Methods and systems for estimating PCV flow using an inlet oxygen sensor

Abstract

Method for a power machine (10) comprising the following: Setting an EGR valve (204) based on an output of an inlet oxygen sensor (172) and the PCV flow during operation with flowing EGR, wherein the PCV flow during the preceding operation with EGR blocked and draining is identified based on the outputs of the inlet oxygen sensor (172) with and without boost.

Description

[0001] Engine systems can utilize the recirculation of exhaust gas from an engine's exhaust system to an engine's intake system (intake port), a process known as exhaust gas recirculation (EGR), to reduce regulated emissions and improve fuel economy. An EGR system may include various sensors to measure and / or control the EGR. For example, the EGR system may include a sensor for the components of the intake gas, such as an oxygen sensor, which can be used during non-EGR conditions to determine the oxygen content of the fresh intake air. During EGR conditions, the sensor can be used to determine the EGR based on a change in oxygen concentration due to the addition of the EGR as a diluent. An example of such an intake oxygen sensor is shown by Matsubara et al. in US 6,742,379 B2.The EGR system may additionally or optionally include an exhaust gas oxygen sensor coupled to the exhaust manifold to estimate the air-fuel ratio of the combustion.

[0002] Further prior art is US Patent 2012 / 0037134A1. This describes a power machine system and a method for a power machine, comprising a control of exhaust gas recirculation in a turbocharged engine with an oxygen sensor, an EGR valve and a throttle valve.

[0003] US 2013 / 0191008A1 describes a method for a naturally aspirated engine in which the contributions to the dilution of an intake mixture from EGR, tank venting and crankcase venting are estimated using an oxygen sensor in various conditions.

[0004] US 2012 / 0 237 368 A1 provides a vacuum generation system for tank venting and crankcase venting.

[0005] Methods and a power machine system with the features of the independent claims are provided.

[0006] Due to the oxygen sensor's location downstream of an intercooler in a high-pressure air intake system, the sensor can be sensitive to the presence of fuel vapor and other reducing and oxidizing agents, such as oil mist. During supercharged engine operation, for example, exhaust air and / or crankcase gases may be received at a supercharger inlet. Hydrocarbons drawn from the exhaust air, PCV, and / or rich EGR can consume oxygen on the sensor's catalytic surface, reducing the oxygen concentration detected by the sensor. In some cases, the reducing agents can also react with the oxygen sensor's sensing element. The reduction in oxygen at the sensor can be misinterpreted as a dilution if the change in oxygen is used to estimate EGR.Consequently, the sensor measurements can be confused by the different sensitivities, the accuracy of the sensor can be reduced, and the measurement and / or control of the EGR can be impaired.

[0007] In one example, the problems described above can be addressed by a procedure for a power engine that includes: adjusting an EGR valve based on an intake oxygen sensor output and the PCV flow during operation with EGR flowing, where the PCV flow is identified during the preceding power engine operation with EGR blocked and under load, based on the intake oxygen sensor outputs with and without boost. This way, the effect of hydrocarbons on the sensor can be eliminated from the PCV flow, and the accuracy of the EGR estimation can be improved.

[0008] During engine operation, when the EGR is blocked (no EGR flow) and the drain is blocked (e.g., a fuel canister drain valve is closed), a correction factor for the intake oxygen sensor can be determined based on the PCV flow. Specifically, the correction factor can be based on a change in the intake oxygen concentration (or the intake oxygen reading) at the intake oxygen sensor between naturally aspirated and supercharged engine operation. This is because the PCV flow is received downstream of the intake oxygen sensor, directly in the intake manifold, when the engine is running naturally aspirated and with the drain blocked. Because the sensor output is not affected by the PCV hydrocarbons, it accurately reflects the intake oxygen concentration.When comparing operation with forced induction and blocked exhaust, the PCV flow is received in the air intake system upstream of the intake oxygen sensor. Here, the sensor output is influenced by the PCV hydrocarbons, reflecting the PCV flow. Therefore, by comparing the sensor outputs with and without forced induction, any change in intake oxygen resulting from the PCV flow can be determined and used to correct subsequent sensor outputs. For example, during subsequent engine operation, when the EGR is flowing and the fuel canister drain valve is closed, the intake manifold oxygen sensor output can be adjusted based on the correction factor. As a result, the PCV flow's contribution to the intake oxygen can be removed from the sensor output.The resulting set output can more accurately reflect the change in intake oxygen resulting from EGR. An EGR flow rate can be estimated based on the set output, and an EGR valve can be adjusted accordingly for improved EGR control. Estimating the EGR flow in this way can increase the accuracy of the EGR flow rate estimates, thereby improving the control of the EGR system and maintaining engine emissions at target levels.

[0009] It should be self-evident that the above summary is provided to introduce, in simplified form, a selection of the 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 clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate all the disadvantages stated above or in any part of this disclosure. Fig. Figures 1-2 are schematic graphical representations of a power machine system. Fig. Figure 3 is a graphical representation showing the effect of the exhaust air on the oxygen concentration estimated by an inlet manifold oxygen sensor. Fig. Figure 4 presents a procedure for determining a change in inlet oxygen resulting from the PCV flow. Fig. Figure 5 presents a procedure for adjusting the EGR operation based on a change in the intake oxygen due to the PCV flow. Fig. Figure 6 presents exemplary settings of the operating parameters of the engine based on the changes in the inlet oxygen resulting from the PCV flow.

[0010] The following description refers to systems and methods for using an inlet oxygen sensor to estimate the amount of EGR flow to a power engine system, such as the power engine system according to the Fig. 1-2. A controller can be configured to perform a control procedure, such as the procedure according to Fig. 4. To determine the amount of crankcase hydrocarbons (e.g., PCV) being drawn into an engine when EGR and the drain flow are blocked. Specifically, the PCV flow can be estimated based on sensor outputs displayed with and without boost. Based on the determined PCV flow, the EGR flow can then be adjusted. Engine operation, such as fuel delivery to the engine, can then be adjusted based on the estimated PCV flow. Both a sensor output and an EGR dilution estimated by the sensor can be adjusted to compensate for the effect of crankcase hydrocarbons on the sensor output. Fig. 3) As in Fig. As shown in Figure 5, during engine operation, when EGR is blocked, drain is blocked, and PCV is enabled, the controller can adjust the sensor output based on the detected amount of crankcase hydrocarbons (e.g., the PCV flow). This increases the accuracy of the EGR estimation using an intake oxygen sensor. Exemplary engine operating parameter settings based on changes in intake oxygen resulting from the PCV flow are shown in Figure 5. Fig. 6 shown.

[0011] Fig. Figure 1 shows a schematic representation of an exemplary turbocharged engine system 100, which includes a multi-cylinder internal combustion engine 10 and twin turbochargers 120 and 130. As a non-restrictive example, the engine system 100 can be included as part of a propulsion system for a passenger vehicle. The engine system 100 can receive intake air via an intake duct 140. The intake duct 140 can include an air filter 156 and an EGR throttle valve 230. The engine system 100 can be a split engine system in which the intake duct 140 branches downstream of the EGR throttle valve 230 into a first and a second parallel intake duct, each containing a turbocharger compressor.Specifically, at least a portion of the intake air is directed via a first parallel intake channel 142 to a compressor 122 of the turbocharger 120, and at least a further portion of the intake air is directed via a second parallel intake channel 144 of the intake channel 140 to a compressor 132 of the turbocharger 130.

[0012] The first portion of the total intake air, compressed by the compressor 122, can be fed to the intake manifold 160 via a first parallel branched intake channel 146. In this way, the intake channels 142 and 146 form a first parallel branch of the engine's air intake system. Similarly, a second portion of the total intake air can be compressed by the compressor 132 and fed to the intake manifold 160 via the second parallel branched intake channel 148. Consequently, the intake channels 144 and 148 form a second parallel branch of the engine's air intake system. As shown in Fig. As shown in Figure 1, the intake air from the intake ports 146 and 148 can be recombined via a common intake port 149 before reaching the intake manifold 160, where the intake air can be supplied to the engine.

[0013] A first EGR throttle valve 230 can be positioned in the engine intake upstream of the first and second parallel intake channels 142 and 144, while a second air intake throttle valve 158 can be positioned downstream of the first and second parallel intake channels 142 and 144 and downstream of the first and second parallel branched intake channels 146 and 148, e.g. in the common intake channel 149, in the engine intake.

[0014] In some examples, the intake manifold 160 may contain 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 of which is connected to a controller 12. The intake duct 149 may contain a charge air cooler (CAC) 154 and / or a throttle valve (such as a second throttle valve 158). The position of the throttle valve 158 can be adjusted by the control system via a throttle actuator (not shown) that is telematically coupled to the controller 12. An anti-pump valve 152 may be provided to selectively bypass the compressor stages of the turbochargers 120 and 130 via the bypass duct 150.As an example, the anti-pump valve 152 can be open to allow flow through the bypass channel 150 when the inlet air pressure upstream of the compressors reaches a threshold value.

