Method and system for controlling engine airflow

Abstract

The present application relates to a method and system for controlling engine airflow with an auxiliary throttle arranged in series with a venturi tube and in parallel with a main intake throttle, and provides a method and system for progressively opening and controlling each of a fuel vapor canister purge valve (CPV), an auxiliary throttle coupled in series with the venturi tube, and a main intake throttle arranged in parallel with the auxiliary throttle valve so as to deliver a desired intake airflow or manifold vacuum to an engine intake manifold. In one example, a method includes actuating the CPV to supply airflow to the engine via a fuel vapor canister while keeping the main throttle valve and the auxiliary throttle valve arranged in parallel with the main throttle valve and in series with the venturi tube closed. The method also includes progressively opening the CPV, then opening the auxiliary throttle valve, and then opening the main throttle valve to achieve a desired intake manifold pressure.

Description

Technical Field

[0001] The present description generally relates to methods and systems for controlling purge flow from a fuel vapor canister and air flow to an intake manifold of an engine through coordinated control of a main intake throttle, a canister purge valve, and an auxiliary throttle arranged in series with a venturi and in parallel with the main intake throttle. Background Art

[0002] The vehicle may be equipped with an evaporative emission control system, such as an on-board fuel vapor recovery system. Such a system captures evaporated hydrocarbons and prevents the release of evaporated hydrocarbons into the atmosphere, such as fuel vapors generated in the vehicle's gasoline tank during refueling. Specifically, evaporated hydrocarbons (HC) are stored in a fuel vapor canister filled with an adsorbent that adsorbs and stores the vapors. Later, when the engine is operating, the evaporative emission control system allows the vapors to be purged into the engine intake manifold for use as fuel. The fuel vapor recovery system may include one or more check valves, ejectors (or venturis), and / or controller-actuated valves to facilitate purging of stored vapors under supercharged or non-supercharged engine operation.

[0003] However, in some vehicles (including vehicles that employ a start / stop engine), the conditions for purging the fuel vapor canister may be limited. In a first mode, when the fuel vapor canister effluent is rich, the purge flow is constrained by adjusting the opening of the canister purge valve to limit the mass of fuel provided by the fuel vapor canister to the intake manifold of the engine. In a second mode, when the fuel vapor canister effluent is lean, the flow through the canister and to the intake manifold may be less constrained (e.g., by opening the canister purge valve). However, due to reduced intake manifold vacuum during certain engine operating conditions (such as engine idle conditions), the maximum total flow rate of air flowing through the fuel vapor canister and to the intake manifold may be limited.

[0004] Orzel et al., in U.S. Pat. No. 5,215,055, show an example method for purging a fuel vapor canister during idle speed. Therein, a bypass throttle located in parallel with the main throttle is controlled based on the difference between the actual idle speed and the desired idle speed. During purging of the fuel vapor canister, the purge flow is reduced when the position of the bypass throttle is less than a preselected fraction of the maximum bypass throttle position.

[0005] However, the inventors herein have recognized potential problems with such a system. As one example, controlling the purge flow from the canister to the engine based on the engine idle speed and the position of the bypass throttle may reduce the duration and opportunity to purge the fuel vapor canister. Additionally, reducing the opening of the canister purge valve and / or the bypass throttle based on the engine idle speed in this manner may result in lower intake manifold vacuum and reduced purging from the fuel vapor canister. As a result, vapors within the fuel vapor canister may accumulate over time and purging of the fuel vapor canister may be inefficient. Summary of the invention

[0006] In one example, the above problem can be solved by a method for an engine, the method comprising: actuating a canister purge valve (CPV) to supply airflow to the engine via a fuel vapor canister while keeping the main throttle and an auxiliary throttle in parallel with the main throttle and arranged in series with the venturi closed; and as the desired intake manifold pressure increases, progressively opening the CPV, then opening the auxiliary throttle, and then opening the main throttle to achieve the desired intake manifold pressure. For example, the opening of the CPV can be increased first while keeping the main throttle and the auxiliary throttle closed to achieve the desired intake manifold pressure. If the desired intake manifold pressure cannot be obtained by fully opening the CPV alone, the opening of the auxiliary throttle can be increased while keeping the main throttle closed to achieve the desired intake manifold pressure. Similarly, if the desired intake manifold pressure cannot be obtained by fully opening the auxiliary throttle and the CPV, the opening of the main throttle can be increased and modulated to deliver to the desired intake manifold pressure. In some embodiments, during engine idle conditions, the desired intake manifold pressure may be the desired intake manifold vacuum. By keeping the main throttle closed as long as possible during engine idle, the jitter of the main throttle may be reduced, thereby reducing wear on the throttle position sensor. In addition, by progressively opening the CPV, then opening the auxiliary throttle, and then opening the main throttle, air is first provided by the fuel vapor canister before air is provided through the main intake path. This may increase the frequency and amount of air drawn through the fuel vapor canister, thereby purging the fuel vapor canister more frequently and keeping the outflow in the canister in a leaner state. By arranging the venturi in series with the auxiliary throttle and then opening the auxiliary throttle, the fuel vapor purge vacuum may be increased, thereby allowing air to continue to be drawn through the canister (however, without the auxiliary throttle, there may not be enough vacuum to continue to draw air through the canister). Based on the power demand from the engine, this progressive opening of the valve may also be performed during non-idle conditions to deliver the desired air mass flow to the engine cylinders.

[0007] It should be understood that the above summary is provided to introduce a selection of concepts further described in the detailed description in a simplified form. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the appended claims. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A schematic diagram of a multi-path fuel vapor recovery system for a vehicle system is shown.

[0009] Figure 2 A flow chart is shown of a method for progressively opening a fuel vapor canister purge valve, a venturi throttle, and a main throttle to deliver airflow to an engine intake system during engine idle operation.

[0010] Figure 3 A flow chart is shown of a method for progressively opening a fuel vapor canister purge valve, a venturi throttle, and a main throttle based on engine power demand when the engine is not at idle.

[0011] Figure 4 A flow chart of a method for diagnosing functionality of a fuel vapor canister purge valve, a venturi throttle, and / or a primary throttle is shown.

[0012] Figure 5 Example relationships between mass flow of air through the selected valve, intake manifold vacuum, and valve opening percentage or duty cycle are shown for each of the canister purge valve, venturi, and main throttle.

[0013] Figure 6 A graphical example of progressively opening a canister purge valve, a venturi throttle, and a main throttle based on a desired mass air flow to the intake manifold is shown. DETAILED DESCRIPTION

[0014] The following description relates to systems and methods for controlling purge flow from a fuel vapor canister and air flow to an intake manifold of an engine through coordinated control of a primary intake throttle, a canister purge valve, and an auxiliary throttle arranged in series with a venturi and in parallel with the primary intake throttle. Figure 1 An example engine system including an intake system having a main throttle, an auxiliary throttle arranged in parallel with the main throttle and coupled in series with a venturi (e.g., an ejector), and a fuel vapor recovery system including a canister purge valve is shown in FIG. During engine idle conditions, a desired intake manifold vacuum and a corresponding air mass flow to the intake manifold may be provided by progressively opening the canister purge valve, opening the auxiliary throttle, and then opening the main throttle. For example, as Figure 2As shown in the method illustrated, when the fuel vapor canister is lean (e.g., the effluent leaving the canister is leaner than stoichiometric), the CPV can be controlled to obtain a desired air mass flow to the intake manifold. Then, if the desired air mass flow cannot be obtained by fully opening the CPV, the opening of the auxiliary throttle can be increased. Similarly, if the desired air mass flow cannot be obtained by fully opening each of the CPV and the auxiliary throttle, the main throttle in the engine intake passage can be opened and used to control the air mass flow to the engine cylinders to a desired level. In this way, the CPV, the auxiliary throttle, and the main throttle can be progressively opened to purge the fuel vapor canister and deliver the desired air mass flow to the engine. If the fuel vapor canister is not lean, the CPV can be first controlled based on the fuel supply demand of the engine, and then when the lean state is reached, the progressive opening of the CPV, the auxiliary throttle, and the main throttle can be primarily initiated. As Figure 3 As shown in the method shown, such progressive opening of the valves can also be used when the engine is not at idle speed, based on engine power demand. In addition, diagnostics can also be performed to ensure the proper operation of the CPV, the auxiliary throttle, and the main throttle. Then, if one of these valves fails, or the motor that controls (e.g., actuates) the auxiliary throttle and the main throttle loses power, the auxiliary throttle and the main throttle can be adjusted to a default position, such as Figure 4 The presented method is shown in Figure 5 An example graph of mass flow for each of the CPV, auxiliary throttle (also referred to herein as a venturi or ejector throttle) as a function of intake manifold vacuum and valve opening percentage or duty cycle percentage is shown in FIG. Figure 6 An example coordinated adjustment of the CPV, auxiliary throttle, and main throttle based on changing engine operating conditions is shown. By placing the venturi in series with the auxiliary throttle and staging the opening of the CPV, auxiliary throttle, and main throttle in this manner, the opportunity to purge and flow air through the fuel vapor canister can be increased, and engine control can be increased and wear on components of the main throttle can be reduced.

[0015] Go to the attached picture, Figure 1 A schematic diagram of a vehicle system 100 is shown. The vehicle system 100 includes an engine system 102 coupled to a fuel vapor recovery system (evaporative emission control system) 154 and a fuel system 106. The engine system 102 may include an engine 112 having a plurality of cylinders 108. The engine 112 includes an engine intake system 23 and an engine exhaust 25. The engine intake system 23 includes a throttle (referred to herein as a primary throttle) 114 fluidly coupled to an engine intake manifold 116 via an intake passage 118.

[0016] An air filter 174 is positioned upstream of the throttle 114 in the intake passage 118. The engine exhaust 25 includes an exhaust manifold 120 leading to an exhaust passage 122, which routes exhaust gas to the atmosphere. The engine exhaust 122 may include one or more emission control devices 124, which may be mounted in a close-coupled position in the exhaust. The one or more emission control devices may include a three-way catalyst, a lean NOx trap, a diesel particulate filter, an oxidation catalyst, etc. It should be understood that other components may be included in the vehicle system, such as various valves and sensors further described below.

[0017] The throttle 114 may be located in the intake passage 118 downstream of a compressor 126 of a boosting device, such as a turbocharger 50 or a supercharger. The compressor 126 of the turbocharger 50 may be disposed between an air filter 174 and the throttle 114 in the intake passage 118. The compressor 126 may be at least partially powered by an exhaust turbine 54 disposed between an exhaust manifold 120 and an emission control device 124 in an exhaust passage 122. The compressor 126 may be coupled to the exhaust turbine 54 via a shaft 56. The compressor 126 may be configured to draw intake air at atmospheric pressure into an air intake system (AIS) 173 and boost it to a higher pressure. Using the boosted intake air, a boosted engine operation may be performed.

[0018] The amount of boost can be controlled at least in part by controlling the amount of exhaust gas directed through the exhaust turbine 54. In one example, when a greater amount of boost is requested, a greater amount of exhaust gas can be directed through the turbine. Alternatively, for example, when a smaller amount of boost is requested, some or all of the exhaust gas can bypass the turbine via a turbine bypass passage controlled by a wastegate (not shown). In some embodiments, there may also be a bypass passage around the compressor, including a compressor bypass valve (not shown). When the throttle inlet pressure exceeds the compressor pressure and the throttle 114 is closed (e.g., low flow), the controller 166 can actuate the compressor bypass valve to open (and thereby recirculate air around the compressor).

