METHOD AND SYSTEM FOR EXHAUST GAS RECIRCULATION ESTIMATING USING A LAMBDA PROBE

Abstract

Procedure, comprehensive: During the operation of a lambda probe (126) in a variable voltage mode, a reference voltage of the lambda probe (126) is adjusted from a lower, first voltage to a higher, second voltage; Setting an engine operation based on an exhaust gas recirculation quantity (EGR quantity) estimated on the basis of an output from the lambda sensor (126) and a determined correction factor based on the second voltage, where a dry air pumping current is determined from a first pumping current at the first voltage and a second pumping current at the second voltage, wherein the determined value for the dry air pump current is stored in a memory of a controller (12) and updated after each engine start, and wherein the correction factor is determined based on the second voltage using the stored dry air pump current.

Description

[0001] The present application generally relates to an exhaust gas recirculation control system based on an output from an exhaust gas sensor coupled to an exhaust system of an internal combustion engine.

[0002] Engine systems can utilize exhaust gas recirculation (EGR) from the engine's exhaust system to the engine's intake system to reduce regulated emissions and improve fuel economy. Specifically, the amount of EGR recirculated affects NOx emissions and fuel economy. Increased EGR can lead to partial combustion and misfires, resulting in higher emissions, poorer drivability, and increased fuel consumption. Various sensors can be integrated into the engine system to estimate the amount of EGR supplied to the engine. These may include temperature, pressure, oxygen, and humidity sensors connected to the intake manifold and / or exhaust manifold.

[0003] An exemplary approach to EGR measurement is presented by Kotwicki et al. in US 6,321,732 B1. In this approach, the EGR system incorporates pressure sensors mounted above a fixed orifice. These sensors measure a pressure change (e.g., a delta pressure) across the orifice. These delta pressure sensors are used to measure the pressure differential across the orifice, which is then used to control the EGR and thus the exhaust gas flow in the engine system. However, delta pressure sensors are noisy, which can lead to inaccurate EGR measurements and the aforementioned problems. Furthermore, these sensors are installed in the engine systems solely for the purpose of EGR measurement, potentially increasing manufacturing costs.

[0004] Another exemplary approach to EGR measurement is presented by Matsubara et al. in US 6,742,379 B2. In this approach, the EGR system incorporates an intake gas component sensor, such as an oxygen sensor, which can be used during non-EGR conditions to determine the oxygen content of fresh intake air. During EGR conditions, the sensor can be used to infer the EGR based on a change in oxygen concentration due to the addition of EGR as a diluent.

[0005] However, the inventors have recognized potential problems with such an approach. One or more other engine operating parameters are also affected by the inaccurate EGR reading from the intake oxygen sensor when EGR is lean or rich (relative to stoichiometry). For example, when EGR is lean, the sensor output correctly indicates the proportion of combusted gas, even if the sensor measures a lower (absolute) amount of EGR. Consequently, any adjustments to ignition timing, throttle position, and / or fuel injection based on the adjusted calibration coefficient may be inaccurate. As another example, when EGR is rich, the sensor does not provide an accurate estimate of the amount of excess fuel in the EGR.Therefore, the injected fuel mixture will be higher than desired if the excess fuel in the cylinder fuel injection is not adequately accounted for. This can lead to an open-loop engine fuel supply that is richer than desired. In a closed-loop control system, the adaptive fuel can be adjusted with respect to the excess fuel in the EGR, but the adaptive correction is attributed to a fuel system fault. This can erroneously trigger a fuel system fault if the correction exceeds a threshold. This problem can be further exacerbated by a delay between the timing of fuel injection and the fuel's detection by the intake oxygen sensor. Consequently, the engine fuel supply and EGR control can be interrupted.

[0006] From DE 10 2016 102 548 A1, a method is known in which the operation of a lambda sensor in variable voltage mode with a lower first and a higher second voltage, as well as the calculation and cyclical storage of a dry air pump current and its periodic update after each engine start, is known. However, this value is used exclusively to determine the ambient humidity during further engine operation at the first (lower) voltage and, among other things, to correct the EGR current accordingly.

[0007] Based on this state of the art, the task is to increase the long-term accuracy and robustness of the EGR control without placing an additional burden on the sensor.

[0008] According to the invention, this problem is solved by combining the features of claim 1 and claim 2. Advantageous embodiments result from the subsequent dependent claims.

[0009] In one example, some of the preceding problems can be solved by a procedure that involves adjusting engine operation based on an exhaust gas recirculation (EGR) quantity during operation of a lambda sensor in variable voltage mode (VV mode), where a reference voltage of the lambda sensor is adjusted from a lower, first voltage to a higher, second voltage. This procedure involves adjusting engine operation based on an exhaust gas recirculation (EGR) quantity estimated from an output of the lambda sensor and a correction factor determined based on the second voltage. In this way, the lambda sensor can be used for EGR estimation, and the engine fuel supply can be adjusted accordingly.

[0010] As an example, the lambda sensor can be operated in a reference mode, where the sensor operates at the lower voltage, and an output from the lambda sensor can be used to control an air-fuel ratio (AFR). Under selected conditions, however, the lambda sensor can be switched from reference mode to variable voltage (VV) mode, where the sensor operates at a higher voltage and / or modulates between the lower and higher voltages. In some examples, the higher voltage is a voltage at which water molecules are partially or completely split at the lambda sensor, while the lower voltage is a voltage at which water molecules are not split at the sensor.Thus, the selected conditions can include an engine state without fuel supply, such as deceleration fuel shut-off (DFSO), and a steady-state engine state, such as idling. Under such conditions, the oxygen sensor can generate an output that can be used to estimate the exhaust water concentration from the ethanol content in the fuel and the ambient humidity. Specifically, the ambient humidity can be estimated by operating the oxygen sensor in VV mode during a DFSO, and the ethanol content in the fuel can be estimated during an engine idle state when EGR is inactive. Therefore, the ambient humidity and the ethanol content in the fuel can be considered a correction factor and can further be used to estimate the amount of water in the exhaust gas when EGR is inactive.

[0011] Consequently, under engine idle conditions, EGR can be recirculated from the exhaust port to the intake port, and the exhaust gas sensor can be operated in VV mode to estimate the total water concentration in the exhaust gas. Thus, the total water concentration can include an additional amount of water directly related to the amount of EGR recirculated, for example, for a given fuel composition. Therefore, the amount of EGR recirculated can be estimated by subtracting the correction factor from the total water concentration.

[0012] In this way, the lambda sensor can be used to correct deviations caused by changes in fuel composition and ambient humidity, and furthermore, to estimate the amount of EGR recirculated into the system. By appropriately correcting the sensor output to compensate for the effects of fuel composition and ambient humidity, a more accurate EGR estimate can be provided by the sensor, thereby improving engine fuel delivery and EGR control. By extending the functionality of the lambda sensor (which can be used for AFR estimation in reference mode) to VV mode, the same sensor can be used to estimate all of the ethanol content in the fuel, the ambient humidity, and the water concentration in the exhaust gas, thus eliminating the need for additional sensors to measure each of these factors and thereby reducing manufacturing costs.It is understood that the probe may not operate continuously in VV mode, but rather switches back to reference mode after estimating the correction and water volume under the selected conditions. This allows the integrity of the lambda probe to be maintained, for example, by reducing probe wear.

[0013] It is understood that the foregoing summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the full description. It is not intended to mention important or essential features of the claimed subject matter, the scope of which is defined solely in the claims following the full description. Furthermore, the claimed subject matter is not limited to implementations that remedy the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows a schematic representation of an engine that includes an exhaust system and a lambda sensor. Fig. Figure 2 shows a schematic representation illustrating the operation of the lambda probe in a reference mode and a variable voltage mode (VV mode). Fig. Figure 3 shows a flowchart illustrating an exemplary procedure for estimating an amount of exhaust gas recirculation (EGR) based on an output from the lambda sensor in VV mode and further on the basis of a determined correction factor, wherein the determined correction factor includes a correction for ethanol content in the fuel and a correction for ambient humidity. Fig. Figure 4 shows a flowchart illustrating an exemplary procedure for estimating a dry air pump flow using the lambda probe in VV mode. The Fig. Figures 5-6 show flowcharts illustrating exemplary procedures for estimating ambient humidity using the lambda probe operated in VV mode and further based on the estimated dry air pump flow rate. Fig. Figure 7 shows a flowchart illustrating an exemplary procedure for accurately estimating the amount of ethanol content in the fuel using the lambda probe operating in VV mode. Detailed description

[0014] The following description concerns systems and methods for determining an exhaust gas recirculation (EGR) quantity based on outputs from an exhaust gas sensor, such as an oxygen sensor, as described in the Fig. 1-2 shown (herein referred to as lambda sensor). An engine control unit may be configured to perform a control routine, such as the exemplary procedure from Fig. 3, to determine if it is time for an EGR estimate and switch the sensor accordingly from a non-variable voltage mode to a variable voltage mode (VV mode). Thus, the sensor can operate normally in non-VV mode to estimate an air-fuel ratio (AFR) and only switch to VV mode when possible and only under selected operating conditions (e.g., engine states without fuel supply, static states, etc.). Furthermore, the controller can estimate a correction factor based on the sensor output under the selected operating conditions. In particular, the correction factor can include a correction for ambient humidity, which is estimated by operating the lambda sensor in VV mode during an engine state without fuel supply ( Fig. 5-6). Here, the lambda sensor can be operated in VV mode to determine a dry air pump flow ( Fig. 4), and the controller can estimate the ambient humidity based on the dry air pump flow ( Fig. 5-6). The correction factor may additionally include a correction for the ethanol content in the fuel, which is caused by operating the lambda sensor in VV mode during an engine idle condition, as in Fig. Figure 7 shows how to estimate the amount of additional water in the system. Ambient humidity and fuel ethanol content can be used together to determine the exhaust water concentration when no EGR recirculation is present. The control unit can operate the probe in VV mode with an EGR flow during engine idle and estimate the total exhaust water concentration based on the probe output. The control unit can then determine the amount of additional water in the system when EGR is active by subtracting the corrections for ambient humidity and fuel ethanol content from the total water concentration. This additional water is directly proportional to the amount of recirculated EGR. In this way, an accurate measurement of the amount of EGR in the system can be obtained, thereby improving EGR control.

[0015] Now, with reference to Fig. Figure 1 illustrates a schematic diagram showing a cylinder of a multi-cylinder engine 10, which may be enclosed in a drive system of an automobile. The engine 10 may be controlled, at least partially, by a control system comprising a controller 12 and by input from a driver 132 via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. A combustion chamber (i.e., a cylinder) 30 of the engine 10 may include combustion chamber walls 32 with a piston 36 positioned therein. The piston 36 may be coupled to a crankshaft 40, such that an alternating motion of the piston is translated into a rotational motion of the crankshaft. The crankshaft 40 may be coupled to at least one drive wheel of a vehicle via an intermediate gear system.Furthermore, a starter can be coupled to the crankshaft 40 via a flywheel to enable a starting process of the engine 10.

[0016] The combustion chamber 30 can draw in intake air from an intake manifold 44 via an intake port 42 and discharge combustion exhaust gases via an exhaust port 48. The intake manifold 44 and the exhaust port 48 can be selectively connected to the combustion chamber 30 via a corresponding intake valve 52 and exhaust valve 54. In some embodiments, the combustion chamber 30 can include two or more intake valves and / or two or more exhaust valves.