[0015] The intake manifold 160 can further include an intake gas oxygen sensor 172. In one example, the oxygen sensor is a UEGO sensor. As elaborated here, the intake gas oxygen sensor can be configured to provide an estimate of the oxygen content of the fresh air received in the intake manifold. Furthermore, when the EGR flows, a change in the oxygen concentration at the sensor can be used to derive an EGR quantity and for precise control of the EGR flow. In the illustrated example, the oxygen sensor 172 is positioned upstream of the throttle valve 158 and downstream of the charge air cooler 154. In alternative embodiments, however, the oxygen sensor can be positioned upstream of the CAC. A pressure sensor 174 can be positioned adjacent to the oxygen sensor to estimate an intake pressure at which an output from the oxygen sensor is received.Because the oxygen sensor output is influenced by the intake pressure, a reference output from the oxygen sensor can be derived from a reference intake pressure. In one example, the reference intake pressure is a throttle-point intake pressure (TIP), where pressure sensor 174 is a TIP sensor. In alternative examples, the reference intake pressure is a manifold pressure (MAP), as measured by MAP sensor 182.

[0016] The engine 10 can contain multiple cylinders 14. In the example shown, the engine 10 contains six cylinders arranged in a V configuration. Specifically, the six cylinders are arranged in two rows 13 and 15, with each row containing three cylinders. In alternative examples, the engine 10 can contain two or more cylinders, such as 3, 4, 5, 8, 10, or more. These cylinders can be equally spaced and arranged in alternative configurations, such as V, in-line, boxer, etc. Each cylinder 14 can be configured with a fuel injector 166. In the example shown, the fuel injector 166 is a direct injector into the cylinder. However, in other examples, the fuel injector 166 can be configured as a channel-based fuel injector.

[0017] The intake air supplied to each cylinder 14 (also referred to here as a combustion chamber 14) via the common intake port 149 can be used for fuel combustion, with the combustion products then being discharged via row-specific parallel exhaust ports. In the example shown, a first row 13 of cylinders of the engine 10 can discharge the combustion products via a first parallel exhaust port 17, and a second row 15 of cylinders can discharge the combustion products via a second parallel exhaust port 19. Both the first and second parallel exhaust ports 17 and 19 can furthermore contain a turbocharger turbine.Specifically, the combustion products discharged through the exhaust port 17 can be routed through the exhaust turbine 124 of the turbocharger 120, which in turn can supply mechanical work to the compressor 122 via a shaft 126 to provide compression to the intake air. Alternatively, some or all of the exhaust gases flowing through the exhaust port 17 can bypass the turbine 124 via the turbine bypass port 123, as controlled by a boost pressure control valve 128. Similarly, the combustion products discharged through the exhaust port 19 can be routed through the exhaust turbine 134 of the turbocharger 130, which in turn can supply mechanical work to the compressor 132 via a shaft 136 to provide compression to 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 outlet channel 19 can bypass the turbine 134 via a turbine bypass channel 133, as controlled by a boost pressure control valve 138.

[0018] In some examples, the exhaust gas turbines 124 and 134 can be configured as variable geometry turbines, where the controller 12 can adjust the position of the blades (or vanes) of the turbine impeller to vary the energy level obtained from the exhaust gas flow and transferred to their respective compressors. Alternatively, the exhaust gas turbines 124 and 134 can be configured as variable nozzle turbines, where the controller 12 can adjust the position of the turbine nozzle to vary the energy level obtained from the exhaust gas flow and transferred to their respective compressors. The control system can, for example, be configured to change the blade or nozzle position of the exhaust gas turbines 124 and 134 independently via respective actuators.

[0019] The exhaust gases in the first parallel outlet channel 17 can be discharged to the atmosphere via the branched parallel outlet channel 170, while the exhaust gases in the second parallel outlet channel 19 can be discharged to the atmosphere via the branched parallel outlet channel 180. Outlet channels 170 and 180 can contain one or more exhaust aftertreatment devices, such as a catalyst, and one or more exhaust gas sensors.

[0020] The engine 10 can further include one or more exhaust gas recirculation (EGR) channels or loops for recirculating at least a portion of the exhaust gas from the exhaust manifold to the intake manifold. These can include high-pressure EGR loops for providing high-pressure EGR (HP-EGR) and low-pressure EGR loops for providing low-pressure EGR (LP-EGR). In one example, HP-EGR can be provided when the turbocharging provided by the turbochargers 120, 130 is absent, while LP-EGR can be provided when turbocharging is present and / or when the exhaust gas temperature exceeds a threshold value. In other examples, both HP-EGR and LP-EGR can be provided simultaneously.

[0021] In the illustrated example, the engine 10 can include a low-pressure EGR loop 202 to recirculate at least some exhaust gas from the first branched parallel exhaust port 170 downstream of the turbine 124 to the first parallel inlet port 142 upstream of the compressor 122. In some embodiments, a second (not shown) low-pressure EGR loop can likewise be provided to recirculate at least some exhaust gas from the second branched parallel exhaust port 180 downstream of the turbine 134 to the second parallel inlet port 144 upstream of the compressor 132. The LP-EGR loop 202 can include both an LP-EGR valve 204 for controlling an EGR flow (i.e., a recirculated amount of exhaust gas) through the loops and an EGR cooler 206 for reducing the temperature of the exhaust gas flowing through the EGR loop before it is recirculated to the engine inlet.Under certain conditions, the EGR cooler 206 can also be used to heat the exhaust gas flowing through the LP-EGR loop 202 before the exhaust gas enters the compressor, in order to prevent water droplets from hitting the compressors.

[0022] The engine 10 can further include a first high-pressure EGR loop 208 to recirculate at least some exhaust gas from the first parallel exhaust port 17 upstream of the turbine 124 to the intake manifold 160 downstream of the intake throttle valve 158. Likewise, the engine can include a second high-pressure EGR loop (not shown) to recirculate at least some exhaust gas from the second parallel exhaust port 18 upstream of the turbine 134 to the second branched parallel intake port 148 downstream of the compressor 132. The EGR flow through the high-pressure EGR loops 208 can be controlled by a high-pressure EGR valve 210.

[0023] A PCV orifice 102 can be configured to direct the crankcase vent gases (the crankcase gases) along the second parallel intake channel 144 to the intake manifold of the engine. In some embodiments, the flow of PCV air through the PCV orifice 102 (e.g., the PCV flow) can be controlled by a dedicated PCV orifice valve. Similarly, a vent orifice 104 can be configured to direct the vent gases from a fuel system canister along channel 144 to the intake manifold of the engine. In some embodiments, the flow of vent air through the vent orifice 104 can be controlled by a dedicated vent orifice valve.

[0024] A humidity sensor 232 and a pressure sensor 234 can be located in only one of the parallel intake channels (shown here in the first parallel intake air channel 142, but not in the second parallel intake channel 144) downstream of the EGR throttle valve 230. Specifically, the humidity sensor and the pressure sensor can be located in the intake channel that does not receive the PCV or the exhaust air. The humidity sensor 232 can be configured to estimate the relative humidity of the intake air. In one embodiment, the humidity sensor 232 is a UEGO sensor configured to estimate the relative humidity of the intake air based on the sensor's output at one or more voltages.Because the drain air and the PCV air can interfere with the humidity sensor readings, the drain port and the PCV port are positioned in an inlet channel separate from the humidity sensor. The pressure sensor 234 can be configured to estimate the pressure of the inlet air. In some embodiments, a temperature sensor can also be included in the same parallel inlet channel downstream of the EGR throttle valve 230.

[0025] The inlet oxygen sensor 172 can be used to estimate the inlet oxygen concentration and, based on a change in the inlet oxygen concentration when the EGR valve 204 opens, to derive the amount of EGR flow through the engine. Specifically, a change in the sensor output when the EGR valve opens is compared to a reference point where the sensor operates without EGR (the zero point). Based on the change (e.g., decrease) in the amount of oxygen from the point of operation without EGR, the EGR flow currently supplied to the engine can be calculated. When a reference voltage (Vs) is applied to the sensor, a pump current (Ip) is output by the sensor. The change in oxygen concentration can be proportional to the change in the pump current (ΔIp) output by the sensor when EGR is present, relative to the sensor output when EGR is absent (the zero point).Based on a deviation of the estimated EGR flow from the expected (or target) EGR flow, further EGR control can be performed.

[0026] In one example, a zero-point estimate of the intake oxygen sensor can be performed during idle conditions, when intake pressure fluctuations are minimal and no PCV or vent air is drawn into the low-pressure intake system. Additionally, an idle adjustment can be performed periodically, such as on each initial idle after engine start, to compensate for the effects of sensor aging and part-to-part variability on the sensor output.

[0027] Alternatively, a zero-point estimate of the intake oxygen sensor can be performed during conditions without fuel supply to the engine, such as during a deceleration fuel shut-off (DFSO). Performing the adaptation during DFSO conditions can reduce not only noise factors, such as those obtained during idle adaptation, but also variations in the sensor reading due to EGR valve leakage.

[0028] In some cases, the PCV flow from drain port 102 and / or the drain flow from drain port 104 can cause an error in the estimation of the EGR flow by the inlet oxygen sensor 172 (also referred to herein as the inlet manifold oxygen sensor). As further discussed below, under boosted conditions, the PCV flow can result in a large change in oxygen concentration from zero. In other words, the PCV flow can cause a decrease in the inlet oxygen concentration measured by the inlet oxygen sensor 172. The controller may infer the second total change in inlet oxygen, which is attributable to the EGR, and thereby misestimate the EGR flow during PCV flow conditions. The procedures for correcting the PCV flow are described below with reference to the Fig. 4-5 discussed further.