[0019] The fuel system 106 may include a fuel tank 128 coupled to a fuel pump system 130. The fuel pump system 130 may include one or more pumps for pressurizing the fuel delivered to the fuel injectors 132 of the engine 112. Although only a single fuel injector 132 is shown, additional injectors may be provided for each cylinder. For example, the engine 112 may be a direct injection gasoline engine, and additional injectors may be provided for each cylinder. It should be understood that the fuel system 106 may be a returnless fuel system, a return fuel system, or various other types of fuel systems. In some examples, the fuel pump may be configured to draw liquid from the tank bottom. As further described below, vapors generated in the fuel system 106 may be routed to a fuel vapor recovery system (evaporative emission control system) 154 via a conduit 134 and a valve (e.g., a fuel tank isolation valve, aka, a vapor barrier valve) 133, and then purged to the engine intake system 23.

[0020] The fuel vapor recovery system 154 includes a fuel vapor retention device, which is depicted as a fuel vapor canister 104 herein. The canister 104 may be filled with an adsorbent capable of binding a large amount of evaporated HC. In one example, the adsorbent used is activated carbon. The canister 104 may receive fuel vapor from the fuel tank 128 via a conduit 134. Although the depicted example shows a single canister, it should be understood that in an alternative embodiment, a plurality of such canisters may be connected together. The canister 104 may be connected to the atmosphere via a vent 136. In some examples, a canister vent valve 172 may be positioned along the vent 136, coupled between the fuel vapor canister and the atmosphere, and may adjust the flow of air and vapor between the canister 104 and the atmosphere. However, in other examples, a canister vent valve may not be included. In one example, the operation of the canister vent valve 172 may be regulated by a canister vent solenoid (not shown). For example, the canister vent valve may be opened or closed based on whether the canister is purged. In some examples, an evaporative level check monitor (ELCM) (not shown) may be disposed in vent 136 and may be configured to control exhaust of undesirable evaporative emissions and / or assist in detecting undesirable evaporative emissions. Additionally, in some examples, one or more oxygen sensors may be positioned in engine intake manifold 116 or coupled to canister 104 (e.g., downstream of the canister) to provide an estimate of canister loading (e.g., canister air-fuel ratio or canister outflow air-fuel ratio). For example, Figure 1As shown, an oxygen sensor 159 is coupled to the canister 104 to provide an estimate of the air-fuel ratio of the outflow from the canister (or the flow purged from the canister during a purge operation). In another example, one or more temperature sensors 157 can be coupled to the canister 104 and / or coupled within the canister 104. When fuel vapor is adsorbed by the adsorbent in the canister, heat (adsorption heat) is generated. Similarly, when fuel vapor is desorbed by the adsorbent in the canister, heat is consumed. In this way, the adsorption and desorption of fuel vapor by the canister can be monitored and estimated based on temperature changes within the canister, and can be used to estimate the canister load.

[0021] Conduit 134 may include a fuel tank isolation valve 133. Among other functions, fuel tank isolation valve 133 may allow fuel vapor canister 104 to remain at a low pressure or vacuum without increasing the rate of fuel evaporation from the tank (which would otherwise occur if the fuel tank pressure were reduced). Fuel tank 128 may hold a variety of fuel blends, including fuels having a range of alcohol concentrations, such as various gasoline-ethanol blends, including E10, E85, gasoline, etc., and combinations thereof.

[0022] The fuel vapor recovery system 154 may include a multi-path purge system 171. The purge system 171 is coupled to the canister 104 via the conduit 150. The conduit 150 may include a canister purge valve (CPV) 158 disposed therein. Specifically, the CPV 158 may regulate the flow of vapor along the conduit 150. The amount and rate of vapor released by the CPV 158 may be determined by the open / closed duty cycle of the CPV solenoid of the CPV 158. In one example, the duty cycle of the CPV solenoid may be determined by the controller 166 in response to engine operating conditions, including, for example, an air-fuel ratio of the canister effluent and / or a desired intake manifold vacuum or a corresponding desired mass air flow into the intake manifold 116 to achieve the desired intake manifold vacuum. By commanding the CPV to close, the controller may seal the fuel vapor canister from the fuel vapor purge system so that no vapor is purged through the fuel vapor purge system. Conversely, by commanding the CPV to open, the controller may enable the fuel vapor purge system to purge vapors from the fuel vapor canister.

[0023] Fuel vapor canister 104 operates to store evaporated hydrocarbons (HC) from fuel system 106. Under some operating conditions, such as during fueling, when liquid is added to the tank, fuel vapors present in the fuel tank may be displaced. The displaced air and / or fuel vapors may be routed from fuel tank 128 to fuel vapor canister 104 and then to the atmosphere through vent 136. However, any gases exiting to the atmosphere via vent 136 may be free of hydrocarbons, which have been removed by the canister. In this way, an increased amount of evaporated HC may be stored in fuel vapor canister 104. During later engine operation, the stored vapors may be released back into the incoming air charge via fuel vapor purge system 171.

[0024] The conduit 150 is coupled to the suction port of the ejector 140 in the ejector system 141 and includes a second check valve (CV2) 170 disposed therein between the ejector 140 and the CPV 158. In some embodiments, the ejector 140 may be referred to as a venturi tube. The second check valve (CV2) 170 may prevent intake air from flowing from the ejector into the conduit 150 while allowing air and fuel vapor to flow from the conduit 150 into the ejector 140. For example, CV2 170 may be a vacuum actuated check valve that opens in response to a vacuum from the ejector 140.

[0025] Conduit 151 couples conduit 150 to intake system 23 at a location within conduit 150 between check valve 170 and CPV 158 and at a location in intake system 23 downstream of throttle 114. For example, conduit 151 may be used to direct fuel vapors from canister 104 to intake system 23, specifically to intake manifold 116, during a purge event using vacuum generated in intake manifold 116. Conduit 151 may include a first check valve (CV1) 153 disposed therein. First check valve (CV1) 153 may prevent intake air from intake manifold 116 from flowing into conduit 150 while allowing fluid and fuel vapors to flow from conduit 150 to intake manifold 116 via conduit 151 during a canister purge event. For example, CV1 may be a vacuum actuated check valve that opens in response to vacuum from intake manifold 116.

[0026] Another conduit 180 couples conduit 150 to a venturi 183 coupled within a parallel conduit 182. Figure 1As shown, the venturi tube 183 is an ejector. The parallel conduit 182 includes an auxiliary throttle 184 disposed therein and arranged in series with the venturi tube 183. The auxiliary throttle 184 may also be referred to herein as an ejector throttle (or venturi tube throttle) because it is coupled in series with the venturi tube 183 and is adjacent to the venturi tube 183. The venturi tube 183 and the auxiliary throttle 184 are arranged in parallel with the throttle valve 114. Specifically, the parallel conduit is coupled to each of the conduit 148 (which is coupled to the intake passage 118 upstream of the throttle valve 114) and the conduit 151 (which is coupled to the intake passage 118 (and / or the intake manifold 116) downstream of the throttle valve 114) and is coupled therebetween. The conduit 180 includes a third check valve (CV3) 181 disposed therein. A third check valve (CV3) 181 may prevent intake air from flowing from intake passage 118 into conduit 150 while allowing fluid and fuel vapor to flow from conduit 150 into intake manifold 116 via conduit 180 during a canister purge event. For example, CV3 may be a vacuum-actuated check valve that opens in response to vacuum from intake manifold 116. Conduit 180 is coupled to conduit 150 closer to CV2 170 than conduit 151 is coupled to conduit 150.

[0027] Conduit 185 is coupled between conduit 180 and conduit 150 downstream of third check valve (CV3) 181 at a location between fuel vapor canister 104 and CPV 158. Figure 1 As shown, an optional second canister purge valve (CPV2) 186 may be disposed in conduit 185. Increasing the duty cycle of CPV2 186 may increase the flow of fuel vapor purge flow (or air flow) from the fuel vapor canister to intake manifold 116 via conduits 185 and 183.

[0028] Returning to the ejector system 141, a conduit 148 may be coupled to the ejector 140 at a first port or inlet 142 (motive flow inlet). The ejector 140 includes a second port 144 (suction flow port) or inlet that couples the ejector 140 to a conduit 150. The ejector 140 is coupled to the intake system 23 via the conduit 148 at a location upstream of the throttle 114 and downstream of the compressor 126. Under boost conditions, the conduit 148 may direct compressed air in the intake conduit 118 downstream of the compressor 126 into the ejector 140 via the port 142.

[0029] The ejector 140 may also be coupled to the intake conduit 118 via a connection or conduit 152 at a location upstream of the compressor 126. Figure 1 As shown, in some examples, a conduit 152 may couple the third port 146 or outlet of the ejector 140 to the intake conduit 118 upstream of the compressor 126 .

[0030] The ejector 140 and / or the ejector 183 may include various check valves disposed therein. For example, in some examples, the ejector 140 may include a check valve positioned adjacent each port in the ejector 140 so that there is a one-way flow of fluid or air at each port. For example, air from the intake duct 118 downstream of the compressor 126 may be directed into the ejector 140 via the inlet port 142, and may flow through the ejector and exit the ejector at the outlet port 146, and then be directed to the intake duct 118 at a location upstream of the compressor 126. Due to the Venturi effect at the inlet port 144, the air flow through the ejector may create a vacuum, so that a vacuum is provided to the duct 150 via the port 144 during the boosted condition. Specifically, a low pressure area is created adjacent to the inlet port 144, which may be used to draw purge vapor from the tank into the ejector 140.

[0031] The ejector 140 includes a nozzle 204 including a throat 212 that converges in a direction from the inlet 142 toward the suction port 144 so that when air flows through the ejector 140 in a direction from the port 142 toward the port 146, a vacuum is created at the port 144 due to the venturi effect. After passing through the converging nozzle and throat, the gas then passes through the diverter section to restore the pressure and make the device efficient, much like a venturi tube. Under certain conditions, such as during boosted engine conditions, this vacuum can be used to assist in fuel vapor purging. In one example, the ejector 140 is a passive component. That is, the ejector 140 is designed to provide a vacuum to the fuel vapor purge system via the conduit 150 to assist in purging under various conditions without active control. Thus, CPV 158 and throttle 114 may be controlled via controller 166, whereas, for example, ejector 140 and ejector 183 may not be controlled via controller 166, nor may they be subject to any other active control. In another example, the ejector may be actively controlled using a variable geometry to adjust the amount of vacuum provided by the ejector to the fuel vapor recovery system via conduit 150.

[0032] During select engine and / or vehicle operating conditions, such as after the emission control device light-off temperature has been reached (e.g., after reaching a threshold temperature after warming up from ambient temperature), and with the engine running, controller 166 may adjust the duty cycle of a canister vent valve solenoid (not shown) and open or maintain canister vent valve 172 open. For example, canister vent valve 172 may remain open except during vacuum testing (described in further detail below) performed on the system. At the same time, controller 166 may adjust the duty cycle of a CPV solenoid (not shown) and open CPV 158. Pressure within fuel vapor purge system 171 may then draw fresh air through vent 136, fuel vapor canister 104, and CPV 158, causing fuel vapor to flow into conduit 150.

