Wastegate control to reduce intercooler condensation

Abstract

Method for an engine (10), comprising: Adjusting a wastegate (26) in response to condensate formation conditions in a charge air cooler (80) when an intake pressure is higher than required to produce a manifold pressure required for a torque demand.

Description

Background / Brief description

[0001] US 2010 / 0 077 745 A1 discloses a wastegate control system and method. US 2011 / 0 155 112 A1 discloses an internal combustion engine. DE 10 2013 216 108 A1 discloses a method for controlling a variable charge air cooler. Engines may use a turbocharger or supercharger to compress ambient air entering the engine to increase power. The compression of the air can cause an increase in air temperature, which is why an intercooler or charge air cooler (CAC) may be used to cool the heated air, thereby increasing its density and further increasing the potential power of the engine. Condensation may form in the CAC when the ambient air temperature decreases or during humid or rainy weather conditions, cooling the intake air to below the dew point of water. Furthermore, if the charge air entering the CAC is pre-compressed (e.g.Condensation can form when the CAC temperature drops below the dew point (i.e., intake pressure and boost pressure are higher than atmospheric pressure). As a result, condensate can accumulate at the bottom of the CAC or in the internal passages and cooling turbulators. When torque increases, such as during acceleration, increased mass air flow can entrain condensate from the CAC, draw it into the engine, and increase the likelihood of engine misfire and combustion instability.

[0002] Engines may use a wastegate to redirect exhaust flow around a turbocharger turbine to control an amount of boost delivered to an engine intake manifold. For example, opening a wastegate may reduce boost and intake pressure. One approach to controlling boost and / or intake pressure includes actively controlling the wastegate. An exemplary approach is presented by Hartman et al. in US 6,779,344. Therein, a wastegate is adjusted so that an actual boost pressure corresponds to a desired boost pressure. The desired boost pressure may be based on a desired manifold pressure (which is based on mass air flow) and a compressor surge characteristic.

[0003] However, the inventors herein have recognized a potential problem with such systems. As an example, controlling the wastegate in this manner may cause the wastegate to remain closed under conditions when increased boost is not required by a torque demand. Consequently, the closed wastegate may build up intake pressure upstream of the throttle, thereby increasing the possibility of condensate formation in the CAC.

[0004] The problem is solved with the features of the independent claims. Preferred embodiments thereof are specified in the further claims. In one example, the aforementioned problems may be overcome by a method for adjusting a wastegate in an engine to lower an intake pressure in response to condensate formation conditions in the charge air cooler. Specifically, a wastegate may be opened in response to condensate formation conditions in the charge air cooler when an intake pressure between a compressor and a throttle (e.g., a pre-throttle pressure) is higher than required to generate a manifold pressure required for a torque demand and the engine is under steady-state conditions. In one example, condensate formation conditions include an intake pressure higher than atmospheric pressure (e.g., an intake pressure ratio greater than 1).In another example, condensate formation conditions include humidity higher than a threshold. After opening the wastegate to lower intake pressure, the wastegate may be closed in response to one or more of the intake pressure decreasing to atmospheric pressure and / or an increase in torque demand. Further, under certain engine operating conditions, in addition to opening the wastegate, a compressor recirculation valve may be opened to further lower intake pressure.

[0005] It should be understood that the foregoing summary is provided to introduce, in a simplified form, a selection of concepts described in more detail in the detailed description. It is not intended to reveal essential or principal features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages mentioned previously or elsewhere in this disclosure. Short description of the drawings Fig. 1 is a schematic diagram of an exemplary engine system including a charge air cooler. Fig. 2 is a flowchart illustrating a method for adjusting a wastegate and / or a compressor recirculation valve to reduce condensate formation in a charge air cooler based on engine operating conditions. Fig. 3 is a flowchart illustrating a method for adjusting a wastegate to lower intake pressure and subsequently reduce condensate formation in a charge air cooler. Fig. 4 is a flowchart illustrating a method for adjusting a compressor recirculation valve to lower intake pressure and subsequently reduce condensate formation in a charge air cooler. Fig. 5 is a graph illustrating example adjustments of a wastegate and a compressor recirculation valve based on engine operating conditions. Detailed description

[0006] The following description relates to systems and methods for adjusting a wastegate and / or a compressor recirculation valve in response to condensate formation conditions in a charge air cooler (CAC). An engine system, such as the one in Fig. 1 may include a turbocharger with exhaust gas flow through a turbine that drives a compressor. The engine may include a wastegate and a compressor recirculation valve (CRV) operable to redirect airflow around the turbine and compressor, respectively. Accordingly, opening the wastegate and / or the CRV may reduce boost to thereby lower intake pressure measured upstream of an intake throttle and downstream of a charge air cooler (CAC) and reduce the possibility of condensate forming in the CAC. Under select driving conditions, such as when intake pressure is higher than required to measure intake manifold pressure (MAP),intake manifold pressure) required for a torque demand, an engine controller may open the wastegate and / or the CRV to lower intake pressure and subsequently reduce condensate buildup in the CAC. In this way, the controller may open the wastegate and / or the CRV to lower intake pressure if the MAP required for the torque demand can be generated without boost. Methods for adjusting the wastegate and / or the CRV to lower intake pressure based on engine operating conditions are described at . Fig. 2 to 4. Fig. Figure 5 illustrates example wastegate and CRV adjustments based on CAC condensate formation conditions and additional engine operating conditions.

[0007] Fig. 1 is a schematic diagram illustrating an example engine 10 that may be included in a propulsion system of a motor vehicle. The engine 10 is shown with four cylinders or combustion chambers 30. However, other numbers of cylinders may be used in accordance with the present disclosure. The engine 10 may be controlled at least in part by a control system including a controller 12 and by inputs from a vehicle operator 132 via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. Each combustion chamber (e.g., cylinder) 30 of the engine 10 may include combustion chamber walls with a piston (not shown) positioned therein. The pistons may be coupled to a crankshaft 40 such that up and down movement of the piston is translated into rotational movement of the crankshaft.Crankshaft 40 may be coupled to at least one drive wheel of a vehicle and utilize engine output torque to propel the motor vehicle. Crankshaft 40 may also be used to drive an alternator 152.