[0029] In Fig. 1. The position of the intake and exhaust valves of each cylinder 14 can be controlled by hydraulically actuated tappets coupled to valve pushrods or by a direct-acting mechanical tappet system using cam projections. In this example, at least the intake valves of each cylinder 14 can be controlled by cam actuation using a cam actuation system. Specifically, the intake valve cam actuation system 25 can include one or more cams and can use variable cam timing or variable cam lift for the intake and / or exhaust valves. In alternative embodiments, the intake valves can be controlled by electric valve actuation. Similarly, the exhaust valves can be controlled by cam actuation systems or electric valve actuation.

[0030] The power system 100 can be controlled, at least partially, by a control system 15, which includes a controller 12, and by input from a vehicle operator via an input device (not shown). The control system 15 is shown to receive information from several sensors 16 (various examples of which are described here) and send control signals to several actuators 81. For example, the sensors 16 can include a humidity sensor 232, an intake air pressure sensor 234, a MAP sensor 182, an MCT sensor 183, a TIP sensor 174, and an intake air oxygen sensor 172. In some examples, the common intake duct 149 can further include a throttle valve intake temperature sensor for estimating a throttle valve air temperature (TCT).In other examples, one or more of the EGR channels may contain pressure, temperature, and air-fuel ratio sensors to determine the characteristics of the EGR flow. As another example, the actuators 81 may include the fuel injector 166, the high-pressure EGR valve 210, the low-pressure EGR valve 204, the throttle valves 158 and 230, and the boost pressure control valves 128 and 138. Other actuators, such as various auxiliary valves and throttle bodies, may be coupled to different locations in the power system 100. The controller 12 can receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on instructions or code programmed according to one or more routines within it. Exemplary control routines are given here with respect to the... Fig. 4-5 described.

[0031] In Fig. 2 is another exemplary embodiment 200 of the power machine according to Fig. 1 shown. The previous one in Fig. The components introduced in section 1 are similarly numbered and are not reintroduced here for the sake of brevity.

[0032] The embodiment 200 shows a fuel tank 218 configured to supply fuel to the fuel injectors of the engine. A fuel pump (not shown) immersed in the fuel tank 218 can be configured to pressurize the fuel supplied to the injectors of the engine 10, such as injector 166. The fuel can be pumped into the fuel tank from an external source through a fuel filler flap (not shown). The fuel tank 218 can contain several fuel mixtures, including a fuel with a range of alcohol concentrations, such as various gasoline-ethanol blends, including E10, E85, gasoline, etc., and combinations thereof. A fuel level sensor 219 located in the fuel tank 218 can provide a fuel level reading to the controller 12.As shown, the fuel level sensor 219 can include a float connected to a variable resistor. Alternatively, other types of fuel level sensors can be used. One or more other sensors, such as a fuel tank pressure sensor 220 for estimating fuel tank pressure, can be coupled to the fuel tank 218.

[0033] The vapors generated in the fuel tank 218 can be routed via a line 31 to a fuel vapor canister 22 before being discharged into the engine inlet 23. The engine inlet 23 may include the inlet channel 140 and the inlet manifold 160. The vapors discharged into the engine inlet 23 may include, for example, daily fuel tank vapors and refueling vapors. The canister may be filled with a suitable adsorbent, such as activated carbon, to temporarily capture the fuel vapors (including vaporized hydrocarbons) generated in the fuel tank. Then, during subsequent engine operation, when the discharge conditions are met, such as when the canister is saturated, the fuel vapors can be discharged from the canister into the engine inlet by opening a canister discharge valve 112 and a canister vent valve 114.

[0034] The canister 22 contains a vent opening 27 to allow gases from the canister 22 to be released to the atmosphere when fuel vapors are stored or collected from the fuel tank 218. The vent opening 27 can also allow fresh air to be drawn into the fuel vapor canister 22 when the stored fuel vapors are discharged to the engine inlet 23 via the drain line 28, the boost pressure path 92, or the vacuum path 90 (depending on the boost level), and the drain valve 112. The boost pressure path 92 and the vacuum path 90 can also be referred to here as the drain lines. While this example shows that the vent opening 27 is connected to fresh, unheated air, various modifications can also be used.The vent opening 27 can contain a canister vent valve 114 to regulate the flow of air and vapors between the canister 22 and the atmosphere. The vent valve can be open during fuel vapor storage operations (e.g., during refueling of the fuel tank and while the engine is not running) so that the air from which the fuel vapor has been separated after passing through the canister can be expelled to the atmosphere. Likewise, during emptying operations (e.g., during canister regeneration and while the engine is running), the vent valve can be open to allow a flow of fresh air to remove the fuel vapors stored in the canister.

[0035] The fuel vapors released from canister 22, for example during a draining operation, can be routed via drain line 28 either into the boost pressure path 92 or the vacuum path 90. The flow of vapors along drain line 28 can be controlled by the canister drain valve 112, which is coupled between the fuel vapor canister and the engine inlet. The quantity and rate of vapors released by the canister drain valve can be determined by the duty cycle of an associated solenoid (not shown) of the canister drain valve. The duty cycle of the solenoid of the canister drain valve can be controlled by the vehicle's powertrain control module (PCM), such as the controller 12, in response to the engine's operating conditions. B. including the speed-load conditions of the engine, an air-fuel ratio, a canister load, etc., will be determined.

[0036] An optional canister check valve (not shown) may be included in the drain line 28 to prevent gases from flowing in the opposite direction to the drain flow due to intake manifold pressure. The check valve may be necessary if the canister drain valve control is not precisely timed or if the canister drain valve itself can be forced open by high intake manifold pressure. An estimate of the manifold absolute pressure (MAP) can be obtained from the MAP sensor coupled to the intake manifold 160 and transmitted to the controller 12. Alternatively, the MAP can be derived from alternative engine operating conditions, such as the mass airflow (MAF) as measured by a MAF sensor coupled to the intake manifold.

[0037] Depending on the engine's operating conditions, the exhaust hydrocarbons can be routed to the intake manifold 160 via either a boost pressure path 92 or a vacuum path 90. Specifically, when the turbocharger 120 is operating to provide a boosted air charge to the intake manifold, the increased pressure in the intake manifold causes the one-way valve 94 in the vacuum path 90 to close, while the one-way valve 96 in the boost pressure path 92 opens. As a result, the exhaust air is routed via the boost pressure path 92 downstream of the air filter 156 and upstream of the charge air cooler 154 into the air intake duct 140. Here, the exhaust air is introduced upstream of the intake air sensor 172.In some embodiments, as shown, a Venturi nozzle 98 can be positioned in the charge air path, so that the exhaust air is directed to the inlet as it passes through the Venturi nozzle and the channel 99. This allows the flow of the exhaust air to be advantageously used for generating a vacuum.

[0038] During the conditions when the engine 10 is operating without forced induction, the increased vacuum in the intake manifold causes the one-way valve 94 in the vacuum path to open, while the one-way valve 96 in the boost path closes. As a result, the exhaust air is routed via the vacuum path 90 downstream of the throttle valve 158 into the intake manifold 160. Here, the exhaust air is introduced directly into the intake manifold 160 downstream of the intake oxygen sensor 172, and therefore does not affect the output of the oxygen sensor 172. In contrast, during the conditions when the engine 10 is operating with forced induction, the exhaust air is introduced upstream of the intake oxygen sensor 172, and therefore does affect the output of the oxygen sensor 172.

[0039] The PCV hydrocarbons can also be routed to the intake manifold 160 either via a PCV hose 252 on the boost side or a PCV hose 254 on the vacuum side, depending on the engine's operating conditions. Specifically, the crankcase gases flow from the engine cylinders 14 past the piston rings, entering the crankcase 255. During conditions when the turbocharger 120 is operating to provide a boosted air charge to the intake manifold, the increased pressure in the intake manifold causes the one-way valve 256 in the PCV hose 254 on the vacuum side to close. As a result, during boosted engine operation, the PCV gases flow in a first direction (arrow 262), being received downstream of the intake oxygen sensor in the engine intake.Specifically, the PCV air is routed via the PCV hose 252 on the boost side, downstream of the air filter 156 and upstream of the charge air cooler 154, into the air intake duct 140. After passing through an oil separator 260 on the boost side, the PCV flow can be directed to the intake duct. The oil separator on the boost side can be integrated into the cam cover or be an external component. Consequently, during boosted operation, the PCV gases are introduced upstream of the intake oxygen sensor 172, thus influencing the output of the oxygen sensor 172.