[0033] The operation of the ejector 140 within the fuel vapor purge system 171 during vacuum conditions will now be described. The vacuum condition may include an intake manifold vacuum condition. For example, an intake manifold vacuum condition may exist during an engine idle condition, where the manifold pressure is a threshold amount lower than atmospheric pressure. This vacuum in the intake system 23 may draw fuel vapor from the canister into the intake manifold 116 through conduits 150 and 151. In addition, at least a portion of the fuel vapor may flow from conduit 150 into the ejector 140 via port 144. Upon entering the ejector via port 144, the fuel vapor may flow toward port 142 through nozzle 204. Specifically, the throttle inlet pressure (measured at 117) causes the fuel vapor to flow through the throat (e.g., orifice) 212. The ejector 140 is powered by a motive flow entering the ejector 140 at port 142. This creates a low pressure at throat 212 and draws air through the fuel vapor canister, which removes fuel vapor as it passes through the canister. After passing through the nozzle, the fuel vapor and air exit ejector 140 at port 146 and flow through conduit 152 to intake passage 118 and then to compressor 126.

[0034] Additionally, during engine idle conditions, opening the auxiliary throttle 184 positioned in series with the ejector 183 may increase the vacuum in the conduit 180, thereby increasing the flow of air or purge vapor from the fuel vapor canister 104 to the intake manifold 116 via the conduits 150, 151, 185, and / or 180. Thus, under conditions where increased intake manifold vacuum is desired, the controller 166 may increase the duty cycle of the CPV 158 and / or the second CPV 186, and then increase the opening of the auxiliary throttle 184. Specifically, due to the orientation of the orifices in the ejector 183 that converge in a direction from the auxiliary throttle 184 to the location where the ejector 183 is coupled to the conduit 180, the motive flow of the ejector 183 enters at the ejector inlet closest to the auxiliary throttle 184 and is discharged at the port of the ejector 183 that is coupled to the intake manifold 116. Intake flow entering ejector 183 passes from either conduit 180 or conduit 185 toward ejector 183. The motive flow through ejector 183 creates a pressure lower than the pressure at intake manifold 116, which tends to provide enhanced vacuum at conduits 180 and 185. Since the vent is fluidly coupled to CPV 158 and CPV 186, this vacuum can then be used to assist in fuel vapor purging or increase mass air flow into intake manifold 116 during certain engine operating conditions, as further explained below.

[0035] In one example, the ejector 183 may have a relatively large power flow in the range of 3 g / s to 12 g / s between the inlet of the throttle 114 and the intake manifold 116. Under steady-state conditions, there may be a 7+ kPa pressure drop from the throttle inlet to the intake manifold, and the ejector 183 utilizes this pressure drop to enhance vacuum for fuel vapor purge (or crankcase ventilation).

[0036] Next, the operation of the ejector 140 within the fuel vapor purge system 171 during boost conditions will be described. Boost conditions may include conditions during compressor operation. For example, boost conditions may include one or more of high engine load conditions and super-atmospheric intake conditions (where the intake manifold pressure is greater than atmospheric pressure by a threshold amount).

[0037] Since the throttle inlet pressure of the throttle 114 may be the highest pressure point in the system, flow through the conduit 148 is always toward the port 142 of the ejector 140. The flow toward the port 142 is referred to as the motive flow of the ejector 140. When motive flow is present at a significant level, an increased vacuum is created at CV2 170 in the conduit 150.

[0038] In some examples, the fluid may include a mixture of air and fuel. After the fluid flows into the ejector via port 142, it flows through the converging orifice 212 in the nozzle 204 in the direction from port 142 toward outlet 146. Because the diameter of the nozzle gradually decreases in the direction of the flow, a low pressure area is generated in the area of ​​the orifice 212 adjacent to the suction inlet 144. The pressure in the low pressure area may be lower than the pressure in the conduit 150. When present, the pressure difference provides a vacuum to the conduit 150 to draw fuel vapor from the tank 104. The pressure difference may further cause the flow of fuel vapor from the fuel vapor tank through the CPV and into the port 144 of the ejector 140. Upon entering the ejector, the fuel vapor may be drawn out of the ejector via the outlet port 146 together with the fluid from the intake manifold and enter the intake passage 118 at a position upstream of the compressor 126. The operation of the compressor 126 then draws the fluid and fuel vapor from the ejector 140 into the intake passage 118 and through the compressor. After being compressed by compressor 126 , fluid and fuel vapor flow through charge air cooler 156 to be delivered to intake manifold 116 via throttle valve 114 .

[0039] The vehicle system 100 may also include a control system 160. The control system 160 is shown receiving information from a plurality of sensors 162 (various examples of which are described herein) and sending control signals to a plurality of actuators 164 (various examples of which are described herein). As an example, the sensors 162 may include an exhaust gas sensor 125 (located in the exhaust manifold 120) and various temperature sensors and / or pressure sensors disposed in the intake system 23. For example, a pressure or airflow sensor 115 (e.g., manifold pressure) in the intake conduit 118 downstream of the throttle 114, a pressure or airflow sensor 117 (e.g., throttle inlet pressure) in the intake conduit 118 between the compressor 126 and the throttle 114, and a pressure or airflow sensor 119 (e.g., compressor inlet pressure) in the intake conduit 118 upstream of the compressor 126. In some examples, the pressure sensor 119 may include a dedicated atmospheric pressure sensor. Other sensors such as additional pressure sensors, temperature sensors, air-fuel ratio sensors, and composition sensors may be coupled to various locations in the vehicle system 100. As another example, the actuators 164 may include the fuel injectors 132, the throttle valve 114, the auxiliary throttle valve 184, the compressor 126, the fuel pumps of the pump system 130, the CPV 158, the CPV 186, etc. The control system 160 may include an electronic controller 166. The controller 166 may receive commands from the controller 166 based on instructions or code programmed therein corresponding to one or more programs (e.g., instructions) stored in a memory of the controller 166. Figure 1 The present invention relates to a method for detecting input data (e.g., signals) from various sensors, processing the input data, and triggering a control in response to the processed input data. Figure 1 For example, adjusting the opening of the throttle valve 114 or the auxiliary throttle valve 184 may include adjusting an actuator of the throttle valve 114 or the auxiliary throttle valve 184 to adjust a position of a throttle plate and thus adjust an amount of airflow through the throttle valve.

[0040] Additionally, vehicle system 100 may include a crankcase ventilation system including a passage 135 for venting fuel vapors from a crankcase of engine 112 to intake manifold 116 via a valve (eg, a crankcase purge valve) 137 .

[0041] In some examples, the vehicle system 100 may be a hybrid vehicle with multiple torque sources available for one or more vehicle wheels 55. In other examples, the vehicle system 100 is a conventional vehicle with only an engine, or an electric vehicle with only (one or more) motors. In the example shown, the vehicle system 100 includes an engine 112 and a motor 52. The motor 52 may be a motor or a motor / generator. When one or more clutches 59 are engaged, the crankshaft 53 of the engine 112 and the motor 52 are connected to the vehicle wheels 55 via a transmission 57. In the depicted example, a first clutch 59 is disposed between the crankshaft 53 and the motor 52, and a second clutch 59 is disposed between the motor 52 and the transmission 57. The controller 166 may send a signal to the actuator of each clutch 59 to engage or disengage the clutch, thereby connecting or disconnecting the crankshaft 53 with the motor 52 and its connected components, and / or connecting or disconnecting the motor 52 with the transmission 57 and its connected components. The transmission 57 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in a variety of ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0042] The electric machine 52 receives power from the traction battery 58 to provide torque to the vehicle wheels 55. The electric machine 52 may also operate as a generator to provide power to charge the battery 58, such as during braking operations.

[0043] Figure 2 A flow chart of a method 200 for progressively opening a fuel vapor canister purge valve, a venturi throttle, and a main throttle to deliver airflow to an engine intake system during various engine operating conditions is shown. A fuel vapor canister purge valve (CPV) may be one or both valves located in a fuel vapor recovery system, such as Figure 1 The CPV 158 and / or CPV 186 shown in the fuel vapor recovery system 154 of FIG. The venturi throttle may also be referred to herein as an auxiliary throttle or an ejector throttle and may be coupled in series with the venturi (or ejector) and directly upstream thereof, such as Figure 1The auxiliary throttle 184 and the venturi tube 183 shown in FIG. The ejector throttle and the main throttle (such as Figure 1 The main throttle valve 114 is arranged in parallel with the main throttle valve 114 shown, which is located in the intake passage upstream of the intake manifold and the engine cylinder of the engine. Based on instructions stored in the memory of the controller, and in combination with sensors from the engine system (such as those referenced above), the main throttle valve 114 is arranged in parallel with the main throttle valve 114 shown, which is located in the intake passage upstream of the intake manifold and the engine cylinder of the engine. Figure 1 The signal received by the sensor described in the embodiment of the present invention is transmitted to the controller (for example, Figure 1 The controller 166 shown in FIG. 1 may execute instructions for performing method 200 and the remaining methods included herein. According to the method described below, the controller may employ engine actuators of the engine system to adjust engine operation. For example, the controller may employ actuators (such as one or more motors, valve plates, or additional valve actuators) of the CPV, ejector throttle, and main throttle to adjust the valves to different valve positions (with different opening amounts), and / or adjust the duty cycle of the valves based on signals received from one or more engine sensors (such as various air temperature and pressure sensors, engine load sensors, accelerator pedals, throttle position sensors, etc.).

[0044] At 202, the method includes estimating and / or measuring engine operating conditions. Engine operating conditions may include engine speed, engine load and / or power demand, engine output torque, operator torque demand (from an accelerator pedal position sensor in one example), atmospheric pressure, intake manifold pressure and / or temperature, boost pressure, air-fuel ratio of outflow from a fuel vapor canister, mass air flow through various engine passages, etc. At 204, the method includes determining whether the engine is idling (e.g., operating under an engine idle condition). The engine may be operated at idle when the torque demand and / or engine load is below a threshold load and / or when the engine speed is below an engine idle speed (e.g., when the vehicle is stationary). However, during engine idling, fuel may continue to burn at the engine cylinders. If the engine is not idling, the method continues to 206 to determine the engine operating conditions based on the engine power demand and the fuel vapor canister (e.g., Figure 1 The air-fuel ratio (AFR) of the outflow from the canister 104 shown is adjusted by the engine's (one or more) CPVs (e.g., Figure 1 158 and / or CPV 186 shown in FIG), a primary throttle valve (eg, Figure 1 The intake throttle 114 shown) and the ejector throttle (eg, Figure 1184 shown). In one example, adjusting the CPV(s), the primary throttle, and the secondary throttle can include the controller sending electronic signals to actuators of one or more of these valves to adjust the duty cycle or amount of opening of the valve (e.g., by adjusting the position of a throttle plate of the throttle valve) based on an estimate of the engine power demand and the AFR of the fuel vapor canister. For example, the controller can determine a control signal to send to the actuator of the secondary throttle, such as the position of the throttle plate of the secondary throttle based on a determination of the engine power demand (which can be based on an accelerator pedal position or an engine torque demand) and the AFR of the fuel vapor canister (which can be based on a signal received from an oxygen sensor coupled within or near the fuel vapor canister). Referring to FIG. 184, the controller can determine a control signal to send to the actuator of the secondary throttle, such as the position of the throttle plate of the secondary throttle based on a determination of the engine power demand (which can be based on an accelerator pedal position or an engine torque demand) and the AFR of the fuel vapor canister (which can be based on a signal received from an oxygen sensor coupled within or near the fuel vapor canister). Figure 3 Further details of the method at 206 are described.