[0008] Combustion chambers 30 may receive intake air from intake manifold 44 and expel combustion gases to an exhaust passage 48 via an exhaust manifold 46. Intake manifold 44 and exhaust manifold 46 may selectively communicate with combustion chamber 30 via respective intake valves and exhaust valves (not shown). In some embodiments, combustion chamber 30 may include two or more intake valves and / or two or more exhaust valves.

[0009] Fuel injectors 50 are shown coupled directly to combustion chamber 30 for injecting fuel directly therein in proportion to the pulse width signal FPW received from controller 12. In this manner, fuel injector 50 provides what is known as direct injection of fuel into combustion chamber 30; however, it should be understood that port injection is also possible. Fuel may be delivered to fuel injector 50 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail.

[0010] In a process referred to as ignition, the injected fuel is ignited by known ignition means, such as spark plug 52, resulting in combustion. Spark timing can be controlled so that the spark occurs before (advance) or after (retard) the manufacturer-specified timing. For example, the spark timing can be retarded from a maximum break torque (MBT) timing to control engine knock or advanced under high humidity conditions. In particular, the MBT can be advanced to account for the slow combustion rate. In one example, the spark can be retarded during acceleration.

[0011] The intake manifold 44 may receive intake air from an intake passage 42. The intake passage 42 includes a throttle valve 21 with a throttle plate 22 for regulating airflow to the intake manifold 44. In this particular example, the position (TP) of the throttle plate 22 may be changed by the controller 12 to enable electronic throttle control (ETC). In this way, the throttle valve 21 may be actuated to vary the intake air supplied to the combustion chambers 30. For example, the controller 12 may adjust the throttle plate 22 to increase an opening of the throttle valve 21. Increasing the opening of the throttle valve 21 may increase the amount of air supplied to the intake manifold 44. In an alternative example, the opening of the throttle valve 21 may be reduced or completely closed to block airflow to the intake manifold 44.In some embodiments, additional throttle valves may be present in the intake passage 42, such as a throttle valve upstream of a compressor 60 (not shown).

[0012] Further, in the disclosed embodiments, an exhaust gas recirculation (EGR) system may direct a desired portion of exhaust gas from exhaust passage 48 to intake passage 42 via an EGR passage, such as high-pressure EGR passage 140. The amount of EGR supplied to intake passage 42 may be varied by controller 12 via an EGR valve, such as high-pressure EGR valve 142. Under some conditions, the EGR system may be used to regulate the temperature of the air and fuel mixture within the combustion chamber. Fig. 1 illustrates a high pressure EGR system wherein EGR is routed from upstream of a turbine of a turbocharger via the EGR passage 140 downstream of a compressor of a turbocharger. Fig. 1 also illustrates a low-pressure EGR system, where EGR is routed from downstream of a turbocharger turbine via EGR passage 156 upstream of a turbocharger compressor. A low-pressure EGR valve 154 may regulate the amount of EGR supplied to intake passage 42. In some embodiments, the engine may include both a high-pressure EGR and a low-pressure EGR system, as shown in Fig. 1. In other embodiments, the engine may include either a low-pressure EGR system or a high-pressure EGR system. When deployed, the EGR system may cause condensate to form from the compressed air, particularly when the compressed air is cooled by the charge air cooler, as described in more detail below.

[0013] The engine 10 may further include a compression device, such as a turbocharger or a positive displacement supercharger, including at least one compressor 60 disposed along the intake passage 42. For a turbocharger, the compressor 60 may be at least partially driven by a turbine 62, for example, via a shaft or other coupling arrangement. The turbine 62 may be disposed along the exhaust passage 48. Various arrangements for driving the compressor may be provided. For a positive displacement supercharger, the compressor 60 may be at least partially driven by the engine and / or an electric machine and need not include a turbine. Accordingly, the degree of compression provided to one or more cylinders of the engine via a turbocharger or a positive displacement supercharger may be varied by the controller 12.

[0014] In the Fig. 1, the compressor 60 may be primarily driven by the turbine 62. The turbine 62 may be driven by exhaust gases flowing through the exhaust passage 48. Thus, the driving motion of the turbine 62 may drive the compressor 60. Accordingly, the speed of the compressor 60 may be based on the speed of the turbine 62. As the speed of the compressor 60 increases, more boost may be delivered to the intake manifold 44 through the intake passage 42.

[0015] Further, the exhaust passage 48 may include a wastegate 26 for diverting exhaust gas away from the turbine 62. Additionally, the intake passage 42 may include a compressor bypass or recirculation valve (CVR) 27 configured to divert intake air around the compressor 60. The wastegate 26 and / or the CVR 27 may be controlled by the controller 12 to open when, for example, a lower boost pressure is desired. For example, in response to compressor surge or a potential compressor surge event, the controller 12 may open the CVR 27 to lower the pressure at the outlet of the compressor 60. This may reduce or stop compressor surge. In some embodiments, the CRV 27 may be a two-position valve that is adjustable between a closed and an open position.In other embodiments, the CRV 27 may be a multi-position valve that can be positioned in a plurality of positions between fully open and fully closed. Accordingly, the CRV 27 may be adapted to vary airflow around the compressor 60 and regulate intake pressure, as discussed in more detail below.