[0040] In comparison, during the conditions when the engine 10 is operating without a turbocharger, the increased vacuum in the intake manifold causes the one-way valve 256 in the PCV hose 254 to open on the vacuum side. As a result, during the naturally aspirated engine operation, the PCV gases flow in a second direction (arrow 264), which differs from the first direction, being received downstream of the intake oxygen sensor in the engine inlet. In the example shown, the second direction of PCV flow during naturally aspirated engine operation is opposite to the first direction of PCV flow during turbocharged engine operation (compare arrows 262 and 264). Specifically, during naturally aspirated operation, the PCV air is routed via the PCV hose 254 on the vacuum side, downstream of the throttle valve 158, directly into the intake manifold 160.Here, the PCV air is introduced downstream of the inlet oxygen sensor 172, and therefore does not affect the output of the oxygen sensor 172.

[0041] Consequently, the systems are configured according to the Fig. 1-2 a power engine system comprising a power engine containing an intake manifold, a crankcase coupled to the intake manifold via a PCV valve, a turbocharger with an intake compressor, an exhaust turbine and an intercooler, an intake throttle valve coupled to the intake manifold downstream of the intercooler, a canister configured to receive fuel vapors from a fuel tank, the canister coupled to the intake manifold via a drain valve, an EGR system comprising a channel for recirculating exhaust residues from a location downstream of the turbine via an EGR valve to a location upstream of the compressor, an oxygen sensor coupled to the intake manifold downstream of the intercooler and upstream of the intake throttle valve, and a controller with computer-readable instructions,For: Determining a correction factor for an intake oxygen sensor based on the PCV flow and charging conditions, and adjusting the position of the EGR valve based on an output from the intake oxygen sensor with respect to the correction factor.

[0042] As further described below, learning the correction factor involves determining a change in intake oxygen at the intake oxygen sensor between supercharged and naturally aspirated engine operation while both EGR and the drain valve are blocked (i.e., when both the EGR valve and the drain valve are closed). The controller may further include instructions to estimate an EGR flow rate based on a change in intake oxygen due to EGR, where the change in intake oxygen due to EGR is determined by subtracting a quantity of PCV hydrocarbons (e.g., the previously learned correction factor) from the intake oxygen sensor output.

[0043] As previously discussed, the intake air oxygen sensor 172 can be used to measure the amount of EGR in the intake air charge as a function of the change in oxygen content due to the addition of EGR, acting as a diluent. Consequently, as more EGR is introduced, the sensor may output a reading or pump current corresponding to a lower oxygen concentration. During the estimation, a nominal reference voltage (e.g., at 450 mV) or a Nernst voltage is applied to the sensor, and an output (e.g., a pump current output by the sensor when the lower reference voltage is applied) is observed. Based on the sensor output with respect to a sensor zero point (i.e., the sensor output under no-EGR conditions), a change in oxygen concentration is determined, and an intake dilution with EGR is inferred.

[0044] However, if the EGR estimation is performed under conditions when the drain and / or crankcase ventilation are open (e.g., PCV flow is open), the sensor output will be corrupted. In other words, the PCV and / or fuel vapor drain flow can cause an error in the intake oxygen sensor output. The drain air and / or crankcase ventilation hydrocarbons (e.g., the PCV flow) can be ingested as such during the engine's supercharged operating conditions along the boost pressure path 92 and the PCV hose 252 on the boost pressure side when the drain valve 112 is open and / or the PCV valve 256 is closed. The sensor output can be corrupted primarily due to the ingested hydrocarbons reacting with ambient oxygen at the intake sensor's sensing element.This reduces the (local) oxygen concentration indicated by the sensor. Because the sensor output and the change in oxygen concentration are used to infer EGR dilution of the intake air charge, the reduced oxygen concentration indicated by the intake oxygen sensor in the presence of blow-off air and / or PCV can be incorrectly interpreted as an additional diluent. This affects EGR estimation and subsequent EGR control. Specifically, the EGR may be overestimated.

[0045] Fig. Figure 3 illustrates this variation in the intake sensor reading. Specifically, graph 300 represents an oxygen concentration estimated by an intake manifold oxygen sensor along the y-axis and a PCV hydrocarbon content (PCV HC content) along the x-axis at a given EGR level. As the amount of PCV HCs drawn into the engine's intake manifold increases, such as when PCV is released during boosted conditions, the hydrocarbons react with the oxygen at the intake oxygen sensor's sensing element. The oxygen is consumed, releasing water and carbon dioxide. As a result, the estimated oxygen concentration is reduced, even if a certain amount of EGR flow remains constant. This reduction in the oxygen concentration estimated by the oxygen sensor can be interpreted as increased dilution (or replacement of oxygen by the EGR).Consequently, the controller may infer that a greater quantity of EGR flow is available than is actually present. If a controller is not corrected for the hydrocarbon effect, it may reduce the EGR flow in response to an incorrect reading of higher EGR dilution, thus degrading EGR control. For example, during drain and / or PCV flow conditions that lead to an overestimation of EGR, the controller may reduce the opening of the EGR valve in response to a higher EGR estimate (based on a lower intake oxygen reading from the intake oxygen sensor). However, the actual EGR may be lower than the estimated level. Consequently, the EGR flow may be incorrectly reduced instead of being maintained or increased. This, in turn, can lead to increased engine emissions and degraded engine performance.

[0046] In one example, adjusting the intake oxygen measurement based on the PCV flow can increase the accuracy of EGR flow estimates. Specifically, under certain engine operating conditions, an engine controller (such as the one in Fig. 1 controller 12) a contribution of the PCV flow to that at the inlet oxygen sensor (such as the inlet oxygen sensor 172, which is in the Fig. (as shown in Figures 1-2) determine the measured inlet oxygen concentration. If the effect of the PCV flow on the inlet oxygen under the charging conditions is known, the controller can use this to correct the measured inlet oxygen, which is used to estimate the EGR flow. The EGR estimate itself can be corrected based on the PCV flow.

[0047] The effect of PCV flow on intake oxygen measurements can be determined as a function of boost pressure. As discussed above, PCV flow can only be enabled (i.e., flowing) during boosted conditions (e.g., when the intake air is being turbocharged). During normal engine operation, when EGR is disabled (e.g., the EGR valve is closed and / or EGR is not flowing) and fuel vapor recovery is disabled (e.g., the fuel canister drain valve is closed), the effect of PCV on the intake oxygen sensor output can be determined. Specifically, during these conditions, intake oxygen can be measured by the intake oxygen sensor while the engine is not boosted. The controller can then engage boost and measure intake oxygen again at the intake oxygen sensor.A change in intake oxygen between uncharged and charged conditions can then represent the contribution of the PCV flow to reducing the intake oxygen from a reference point (e.g., zero). This change in intake oxygen due to the PCV flow can then be stored as a function of the boost pressure (e.g., in a controller memory) and used to adjust the EGR flow estimates during subsequent engine operation when the EGR and PCV flows are enabled. During engine operation with flowing EGR, the controller can, for example, obtain an intake oxygen measurement from the intake oxygen sensor. A difference between the reference point (e.g., zero) and the intake oxygen measurement then represents a second overall change in intake oxygen due to the system diluters (the EGR and the PCV).The previously determined change in intake oxygen due to PCV at a given boost pressure can then be subtracted from the second total change in intake oxygen to determine the actual change in intake oxygen due to EGR. This value can then be used to estimate the EGR flow.

[0048] In addition to correcting EGR estimates, the change in intake oxygen due to PCV flow can be used to accurately estimate the PCV flow. Specifically, a change in intake oxygen between turbocharged and non-turbocharged conditions, measured at the intake oxygen sensor, can be converted into equivalent hydrocarbons. Because during turbocharged engine operation with EGR blocked and idle, the absorbed hydrocarbons originate from the crankcase gases, these equivalent hydrocarbons can be used to estimate the PCV flow. The controller can use the PCV flow estimates to monitor and diagnose the PCV system and adjust the fuel supply to the engine. For example, as the estimated PCV flow increases, the controller can decrease the fuel supply to the engine.In this way, the controller can adjust the fuel injection based on estimates of the PCV flow. The procedures for determining a change in intake oxygen resulting from the PCV flow and estimating the EGR and PCV flow based on the change in intake oxygen from the PCV flow are described below with reference to the [reference to be added]. Fig. 4-5 discussed further.

[0049] In this way, a method for an engine comprises estimating the PCV flow based on a change in intake oxygen between naturally aspirated and supercharged engine operation when exhaust gas recirculation is blocked (e.g., EGR is not flowing and an EGR valve in a low-pressure EGR channel is closed) and drain is blocked (e.g., a drain valve coupled between a fuel system canister and an engine intake is closed), with the change in intake oxygen being measured by an intake manifold oxygen sensor. The method further comprises adjusting the engine's fuel supply based on the estimated PCV flow. In an example, the method may involve decreasing the engine's fuel supply as the estimated PCV flow increases.The method may further include learning the change in intake oxygen as a function of boost pressure, e.g., from a lookup table stored in the memory of the engine controller (e.g., in the KAM). Additionally, during subsequent engine operation with exhaust gas recirculation enabled and the fuel canister drain valve closed, the method may include estimating an exhaust gas recirculation flow rate based on an output from the intake manifold oxygen sensor, which is set based on the learned change in intake oxygen and a reference point of the intake oxygen sensor.Furthermore, the method may include adjusting an exhaust gas recirculation valve based on the estimated exhaust gas recirculation flow rate relative to a target exhaust gas recirculation flow rate, wherein the target exhaust gas recirculation flow rate is based on the speed-load conditions of the engine.