[0017] In this example, the inlet valve 52 and exhaust valve 54 can be controlled by cam actuation via corresponding cam actuation systems 51 and 53. The cam actuation systems 51 and 53 can each include one or more cams and utilize one or more of the following systems: cam profile adjustment (CPS), variable cam actuation (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) systems, which can be operated by the controller 12 to vary the valve operation. The position of the inlet valve 52 and exhaust valve 54 can be determined by position sensors 55 and 57, respectively. In alternative embodiments, the inlet valve 52 and / or exhaust valve 54 can be controlled by an electric valve actuator.For example, cylinder 30 may alternatively include an inlet valve controlled by an electric valve actuation and an exhaust valve controlled by cam actuation, including CPS and / or VCT systems.

[0018] In some embodiments, each cylinder of the engine 10 can be configured with one or more fuel injection devices for supplying fuel to it. As a non-limiting example, cylinder 30 is shown to include a fuel injection device 66. The fuel injection device 66 is shown to be directly coupled to cylinder 30 to inject fuel directly into it in proportion to the pulse width of the FPW signal received by the controller 12 via an electronic driver 68. In this way, the fuel injection device 66 provides so-called direct injection (hereinafter also referred to as “DI”) of fuel into the combustion cylinder 30.

[0019] It is understood that, in an alternative embodiment, the injection device 66 can be an injection device with one nozzle per intake port, which supplies fuel to the intake port upstream of the cylinder 30. It is further understood that the cylinder 30 can receive fuel from a plurality of injection devices, such as a plurality of injection devices with one nozzle per intake port, a plurality of direct injection devices, or a combination thereof.

[0020] The fuel tank in fuel system 172 can contain fuel with varying properties, such as different fuel compositions. These differences can include varying alcohol content, octane rating, heat of vaporization, fuel mixtures, and / or combinations thereof. The engine can run on an alcoholic fuel mixture, such as E85 (approximately 85% ethanol and 15% gasoline) or M85 (approximately 85% methanol and 15% gasoline). Alternatively, depending on the alcohol content of the fuel supplied by the operator at the tank, the engine can run on other ratios of gasoline and ethanol stored in the tank, including 100% gasoline and 100% ethanol and various ratios in between.Furthermore, the fuel properties of the fuel tank can often vary. For example, a driver might fill up with E85 one day, E10 the next, and E50 the following day. Thus, the fuel tank composition can change dynamically based on the level and composition of the fuel remaining in the tank at the time of refueling.

[0021] The daily fluctuations in tank refilling can therefore lead to a frequently varying fuel composition in the fuel system 172, which affects the fuel composition and / or fuel quality supplied by the injection device 66. The different fuel compositions injected by the injection device 166 can be referred to here as a fuel type. For example, the different fuel compositions can be quantitatively described by their research octane number rating (RON rating), alcohol content, ethanol content, etc.

[0022] It is understood that in one embodiment the engine can be operated by injecting the variable fuel mixture via a direct injection device, but in alternative embodiments the engine can be operated using two injection devices and varying a relative injection quantity from each injection device. It is further understood that when operating the engine with amplification from an amplification device, such as a turbocharger or supercharger (not shown), the amplification limit can be increased by increasing the alcohol content of the variable fuel mixture. In one embodiment, an exhaust gas sensor 126, which is coupled to an exhaust channel 48, can be operated in a variable voltage mode (VV mode) ( Fig. 2) can be used to estimate the amount of alcohol in the fuel injected into the engine (e.g., to estimate the ethanol content of the fuel as in Fig. 7 shown).

[0023] Continuing with Fig. 1. The intake port 42 can include a throttle 62 with a throttle valve 64. In this particular example, the position of the throttle valve 64 can be varied by the controller 12 via a signal provided to an electric motor or actuator incorporated by the throttle 62, a configuration commonly referred to as an electronic throttle control (ETC). In this way, the throttle 62 can be operated to vary the intake air supplied to the combustion chamber 30 among other engine cylinders. The position of the throttle valve 64 can be provided to the controller 12 by the throttle position signal TP. The intake port 42 can include a mass airflow sensor 120 and a manifold absolute pressure sensor 122 to provide the corresponding MAF and MAP signals to the controller 12.In one embodiment, the inlet channel 42 can additionally include a humidity sensor 121 for measuring ambient humidity. In another embodiment, the humidity sensor 121 can additionally or alternatively be placed in the outlet channel 48. In yet another embodiment, the exhaust gas sensor 126 can be operated in VV mode to measure the ambient humidity as in the [reference to a specific example]. Fig. 5-6 shown to estimate.

[0024] An ignition system 88 can provide a spark to the combustion chamber 30 via a spark plug 92 in response to a pre-ignition signal SA from the control unit 12 in selected operating modes. Although spark ignition components are shown, in some embodiments the combustion chamber 30 or one or more other combustion chambers of the engine 10 can be operated in a compression ignition mode with or without a spark.

[0025] An exhaust gas sensor 126 (e.g., a lambda probe) is shown coupled to the exhaust port 48 upstream of an emission control device 70. The exhaust gas sensor 126 can be referred to synonymously as a lambda probe, oxygen sensor, or sensor / probe. The exhaust gas sensor 126 can be any suitable sensor for providing an indication of an exhaust air-fuel ratio (AFR), such as a linear lambda probe or UEGO (universal or wide-range exhaust oxygen), a dual-state lambda probe or EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor.

[0026] The emission control device 70 is shown arranged downstream of the exhaust gas sensor 126 along the exhaust channel 48. The device 70 can be a three-way catalytic converter (TWC), a NOx trap, various other emission control devices, or combinations thereof. In some embodiments, the emission control device 70 can be periodically reset by operating at least one cylinder of the internal combustion engine within a specific air-fuel ratio during engine operation 10.

[0027] Furthermore, in the disclosed embodiments, an exhaust gas recirculation (EGR) system can direct a desired portion of the exhaust gas from the exhaust port 48 to the intake port 44 via an EGR channel 140. The amount of EGR provided at the intake port 44 can be varied by the control unit 12 via an EGR valve 142. An EGR sensor 144 can also be arranged within the EGR channel and provide a reading of one or more parameters relating to the pressure, temperature, and concentration of the exhaust gas. Under certain conditions, the EGR system can also be used to regulate the temperature of the air-fuel mixture in the combustion chamber, thereby providing a method for controlling the ignition timing in some combustion modes.Furthermore, under certain conditions, a portion of the combustion gases can be retained or captured in the combustion chamber by controlling the exhaust valve actuation, such as by controlling a variable valve actuation mechanism. Therefore, the use of additional sensors to estimate EGR can increase the manufacturing costs of the engine systems.

[0028] The inventors have realized that it is possible to operate the exhaust gas sensor 126 in a variable voltage mode (VV mode) under various engine operating conditions to determine the amount of EGR recirculated from the exhaust port to the intake port. In this way, the exhaust gas sensor 126, which is typically operated in a non-variable voltage mode (also referred to as reference mode) to measure the air-fuel ratio, can be used in a VV mode to estimate the amount of EGR. In the non-VV mode, the sensor is operated at a lower voltage, and the sensor output in the non-VV mode can be used to estimate the AFR. In the VV mode, the sensor is operated between the lower and a higher voltage (e.g., modulated between the lower and higher voltages and / or switched from one to the other) (hereinafter referred to as...). Fig. 2 described in more detail). Thus, the sensor output in VV mode can be used to estimate one or more of the humidity, the ethanol content in the fuel, and the total water concentration in the exhaust gas, as described in relation to the Fig. 3-7 describes this in detail. By taking into account the ethanol content of the fuel and the ambient humidity, an accurate estimate of the amount of recirculated EGR can be determined. Consequently, EGR control can be improved, fuel economy increased, and NOx emissions reduced.

[0029] Control 12 is in Fig. 1 shown as a microcomputer which includes a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, which in this specific example is shown as a read-only memory chip 106, a random access memory 108, a keep-alive memory 110 and a data bus.In addition to the signals discussed previously, the control unit 12 can receive various signals from sensors coupled to the engine 10, including the mass air flow (MAF) measurement from a mass air flow sensor 120; the engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a profile ignition pickup (PIP) signal from a Hall effect sensor 118 (or another type) coupled to the crankshaft 40; the throttle position (TP) from a throttle position sensor; and the manifold absolute pressure (MAP) signal from sensor 122. The engine speed signal (RPM) can be generated by the control unit 12 from the PIP signal. The control unit 12 receives signals from the aforementioned sensors and uses various actuators. Fig. 1, to adjust the motor operation based on the received signals and instructions stored in a memory of the control unit.

[0030] As an example, the control unit can continue operating the exhaust gas sensor 126 in a non-VV mode at a lower voltage to measure the rich or lean air-fuel ratio (AFR) and adjust fuel injection to the cylinders accordingly to maintain stoichiometric operation. As another example, under selected engine operating conditions (such as an engine without fuel supply and a steady state), the control unit can switch the lambda sensor from non-VV mode to VV mode by increasing the sensor's operating voltage from the lower to a higher voltage. By operating the sensor at a higher voltage (and / or modulating the sensor between the lower and higher voltages), the control unit can monitor the sensor's output under selected engine operating conditions.Based on the output, the control unit can also determine the ethanol content of the fuel, the ambient humidity, and the total water content in the exhaust gas, based on the output of the probe during the selected engine operating conditions (. Fig. 3-7).

[0031] For example, during a fuel cut-off during braking (DFSO), the controller can switch the sensor from non-VV mode to VV mode to estimate the ambient humidity, and then switch the sensor back to non-VV mode once the estimate is complete. The estimated ambient humidity can be stored in memory and later retrieved to estimate the EGR. As another example, the controller can control an EGR valve (such as the EGR valve 142 from Fig. 1) During engine idle, the EGR valve can be closed to prevent the flow of EGR from the exhaust port into the intake port. Additionally, the control unit can operate the lambda sensor in VV mode at a higher voltage to determine the ethanol content in the fuel. Once the estimate is complete, the control unit can store the ethanol content value in memory and reset the sensor to non-VV operating mode by operating it at the lower voltage. The EGR estimation can then continue. Thus, ambient humidity and fuel ethanol content can act as a correction factor used to estimate the amount of EGR.During engine idle, the control unit can actuate the EGR valve when it is time for EGR estimation, opening the EGR valve to recirculate EGR from the exhaust port to the intake port. Additionally, it can operate the lambda sensor in variable-velocity (VV) mode to determine the total water content in the exhaust gas. The control unit can then subtract a correction factor (e.g., a contribution due to ambient humidity and ethanol content in the fuel) from the total water content in the exhaust gas, thus estimating the amount of EGR recirculated from the exhaust port to the intake port. In this way, the control unit can determine the amount of EGR by selectively operating the lambda sensor in VV mode under selected engine operating conditions.

[0032] Computer-readable data can be programmed onto the read-only memory 106 of a storage medium, representing instructions that can be executed by the processor 102 to carry out the procedures described below, as well as other variants that are anticipated but not explicitly listed.

[0033] As described above, shows Fig. 1 only one cylinder of a multi-cylinder engine and each cylinder can likewise contain its own set of inlet / exhaust valves, fuel injectors, spark plugs, etc.