[0016] The intake passage 42 may further include a charge air cooler (CAC) 80 (e.g., an intercooler) to reduce the temperature of the turbocharged or boosted intake gases. In some embodiments, the CAC 80 may be an air-to-air heat exchanger. In other embodiments, the CAC 80 may be an air-to-liquid heat exchanger. The CAC 80 may also be a variable volume CAC. Hot charge air (pre-compressed air) enters the inlet of the CAC 80 from the compressor 60, cools as it passes through the CAC, and then exits to flow through the throttle body 21 and then into the engine intake manifold 44. Ambient airflow from outside the vehicle may enter the engine 10 through a vehicle front end and flow over the CAC to assist in cooling the charge air.Condensate can form and accumulate in the CAC when the ambient air temperature decreases or during humid or rainy weather conditions, cooling the charge air to a temperature below the dew point of water. Furthermore, if the charge air entering the CAC is pre-compressed (e.g., boost pressure and / or CAC pressure are higher than atmospheric pressure), condensate can form when the CAC temperature drops below the dew point temperature. If the charge air includes recirculated exhaust gases, the condensate can become acidic and corrode the CAC housing. The corrosion can lead to leaks between the air charge, the ambient environment, and, in the case of water-to-air coolers, possibly the coolant. Furthermore, if condensate forms in the CAC, it can be drawn into the engine during increased airflow. Consequently, unstable combustion and / or engine misfires can occur.

[0017] An intake pressure may be measured at the outlet of the CAC before the throttle valve 21. Accordingly, the intake pressure may be referred to as pre-throttle pressure. In one example, the intake pressure may be determined using a sensor, such as sensor 124. A relationship between the intake pressure and atmospheric pressure may be referred to as an intake pressure ratio. A ratio between a CAC pressure (which may be the intake pressure or an intermediate CAC pressure) may be referred to as a CAC pressure ratio. If the CAC pressure ratio and / or the intake pressure ratio are higher than 1, the intake pressure is higher than atmospheric pressure, and the engine is operating under boost conditions. Therefore, if the intake pressure ratio is higher than 1, condensate may form in the CAC. However, if the intake pressure ratio is maintained at or below 1, condensate may not form.In this way, reducing the suction pressure ratio from above 1 to 1 or below can reduce condensate formation in the CAC.

[0018] The intake pressure ratio may be reduced by reducing boost. In one example, opening the wastegate 26 may reduce boost. For example, the controller 12 may open the wastegate 26, thereby causing exhaust gas to bypass the turbine 62. This, in turn, reduces the speed of the turbine and subsequently the speed of the compressor 60. Reducing the speed of the compressor 60 results in less boost, thereby reducing boost pressure, CAC pressure, and intake pressure. In one example, opening the CRV 27 may reduce boost. For example, the controller 12 may open the CVR 27, thereby causing intake air to be recirculated around the compressor. This may cause boost pressure to drop to atmospheric pressure. Consequently, the CAC pressure and intake pressure may be reduced, and the resulting intake pressure ratio may be substantially equal to 1.

[0019] Although opening either the CRV 27 or the wastegate 26 can reduce boost under certain conditions, opening the wastegate 26 can result in turbo lag. For example, the controller may open the wastegate 26 to reduce boost pressure and thereby reduce turbine and compressor speed. If the controller receives a request to increase torque while the wastegate 26 is opening, the compressor may be rotating too slowly to promptly deliver the required boost pressure to meet the torque demand. The time required to close the wastegate 26 and increase the compressor speed to provide the required boost can be referred to as turbo lag. As a result of turbo lag, there may be a delay in the output of engine torque.Therefore, the controller may only open the wastegate 26 to reduce intake pressure when the engine is under steady-state conditions. In one example, steady-state conditions may include the engine running with automatic cruise control and / or a relatively constant pedal position. Accordingly, torque demand may not increase. When the engine is not running at a steady state, the CRV 27 may be opened while the wastegate 26 remains closed. In this way, intake pressure may be reduced to reduce CAC condensate formation while also reducing the possibility of turbo lag.

[0020] Furthermore, opening the CRV 27 may not only lower the intake pressure, but also increase the temperature of the intake or charge air entering the CAC. For example, when the CRV is open, intake air may be recirculated around the compressor and recompressed by the compressor. Recompressing the intake air may increase the temperature of the intake air, thereby increasing the temperature of the charge air entering the CAC. This may help maintain the air temperature within the CAC above the dew point temperature, thereby reducing condensate formation in the CAC. In an alternative example, additionally or alternatively, a bypass duct may be positioned after the CAC such that cooled charge air is recirculated around the CAC and the compressor. In some examples, an extent of opening the CVR 27 may be adjusted to vary the airflow through the CRV 27 and the compressor.For example, the controller may adjust the position of the CRV 27 to achieve a target intake pressure and / or a target air temperature in the CAC.

[0021] In some examples, opening both the CRV 27 and the wastegate 26 may reduce intake pressure more quickly, thereby reducing condensate formation more quickly. Accordingly, under some conditions, the controller may open the CRV 27 and the wastegate 26 simultaneously to quickly reduce intake pressure and reduce condensate formation in the CAC. Opening both the CRV 27 and the wastegate 26 may be based on intake pressure, a compressor surge level, and / or a humidity level of the ambient or intake air. In this way, the CRV 27 and the wastegate 26 may be adjusted to maintain the intake pressure below the dew point for a current temperature and humidity level. Further details on methods for controlling the CVR 27 and the wastegate 26 to reduce condensate formation are provided below with reference to Fig. 2 to 4 are discussed.