[0050] In Fig. Figure 4 shows a method 400 for determining a change in intake oxygen resulting from the PCV flow. The fuel supply to the engine can then be adjusted based on the PCV flow estimated from the change in intake oxygen. In one example, the intake oxygen can be measured by an intake oxygen sensor, such as the intake oxygen sensor 172, which is located in the Fig. The measurements shown in 1-2 can be taken. The instructions for executing procedure 400 can be stored in a memory of a controller of the power machine, such as the one shown in Fig. 1 of the controllers shown, 12, should be stored.

[0051] In 402, the procedure involves estimating and / or measuring the engine operating conditions. These may include, for example, engine speed and load, torque demand, boost pressure, EGR, required engine dilution, engine temperature, BP, MAP, etc. In 404, the procedure involves determining whether EGR is enabled. In one example, EGR may be enabled based on the engine speed-load conditions under which the benefits of EGR can be achieved. For example, EGR may be enabled when the engine speed is above a threshold speed (e.g., above idle speed) and when the engine load is above a threshold load (e.g., above a minimum load). The controller may determine that EGR is enabled if an EGR valve is open and EGR is flowing through an EGR channel (such as...).the EGR valve 152 or 210 and the EGR channel 150 or 208, which are in . Fig. (as shown in Figure 1). The EGR used here refers to low-pressure EGR that is recirculated from an exhaust manifold downstream of a turbine to an intake manifold upstream of a compressor. If the EGR is enabled (e.g., the EGR is flowing through the intake port), the procedure proceeds to Figure 406 to measure the intake oxygen and adjust the intake oxygen measurement based on the PCV flow to estimate the EGR. Specifically, the intake oxygen measurement can be adjusted to account for the intake oxygen contribution due to the PCV flow as determined during the preceding engine operation (as in Figures 412-418). Fig. (as shown in Figure 4) to take this into account and remove this inlet oxygen contribution. In this way, the controller can obtain a more accurate estimate of the EGR flow. A method for adjusting the inlet oxygen and estimating the EGR based on the PCV flow is described in Figure 4. Fig. 5 is shown and will be explained further below.

[0052] If the EGR is blocked at 404, for example, if the EGR is not flowing and the EGR valve is closed, the procedure continues to 408 to determine whether the fuel canister drain is enabled. As introduced above, a fuel vapor canister (such as the one in Fig. The two fuel vapor canisters (22) shown are emptied when the canister charge exceeds a threshold, the engine is running, and a vent valve is open. If vent air is received as such in the intake air charge, the vent hydrocarbons (vent HCs) can be drawn into the EGR along with the exhaust residue. These hydrocarbons can react with oxygen at the sensing element of the intake oxygen sensor, producing carbon dioxide and water. The resulting reduction in oxygen concentration leads to an inaccurate reading of the engine dilution. Furthermore, in the presence of vent air, a controller may be unable to distinguish the effect of the vent hydrocarbons on the oxygen sensor from that of the PCV hydrocarbons.Consequently, if the drain is enabled at 408, the procedure proceeds to 410 to wait until the fuel canister drain valve closes, thereby indicating that the drain is blocked. Alternatively, the procedure can close the drain valve at 410 to allow the PCV experience to occur. In other words, the intake oxygen sensor-based PCV flow estimation is only executed if there is no other reducing agent contribution from the EGR or drain air.

[0053] With the fuel can drain valve closed and draining blocked, the procedure proceeds to 412 to determine if the engine is supercharged. In one example, determining if the engine is supercharged might involve determining if the MAP is greater than the compressor inlet pressure (CIP). If the engine is not supercharged (which is also referred to as an unsupercharged condition, for example, if the MAP is less than the CIP), the procedure proceeds to 414, where the inlet oxygen sensor measures the inlet oxygen while the engine is not supercharged. As discussed above, an output from the oxygen sensor might reflect an inlet oxygen concentration in the intake air. The procedure then proceeds to 416 to enable or engage supercharging (e.g.,to operate the engine under supercharged conditions) and to measure the intake oxygen concentration of the air with the intake oxygen sensor. Alternatively, the procedure at 416 may involve waiting until the engine enters supercharged operation via a driver request (e.g., entering supercharged operation in response to the engine's operating conditions) and then measuring the intake oxygen with the intake oxygen sensor during supercharged operation. At 418, the controller determines the change (e.g., the difference) in the intake oxygen concentration (or sensor outputs) between the supercharged and unsupercharged conditions. The difference in the intake oxygen sensor output between the supercharged and unsupercharged conditions indicates an (initial) change in intake oxygen due to PCV flow.In some examples, the (initial) change in inlet oxygen can also be corrected based on humidity (e.g., based on a humidity reading from a humidity sensor). This may involve adjusting the sensor outputs and / or the difference between sensor outputs based on an estimate of the ambient humidity, either to eliminate the effect of all ambient humidity (to standardize to dry ambient conditions) or to adjust to a known amount of ambient humidity (to standardize to a predetermined and calibrated amount of ambient humidity).

[0054] At 420, the controller can store the change in intake oxygen due to the PCV as a function of the boost pressure. For example, the controller can maintain a lookup table of the change in intake oxygen from the PCV flow as a function of the boost pressure, stored in a memory (e.g., the KAM) of the controller. The lookup table can be updated with the learned change in intake oxygen, determined at 418 at the corresponding boost pressure. The learned value can then be used as a correction factor during boosted conditions when the EGR is flowing, as described below with reference to Fig. 5 is discussed further. In some examples, the table can be continuously updated during engine operation if both EGR and the drain are locked (e.g., switched off). In another example, once the table has been populated with changes to the intake oxygen data within a range of boost pressures, the controller can update the table only after a period of engine operation. For example, the controller can update the PCV intake oxygen data after a predetermined number of engine operating hours or a defined number of drive cycles. In yet another example, the controller can update the PCV intake oxygen data after a certain number of engine starts or repeated cold start conditions. For example, the controller can update the PCV intake oxygen data once every ten engine starts in cold weather (e.g.,(at a temperature below a threshold). Furthermore, if significant PCV flow is detected, indicating increased fuel dilution of the oil, the PCV intake oxygen data can be updated more frequently until the fuel evaporates from the oil (as indicated, for example, by a decrease in the estimated PCV flow rate). In this way, the update rate of the PCV intake oxygen data can be set based on the specific PCV flow, engine temperatures, ambient temperatures, and / or additional engine operating conditions.

[0055] In document 422, the procedure involves converting the change in inlet oxygen due to PCV flow into equivalent hydrocarbons to estimate the PCV flow. Specifically, based on the change in oxygen concentration due to PCV, a quantity or concentration of hydrocarbons can be determined. This can then be used as an estimate of the PCV flow to the engine inlet. For example, the PCV flow estimate can be used to monitor the PCV system and determine if the system is deteriorating. The changes in the inlet oxygen sensor reading between supercharged and unsupercharged conditions, for instance, can indicate that the PCV system is flowing as expected, is not blocked, and does not have a broken hose.If the change in the intake oxygen reading between the supercharged and unsupercharged conditions exceeds a threshold, it can indicate a significant amount of fuel hydrocarbons originating from the PCV. This can falsely trigger fuel system monitoring. Therefore, this information can be used to disable the fuel system monitoring device. In another example, as shown in Figure 424, the controller can adjust the fuel supply to the engine based on the specific PCV flow. For example, the controller can adjust the mass and / or volume of fuel supplied to the engine cylinders. In one example, the fuel supply to the engine (e.g., the mass and / or volume of fuel supplied through the fuel injectors) can be reduced as the PCV flow increases.In one example, the amount of fuel coming from the PCV flow is estimated by determining the magnitude of the change in intake oxygen due to the PCV and converting this magnitude into the quantity of fuel vapor. The change in intake oxygen is converted into a mass of fuel, assuming that the fuel in the PCV is the same type as the fuel in the injectors (for example, it is assumed that the nominal stoichiometric air / fuel ratio of the fuel in the PCV is the same as that of the fuel in the injectors). In other examples, a time control of the fuel injection can also be set.

[0056] If, back at 412, the engine is supercharged instead of unsupercharged, the procedure continues to 426. At 426, the procedure involves determining whether the engine is capable of switching to unsupercharged operation (e.g., being able to disable supercharging). If the engine is unable to disable supercharging (e.g., due to the torque demand), the procedure continues to 428 to wait until supercharging can be disabled in order to determine the change in intake oxygen due to PCV. In one example, the engine may be unable to operate unsupercharged if the torque demand exceeds a threshold, thereby requiring the MAP to be greater than atmospheric pressure (BP).Conversely, if the engine is able to switch off the boost at 426, the procedure continues to 430 to measure the intake oxygen via the intake oxygen sensor while the engine is still boosted. Then, at 432, the boost is switched off, and the intake oxygen is measured again via the intake oxygen sensor while the engine is not boosted. Alternatively, at 432, the procedure may involve waiting until the engine switches to unboosted operation in response to a torque demand or other engine operating conditions. Then, after the switch to unboosted operation, the controller can measure the intake oxygen via the intake oxygen sensor. The procedure then continues to 418 to determine the change in intake oxygen between the boosted and unboosted conditions, as described above.In alternative embodiments, the procedure of 426 can proceed to turn off the supercharging and then measure the inlet oxygen. The procedure can then proceed to 416 to turn the supercharging back on and measure the inlet oxygen. In other words, if the engine is not supercharged, the routine first includes obtaining an output during unsupercharged operation, then operating the engine with supercharging even if supercharging is not required, and obtaining an output during supercharged operation. In comparison, if the engine is supercharged, the routine first includes obtaining an output during supercharged operation, then operating the engine without supercharging if the torque requirement is below a threshold, and obtaining an output during unsupercharged operation.

