Method and system for determining the knock control fluid composition

Abstract

Power engine process, which includes the following: Injecting a quantity of a water-alcohol mixture; Applying a reference voltage to an inlet oxygen sensor; Monitoring a change in the sensor's pump current; Determining the first part of the change in pump flow due to the water content of the mixture; and Determining a second part of the change in pump current due to the alcohol content of the mixture.

Description

Field of the invention

[0001] The present invention relates generally to methods and systems for determining the composition of windshield washer fluid injected into an engine for knock control. State of the art / brief description

[0002] A variety of knock control fluids have been developed to mitigate abnormal combustion events, including various combinations of gasoline, ethanol, methanol, other alcohols, water, and other inert fluids. Water injection, for example, reduces knock, provides charge cooling, and lowers octane requirements. Additionally, the need for a specific knock control fluid is reduced because water injection can also be used for engine dilution control.

[0003] Another example of a knock control fluid is shown by Surnilla in US 7,533,651 B2. Therein, the direct injection of a washer fluid containing water and alcohol (e.g., an engine coolant or methanol) utilizes the charge cooling properties of both the fluid and the direct injection to reduce knock. In addition to protecting the water from freezing, the inclusion of an engine coolant in the composition of the injected knock control fluid provides an additional benefit in that light hydrocarbons (such as methanol) are available to aid in the combustion process. The overall approach increases engine efficiency while reducing the octane requirement of injected fuel, thereby increasing engine power output.Here, the windshield washer fluid can be converted for knock control in addition to its use for cleaning a vehicle windshield.

[0004] DE 10 2014 119 377 A1 discloses a method for accurately learning the deviation of individual components of an intake or outlet oxygen sensor. A correction factor is learned based on a sensor reading under dry air conditions, with the dry air reading being learned by applying a higher reference voltage to the sensor. An ethanol transfer function is then adjusted based on the learned correction factor to improve the accuracy of estimating the combusted fuel ethanol content.

[0005] DE 10 2013 219 669 A1 discloses methods and systems for improving engine knock control in light of a decrease in the charge air cooling efficiency of a knock control fluid at higher temperatures. In response to the prediction of an increased temperature of a knock control fluid at the time of discharge from a direct injection engine, an injection pulse width is adjusted. Any knock mitigation deficiencies are compensated for by using alternative engine settings such as boost or spark timing.

[0006] US 7,533,651 B2 discloses a system for a vehicle engine having a combustion chamber located within the engine, a delivery system configured to deliver a fuel and a fluid in varying ratios to at least the combustion chamber. The delivery system includes at least one direct injector configured to inject at least the fluid directly into the combustion chamber. A control system is configured to advance the timing of the fluid delivered from the direct injector to the combustion chamber to reduce the likelihood of knocking and to retard the timing of the fluid delivered from the direct injector to the combustion chamber to reduce the likelihood of pre-ignition.

[0007] However, the inventors herein have recognized a problem with this approach. Variations in windshield washer fluid composition may exist. For example, there may be a large variation in the ethanol or methanol content of the fluid itself. Additionally, when a windshield washer fluid tank is refilled, the composition of the available washer fluid may vary based on the amount and composition of washer fluid left in the tank following refilling. While this does not affect the fluid's ability to clean a windshield wiper, it may affect the fluid's knock control capability. For example, the fluid's octane rating may change. Therefore, various engine parameters are adjusted based on the knock control fluid injected.For example, the cylinder fueling can be adjusted based on the alcohol content of the injected fluid. Additionally, engine parameters may need to be adjusted based on the type of alcohol in the fluid (e.g., depending on whether the alcohol is ethanol or methanol). Consequently, errors in estimating a windshield washer fluid composition can lead to significant air-fuel ratio errors, degrading engine performance. Furthermore, the use of a windshield washer fluid as a knock control fluid may be limited if the composition of the windshield washer fluid is not precisely known. On the other hand, adding a sensor dedicated to estimating the alcohol content and composition of a knock control fluid can add significant cost and complexity.

[0008] In one example, the problems described above may be solved by a method for an engine that includes: during selected conditions, injecting an amount of a water-alcohol mixture into an engine intake; applying a voltage to an intake oxygen sensor; monitoring a change in the sensor's pumping current; detecting a first portion of the change in the pumping current due to a water content of the mixture; and detecting a second portion of the change in the pumping current due to an alcohol content of the mixture. This allows the composition of a knock control fluid injected into an engine to be accurately determined using existing engine sensors.

[0009] For example, following refilling a windshield washer fluid tank, a windshield washer fluid composition may be estimated using an intake oxygen sensor. The windshield washer fluid may then be used as a knock control fluid. As such, the windshield washer fluid may contain a mixture of water and alcohol, but not gasoline. Furthermore, an alcohol type in the fluid may be known a priori. For example, it may be known that the windshield washer fluid is a water-ethanol mixture or a water-methanol mixture. However, a ratio of water to the particular alcohol in the fluid may not be precisely known. A controller may inject a defined mass of the knock control fluid into the engine intake, such as the intake manifold, downstream of an intake throttle and upstream of an intake oxygen sensor.The fluid may be injected while exhaust gas recirculation is deactivated to reduce interference with the exhaust gas recirculation results. A lower reference voltage (e.g., 450 mV) may then be applied to the intake oxygen sensor, and an output from the sensor may be observed. For example, a pumping current (or a change in pumping current) may be output. As such, the pumping current may be affected by a reduction in the oxygen concentration at the oxygen sensor due to the water content of the knock control fluid, as well as due to the alcohol content of the knock control fluid. In particular, the water in the knock control fluid may have a dilution effect on the oxygen sensor, while the alcohol in the knock control fluid may combust with oxygen at the sensor, reducing the oxygen concentration at the sensor.An engine control system can then calculate the alcohol content of the knock control fluid based on a change in pumping current and injection mass. For example, the engine control system can refer to a 3D calibration map to estimate the fluid's alcohol content and update the fluid's composition. By determining the fluid's composition, the flexibility of using windshield washer fluid as a knock control fluid can be improved.

[0010] This allows an intake oxygen sensor to be used to estimate the composition (including hydrocarbon type and alcohol content) of a knock control fluid. The technical effect of modulating the reference voltage of an intake oxygen sensor is that a change in the sensor's pumping current attributed to the water component of the knock control fluid can be better distinguished from the change attributed to the alcohol component of the knock control fluid. This is because the dilution effect on the oxygen sensor has a significantly different contribution than the combustion effect of the alcohol. By better estimating the composition of an injected knock control fluid, the use of the knock control fluid can be extended to engines using different fuel types, thereby improving the robustness of the system.Additionally, the accuracy of fuel octane estimates can be increased, enabling improved ignition control. For example, spark retard utilization for knock control can be reduced, delivering fuel economy benefits. Using an existing intake oxygen sensor to determine the knock control fluid composition reduces the need for a dedicated sensor without compromising estimation accuracy.

[0011] It is understood that the above summary is provided to introduce, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. Short description of the drawings Fig. Figure 1 shows a schematic diagram of a power machine system. Fig. Figure 2 shows a detailed diagram of an engine combustion chamber. Fig. 3 shows a schematic diagram of an example oxygen sensor. Fig. 4 is a flowchart illustrating a routine for using an intake oxygen sensor for knock control fluid alcohol estimation. Fig. 5 is a flowchart illustrating a routine for using an outlet oxygen sensor for knock control fluid alcohol estimation. Fig. 6 is a map showing an exemplary relationship between an alcohol content of a knock control fluid in relation to each change in pumping current of an oxygen sensor and a mass of the knock control fluid injected into an engine. Detailed description

[0012] The following description relates to systems and methods for determining the composition of a knock control fluid injected into an engine, such as the engine of Fig. 1-2, based on outputs from an intake oxygen sensor, such as the sensor in Fig. 3. Therefore, the intake oxygen sensor may be used during various engine operating conditions to determine the alcohol content of a fuel supplied to the engine during engine combustion or the alcohol composition of the knock control fluid that may be released in response to an indication of knock ( Fig. 3) supplied to the engine. An engine controller may be configured to execute a control routine, such as the example routine of Fig. 4-5, to estimate the composition of the knock control fluid, including the alcohol content and the hydrocarbon content of the fluid, based on a change in the pumping current of the intake oxygen sensor after modulating a reference voltage. The control device may refer to a map, such as the exemplary map of Fig. 6, to correlate the change in pumping current and injection mass with the alcohol content of the injected fluid. One or more engine operating parameters, such as ignition timing and / or fuel injection quantity, can be adjusted based on the determined knock control fluid composition. This allows for expanded engine knock control fluid utilization.

[0013] Fig. 1 shows a schematic diagram of an exemplary turbocharged engine system 100 including a multi-cylinder internal combustion engine 10 and dual turbochargers 120 and 130. As a non-limiting example, engine system 100 may be included as part of a propulsion system for a passenger vehicle. Engine system 100 may receive intake air via intake passage 140. Intake passage 140 may include an air cleaner 156 and an EGR throttle 131. Engine system 100 may be a split-engine system in which intake passage 140, downstream of EGR throttle 131, is branched into first and second parallel intake passages, each containing a turbocharger compressor.In particular, at least a portion of the intake air is directed to the compressor 122 of the turbocharger 120 via a first parallel intake passage 142, and at least another portion of the intake air is directed to the compressor 132 of the turbocharger 130 via a second parallel intake passage 144 of the intake passage 140.

[0014] The first portion of the total intake air compressed by the compressor 122 may be supplied to the intake manifold 160 via the first parallel branched intake passage 146. Thus, the intake passages 142 and 146 form a first parallel branch of the engine's air intake system. Similarly, a second portion of the total intake air may be compressed by the compressor 132 and may be supplied to the intake manifold 160 via the second parallel branched intake passage 148. Thus, the intake passages 144 and 148 form a second parallel branch of the engine's air intake system. As shown in Fig. 1, the intake air from the intake passages 146 and 148 may be recombined via a common intake passage 149 before reaching the intake manifold 160 where the intake air may be supplied to the engine.