[0022] The control 12 is in Fig. 1 as a microcomputer including a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 106, a random access memory 108, a retention memory 110, and a data bus. The controller 12 may receive various signals from sensors coupled to the engine 10 to perform various functions for operating the engine 10. In addition to the signals previously discussed, these signals may include the measurement of induced mass air flow from a MAF (mass air flow) sensor 120; an engine coolant temperature (ECT) from a temperature sensor 112 schematically shown at a location within the engine 10; an ignition pulse input (PIP) signal; and a timing signal.profile ignition pick-up) from a Hall-effect sensor 118 (or other type) coupled to the crankshaft 40; throttle position (TP) from a throttle position sensor, as discussed; and an absolute manifold pressure (MAP) signal from a pressure sensor 122, as discussed. An engine speed signal, RPM, may be generated by the controller 12 from the PIP signal. The manifold pressure signal, MAP, from a manifold pressure sensor may be used to provide an indication of vacuum or pressure in the intake manifold 44. It should be noted that various combinations of the aforementioned sensors may be used, such as a MAF sensor without a MAP sensor, or vice versa. During stoichiometric operation, the MAP sensor may provide an indication of engine torque.Furthermore, this sensor, along with the detected engine speed, may provide an estimate of charge (including air) introduced into the cylinder. In one example, the Hall effect sensor 118, which is also used as an engine speed sensor, may generate a predetermined number of equally spaced pulses each revolution of the crankshaft 40.

[0023] Other sensors that may send signals to the controller 12 include a temperature and / or pressure sensor 124 at an outlet of a charge air cooler 80 and a boost pressure sensor 126. Other sensors, not shown, may also be present, such as a sensor for determining intake air velocity at the inlet of the charge air cooler, a sensor for determining intake air humidity, and other sensors. In some examples, the storage medium read-only memory chip 106 may be programmed with computer-readable data representing instructions executable by a microprocessor unit 102 for performing the methods described below, as well as other variants anticipated but not specifically listed. Example routines are described herein at Fig. 2 to 3.

[0024] The system of Fig. 1 provides an engine system comprising an engine having an intake manifold, a throttle valve positioned upstream of the intake manifold, a turbocharger having a turbine operable to drive a compressor, a compressor recirculation valve operable to redirect intake air around the compressor, an intercooler positioned upstream of the throttle valve and downstream of the compressor, a wastegate operable to redirect exhaust gas around the turbine, and a controller having computer-readable instructions for opening the wastegate in response to an intake pressure measured downstream of the intercooler and upstream of the throttle valve being higher than a first threshold pressure under driving conditions when the intake pressure is higher than required to maintain an intake manifold pressure (e.g.,MAP) required for a torque demand and the engine is at a steady state. Further, in addition to opening the wastegate, the controller may open the compressor recirculation valve in response to one or more of the intake pressure being higher than a second threshold pressure, where the second threshold pressure is higher than the first threshold pressure, and / or a compressor surge condition. The controller may open the compressor recirculation valve while maintaining the wastegate closed in response to the intake pressure being higher than the first threshold pressure during driving conditions when the intake pressure is higher than required to produce an intake manifold pressure (e.g., MAP) required for a torque demand and the engine is not at a steady state.

[0025] Now with reference to Fig. 2, a method 200 for adjusting a wastegate and / or a compressor recirculation valve (CRV) to reduce condensate formation in a CAC based on engine operating conditions is set forth. In one example, the method 200 may be implemented by the Fig. 1. Specifically, the controller may determine a position of the wastegate and / or the CRV (such as the wastegate 26 and the CRV 27 shown in Fig. 1) based on condensate formation conditions in the CAC, a torque demand, and additional engine operating conditions. The base position of the wastegate and the CRV may be closed. As further described below in method 200, the controller may fully open and fully close the CRV and the wastegate. In an alternative embodiment, the controller may position the wastegate and / or the CRV in a plurality of positions between fully open and fully closed.

[0026] The method begins at 202 by estimating and / or measuring engine operating conditions. Engine operating conditions may include engine speed and load, boost pressure, intake pressure, pedal position, mass air flow, MAP, EGR flow, humidity, engine temperature, torque demand, charge air cooler conditions (inlet temperature, outlet temperature, inlet pressure, outlet pressure, flow rate through the cooler, etc.). At 204, the method includes determining if condensate formation conditions exist in the CAC. In one example, condensate formation conditions include when the intake pressure (e.g., the pressure at the outlet of the CAC upstream of the throttle) is higher than a threshold pressure, which may be a first threshold pressure. In one example, the threshold pressure may be atmospheric pressure. In another example, the threshold pressure may be a pressure higher than atmospheric pressure.Alternatively or additionally, the controller may determine the intake pressure ratio as the ratio between the intake pressure and the atmospheric pressure. Accordingly, the condensate formation conditions may include when the intake pressure ratio is higher than 1. In another example, condensate formation conditions include when a humidity is higher than a first threshold. The humidity may be either a measured or inferred humidity. For example, the humidity may be one or more of a measured ambient humidity and / or an intake air humidity. In an alternative example, the humidity may be inferred based on an on / off state or a duty cycle of a windshield wiper. The first threshold may be based on a humidity level at which condensate is likely to form in the CAC.

[0027] If condensate formation conditions are not present at 204, the method proceeds to 206 to maintain engine operating conditions. Maintaining engine operating conditions may include maintaining the wastegate and CRV in closed positions. However, if condensate formation conditions are confirmed at 204, the method proceeds to 208 to determine if intake pressure is higher than required to produce a manifold pressure (MAP) required for a torque demand. Specifically, at 208, control may compare a current and measured or inferred barometric pressure (e.g., actual MAP) to a requested MAP required by the torque demand. The MAP required for a torque demand may be determined based on pedal position. For example, a pedal position input may indicate an amount of boost air required to produce the requested torque.The amount of charge air may then be used to determine the required MAP. For example, if the torque demand increases, as indicated by an increase in pedal position, an increased MAP may be required to produce the requested torque. Accordingly, the MAP may increase as the torque demand increases. An increase in the requested MAP may also result in an increase in the required boost if the pressure required to produce the torque demand is higher than atmospheric pressure. Therefore, at 208, control may determine whether boost is required to produce the required MAP and subsequently the requested torque. In one example, the intake pressure may be higher than required to produce the MAP for a torque demand when the accelerator pedal is partially depressed (e.g.,the pedal position is greater than 0 but less than a wide open pedal) and the MAP is lower than atmospheric pressure.