[0045] Alternatively, at 204, if the engine is operating at idle conditions, the method continues to 208 to determine the desired intake manifold vacuum and the corresponding desired air mass flow to the intake manifold during the engine idle condition. In one example, the desired intake manifold vacuum can be a set pressure value for purging the effluent from the fuel vapor canister. In another example, the desired intake manifold vacuum can be determined by the controller based on the total volume, current load and / or the air-fuel ratio of the fuel vapor canister, wherein the desired intake manifold vacuum increases with increasing load and volume. In another example, the controller determines the desired engine torque, then determines the desired cylinder air charge, and then determines the desired intake manifold pressure (or vacuum) that will result in the cylinder air charge. The controller can then determine the corresponding air mass flow to the intake manifold to achieve (e.g., to obtain) the desired intake manifold vacuum. The controller may determine the desired mass air flow based on the current (e.g., present) engine speed, air temperature (entering the intake manifold), and air pressure (barometric pressure and / or the initial pressure of the air within the intake manifold). In another example, the controller may determine the desired mass air flow based on a calculation using a lookup table stored in memory, where the inputs are the desired intake manifold vacuum, engine speed, air temperature, and air pressure, and the output is the desired mass air flow.

[0046] At 210 , the method includes determining a fuel vapor canister (such as Figure 1 The air-fuel ratio of the contents (e.g., the outflow) of the fuel vapor canister 104 as shown is lean. In one example, if the outflow is leaner than stoichiometry, the outflow of the fuel vapor canister may be lean. In another example, when the fuel-air equivalence ratio is When it is less than 0.5, the outflow of the fuel vapor canister can be determined to be lean, where λ is defined as the air-fuel equivalence ratio (the ratio of actual AFR to the stoichiometric AFR when λ=1). The controller can obtain the oxygen sensor (such as Figure 1 The controller may determine the air-fuel ratio (AFR) of the fuel vapor canister based on the output of an oxygen sensor 159 (shown) and / or an oxygen sensor positioned downstream of the outlet of the fuel vapor canister. In another embodiment, the controller may determine the air-fuel ratio of the effluent within the fuel vapor canister based on (e.g., using an equation or relationship or lookup table stored in a memory of the controller) the duration since the last fueling event and the duration since the last purge event of the fuel vapor canister.

[0047] If the outflow from the fuel vapor canister is not lean (eg, has a relatively large amount of fuel vapor), the method proceeds to 212 to open the CPV(s) (eg, Figure 1158 or CPV 158 and CPV 186 shown in ) and meters the amount of opening of (one or more) CPVs based on the AFR of the purge flow (e.g., effluent) from the canister and the fuel supply demand at the engine cylinders. For example, the controller can determine a control signal sent to the actuator of the CPV, such as an open / closed duty cycle, which is determined based on the determination of the AFR of the effluent from the canister and the fuel supply demand (e.g., the required combustion AFR) at the engine cylinders. For example, the duty cycle of the CPV may have to be controlled so that too much additional fuel (in the form of fuel vapor from the canister) does not enter the engine cylinders. As described above, the AFR of the effluent can be based on the measured AFR, and the engine fuel supply demand can be based on operating conditions such as torque demand, desired combustion AFR, MAF and / or MAP in the manifold. The controller can determine the duty cycle of the CPV by directly considering the determined effluent AFR and the determination of the fuel supply demand, such as reducing the duty cycle as the effluent AFR increases and / or the fuel supply demand decreases. Alternatively, the controller may determine the duty cycle based on a calculation using a lookup table, where the inputs are the fuel vapor canister outflow AFR and the fuel supply demand and the output is the CPV duty cycle. As another example, the controller may make a logical determination (e.g., about the duty cycle of the CPV) based on a logic rule that is a function of the fuel vapor canister outflow AFR and the engine cylinder fuel supply demand. The controller may then generate a control signal that is sent to the actuator of the CPV. The controller may additionally or alternatively track the fuel vapor concentration in or near the intake manifold and / or intake passage. Based on the vapor concentration and the air charge, the controller may determine the fuel required by the fuel injector at the engine cylinder. At 214, the method again includes checking whether the outflow of the fuel vapor canister is lean, as described above with reference to 210. If the outflow is not yet lean, the method loops back to 212 to continue adjusting the duty cycle of (one or more) CPVs based on the AFR of the purge flow and the engine cylinder fuel supply demand. Alternatively, if the outflow of the fuel vapor canister has become lean, the method continues to 216. The method also continues from 210 to 216 .

[0048] At 216, the method includes determining whether the desired mass air flow to the intake manifold is less than the maximum CPV flow at the desired intake manifold vacuum. As described above, the desired mass air flow is the desired mass air flow determined at 208. The maximum CPV flow can be the maximum possible mass air flow through the CPV at the desired intake manifold vacuum (as determined at 208) (e.g., when the duty cycle is actuated to 100%). The controller can use a relationship (such as one or more curves, graphs, or functions / equations) or one or more lookup tables to determine the maximum CPV flow at the desired intake manifold vacuum. As further described below, Figure 5 The graph 505 in FIG. 1 shows different duty cycles for CPV, for example, Figure 1 An example of a relationship between the mass air flow through the CPV 158) as a function of the intake manifold vacuum and the CPV 158 shown in FIG. 1 is provided. The graph may be stored in a memory of the controller in the form of a graph, equation, or lookup table and then referenced by the controller during engine operation to determine or look up the maximum possible flow through the CPV (at 100% duty cycle) for a determined desired intake manifold vacuum. If the desired mass air flow is less than the maximum possible flow through the CPV at the desired intake manifold vacuum, then only the CPV (or one or more CPVs) may be adjusted to provide the desired mass air flow and intake manifold vacuum to the intake manifold. The method then continues to 218 to close (e.g., fully close) the main throttle and the ejector throttle and adjust the amount of opening of the CPV(s) (such as adjusting the open / closed duty cycle) to obtain the desired mass air flow to the intake manifold. In one example, this may include fully opening the CPV(s) (e.g., operating the CPV at a 100% duty cycle) or operating the CPV(s) at a duty cycle between 100% and 0% (e.g., 50%). For example, the controller may use CPV mass flow, intake manifold vacuum, and CPV duty cycle (e.g., Figure 5 ) to determine the duty cycle used to achieve the desired air mass flow to the intake manifold. In one embodiment, adjusting the opening of the CPV(s) at 218 may include adjusting only the main first CPV (such as Figure 1 158) to deliver the desired air mass flow to the intake manifold. In another embodiment, adjusting the opening of the CPV(s) at 218 may include adjusting Figure 1 Each of the first CPV and the second CPV 186 shown in , to deliver the desired air mass flow to the intake manifold. As an example, when the outflow of the fuel vapor canister is rich and the air flow (to the engine cylinders) is relatively low, only CPV 158 can be used to meter the air flow from the canister to the intake manifold. However, when the outflow of the fuel vapor canister is rich or the air flow to the engine is high, both CPV 158 and CPV 186 can be opened. If the engine air flow is high, both CPV 158 and CPV 186 can be fully opened because the amount of fuel vapor they can supply is limited even when the outflow is rich. When the outflow is lean, the air supply requirement at the intake manifold can be met by CPV 158 and / or CPV 186 before opening the auxiliary throttle and the main throttle.

[0049] Alternatively, at 216, if the desired air mass flow is not less than the maximum CPV flow at the desired intake manifold vacuum, the method proceeds to 220 because simply fully opening the CPV (or operating the CPV(s) at their maximum duty cycle) cannot provide the desired air mass flow to the intake manifold. At 220, the method includes fully opening one or both of the CPV(s) (e.g., 100% duty cycle) and determining the additional flow required to achieve the desired air mass flow to the intake manifold (e.g., the remaining flow required to achieve the desired air mass flow after fully opening the CPV(s)). The method proceeds to 222 to determine if the determined additional flow required is less than the maximum possible ejector throttle flow at the desired intake manifold vacuum. The maximum ejector throttle flow may be the maximum possible air mass flow through the ejector throttle at the desired intake manifold vacuum (e.g., when the ejector throttle is actuated to 100% or fully open). The controller may use a relationship (such as one or more curves, graphs, or functions / equations) or one or more lookup tables to determine the maximum ejector throttle flow at a desired intake manifold vacuum. As further described below, Figure 5 The curve 503 in FIG. 1 shows the ejector throttle (eg, Figure 1 An example of a relationship between the mass air flow through the ejector throttle (184) as a function of the intake manifold vacuum and the auxiliary throttle (shown in FIG. 1 ) is provided as an example of a relationship between the mass air flow through the ejector throttle (184) as a function of the intake manifold vacuum and the ejector throttle (184) as a function of the intake manifold vacuum. The graph may be stored in a memory of the controller in a graphical, equation, or lookup table format and then referenced by the controller during engine operation to determine or look up the maximum possible flow through the ejector throttle (at 100% open) for a determined desired intake manifold vacuum. If the required additional flow is less than the maximum possible flow through the ejector throttle at the desired intake manifold vacuum, adjusting the amount of opening of the ejector throttle (in addition to a fully open CPV) may provide the desired mass air flow and intake manifold vacuum to the intake manifold. The method then continues to 224 to maintain the main throttle fully closed and maintain the CPV(s) fully open, and adjust the amount of opening of the ejector throttle (such as adjusting the position of the throttle plate of the ejector throttle to increase the amount of opening through the ejector throttle) to obtain the additional flow required to achieve the desired mass air flow to the intake manifold. In one example, this may include fully opening the ejector throttle (e.g., 100% open) or adjusting the ejector throttle opening to somewhere between 100% open and 0% open (such as 60% open). The controller may use a stored relationship between ejector throttle mass flow, intake manifold vacuum, and ejector throttle opening percentage (e.g., Figure 5The percentage of opening (or amount of opening) of the ejector throttle to achieve the desired additional flow is determined by using the ejector throttle valve as shown in FIG.

[0050] Alternatively, at 222, if the desired additional flow is not less than the maximum ejector throttle flow at the desired intake manifold vacuum, the method continues to 226. At 226, the method includes maintaining the CPV fully open, fully opening the ejector throttle (e.g., actuating the throttle plate of the ejector throttle to 100% open), determining the additional flow required to achieve the desired air mass flow to the intake manifold, and then adjusting the opening amount of the main throttle to achieve the desired additional flow. For example, the additional flow required to achieve the desired air mass flow may be the difference between the desired air mass flow and the sum of the maximum flow through the ejector throttle and each of the (one or more) CPVs at the desired intake manifold vacuum. The controller may determine the opening amount of the main throttle to achieve the desired additional flow using a relationship (such as one or more curves, graphs, or functions / equations) or one or more lookup tables. As further described below, Figure 5 The curve 501 in FIG. 1 shows different opening percentages of the main throttle valve, through the main throttle valve (eg, Figure 1 An example of a relationship between the mass air flow of the main throttle valve 114 as a function of the intake manifold vacuum is shown in FIG. This graph may be stored in a memory of the controller in the form of a graph, equation, or lookup table and then referenced by the controller during engine operation to determine or look up the percentage of opening of the main throttle valve to achieve the additional flow required to achieve the desired mass air flow at the determined desired intake manifold vacuum.

[0051] Each of the methods at 218, 224, and 226 continues to 228, where the method includes determining whether there is an increase in engine power demand (or torque demand), which may indicate a request to exit engine idle operation. If there is a request to increase engine power or torque or to exit engine idle operation, the method continues to 206, as described above. Otherwise, if the engine power or torque demand has not increased, the method may continue to 230 to maintain the current position of the valve (CPV(s), ejector throttle, and main throttle) and continue idle operation. The method then ends.