[0034] Next, show Fig. Figure 2 shows a schematic view of an exemplary embodiment of a UEGO probe 200 configured to measure the concentration of oxygen (O2) in the exhaust gas stream. The probe 200 can, for example, be configured as the exhaust gas sensor 126. Fig. 1. The probe 200 comprises a plurality of layers of one or more ceramic materials arranged in a stacked configuration. In the embodiment consisting of Fig. Figure 2 shows five ceramic layers, designated as layers 201, 202, 203, 204, and 205. These layers comprise one or more layers of a solid electrolyte capable of conducting ionic oxygen. Examples of suitable solid electrolytes include zirconia-based materials. In some embodiments, a heating device 207 may also be arranged in thermal communication with the layers to increase their ionic conductivity. While the illustrated UEGO probe is formed from five ceramic layers, it is understood that the UEGO probe may incorporate other suitable numbers of ceramic layers.

[0035] A layer 202 contains a material or materials that create a diffusion path 210. The diffusion path 210 is configured to introduce exhaust gases into a first inner cavity 222 via diffusion. The diffusion path 210 can be configured to allow one or more components of the exhaust gases, including a desired analyte (e.g., O2), to diffuse into the inner cavity 222 at a more limiting rate than the rate at which the analyte can be pumped in or out by pumping an electrode pair 212 and 214. In this way, a stoichiometric amount of O2 can be obtained in the first inner cavity 222.

[0036] The probe 200 further includes a second inner cavity 224 within layer 204, which is separated from the first inner cavity 222 by layer 203. The second inner cavity 224 is configured to maintain a constant oxygen partial pressure according to a stoichiometric condition; for example, the amount of oxygen present in the second inner cavity 224 is equal to that which the exhaust gas would have if the air-fuel ratio were stoichiometric. The oxygen concentration in the second inner cavity 224 is kept constant by a pumping voltage Vcp. The second inner cavity 224 can be referred to here as the reference cell.

[0037] A pair of measuring electrodes 216 and 218 is arranged in communication with the first inner cavity 222 and the reference cell 224. The measuring electrode pair 216 and 218 detects a concentration gradient that can develop between the first inner cavity 222 and the reference cell 224 due to an oxygen concentration in the exhaust gas that exceeds or falls below the stoichiometric amount. A high oxygen concentration can be caused by a lean exhaust gas mixture, while a low oxygen concentration can be caused by a rich mixture.

[0038] A pair of pump electrodes 212 and 214 is arranged in communication with the inner cavity 222 and is configured to electrochemically pump a selected gas component (e.g., O2) through layer 201 from the inner cavity 222 and from the probe 200. Alternatively, the pair of pump electrodes 212 and 214 can be configured to electrochemically pump a selected gas through layer 201 and into the inner cavity 222. The pump electrode pair 212 and 214 can be referred to here as an O2 pump cell.

[0039] The electrodes 212, 214, 216, and 218 can be made of various suitable materials. In some embodiments, the electrodes 212, 214, 216, and 218 can consist at least partially of a material that catalyzes the splitting of molecular oxygen. Examples of such materials include, but are not limited to, electrodes containing platinum and / or silver.

[0040] The process of electrochemically pumping oxygen from or into the inner cavity 222 involves applying a voltage Vp (e.g., a reference voltage) to the pump electrode pair 212 and 214. The pump voltage Vp applied to the O2 pump cells pumps oxygen into or out of the first inner cavity 222 to maintain a stoichiometric amount of oxygen in the cavity pump cell. The resulting pump current Ip is proportional to the oxygen concentration in the exhaust gas. A control system (in non- Fig. (2 shown) generates the pump current signal Ip as a function of the intensity of the applied pump voltage Vp required to maintain a stoichiometric amount within the first inner cavity 222. Thus, a lean mixture causes oxygen to be pumped out of the inner cavity 222, and a rich mixture causes oxygen to be pumped into the inner cavity 222.

[0041] It is understood that the UEGO probe described here is merely one embodiment of a UEGO probe and that other embodiments of UEGO probes may have additional and / or alternative features and / or designs. The oxygen sensor made of Fig. 2. The oxygen sensor can be a variable-voltage sensor configured to operate at a first, lower voltage (e.g., a reference voltage) at which water molecules are not split, and a second, higher voltage (e.g., a reference voltage) at which water molecules are completely split. Thus, the second voltage is higher than the first. Therefore, the lambda sensor can only operate at the lower, first reference voltage (e.g., approximately 450 mV) than a conventional oxygen sensor (e.g., an air-fuel ratio sensor). This lower voltage can be referred to here as the base reference voltage. In other words, the UEGO can be operated as an air-fuel ratio sensor to determine the exhaust air-fuel ratio.

[0042] As detailed below, the UEGO probe can be made of Fig. 2. Advantageously used to estimate the amount of alcohol in the fuel being burned in the engine, as well as ambient humidity and EGR. Under selected engine operating conditions, the sensor can be operated in VV mode, where the sensor operates at the second, higher voltage and / or modulates between the lower, first voltage and the second, higher voltage. In response to the modulation of the lambda sensor voltage between the first and second voltages, a first and second pump current can be generated. The first pump current can indicate the amount of oxygen in a sample gas, while the second pump current can indicate the amount of oxygen in the sample gas plus the amount of oxygen contained in water molecules within the sample gas.The first and second pump streams can be corrected based on an AFR correction, pressure correction and / or ambient humidity correction, and the corrected streams can then be used to determine the ethanol content in the fuel as in . Fig. 7 illustrates how to appreciate.

[0043] The probe can be operated in VV mode to determine ambient humidity. Thus, the ambient humidity (e.g., the absolute humidity of the fresh air surrounding the vehicle) can be determined based on the first and second pump currents (or the first and second correction pump currents). For example, the first pump current can be subtracted from the second pump current to obtain a change in the pump current that indicates the amount of oxygen released from split water molecules (e.g., the amount of water) in the sample gas. This value can be proportional to the ambient humidity.

[0044] The lambda sensor can be operated in VV mode to estimate the total water concentration in the exhaust gas. In exemplary embodiments, the total water concentration in the exhaust gas can be estimated based on a compensation or a rearrangement of the combustion equation (1) shown below: (Gasoline + EtOH) + (Air + Moisture) + EGR = CO2 + H2O + N2, (1) where (gasoline + EtOH) represents the fuel mixture and EGR represents the amount of exhaust gas recirculated from the exhaust port to the intake port. The right-hand side of equation (1) represents combustion products, such as carbon dioxide (CO2), water (H2O), and nitrogen (N2).

[0045] For an engine system that includes 100% gasoline, 0% moisture and no EGR, and additionally includes an air composition, equation (1) can be simplified as shown in equation (2) below: (Gasoline) + (aO2 + bN2) = CO2 + H2O + N2 (2) , where a and b are constants representing the air composition (a = 20.95% and b = 79.05%). Equation (1) can be rewritten as follows: C8H15 + y[z(EGR) + (1 - z)(aO2 + bN2)] -> 8CO2 + u H20 + v N2 (3) , where y represents the amount of air required for stoichiometry, z represents the mole fraction of moisture, and u and v represent the mole fraction of exhaust gas H2O and exhaust gas N2, respectively.

[0046] Equation (2) can further be broken down into chemical compositions and balanced as shown in equation (4) below: C8H15 + y(aO2 + bN2) -> 8CO2 + 7.5 H20 + y*b N2 (4) , where C8H15 represents gasoline and y represents the amount of air required for stoichiometry. Therefore: y*a = 16 + 7.5 (e.g., balancing oxygen in equation (3)), where a = 0.2095. Solving for y yields: y = 112.17, and substituting this value into equation (3) results in EGR as shown in equation (5): EGR = 8 CO2 + 7.5 H2O + 112.12*b N2. (5)

[0047] When EGR is recirculated, the combustion equations can be rewritten as shown below: (C8H15) + y'(z(AGR) + (1 - z)(aO2 + bN2))→ xCO2 + uH2O + vN2, (6) where y' is the mole fraction of the total intake air required for stoichiometry (e.g., EGR + air) and x represents the mole fraction of EtOH. Substituting EGR from equation (5) into equation (6) yields: (C8H15) + y' (z((8)CO2 + (7,5)H2O + (112,17b)N2) + (1 - z)(aO2 + bN2))- xCO2 +uH2O + vN2 (7)

[0048] The values ​​of each of u, x, v and y' can be estimated by balancing hydrogen, carbon, nitrogen and oxygen as shown in equations (8) to (11): u=7.5+(7.5)*y'*z x=8+8*y'*z v=(112,017)*b*y'*z+y'*b−y'*b*z y'=(2X+u) / (23.5z+(1−z)*2*a)

[0049] Using these equations, the final or total generated water is given in mole fraction by equation (12): [H2O]=ux+u+v where u represents the amount of substance of H2O and (x + u + v) represents the total amount of substance.

[0050] In this way, the total water content in the exhaust gas can be estimated by operating the probe in VV mode to determine the amount of H₂O and the total amount of other substances, from which the total water concentration can be estimated. This total water content can include water from ambient humidity, the ethanol content of the fuel, and the volume percentage of EGR recirculated into the system. Therefore, the amount of recirculated EGR can be estimated by subtracting the water content due to the ethanol content in the fuel and the ambient humidity from the total water content. This allows for an accurate estimation of the amount of EGR recirculated into the system.

[0051] The systems from the Fig. 1-2 provide a system comprising: an exhaust gas recirculation (EGR) system comprising an EGR channel coupling an exhaust channel to an intake channel, the EGR channel including an EGR valve, a lambda sensor configured to operate in a variable voltage mode, with a reference voltage of the lambda sensor being adjusted from a lower, first voltage to a higher, second voltage, and coupled to the exhaust channel.Additionally or alternatively, the system includes a controller that contains computer-readable instructions for the following: operating the lambda sensor in variable voltage mode while the EGR valve is closed to generate a first output, opening the EGR valve to circulate EGR, and operating the lambda sensor in variable voltage mode to generate a second output, and setting engine operation based on an estimated amount of EGR, the estimated amount of EGR being determined based on a difference between the second output and the first output (as in the . Fig. (shown in Figures 3-7). Additionally or alternatively, the control unit may also include instructions to generate both the first and second outputs during an engine idle condition. Additionally or alternatively, the control unit may also include instructions to operate the lambda sensor in variable voltage mode during a fuel-free engine condition and to generate a third lambda sensor output and estimate ambient humidity based on the third lambda sensor output and also based on a dry air pump current output from the lambda sensor. Additionally or alternatively, the control unit may also include instructions to estimate the amount of EGR flowing into the engine based on a difference between the second output and both the first and third outputs.Additionally or alternatively, the control may also include instructions for estimating the dry air pump current based on a ratio between a first pump current generated when the lambda probe is operated at the first voltage and a second pump current of the lambda probe generated when the lambda probe is operated at the second voltage, as shown below.

[0052] With reference to Fig. Figure 3 presents a method 300 for adjusting engine operation based on an output from a lambda sensor. Specifically, the lambda sensor can be operated under selected conditions (e.g., engine states without fuel supply and static states) to estimate both the ethanol content in the fuel and the ambient humidity. These estimates can be used as a correction factor and subtracted from a total amount of water estimated in the exhaust gas to determine the amount of exhaust gas recirculation (EGR) from an exhaust port to an intake port. Thus, engine operation can be adjusted based on the EGR estimate.