[0015] A first EGR throttle valve 131 may be positioned in the engine intake upstream of the first and second parallel intake passages 142 and 144, while a second air intake throttle valve 158 may be positioned in the engine intake downstream of the first and second parallel intake passages 142 and 144 and downstream of the first and second parallel branched intake passages 146 and 148, for example, in the common intake passage 149.

[0016] In some examples, intake manifold 160 may include an intake manifold pressure sensor 182 for estimating manifold pressure (MAP) and / or an intake manifold temperature sensor 183 for estimating manifold air temperature (MCT), each in communication with controller 12. Intake passage 149 may include a charge air cooler (CAC) 154 and / or a throttle (such as second throttle plate 158). The position of throttle plate 158 may be adjusted by the control system via a throttle actuator (not shown) communicatively coupled to controller 12. A surge prevention valve 152 may be provided to selectively bypass the compressor stages of turbochargers 120 and 130 via bypass passage 150.As an example, the anti-surge valve 152 may open to allow flow through the bypass passage 150 when the intake air pressure upstream of the compressors reaches a threshold.

[0017] The intake manifold 160 may further include an intake gas oxygen sensor 172. In one example, the oxygen sensor is a UEGO sensor, such as the exemplary UEGO sensor of Fig. 3. As stated herein, the intake gas oxygen sensor may be configured to provide an estimate of the oxygen content of the fresh air received in the intake manifold. Furthermore, when EGR is flowing, a change in oxygen concentration at the sensor may be used to infer an amount of EGR and used for precise EGR flow control. Further, during select fueling conditions, the sensor's reference voltage may be modulated, and the corresponding change in current may be used to infer the alcohol content of an injected fuel. As also stated herein, during conditions when a knock control fluid is injected, the sensor's reference voltage may be modulated, and the corresponding change in current may be used to infer the water content of the injected fluid and distinguish it from the alcohol content of the injected fluid.In the example shown, the oxygen sensor 162 is positioned upstream of the throttle 158 and downstream of the charge air cooler 154. However, in other embodiments, the oxygen sensor may be positioned upstream of the CAC.

[0018] A pressure sensor 174 may be positioned adjacent to the oxygen sensor for estimating an intake pressure at which an oxygen sensor output is received. Since the oxygen sensor output is influenced by intake pressure, a reference oxygen sensor output may be learned at a reference intake pressure. In one example, the reference intake pressure is throttle inlet pressure (TIP), with pressure sensor 174 being a TIP sensor. In other examples, the reference intake pressure is manifold pressure (MAP) sensed by MAP sensor 182.

[0019] The engine 10 may include a plurality of cylinders 14. In the example shown, the engine 10 includes six cylinders arranged in a V-configuration. More specifically, the six cylinders are arranged on two banks 13 and 15, with each bank having three cylinders. In other examples, the engine 10 may include two or more cylinders, such as 3, 4, 5, 8, 10, or more cylinders. These various cylinders may be evenly split and configured in other configurations, such as a V, inline, or horizontally opposed configuration, etc. Each cylinder 14 may be configured with a fuel injector 166. In the example shown, the fuel injector 166 is a direct-in-cylinder fuel injector. However, in other examples, the fuel injector 166 may also be configured as a port fuel injector.

[0020] Intake air supplied to each cylinder 14 (also called combustion chamber 14) via a common intake passage 149 may be used for fuel combustion, and combustion products may then be exhausted via bank-specific parallel exhaust passages. In the depicted example, a first bank 13 of cylinders of engine 10 may exhaust combustion products via a first parallel exhaust passage 17, and a second bank 15 of cylinders may exhaust combustion products via a second parallel exhaust passage 19. The first and second parallel exhaust passages 17 and 19 may each further include a turbocharger turbine. In particular, combustion products exhausted via exhaust passage 17 may be directed through exhaust turbine 124 of turbocharger 120, which in turn may provide mechanical work to compressor 122 via shaft 126 to provide compression of the intake air.Alternatively, some or all of the exhaust gas flowing through the exhaust passage 17 may bypass the turbine 124 via the turbine bypass passage 123, as controlled by the wastegate 128. Similarly, combustion products exhausted via the exhaust passage 19 may be directed to the exhaust turbine 134 of the turbocharger 130, which in turn may provide mechanical work to the compressor 132 via the shaft 136 to provide compression for the intake air flowing through the second branch of the engine's intake system. Alternatively, some or all of the exhaust gas flowing through the exhaust passage 19 may bypass the turbine 134 via the turbine bypass passage 133, as controlled by the wastegate 138.

[0021] In some examples, exhaust turbines 124 and 134 may be configured as variable geometry turbines, where controller 12 may adjust the position of the turbine impeller blades (or vanes) to vary the energy level received from the exhaust flow and applied to their respective compressors. Alternatively, exhaust turbines 124 and 134 may be configured as variable nozzle turbines, where controller 12 may adjust the position of the turbine nozzle to vary the energy level received from the exhaust flow and applied to their respective compressors. For example, the control system may be configured to independently vary the vane or nozzle position of exhaust turbines 124 and 134 via respective actuators.

[0022] Exhaust gases in the first parallel exhaust passage 17 may be directed to the atmosphere via the branched parallel exhaust passage 170, while exhaust gases in the second parallel exhaust passage 19 may be directed to the atmosphere via the branched parallel exhaust passage 180. The exhaust passages 170 and 180 may include one or more exhaust aftertreatment devices, such as a catalyst, and one or more exhaust gas sensors.

[0023] Further, engine 10 may include one or more exhaust gas recirculation (EGR) passages or circuits for recirculating at least a portion of the exhaust gas from the exhaust manifold to the intake manifold. These may include high-pressure EGR circuits for providing high-pressure EGR (HP EGR) and low-pressure EGR circuits for providing low-pressure EGR (LP EGR). In one example, HP EGR may be provided in the absence of boost provided by turbochargers 120, 130, while LP EGR may be provided in the presence of turbocharger boost and / or when the exhaust gas temperature is above a threshold. In still other examples, both HP EGR and LP EGR may be provided simultaneously.

[0024] In the example shown, engine 10 may include a low-pressure EGR circuit 202 for recirculating at least a portion of the exhaust gas from the first branched parallel exhaust passage 170 downstream of the turbine 124 to the first parallel intake passage 142 upstream of the compressor 122. In some embodiments, a second low-pressure EGR circuit (not shown) may also be provided for recirculating at least a portion of the exhaust gas from the second branched parallel exhaust passage 180 downstream of the turbine 134 to the second parallel intake passage 144 upstream of the compressor 132. The LP EGR circuit 202 may include an LP EGR valve 204 for controlling an EGR flow (i.e., an amount of recirculated exhaust gas) through the circuits and an EGR cooler 206 for lowering the temperature of an exhaust gas flowing through the EGR circuit before being recirculated to the engine intake.Under certain conditions, the EGR cooler 206 may also be used to warm the exhaust gas flowing through the LP EGR circuit 202 before the exhaust gas enters the compressor to prevent water droplets from impacting the compressors.

[0025] The engine 10 may further include a first high-pressure EGR circuit 208 for recirculating at least a portion of the exhaust gas from the first parallel exhaust passage 17 upstream of the turbine 124 to the intake manifold 160 downstream of the intake throttle 158. Likewise, the engine may include a second high-pressure EGR circuit (not shown) for recirculating at least a portion of the exhaust gas from the second parallel exhaust passage 18 upstream of the turbine 134 to the second branched parallel intake passage 148 downstream of the compressor 132. EGR flow through the HP EGR circuits 208 may be controlled via the HP EGR valve 210.

[0026] A positive crankcase ventilation (PCV) port 102 may be configured to supply blow-by gases to the engine intake manifold along the second parallel intake passage 144. In some embodiments, flow of PCV air through the PCV port 102 may be controlled by a dedicated PCV port valve. Thus, when the PCV valve is closed, crankcase ventilation to the engine intake is disabled. Likewise, a purge port 104 may be configured to supply purge gases from a fuel system reservoir to the engine intake manifold along the passage 144. In some embodiments, purge air through the purge port 104 may be controlled by a dedicated purge port valve. Thus, when the purge valve is closed, fuel vapor purged to the engine intake is disabled.

[0027] The humidity sensor 112 and the pressure sensor 114 may be included in only one of the parallel intake passages (shown herein in the first parallel intake air passage 142, but not in the second parallel intake passage 144) downstream of the EGR throttle 131. In particular, the humidity sensor and the pressure sensor may be included in the intake passage that does not receive the PCV or purge air. The humidity sensor 112 may be configured to estimate a relative humidity of the intake air. In one embodiment, the humidity sensor 112 is an oxygen sensor configured to estimate the relative humidity of the intake air based on the sensor's output at one or more voltages. Because purge air and PCV air can interfere with the humidity sensor's readings, the purge orifice and the PCV orifice are positioned in a different intake passage than the humidity sensor.Pressure sensor 114 may be configured to estimate intake air pressure. In some embodiments, a temperature sensor may also be included in the same parallel intake passage downstream of EGR throttle 131.

[0028] Intake oxygen sensors 172 may be used during select conditions to estimate an intake oxygen concentration and infer an amount of EGR dilution at the fuel engine based on a change in intake oxygen concentration after the EGR valve 204 opens. For example, upon applying a reference voltage (Vs) to the sensor, a pumping current (Ip) is output by the sensor. The change in oxygen concentration may be proportional to the change in pumping current (delta Ip) output by the sensor. Similarly, during other select conditions, the intake oxygen sensor 172 may be used to estimate the water content of the intake charge (i.e., ambient humidity) or the water content of an injected liquid (and infer the alcohol content of the injected liquid).Furthermore, as noted herein, during other conditions, the intake oxygen sensor may be used to estimate the water content and alcohol content of a knock control fluid and estimate a composition of the knock control fluid accordingly. In one example, the knock control fluid is windshield washer fluid. The reference voltage (Vs) may be applied to the sensor, and a change in pumping current (Ip) output by the sensor may be detected. A first portion of the change in pumping current (Delta Ip) output by the sensor attributable to the water content of the injected knock control fluid may be detected and distinguished from a second portion of the change in pumping current attributable to the alcohol content of the injected knock control fluid.