[0052] Continue to Figure 3, a method 300 for progressively opening (one or more) CPVs, ejector throttles (e.g., venturis or auxiliary throttles), and main throttles based on engine power demand when the engine is not at idle is shown. As described above, method 300 may start from 206 of method 200. Thus, method 300 may start after determining that the engine is not at idle and / or there is an engine power or torque demand above the idle level. Method 300 starts at 302, which determines the engine power demand and the AFR of the fuel vapor canister (e.g., the AFR of the outflow within the fuel vapor canister). As described above with reference to 210 of method 200, the controller may determine the AFR of the outflow in the fuel vapor canister. In addition, in one example, the controller may determine the engine power demand based on the torque demanded by the operator (e.g., based on a signal from a pedal position sensor of an accelerator pedal). In other examples, the controller may determine the engine power demand based on additional engine operating parameters such as engine speed, engine load, torque demand, and / or boost pressure.

[0053] At 304, the method includes determining whether the fuel vapor canister is lean (similar to the method described above for method 200 at 210). If the fuel vapor canister is not lean, then the method continues to 306 to control engine airflow (e.g., airflow to the engine cylinders) by adjusting the ejector throttle and / or the main throttle. At 308, the method includes determining whether a fuel vapor canister purge condition is met. In one example, the fuel vapor canister purge condition may be met when the load of the fuel vapor canister is greater than a threshold load, where the threshold load may be non-zero, such as filling with fuel vapor to 80% or 70% full. The load of the fuel vapor canister may be measured or estimated based on one or more of an output of a temperature sensor or an oxygen sensor coupled to the fuel vapor canister, a time since the last fueling event, and / or a duration of the last fueling event. In another example, the fuel vapor canister purge condition may be met after a fueling event, or if the duration since the last purge event is greater than a threshold amount of time (e.g., 5 hours). If fuel vapor canister purge conditions are not met, the method continues to 310 to maintain the CPV(s) closed (and not purge fuel vapors from the fuel vapor canister) and continue to control engine airflow by adjusting the position of the ejector throttle and the main throttle (in one example, based on engine power demand and desired air-fuel ratio at the engine cylinders).

[0054] Alternatively, if the conditions for purging vapors from the fuel vapor canister are met at 308, the method continues to 312 to open one or more CPVs of the system and then meter (e.g., adjust) the amount of opening (e.g., duty cycle) of the CPV(s) based on the AFR of the purge flow (effluent leaving the canister) and the fuel supply demand at the engine cylinders of the engine, similar to what was explained above with reference to 212 of method 200. The method then continues to 314 to determine if the effluent in the fuel vapor canister has become lean (e.g., as described above, enough fuel vapor has been purged from the canister so that the gases leaving the canister are now lean). If the fuel vapor canister is not yet lean, the method returns to 312. Otherwise, if the fuel vapor canister is lean, the method continues to 316.

[0055] If the canister is determined to be lean at 304 or 314, the method continues to 316. At 316, the method includes closing the main throttle and the ejector throttle (e.g., fully closed), and then controlling the engine airflow to the engine cylinders by adjusting (one or more) CPVs. At 316, the method may include determining the desired intake manifold pressure for the current engine power demand, and then determining the corresponding desired air mass flow to the intake manifold to deliver the desired intake manifold pressure. Similar to what is described at 208 above, the controller may determine the desired air mass flow to the intake manifold to deliver the desired intake manifold pressure based on the current (e.g., current) engine speed, air temperature (entering the intake manifold), and air pressure (atmospheric pressure and / or the initial pressure of the air in the intake manifold). In another example, the controller may determine the desired air mass flow based on a calculation using a lookup table stored in a memory, where the inputs are the desired intake manifold pressure, engine speed, air temperature, and air pressure, and the output is the desired air mass flow. The controller can then use the stored relationship between CPV mass flow, intake manifold pressure, and the duty cycle of the CPV to determine the duty cycle of the CPV that delivers the desired air mass flow to the intake manifold. The stored relationship can be in the form of an equation, a graph, or a lookup table, similar to Figure 5 , and as described above with reference to 218 of method 200. For example, as the desired air mass flow to the intake manifold increases, the controller may actuate the CPV(s) to have a higher open / closed duty cycle.

[0056] The method then proceeds to 318 to determine if the determined desired air mass flow to the intake manifold and engine cylinders is greater than a first threshold. In one example, the first threshold may be the maximum possible air mass flow of the CPV(s). The controller may determine the maximum possible air mass flow through the CPV(s) based on a stored relationship between CPV mass flow, intake manifold pressure, and the duty cycle of the CPV. For example, for a desired intake manifold pressure and at a maximum duty cycle, the controller may use the stored relationship to look up or calculate the maximum possible air mass flow through the CPV(s) (as described above with reference to FIG. Figure 2 And the following reference Figure 5 ). If the desired air mass flow is greater than the maximum air mass flow through the CPV(s) at the maximum duty cycle (e.g., 100% or fully open) and the desired intake manifold pressure, additional air flow may be required to achieve the desired air mass flow. If the desired air mass flow is not greater than the first threshold, the method continues to 320 to keep the main throttle and the ejector throttle closed and adjust the opening of the CPV(s) to achieve the desired air mass flow, as described above at 316, and similarly as described above with reference to 218 of method 200. The method then ends.

[0057] Alternatively, at 318, if the desired air mass flow to the intake manifold is greater than the first threshold, the method continues to 322 to fully open the CPV(s) (or fully open one or both of the CPVs if two CPVs are present in the fuel vapor purge system), maintain the main throttle closed, and control engine airflow by adjusting the amount of opening of the ejector throttle. The method then proceeds to 324 to determine if the determined desired air mass flow to the intake manifold is greater than a second threshold, where the second threshold is greater than the first threshold. In one example, the second threshold may be the sum of the maximum possible air mass flow through the CPV(s) and the maximum possible air mass flow through the ejector throttle. The controller may determine the maximum possible air mass flow through the ejector throttle based on a stored relationship between the ejector throttle mass flow, intake manifold pressure, and the percentage of opening of the ejector throttle. The stored relationship may be in the form of an equation, a graph, or a lookup table, similar to Figure 5 503 in the graph and as described above with reference to 224 of method 200. For example, for a desired intake manifold pressure and at a maximum opening percentage of the ejector throttle, the controller may use the stored relationship to look up or calculate the maximum possible air mass flow through the ejector throttle (as described above with reference to Figure 2 And the following reference Figure 5If the desired air mass flow is greater than the maximum air mass flow through the CPV(s) and the ejector throttle, additional air flow may be required to achieve the desired air mass flow. If the desired air mass flow is not greater than the second threshold, the method continues to 326 to maintain the main throttle closed, maintain the CPV(s) fully open, and adjust the ejector throttle opening percentage using the stored relationship between the ejector throttle air mass flow, intake manifold pressure, and ejector throttle opening percentage to obtain the desired air mass flow, similar to what is described above with reference to 224 of method 200. The method then ends.

[0058] Alternatively, at 324, if the desired air mass flow to the intake manifold is greater than the second threshold, the method continues to 328 to maintain the CPV(s) fully open, fully open the ejector throttle (e.g., to 100% open), and control engine airflow to the desired air mass flow by adjusting the position (opening amount) of the main throttle. The controller may determine the main throttle opening percentage to deliver the desired air mass flow to the intake manifold based on a stored relationship between the main throttle mass flow, intake manifold pressure, and the main throttle opening percentage. The stored relationship may be in the form of an equation, a graph, or a lookup table, similar to Figure 5 501 in the graph and as described above with reference to 226 of method 200. For example, for a desired intake manifold pressure and a desired air mass flow rate at the intake manifold to achieve the desired air mass flow rate, the controller may use the stored relationship to look up or calculate the opening percentage of the primary throttle valve (as described above with reference to Figure 2 And the following reference Figure 5 The method then ends.

[0059] In this manner, a method for an engine may include actuating a canister purge valve (CPV) to supply airflow to the engine via a fuel vapor canister while keeping a primary throttle and an auxiliary throttle arranged in parallel with the primary throttle and in series with a venturi closed; and as a desired intake manifold pressure increases, progressively opening the CPV, then opening the auxiliary throttle, and then opening the primary throttle to achieve the desired intake manifold pressure. In one example, as Figure 2 As shown, actuating the CPV to supply airflow to the engine via the fuel vapor canister is in response to an engine idle condition, and the desired intake manifold pressure is a desired intake manifold vacuum. The method may also include adjusting the duty cycle of the CPV based on a fuel supply demand at the engine cylinder in response to the air-fuel ratio of the outflow of the fuel vapor canister being rich, and when the outflow becomes lean, adjusting the duty cycle of the CPV to increase the opening amount of the CPV and achieve the desired intake manifold pressure. In another example, as Figure 3As shown, actuating the CPV to supply airflow to the engine via the fuel vapor canister in response to the air-fuel ratio of the outflow of the fuel vapor canister being lean while the engine power demand of the engine is greater than a threshold, and the desired intake manifold pressure is based on the engine power demand. The method may also include determining the air mass flow entering the intake manifold of the engine to achieve the desired intake manifold pressure based on the engine speed, air temperature, and air pressure, and progressively opening the CPV, then opening the auxiliary throttle, and then opening the main throttle to obtain the determined air mass flow. In addition, in response to the determined air mass flow being less than the maximum possible CPV flow at the desired intake manifold pressure, the method may include adjusting the opening and closing duty cycle of the CPV to obtain the determined air mass flow while keeping the auxiliary throttle and the main throttle closed. Then, in response to the determined air mass flow being greater than the maximum possible CPV flow at the desired intake manifold pressure, the method may include fully opening the CPV, determining a first additional air mass flow required to achieve the determined air mass flow, and adjusting the opening amount of the auxiliary throttle to achieve the first additional air mass flow while keeping the main throttle closed. The method may then include, in response to the additional air mass flow required to achieve the determined air mass flow being greater than the maximum possible auxiliary throttle flow at the desired intake manifold pressure, fully opening the CPV and the auxiliary throttle, determining a second additional flow required to achieve the determined air mass flow, and adjusting an opening amount of the main throttle to achieve the second additional air mass flow. In one example, the venturi is an ejector, and the auxiliary throttle (also referred to as a venturi throttle or ejector throttle) is coupled upstream of a motive flow inlet of the ejector, and the CPV is coupled upstream of an entraining inlet of the ejector.

[0060] Now go to Figure 4, a method 400 for diagnosing the functioning of (one or more) CPVs, ejector throttles, and / or main throttles is shown. Method 400 begins at 402, which estimates and / or measures engine operating conditions. Engine operating conditions may include engine speed, engine load and / or power demand, engine output torque, operator torque demand (in one example, from an accelerator pedal position sensor), atmospheric pressure, intake manifold pressure and / or temperature, boost pressure, air-fuel ratio of outflow from a fuel vapor canister, mass air flow through various engine passages, positions of various valves of the engine, etc. At 404, the method includes determining whether conditions for valve diagnosis are met. One or more valves of the engine (including (one or more) CPVs, ejector throttles, and main throttles) can be diagnosed for normal operation and determine whether they are in the commanded position (and whether feedback systems such as valve position sensors are reading accurately). In one example, conditions for valve diagnostics may be met after a duration of engine operation or a number of drive cycles or combustion events, after a duration since a last valve diagnostic, and / or in response to one or more diagnostic flags set at a controller. In another example, conditions for valve diagnostics may include the engine operating at idle (e.g., when the engine speed is at or below the engine idle speed) or when the fuel flow of the engine is at a level at which the air-fuel ratio is controlled to stoichiometry. If the conditions for running one or more valve diagnostics are not met, the method continues to 406 to continue adjusting the engine valves (CPV(s), ejector throttle, and main throttle) based on the engine power demand and tank AFR, such as Figure 2-Figure 3 as shown.