[0053] As illustrated below, a controller (such as the controller 12 from Fig. 1) Operate the lambda sensor (e.g., by sending one or more electrical control signals to the sensor) to determine the amount of exhaust gas recirculation (EGR) flowing into the engine. This is achieved based on an initial lambda sensor output during operation in VV mode, where a reference voltage from the lambda sensor is adjusted from a lower, first voltage to a higher, second voltage when EGR is flowing, and a second lambda sensor output during operation in VV mode without EGR flow. The control unit can additionally adjust engine operation based on the determined amount of EGR. For example, the control unit can actuate an EGR valve to open, allowing EGR to flow from the exhaust port into the intake port. While the EGR is flowing, the control unit can operate the lambda sensor in VV mode and monitor the sensor's initial output.The control unit can then close the EGR valve to stop the EGR flow from the exhaust port to the intake port. Furthermore, the control unit can operate the sensor in VV mode and monitor the sensor's second output. Additionally, the control unit can determine the ethanol content in the fuel based on the second output.

[0054] The control unit can estimate the lambda sensor reading during a static engine operating condition (e.g., engine idle) and derive an initial water concentration in the engine exhaust gases based on the estimated ethanol content in the fuel. Furthermore, the control unit can estimate ambient humidity based on a third lambda sensor output during operation in VV mode during an engine condition without fuel supply (e.g., a DFSO) and also based on an estimated dry air pump current output from the lambda sensor. Finally, the control unit can estimate a second water concentration in the exhaust gas based on the estimated water humidity.Finally, the control unit can determine the amount of EGR flowing into the engine by subtracting both the first water concentration and the second water concentration from a total water concentration in the exhaust gas, where the total water concentration is determined based on the first output of the lambda sensor, as shown below.

[0055] As described above, a lambda sensor (such as the one in Fig. Lambda sensor 126 shown and the one in Fig. The probe shown (200) is a variable voltage (VV) probe that can be operated at a lower base voltage and a higher target voltage. Thus, the lambda probe can be operated as a conventional air-fuel sensor, with the sensor's reference voltage maintained at a lower base voltage (e.g., 450 mV) at which water and carbon dioxide molecules are not split at the sensor (referred to herein as non-VV operation). Then, under selected conditions, the lambda probe's reference voltage can be increased from the lower base voltage (e.g., the first voltage) to a higher target voltage (e.g., the second voltage) at which water molecules and / or carbon dioxide molecules are split. In one example, the second voltage can be in a range of approximately 900–1,100 mV.Thus, the ethanol content in the fuel, as well as the ambient humidity and total water concentration, can be estimated based on the probe output in VV mode under selected conditions as described below.

[0056] The instructions for executing procedure 300 and the other procedures 400, 500, 600 and 700 contained herein can be executed by a controller based on instructions stored in a working memory of the controller and in conjunction with signals received from sensors of the motor system, such as those described above with reference to the Fig. 1 and Fig. The two sensors described below. The controller can use motor actuators of the motor system to adjust the motor operation according to the procedures described below.

[0057] Procedure 300 begins at 302 with estimating and / or measuring engine operating conditions. Engine operating conditions may include engine speed and / or load, engine temperature, exhaust air-fuel ratio, ambient humidity, ambient temperature, mass airflow, exhaust gas recirculation (EGR) flow, etc. At 304, the procedure involves determining when it is time for EGR estimation. In one example, the control unit may determine that it is time for EGR estimation when a threshold period has elapsed since a previous EGR estimation. In another example, the control unit may determine that it is time for EGR estimation when a refueling event has recently occurred or when a fuel composition has changed during refueling. Generally, EGR is turned off when full power is required (e.g.,during transitional engine operating conditions) and open once a static state is reached. In one example, the control unit can determine that it is time for EGR estimation when the engine returns to a static state after being in a transitional state for a threshold period. In another example, the control unit can determine that it is time for EGR estimation when NOx emissions have reached a threshold level. In some examples, EGR can be recirculated during part-load conditions, such as cruising (e.g., low to medium vehicle speeds), and during full-load conditions (such as while towing a trailer). During such operating conditions, the control unit can determine that it is time for EGR estimation.In some such examples, the amount and flow rate of recirculated EGR can be set based on specific engine or engine operating conditions. During operation under such conditions, the control unit can determine when it is time to estimate the EGR flow. For example, EGR can be stopped or not recirculated when the engine temperature is below a threshold temperature (e.g., during a cold start). Another example is that the EGR flow rate can be set based on humidity. Yet another example is that EGR can be restricted under conditions where water can condense in the CAC (Cooling Acquisition Control Unit). Typically, EGR can be allowed to flow at loads of 0.2 to 0.8. In some systems, EGR can be allowed to flow at very high load conditions to prevent overheating of exhaust components.Thus, the control system can determine that it is time for EGR estimation when one of the aforementioned conditions occurs.

[0058] If it is not time for EGR estimation (e.g., "NO" at 304), procedure 300 continues with 306, with the controller continuing to operate the oxygen sensor in non-VV mode (or reference mode). As described previously, the oxygen sensor can be operated at a lower voltage, and the oxygen sensor output can be used to control the AFR. However, if it is time for EGR estimation (e.g., "YES" at 304), the procedure continues with 308, where the controller determines whether the oxygen sensor can be operated in variable voltage mode (VV mode). For example, under certain conditions where the oxygen sensor is used for air-fuel control (A / F control), the sensor may not be able to operate in VV mode. In such cases, A / F control may take precedence over EGR estimation. However, it is possible that the EGR estimate takes precedence over the A / F control.Some exemplary situations in which EGR estimation takes precedence over A / F control are outlined below.

[0059] During engine operating conditions without fuel supply and in static states, the probe can be operated in VV mode to determine the ambient humidity, the ethanol concentration in the fuel, and the amount of EGR recirculated into the system, based on the estimated water content in the exhaust gas. This allows the EGR to be controlled by actuating the EGR valve and comparing the readings with calibrated EGR sensors at the intake (IAO2, delta pressure sensors, etc.). Thus, all variables (ambient humidity, ethanol content in the fuel, and EGR) would be known. Therefore, it would be possible to maintain the VV operation of the UEGO while still controlling the air-to-fuel ratio. This can be advantageous for several reasons. One reason, for example, is that the UEGO would not need to switch from a low to a high voltage. This can reduce the transition time between low- and high-voltage measurements.Furthermore, this could reduce voltage spikes that would otherwise wear out the lambda sensor (e.g., cause it to blacken). Additionally, continuous high-voltage measurement could enable continuous measurement of all variables affecting the exhaust water concentration. For example, the ethanol content can be continuously measured in this case, as it is one of the variables contributing to the exhaust water concentration. Consequently, the lambda sensor could potentially replace the ethanol fuel sensor in the line.

[0060] Another exemplary situation where EGR measurement may take precedence over A / F ratio measurement is when it is determined that the EGR lift valve needs to be recalibrated (i.e., a sweeping concentration of EGR must be passed through different lift valve angles and the resulting EGR measured on the exhaust oxygen using variable voltages, and the calibration data must then be stored in a table that is stored in the memory of the control unit).

[0061] Another example scenario involves the need to recalibrate an EGR sensor, such as a delta pressure sensor, and the determination that the lambda sensor would provide a more accurate EGR measurement, which could then be used to calibrate the sensor. Initial conditions for this (besides the determination that the EGR valve or sensors need recalibration) would be that the vehicle's AFR is in a steady state, allowing the vehicle to maintain this AFR while the lambda sensor is put into an open circuit to calibrate the EGR valve or sensor.

[0062] As previously described, VV mode involves adjusting the reference voltage (also referred to herein as the pump voltage) of the oxygen sensor from a lower base voltage (e.g., approximately 450 mV) to a higher target voltage at which the water molecules are split at the sensor. In some examples, operating in VV mode may involve continuously modulating the reference voltage between the base voltage (e.g., the first voltage) and the target voltage (e.g., the second voltage). In some examples, continuously operating the oxygen sensor in VV mode, and especially at the higher, second voltage, may wear out the sensor over time. Therefore, it may be advantageous to reduce the duration for which the sensor is operated in VV mode. In one example, the sensor may only be operated in VV mode after a certain period has elapsed since a previous VV operating period.In another example, the sensor can only be operated in VV mode if the total operating time in VV mode for an engine's service life is below an upper threshold. In yet another example, the sensor can be operated in VV mode based on a duration (e.g., an elapsed period) since a previous measurement. The sensor can also be switched off if a total threshold time has elapsed since a measurement. In a further embodiment, continuous operation of the oxygen sensor at the higher, second voltage may not cause sensor wear if the gas composition and the second voltage are within certain threshold ranges that reduce wear.In this embodiment, the sensor can operate in VV mode by default, and the procedure can be continued with 312 if the gas composition and the second voltage of the sensor are kept within the threshold ranges.

[0063] In 312, the procedure involves determining a dry air pump flow rate (Ip) by operating the sensor in VV mode, as described in Fig. 4 illustrates. Now, with reference to Fig. 4 a flow diagram is shown, which describes a method 400 for determining a dry air pump flow or a dry air oxygen measurement with an oxygen sensor, such as the oxygen sensor 200, which was previously described in relation to Fig. 2 is illustrated. In particular, Method 400 determines the dry air pump current based on various voltages (e.g., reference voltages) applied to a pump cell of the oxygen sensor under selected engine operating conditions. The resulting dry air pump current can then be used together with subsequent oxygen sensor outputs during additional selected operating conditions to determine an ambient humidity ( Fig. 5-6).

[0064] In step 410 of procedure 400, engine operating conditions are determined. Engine operating conditions may include, among other things, an air-fuel ratio, an amount of EGR entering the combustion chambers, and fuel supply conditions. Once the engine operating conditions have been determined, procedure 400 continues with step 412, which determines whether selected conditions are met. The selected conditions may include, for example, engine conditions without fuel supply. Conditions without fuel supply include vehicle braking conditions and engine operating conditions in which the fuel supply is interrupted, but the engine continues to rotate and at least one intake valve and one exhaust valve are operating; thus, air flows through one or more of the cylinders, but no fuel is injected into the cylinders.Under conditions without fuel supply, no combustion takes place, and ambient air can move through the cylinder from the intake to the exhaust. In this way, a sensor, such as a lambda sensor, can detect ambient air, allowing measurements such as ambient humidity to be taken.

[0065] As noted, engine states without fuel supply can include, for example, fuel shut-off during braking (DFSO). DFSO occurs in response to the operator pedal (e.g., in response to a release by the driver when the vehicle deceleration exceeds a threshold or duration without operator pedal application). DFSO conditions can occur repeatedly during a driving cycle, thus generating multiple ambient humidity readings during the cycle, such as during each DFSO event. Therefore, the fuel type can be accurately identified based on the amount of water in the exhaust gas, despite humidity fluctuations between driving cycles or even within the same cycle.