[0029] In still further examples, an exhaust oxygen sensor, such as sensor 248 of Fig. 2, during selected conditions for estimating one or more of the water content of an injected fuel (and deriving the alcohol content of the injected fluid), a ratio of the water content to the alcohol content of a knock control fluid. Estimating a composition of the knock control fluid may include modulating the voltage applied to the sensor between a higher and a lower voltage and finding a change in the pumping current (Ip) output by the sensor. A first portion of the change in the pumping current (Delta Ip) output by the sensor attributable to the water content of the injected knock control fluid may be found and distinguished from a second portion of the change in the pumping current attributable to the alcohol content of the injected knock control fluid.

[0030] The position of the intake and exhaust valves of each cylinder 14 may be controlled by hydraulically actuated lifters coupled to valve pushrods or by a direct-acting mechanical vane system utilizing cam lobes. In this example, at least the intake valves of each cylinder 14 may be controlled by cam actuation using a cam actuation system. In particular, the valve cam actuation system 25 may include one or more cams and may utilize variable cam timing or variable lift for intake and / or exhaust valves. In alternative embodiments, the intake valves may be controlled by electric valve actuation. Similarly, the exhaust valves may be controlled by cam actuation systems or electric valve actuation.

[0031] The engine system 100 may be controlled at least in part by a control system 15 including the control device 12 and by input from a vehicle operator via an input device (not shown). The control system 15 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein in Fig. 1 and Fig. 2) and sends control signals to a plurality of actuators 81. As an example, sensors 16 may include humidity sensor 112, intake air pressure sensor 114, MAP sensor 182, MCT sensor 183, TIP sensor 174, and intake air oxygen sensor 172. In some examples, common intake passage 149 may further include a throttle inlet temperature sensor for estimating a throttle air temperature (TCT). In other examples, one or more of the EGR passages may include pressure, temperature, and air-fuel ratio sensors for determining EGR flow characteristics. As another example, the actuators 81 may include the fuel injector 166, the HP EGR valves 210 and 220, the LP EGR valves 204 and 214, the throttle bodies 158 and 131, and the wastegates 128, 138.Other actuators, such as a variety of additional valves and throttles, may be connected to various locations in the engine system 100, such as the ones related to . Fig. 2. The control device 12 receives signals from the various sensors Fig. 1 (and Fig. 2) and exposes the various actuators Fig. 1 (and Fig. 2) to adjust engine operation based on the received signals and instructions stored in a memory of the controller. For example, the controller 12 may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on an instruction or code programmed therein according to one or more routines. Example control routines are described herein with respect to Fig. 4 - 5 described.

[0032] Fig. Figure 2 illustrates a detailed embodiment of a combustion chamber, such as a combustion chamber of the engine 10 Fig. 1. Previously in Fig. 1 introduced components are similarly numbered and not reintroduced.

[0033] The engine 10 may receive control parameters from a control system including a controller 12 and input from a vehicle operator 230 via an input device 232. In this example, the input device 232 includes an accelerator pedal and a pedal position sensor 234 for generating a proportional pedal position signal PP. The cylinder (also referred to herein as the "combustion chamber") 14 of the engine 10 may include combustion chamber walls 236 with a piston 238 positioned therein. The piston 238 may be coupled to the crankshaft 240 such that reciprocating motion of the piston is translated into rotational motion of the crankshaft. The crankshaft 240 may be coupled to at least one drive wheel of the passenger vehicle via a gear system. Further, a starter motor may be coupled to the crankshaft 240 via a flywheel to enable starting operation of the engine 10.

[0034] The engine 10 is coupled in a vehicle system 100 that includes a windshield wiper system that enables cleaning of a vehicle windshield 68. The windshield 68 may be a front or rear windshield of a vehicle. The windshield wiper system includes at least one windshield wiper 70 driven by a wiper motor 72. In response to an operator request and based on input from the controller 12, the wiper motor 72 may be energized, causing the wiper 70 to perform multiple sweep cycles, known as wiping or sweeping, across the windshield 68. The wiping or sweeping allows the wiper blade 71 to remove moisture, residue, and foreign particles from the surface of the windshield 68.While the wiper motor 72 is operating and while the wiper blade 71 is sweeping, the controller 12 may, based on a request from a vehicle driver, alternately inject or eject windshield washer fluid onto the windshield via a wiper injector 74. The windshield washer fluid may be stored in a reservoir 76, from where it is supplied to the windshield. As noted herein, the reservoir 76 may be further coupled to the intake passage as well as the engine cylinder. This allows the windshield washer fluid to be injected to provide knock control in addition to its use for windshield wiping purposes.In particular, the windshield washer fluid may be injected into the intake manifold, specifically into the intake passage 246, downstream of the intake throttle, during knock conditions, thereby enabling the windshield washer fluid to be used as a knock control fluid. Additionally or alternatively, the windshield washer fluid may be directly injected into an engine cylinder via a direct injection valve, such as the direct fuel injector or a dedicated direct fuel injector, to provide knock control. The windshield washer fluid stored in the reservoir 76 may contain a combination of water and alcohol, such as methanol or isopropanol. However, the windshield washer fluid does not contain any gasoline.

[0035] Therefore, there may be considerable variation in the water-alcohol content of the windshield washer fluid. To enable the windshield washer fluid to be used reliably as a knock control fluid, the composition of the windshield washer fluid may need to be known. As with Fig. 1, during selected conditions, such as immediately after the windshield washer fluid reservoir has been refilled, an inlet oxygen sensor, such as sensor 172, may be used to estimate the water-alcohol content of the windshield washer fluid. Alternatively, an exhaust oxygen sensor, such as sensor 228, may be used to estimate the water-alcohol content of the windshield washer fluid. Exemplary methods for estimating a windshield washer fluid composition using an inlet or outlet oxygen sensor are described with respect to Fig. 4-5 shown.

[0036] Cylinder 14 may receive intake air via a series of intake air passages 242, 244, and 246. Intake air passage 246 may be connected to other cylinders of engine 10 in addition to cylinder 14. In some embodiments, one or more of the intake passages may include a boosting device, such as a turbocharger or a supercharger. For example, Fig. 2 shows the engine 10 configured with a turbocharger including a compressor 274 disposed between the intake passages 242 and 244 and an exhaust turbine 276 disposed along the exhaust passage 248. The compressor 274 may be at least partially driven by the exhaust turbine 276 via a shaft 280, wherein the boosting device is configured as a turbocharger. However, in other examples, such as when the engine 10 is provided with a supercharger, the exhaust turbine 276 may optionally be omitted, wherein the compressor 274 may be driven by a mechanical input from an engine or the engine. A throttle 262, including a throttle valve 264, may be provided along an intake passage of the engine to vary the flow rate and / or pressure of the intake air supplied to the engine cylinders.For example, the throttle 262 may be located downstream of the compressor 274, as shown in FIG. Fig. 2, or alternatively upstream of the compressor 274.

[0037] Exhaust passage 248 may receive exhaust gases from other cylinders of engine 10 in addition to cylinder 14. Exhaust sensor 228 is shown coupled to exhaust port 248 upstream of emission control device 278. Sensor 228 may be selected from various suitable sensors for providing an indication of exhaust air / fuel ratio, such as a linear oxygen sensor or UEGO (universal or widerange exhaust gas oxygen), a dual-state oxygen sensor or EGO sensor (as shown), a HEGO (heated EGO), a NOx, an HC, or a CO sensor. Emission control device 278 may be a three-way catalyst (TWC), a NOx trap, various other emission control devices, or combinations thereof.

[0038] The exhaust temperature may be measured by one or more temperature sensors (not shown) located in the exhaust passage 248. Alternatively, the exhaust temperature may be inferred based on engine operating conditions, such as speed, load, air-fuel ratio (AFR), spark retard, etc. Furthermore, the exhaust temperature may be calculated by one or more exhaust sensors 228. It should be understood that the exhaust temperature may alternatively be estimated by any combination of temperature estimation methods listed herein.

[0039] Each cylinder of engine 10 may include one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown including at least one intake poppet valve 250 and at least one exhaust poppet valve 256 positioned in an upper region of cylinder 14. In some embodiments, each cylinder of engine 10, including cylinder 14, may include at least two intake poppet valves and at least two exhaust poppet valves positioned in an upper region of the cylinder.

[0040] The intake valve 250 may be controlled by the controller 12 through cam actuation via the cam actuation system 251. Likewise, the exhaust valve 256 may be controlled by the controller 12 via the cam actuation system 253. The cam actuation systems 251 and 253 may each include one or more cams and may utilize one or more cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVS), and / or variable valve lift (VVL) systems, which may be actuated by the controller 12 to vary valve operation. The operation of the intake valve 250 and the exhaust valve 256 may be determined by valve position sensors (not shown) and / or camshaft position sensors 255 and 257, respectively.In alternative embodiments, the intake and / or exhaust valves may be controlled by electric valve actuation. For example, cylinder 14 may alternatively have an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation, including CPS and / or VCT systems. In still further embodiments, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a VAV actuator or actuation system.

[0041] Cylinder 14 may have a compression ratio that is the ratio of volume when piston 238 is at bottom dead center or top dead center. Conventionally, the compression ratio is in the range of 9:1 to 10:1. However, in some examples where different fuels are used, the compression ratio may be increased. This may occur, for example, when using higher octane fuels or fuels with a higher latent heat of vaporization. The compression ratio may also be increased if direct injection is used due to its effect on engine knock.

[0042] In some embodiments, each cylinder of engine 10 may include a spark plug 292 for initiating combustion. Ignition system 290 may provide an ignition spark to combustion chamber 14 via spark plug 292 in response to spark advance signal SA from controller 12 during selected operating modes. However, in some embodiments, spark plug 292 may be omitted, for example, when engine 10 is capable of initiating combustion through auto-ignition or by fuel injection, as may be the case with some diesel engines.