[0061] If conditions for performing valve diagnostics for the CPV(s), ejector throttle, and / or main throttle are met at 404, the method continues to 408 to actuate the selected valve(s) to open and closed positions, and measure air flow through the selected valve(s) (or in a passage upstream or downstream of the valve) during actuation, and determine a feedback position based on a position sensor coupled to the selected valve(s). At 410, the method includes determining whether the valve is operating properly (e.g., actuated to the correct position as commanded). In one example, the feedback position can be compared to the measured (or estimated) flow and then used by the controller to determine correct operation of the position sensor and correct positioning of the selected valve(s). If the controller determines that the selected valve(s) are not actuated to the correct (e.g., commanded) position or that one or more components of the selected valve(s) (such as a position sensor) are degraded, the method may continue to 412 to set the degraded valve(s) to a default or unpowered position, set one or more diagnostic codes at the controller, and / or notify the vehicle operator that one or more valves are degraded and require maintenance. In one example, the default or unpowered position of the main throttle and the ejector throttle may be the main throttle fully closed and the ejector throttle fully open. During engine operation, if a motor (e.g., a single motor in one example) that controls both the main throttle and the ejector throttle loses power, the main throttle may be automatically adjusted to a default fully closed position and the ejector throttle may be automatically adjusted to a default fully open position. If instead at 410 the controller determines that the valves are operating properly and are not degraded, the method continues to 414 to adjust the valves based on engine power demand and fuel vapor canister AFR, such as Figure 2-Figure 3 Additionally, with the ejector throttle open and the main throttle closed, maximum engine torque can be modulated by a combination of intake valve actuation, spark retard, and ejector cutout.

[0062] Figure 5 Graph 500 shows an example relationship between mass flow of air through the selected valve, intake manifold vacuum, and valve opening percentage or duty cycle for each of the canister purge valve, ejector throttle, and main throttle. Figure 2-Figure 3 As explained, in one example, Figure 5 The relationship shown in may be stored in a controller memory (e.g., Figure 1 166) and then in Figure 2-Figure 3is referenced during a routine to determine the maximum air mass flow through a selected valve at a desired intake manifold vacuum (or intake manifold pressure during non-idle conditions) and / or to determine the valve opening percentage or duty cycle of the selected valve at the desired intake manifold vacuum and the required additional air mass flow to the intake manifold (to achieve the total desired air mass flow at the intake manifold). Figure 5 An example of a relationship is shown for intake manifold vacuum, but similar relationships between mass flow of air through a selected valve, intake manifold pressure, and valve opening percentage or duty cycle may also be stored in controller memory and used in Figure 3 In addition, for each curve diagram for each valve, multiple duty cycle or opening percentage curves are shown. Although in Figure 5 Only a selection of these curves are shown, but additional curves at different opening percentages or duty cycles are possible and can be presented and stored in the controller memory. In one example, the controller can interpolate between adjacent curves to determine values ​​for opening percentages or valve duty cycles that are not represented by a particular curve. In another example, an equation form of the shown relationship can be stored in the controller memory and can include terms for a particular opening percentage or duty cycle.

[0063] Turning first to graph 501 of diagram 500 , the y-axis shows the flow of air through a primary throttle (eg, Figure 1 501 shows a graph of the mass air flow of the main throttle 114 shown in FIG. 501 , and the intake manifold vacuum is shown on the x-axis. Graph 501 shows a plurality of graphs, each for a different percentage of opening of the main throttle and a sonic flow threshold 516. Specifically, graph 502 is for a fully closed (0% open but with some leakage) throttle position, graph 504 shows a 10% open throttle position, graph 506 shows a 20% open throttle position, graph 508 shows a 40% open throttle position, graph 510 shows a 60% open throttle position, graph 512 shows an 80% open throttle position, and graph 514 shows a 100% open throttle position (e.g., fully open). At the sonic flow threshold 516, graphs 508, 506, and 504 flatten out and remain at a relatively constant mass air flow, even if the intake manifold vacuum increases further.

[0064] Turning to graph 503 of chart 500, the y-axis shows the flow of air through an ejector throttle (eg, Figure 1503 shows a plurality of curves, each for a different percentage of opening of an ejector throttle and a sonic flow threshold 525. Specifically, curve 518 is for a fully closed (0% open but with some leakage) throttle position, curve 520 shows a 20% open throttle position, curve 522 shows a 40% open throttle position, and curve 524 shows a 100% open throttle position (e.g., fully open). At the sonic flow threshold 525, the curve flattens and remains at a relatively constant mass air flow, even if the intake manifold vacuum increases further. As shown in the graph 503, since the ejector throttle includes a throttle in series with an ejector (or venturi), below the sonic flow threshold 525, the curve looks more like a conventional throttle, and above the sonic flow threshold 525, the curve looks more like an ejector / venturi.

[0065] Turning to graph 505 of chart 500, the flow of gas through a tank purge valve (e.g., Figure 1 158 or CPV 186) shown in , and intake manifold vacuum is shown on the x-axis. Graph 505 shows a plurality of curves, each for a different open / closed duty cycle percentage of the CPV and a sonic flow threshold 530. Specifically, curve 526 is for a 50% duty cycle, and curve 528 shows a 100% duty cycle (e.g., fully open). The curves shown in graph 505 may be different than a conventional CPV coupled only to the intake manifold. Specifically, the curves shown in graph 505 are different because they represent flow through a CPV fluidly coupled to a venturi / ejector (e.g., Figure 1 shown, in one example), and thus the CPV is exposed to the ejector's intake rather than the intake manifold.

[0066] As an example, looking at graph 503 for an ejector throttle, the controller can use graph 503 to look up the maximum flow through the ejector throttle for a desired intake manifold vacuum. For example, if the desired intake manifold vacuum is 40 kPa, the maximum flow through the ejector throttle is 10 g / s (see graph 524 at 40 kPa). As another example, if the desired intake manifold vacuum is 20 kPa and the additional flow required to the intake manifold is 7.5 g / s, the controller can determine from graph 503 that the percentage of opening of the ejector throttle should be approximately 40% open (graph 522).

[0067] Figure 6An example graph 600 is shown for progressively opening a canister purge valve, an ejector throttle, and a main throttle based on a desired mass air flow to the intake manifold. Specifically, graph 600 shows changes in engine power demand at graph 602, changes in engine speed relative to engine idle speed 606 at graph 604, changes in fuel vapor canister outflow air-fuel ratio (AFR) relative to stoichiometric air-fuel ratio 610 at graph 608, changes in desired mass air flow to the intake manifold at graph 612, changes in actual mass air flow delivered to the intake manifold at graph 613, CPV (e.g., Figure 1 158 and / or CPV 186) shown in FIG. 6 , the ejector throttle (eg, Figure 1 , and the change in the percentage of opening of the primary throttle valve (eg, Figure 1 . The change in the percentage of opening of the main throttle valve 114) shown in FIG.

[0068] Prior to time t1, the engine power demand may be relatively low (graph 602) and the engine speed may be below the engine idle speed 606 (graph 604). Therefore, the engine may be operated at idle speed (e.g., operated at an engine idle condition). The controller may determine the desired intake manifold vacuum when the engine is idling, which may allow airflow to be pulled through the fuel vapor canister and delivered to the engine. The controller may then determine the desired air mass flow to the intake manifold that will deliver the desired intake manifold vacuum. Since the outflow in the fuel vapor canister is rich prior to time t1 (graph 608), the controller may open the CPV and adjust the amount of opening (e.g., duty cycle) of the CPV based on the fuel supply demand and the canister AFR. For example, since the canister is rich, the CPV may not be actuated to its 100% duty cycle. As the canister AFR decreases, the duty cycle of the CPV increases. While adjusting the CPV to deliver the desired fuel supply to the engine cylinders, the controller may also adjust the injector throttle (graph 616 ) while keeping the main throttle closed (graph 618 ) to deliver the desired air mass flow to the intake manifold.

[0069] At time t1, the tank AFR reaches the stoichiometric air-fuel ratio 610 and then becomes lean. Therefore, in response to the tank AFR being lean and the desired air mass flow to the intake manifold being greater than the maximum CPV flow at the desired intake manifold vacuum, the controller fully opens the CPV. The ejector throttle opening percentage is then increased to move the actual air mass flow to the intake manifold (graph 613) toward the desired air mass flow to the intake manifold (graph 612). The desired air mass flow to the intake manifold can be obtained by fully opening the CPV and increasing the ejector throttle opening percentage to a level less than 10% open (graph 616). Therefore, the main throttle remains closed during engine idle conditions. This can reduce the jitter of the main throttle, thereby reducing degradation of the position sensor of the main throttle.

[0070] At time t2, there is an increase in engine power demand (graph 602) and the engine stops idling (graph 604). Since the tank AFR is still lean at time t2, the main throttle and the ejector throttle can be closed while adjusting the CPV to deliver engine airflow to the intake manifold. At time t3, even though the desired air mass flow to the intake manifold continues to rise (due to the rising engine power demand), the CPV can reach its maximum duty cycle. Therefore, the desired air mass flow to the intake manifold can reach a first threshold at time t3, and the desired air mass flow cannot be obtained by opening only the CPV at time t3. Therefore, the controller begins to increase the opening of the ejector throttle (graph 616) to obtain the desired air mass flow to the intake manifold. However, the main throttle remains closed at this time. Between time t3 and time t4, the percentage opening of the ejector throttle increases as the desired air mass flow to the intake manifold increases until it reaches its maximum 100% opening at time t4. In response to the desired air mass flow continuing to increase above the second threshold at time t4, the desired air mass flow cannot be achieved by fully opening only the CPV and the ejector throttle at time t4. Therefore, the controller begins to increase the main throttle opening percentage (graph 618) while the ejector throttle and CPV remain open. Only after the CPV and ejector throttle are fully opened is the main throttle used to deliver the engine power demand and the desired air mass flow to the engine cylinders. Therefore, Figure 5 An example is shown of progressively opening the CPV, then the ejector throttle, and then the main throttle in a staged manner to achieve a desired air mass flow to the intake manifold, which may be based on a desired intake manifold pressure and / or engine power demand (or torque demand).

[0071] For example, Figure 5An example of a method is shown for adjusting the opening of a canister purge valve (CPV) to supply a determined air flow rate to an intake manifold via a fuel vapor canister while maintaining a main throttle and an auxiliary throttle closed, the auxiliary throttle being arranged in parallel with the main throttle and in series with the venturi (as shown between time t2 and t3); in response to a maximum flow rate of the CPV being lower than the determined air flow rate, fully opening the CPV and increasing the opening of the auxiliary throttle to achieve the determined air flow rate (as shown between time t1 and time t2 and between time t3 and time t4); and in response to a combination of the maximum flow rate of the CPV and the maximum flow rate of the auxiliary throttle being lower than the determined air flow rate, fully opening each of the CPV and the auxiliary throttle and increasing the opening of the main throttle to achieve the determined air flow rate (as shown after time t4). In one example, the opening of the CPV is adjusted to supply the determined air flow rate to the intake manifold in response to an engine idle condition and an air-fuel ratio of an outflow of the fuel vapor canister being leaner than stoichiometry, as shown between time t1 and time t2. In another example, the determined air flow to the intake manifold is an air flow at which a desired intake manifold vacuum is achieved during engine idle conditions, and the determined air flow is further determined based on one or more of engine speed, air temperature, and air pressure. The method may also include, in response to the air-fuel ratio of the outflow being richer than stoichiometry, first adjusting the opening of the CPV based on a fuel supply demand at the engine to purge vapors from the fuel vapor canister to the intake manifold, and then in response to a transition in the air-fuel ratio from rich to lean, increasing the opening of the CPV and adjusting the opening amount based on the determined air flow (as shown before time t1 and between time t1 and time t2).

