Procedure and boost pressure limiter

Abstract

Procedure comprising: Adjusting a wastegate actuator (150) coupled to a wastegate valve (206) in an engine outlet to control an engine boost level of an engine (10), the adjustment being based on a force provided by a preload (210), wherein a boost limiter actuation force (550) is calculated based on a pressure differential across the boost limiter, the exhaust gas flow, the closing force provided by the preload (210) and / or the angle of the boost limiter valve (206), and the boost limiter actuation force (550) is used as input to an inverse boost limiter model that maps a desired boost limiter pressure or a desired boost limiter valve position to a boost limiter duty cycle for a given boost limiter actuation force (550), wherein the duty cycle signal is generated by the control unit and sent to the boost pressure limiter actuator (150) to adjust the boost pressure limiter actuation force (550).

Description

Area

[0001] The disclosure relates to methods for controlling a turbocharger assembly of an internal combustion engine and a boost pressure limiter. Background and Summary

[0002] Engines may use a turbocharger to improve engine torque / power output density. In one example, a turbocharger may include a compressor and a turbine connected by a driveshaft, with the turbine coupled to an exhaust manifold side and the compressor coupled to an intake manifold side. In this way, the exhaust-driven turbine provides energy to the compressor to increase intake manifold pressure (e.g., boost or boost pressure) and increase the flow of air into the engine. Boosting may be controlled by adjusting the amount of gas reaching the turbine, for example, with a wastegate. The wastegate valve may be controlled based on operating conditions to achieve the desired boost.In one example, the wastegate valve may be an electronic wastegate controlled by an associated electric actuator. The electric actuator is driven to change the wastegate position, thereby controlling the amount of gas reaching the turbine and achieving the desired boost. In some downsized engines, whose volumes have been reduced to improve fuel economy, a turbocharger is included to recover the power lost due to the downsizing.

[0003] In some examples, an electric actuator is used to control the position of a wastegate valve. The electric actuator may, for example, be an electric motor that transmits a linear force to a rod. The rod may directly actuate the wastegate valve, or alternatively, the rod may be coupled to a rotary element that transmits rotary motion to the wastegate valve.

[0004] US 6 012 289 A discloses an apparatus and method for using a learned wastegate control signal to control turbocharger operation. US 7 926 270 B2 discloses a turbocharger wastegate controller.

[0005] The inventors herein have recognized a problem with such methods using electric actuators to control the position of a wastegate valve. In downsized engines, the loss of wastegate valve control due to a degraded actuator can cause insufficient boost to be delivered to the engine. In this case, the engine cannot deliver the desired level of torque and power output. Consequently, the degree of engine downsizing may be limited due to wastegate degradation concerns. For example, the loss of wastegate valve control can cause insufficient boost to be delivered to an engine, particularly when the wastegate valve is pushed to a partially open position due to exhaust flow pressure and forces.In this case, the deteriorated actuator cannot provide enough closing force to the valve.

[0006] Systems and methods for compensating for a degraded electric actuator operatively coupled to a wastegate valve are provided. For example, one method may include adjusting a wastegate actuator coupled to a wastegate valve in an engine exhaust to control an engine boost level, the adjustment based on a force provided by a preload.

[0007] In one example, a spring is coupled to an electric wastegate actuator, the spring maintaining a wastegate valve in a closed position up to a threshold pressure. During undegraded operation, the electric actuator is moved toward an open position with a first current and toward a closed position with a second current, additionally biased toward the closed position via the spring.

[0008] In this way, by coupling a spring to an electric wastegate actuator and holding a wastegate valve in a closed position up to a threshold manifold pressure via the preload spring force (e.g., spring preload), sufficient boost can be provided to an engine and a desired engine output can be ensured even if the electric actuator has degraded. Furthermore, because the closing force is supplied via the spring, the size of the electric actuator can be reduced, reducing power consumption. Downsized engines can also eliminate or reduce sizing to account for wastegate degradation.

[0009] The above advantages and other advantages and features of the present description will be readily apparent from the following detailed description taken alone or in conjunction with the accompanying drawings.