[0043] In some embodiments, each cylinder of engine 10 may be configured with one or more fuel injectors to provide a knock control fluid thereto. In some embodiments, the knock control fluid may be a fuel, wherein the injector is also referred to as a fuel injector. As a non-limiting example, cylinder 14 is shown including a fuel injector 266. Fuel injector 266 is shown coupled directly to cylinder 14 to inject fuel directly therein in proportion to the pulse width of a signal FPW received from controller 12 via an electronic driver 268. In this manner, fuel injector 166 provides so-called direct injection (hereinafter also referred to as "DI") of fuel into combustion cylinder 14. Although Fig. While Figure 1 shows the injector 266 as a side injector, it may also be positioned above the piston, for example, near the position of the spark plug 292. Such a position may improve mixing and combustion when the engine is running on an alcohol-based fuel, due to the lower volatility of some alcohol-based fuels. Alternatively, the injector may be positioned above and near the intake valve to improve mixing. Fuel may be supplied to the fuel injector 266 from a high-pressure fuel system 8, including one or more fuel tanks 78, fuel pumps, and a fuel rail.Alternatively, fuel may be delivered by a single-stage fuel pump at a lower pressure, in which case the timing of direct fuel injection during the compression stroke may be more limited than when using a high-pressure fuel system. Although not shown, fuel tanks 78 may further include a pressure transducer that provides a signal to controller 12. It should be understood that in another embodiment, fuel injector 266 may be a port injector that delivers fuel to the intake port upstream of cylinder 14.

[0044] Fuel may be delivered to the cylinder by the injector during a single cylinder cycle. Furthermore, the distribution and / or relative amount of fuel delivered by the injector may vary with operating conditions, such as air charge temperature, as described below. Furthermore, during a single combustion event, multiple injections of the delivered fuel may be performed per cycle. The multiple injections may be performed during the compression stroke, intake stroke, or any appropriate combination thereof.

[0045] As described above, Fig. 1 only a single cylinder of a multi-cylinder engine. Thus, each cylinder can have its own set of intake / exhaust valves, fuel injector(s), spark plug, etc.

[0046] The fuel tanks 78 in the fuel system 8 may contain fuel or knock control fluids with different properties, such as different compositions. These differences may include different alcohol content, different water content, different octane, different heat of vaporization, different fuel mixtures, different water contents, different flammability limits, and / or combinations thereof, etc. In one example, knock control fluids with different alcohol contents could contain one fuel that is gasoline and the other being ethanol or methanol. Other alcohol-containing fuels could be a mixture of alcohol and water, a mixture of alcohol and water, etc.In yet another example, both fuels may be alcohol blends, where the first fuel may be a gasoline-alcohol blend with a lower alcohol ratio than a gasoline-alcohol blend of a second fuel with a higher alcohol ratio, such as E10 (which is approximately 10% ethanol) as a first fuel and E85 (which is approximately 85% ethanol) as a second fuel. Additionally, the first and second fuels may also differ in other fuel properties, such as a difference in temperature, viscosity, octane rating, latent heat of vaporization, etc.

[0047] Furthermore, the fuel properties of the fuel or knock control fluid stored in the fuel tank may vary frequently. Daily refueling fluctuations may thus result in frequently varying fuel compositions, thereby affecting the fuel composition delivered by injector 166.

[0048] In addition to the fuel tanks, the fuel system 8 may also include a reservoir 76 for storing a knock control fluid, herein a windshield washer fluid. Although the reservoir 76 is illustrated as distinct from the one or more fuel tanks 78, it should be understood that in other examples, the reservoir 76 may be one of the one or more fuel tanks 78. The reservoir 76 may be coupled to the direct fuel injector 266 such that the windshield washer fluid may be injected directly into the cylinder 14. During some conditions, in response to an indication of knock, an engine controller may inject windshield washer fluid used as a knock control fluid into the intake manifold downstream of the intake throttle to increase engine dilution and thereby control the premature and undesirable detonation event.Additionally or alternatively, in response to an indication of knock, the engine controller may directly inject windshield washer fluid used as a knock control fluid into the engine cylinder to increase engine dilution and thereby control the premature and undesirable detonation event.

[0049] In some embodiments, the fuel system may also include a reservoir for storing water coupled to the direct fuel injector so that water can be injected directly into the cylinder. Therefore, injecting water provides "liquid EGR," allowing for significant EGR benefits. However, during conditions when fluid must be conserved or when a reserve is needed when liquid EGR is unavailable, an external EGR system may be added.

[0050] The engine may further include one or more exhaust gas recirculation passages for redirecting at least a portion of the exhaust gas from the engine outlet to the engine inlet. Fig. 2 shows a low-pressure EGR (LP-EGR) system, but an alternative embodiment may include only a high-pressure EGR (HP-EGR) system or a combination of LP-EGR and HP-EGR systems. The LP-EGR is routed through the LP-EGR passage 249 from upstream of the turbine 276 to downstream of the compressor 274. The amount of LP-EGR provided to the intake manifold 244 may be varied by the controller 12 via the LP-EGR valve 252. The LP-EGR system may include an LP-EGR cooler 258 to transfer heat from the EGR gases, for example, to the engine coolant. If present, the HP EGR system may route the HP EGR through a dedicated HP EGR line (not shown) from upstream of the turbine 276 to downstream of the compressor 274 (and upstream of the intake throttle 262) via an HP EGR cooler.The amount of HP EGR supplied to the intake manifold 244 may be varied by the controller 12 via an HP EGR valve (not shown).

[0051] Under some conditions, the EGR system may be used to regulate the temperature of the air and fuel mixture within the combustion chamber 14. It may therefore be desirable to measure or estimate the EGR mass flow. For example, one or more sensors 259 may be positioned within the HP EGR line 249 to provide an indication of a pressure and / or temperature and / or air-fuel ratio of exhaust gas recirculated through the HP EGR line. Exhaust gas rerouted through the LP EGR line 249 may be diluted with fresh intake air at a mixing point located at the junction of the LP EGR line 249 and the intake passage 242.In some examples where an air intake system (AIS) throttle is included in the intake passage 242, dilution of the EGR flow may be adjusted upstream of the compressor 274 by adjusting the LP EGR valve 252 in coordination with the air intake system throttle.

[0052] A percentage dilution of the LP EGR flow may be derived from the output of a sensor in the engine intake gas stream. For example, a sensor 172 positioned downstream of the LP EGR valve 252 and upstream of the main intake throttle 262 may be used so that the LP EGR dilution can be precisely determined at or near the main intake throttle. The sensor 172 may be an oxygen sensor, for example. Additionally, during select conditions, the sensor 172 may be used to estimate the alcohol content of fuel delivered to the engine, as well as the alcohol content and composition of a knock control fluid delivered to cylinder 14.

[0053] The control device 12 is in Fig. 2 as a microcomputer including a microprocessor unit 206, input / output ports 208, an electronic storage medium for executable programs and calibration values, shown as a read-only memory chip 210 in this particular example, a random access memory 212, a keep-alive memory 214, and a data bus.Controller 12 may receive various signals from sensors coupled to engine 10 in addition to those previously analyzed signals, including measurements of induced mass air flow (MAF) from mass air flow sensor 222; engine coolant temperature (ECT) from temperature sensor 216 coupled to cooling sleeve 218; a profile ignition pickup (PIP) signal from a Hall effect sensor 220 (or other type) coupled to crankshaft 240; throttle position (TP) from a throttle position sensor; and a manifold absolute pressure (MAP) signal from sensor 224. The engine speed signal RPM may be generated by controller 12 based on the PIP signal. The manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of intake manifold vacuum or pressure.Still other sensors may include fuel level sensors and fuel composition sensors coupled to the fuel tank(s) of the fuel system. The controller 12 may also receive an operator request for windshield wipers via a dedicated sensor (not shown). In response to the signals received from the various sensors, the controller may actuate various engine actuators. Example actuators include a fuel injector 266, a wiper motor 72, a wiper injector 74, a throttle 262, cams 251 and 253, etc. The storage medium read-only memory 210 may be programmed with computer-readable data representing instructions executable by a processor 206 for performing the previously described methods, as well as other variations anticipated but not specifically listed.Example routines that can be performed are with respect to . Fig. 4-5 listed.

[0054] Next, Fig. 3 is a schematic view of an exemplary embodiment of an oxygen sensor 300 configured to measure a concentration of oxygen (O2) in an intake air charge stream. The sensor 300 may, for example, be configured as the intake oxygen sensor 172 of the Fig. 1-2 or as exhaust gas oxygen sensor 226 of FIG. 1-2. The sensor 300 comprises multiple layers of one or more ceramic materials arranged in a stacked configuration. In the embodiment of Fig. 3, five ceramic layers are illustrated as layers 301, 302, 303, 304, and 305. These layers include one or more layers of a solid electrolyte capable of conducting ionic oxygen. Examples of suitable solid electrolytes include, but are not limited to, zirconium-oxygen-based materials. Further, in some embodiments, a heater 307 may be disposed in thermal communication with the layers to increase the ionic conductivity of the layers. Although the illustrated oxygen sensor is formed from five ceramic layers, it is understood that the oxygen sensor may include other suitable numbers of ceramic layers.

[0055] Layer 302 includes a material or materials that create a diffusion pathway 310. Diffusion pathway 310 is configured to introduce inlet gases into a first internal cavity 322 via diffusion. Diffusion pathway 310 may be configured to allow one or more components of exhaust gases, which may include, but are not limited to, a desired analyte (e.g., O2), to diffuse into the internal cavity 322 at a more restrictive rate than the analyte can be pumped in or out by the pair of pumping electrodes 312 and 314. This allows a stoichiometric level of O2 to be maintained in the first internal cavity 322.

[0056] The sensor 300 further includes a second internal cavity 324 within layer 304, separated from the first internal cavity 322 by layer 303. The second internal cavity 324 is configured to maintain a constant oxygen partial pressure corresponding to a stoichiometric condition, e.g., an oxygen level present in the second internal cavity 324 corresponds to that which the exhaust gas would have if the air-fuel ratio were stoichiometric. Herein, the second internal cavity 324 may be referred to as a reference cell. As shown, the reference voltage is variable (e.g., between 0 and 1300 mV).