[0028] Returning to 208, if the intake pressure is not higher than required to produce the MAP required for the torque demand (e.g., an increase in MAP and boost is required), the controller maintains operation of the CRV and wastegate at 210. Maintaining operation of the CRV and wastegate may include keeping the CRV and wastegate closed even when condensate formation conditions are present. Additionally, at 210, the method may include adjusting alternative parameters to reduce CAC condensate formation. Alternative parameters may include closing vehicle grille shutters, decreasing a speed of one or more engine fans, decreasing a speed of a CAC coolant pump, increasing airflow into the intake manifold to remove condensate from the CAC, etc.

[0029] Otherwise, at 208, if the intake pressure is higher than required to produce the required MAP for the torque demand, the method proceeds to 212 to determine if the engine is running at steady-state conditions. In one example, steady-state conditions include the engine running under automatic cruise control. In another example, steady-state conditions include a relatively constant pedal position. For example, the relatively constant pedal position may result in a vehicle speed within 3.22 km / h (2 mph) of an average vehicle speed. In another example, a relatively constant pedal position may be indicated by a change in pedal position of less than 5% over a period of time.Additionally, steady-state conditions may include the pedal position being greater than zero, indicating that the accelerator pedal is at least partially depressed. The steady-state conditions listed above may indicate that a sudden increase in pedal position, and therefore an increase in torque demand, may not be expected. Accordingly, the risk of turbo lag may be reduced if the wastegate is opened during steady-state conditions.

[0030] Returning to 212, if the engine is not running at a steady state, the method proceeds to 214 to open the CRV to lower intake pressure and reduce CAC condensate formation. A method for controlling the CRV while lowering intake pressure is described at Fig. 4. Opening the CRV instead of the wastegate can reduce turbo lag when the controller receives a request to increase torque, which requires increased boost while lowering intake pressure.

[0031] Otherwise, if the engine is in a steady state at 212, the method proceeds to 216 to open the wastegate to lower intake pressure and reduce CAC condensate formation. A method for controlling the wastegate while lowering intake pressure is described at Fig. 3. The method may also include opening the CRV to decrease intake pressure at 216. In some examples, control may only open the CRV to decrease intake pressure. In these embodiments, method 200 may proceed from 208 directly to 214. While this may reduce the risk of turbo lag, intake pressure may decrease more slowly with the wastegate remaining closed.

[0032] In this way, a wastegate and / or a CRV may be adjusted in response to CAC condensate formation conditions when intake pressure is higher than required to produce manifold pressure required for a torque demand. Methods for adjusting the wastegate and / or the CRV may be performed by an engine controller. In one example, the controller may only adjust a wastegate in response to CAC condensate formation conditions when intake pressure is higher than required to produce manifold pressure required for a torque demand. In another example, the controller may only adjust the CRV in response to CAC condensate formation conditions when intake pressure is higher than required to produce manifold pressure required for the torque demand.In yet another example, the controller may adjust both the CRV and the wastegate in response to CAC condensate formation conditions when intake pressure is higher than required to generate the manifold pressure required for the torque demand. Condensate formation conditions may include one or more of intake pressure higher than atmospheric pressure, an intake pressure ratio greater than 1, and / or humidity higher than a first threshold. Further, intake pressure between the compressor and the throttle may be measured.

[0033] Specifically, the controller may adjust the wastegate in response to CAC condensate formation conditions when intake pressure is higher than required to produce the manifold pressure required for the torque demand and the engine is under steady-state conditions. Steady-state conditions may include one or more of operation at automatic cruise control and a constant pedal position. Further, in addition to opening the wastegate, the controller may open the CRV in response to one or more of intake pressure being higher than a threshold pressure, where the threshold pressure is a threshold amount higher than atmospheric pressure, humidity being higher than a second threshold, where the second threshold is higher than the first threshold, and a compressor surge condition.After opening the wastegate to decrease intake pressure, the controller may close the wastegate in response to one or more of intake pressure decreasing to or below atmospheric pressure (or a pressure capable of maintaining the CAC temperature above the dew point at an intake temperature) and / or an increase in torque demand. In another example, the controller may keep the wastegate closed and open the compressor recirculation valve in response to condensate buildup conditions in the charge air cooler when the intake pressure is higher than required and the engine is not at steady state conditions. In yet another example, the controller may keep both the wastegate and the compressor recirculation valve closed in response to condensate buildup conditions in the charge air cooler when the intake pressure is not higher than required to produce the manifold pressure required for the torque demand.

[0034] Fig. 3 illustrates a method 300 for adjusting a wastegate to lower a suction pressure and subsequently reduce condensate formation in a CAC. Method 300 continues at 216 into method 200. The method begins at 302 by determining a severity of condensate formation conditions at the CAC and / or whether compressor surge conditions are present. Specifically, at 302, the method determines whether condensate formation conditions are greater than a threshold.

[0035] Condensation formation conditions that are higher than a threshold (intake pressure and temperature below the dew point condition) may include the intake pressure being higher than a second threshold pressure. The second threshold pressure may be a threshold amount higher than the first threshold pressure or atmospheric pressure. As the intake pressure increases, the possibility of condensation formation in the CAC may also increase. Further, condensation formation conditions that are higher than a threshold may include the intake pressure and intake air temperature being below the dew point conditions (e.g., the conditions at which condensate may form). Additionally or alternatively, condensation formation conditions that are higher than a threshold may include the humidity being higher than a second threshold, where the second threshold is higher than the first threshold (as at 204 in Fig. 2). Determining at 302 whether surge conditions exist may include determining whether the intake pressure is higher than a surge threshold and / or determining whether to degas. In some embodiments, the presence of potential surge conditions may cause the controller to open the CRV to reduce or avoid compressor surge.