[0057] The procedure can then proceed to steps 418-424, as described above, to estimate the moisture-corrected PCV flow and adjust the engine fuel supply based on the estimated PCV flow. As discussed above, in one example, estimating the PCV flow (e.g., learning the PCV correction factor for EGR estimation) via procedure 400 can be done with a first frequency, the first frequency being based on a threshold number of engine starts. The threshold number of engine starts might, for example, include engine starts in a range of approximately 10 to 100. Furthermore, the frequency of estimating the PCV flow and learning the PCV correction factor in response to an increase in the estimated PCV flow above a threshold can increase from the first frequency to a higher, second frequency.Estimating the PCV flow at the second frequency can then be maintained until the estimated PCV flow falls back below the threshold, with the second frequency increasing as the magnitude of the estimated PCV flow increases. In this way, the frequency of estimating the PCV flow can be based on changes in the estimated PCV and its magnitude.

[0058] In Fig. Figure 5 shows a method 500 for adjusting EGR operation based on a change in intake oxygen due to PCV flow. As described above, when the EGR is flowing, an EGR estimate based on the measured intake oxygen can be adjusted (e.g., corrected) based on the PCV's contribution to a second total change in intake oxygen from a reference point. As a result, a more accurate estimate of the EGR flow can be determined, leading to improved control of the EGR system and reduced emissions. As described above, in one example, the intake oxygen can be measured by an intake oxygen sensor, such as the one described in the Fig. The inlet oxygen sensor 172 shown in Figures 1-2 can be measured. The instructions for performing procedure 500 can be stored in a memory of a controller of the power machine, such as the one shown in Figures 1-2. Fig. 12 controllers shown, should be stored.

[0059] The procedure begins at 502 by estimating and / or measuring the engine operating conditions. In an example, the engine operating conditions may include the engine speed and load, the torque requirement, the MAF, the MAP, the EGR, the position of an EGR valve, a PCV valve, and a fuel can drain valve, the boost pressure, the EGR, the required engine dilution, the engine temperature, the BP, etc. At 504, the procedure includes determining whether the EGR is enabled. As discussed above, the EGR may be enabled if the EGR valve is at least partially open, with the EGR flowing through the low-pressure EGR channel and into the engine intake. If the EGR is not enabled (e.g., the EGR valve is partially closed), the procedure involves determining whether the EGR is enabled.(where the PCV is in a closed position and the EGR is not flowing), the procedure continues to 506 to determine the effect of the PCV flow on the inlet oxygen if the drain is not released, as in . Fig. 4 is described. If, for example, the EGR is not flowing and the fuel canister drain valve is closed, a change in intake oxygen between the turbocharged and non-turbocharged conditions can be compared to determine the PCV effect on the intake oxygen measurements.

[0060] Alternatively, if EGR is enabled at 504, the procedure proceeds to 508 to determine if PCV is enabled. PCV can be enabled if the engine is turbocharged and a PCV valve is open. As discussed above, if PCV is enabled, PCV hydrocarbons (PCV-HCs) can be drawn into the intake air charge along with exhaust residue in the EGR system. These hydrocarbons can react with oxygen at the intake oxygen sensor's sensing element, producing carbon dioxide and water. The resulting reduction in oxygen concentration leads to an inaccurate representation of the engine dilution and an inaccurate estimate of the EGR flow.

[0061] If the PCV is cleared, the procedure proceeds to 510 to determine if the fuel can drain is cleared. As discussed above, a fuel can drain valve (such as the one in Fig. The canister drain valve 112 (shown in Figure 2) must be open if fuel canister draining is enabled. If draining is blocked at 510, the procedure proceeds to 514. At 514, the procedure involves measuring the intake oxygen at the intake oxygen sensor and determining a set change in intake oxygen relative to a reference point and a predetermined change in intake oxygen due to PCV flow. First, the intake oxygen sensor may measure the intake oxygen. The procedure at 514 may then involve subtracting the intake oxygen measurement (e.g., the output from the intake oxygen sensor) from a reference point. As discussed above, the reference point may be a predetermined point if the sensor operates without EGR (the zero point). Consequently, the resulting value can represent a second overall change in the inlet oxygen (at the inlet oxygen sensor) due to the diluents in the airflow (e.g.the air charge). In one example, the diluents could be the EGR and the PCV (e.g., the HCs from the PCV flow). The method can then involve subtracting the change in intake oxygen due to the PCV flow at the corresponding boost level from the second total change in intake oxygen due to the diluents (e.g., the EGR and the PCV) in the airflow. The change in intake oxygen due to the PCV flow can be stored in the controller at a corresponding boost pressure. The intake oxygen due to the PCV flow can be determined beforehand during engine operation when both the EGR and the exhaust gas recirculation (EGR) were disabled, as in [reference]. Fig. 4 is discussed. In some examples, the stored change in intake oxygen due to the PCV flow can be described as a correction factor because the second total change in intake oxygen measured at the intake oxygen sensor is corrected by this value to determine the EGR flow.

[0062] The result of subtracting the change in intake oxygen due to PCV flow from the total change in intake oxygen due to diluents can be the change in intake oxygen due to EGR. More specifically, the result can be the change in intake oxygen due to EGR alone, and not due to PCV. In some examples, the change in intake oxygen due to EGR can also be adjusted based on humidity (e.g., ambient humidity measured by a humidity sensor).

[0063] Alternatively, at 510, if fuel canister draining is enabled, the procedure continues to 512 to measure the intake oxygen at the intake oxygen sensor and determine a set change in intake oxygen based on a reference point, a predetermined change in intake oxygen due to PCV flow, and a change in intake oxygen due to fuel vapor draining (e.g., a draining correction factor). In this way, the procedure at 512 can follow the procedure at 514, while additionally correcting the intake oxygen measurement based on a draining correction factor. In alternative embodiments, if draining is enabled, the oxygen sensor can be operated at a higher reference voltage during EGR estimation to counteract the effect of the draining air.The resulting value at 514 can be the change in intake oxygen due to EGR alone, and not due to PCV or the drain. In this way, the intake oxygen measurement can be corrected for PCV flow both when the drain is enabled and when it is blocked. However, when the drain is enabled, a predefined correction factor for the drain (e.g., a change in intake oxygen due to fuel canister emptying) can also be applied to the intake oxygen sensor reading to determine the change in intake oxygen due to EGR.

[0064] In procedure 516, the process involves determining (e.g., estimating) the EGR based on the set change in the intake oxygen measurement. As described above, the set change in the intake oxygen measurement can be the change in intake oxygen due to EGR. Furthermore, determining the EGR can involve estimating the EGR flow rate based on the change in intake oxygen due to EGR. Then, in procedure 518, the process can involve adjusting an EGR valve based on the determined EGR. For example, if the estimated EGR flow rate is greater than a target EGR flow rate (based on the engine's operating conditions), the controller can reduce the opening of the EGR valve to decrease the EGR flow to the target flow rate.In another example, if the estimated EGR flow is lower than the target EGR flow rate, the controller can increase the EGR valve opening to raise the flow rate to the target value. In some examples, additional engine operating parameters can be set based on the specific EGR flow rate. For example, the spark timing, throttle angle, and / or fuel injection can be adjusted based on the specific EGR flow rate.

[0065] If the PCV is not enabled back at 508, the procedure proceeds to 520 to measure the intake oxygen concentration with the intake oxygen sensor and determine the change in intake oxygen from the reference point. As described above, the procedure at 520 may involve subtracting the intake oxygen measurement from the reference point. The resulting value may be a second total change in intake oxygen (at the intake oxygen sensor) due to diluents in the airflow (e.g., air charge). Because the PCV is not enabled in this case, the principal or only diluent in the airflow may be the EGR. Consequently, the EGR flow can be estimated from the second total change in intake oxygen at 516, as discussed above.

[0066] In one embodiment, a method for a power engine comprises estimating the PCV flow based on both a first output from the intake manifold oxygen sensor with boost enabled and a second output from the sensor with boost disabled, while exhaust gas recirculation (EGR) and drain are blocked, and adjusting an EGR valve based on a third output from the sensor and the estimated PCV flow during subsequent operation with EGR flowing. In another embodiment, a method for a power engine comprises adjusting an EGR valve based on an output from an intake oxygen sensor and the PCV flow during operation with EGR flowing, wherein the PCV flow during the preceding operation with EGR blocked and drain is identified from the outputs of the intake oxygen sensor with and without boost.