[0057] A pair of sensing electrodes 316 and 318 are arranged in communication with the first internal cavity 322 and the reference cell 324. The pair of sensing electrodes 316 and 318 sense a concentration gradient that may develop between the first internal cavity 322 and the reference cell 324 due to an oxygen concentration in the intake air that is higher or lower than the stoichiometric level. A high oxygen concentration may be caused by a lean charge mixture, while a low oxygen concentration may be caused by a rich charge mixture.

[0058] A pair of pumping electrodes 312 and 314 are arranged in communication with the internal cavity 322 and are configured to electrochemically pump a selected gas component (e.g., O2) from the internal cavity 322 through the layer 301 and out of the sensor 300. Alternatively, the pair of pumping electrodes 312 and 314 may be configured to electrochemically pump a selected gas through the layer 301 and into the internal cavity 322. Herein, the pair of pumping electrodes 312 and 314 may be referred to as an O2-pumping cell.

[0059] Electrodes 312, 314, 316, and 318 may be made from a variety of suitable materials. In some embodiments, electrodes 312, 314, 316, and 318 may be made at least partially from a material that catalyzes the decomposition of molecular oxygen. Examples of such materials include, but are not limited to, electrodes containing platinum and / or silver.

[0060] The process of electrochemically pumping oxygen into or out of the inner cavity 322 involves applying a voltage V p across the pair of pumping electrodes 312 and 314. The pumping voltage V p , which is applied to the O2-pumping cell, pumps oxygen into or out of the inner cavity 322 to maintain a stoichiometric level of oxygen in the pumping cell of the cavity. The resulting pumping current I pis proportional to the concentration of oxygen in the exhaust gas. A control system (in Fig. 3 not shown) generates the pump current signal I p as a function of the strength of the applied pump voltage V p , which is required to maintain a stoichiometric level within the first cavity 322. Thus, a lean mixture will result in oxygen being pumped out of the inner cavity 322, and a rich mixture will result in oxygen being pumped into the inner cavity 322. Furthermore, the output gain of the pumping current can be varied via the variable operational amplifier (e.g., op-amp). By varying the reference voltage and the output gain of the op-amp, the oxygen sensor can provide a higher-resolution signal.

[0061] It should be understood that the oxygen sensor described herein is merely one exemplary embodiment of an oxygen sensor and that other embodiments of oxygen sensors may include additional and / or alternative features and / or configurations.

[0062] With reference to Fig. 4 is an exemplary routine 400 for using an intake oxygen sensor (such as sensor 172 of the Fig. 1-2) for estimating the alcohol content and / or composition of an injected windshield washer fluid based on a change in the pumping current of the inlet oxygen sensor. This method enables precise determination of the composition of the windshield washer fluid without the need for additional sensors.

[0063] At 402, the method includes estimating and / or measuring engine operating conditions. These include, for example, engine speed, engine load, boost, ambient conditions (temperature, pressure, humidity), EGR, air-fuel ratio, etc.

[0064] At 404, it may be determined whether the windshield washer fluid has recently been refilled in the windshield washer fluid reservoir. In particular, the windshield washer fluid composition estimation may be triggered by a recent windshield washer fluid refill event. This allows the composition of the available windshield washer fluid to be accurately known. Consequently, the windshield washer fluid may be more reliably used for knock control in addition to wiper washing functions. In other examples, the composition may be estimated in response to an operator request for windshield washer fluid composition estimation. For example, the composition of the windshield washer fluid may be determined periodically, such as once for each threshold distance of vehicle travel, once for each duration of engine operation of vehicle travel, once for each threshold number of engine cycles, etc.

[0065] Herein, the windshield washer fluid (also referred to as windshield washer fluid or simply washer fluid) is a water-alcohol mixture that does not contain gasoline. In other words, the alcohol is the only hydrocarbon source in the washer fluid. In one example, the alcohol in the water-alcohol mixture is one or more of ethanol, methanol, propanol, isopropanol, etc. It should be understood that while the present routine illustrates the composition estimation of a washer fluid to enable the fluid to also be utilized as a knock control fluid, this is not meant to be limiting, and in other examples, the composition of an engine coolant fluid may be determined through use of the intake oxygen sensor to enable the fluid to also be utilized as a knock control fluid.

[0066] If the windshield washer fluid has not been replenished in the reservoir, or if other windshield washer fluid composition estimation conditions have not been met, then at 424 the method includes continuing to operate the intake oxygen sensor as an oxygen sensor. Further, one or more engine operating parameters are adjusted based on the oxygen sensor output. As non-limiting examples, the intake oxygen sensor output may be used for EGR estimation and control, as well as air-fuel ratio combustion control. For example, based on the estimated oxygen concentration of the intake air charge, an amount of EGR supplied to the engine intake may be adjusted (e.g., to provide a desired engine dilution or combustion air-fuel ratio).As another example, the cylinder fuel supply can be adjusted based on the estimated oxygen concentration of the intake air charge.

[0067] If the windshield washer fluid in the reservoir has been replenished, or if other windshield washer fluid composition estimation conditions have been met, then at 406 the method includes injecting an amount (also referred to herein as an injection mass) of the windshield washer fluid into the intake passage downstream of the intake throttle (and upstream of the intake valve). In one example, the injection mass is set to be an amount that will provide a significant change in the intake oxygen sensor output.

[0068] At 408, a transfer function for the windshield washer fluid may be determined based on the intake manifold airflow level (as determined based on the output of a MAF sensor, for example) and the windshield washer fluid injection mass. The transfer function may represent an expected change in the intake oxygen sensor pumping current with the injection mass for a given reference voltage. This change is then compared to a zero oxygen concentration measurement when no washer fluid is injected. Similarly, the manifold airflow may be interpreted by a MAP sensor and a lookup table that determines the mass air flow velocity in a velocity-density system. At 410, a first pumping voltage (also referred to herein as the reference voltage) (V1) is applied to the oxygen sensor.The first pumping voltage may be a lower reference voltage that pumps oxygen from the oxygen pumping cell, but may have a value low enough to not split water molecules (e.g., H2O molecules) in the pumping cell (e.g., V1 = 450 mV). When the first voltage is applied to the pumping cell, a first pumping current (I1) may be generated. In this example, the first pumping current may indicate an amount of oxygen that has either reacted with the sensing element of the oxygen sensor or has been displaced due to the dilution effect of water as windshield washer fluid is injected into the engine intake manifold.

[0069] At 412, the method includes determining the composition of the windshield washer fluid based on the output of the intake oxygen sensor. In particular, the change in the sensor's pumping current following application of the lower pumping voltage may be monitored, and a controller may estimate the composition of the windshield washer fluid by determining a first portion of the change in the pumping current due to a water content of the fluid, while determining a second portion of the change in the pumping current due to an alcohol content of the mixture. In particular, an alcohol content (e.g., an alcohol percentage) in the windshield washer fluid is determined based on the change in the sensor pumping current and further based on the fluid injection mass (as injected at 406).Estimating an alcohol content of the water-alcohol mixture includes, at 414, finding a first portion of the change in pumping current due to a water content of the mixture and, at 416, finding a second portion of the change in pumping current due to an alcohol content of the mixture.

[0070] In one example, an amount of water in the sample can be determined based on the first pump current and the transfer function. The amount of alcohol can then be identified based on the estimated water content. Since ambient humidity can also contribute to the amount of water in the intake charge, an ambient humidity estimate (as determined by a dedicated humidity sensor or detected by an intake or exhaust oxygen sensor during selected conditions) can be subtracted from the determined amount of water.In some embodiments, the computer-readable storage medium of the control system receiving communication from the sensor may include instructions for identifying the amount of alcohol by referring to a graph illustrating examples of the relationship between the change in oxygen sensor output and injection mass with a change in the percentage alcohol content of the windshield washer fluid (as described below with respect to . Fig. 6), wherein the graphic data is stored, for example, in the computer-readable storage medium in the form of a lookup table. Therein, the amount of water estimated by the intake oxygen sensor may decrease accordingly as the amount of alcohol (e.g., ethanol or methanol) in the injected windshield washer fluid increases. As in Fig. As shown in Figure 6, for a given mass of washer fluid injected into the intake air stream, a larger change (Delta) in the intake oxygen sensor output will reflect a higher methanol-to-water ratio. Consequently, the change in oxygen percentage (Delta_O2%) will be closer to the 100% MeOH line, and the engine controller can determine / label the line with a constant methanol concentration corresponding to that operating point.

[0071] In particular, applicants have recognized that the effect of the water component of the water-alcohol mixture on the intake oxygen sensor pumping current differs from the effect of the alcohol component (including the alcohol content and alcohol type) of the water-alcohol mixture on the intake oxygen sensor pumping current. For example, injecting 1% water (by volume) into intake air results in a 0.2% reduction in the oxygen concentration measured by the intake oxygen sensor due to its dilution effect on the oxygen concentration. However, injecting 1% methanol (by volume) into intake air results in a 1.5% reduction in the oxygen concentration measured by the intake oxygen sensor due to methanol combustion with the oxygen at the sensing element of the oxygen sensor, as indicated below. CH3OH + 1.5O2 = CO2 + H2O

[0072] Therefore, if 2% of the scrubbing liquid (water+methanol) mixture is injected, this will result in a total oxygen reduction of 2.5% (in this example), with 0.2 / 1.7 or 11.7% of this reduction being due to water and the remaining 1.5 / 1.7 or 88.3% of this reduction being due to methanol.

[0073] Thus, determining the first part may include determining a first value of the methanol-water concentration in the mixture (based on the change in pumping current). Furthermore, determining the second part may include determining a second value of the methanol-water concentration in the mixture, which is determined based on the monitored change in pumping current and further based on the amount of injected water-alcohol mixture. Herein, the second value may reflect a baseline oxygen concentration in the ambient air. Additionally, the controller may compare the first value with the second value.