[0036] If none of the conditions are met at 302, the method proceeds to 304 to open the wastegate to lower the intake pressure to atmospheric pressure (e.g., ATM). Accordingly, the intake pressure ratio may drop to 1. At 306, control determines whether the torque demand is increasing and / or whether the intake pressure ratio is substantially equal to or below 1 (e.g., the intake pressure is at or below atmospheric pressure). If the torque demand is not increasing (e.g., the engine remains at a steady state) and the intake pressure ratio remains above 1, the wastegate remains open and the method returns to 306. However, if one or more of the conditions are met at 306, the method proceeds to 308 to close the wastegate and stop lowering the intake pressure.

[0037] Returning to 302, if one or more of the conditions at 302 are met, the method proceeds to 310 to open both the wastegate and the CRV to reduce intake pressure to atmospheric pressure (e.g., ATM). Opening the wastegate and the CRV together may reduce intake pressure and intake pressure ratio more quickly than opening either the wastegate or the CRV alone. Further, opening the CRV may increase the temperature of the charge air (e.g., intake air), thereby reducing condensate formation in the CAC. At 312, the method includes determining whether torque demand is increasing and / or whether the intake pressure ratio is substantially equal to or below 1 (e.g., intake pressure is at or below atmospheric pressure). If the torque demand does not increase (e.g., the engine remains at a steady state) and the intake pressure ratio remains above 1, the wastegate remains open and the method returns to 312.However, if one or more of the conditions are met at 312, the method proceeds to 314 to close the wastegate. This allows control to close the wastegate to reduce turbo lag while keeping the CRV open to continue lowering intake pressure.

[0038] At 316, control determines whether a requested MAP is higher than a pressure available to produce the requested MAP and / or whether the intake pressure ratio is substantially equal to or below 1 (e.g., the intake pressure is at or below atmospheric pressure). The pressure available to produce the requested MAP may be the intake pressure. The requested MAP may be based on a torque demand or request. Accordingly, if the requested MAP is higher than the intake pressure, and the throttle and other engine actuators are already adjusted to increase torque, an increase in boost may be required. For example, if the engine requires increased pressure to produce the required torque, boost may be required to increase intake pressure and deliver a greater amount of pressure to the intake manifold.Therefore, at 316, the method may include determining whether charging is required.

[0039] If the requested MAP is not higher than the intake pressure and the intake pressure ratio remains above 1, the CRV remains open at 318, and the method returns to 316. However, if one or more of the conditions are met at 316, the method proceeds to 320 to close the CRV. In an alternative embodiment, the CRV may remain open until the requested MAP is higher than the intake pressure, even if the intake pressure ratio is substantially equal to 1. Accordingly, the method may only include determining whether the requested MAP is higher than the current MAP at 316. In this way, the intake pressure may remain low until increased boost is required, thereby decreasing the likelihood of condensate formation in the CAC.

[0040] In this way, a wastegate may be opened in response to intake pressure higher than a first threshold pressure to decrease intake pressure during driving conditions when the intake pressure is higher than required to generate manifold pressure necessary for a torque demand and the engine is at a steady state. The wastegate may also be opened in response to humidity higher than a first threshold during driving conditions when the intake pressure is higher than required to generate manifold pressure necessary for the torque demand and the engine is at a steady state.Further, a compressor recirculation valve may be opened in response to one or more of the intake pressure being higher than a second threshold pressure, where the second threshold pressure is higher than the first threshold pressure, humidity being higher than a second threshold, where the second threshold is higher than the first threshold, and / or a compressor surge condition. After opening the compressor recirculation valve and the wastegate, the wastegate may be closed in response to one or more of the increasing torque demand and / or the intake pressure decreasing to or below the threshold (e.g., decreasing the intake pressure ratio to 1), and then the compressor recirculation valve may be closed in response to one or more of a required intake pressure for the torque demand being higher than the intake pressure and / or the intake pressure decreasing to or below the threshold pressure.

[0041] After opening the wastegate to decrease intake pressure, the wastegate may be closed in response to one or more of the intake pressure decreasing to or below the threshold pressure and an increase in torque demand. Further, the compressor recirculation valve may be opened and the wastegate may be kept closed when the engine is not at a steady state. Accordingly, intake pressure may be decreased by opening the compressor recirculation valve while simultaneously reducing turbo lag. In one example, the first threshold pressure is based on a pressure at which condensate forms in the charge air cooler. In another example, the first threshold pressure is atmospheric pressure.

[0042] Fig. 4 illustrates a method 400 for adjusting the CRV to lower intake pressure and subsequently reduce condensate formation in a CAC. Method 400 continues at 214 into method 200. The method begins at 402 by opening the compressor recirculation valve when the required intake pressure for the torque demand is higher than the intake pressure. At 404, the method includes determining if a requested MAP is higher than the current intake pressure. As previously mentioned, the requested MAP may be based on the torque demand. An increase in torque demand may be indicated by an increase in pedal position. If the requested MAP is higher than the current intake pressure, an increase in intake pressure may be required to produce the requested MAP. The intake pressure may be increased by operating the compressor and producing boost.If the requested MAP is higher than the current intake pressure and boost is required, the method proceeds to 406 to close the CRV. Closing the CRV may allow the compressor to deliver increased boost to the intake manifold as required by torque demand.

[0043] However, if the requested MAP is not higher than the intake pressure at 404 and no boost is required, the method proceeds to 408 to determine if the intake pressure ratio is substantially equal to or below 1 (e.g., the intake pressure is below or equal to atmospheric or threshold pressure, or below the dew point at the given intake temperature). If the intake pressure ratio is substantially equal to or below 1, control closes the CRV at 406. In an alternative embodiment, control may keep the CVR open until the requested MAP increases above the current MAP, even if the intake pressure ratio drops to 1. If at 408 the intake pressure ratio is still above 1, control keeps the CRV open at 410, and the method returns to 404.

