and / or the third heating voltage (U Ｈ３ ) .

11. The sensor further comprises an electronic control device (122) according to claim 9. The sensor (100) of claim 10.

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