[0067] Estimating the PCV flow involves determining the difference between the first and second outputs to determine the first intake oxygen change resulting from the PCV flow. The procedure further involves adjusting the intake oxygen change resulting from the PCV flow based on humidity. Additionally, the procedure involves adjusting the third output with respect to a reference point during operation with flowing EGR to determine a second overall intake oxygen change due to diluents in the intake air charge. In an example, adjusting the EGR valve based on the third output involves adjusting the EGR valve based on the second overall intake oxygen change due to diluents in the intake air charge when the PCV is not enabled.In another example, adjusting the EGR valve based on the third output involves adjusting the EGR valve based on a third change in intake oxygen resulting from the EGR when the PCV is released, wherein the third change in intake oxygen from the EGR is determined by a difference between the second total change in intake oxygen due to the diluents in the intake air charge and the first change in intake oxygen resulting from the PCV flow.

[0068] The method further includes, if the engine is not supercharged, first obtaining the second output during unsupercharged operation and then obtaining the first output during subsequent supercharged operation; and if the engine is supercharged, first obtaining the first output during supercharged operation and then obtaining the second output during subsequent unsupercharged operation. In this way, the second and first outputs are obtained during unsupercharged and supercharged operation, respectively, with the switching between unsupercharged and supercharged operation occurring in response to the engine's operating conditions, such as the torque demand.

[0069] In an alternative embodiment, if the engine is not supercharged, the method may first include obtaining the second output during unsupercharged operation, then operating the engine with supercharged power even if no supercharger is required, and obtaining the first output during supercharged operation. Conversely, if the engine is supercharged, the method may first include obtaining the first output during supercharged operation, then operating the engine without supercharged power if the torque requirement is below a threshold, and obtaining the second output during unsupercharged operation.

[0070] The estimated PCV flow is stored as a correction factor, derived as a function of the boost pressure, in a memory of the engine controller. The controller can continuously update the correction factor when both the EGR and the drain are locked. Furthermore, if the drain is enabled, the procedure includes waiting until a fuel canister drain valve closes and the drain is locked to estimate the PCV flow. The procedure also includes adjusting the fuel injection to the engine based on the estimated PCV flow, decreasing the amount of injected fuel as the estimated PCV flow increases.

[0071] Fig. Figure 6 shows a graphical example of the settings on an EGR valve and the fuel supply to the engine based on the changes in intake oxygen resulting from the PCV flow. Specifically, graphic 600 shows the changes in the actual EGR flow, graphic 602 shows the changes in an uncorrected EGR flow, and graphic 603 shows the changes in a target EGR flow (e.g.,a target EGR flow) in graph 604, changes in the position of a fuel canister drain valve in graph 606, changes in PCV flow in graph 608, changes in boost pressure in graph 610, changes in intake oxygen in graph 612, changes in engine fuel supply in graph 614, and changes in the position of an EGR valve in graph 616. The changes in intake oxygen shown in graph 612 can be measured by an intake oxygen sensor positioned in an engine's intake system. As discussed above, in one example the intake oxygen sensor is located in an intake manifold downstream of the point where the EGR flow and the PCV flow enter the intake system (e.g.an intake manifold oxygen sensor), and positioned upstream of an intake throttle valve.

[0072] Before time t1, the EGR valve is closed (graphic 616), and no EGR flows into the engine's intake manifold (the EGR is switched off) (graphic 602). Furthermore, the drain valve is closed (graphic 606), and the engine is not supercharged (e.g., the supercharging is switched off) (graphic 610). In the present example, a PCV valve in the PCV system may be closed, and PCV cannot flow upstream of the intake sensor (graphic 608). In some examples, the PCV valve may be open, but during the unsupercharged conditions, PCV flow can be received directly in the engine's intake manifold downstream of the intake oxygen sensor, and therefore the PCV flow cannot influence the intake oxygen sensor output.Because the PCV and EGR are not flowing, there can be less diluent in the intake air charge (e.g., the intake air flow to the intake manifold). Consequently, the intake oxygen can be at a higher initial level. Because the EGR is not flowing and the drain valve is closed, the controller (e.g., the engine controller) can determine a correction factor for the intake oxygen sensor. At time t1, the controller can initiate supercharged operation of the engine and increase the boost pressure (see graph 610). Supercharged operation can occur in response to a torque demand. As the boost pressure increases, the PCV flow also increases (see graph 608).Once the power unit is charged at time t2, the inlet oxygen can be measured during charged operation if the PCV is received upstream of the inlet oxygen sensor and if the sensor output is influenced by the PCV flow. In one example, the power unit may require a period of time to reach steady-state charged conditions where the PCV flow operates at a substantially steady rate. As shown in Figure 600, this period may lie between time t1 and time t2. In some examples, if the controller learns the PCV flow correction factor, it may wait the period after charging is initiated to obtain the charged inlet oxygen measurement.

[0073] Due to the flowing PCV, the intake oxygen decreases to a second, lower level between time t1 and time t2. The decrease or change in intake oxygen between time t1 and time t2 is shown at 618. The change in intake oxygen between time t1 and time t2 (shown at 618) is the change in intake oxygen resulting from the PCV flow at the boost pressure level. The controller can store this change in intake oxygen due to the PCV flow and the corresponding boost pressure level in the controller's memory. In one example, the change in intake oxygen due to the PCV flow can be referred to as a correction factor, which can be stored in the controller's memory in a lookup table for subsequent correction of intake oxygen measurements for estimating the EGR flow.

[0074] In addition to determining the correction factor, the change in inlet oxygen due to PCV flow can be used to estimate the PCV flow. Estimating the PCV flow can involve estimating a PCV flow rate or a PCV flow quantity. For example, the change in inlet oxygen shown in Figure 618 can be converted into equivalent hydrocarbons. The equivalent hydrocarbons can then be used to determine the PCV flow. At time t2, the controller can reduce the fuel supply to the engine based on the estimated PCV flow (e.g., decrease the amount of fuel supplied to the cylinders) (see Figure 614).

[0075] After a period of engine operation, EGR may flow at time t3 (see graph 602). The EGR valve may be open (see graph 616) to allow exhaust gases to flow from the exhaust port to the engine's intake port. Additionally, at time t3, the drain valve may be closed (see graph 606), the engine may be turbocharged (see graph 610), and PCV may flow into the intake port (see graph 608). In response to the flowing EGR while the drain valve is closed, the engine controller can correct the intake oxygen sensor output (e.g., the intake oxygen measurement shown in graph 612) based on the previously stored PCV flow correction factor.Specifically, the inlet oxygen output by the inlet oxygen sensor is at a third, lower level (which is, for example, lower than the first level shown at time t1 and the second level shown at time t2), as shown at time t3.

[0076] In some examples, the first level may be a reference level of the intake oxygen sensor. In other examples, a further, higher intake oxygen level may be the reference level of the intake oxygen sensor. Consequently, the second total change of intake oxygen with respect to the reference level may be shown at 620. The second total change of intake oxygen (shown at 620) may be due to either the PCV or the EGR. The contribution of the PCV flow to the second total change of intake oxygen (e.g., the change in intake oxygen resulting from the PCV flow) is the amount shown at 618. The remaining amount may be the contribution of the EGR flow to the second total change of intake oxygen (e.g., the change in intake oxygen resulting from the EGR flow), as shown at 622.In other words, the change in intake oxygen due to PCV (shown at 618) plus the change in intake oxygen due to EGR (shown at 622) is approximately equal to the second total change in intake oxygen (shown at 620).

[0077] Consequently, the change in intake oxygen resulting from the EGR flow can be a set change in intake oxygen based on the PCV correction factor (e.g., the change in intake oxygen resulting from the PCV flow). If, for example, no correction factor for the PCV flow has been used, the controller may determine that the second total change in intake oxygen (shown at 620) originates from the EGR. As a result, the EGR flow rate can be estimated based on this value, as shown by the uncorrected estimate of the EGR flow (Graph 603). Consequently, the uncorrected EGR flow rate (Graph 603) may be overestimated by the actual EGR flow rate (Graph 602). In response, the controller may reduce the EGR flow rate by a larger amount than is actually required.

[0078] As shown at time t4, the controller can reduce the opening of the EGR valve (Figure 616) because the estimated EGR flow (based on the change in intake oxygen set by the PCV flow) is slightly higher than the setpoint EGR flow rate (e.g., the target EGR flow rate) (Figure 604). In one example, the target EGR flow rate might be based on the engine speed and load conditions. This reduction in the opening of the EGR valve might be smaller than the reduction in the opening of the EGR valve if the intake oxygen sensor output were not set with respect to the PCV correction factor.

[0079] How between time t1 and time t3 in Fig. As shown in Figure 6, a method for a power machine can include learning a correction factor for an inlet oxygen sensor based on the PCV flow and the charging conditions. Furthermore, as shown at time t4, the method can also include adjusting the position of the EGR valve based on an output from the inlet oxygen sensor with respect to the correction factor.