[0044] In this way, an engine controller may open a compressor recirculation valve in response to condensate formation conditions in the charge air cooler during driving conditions when a pre-throttle pressure is higher than required to produce the required MAP for a torque demand. In one example, the condensate formation conditions include one or more of an intake pressure higher than atmospheric pressure and a humidity higher than a first threshold. The humidity may be one or more of a measured humidity and an inferred humidity of intake air. In one example, after opening the compressor recirculation valve to decrease intake pressure, the controller may close the compressor recirculation valve in response to a demanded manifold pressure increasing above intake pressure.In another example, after opening the compressor recirculation valve to decrease intake pressure, the controller may close the compressor recirculation valve in response to an intake pressure decrease to atmospheric pressure. Further, the controller may open a wastegate in response to condensate formation conditions in the charge air cooler during driving conditions when the intake pressure is higher than required to create manifold pressure necessary for a torque demand and the engine is at a steady state. Opening the wastegate may assist in decreasing intake pressure, thereby reducing intake pressure at a faster rate. The controller may then close the wastegate in response to one or more of an increase in torque demand and an intake pressure decrease to atmospheric pressure.Further, the controller may keep the compressor recirculation valve closed and adjust alternative engine operating parameters when intake pressure is not higher than necessary to produce the manifold pressure required for the torque demand. In one example, adjusting alternative engine operating conditions may include adjusting a vehicle grille shutter system, adjusting a speed of one or more engine fans, and / or adjusting airflow to an intake manifold. In another example, the controller may open the compressor recirculation valve in response to compressor surge conditions.

[0045] Fig. 5 illustrates a graphical example of wastegate and compressor recirculation valve (CRV) adjustments based on engine operating conditions. Specifically, graph 500 illustrates changes in pedal position (PP) at plot 502, changes in torque demand at plot 504, changes in requested MAP at plot 508, changes in intake pressure at plot 512, changes in humidity at plot 516, changes in CRV position at plot 518, and changes in wastegate position at plot 520. The intake pressure may be an estimated or measured pressure at an outlet of a CAC upstream of an intake throttle. At plot 512, the intake pressure is compared to a threshold pressure for condensate formation in the CAC. In this example, the threshold pressure is atmospheric pressure 510.Accordingly, an intake pressure ratio may be higher than one, and condensate may form in the CAC if the intake pressure is above atmospheric pressure 510. As previously mentioned, the humidity may be a measured or inferred humidity of the intake air. Furthermore, graph 500 represents the adjustment of the CRV and the wastegate between an open and a closed position. In an alternative embodiment, the controller may position the wastegate and / or the CRV in a plurality of positions between fully open and fully closed.

[0046] Before time t1, the pedal position (plot 502), the torque demand (plot 504), and the requested MAP (plot 508) may be at relatively constant levels. The CRV and wastegate are both closed (plots 518 and 520). The intake pressure is near the requested MAP, but the intake pressure and humidity remain at or below their respective thresholds for indicating condensate formation conditions (plots 512 and 516). At time t1, the intake pressure increases to above atmospheric pressure 510 (plot 512) while remaining higher than the requested MAP (plots 512 and 508). At time t1, the pedal position is also relatively constant, indicating that the engine is at a steady state. In response to the intake pressure increasing above atmospheric pressure 510 under the previously mentioned driving conditions, a controller opens the wastegate to lower the intake pressure (graph 520).At time t1, the CRV remains closed because the condensate formation conditions are not above a threshold (e.g., the intake pressure is not above a second threshold pressure). However, in alternative embodiments, the CRV may also open at time t1 to increase the rate at which the intake pressure decreases. In another embodiment, the CRV may open at time t1 instead of opening the wastegate, and accordingly, the wastegate may remain closed.

[0047] At time t2, the intake pressure drops to atmospheric pressure 510. In response, the controller closes the wastegate (plot 520). At time t3, the humidity increases above a threshold 514, thereby indicating the presence of condensate formation conditions at the CAC (plot 516). At time t3, the pedal position also increases (plot 502), and the intake pressure is higher than required to produce the requested MAP for the torque demand. Thus, at time t3, when the intake pressure is higher than required for the torque demand and the engine is not at a steady state, the controller opens the CRV in response to the humidity increase above threshold 514. At time t4, the pedal position increases (plot 502), thereby increasing the torque demand (plot 504). Consequently, the requested MAP increases above the intake pressure at time t5.In response, the controller closes the CRV to increase the boost supplied to the engine.

[0048] After closing the CRV, intake pressure continues to rise above atmospheric pressure 510. However, since the requested MAP is still higher than intake pressure, the wastegate and CRV remain closed. Between time t5 and time t6, the pedal position settles, and the engine operates under steady-state conditions. At time t6, intake pressure increases above the requested MAP (plots 512 and 508). At this time, the intake pressure may be a threshold amount 522 above atmospheric pressure 510 (e.g., the intake pressure is higher than a second threshold pressure). Consequently, at time t6, control opens both the CRV and the wastegate. Just before time t7, the pedal position increases (plot 502). The increase in pedal position causes the torque demand to begin increasing at time t7.In response to the increase in torque demand, the controller closes the wastegate; however, the CRV remains open. Holding the CRV open longer allows intake pressure to continue decreasing while reducing turbo lag. At time t8, the requested MAP rises above intake pressure. Consequently, the controller closes the CRV (plot 518).

[0049] As at time t1 and t6 in Fig. 5, in a first condition, the controller may open a wastegate in response to one or more of a suction pressure greater than a first threshold pressure and humidity greater than a threshold. The first condition includes when a suction pressure is higher than required based on a torque demand and the engine is at a steady state. Further, the controller may open the CRV in response to one or more of a compressor surge condition and the suction pressure greater than a second threshold pressure (as shown at time t6), where the second threshold pressure is higher than the first threshold pressure.