[0072] In this manner, an engine system including a primary throttle, an auxiliary throttle coupled in series with a venturi and coupled in parallel with the primary throttle, and a fuel vapor recovery system having a canister purge valve (CPV) fluidly coupled to the venturi can be controlled to deliver a desired airflow and / or intake manifold vacuum to an intake manifold upstream of an engine cylinder. Specifically, when the outflow of a fuel vapor canister of the fuel vapor recovery system is determined to be lean, the CPV, the auxiliary throttle, and the primary throttle can be progressively opened in a staged manner to deliver a desired air mass flow to an intake manifold that delivers a desired intake manifold vacuum (during idle) or intake manifold pressure (during non-idle conditions). For example, the controller can first open the CPV while keeping the primary throttle and the auxiliary throttle closed, and then only open the ejector throttle when the desired air mass flow to the intake manifold cannot be obtained by the CPV alone. The ejector throttle can then be used to deliver the desired air mass flow while the CPV is fully open and the main throttle is fully closed. Then, when the desired air mass flow cannot be obtained by the additional opening of the ejector throttle, after fully opening the CPV and the ejector throttle, the controller can open the main throttle and adjust the opening amount to deliver the desired air mass flow to the intake manifold. The technical effect of "actuating the CPV to supply air flow to the engine via the fuel vapor canister while keeping the main throttle and the auxiliary throttle arranged in parallel with the main throttle and in series with the venturi closed; and as the desired intake manifold pressure increases, gradually opening the CPV, then opening the auxiliary throttle, and then opening the main throttle to achieve the desired intake manifold pressure" is to reduce the jitter of the main throttle, thereby reducing wear on the throttle position sensor and / or the motor of the main throttle, and increase the frequency and amount of air drawn through the fuel vapor canister, thereby purging the fuel vapor canister more frequently and keeping the outflow in the canister in a leaner state. Additionally, by placing a venturi in series with the auxiliary throttle and then opening the auxiliary throttle, intake manifold vacuum may be increased, thereby allowing air to continue to be drawn through the canister (however, without the auxiliary throttle, there may not be sufficient vacuum to continue to draw air through the canister).

[0073] As one embodiment, a method for an engine includes actuating a canister purge valve (CPV) to supply airflow to the engine via a fuel vapor canister while keeping a main throttle and an auxiliary throttle arranged in parallel with the main throttle and in series with a venturi closed; and as a desired intake manifold pressure increases, progressively opening the CPV, then opening the auxiliary throttle, and then opening the main throttle to achieve a desired intake manifold pressure. In a first example of the method, actuating the CPV to supply airflow to the engine via a fuel vapor canister is responsive to an engine idle condition, and wherein the desired intake manifold pressure is a desired intake manifold vacuum. A second example of the method optionally includes the first example, and further includes adjusting a duty cycle of the CPV based on a fuel supply demand at an engine cylinder in response to an air-fuel ratio of an outflow of the fuel vapor canister being rich, and adjusting the duty cycle of the CPV to increase the amount of opening of the CPV and achieve a desired intake manifold pressure when the outflow becomes lean. The third example of the method optionally includes one or more of the first and second examples, and further includes, wherein actuating the CPV to supply airflow to the engine via the fuel vapor canister is responsive to the air-fuel ratio of the outflow of the fuel vapor canister being lean while the engine power demand of the engine is greater than a threshold, and wherein the desired intake manifold pressure is based on the engine power demand. The fourth example of the method optionally includes one or more of the first to third examples, and further includes determining the air mass flow entering the intake manifold of the engine to achieve the desired intake manifold pressure based on engine speed, air temperature, and air pressure, and progressively opening the CPV, then opening the auxiliary throttle, and then opening the main throttle to obtain the determined air mass flow. The fifth example of the method optionally includes one or more of the first to fourth examples, and further includes adjusting the opening and closing duty cycle of the CPV to obtain the determined air mass flow in response to the determined air mass flow being less than the maximum possible CPV flow at the desired intake manifold pressure, while keeping the auxiliary throttle and the main throttle closed. The sixth example of the method optionally includes one or more of the first to fifth examples, and further includes, in response to the determined air mass flow being greater than the maximum possible CPV flow at the desired intake manifold pressure, fully opening the CPV, determining a first additional air mass flow required to achieve the determined air mass flow, and adjusting an opening amount of the auxiliary throttle valve to achieve the first additional air mass flow while keeping the main throttle valve closed. The seventh example of the method optionally includes one or more of the first to sixth examples, and further includes, in response to the additional air mass flow required to achieve the determined air mass flow being greater than the maximum possible auxiliary throttle valve flow at the desired intake manifold pressure, fully opening the CPV and the auxiliary throttle valve, determining a second additional flow required to achieve the determined air mass flow, and adjusting an opening amount of the main throttle valve to achieve the second additional air mass flow.An eighth example of the method optionally includes one or more of the first to seventh examples, and also includes wherein the venturi is an ejector, wherein the auxiliary throttle is coupled upstream of a motive flow inlet of the ejector, and the CPV is coupled upstream of a suction inlet of the ejector, and wherein progressively opening the CPV, then opening the auxiliary throttle, and then opening the main throttle includes not opening the auxiliary throttle until the CPV is fully open, and not opening the main throttle until both the CPV and the auxiliary throttle are fully open.

[0074] As another embodiment, a method for an engine includes adjusting an opening of a canister purge valve (CPV) to supply a determined air flow rate to an intake manifold via a fuel vapor canister while maintaining a main throttle and an auxiliary throttle closed, the auxiliary throttle being arranged in parallel with the main throttle and in series with a venturi; in response to a maximum flow rate of the CPV being lower than the determined air flow rate, fully opening the CPV and increasing the opening of the auxiliary throttle to achieve the determined air flow rate; and in response to a combination of a maximum flow rate of the CPV and a maximum flow rate of the auxiliary throttle being lower than the determined air flow rate, fully opening each of the CPV and the auxiliary throttle and increasing the opening of the main throttle to achieve the determined air flow rate. In a first example of the method, adjusting the opening of the CPV to supply the determined air flow rate to the intake manifold is in response to an engine idle condition and an air-fuel ratio of an outflow of the fuel vapor canister being leaner than stoichiometry. The second example of the method optionally includes the first example and further includes, wherein the determined air flow to the intake manifold is an air flow at which a desired intake manifold vacuum is achieved during engine idle conditions, and wherein the determined air flow is further determined based on one or more of engine speed, air temperature, and air pressure. The third example of the method optionally includes one or more of the first example and the second example, and further includes, in response to the air-fuel ratio of the outflow being richer than stoichiometry, first adjusting the opening of the CPV based on the fuel supply demand at the engine to purge vapor from the fuel vapor canister to the intake manifold, and then in response to the air-fuel ratio changing from rich to lean, increasing the opening of the CPV and adjusting the opening amount based on the determined air flow. The fourth example of the method optionally includes one or more of the first to third examples, and further includes, wherein the venturi is an ejector including a motive flow inlet, an outlet, and an intake inlet, and wherein the auxiliary throttle is coupled upstream of the motive flow inlet, the CPV is coupled upstream of the intake inlet, and the outlet is fluidly coupled to the intake manifold downstream of the main throttle.

[0075] A system for an engine includes: a main throttle disposed in an intake passage of the engine upstream of an intake manifold; an auxiliary throttle disposed in parallel with the main throttle and in series with a venturi, the venturi being positioned downstream of the auxiliary throttle in a first passage disposed in parallel with the intake passage; an evaporative emission system including: a fuel vapor canister coupled to a fuel tank; and a first canister purge valve (CPV) disposed in a second passage, the second passage being fluidly coupled to each of the fuel vapor canister, the venturi, and the intake passage downstream of the main throttle; and a controller having computer readable instructions stored in a memory, the computer readable instructions being used to: during engine idle operation and in response to The air-fuel ratio of the outflow in the fuel vapor tank is lean, the main throttle valve and the auxiliary throttle valve are closed, and the desired intake manifold vacuum and the corresponding desired air mass flow entering the intake manifold are determined; in response to the desired air mass flow being less than a first threshold flow, the opening amount of the first CPV is increased, while the main throttle valve and the auxiliary throttle valve remain closed; in response to the desired air mass flow being less than a second threshold flow, the first CPV is fully opened and the opening amount of the auxiliary throttle valve is increased while the main throttle valve remains closed, the second threshold being greater than the first threshold; and in response to the desired air mass flow being less than a third threshold flow, the first CPV and the auxiliary throttle valve are fully opened, and the opening amount of the main throttle valve is increased, the third threshold being greater than the second threshold. In a first example of the system, the computer-readable instructions also include instructions for: during engine idle operation and in response to an air-fuel ratio of the outflow in the fuel vapor canister being rich, closing the main throttle and the auxiliary throttle, and adjusting the opening amount of the first CPV based on the air-fuel ratio of the outflow and the fuel supply demand at the engine; in response to the air-fuel ratio of the outflow becoming lean, determining a desired intake manifold vacuum and a corresponding desired air mass flow entering the intake manifold, and increasing the opening amount of the first CPV to obtain the desired air mass flow while the main throttle and the auxiliary throttle remain closed; in response to the desired air mass flow being less than a second threshold flow, fully opening the first CPV and increasing the opening amount of the auxiliary throttle while the main throttle remains closed; and in response to the desired air mass flow being less than a first threshold flow, fully opening the first CPV and the auxiliary throttle, and increasing the opening amount of the main throttle. A second example of the system optionally includes the first example and further includes, wherein the computer readable instructions further include instructions for: during engine operation during a non-idle period, when the engine load exceeds a threshold load and in response to an air-fuel ratio of the outflow in the fuel vapor canister being lean, closing the main throttle and the auxiliary throttle, and controlling engine airflow to a level based on a current engine power demand by adjusting an opening amount of the first CPV; and as the engine power demand increases, progressively opening the auxiliary throttle and then opening the main throttle to deliver the level of engine airflow based on the current engine power demand.A third example of the system optionally includes one or more of the first and second examples, and further includes a single motor that controls and actuates each of the auxiliary throttle and the main throttle, and wherein the computer-readable instructions further include instructions for the following operations: in response to a diagnosis indicating degraded function of one or more of the auxiliary throttle and the main throttle, adjusting the main throttle and the auxiliary throttle to a default unpowered position, wherein the default unpowered position includes the main throttle fully closed and the auxiliary throttle fully open. A fourth example of the system optionally includes one or more of the first to third examples, and further includes a second canister purge valve disposed in a third passage, the third passage coupled between the second passage and the fourth passage upstream of the first CPV, the fourth passage coupled between the second passage and the first venturi. A fifth example of the system optionally includes one or more of the first to fourth examples, and further includes a second venturi coupled in a fifth passage, the fifth passage coupled between the intake passage upstream of the compressor and the intake passage downstream of the charge air cooler and upstream of the main throttle, wherein the second passage is coupled to the suction inlet of the second venturi.