[0066] Furthermore, the selected conditions at 412 may additionally include after an engine start or a period of engine operation (e.g., after a number of miles traveled, after a period of engine operation, or after a number of engine cycles). The selected conditions at 412 may, for example, include after an engine start (or after a period of engine operation) during engine conditions without fuel supply (e.g., when the fuel supply has been disabled as described above). In this way, determining the dry air oxygen measurement (or dry air pump flow), as described in more detail below, can occur only periodically after each engine start or after a period of engine operation, when the flow of hydrocarbons past the oxygen sensor decreases.In this way, a more accurate sensor measurement can be obtained while reducing the time voltage of operating the oxygen sensor in VV mode.

[0067] Continuing with Fig. 4. Procedure 400 continues with 413 if it is determined that the selected operating conditions are not met (e.g., "NO" at 412) in order to continue the current oxygen sensor operation (with the current pump voltage, such as the base voltage or the lower, first reference voltage) and to determine an ambient humidity based on a previously determined dry air pump current (e.g., a dry air oxygen measurement). After each execution of procedure 400 in which a dry air oxygen measurement is determined, the resulting value from the dry air oxygen measurement (e.g., the pump current) can be stored, for example, in a memory of the controller. Then, for example, during an ambient humidity measurement, the most recently stored dry air pump current can be looked up in the controller's memory and used to determine the ambient humidity.The procedure described in 413 may involve not operating the oxygen sensor in VV mode and instead continuing to operate the oxygen sensor with a lower, first reference voltage, also referred to here as the base reference voltage. Operating the oxygen sensor with the base reference voltage may result in less sensor wear than operating the oxygen sensor with the higher, second reference voltage.

[0068] Conversely, procedure 400 at 412 continues with 414 if it has been determined that the selected operating conditions are met (e.g., "YES" at 412), applying a first pump voltage (V1) (e.g., the first reference voltage) to the oxygen pump cell of the oxygen sensor and receiving a first pump current (Ip1). The first pump voltage can be such that oxygen is pumped from the cell, but low enough that oxygen compounds, such as H₂O (e.g., water), are not split (e.g., V1 = about 450 mV). At the first pump voltage, for example, the oxygen sensor may not split water molecules. Applying the first voltage generates an output from the probe in the form of the first pump current (Ip1), which indicates the amount of oxygen in the sample gas.In this example, the amount of oxygen can correspond to the amount of oxygen in the fresh air surrounding the vehicle or to a wet air oxygen measurement, since the vehicle is in one of the selected states (such as an engine state without fuel supply).

[0069] Once the amount of oxygen has been determined, procedure 400 continues with 416, where a second pump voltage (V2) (e.g., the reference voltage) is applied to the oxygen pump cell of the oxygen sensor, and a second pump current (Ip2) is received. The second voltage may be higher than the first voltage applied to the sensor. In particular, the second voltage may be high enough to split a desired oxygen compound. For example, the second voltage may be high enough to split all H2O molecules into hydrogen and oxygen (e.g., V2 = about 1.1 V). Applying the second voltage generates the second pump current (I2), which indicates the amount of oxygen and water in the sample gas. It is understood that the term "water" in the "amount of oxygen and water," as used herein, refers to the amount of oxygen from the split H2O molecules in the sample gas.

[0070] In a specific example, the second voltage (e.g., the second reference voltage) could be 1080 mV, at which value the water in the air is completely split (e.g., 100% of the water in the air is split at 1080 mV). This second voltage could be higher than a third, intermediate voltage, at which water in the air is partially split (e.g., 40% of the water in the air is split). In one example, the third, intermediate voltage could be around 920 mV. In another example, the third, intermediate voltage could be around 950 mV. As an example, the sensor output at 920 mV could correspond to a dry air measurement under a range of humidity conditions. The sensor output at 1.1 V can correspond to a humid air measurement where all the water in the air has been split at the sensor, and the sensor output at 450 mV can correspond to a humid air measurement where no water in the air has been split.Accordingly, a dry air oxygen measurement can be obtained by a ratio of oxygen sensor outputs when the oxygen sensor is operated at 450 mV and 1.1 V. In an alternative embodiment, the dry air oxygen measurement can be obtained by a ratio of the oxygen sensor output when the oxygen sensor is operated at a voltage below 0.92 V, at which water is not split (e.g., not even partially split), and at a voltage above 0.92 V, a value at which water is completely split (e.g., 100%).

[0071] At 418, the dry air pump current is determined based on the first and second pump currents. For example, as described above, operating the sensor at 450 mV (or a similar voltage at which no water is split at the sensor) can result in a lower pump current and a lower oxygen reading, while operating the sensor at 1080 mV (or a similar voltage at which all the water is split at the sensor) can result in a higher pump current and a higher oxygen reading. A dry air pump current that indicates a dry air oxygen reading can then be estimated from a ratio between the lower, first pump current and the higher, second pump current. For example, a sum of 40% of the higher, second pump current and 60% of the lower, first pump current can be essentially equal to the dry air pump current and the oxygen reading.In an alternative example, different proportions of the higher and lower pump currents can be added to determine the dry air pump current. For example, if the higher and lower voltages differ by 450 mV and 1080 mV respectively, the corresponding proportions used to determine the ratio between the higher and lower pump currents can differ proportionally.

[0072] The estimated dry air pump current, based on the ratio between the higher and lower pump currents (e.g., a higher and lower oxygen sensor output corresponding to the higher and lower voltages), can then be used to determine an ambient humidity estimate at step 316 of procedure 300. For example, procedure 400 at step 420 may involve storing the determined dry air pump current value in a controller memory. The controller can then, during the procedure, Fig. 3 (e.g., at step 316) either generate the dry air pump flow by executing procedure 400 as described above, or alternatively, the controller can simply look up the most recent stored dry air pump flow to make an ambient humidity estimate as described in relation to the Fig. The procedure described in sections 3 and 5-6 can be further refined. Additionally, procedure 420 can involve updating a previously stored dry air pump flow with a new dry air flow in the controller's memory. The stored dry air flow can be updated, for example, after each engine start.

[0073] With renewed reference to Fig. 3 includes the procedure 300 at 312 determining the dry air flow Ip or retrieving the most recent dry air value Ip stored in the memory (as in Fig. (illustrated in Figure 4). Method 300 then continues with 314, where an exhaust water concentration (W1) is determined from (e.g., due to) ambient humidity and the ethanol content in the fuel. Here, both the ambient humidity and the ethanol content in the fuel can contribute a correction factor, which is used to determine the exhaust water from ambient humidity and the ethanol content in the fuel, W1.

[0074] As previously described, the controller can operate the lambda sensor in VV mode to determine the exhaust water concentration W1. Estimating the exhaust water concentration W1 involves estimating the ambient humidity with the engine running without fuel at 316 and further estimating the ethanol concentration in the fuel in a static state at 318. Specifically, the controller can operate the lambda sensor in VV mode at 316 to determine the ambient humidity using the dry air Ip estimated at 312, as shown in Fig. 5 illustrates.

[0075] In procedure 316, this involves operating the oxygen sensor in VV mode to determine a correction factor based on the sensor's second voltage. For example, the determined correction factor might include an amount or proportion of water in the exhaust gas due to ambient humidity, estimated based on an output from the oxygen sensor while operating in VV mode in a no-fuel engine condition (such as fuel cut-off during braking) and based on a dry air pump current output from the oxygen sensor. In short, the dry air pump current can be estimated based on an output from the oxygen sensor while operating in VV mode during one or more instances of an engine start, a number of miles traveled, a time period, a number of engine cycles, and the no-fuel engine condition.

[0076] In the 318 procedure, the process additionally involves operating the lambda sensor in VV mode to determine the correction factor based on the sensor's second voltage. Here, the determined correction factor can include an amount or proportion of water in the exhaust gas due to an ethanol content in the fuel, while no EGR is flowing, as in Fig. Figure 7 illustrates this. Thus, the ethanol content in the fuel can be estimated based on an output from the lambda sensor while the lambda sensor is operating in VV mode during a steady-state engine operating condition, when the EGR is switched off and no ethanol is circulating from an exhaust port to an intake port. Here, the steady-state engine operating condition can include an engine idle condition.

[0077] As outlined below, procedures 500, 600, and 700 can be included within procedure 300. Thus, the order in which procedures 500, 600, and 700 are performed within procedure 300 can be selected by the controller based on one or more of the current engine operating conditions and the ability to operate the sensor in VV mode. In some examples, the controller may choose not to perform procedure 700 if the engine is in a no-fuel state (e.g., a DFSO); instead, procedures 500 and 600 can be performed to estimate the ambient humidity and store the generated ambient humidity value in memory.However, if the engine is in a steady state, the control unit can choose not to perform procedures 500 and 600; instead, the control unit can perform procedure 700 to estimate the ethanol concentration in the fuel. In both cases, the generated values ​​(ambient humidity or ethanol content in the fuel) can be used to determine an EGR quantity. Fig. Items 5-7 are described together below.

[0078] With reference to Fig. 5 describes an exemplary method 500 for estimating ambient humidity using a VV lambda probe (such as the one in Fig. Lambda sensor 126 shown in 1 and the one in Fig. The procedure is shown in Figure 200. It begins with 502 by determining if it is time for an ambient humidity estimate. Thus, the controller can determine that it is time for the ambient humidity estimate, and the procedure can continue with 504 if the engine is running under no-fuel conditions. In another example, the procedure 500 can be performed after a duration, such as a period of engine operation, a series of engine cycles, a duration of vehicle movement, or a distance traveled by vehicle. In yet another example, the procedure 500 can be performed when the engine is started. If it is not time for the ambient humidity estimate (e.g., "NO" at 502), the procedure continues with 503 to not estimate ambient humidity, and the procedure ends.If an ambient humidity measurement is requested by another control routine, the controller can look up a previously stored ambient humidity estimate and returns to step 318 of procedure 300. Continued with... Fig. Procedure 500 at 504 includes determining whether an incoming transmission shift is occurring. An incoming transmission shift can be predicted based on one or more of the following: the fact that a shift request flag has been set, the observation of one or more operator pedals, and / or vehicle acceleration. During transmission shifts following non-fueling conditions (e.g., fuel cut-off during braking), humidity sensing using the oxygen sensor may not be possible due to the need to reduce the load during the transmission shift (and humidity sensing using the oxygen sensor may involve throttle opening to reduce PCV noise). If a transmission shift is predicted at 504 (e.g.,If “YES” is answered in section 504), the procedure is continued with section 506 to determine the ambient humidity using an alternative method, as in . Fig. 6 shown.

[0079] If no incoming transmission shift is predicted at 504 (e.g., "NO" at 504), procedure 500 continues with 508 to adjust the intake throttle (e.g., the one in Fig. 1 throttle 62) shown, to open in order to further reduce the amount of hydrocarbons detected at the lambda sensor (e.g. the one in Fig. 1 Lambda sensor 126 shown and / or the one in Fig. (200 shown). Opening the throttle can, for example, reduce the amount of hydrocarbons from a PCV that escape via the exhaust. In particular, a large intake manifold vacuum is generated, which can draw in hydrocarbons from the positive crankcase ventilation (PCV) when the intake throttle is closed during the engine's no-fuel condition. Thus, the vacuum can be strong enough to draw PCV hydrocarbons past the piston rings, even if one PCV channel is closed during DFSO. The PCV flow that is drawn in can be increased in an older engine due to PCV gas leakage past the piston rings and valves. The ingested hydrocarbons can affect the lambda sensor output and interfere with humidity readings.In particular, the hydrocarbon effect leads to a probe output that overestimates the ambient humidity.