[0010] Of course, the above summary is provided to introduce, in a simplified form, a selection of concepts further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined only by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages identified above or in any part of this disclosure. Brief description of the drawings Fig. 1 shows a block diagram of a turbocharged engine with a boost pressure limiter. Fig. 2 shows an exemplary boost pressure limiter according to an embodiment of the present disclosure. Fig. 3 shows a flowchart illustrating a method for controlling a turbocharger via a boost pressure limiter. Fig. 4 shows a flowchart illustrating a method for controlling a boost pressure limiter associated with a turbocharger. Fig. 5 shows a protocol for determining a boost pressure limiter actuation force. Detailed description

[0011] In turbocharged engines, electronic wastegate actuators can provide precise output to achieve the delivery of a desired boost to the engine. Deterioration of the electric actuator, for example, due to a loss of power, can reduce the precise control of a wastegate valve and limit engine output power / torque. If the actuator deteriorates and the wastegate valve is in a partially open position, for example, adequate boost cannot be delivered to the engine, which then cannot provide the desired output power. Such a problem is particularly true for downsized engines whose dimensions are reduced to improve fuel economy.Downsized engines may incorporate a turbocharger to recover power lost due to downsizing. If an electric actuator controlling the turbocharger deteriorates, sufficient boost may not be delivered to the engine, and the engine may not provide the desired power output. Such downsized engines are consequently sized with wastegate actuator deterioration in mind, which limits the extent of downsizing and, consequently, fuel economy gains. On the other hand, if the actuator deteriorates when the wastegate valve is in a fully closed position, boost may be delivered to the engine in an amount greater than desired, resulting in lean combustion and degraded emissions.

[0012] Various systems and methods for compensating for a degraded electric wastegate actuator are provided. In one embodiment, a spring is coupled to an electric wastegate actuator, the spring maintaining a wastegate valve in a closed position up to a threshold manifold pressure. During operation, the electric actuator is moved toward an open position with a first current and toward a closed position with a second current. Fig. 1 is a block diagram of a turbocharged engine with a wastegate. Fig. 2 shows an exemplary boost pressure limiter used in the engine of Fig. 1, according to an embodiment of the present disclosure. The engine of Fig. 1 also includes a control unit configured to Fig. 3 and Fig. 4 to carry out the procedure shown. Fig. 5 shows a protocol for determining a boost pressure limiter actuation force.

[0013] Fig. 1 is a schematic diagram showing an example engine 10 that may be included in a propulsion system of a motor vehicle. The engine 10 is shown with four cylinders 30. However, other numbers of cylinders may be used according to the current disclosure. The engine 10 may be controlled at least in part by a control system including a controller 12 and by input 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) disposed therein. The pistons may be coupled to a crankshaft 40 such that reciprocating motion of the piston is translated into rotational motion of the crankshaft.The crankshaft 40 may be coupled to at least one drive wheel of a vehicle via an intermediate transmission system (not shown). Furthermore, a starter motor may be coupled to the crankshaft 40 via a flywheel to enable a starting operation of the engine 10.

[0014] Combustion chambers 30 may receive intake air from intake manifold 44 via an intake passage 42 and may exhaust combustion gases via an exhaust passage 48. 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.

[0015] Fuel injectors 50 are shown coupled directly to the combustion chamber 30 for injecting fuel directly therein in proportion to the pulse width of a signal FPW received from the controller 12. In this manner, the fuel injector 50 provides what is known as direct injection of fuel into the combustion chamber 30. The fuel injector may be mounted, for example, in the side of the combustion chamber or in the top of the combustion chamber. Fuel may be delivered to the fuel injector 50 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail. In some embodiments, the combustion chambers 30 may alternatively or additionally include a fuel injector disposed in the intake manifold 44 in a configuration that provides what is known as port injection of fuel into the intake port upstream of each combustion chamber 30.

[0016] The intake passage 42 may include throttle valves 21 and 23 with throttle plates 22 and 24, respectively. In this particular example, the position of the throttle plates 22 and 24 may be varied by the control unit 12 via signals provided to an actuator included with the throttle valves 21 and 23. In one example, the actuators may be electric actuators (e.g., electric motors), a configuration commonly referred to as electronic throttle control (ETC). In this manner, the throttle valves 21 and 23 may be actuated to vary the intake air supplied to the combustion chamber 30 among other engine cylinders. The position of the throttle plates 22 and 24 may be provided to the control unit 12 by a throttle position signal TP.The intake passage 42 may further include a mass air flow sensor 120 and a manifold air pressure sensor 122 for providing respective MAF (mass air flow) and MAP (manifold air pressure) signals to the control unit 12.

[0017] Exhaust passage 48 may receive exhaust gases from cylinders 30. An exhaust gas sensor 128 is shown coupled to exhaust passage 48 upstream of turbine 62 and an emission control device 78. Sensor 128 may be selected from various suitable sensors for providing an indication of exhaust air / fuel ratio, such as a linear oxygen sensor or UEGO (universal or wideband exhaust gas oxygen sensor), a dual-state oxygen sensor or EGO, a NOx, HC, or CO sensor. The emission control device 78 may be a three-way catalyst (TWC), a NOx trap, various other emission control devices, or combinations thereof.