[0074] As an example, the control device may refer to a lookup table or a map, such as the exemplary map of Fig. 6, to determine the percentage of alcohol in the knock control fluid. The map may be a 3D map that requires two inputs, the mass of injected fluid and the change in intake oxygen sensor pumping current, to provide an output regarding the percentage of alcohol in the injected knock control fluid.

[0075] With reference to Fig. 6, map 600 illustrates such an example map. In particular, map 600 illustrates a change in the intake oxygen sensor along the y-axis (Delta_O2%) and the washer fluid injection mass (M_washer_fluid_inj) along the y-axis. Here, the washer fluid is a water-methanol mixture that does not contain gasoline. The map is calibrated for 0% methanol (MeOH) and 100% methanol, as well as one or more intermediate methanol percentages. As can be seen, for a given injection mass, a larger change in the oxygen sensor output is observed with increasing methanol content. In other words, using the map, the methanol percentage (Methanol_pct) can be estimated as follows: Methanol_pct = fn(Delta_O2, M_washer_fluid_inj). Thus, using a map such as the map of Fig. 6, a control device must be able to estimate the alcohol (e.g. methanol) content of the injected windshield washer fluid.

[0076] With reference to Fig. 4, the composition of the windshield washer fluid from a water-alcohol mixture is based on the determined first part and second part, as well as on the injection quantity. That is, the composition of the water-alcohol mixture can be determined and updated based on the alcohol content of the windshield washer fluid from a water-alcohol mixture.

[0077] At 418, after determining the composition of the windshield washer fluid, an octane value of the fluid is updated. Additionally, a fuel octane estimate for the engine system may be updated. For example, an octane modification duration may be updated when used during knock feedforward control. In one example, updating includes increasing the octane value when the alcohol (ethanol or methanol) content of the windshield washer fluid increases or when the water content of the windshield washer fluid decreases.

[0078] At 420, after confirming the composition of the windshield washer fluid, the fluid may be used as a knock control fluid, if desired. For example, in response to a knock indication or in anticipation of potential knock, an amount of windshield washer fluid may be injected based on the engine octane demand (to address knock) relative to the fluid's updated octane rating.

[0079] At 422, one or more engine operating parameters are adjusted based on the updated windshield washer fluid and fuel octane estimate. For example, a base spark timing may be adjusted (e.g., extended from MBT). As another example, a marginal spark value may be adjusted (e.g., extended). As yet another example, one or more of an EGR schedule, VCT schedule, variable compression ratio, dual fuel injection schedule, etc. may be adjusted.

[0080] After completing the windshield washer fluid composition estimation by the intake oxygen sensor, the method may return to 424, where operation of the sensor may resume for oxygen sensing for purposes of EGR control, air-fuel ratio control, and the like.

[0081] This allows for improved windshield washer fluid composition estimation, allowing the fluid's use to be expanded to other functions. For example, composition estimation may enable improved use of windshield washer fluid outside of windshield wiping or engine coolant outside of engine cooling. In particular, the windshield washer fluid and / or engine coolant may be used more reliably and consistently as a knock control fluid to treat knock. By improving the use of a water-alcohol mixture in knock mitigation, fuel octane requirements can be reduced while treating knock, allowing more power to be extracted from the engine. Additionally, fuel economy benefits are achieved by reducing the need for spark retard.

[0082] With reference to Fig. 5 is an exemplary routine 500 for using an outlet oxygen sensor (such as sensor 225 of Fig. 1-2) for estimating the alcohol content and / or composition of an injected windshield washer fluid based on a change in the pumping current of the outlet oxygen sensor. This method enables precise determination of the composition of the windshield washer fluid without the need for additional sensors.

[0083] At 502, the method includes estimating and / or measuring engine operating conditions. These include, for example, engine speed, engine load, boost, ambient conditions (temperature, pressure, humidity), EGR, air-fuel ratio, etc.

[0084] At 504, it may be determined whether the windshield washer fluid has recently been refilled in the windshield washer fluid reservoir. In particular, the windshield washer fluid composition estimation may be triggered by a recent windshield washer fluid refill event. This allows the composition of the available windshield washer fluid to be accurately known. Consequently, the windshield washer fluid may be more reliably used for knock control in addition to wiper washing functions. In other examples, the composition may be estimated in response to an operator request for windshield washer fluid composition estimation. For example, the windshield washer fluid composition may be determined periodically, such as once for each threshold distance of vehicle travel, once for each duration of engine operation or vehicle travel, once for each threshold number of engine cycles, etc.

[0085] Herein, the windshield washer fluid (also called windshield washer fluid or simply washer fluid) is a water-alcohol mixture that does not contain gasoline. In other words, the alcohol is the only hydrocarbon source in the washer fluid. In one example, the alcohol in the water-alcohol mixture is one or more of ethanol, methanol, propanol, isopropanol, etc. It should be understood that while the present routine represents the composition estimation of a washer fluid to enable the fluid to also be used as a knock control fluid, this is not meant to be limiting, and in other examples, the composition of an engine coolant fluid may be determined through use of the intake oxygen sensor to enable the fluid to also be used as a knock control fluid.

[0086] If the windshield washer fluid has not been replenished in the reservoir, or if other windshield washer fluid composition estimation conditions have not been met, then at 540, a determination may be made as to whether fueling conditions exist. Fueling conditions include vehicle acceleration conditions and engine operating conditions where fueling is uninterrupted and the engine continues to rotate with at least one intake valve and one exhaust valve in operation; and with air flowing through one or more of the cylinders. Under fueling conditions, combustion is performed in the combustion chamber, and ambient air may move through the cylinder from the intake to the exhaust.

[0087] By comparison, unfueled conditions include vehicle deceleration conditions and engine operating conditions where 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 unfueled conditions, combustion is not performed, but ambient air can move through the cylinder from the intake to the exhaust.

[0088] If the fueling conditions are confirmed at 542, the method includes determining whether sensor-based air-fuel ratio feedback control or sensor-based alcohol detection is desired or to be performed. The selection may be based on operating conditions, such as a duration since a last alcohol determination or whether closed-loop air-fuel ratio control is enabled. For example, if air-fuel ratio feedback control is disabled, the routine may continue to determine alcohol content, whereas if air-fuel ratio feedback is commanded or enabled, the routine may continue to perform such air-fuel ratio feedback control (without determining alcohol content).If it is determined that feedback control is desired, or if fueling conditions are not confirmed at 540, the method moves to 550 and the sensor is operated as an outlet oxygen (e.g., O2) sensor to determine an oxygen concentration and / or an air-fuel ratio of the exhaust gas. Further, one or more engine operating parameters are adjusted based on the oxygen sensor output. As non-limiting examples, the outlet oxygen sensor output may be used for EGR estimation and control, as well as air-fuel ratio combustion control. The routine then ends.

[0089] If alcohol detection is desired, the method proceeds to 544, where it is first confirmed that the exhaust gas recirculation (EGR) valve is already closed (otherwise, the valve is actively closed). This ensures that the amount of EGR entering the combustion chamber is substantially zero. Next, the method includes modulating a reference voltage applied to the exhaust gas sensor. Specifically, a first pumping voltage (V1) and a second pumping voltage (V2) are applied sequentially to the exhaust gas sensor. The first pumping voltage may pump oxygen from the oxygen pumping cell, but may have a value low enough not to split water (e.g., H2O) molecules in the pumping cell (e.g., V1 = 450 mV). In some examples, the first pumping voltage applied to the sensor at 544 may be the same as the first pumping voltage applied to the sensor at 410 in Fig. 4 is applied. When the first voltage is applied to the pumping cell, a first pumping current (I1) may be generated. In this example, the first pumping current may indicate an amount of oxygen in the exhaust gas as fuel is injected into the engine and combustion occurs.

[0090] The second pumping voltage (V2) applied to the pumping cell of the exhaust gas sensor may be higher than the first pumping voltage, and the second voltage may be high enough to cleave oxygen compounds, such as water molecules. Applying the second pumping voltage across the oxygen pumping cell may generate a second pumping current (I2). The second pumping current may indicate an amount of oxygen and water in the sample gas (e.g., oxygen already present in the sample gas and oxygen from water molecules that are cleaved when the second pumping voltage is applied).

[0091] After the first and second pumping currents are generated, an alcohol content of the fuel may be determined based on an amount of water in the sample gas at 546. For example, the first pumping current may be subtracted from the second pumping current to determine a value corresponding to an amount of water. The amount of alcohol in the fuel may then be identified. For example, the amount of water in the exhaust gas may be proportional to an amount of alcohol (e.g., a percentage of ethanol) in the fuel injected into the engine. Since ambient humidity may also contribute to an amount of water in the exhaust gas, an ambient humidity estimate may be subtracted from the determined amount of water.In some embodiments, the computer-readable storage medium of the control system that receives communication from the sensor may include instructions for characterizing the amount of alcohol based on a lookup table that uses the change in pump current as an input.

[0092] After determining the fuel alcohol content of the injected fuel at 548, a fuel octane estimate is updated. For example, an octane modification duration may be updated when used during knock feedforward control. In one example, updating includes increasing the fuel octane estimate as the alcohol content of the injected fuel increases. Further, one or more engine operating parameters are adjusted based on the updated fuel octane estimate. For example, an applied base spark timing may be adjusted (e.g., extended from MBT). As another example, a marginal spark value may be adjusted (e.g., extended). As yet another example, engine EGR timing may be adjusted.

[0093] Referring to 504, the windshield washer fluid is replenished, or if other windshield washer fluid composition estimation conditions have been met, then at 506 the method includes injecting an amount (also referred to herein as the injection mass) of the windshield washer fluid into the engine. In one example, the windshield washer fluid may be injected into the intake passage downstream of the intake throttle (and upstream of the exhaust valve). In another example, an engine fuel injector may inject the windshield washer fluid directly within the cylinder. Herein, the fluid may be injected and combusted within the cylinder, as the washer fluid composition is to be detected using the exhaust gas.In one example, the windshield washer fluid injection injection mass is set to be an amount that will provide a significant change in the outlet oxygen sensor output.