[0050] As shown at time t3, in a second condition, the controller may open the CRV in response to humidity higher than a threshold (e.g., the humidity level in Fig. 5). In another example, in the second condition, control may open the CRV in response to the intake pressure being higher than a first threshold pressure. As shown in Fig. 5, the first threshold pressure is atmospheric pressure. The second condition includes when the intake pressure is higher than required based on a torque demand and the engine is not in a steady state. In another embodiment, the second condition may include when the intake pressure is higher than required based on a torque demand. In this embodiment, the CRV may open at time t1 instead of, or in addition to, opening the wastegate.

[0051] As shown at time t5, under a third condition, the controller keeps the CRV and wastegate closed. The third condition includes when the intake pressure is at or below the requested level, where the requested level is based on the torque demand. At time t5, the wastegate and CRV remain closed even if the intake pressure is higher than atmospheric pressure.

[0052] In this way, opening one or more of a compressor recirculation valve (CRV) and / or a wastegate in response to condensate formation conditions in a charge air cooler (CAC) may lower a suction pressure to thereby reduce the possibility of condensate formation in the CAC. In one example, condensate formation conditions may include the suction pressure being higher than a threshold pressure. The threshold pressure may be atmospheric pressure. Similarly, condensate formation conditions may also be determined from a suction pressure ratio higher than 1, where the suction pressure ratio is a ratio between the suction pressure and atmospheric pressure. In another example, condensate formation conditions include humidity higher than a threshold for condensation formation.

[0053] Specifically, control may open the wastegate and / or the CRV in response to one or more of the condensate formation conditions during driving conditions when the intake pressure is higher than required to produce the manifold pressure (MAP) required for a torque demand. In one example, control may only open the wastegate when the engine is at a steady state and the condensate formation conditions are below a threshold. In another example, control may only open the CRV when the engine is not at a steady state. In yet another example, control may open both the CRV and the wastegate when the engine is at a steady state and the condensate formation conditions are higher than a threshold. The threshold condensate formation conditions may be based on intake pressure and / or humidity levels that indicate increased condensate formation.After opening one or more of the wastegate and / or the CRV, the controller can close the valves when torque demand increases and / or when intake pressure has dropped to atmospheric pressure. Adjusting the CRV and wastegate in this manner can lower intake pressure when higher manifold pressure is not required by the engine. Accordingly, condensate formation in the CAC can be reduced, thereby reducing the possibility of engine misfires and / or unstable combustion.

[0054] It should be appreciated that the example control routines included herein may be used with various engine and / or vehicle system configurations. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated acts, operations, or functions may be performed in the illustrated order, in parallel, or, in some cases, omitted. Likewise, the order of processing is not required to achieve the features and advantages of the example embodiments described herein, but is provided merely for ease of illustration and description.One or more of the illustrated actions or functions may be performed repeatedly depending on the specific strategy being used. Furthermore, the described actions may graphically represent code to be programmed into the computer-readable storage medium in the engine control system.

[0055] It is to be understood that the configurations and routines described herein are exemplary in nature, and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the above technology may be applied to V-6, I-4, I-6, V-12, horizontally opposed four, and other engine types. Furthermore, one or more of the various system configurations may be used in combination with one or more of the described diagnostic routines. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or characteristics disclosed herein.

Claims

[1] A method for an engine (10), comprising: Adjusting a wastegate (26) in response to condensate formation conditions in a charge air cooler (80) when an intake pressure is higher than required to produce a manifold pressure required for a torque demand. [2] The method of claim 1, further comprising opening the wastegate (26) in response to condensate formation conditions in the charge air cooler (80) when the intake pressure is higher than required and the engine (10) is under steady state conditions. [3] The method of claim 2, wherein the intake pressure is measured between a compressor (60) and a throttle valve (21), and wherein steady state conditions comprise one or more of operation at automatic cruise control and a constant pedal position. [4] The method of claim 2, wherein condensate formation conditions include one or more of suction pressure higher than atmospheric pressure and humidity higher than a first threshold. [5] The method of claim 4, further comprising, in addition to opening the wastegate (26), opening a compressor recirculation valve (27) in response to one or more of the intake pressure being higher than a threshold pressure, the threshold pressure being a threshold amount higher than atmospheric pressure, the humidity being higher than a second threshold, the second threshold being higher than the first threshold, and a compressor surge condition. [6] The method of claim 2, further comprising closing the wastegate (26) in response to one or more of an intake pressure decrease to or below atmospheric pressure and an increase in torque demand. [7] The method of claim 1, further comprising maintaining the wastegate (26) closed and opening a compressor recirculation valve (27) in response to condensate formation conditions in the charge air cooler (80) when the intake pressure is higher than required to produce the manifold pressure required for the torque demand and the engine (10) is not under steady state conditions. [8] The method of claim 1, further comprising maintaining the wastegate (26) closed in response to condensate formation conditions in the charge air cooler (80) when the intake pressure is not higher than required for the torque demand. [9] Engine process comprising: in a first condition, opening a wastegate (26) in response to one or more of an intake pressure higher than a first threshold pressure and a humidity higher than a threshold; and in a second condition, opening a compressor recirculation valve (27) in response to one or more of the suction pressure being higher than the first threshold pressure and the humidity being higher than the threshold. [10] The method of claim 9, wherein the first condition includes when the intake pressure is higher than required based on a torque demand and the engine (10) is in a steady state. [11] The method of claim 10, further comprising opening the compressor recirculation valve (27) in response to one or more of a compressor surge condition and the suction pressure being higher than a second threshold pressure, the second threshold pressure being higher than the first threshold pressure. [12] The method of claim 9, wherein the second condition includes when the intake pressure is higher than required based on a torque demand and the engine (10) is not in a steady state.

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