[0080] At step 510, the procedure may include determining whether the lambda sensor should be operated in a variable voltage (VV) mode. In one example, step 510 may be considered redundant if the controller has reached step 510 after performing procedure 300, since a similar check is performed at step 308 of procedure 300, and the controller can skip the check at step 510 and proceed to step 512 via step 518. However, if the controller performs procedure 500 independently of procedure 300, the controller may check whether the sensor can be operated in VV mode at step 510. As described above, VV mode involves adjusting the reference voltage (also referred to herein as the pump voltage) of the oxygen sensor from a lower base voltage (e.g., about 450 mV) to a higher target voltage at which the water molecules at the sensor are split.In some examples, operation in VV mode may involve continuous modulation of the reference voltage between the base voltage (e.g., the first voltage) and the target voltage (e.g., the second voltage). In some examples, continuous operation of the oxygen sensor in VV mode, and especially with the higher, second voltage, may wear out the sensor over time. Therefore, it may be advantageous to reduce the duration for which the sensor operates in VV mode. In one example, the sensor may only be operated in VV mode if a certain duration has elapsed since a previous VV operating period. In another example, the sensor may only be operated in VV mode if the total duration of operation in VV mode for an engine operating period is below an upper threshold. In yet another example, the sensor may be operated based on a duration (e.g.,The sensor can be operated in VV mode for a period of time since a previous measurement. The sensor can also be switched off if a total threshold time has elapsed since a measurement. In another embodiment, continuous operation of the oxygen sensor at the higher, second voltage may not cause wear on the sensor if the gas composition and the second voltage are within certain threshold ranges that reduce wear. In this embodiment, the sensor can operate in VV mode by default, and the procedure can be continued with 512 if the gas composition and the second voltage of the sensor are kept within the threshold ranges.

[0081] If the controller determines that it is capable of operating the lambda probe in VV mode, the procedure continues at 512 to modulate the lambda probe's reference voltage between the first voltage (V1) and the second voltage (V2). The procedure at 512 involves, for example, first applying the first voltage (V1) to the lambda probe's oxygen pump cell and receiving the first pump current (Ip1) at 514. The first reference voltage can be such that oxygen is pumped from the cell, but low enough that oxygen compounds, such as H₂O (e.g., water), are not split (e.g., V1 = approximately 450 mV). Applying the first voltage generates an output from the probe in the form of the first pump current (Ip1), which indicates the amount of oxygen in the sample gas.In this example, the amount of oxygen can correspond to the amount of oxygen in the fresh air surrounding the vehicle, since the vehicle is in an engine-less state. The procedure at 512 further involves, at 516, applying the second voltage (V2) to the oxygen pump cell of the probe and receiving a second pump current (Ip2). The second voltage can be higher than the first voltage applied to the sensor. In particular, the second voltage can have a value high enough to split a desired oxygen compound. For example, the second voltage can be high enough to split H2O molecules into hydrogen and oxygen (e.g., V2 = about 1.1 V). Applying the second voltage generates the second pump current (I2), which indicates the amount of oxygen and water in the sample gas.It is understood that the term "water" in the "amount of oxygen and water," as used herein, refers to the amount of oxygen from the split H₂O molecules in the sample gas. In some examples, the first pumping stream and the second pumping stream can be corrected using a determined correction factor for the air-fuel ratio.

[0082] The ambient humidity (e.g., the absolute humidity of the fresh air surrounding the vehicle) can be determined based on the first and second pump streams (or the first and second pump stream corrections) at 518 of Routine 500. For example, the first pump stream can be subtracted from the second pump stream to obtain a change in pump stream that indicates the amount of oxygen released from split water molecules (e.g., the amount of water) in the sample gas. This value can be proportional to the ambient humidity.

[0083] With further reference to 510, if operation of the lambda probe in VV mode is not desired, the method may instead involve determining an ambient humidity based on an output of the lambda probe at the first voltage and a dry air pump current value. In particular, the method in 520 involves determining a dry air pump current. A method for determining a dry air pump current of the lambda probe is described in Fig. Figure 4 illustrates this. The method can involve operating the lambda probe with a first, lower voltage to obtain an initial output indicating a wet-air oxygen measurement. The probe can then be operated with a second, higher voltage to obtain a second output indicating a wet-air oxygen measurement, where all the moisture in the air has been split at the oxygen sensor. An intermediate voltage between the first, lower voltage and the second, higher voltage can produce an oxygen sensor output indicating a dry-air oxygen measurement, where only partial moisture splitting occurs. A dry-air oxygen measurement can then be estimated by the ratio between the first and second outputs. In this way, the dry-air oxygen measurement can be determined by operating the oxygen sensor in VV mode.At 520, the controller can look up the most recently stored value of the dry air pump flow (determined by routine 800) in order to use it at 520.

[0084] The procedure continues with 522 to apply the first, lower reference voltage (e.g., a base voltage V1) to the lambda probe, and a pump current (IpB) is received. Thus, the procedure in 522 involves not operating the oxygen sensor in VV mode and instead maintaining the sensor's reference voltage at a lower base level, thereby reducing oxygen sensor wear. In other words, the procedure in 522 involves non-modulating the oxygen sensor's reference voltage between a lower first voltage and a higher second voltage. The resulting pump current can indicate the amount of oxygen in the sample gas.

[0085] The procedure then continues with 524 to determine the ambient humidity based on IpB (the pump current determined at 522 during non-VV sensor operation) and the dry air pump current determined during procedure 400 (and looked up at 510). The amount of oxygen reduction due to the dilution effect of the ambient humidity can then be determined based on the difference between the dry air flow and the pump current IpB determined or retrieved at 522. By multiplying by a conversion factor, this difference can then be converted from a pump current to a humidity fraction. In this way, the ambient humidity can be determined with continuous operation of the oxygen sensor in VV mode by comparing the output of the oxygen sensor, operating at the basic reference voltage in non-VV mode, to a stored dry air pump current value.The ambient humidity value determined at 514 can then be used to correct the water estimate of procedure 300 at 314 and / or can be stored in the controller's memory. In other examples, motor operation can be adjusted based on the determined ambient humidity.

[0086] With renewed reference to 504 of Procedure 500, the procedure continues with 506 to determine the ambient humidity using an alternative method, as described in Fig. Figure 6 shows when a gear shift is predicted at 504. With Fig. Continuing from paragraph 6 of 506, method 600 begins with 602 by determining whether an ambient humidity sensor is available. In one embodiment, for example, the motor may include a humidity sensor, such as the one described in Fig. 1 humidity sensor 121 shown, to directly measure the ambient humidity (e.g. by measuring the moisture content of the incoming intake air).

[0087] If no ambient humidity sensor is available (e.g., the engine does not include a dedicated ambient humidity sensor), the procedure continues with 612 to estimate the ambient humidity based on an ambient air temperature. For example, the ambient humidity can be estimated based on the ambient air temperature, and a saturation vapor pressure can be estimated using an assumption of 50% relative humidity. Similar to the procedure in 606, an equivalent pump current can be determined in 614 based on the humidity estimate. The procedure then continues with 608 as described above. Estimating the ambient humidity based on the ambient air temperature may not be as accurate as using a dedicated humidity sensor or the variable voltage lambda sensor.Thus, the control system can determine the humidity, preferably based on outputs from the VV lambda probe, as described in more detail below.

[0088] Conversely, the procedure continues with 604 to measure the ambient humidity using the humidity sensor if an ambient humidity sensor is present and available for use in 602. In 606, the procedure involves determining an equivalent pump current Ip for an oxygen sensor based on the humidity measurement and a current voltage setting value of the lambda probe, which is used to determine the fuel alcohol ( Fig. 7) is used. For example, the output of the humidity sensor can be used as an input to a lookup table stored in the controller's memory. The lookup table can relate humidity measurements (e.g., raw humidity readings from the humidity sensor) and an oxygen sensor voltage to the pump current. In one example, the resulting pump current can be used as the humidity correction for the water estimation for determining ethanol in the fuel. Fig. 7. The procedure can then be continued with 608 to refine the moisture correction determined at 606 based on an available moisture estimate at variable voltage, as further described below with reference to Fig. 5 described in more detail. For example, humidity estimates using the variable voltage lambda sensor during no-fuel conditions, when no gear shift is expected, can be stored in the control unit's memory and used to further refine the humidity correction.

[0089] In 610, the procedure involves correcting the estimate of water in the exhaust gas to determine the fuel alcohol based on the determined moisture correction. Thus, the procedure in 610 can involve subtracting the equivalent pump current determined in 606 (or refined in 608) from the change in the pump current measurement. In this way, the ambient humidity can be subtracted from the estimate of total water in the exhaust gas before determining the proportion of ethanol in the fuel.

[0090] Continuing with Fig. Figure 7 shows a flowchart illustrating an estimation method 700 for a lambda sensor, such as the one in Fig. 2 UEGO 200 shown, illustrated. In particular, in method 700, a quantity of alcohol in the fuel injected into the engine is determined based on voltages applied to a pump cell of the probe during selected engine fuel supply conditions and further based on a variety of correction factors, as in relation to the Fig. 3-6 described, calculated, determined (e.g. estimation of the ethanol content in the fuel).

[0091] In step 710 of procedure 700, engine operating conditions are determined. Engine operating conditions can include, among other things, an air-fuel ratio, the amount of EGR entering the combustion chambers, and fuel supply conditions, etc.

[0092] Once the engine operating conditions have been determined, procedure 700 continues with 712, which determines whether the engine is in a no-fuel condition. No-fuel conditions include vehicle braking conditions and engine operating conditions where the fuel supply is interrupted, but the engine continues to rotate and at least one intake and one exhaust valve are operating; thus, air flows through one or more of the cylinders, but no fuel is injected into the cylinders. In no-fuel conditions, no combustion takes place, and ambient air can move through the cylinder from the intake to the exhaust. In this way, a sensor, such as a UEGO probe (e.g., a lambda sensor), can receive ambient air on which measurements, such as ambient humidity, can be taken.

[0093] As noted, engine states without fuel supply can include, for example, fuel cut-off during braking (DFSO). DFSO occurs in response to the operator pedal (e.g., in response to a release by the driver when the vehicle acceleration exceeds a threshold). DFSO conditions can occur repeatedly during a driving cycle, thus generating multiple ambient humidity readings during the cycle, such as during each DFSO event. Therefore, the fuel type can be accurately identified based on the amount of water in the exhaust gas, despite humidity fluctuations between driving cycles or even within the same cycle.

[0094] Continuing with Fig. 7. Procedure 700 is continued with 718 to determine ambient humidity using the procedures from the Fig. 5-6, as described in more detail below, to determine when it has been determined that the engine is in a state without fuel supply, such as a DFSO. If it is determined that the engine is not in a state without power supply, procedure 700 from Fig. Alternatively, step 720 continues, determining whether probe-based air-fuel ratio feedback control or probe-based alcohol detection is desired or should be performed. The selection can be based on operating conditions, such as the time elapsed since the last alcohol determination or whether closed-loop control is activated. For example, if air-fuel ratio feedback control is disabled, the procedure can continue to determine the alcohol content, whereas if air-fuel ratio feedback control is requested or activated, the procedure can still perform such feedback control (without determining the alcohol content).For example, if step 316 of procedure 300 requires VV (variable voltage) measurement of the ethanol content in the fuel, fuel alcohol measurement can be selected via feedback control of the air-fuel ratio. If it is determined that feedback control is desired, procedure 700 continues with step 736, and the probe is operated as an oxygen sensor (e.g., an O2 sensor) in non-VV mode (e.g., with a lower base voltage) to determine an oxygen concentration and / or an air-fuel ratio of the exhaust gas, and the procedure ends.