[0076] In another representation, a method for an engine includes: during a first condition when the outflow from a fuel vapor canister is lean, adjusting the opening of a canister purge valve (CPV) to supply a determined air flow rate to an intake manifold via the fuel vapor canister while maintaining a main throttle and an auxiliary throttle closed, the auxiliary throttle being arranged in parallel with the main throttle and in series with a venturi; after fully opening the CPV, opening the auxiliary throttle to achieve the determined air flow rate while maintaining the main throttle closed; and after fully opening the auxiliary throttle, opening the main throttle to achieve the determined air flow rate; and during a second condition when the outflow from the fuel vapor canister is rich, first adjusting the opening of the CPV based on a fuel supply demand at the engine to purge vapors from the fuel vapor canister to the intake manifold, and then increasing the opening of the CPV and adjusting the opening amount based on the determined air flow rate in response to an air-fuel ratio transition from rich to lean. In one example, when the outflow from the fuel vapor canister transitions from rich to lean, the first condition may be immediately followed by the second condition in the same drive cycle (e.g., Figure 6 as shown in the example shown).

[0077] In one example, the method may include determining whether the outflow from the fuel vapor canister is lean, and in response thereto adjusting the opening of a canister purge valve (CPV) to supply a determined air flow rate to the intake manifold via the fuel vapor canister while maintaining a main throttle and an auxiliary throttle closed, the auxiliary throttle being arranged in parallel with the main throttle and in series with the venturi; after fully opening the CPV, opening the auxiliary throttle to achieve the determined air flow rate while maintaining the main throttle closed; and after fully opening the auxiliary throttle, opening the main throttle to achieve the determined air flow rate; and determining whether the outflow from the fuel vapor canister is rich (which may not be lean), and in response thereto, first adjusting the opening of the CPV based on a fuel supply demand at the engine to purge vapors from the fuel vapor canister to the intake manifold, and then in response to a transition of the air-fuel ratio from rich to lean, increasing the opening of the CPV and adjusting the opening amount based on the determined air flow rate. In some examples, while or during determining whether the outflow from the fuel vapor canister is lean or has transitioned from rich to lean, adjusting the opening of the CPV to purge vapors from the fuel vapor canister to the intake manifold based on a fueling demand at the engine is performed. Then, upon determining that the outflow from the fuel vapor canister has transitioned from lean to rich, the method transitions from adjusting the opening of the CPV based on the fueling demand of the engine to adjusting the opening of the CPV to supply the determined air flow to the intake manifold.

[0078] In another example, a system for an engine may include a controller having a memory with computer readable instructions for: determining whether the outflow of the fuel vapor canister is lean based on the output of an oxygen sensor coupled to the fuel vapor canister, and in response thereto adjusting the opening of a canister purge valve (CPV) to supply a determined air flow rate to an intake manifold via the fuel vapor canister while keeping a main throttle valve and an auxiliary throttle valve closed, the auxiliary throttle valve being arranged in parallel with the main throttle valve and in series with the venturi tube; after fully opening the CPV, opening the auxiliary throttle valve; The invention relates to a method for controlling the air flow rate of the fuel vapor canister and the control system of the present invention. The invention relates to a method for controlling the air flow rate of the fuel vapor canister and the control system of the present invention. The invention relates to a method for controlling the air flow rate of the fuel vapor canister and the control system of the present invention. The invention relates to a method for controlling the air flow rate of the fuel vapor canister and the control system of the present invention.

[0079] It should be noted that the example control and estimation procedures included herein can be used with various engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-volatile memory and can be performed by a control system including a controller combined with various sensors, actuators, and other engine hardware. The dedicated procedures described herein can represent any number of processing strategies, such as one or more of event-driven, interrupt-driven, multi-tasking, multi-threading, etc. In this way, the various actions, operations, and / or functions shown can be performed in the program shown, executed in parallel, or omitted in some cases. Similarly, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. Depending on the specific strategy used, one or more of the actions, operations, and / or functions shown can be repeatedly performed. In addition, the described actions, operations, and / or functions can be represented by diagrams of codes programmed into a non-volatile memory of a computer-readable storage medium in an engine control system, wherein the actions are performed by executing instructions in the system, and the system includes various engine hardware components combined with an electronic controller.

[0080] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be viewed in a limiting sense, as many variations are possible. For example, the above techniques can be applied to V-6, I-4, I-6, V-12, opposed 4 cylinders, 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 disclosed herein, and other features, functions, and / or properties.

[0081] The following claims specifically point out certain combinations and subcombinations deemed novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. It should be understood that these claims include combinations of one or more of these elements, and neither require nor exclude two or more of these elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or characteristics may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal to, or different in scope from the original claims, are also deemed to be included within the subject matter of the present disclosure.

Claims

1. A method for an engine, comprising: actuating a canister purge valve (CPV) to supply airflow to the engine via a fuel vapor canister while maintaining a primary throttle valve and an auxiliary throttle valve connected in parallel with the primary throttle valve and arranged in series with a venturi closed; as well as As the desired intake manifold pressure increases, progressively opening the CPV, then opening the auxiliary throttle valve, and then opening the main throttle valve to achieve the desired intake manifold pressure, wherein the venturi is an ejector, wherein the auxiliary throttle is coupled upstream of a motive flow inlet of the ejector, and the CPV is coupled upstream of a suction inlet of the ejector, and wherein progressively opening the CPV, then opening the auxiliary throttle, and then opening the main throttle includes not opening the auxiliary throttle until the CPV is fully open, and not opening the main throttle until the CPV and the auxiliary throttle are fully open. 2 . The method of claim 1 , wherein the CPV is actuated to supply airflow to the engine via the fuel vapor canister in response to an engine idle condition, and wherein the desired intake manifold pressure is a desired intake manifold vacuum.

3. The method of claim 2 further comprising adjusting a duty cycle of the CPV based on a fueling demand at an engine cylinder in response to an air / fuel ratio of the effluent from the fuel vapor canister being rich, and adjusting the duty cycle of the CPV to increase an opening amount of the CPV and achieve the desired intake manifold pressure as the effluent becomes lean.

4. The method of claim 1 , wherein actuating the CPV to supply airflow to the engine via the fuel vapor canister is responsive to an air-fuel ratio of an outflow of the fuel vapor canister being lean while an engine power demand of the engine is greater than a threshold, and wherein the desired intake manifold pressure is based on the engine power demand.

5. The method of claim 1 further comprising determining an air mass flow into an intake manifold of the engine to achieve the desired intake manifold pressure based on engine speed, air temperature, and air pressure, and progressively opening the CPV, then opening the auxiliary throttle valve, and then opening the main throttle valve to obtain the determined air mass flow.

6. The method of claim 5 further comprising, in response to the determined mass air flow being less than the maximum possible CPV flow at the desired intake manifold pressure, adjusting an opening and closing duty cycle of the CPV to achieve the determined mass air flow while maintaining the auxiliary throttle valve and the main throttle valve closed.

7. The method of claim 5 further comprising, in response to the determined air mass flow being greater than the maximum possible CPV flow at the desired intake manifold pressure, fully opening the CPV, determining a first additional air mass flow required to achieve the determined air mass flow, and adjusting an opening amount of the auxiliary throttle valve to achieve the first additional air mass flow while maintaining the main throttle valve closed.

8. The method of claim 7 further comprising, in response to the first additional air mass flow required to achieve the determined air mass flow being greater than a maximum possible auxiliary throttle flow at the desired intake manifold pressure, fully opening the CPV and the auxiliary throttle, determining a second additional air mass flow required to achieve the determined air mass flow, and adjusting an opening amount of the main throttle to achieve the second additional air mass flow.

9. A system for an engine, comprising: a main throttle valve disposed in an intake passage of the engine upstream of an intake manifold; an auxiliary throttle arranged in parallel with the main throttle and in series with a first venturi tube, the first venturi tube being positioned downstream of the auxiliary throttle valve in a first passage arranged in parallel with the intake passage; Evaporative emission system, comprising: a fuel vapor canister coupled to the fuel tank; and a first canister purge valve, or first CPV, disposed in a second passage fluidly coupled to each of the fuel vapor canister, the first venturi, and the intake passage downstream of the primary throttle; and A controller having computer readable instructions stored in a memory for: during engine idle operation and in response to an air-fuel ratio of the outflow in the fuel vapor canister being lean, closing the primary throttle valve and the auxiliary throttle valve and determining a desired intake manifold vacuum and a corresponding desired mass air flow into the intake manifold; In response to the desired air mass flow being less than a first threshold flow rate, increasing an opening amount of the first CPV while the primary throttle valve and the auxiliary throttle valve remain closed; In response to the desired air mass flow rate being less than a second threshold flow rate, fully opening the first CPV and increasing the opening amount of the auxiliary throttle valve while the main throttle valve remains closed, the second threshold being greater than the first threshold; and In response to the desired air mass flow being less than a third threshold flow rate, fully opening the first CPV and the auxiliary throttle valve, and increasing an opening amount of the main throttle valve, The third threshold is greater than the second threshold.

10. The system of claim 9, wherein the computer-readable instructions further comprise instructions for: during idle operation of the engine and in response to the air-fuel ratio of the effluent in the fuel vapor canister being rich, closing the primary throttle valve and the auxiliary throttle valve and adjusting the opening amount of the first CPV based on the air-fuel ratio of the effluent and a fueling demand at the engine; determining the desired intake manifold vacuum and a corresponding desired air mass flow into the intake manifold in response to the air-fuel ratio of the outflow becoming lean, and increasing the opening amount of the first CPV to achieve the desired air mass flow while the primary throttle valve and the auxiliary throttle valve remain closed; In response to the desired air mass flow being less than the second threshold flow rate, fully opening the first CPV and increasing the opening amount of the auxiliary throttle valve while the primary throttle valve remains closed; as well as In response to the desired air mass flow being less than the third threshold flow, the first CPV and the auxiliary throttle valve are fully opened, and the opening amount of the primary throttle valve is increased.

11. The system of claim 9, wherein the computer-readable instructions further comprise instructions for: During engine operation during non-idle periods, when engine load exceeds a threshold load and in response to the air-fuel ratio of the outflow in the fuel vapor canister being lean, closing the primary throttle valve and the auxiliary throttle valve and controlling engine airflow to a level based on current engine power demand by adjusting an opening amount of the first CPV; and As the engine power demand increases, the auxiliary throttle valve is progressively opened, and then the primary throttle valve is opened, to deliver the level of engine airflow based on the current engine power demand.

12. The system of claim 9 further comprising a single motor that controls and actuates each of the auxiliary throttle valve and the main throttle valve, and wherein the computer-readable instructions further include instructions for: in response to a diagnosis indicating degraded function of one or more of the auxiliary throttle valve and the main throttle valve, adjusting the main throttle valve and the auxiliary throttle valve to a default unpowered position, wherein the default unpowered position includes the main throttle valve fully closed and the auxiliary throttle valve fully open.

13. The system of claim 9, further comprising a second tank purge valve disposed in a third passage coupled between the second passage upstream of the first CPV and a fourth passage coupled between the second passage and the first venturi.

14. The system of claim 9 further comprising a second venturi coupled in a fifth passage, the fifth passage coupled between the intake passage upstream of a compressor and the intake passage downstream of a charge air cooler and upstream of the primary throttle, wherein the second passage is coupled to a suction inlet of the second venturi.

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