[0080] As at time t2 in Fig.As shown in Figure 6, the procedure, during supercharged conditions when EGR and the exhaust port are closed, involves the flow of crankcase gases from the crankcase to the intake manifold and the acquisition of a first output from the intake manifold oxygen sensor. The first output from the intake manifold oxygen sensor can be the second intake oxygen level shown at time t2. As shown at time t1, during unsupercharged conditions when EGR and the exhaust port are closed, the procedure involves the non-flow of crankcase gases from the crankcase to the intake manifold and the acquisition of a second, different output from the intake manifold oxygen sensor. The second output can be the first intake oxygen level shown at time t1.The controller can then learn the amount of PCV flow to the intake manifold based on the difference between the first and second outputs. During the subsequent charged conditions, when EGR is enabled and the drain is locked, as shown at time t3, the procedure involves learning a third output from the intake manifold oxygen sensor. This third output can be the third level of intake oxygen shown at time t3. The controller can then correct the third output based on the learned amount of PCV flow, estimate the EGR flow based on the corrected third output, and adjust the opening of the EGR valve based on the estimated EGR flow (with respect to a target EGR flow, as shown at time t4).

[0081] In this way, the intake oxygen sensor output can be corrected for PCV flow. As described above, the intake oxygen sensor can be an intake manifold oxygen sensor located in the intake manifold of the engine. If the contribution to the change in intake oxygen due to PCV flow is removed from the intake oxygen sensor output, the remaining value can be essentially equivalent to the change in intake oxygen due to EGR flow. This value can then be used to more accurately estimate the EGR flow. In this way, by adjusting the EGR operation based on the estimated EGR flow, a technical effect is achieved, with the estimated EGR flow being based on a change in intake oxygen resulting from the PCV flow.As a result, the control of the EGR system can be improved, and engine emissions can be maintained at target levels. Furthermore, the engine's fuel injection can be adjusted based on the PCV flow estimated by the intake oxygen sensor, which improves fuel economy and engine performance.

[0082] It should be noted that the exemplary control and estimation routines contained herein can be used with various system configurations of the power unit and / or the vehicle. The control procedures and routines disclosed herein can be stored as executable instructions in non-volatile memory. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, the illustrated various actions, operations, and / or functions can be executed in the illustrated order, executed in parallel, or, in some cases, omitted.Likewise, the processing sequence is not necessarily required to achieve the features and advantages of the exemplary embodiments described here, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, operations, and / or functions can graphically represent code to be programmed into the non-volatile memory of the computer-readable storage medium in the power machine control system.

[0083] It is clear that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be considered limiting, as numerous variations are possible. The above technology can be applied, for example, to the V-6, I-3, I-4, I-6, V-12, Boxer-4, and other types of power machines. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0084] The following claims specifically describe certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or its equivalent. Such claims should be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Further combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application.Such claims, whether their scope is broader than, narrower than, equal to, or different from the scope of the original claims, are also considered to be included in the subject matter of the present disclosure.

Claims

[1] Method for a power machine (10) comprising the following: Setting an EGR valve (204) based on an output of an inlet oxygen sensor (172) and the PCV flow during operation with flowing EGR, wherein the PCV flow during the preceding operation with EGR blocked and draining is identified based on the outputs of the inlet oxygen sensor (172) with and without boost. [2] Method according to claim 1, wherein the blocked drain includes a drain valve (112) coupled between a fuel system canister (218) and an inlet manifold (160) of the engine (10) being closed, and wherein the blocked EGR includes an EGR valve (204) in a low-pressure EGR channel (202) being closed. [3] Method according to claim 1, wherein the PCV flow identified based on the outputs of the inlet oxygen sensor (172) with and without supercharging comprises identifying the PCV flow based on a difference between a first output of the oxygen sensor (172) estimated with EGR and drain blocked and with supercharging, and a second output of the inlet oxygen sensor (172) estimated with EGR and drain blocked and without supercharging, wherein the difference indicates a first change in the inlet oxygen resulting from the PCV flow. [4] The method of claim 3, further comprising adjusting the first change in inlet oxygen resulting from the PCV flow based on the ambient humidity. [5] Method according to claim 4, wherein adjusting the EGR valve (204) based on an output of the inlet oxygen sensor (172) includes adjusting the EGR valve (204) based on a third output of the inlet oxygen sensor (172) with respect to a reference point during operation with flowing EGR in order to determine a second overall change in the inlet oxygen due to the diluents in the inlet air charge. [6] Method according to claim 5, wherein adjusting the EGR valve (204) based on the output of the inlet oxygen sensor (172) and the PCV flow includes adjusting the EGR valve (204) based on the second total change in inlet oxygen due to the diluents in the inlet air charge when the PCV is not enabled, and adjusting the EGR valve (204) based on a third change in inlet oxygen resulting from the EGR when the PCV is enabled, wherein the third change is determined based on a difference between the second total change in inlet oxygen due to the diluents in the inlet air charge and the first change in inlet oxygen resulting from the PCV flow. [7] The method of claim 3, further comprising, when the power engine (10) is not charged, first obtaining the second output during the uncharged operation and then obtaining the first output during the subsequent charged operation, and when the power engine (10) is charged, first obtaining the first output during the charged operation and then obtaining the second output during the subsequent uncharged operation. [8] Method according to claim 1, further comprising learning the identified PCV flow as a correction factor, wherein the correction factor is stored as a function of the boost pressure in a lookup table of the memory of the engine controller (12), and continuously updating the correction factor when both the EGR and the drain are blocked. [9] The method of claim 1, further comprising waiting until a fuel canister drain valve (112) is closed and the draining is blocked if the draining is enabled, in order to estimate the PCV flow. [10] Method according to claim 1, further comprising adjusting the fuel injection into the engine (10) based on the estimated PCV flow, wherein the amount of fuel injected decreases as the estimated PCV flow increases. [11] Method according to claim 1, wherein, when the power machine (10) is operated with charging and the PCV is enabled, the PCV flow is received in a power machine inlet (23) upstream of the inlet oxygen sensor (172), and wherein, when the power machine (10) is operated without charging and the PCV is enabled, the PCV flow is received in the power machine inlet (23) downstream of the inlet oxygen sensor (172). [12] Method comprising the following: Flow of PCV gases in a first direction and reception of PCV gases in a power engine inlet (23) upstream of an inlet oxygen sensor (172) during the charged power engine operation; Flow of the PCV gases in a second, different direction and reception of the PCV gases in the engine inlet (23) downstream of the inlet oxygen sensor (172) during uncharged operation; and Estimating the PCV flow based on a change in the intake oxygen estimated by the intake oxygen sensor (172) between the uncharged and the charged engine operation while EGR and drain are blocked. [13] The method of claim 12, further comprising estimating the PCV flow at a first frequency, wherein the first frequency is based on a threshold number of power machine starts, and further comprising increasing the first frequency to a higher second frequency in response to an increase in the estimated PCV flow above a threshold and maintaining the estimation of the PCV flow at the second frequency until the estimated PCV flow falls below the threshold, wherein the second frequency increases with an increasing magnitude of the estimated PCV flow. [14] Method according to claim 12, further comprising adjusting the fuel supply to the engine (10) based on the estimated PCV flow, wherein the fuel supply to the engine (10) decreases when the estimated PCV flow increases. [15] The method of claim 14, further comprising investigating the change in inlet oxygen as a function of the boost pressure during supercharged engine operation. [16] Method according to claim 15, further comprising estimating an EGR flow rate based on an output of the inlet oxygen sensor (172) during subsequent engine operation with EGR enabled and drain blocked, wherein a correction factor is based on the known change in inlet oxygen and a reference point of the inlet oxygen sensor (172). [17] Method according to claim 16, further comprising adjusting an EGR valve (204) on the estimated exhaust gas recirculation flow rate with respect to a target exhaust gas recirculation flow rate, wherein the target exhaust gas recirculation flow rate is based on the speed-load conditions of the engine (10). [18] Power machine system (100) comprising the following: a power engine (10) which includes an inlet manifold (160); a crankcase (255) which is coupled to the intake manifold (160) via a PCV valve (256); a turbocharger (120) with an inlet compressor (122), an exhaust turbine (124) and an intercooler (154); an intake throttle valve (158) which is coupled to the intake manifold (160) downstream of the charge air cooler (154); a canister (22) configured to receive fuel vapors from a fuel tank (218), the canister (22) being coupled to the inlet manifold (160) via a drain valve (112); an EGR system comprising a channel (202) for recirculating exhaust gas residues from a location downstream of the turbine (124) via an EGR valve (204) to a location upstream of the compressor (122); an oxygen sensor (172) located downstream of the charge air cooler (154) and is coupled to the intake manifold (160) upstream of the intake throttle valve (158); and a controller (12) with computer-readable instructions for: Determining a correction factor for an inlet oxygen sensor (172) based on the PCV flow and charging conditions; and Setting the position of the EGR valve (204) based on an output of the inlet oxygen sensor (172) with respect to the correction factor. [19] System according to claim 18, wherein the determination of the correction factor includes determining a change in the inlet oxygen at the inlet oxygen sensor (172) between the supercharged and the unsupercharged engine operation when both the EGR valve (204) and the drain valve (112) are closed. [20] System according to claim 19, wherein the computer-readable instructions further include instructions for estimating an EGR flow rate based on a change in inlet oxygen due to EGR, wherein the change in inlet oxygen due to EGR is determined by subtracting the correction factor from the output of the inlet oxygen sensor (172).

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