[0095] If alcohol detection is desired, procedure 700 continues with 721, which determines whether positive crankcase ventilation (PCV) is at a desired level. For example, a PCV level may be based on engine speed and / or turbocharger operation (boosted or non-boosted operation). If the engine speed is high, for instance, an increased PCV flow may be estimated. Other exemplary conditions include increased manifold vacuum, increased crankcase pressure, high ambient conditions, combinations thereof, etc. If the engine speed is relatively low, the PCV level may also be based on whether the turbocharger is engaged and the engine is boosted. If the engine is in a non-boosted state, the PCV flow may be elevated. Conversely, the flow from the PCV valve may be sufficiently low if the engine is boosted.If at 721 it is determined that the amount of PCV is above a desired level (e.g. the PCV current is high), procedure 700 continues with 736 and the probe is operated as an oxygen sensor (in non-VV mode) to determine, for example, an oxygen concentration of the exhaust gas for air control in the fuel, and the procedure ends.

[0096] On the other hand, procedure 700 continues with 722, which determines whether the exhaust gas recirculation (EGR) valve is open when the PCV is at a desired level (e.g., the PCV flow is low). If it is determined that the EGR valve is open, procedure 700 continues with 723, and the EGR valve is closed. Once the EGR valve is closed at 723, or if it is determined at 722 that the EGR valve is closed, and thus the amount of EGR entering the combustion chamber is essentially zero, procedure 700 continues with 724, which determines whether the fuel vapor purge valve is open.

[0097] If it is determined that the fuel vapor purge valve is open, procedure 700 is continued with 725 and the fuel vapor purge valve is closed. Fuel vapor stored in the fuel vapor reservoir may have an alcohol content that differs from the fuel currently in the fuel tank. Thus, fuel vapor entering the combustion chamber may affect the amount of alcohol detected by the lambda sensor (e.g., the UEGO), leading to an inaccurate estimate.

[0098] Once the fuel vapor purge valve is closed at 725, or if it is determined at 724 that the fuel vapor purge valve is closed, procedure 700 continues with 726, where a first pump voltage (V1) (e.g., also referred to herein as the reference voltage) is applied to the exhaust gas sensor and a first pump current (Ip1) is received. The first pump voltage can pump oxygen from the oxygen pump cell but may be of a value low enough not to split water molecules (e.g., H2O molecules) in the pump cell (e.g., V1 = about 450 mV). In some examples, the first pump voltage applied to the probe at 726 may be the same as the first pump voltage applied during operation in non-VV mode. When the first voltage is applied to the pump cell, the first pump current (Ip1) is generated.In this example, the first pumping stream can indicate a significant amount of oxygen in the exhaust gas, as fuel is injected into the engine and combustion is taking place.

[0099] In procedure 700, step 728, a second pump voltage (V2) (also referred to herein as the second reference voltage) is applied to the exhaust gas sensor's pump cell, and a second pump current (Ip2) is received. The second pump voltage can be higher than the first pump voltage, and the second voltage can be high enough to split oxygen compounds, such as water molecules. Applying the second pump voltage across the oxygen pump cell generates the second pump current (Ip2). The second pump current can indicate the amount of oxygen and water in the sample gas (e.g., oxygen already present in the sample gas plus oxygen from water molecules that are split when the second pump voltage is applied).

[0100] If necessary, the first pumping flow and the second pumping flow at 730 can be corrected with a determined air-fuel ratio correction factor. The determined air-fuel ratio correction factor can, for example, be applied at 720 of procedure 700, which is subsequently described in relation to Fig. The first pump flow and the second pump flow can also be corrected for pressure and the water vapor environment at 730, if necessary.

[0101] Continuing with 731, the procedure involves correcting the change in pump current (e.g., the difference between the first and second pump currents) between the two voltages based on ambient humidity. For example, the ambient humidity can be subtracted from the change in pump current, indicating a total amount of water in the exhaust gas (including moisture). In one example, the ambient humidity can be determined based on an output from the lambda sensor during no-power conditions. In another example, the ambient humidity can be determined using an alternative procedure based on engine operating conditions. The procedure at 731 can involve immediately determining the ambient humidity or looking up the most recent ambient humidity estimate in the controller's memory. The procedure for determining the ambient humidity is described in relation to the Fig. 5-6 described.

[0102] Once the first and second pump streams have been generated and corrected based on the various determined correction factors, a quantity of water W1 in the sample gas can be extracted at 732 of procedure 700. Fig. 7. For example, the first pumping flow can be subtracted from the second pumping flow and then corrected on the basis of the air-fuel ratio correction factor, the pressure correction factor and / or the ambient humidity to determine a value that corresponds to a quantity of water.

[0103] Finally, the amount of alcohol in the fuel (referred to herein as the ethanol content in the fuel) can be identified at 734. For example, the amount of water in the exhaust gas can be proportional to the amount of alcohol (e.g., the proportion of ethanol) in the fuel injected into the engine. In some embodiments, the computer-readable storage medium of the control system, which receives communication from the probe, can contain instructions for identifying the amount of alcohol. For example, a relationship between water after combustion (e.g., the proportion of water in the exhaust gas) and the proportion of ethanol in the fuel can be stored on the computer-readable storage medium, for example, in the form of a lookup table. As the amount of ethanol in the fuel increases, the amount of water in the exhaust gas increases.

[0104] Accordingly, the amount of water in the exhaust gas can be determined based on lambda sensor outputs (e.g., pump currents) generated by two different voltages sequentially applied to the exhaust gas sensor's oxygen pump cell during engine power delivery conditions, and the various correction factors described above. In this way, an accurate indication of the amount of alcohol (e.g., ethanol content) in the fuel can be obtained.

[0105] With renewed reference to Fig. 3. The ambient humidity values ​​( Fig. 5-6) and the ethanol concentration in the fuel ( Fig. 7), which are generated by the controller, are used to determine the water concentration W1 at 314. Next, the procedure involves operating the probe in VV mode at 300 and 320 to determine a water concentration W2 (e.g., a total water concentration) in the exhaust gas with the EGR flowing. In particular, the controller can operate the EGR valve (e.g., the one in Fig. 1. Open the EGR valve (142) shown to allow the EGR to flow from the exhaust port (e.g., the exhaust port 48). Fig. 1) into the intake port (e.g., intake port 44 from Fig. 1) to be recirculated. Accordingly, the lambda sensor output is obtained while EGR flows from the exhaust port to the intake port, with the lambda sensor located upstream of the point where the EGR port is coupled to the exhaust port in the exhaust port. Furthermore, the control unit can operate the lambda sensor in VV mode to determine the water concentration W2 of the exhaust gas. Here, the water concentration W2 can be a total water concentration in the exhaust gas, which further includes water from both the ambient humidity and the ethanol content in the fuel, as well as the water originating from the EGR recirculation into the system (W). Mathematically, the total water concentration W2 can be described by the following equation (13): W2=W1+W, where W1 represents the water concentration from both the ambient humidity and the ethanol content in the fuel. Thus, the water contribution from both the ambient humidity and the ethanol content in the fuel can be considered a correction factor, which is controlled by operating the probe in VV mode by performing the steps specified in the Fig. The procedures illustrated in 5-7 are determined under selected engine operating conditions.

[0106] Therefore, W2 can be synonymously referred to as the correction factor. In particular, the ambient humidity can be determined using the dry air pump flow rate ( Fig. 4) can be estimated in engine states without fuel supply (e.g. the DFSO) and the ethanol content in the fuel can be estimated during an engine idle state (e.g. at idle).

[0107] Next, at 322, the water (W) originating from the EGR recirculation into the system is determined by subtracting the correction factor from the total water concentration W2 in the exhaust gas, as shown in equation (14): W=W2−W1

[0108] Procedure 300 involves estimating the EGR quantity in the exhaust gas based on the difference W in 324. This procedure includes determining the total water concentration in the exhaust gas based on the lambda sensor output, determining a water concentration in the exhaust gas due to moisture and the ethanol content in the fuel based on the determined correction factor, and estimating the EGR quantity by subtracting the water concentration in the exhaust gas due to moisture and the ethanol content in the fuel from the total water concentration. Furthermore, the controller can store the EGR quantity estimated using equation (14) in a memory. In some examples, the controller can adjust the EGR quantity based on additional factors. For example, when measuring the exhaust gas composition using VV, the controller can consider how lean or rich the AFR is and adjust the EGR estimate accordingly.In some other examples, the transport delay, from the time the EGR recirculation valve opens until the lambda sensor detects the additional water contribution, can represent an additional factor that can be used to identify the water contribution from EGR. In such examples, the procedure may involve comparing the EGR contribution before and after it has been detected by the lambda sensor.

[0109] In this way, the control unit can operate the lambda probe in VV mode to determine both the ambient humidity and the ethanol concentration in the fuel, as well as the amount of EGR that is recirculated into the system, based on the estimated water content in the exhaust gas.

[0110] Therefore, this estimate is only feasible if the lambda sensor is operated in VV mode (as checked in 308). However, if it is not possible to operate the sensor in VV mode (e.g., "NO" in 308), procedure 300 continues with 310. Procedure 300 involves determining the EGR using alternative methods in 310.

[0111] In one example, the control unit can retrieve the most recent ambient humidity, ethanol content in the fuel, and total water concentration in the fuel from memory and use these values ​​to estimate the amount of EGR. In another example, the control unit can use outputs from the various sensors connected to the engine system to estimate the amount of EGR recirculated from the exhaust port to the intake port. Examples of sensors include, but are not limited to, temperature sensors, pressure sensors, flow sensors, position sensors, and gas composition sensors.

[0112] Regardless of whether the amount of EGR is determined by operating the lambda probe in VV mode (by 324 at 312) or by alternative methods (310), the procedure 300 with 326 is continued once the control has determined the amount of EGR.

[0113] In procedure 326, procedure 300 involves adjusting engine operation based on the determined EGR quantity. For example, the control unit can adjust the fuel supply to the engine based on the estimated amount of EGR. In one example, the control unit adjusts the amount of fuel injection based on the amount of EGR. For example, the control unit can determine a control signal to send to the fuel injection device actuator, such as a pulse width of the signal determined based on an estimate of the EGR quantity. The control unit can determine the pulse width by a determination that directly considers a specific EGR quantity, such as an increase in pulse width with increasing EGR. Alternatively, the control unit can determine the pulse width based on a calculation using a lookup table, where the input is the EGR quantity and the output is the pulse width.

[0114] The procedure continues with 328, where procedure 300 involves resetting the lambda sensor to non-VV mode. Resetting the sensor to non-VV mode involves operating it at a lower voltage and using the sensor's output in non-VV mode, for example, to estimate AFR. Thus, in response to a request to determine an engine's air-fuel ratio, the lambda sensor can simply be operated at the initial voltage in a non-variable voltage mode, and engine operation can be adjusted based on an estimated air-fuel ratio. Here, the estimated air-fuel ratio is determined based on an output from the lambda sensor operating in the non-variable voltage mode. Procedure 300 ends.