[0018] The exhaust gas temperature may be measured by one or more temperature sensors (not shown) disposed in the exhaust passage 48. Alternatively, the exhaust gas temperature may be inferred based on engine operating conditions such as speed, load, air / fuel ratio (AFR), spark retard, etc.

[0019] The control unit 12 is in Fig. 1 as a microcomputer comprising a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown as a read-only memory chip 106 in this particular example, a random access memory 108, a retention memory 110, and a data bus.The control unit 12 may receive various signals from sensors coupled to the engine 10 in addition to the signals previously discussed, including the measurement of inducted mass air flow (MAF) from the mass air flow sensor 120; the engine coolant temperature (ECT) from the temperature sensor 112, which is schematically shown at a location within the engine 10; a profile ignition pickup (PIP) signal from a Hall effect sensor 118 (or other type) coupled to the crankshaft 40; a throttle position (TP) from a throttle position sensor, as discussed; and a manifold absolute pressure signal, MAP, from sensor 122, as discussed. The engine speed RPM may be generated by the control unit 12 from the PIP signal. The manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of a vacuum or pressure in the intake manifold 44.It should be noted that various combinations of the above 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. This sensor, along with the detected engine speed, may further provide an estimate of the charge (including air) being introduced into the cylinder. In one example, sensor 118, which is also used as an engine speed sensor, may generate a predetermined number of equally spaced pulses every revolution of crankshaft 40. In some examples, storage medium read-only memory 106 may be programmed with computer-readable data representing instructions executable by processor 102 to perform the methods described below, as well as other variations that are expected but not specifically listed.

[0020] The engine 10 may further include a compression device, such as a turbocharger or supercharger having at least one compressor 60 disposed along the intake manifold 44. For a turbocharger, the compressor 60 may be at least partially driven by a turbine 62 via, for example, a shaft or other coupling arrangement. The turbine 62 may be disposed along the exhaust passage 48. Various arrangements may be provided to drive the compressor. For a supercharger, the compressor 60 may be at least partially driven by the engine and / or an electric machine and may not include a turbine. Accordingly, the amount of compression delivered to one or more cylinders of the engine via a turbocharger or supercharger may be varied by the controller 12.In some cases, for example, the turbine 62 may drive an electric generator 64 to provide power to a battery 66 via a turbo driver 68. Power from the battery 66 may then be used to drive the compressor 60 via a motor 70. Further, a sensor 123 may be disposed in the intake manifold 44 to provide a BOOST signal to the control unit 12.

[0021] Further, the exhaust passage 48 may include a wastegate 26 for diverting exhaust gas away from the turbine 62. In some embodiments, the wastegate 26 may be a multi-stage wastegate, such as a two-stage wastegate with a first stage configured to control boost pressure and a second stage configured to increase heat flow to the emission control device 78. The wastegate 26 may be operated with an actuator 150, which may, for example, be an electric actuator. In some embodiments, the actuator 150 may be an electric motor. Additional detail regarding the wastegate 26 and actuator 150 is provided below. The intake passage 42 may include a compressor bypass valve 27 configured to divert intake air around the compressor 60.The wastegate 26 and / or the compressor bypass valve 27 may be controlled by the control unit 12 via actuators (e.g., actuator 150) to open when, for example, a lower boost pressure is desired. Additional details of an example wastegate used in the system of . Fig. 1 can be used are in Fig. 2 shown.

[0022] 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, charge air cooler 80 may be an air-to-air heat exchanger. In other embodiments, charge air cooler 80 may be an air-to-liquid heat exchanger.

[0023] Further, in the disclosed embodiments, an exhaust gas recirculation (EGR) system may direct a desired portion of the exhaust gas from the exhaust passage 48 to the intake passage 42 via an EGR passage 140. The amount of EGR supplied to the intake passage 42 may be varied by the control unit 12 via an EGR valve 142. Further, an EGR sensor (not shown) may be disposed within the EGR passage and may provide an indication of one or more of pressure, temperature, and concentration of the exhaust gas. Alternatively, the EGR may be controlled by a calculated value based on signals from the MAF (upstream) sensor, MAP (intake manifold), MAT (manifold gas temperature), and the crank speed sensor. Further, the EGR may be controlled based on an exhaust O 2sensor and / or an intake manifold oxygen sensor. Under some conditions, the EGR system can be used to regulate the temperature of the air and fuel mixture within the combustion chamber. Fig. 1 shows a high-pressure EGR system in which EGR is routed from upstream of a turbocharger turbine to downstream of a turbocharger compressor. In other embodiments, the engine may additionally or alternatively include a low-pressure EGR system in which EGR is routed from downstream of a turbocharger turbine to upstream of a turbocharger compressor.