[0094] At 508, a transfer function for the windshield washer fluid may be determined based on the intake manifold airflow level (as determined, for example, based on the output of a MAF sensor) and the windshield washer fluid injection mass. The transfer function may represent an expected change in the exhaust oxygen sensor pumping current with the injection mass for a given reference voltage. Similarly, the manifold airflow may be interpreted from a MAP sensor and a lookup table that determines the mass airflow velocity in a velocity-density system.

[0095] While the engine is being fueled and the cylinders are performing combustion, the method includes determining at 510 whether the amount of positive crankshaft ventilation (PCV) is at a desired level. Herein, the desired level may include a PCV that is less than a threshold amount. In one example, it may be desirable to have substantially no PCV flow. As an example, increased PCV flow from the engine crankshaft into the intake manifold may be present when the engine is operating at a higher speed range. Other example conditions where PCV flow is increased include increased manifold vacuum conditions, increased crankshaft pressure conditions, high ambient temperature conditions, combinations thereof, etc.Therefore, the windshield washer fluid alcohol content estimation may only be enabled during conditions when the PCV flow is lower than a threshold level (e.g., when the PCV is disabled) to reduce interference from PCV hydrocarbons.

[0096] If the PCV flow is above the desired level (e.g., the PCV flow is high), the method returns to 550, where the sensor is operated as an outlet oxygen sensor, for example, to determine an intake air oxygen concentration for air-fuel control, and the routine ends.

[0097] On the other hand, if the PCV is at a desired level (e.g., PCV flow is low), the method proceeds to 512, where it is determined whether the exhaust gas recirculation (EGR) valve is closed. If it is determined that the EGR valve is open, the method moves to 514, and the EGR valve is closed. As such, the windshield washer fluid alcohol content estimation may only be enabled during conditions when the EGR flow is lower than a threshold (e.g., when EGR is disabled) to reduce interference from EGR hydrocarbons.

[0098] After the EGR valve is closed, or if it is determined that the EGR valve is closed at 512, and thus the amount of EGR entering the combustion chamber is substantially zero, the method proceeds to 516, where it is determined whether the fuel vapor purge valve is closed. If it is determined that the fuel vapor purge valve is open, the method moves to 518 and the fuel vapor purge valve is closed. The fuel vapor stored in the fuel vapor canister may also have an alcohol content and may degrade the results of a windshield washer fluid composition estimation. In particular, the fuel vapor entering the combustion chamber may affect the amount of alcohol detected by the outlet oxygen sensor, resulting in an inaccurate estimate.Thus, the windshield washer fluid composition estimation can only be activated during conditions when the purge flow is less than a threshold level (e.g., when canister purge is disabled). By recording the outlet oxygen sensor's response to the injection of a knock control fluid in the absence of EGR, PCV, or purge, a more accurate estimate of the air-fuel ratio of the injected water-alcohol mixture is achieved. Therefore, this provides an improvement in fuel economy and engine system performance.

[0099] After the fuel vapor purge valve is closed at 518, or if it is determined that the fuel vapor purge valve is closed at 516, the method proceeds to 520, where the method includes modulating a reference voltage of the outlet oxygen sensor. Modulating includes alternating the oxygen sensor reference voltage between a first voltage and a second voltage, wherein the first and second voltages are applied sequentially. In particular, a first pumping voltage (V1) may initially be applied to the outlet oxygen sensor. The first pumping voltage may pump oxygen from the oxygen pumping cell, but may have a value low enough to not split water (e.g., H2O) molecules in the pumping cell (e.g., V1 = 450 mV).In some examples, the first pumping voltage applied to the sensor for estimating the alcohol content of the windshield washer fluid may be the same as the first pumping voltage applied to the sensor for estimating the alcohol content of the injected fuel (as detailed at 544). When the first voltage is applied to the pumping cell, a first pumping current (I1) may be generated. In this example, the first pumping current may indicate an amount of oxygen in the air charge.

[0100] Modulating then involves applying a second pump voltage (V2) to the pump cell of the outlet oxygen sensor. The second pump voltage may be higher than the first pump voltage, and the second voltage may be high enough to cleave oxygen compounds, such as water molecules (e.g., V2 = 950 or 1050 mV). Applying the second pump voltage across the oxygen pump cell may generate a second pump current (I2). The second pump current may indicate an amount of oxygen and water in the sample gas (e.g., oxygen already present in the sample gas and oxygen from water molecules that are cleaved when the second pump voltage is applied).

[0101] After the first and second pumping currents are generated, a change in the sensor's pumping current is monitored. At 522, an alcohol content of (e.g., a percentage of alcohol in) the windshield washer fluid is estimated based on the change in the sensor pumping current and further based on the fluid injection mass (as injected at 506). Estimating an alcohol content of the water-alcohol mixture includes, at 524, determining a first portion of the change in the pumping current due to a water content of the mixture and, at 526, determining a second portion of the change in the pumping current due to an alcohol content of the mixture.

[0102] In one example, an amount of water in the sample may be determined by subtracting the first pumping current from the second pumping current. The amount of alcohol in the windshield washer fluid may then be identified based on the estimated water content. For example, the amount of water in the fluid may be proportional to an amount of alcohol (e.g., a percentage of ethanol or methanol) in the injected water-alcohol mixture. Since ambient humidity may also contribute to an amount of water in the intake charge, an ambient humidity estimate (as determined by a dedicated humidity sensor or sensed by an exhaust gas oxygen sensor or the intake oxygen sensor during other selected conditions) may be subtracted from the determined amount of water.In some embodiments, the computer-readable storage medium of the control system receiving communication from the sensor may include instructions for characterizing the amount of alcohol by reference to a graph illustrating examples of the relationship between a change in oxygen sensor output and mass injection water with a change in the percentage alcohol content of a knock control fluid (as previously discussed with respect to . Fig. 6), wherein the graphic data is stored, for example, in the computer-readable storage medium in the form of a lookup table. Therein, the amount of water estimated by the intake oxygen sensor may decrease accordingly as the amount of alcohol (e.g., ethanol or methanol) in the injected windshield washer fluid increases. As described in Fig. As shown in Figure 6, for a given mass of washer fluid injected into the intake airflow or the engine cylinder, a larger change (delta) in the oxygen sensor output will reflect a larger methanol-to-water ratio; in this case, the Delta_O2% will be closer to the 100% MeOH line, and the engine controller can determine the line with a constant methanol concentration corresponding to that operating point. In particular, applicants have recognized that the effect of the water component of the water-alcohol mixture on the outlet oxygen sensor pumping current differs from the effect of the alcohol component (including the alcohol content and alcohol type) of the water-alcohol mixture on the outlet oxygen sensor pumping current.For example, injecting 1% water (by volume) into the intake air results in a 0.2% reduction in the oxygen concentration measured by the outlet oxygen sensor due to its dilution effect on the oxygen concentration. However, injecting 1% methanol (by volume) into the intake air results in a 1.5% reduction in the oxygen concentration measured by the outlet oxygen sensor due to methanol combustion with the oxygen at the sensing element of the oxygen sensor, as indicated below. CH3OH + 1.5O2 = CO2 + H2O

[0103] Therefore, if 2% of the windshield washer fluid (water+methanol) mixture is injected, this will result in a total oxygen reduction of 2.5% (in this example), with 0.2 / 1.7 or 11.7% of this reduction being due to water and the remaining 1.5 / 1.7 or 88.3% of this reduction being due to methanol.

[0104] Thus, determining the first part may include determining a first value of the methanol-water concentration in the mixture (based on the change in pumping current). Furthermore, determining the second part may include determining a second value of the methanol-water concentration in the mixture, which is determined based on the monitored change in pumping current and further based on the amount of injected water-alcohol mixture. Herein, the second value may reflect a baseline oxygen concentration in the ambient air. Additionally, the controller may compare the first value with the second value.

[0105] As an example, the control device may refer to a lookup table or a map, such as the exemplary map of Fig.6, to determine the percentage of alcohol in the knock control fluid. As previously analyzed, the map can be a 3D map that requires two inputs: the mass of fluid being injected and the change in the outlet oxygen sensor pump current to provide an output regarding the percentage of alcohol in the injected windshield washer fluid.

[0106] It should be understood that in other examples, the windshield washer fluid estimation using the exhaust oxygen sensor may be performed during an engine non-fueling condition where at least one intake valve and one exhaust valve are operating. For example, the modulation may be performed during a deceleration fuel shut-off (DFSO) event.

[0107] At 528, after determining the composition of the windshield washer fluid, an octane value of the fluid is updated. Additionally, a fuel octane estimate for the engine system may be updated. For example, an octane modification duration may be updated when used during knock feedforward control. In one example, updating includes increasing the octane value when the alcohol (ethanol or methanol) content of the windshield washer fluid increases or when the water content of the windshield washer fluid decreases.

[0108] At 530, after confirming the composition of the windshield washer fluid, the fluid may be used as a knock control fluid, if desired. For example, in response to a knock indication or in anticipation of potential knock, an amount of windshield washer fluid may be injected based on the engine octane demand (to address knock) relative to the fluid's updated octane rating.

[0109] At 532, one or more engine operating parameters are adjusted based on the updated windshield washer fluid and fuel octane estimate. For example, an employed base spark timing may be adjusted (e.g., extended from MBT). As another example, the marginal spark value may be adjusted (e.g., extended). As yet another example, one or more of engine EGR timing, VCT timing, variable compression ratio, dual fuel injection timing, etc. may be adjusted.

[0110] After completing the windshield washer fluid composition estimation by the outlet oxygen sensor, the method may return to 550, where operation of the sensor may resume for oxygen sensing for purposes of EGR control, air-fuel ratio control, and the like.