[0115] In this way, the lambda sensor can be used for EGR estimation, and the engine fuel supply can be adjusted accordingly. The technical benefit of determining the correction factor for the exhaust water concentration from the ethanol content in the fuel and the ambient humidity, and subtracting this from the total water concentration, is that the resulting difference provides an accurate measurement of the EGR that is recirculated from the exhaust port to the intake port. Accurate EGR measurement therefore leads to improved EGR control, which in turn results in increased fuel efficiency and reduced NOx emissions.

[0116] The systems and methods described above provide a procedure that, during the operation of a lambda sensor in a variable voltage mode, wherein a reference voltage of the lambda sensor is adjusted from a lower, first voltage to a higher, second voltage, includes adjusting engine operation based on an exhaust gas recirculation (EGR) quantity estimated on the basis of an output of the lambda sensor and a determined correction factor based on the second voltage.In a first example of the method, the method may additionally or alternatively include that the determined correction factor incorporates an estimated ethanol content in the fuel, and further include estimating the ethanol content in the fuel based on an output from the lambda sensor while the lambda sensor is operating in variable voltage mode during a steady-state engine operating condition when the EGR is off and is not circulating from an exhaust port to an intake port. A second example of the method may optionally include the first example and further include that the steady-state engine operating condition includes an engine idle condition. A third example of the method may optionally include one or more of the first and second examples and further include that the determined correction factor also incorporates ambient humidity.A fourth example of the method may include one or more of the examples from the first to the third and further includes estimating the ambient humidity based on an output from the oxygen sensor during operation in variable voltage mode during an engine without fuel supply and based on a dry air pump current output from the oxygen sensor. A fifth example of the method may include one or more of the examples from the first to the fourth and further includes estimating the dry air pump current output based on an output from the oxygen sensor during operation in variable voltage mode during one or more instances after an engine start, after a number of miles traveled, after a duration of engine operation, after a number of engine cycles, and during the engine without fuel supply.A sixth example of the method may optionally include one or more of the first five examples and further includes that the engine state without fuel supply includes fuel cut-off during braking. A seventh example of the method may optionally include one or more of the first six examples and further includes that the output of the lambda sensor, on which the EGR quantity estimate is based, is obtained while the EGR flows from an exhaust port to an intake port, with the lambda sensor located in the exhaust port.An eighth example of the procedure may include one or more of the first to the seventh example and further includes determining a total water concentration in the exhaust gas based on the output of the lambda probe and determining a water concentration in the exhaust gas due to moisture and an ethanol content in the fuel based on the determined correction factor and estimating the EGR quantity by subtracting the water concentration in the exhaust gas due to moisture and the ethanol content in the fuel from the total water concentration.

[0117] The systems and methods described above also provided a procedure comprising: determining an exhaust gas recirculation (EGR) quantity flowing into the engine based on a first output from a lambda sensor during operation in a variable voltage mode, wherein a reference voltage of the lambda sensor is set from a lower, first voltage to a higher, second voltage with EGR flowing, and a second output from the lambda sensor during operation in the variable voltage mode without EGR flowing, and setting an engine operation based on the determined quantity of EGR.In a first example of the procedure, the method may additionally or alternatively include estimating an ethanol content in the fuel based on the second output of the lambda sensor during a static engine operating condition and deriving a first water concentration in engine exhaust gases based on the estimated ethanol content in the fuel. A second example of the procedure may include the first procedure and further includes estimating ambient humidity based on a third output of the lambda sensor during operation in variable voltage mode during an engine operating condition without fuel supply and based on a dry air pump current output of the lambda sensor, wherein the dry air pump current is estimated during one or more instances following an engine start, after a number of miles traveled, after a duration of engine operation, after a number of engine cycles, and during the engine operating condition without fuel supply.A third example of the method may include one or more of the first and second examples and further includes deriving a second water concentration in the exhaust gas based on the estimated ambient humidity. A fourth example of the method may include one or more of the first through third examples and further includes determining the amount of EGR flowing into the engine by subtracting both the first and second water concentrations from a total water concentration in the exhaust gas, the total water concentration being determined based on the first output of the lambda sensor.A fifth example of the method may include one or more of the first to fourth examples and further includes operating the lambda probe at only the first voltage in a non-variable voltage mode in response to a request to determine an air-fuel ratio of the engine and setting an engine operation based on an estimated air-fuel ratio, wherein the estimated air-fuel ratio is determined based on an output from the lambda probe operating in the non-variable voltage mode.

[0118] The systems and procedures described above provide a system for an engine that includes: an exhaust gas recirculation (EGR) system comprising an EGR channel coupling an exhaust port to an intake port, the EGR channel including an EGR valve; a lambda sensor configured to operate in a variable voltage mode, with a reference voltage of the lambda sensor being adjusted from a lower, first voltage to a higher, second voltage, and coupled to the exhaust port; and a controller comprising computer-readable instructions to: operate the lambda sensor in the variable voltage mode while the EGR valve is closed to generate a first output; open the EGR valve to circulate the EGR; and operate the lambda sensor in the variable voltage mode.to generate a second output; and to set engine operation based on an estimated amount of EGR, the estimated amount of EGR being determined based on a difference between the second output and the first output. In a first example of the system, the system may additionally or alternatively include that the control further includes instructions to generate both the first output and the second output during an engine idling condition. A second example of the system may optionally include the first example and further includes,that the control unit includes instructions to: operate the lambda sensor in variable voltage mode during an engine condition without fuel supply and generate a third lambda sensor output; and estimate ambient humidity based on the third lambda sensor output and further based on a dry air pump current output from the lambda sensor. A third example of the system optionally includes one or more of the first and second examples and further includes that the control unit also includes instructions to estimate the amount of EGR flowing into the engine based on a difference between the second output and both the first and third outputs. A fourth example of the system optionally includes the first through third examples and further includes,that the control further includes instructions for estimating the dry air pump current based on a ratio between a first pump current generated when the lambda probe is operated at the first voltage and a second pump current of the lambda probe generated when the lambda probe is operated at the second voltage.

[0119] It should be noted that the exemplary control and estimation routines contained herein can be used with different engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, including the controller, in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more from any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and advantages of the embodiments described here, but is provided for the sake of simplicity. One or more of the illustrated actions, processes, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, processes, and / or functions can graphically represent code that is to be programmed in non-volatile memory of the computer-readable storage medium in the engine control system, with the described actions being executed by carrying out the instructions in a system that includes the various engine hardware components in combination with the electronic control unit.

[0120] It is understood that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the foregoing technology can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0121] The following claims, in particular, describe certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Further combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims, regardless of whether they have a broader, narrower, the same, or different scope compared to the original claims, are also considered to be included in the subject matter of the present disclosure.

Claims

[1] Procedure, encompassing: During the operation of a lambda probe (126) in a variable voltage mode, wherein a reference voltage of the lambda probe (126) is adjusted from a lower, first voltage to a higher, second voltage; Setting an engine operation based on an exhaust gas recirculation quantity (EGR quantity) estimated on the basis of an output from the lambda sensor (126) and a determined correction factor based on the second voltage, where a dry air pumping current is determined from a first pumping current at the first voltage and a second pumping current at the second voltage, wherein the determined value for the dry air pump current is stored in a memory of a controller (12) and updated after each engine start, and wherein the correction factor is determined based on the second voltage using the stored dry air pump current. [2] Procedure, comprehensive: During the operation of a lambda probe (126) in a variable voltage mode, wherein a reference voltage of the lambda probe (126) is adjusted from a lower, first voltage to a higher, second voltage; Setting an engine operation based on an exhaust gas recirculation quantity (EGR quantity) estimated on the basis of an output from the lambda sensor (126) and a determined correction factor based on the second voltage, wherein the determined correction factor includes an estimated ethanol content in the fuel, and further includes estimating the ethanol content in the fuel based on an output of the lambda probe (126) during operation of the lambda probe (126) in the variable voltage mode during a steady-state engine operating condition when the EGR is switched off and is not circulating from an exhaust channel (48) to an intake channel (44). [3] Method according to claim 2, wherein the steady-state engine operation includes an engine idle state. [4] Method according to claim 1, wherein the determined correction factor further includes ambient humidity. [5] Method according to claim 4, further comprising estimating the ambient humidity based on an output from the lambda probe (126) during operation in the variable voltage mode during an engine condition without fuel supply and based on a dry air pump current output from the lambda probe (126). [6] The method of claim 5, further comprising estimating the dry air pump current output based on an output of the lambda probe (126) during operation of the lambda probe (126) in the variable voltage mode during one or more engine starts, after a number of miles traveled, after a duration of engine operation, after a number of engine cycles and the engine condition without fuel supply. [7] Method according to claim 5, wherein the engine state without fuel supply includes fuel shut-off during braking. [8] Method according to claim 1, wherein the output of the lambda sensor (126) on which the EGR quantity is based is obtained while the EGR flows from an exhaust channel (48) to an inlet channel (44), wherein the lambda sensor (126) is arranged in the exhaust channel (48). [9] The method of claim 8, further comprising determining a total water concentration in the exhaust gas based on the output of the lambda probe (126) and determining a water concentration in the exhaust gas due to moisture and an ethanol content in the fuel based on the determined correction factor and estimating the EGR quantity by subtracting the water concentration in the exhaust gas due to moisture and the ethanol content in the fuel from the total water concentration. [10] System for a motor (10), comprising: an exhaust gas recirculation system (EGR system) comprising an EGR channel (140) coupling an exhaust channel (48) to an intake channel (44), wherein the EGR channel (140) includes an EGR valve (142); a lambda sensor (126) configured to operate in a variable voltage mode, wherein a reference voltage of the lambda sensor (126) is adjusted from a lower, first voltage to a higher, second voltage, and is coupled to the exhaust channel (48); and a controller (12) which contains computer-readable instructions for the following: Operating the lambda sensor (126) in variable voltage mode while the EGR valve (142) is closed to generate an initial output; Opening the EGR valve (142) to circulate the EGR, and operating the lambda sensor (126) in variable voltage mode to generate a second output; and Setting an engine operation based on an estimated amount of EGR, wherein the estimated amount of EGR is determined based on a difference between the second output and the first output. [11] System according to claim 10, wherein the control (12) further includes instructions for generating both the first output and the second output during an engine idling state. [12] System according to claim 10, wherein the control (12) further comprises instructions for the following: Operating the lambda sensor (126) in variable voltage mode during an engine condition without fuel supply and generating a third output from the lambda sensor (126); and Estimating ambient humidity based on the third output of the lambda probe (126) and further based on a dry air pump current output of the lambda probe (126). [13] System according to claim 12, wherein the control (12) further includes instructions for estimating the amount of EGR flowing into the engine (10) based on a difference between the second output and both the first and third outputs. [14] System according to claim 12, wherein the control (12) further includes instructions for estimating the dry air pump current based on a ratio between a first pump current generated when the lambda probe (126) is operated with the first voltage and a second pump current of the lambda probe (126) generated when the lambda probe (126) is operated with the second voltage.

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