[0111] This allows the composition of a windshield washer fluid and an injected fuel to be determined using an outlet oxygen sensor. For example, during a first condition, a water-alcohol mixture can be injected into an engine cylinder, and an alcohol composition of the water-alcohol mixture can be determined based on a change in the pumping current of the outlet oxygen sensor. Then, during a second condition, a gasoline-alcohol mixture can be injected into a fuel cylinder, and an alcohol composition of the gasoline-alcohol mixture can be determined based on a change in the pumping current of the outlet oxygen sensor. By accurately and reliably determining the alcohol content and composition of a windshield washer fluid, the use of the fluid for knock control can be expanded, improving the robustness of the engine system.By using the same oxygen sensor to estimate the alcohol content of the knock control fluid and the alcohol content of the injected fuel, the need for a dedicated sensor to determine the composition of the knock control fluid is reduced.

[0112] An exemplary engine method includes: injecting an amount of a water-alcohol mixture; applying a reference voltage to an intake oxygen sensor; monitoring a change in the sensor's pumping current; detecting a first portion of the change in the pumping current due to a water content of the mixture; and detecting a second portion of the change in the pumping current due to an alcohol content of the mixture. The previous example may additionally or optionally further include detecting a composition of the mixture based on the detected first portion and second portion, and further based on the injection amount.Any or all of the previous examples may additionally or optionally further include adjusting an engine operating parameter based on the determined composition, wherein the engine operating parameter includes one or more of a fuel octane estimate and a fuel injection amount. In any or all of the previous examples, the mixture may additionally or optionally further include no gasoline, wherein the alcohol includes one or more of ethanol and methanol. In any or all of the previous examples, applying may additionally or optionally further include applying a first, lower voltage that does not split water molecules.In any or all of the preceding examples, determining the first part additionally or optionally further includes determining a first value of the water-methanol composition in the mixture based on the change in pumping current. In any or all of the preceding examples, determining the second part additionally or optionally further includes determining a second value of a methanol-water concentration in the mixture, determined based on the monitored change in pumping current and further based on the amount of injected water-alcohol mixture, and comparing the first value with the second value. Herein, the second value may reflect a baseline concentration of oxygen in the ambient air.In any or all of the preceding examples, the method is additionally or optionally performed when selected conditions are met, wherein the selected conditions additionally or optionally include the following refilling of the water-alcohol mixture in a reservoir. In any or all of the preceding examples, the water-alcohol mixture additionally or optionally includes one of windshield washer fluid and engine coolant.

[0113] Another example method for an engine includes: during a first condition, injecting a water-alcohol mixture into an engine cylinder and determining an alcohol composition of the water-alcohol mixture based on a change in the pumping current of an intake oxygen sensor; and during a second condition, injecting a gasoline-alcohol mixture into the engine cylinder and determining the alcohol composition of the gasoline-alcohol mixture based on the change in the pumping current of the intake oxygen sensor. In the previous example, the first condition additionally or optionally includes replenishing the water-alcohol mixture in a washer fluid tank of the engine following engine operation, and the second condition additionally or optionally includes replenishing the gasoline-alcohol mixture in a fuel tank of the engine following engine operation.In any or all of the previous examples, additionally or optionally, during the second condition, a reference voltage of the intake oxygen sensor is modulated between a first and a second voltage, and the change in pumping current is responsive to the modulation. Additionally or optionally, in any or all of the previous examples, during the second condition, only the first reference voltage is applied to the intake oxygen sensor, and the change in pumping current is responsive to the application. In any or all of the previous examples, during the first condition, the alcohol composition of the water-alcohol mixture is additionally or optionally further based on an injection mass.In any or all of the preceding examples, during the first condition, determining an alcohol composition of the water-alcohol mixture additionally or optionally includes distinguishing a first portion of the change in pumping current due to a water content of the water-alcohol mixture from a second portion of the change in pumping current due to an alcohol content of the water-alcohol mixture. In any or all of the preceding examples, the water-alcohol mixture additionally or optionally includes a first alcohol in a first ratio to water, and the gasoline-alcohol mixture includes a second alcohol in a second ratio to gasoline, wherein the first alcohol is different from the second alcohol, wherein the first ratio is different from the second ratio.Any or all of the previous examples may additionally or optionally further include, during the first condition, adjusting a knock-reducing spark retard amount based on the determined alcohol composition of the water-alcohol mixture, and, during the second condition, adjusting an air-fuel ratio feedback control gain based on the determined alcohol composition of the gasoline-alcohol mixture.

[0114] Another exemplary engine system includes an engine having an intake manifold; a first fuel injector for injecting fuel into an engine cylinder; a second injector for injecting a knock control fluid into the intake manifold downstream of an intake throttle; an EGR system including a passage for recirculating exhaust residues from downstream of the turbine to upstream of the compressor via an EGR valve; an oxygen sensor coupled to the intake manifold, downstream of the intake throttle and downstream of the EGR valve; and a controller.The controller may be configured with computer-readable instructions stored in non-transitory memory to: inject an amount of knock control fluid into the cylinder; apply a lower reference voltage to the oxygen sensor; measure a change in pumping current of the oxygen sensor; and estimate a composition of the knock control fluid based on the injection amount and the measured change in pumping current. In the previous example, the knock control fluid additionally or optionally contains water and alcohol and no fuel, and the controller estimates the composition by calculating a first portion of the change in pumping current due to a water content of the knock control fluid and calculating a second portion of the change in pumping current due to an alcohol content of the knock control fluid.In any or all of the preceding examples, the controller additionally or optionally further includes instructions for updating a fuel octane estimate based on the estimated knock control fluid composition. In any or all of the preceding examples, the controller additionally or optionally further includes instructions for: adjusting each of an ignition timing and a marginal spark value applied in response to knock based on the updated fuel octane estimate, wherein the adjusting includes retarding ignition timing from a base spark timing and extending a marginal spark toward an MBT as the fuel octane estimate increases.

[0115] This allows the composition of a water-alcohol mixture knock control fluid to be accurately and reliably determined based on sensor outputs (e.g., pumping currents) generated in response to voltages applied to the oxygen pump cell of an engine system oxygen sensor during selected conditions. Specifically, a change in the sensor output can be correlated with the amount of alcohol in a windshield washer fluid or engine coolant. This allows a precise indication of the amount of alcohol (e.g., the percentage of ethanol or the percentage of methanol) in the fluid to be identified, allowing the fluid to be used additionally for knock control.Furthermore, after the composition type is determined, various engine operating parameters can be adjusted to maintain engine and / or emissions efficiency and improve the use of knock control ignition. The technical effect of improving the estimation of a composition of an injected knock control fluid is that the use of the knock control fluid can be expanded.

[0116] It should be noted that the example control and estimation routines included herein may be used with various machine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and may be executed by the control system, including the controller combined with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various illustrated actions, operations, and / or functions may be performed in the illustrated order, in parallel, or in some cases, omitted.Likewise, the order of processing is not necessarily required to achieve the features and advantages of the embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, the described actions, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the machine control system, wherein the described actions are performed by executing the instructions in a system including the various machine hardware components in combination with the electronic controller.

[0117] It is understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered limiting, as numerous variations are possible. For example, the above technology is applicable to V6, I4, I6, V12, horizontally opposed 4-cylinder, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or characteristics disclosed herein.

[0118] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims should be construed as encompassing the inclusion of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope than the original claims, are also considered to be included within the subject matter of the present disclosure.

Claims

[1] Engine process comprising: Injecting a quantity of a water-alcohol mixture; Applying a reference voltage to an intake oxygen sensor; Monitoring a change in the sensor pumping current; Finding a first part of the change in the pumping current due to a water content of the mixture; and Finding a second part of the change in pumping current due to an alcohol content of the mixture. [2] The method according to claim 1, further comprising finding a composition of the mixture based on the found first part and second part, and further based on the injection amount. [3] The method of claim 2, further comprising adjusting an engine operating parameter based on the determined composition, wherein the engine operating parameter includes one or more of a fuel octane estimate and a fuel injection amount. [4] The method of claim 1, wherein the mixture does not contain gasoline, and wherein the alcohol contains one or more of ethanol and methanol. [5] The method of claim 1, wherein applying includes applying a first lower voltage that does not split water molecules. [6] The method of claim 1, wherein the determining the first part includes determining a first value of a methanol-water concentration in the mixture. [7] The method of claim 6, wherein finding the second part includes: Determining a second methanol-water concentration in the mixture, which is found based on the monitored change in the pumping current and further based on the amount of injected water-alcohol mixture, the second value reflecting a baseline concentration of oxygen in the ambient air; and Comparing the first value with the second value. [8] The method of claim 1, wherein the method is performed in response to selected conditions identified, the selected conditions including replenishing the water-alcohol mixture in a storage container. [9] The method of claim 1, wherein the water-alcohol mixture includes one of a windshield washer fluid and an engine coolant. [10] Power machine system comprising: an engine including an intake manifold; a first injection valve for injecting fuel into an engine cylinder; a second injector for injecting a knock control fluid into the intake manifold downstream of an intake throttle; an EGR system including a passage for recirculating exhaust gas residues from downstream of the turbine to upstream of the compressor via an EGR valve; an oxygen sensor coupled to the intake manifold, downstream of the intake throttle and downstream of the EGR valve; and a control device having computer-readable instructions stored on the non-volatile memory for: Injecting a quantity of knock control fluid into the cylinder; Applying a lower reference voltage to the oxygen sensor; Measuring a change in the pumping current of the oxygen sensor; and Estimating a knock control fluid composition based on the injection quantity and the measured change in pumping current. [11] The system of claim 10, wherein the knock control fluid contains water and alcohol and no fuel, and wherein the controller estimates the composition by calculating a first portion of the change in pumping current due to a water content of the knock control fluid and calculating a second portion of the change in pumping current due to an alcohol content of the knock control fluid. [12] The system of claim 10, wherein the control device includes further instructions for: Updating a fuel octane estimate based on the estimated knock control fluid composition. [13] The system of claim 12, wherein the control device includes further instructions for: Adjusting each a spark timing and a marginal spark value applied in response to knock based on the updated fuel octane estimate, wherein the adjusting includes retarding the spark timing from a base spark timing and extending the marginal spark toward an MBT as the fuel octane estimate increases.

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