[0024] If you now Fig. 2, the wastegate 26 and actuator 150 of the engine 10 are shown in more detail. The wastegate 26 is included along a portion of an exhaust manifold 202, for example, similar to the one shown in Fig. 1. In the illustrated embodiment, the wastegate 26 is an electric wastegate and is driven by the actuator 150, which in this example is a solenoid, although various suitable devices may be used to drive the wastegate. The actuator 150 transmits a drive force to a wastegate valve 206, which can transition between a fully closed position and a fully open position and can settle in any position therebetween. The wastegate 26 also includes a vent 208 that can receive and vent gas from the exhaust manifold 202 when the wastegate valve 206 is not in the fully closed position.Consequently, the amount of boost delivered to an engine may be controlled by driving the wastegate valve 206 via the actuator 150, thereby changing the position of the wastegate valve 206 and the amount of gas reaching an intake manifold. In one example, the valve 206 may be formed via a pin with a surface facing the flow through the manifold 202. The pressure differential across the pin may create forces acting to move the pin. Although not shown, the wastegate 26 may include a motor, a transmission case, and a linkage from an output shaft of the transmission to the wastegate valve 206. In some embodiments, a preload may be coupled to the output shaft, the type and physical characteristics of which may be determined by the movement of the output shaft.However, various suitable wastegate arrangements may be used without departing from the scope of the present disclosure and may depend, for example, on mechanical design and packaging constraints.

[0025] The wastegate 26 further includes a preload 210. The preload 210 is attached to the wastegate 26 at one end and to the wastegate valve 206 at the other end. In some embodiments, the preload 210 is selected to provide a closing force that maintains the wastegate valve 206 in a fully closed position up to a threshold pressure. As a non-limiting example, the preload 210 may be selected to allow the wastegate valve 206 to open for an average pressure differential across the turbocharger turbine between 0.75 bar and 1 bar.In the event of wastegate degradation, for example, due to a loss of power to actuator 150, wastegate valve 206 may be held in a fully closed position up to a threshold pressure via the spring preload, ensuring that a sufficient buildup of boost is delivered to the engine. Such a configuration may be particularly advantageous in downsized engines, as the amount of downsizing need not be limited by considering the possibility of wastegate actuator degradation. At or above the threshold pressure, however, preload 210 may allow wastegate valve 206 to move toward a fully open position, limiting maximum boost, particularly at high loads. Furthermore, the size of the wastegate actuator (e.g.,of actuator 150) and its power consumption can be reduced because preload 210 provides additional closing force to wastegate 26. Therefore, during non-degraded operation, the actuator can maintain the valve in the fully closed position with a current level lower than if the spring preload were zero. As described below with reference to FIG. Fig. 5, the current supplied to a wastegate actuator may be selected to account for the closing force of a preload, such as a spring. In the illustrated embodiment, the preload 210 is shown as a spring in a pre-compressed state, although various suitable structures may be used to provide additional closing force to the wastegate 26. In the case where a spring is used, the spring rate may be selected to provide closing force up to a certain threshold pressure and provide sufficient boost to an engine.

[0026] The wastegate 26 may provide additional benefits. Pneumatic wastegates, in some examples, provide a closing force to a wastegate valve by creating a pressure differential across a diaphragm attached to a spring. Such pneumatic wastegates are therefore limited in their supply of force to the pressure differential and the spring force. Under a normal operating condition, the wastegate 26 may instead provide higher levels of closing force via the preload 210 and its associated electric actuator (e.g., actuator 150). As such, even while the wastegate is held fully closed, the actuator current may be adjusted in response to engine operating conditions (e.g.,to increase the exhaust manifold pressure, or vice versa) to maintain the fully closed position in combination with the spring preload force, where the spring preload force is non-zero.

[0027] If you now Fig. Turning to FIG. 3, a method 301 is performed according to the invention by an engine control unit (control unit 12) for controlling a turbocharger via a wastegate (e.g., wastegate 26). In one example, a method for controlling an engine turbocharger via a wastegate may include determining a desired boost pressure and an actual boost pressure. The operating condition of a wastegate actuator (e.g., actuator 150) may then be determined, and the wastegate actuator may be actuated accordingly.

[0028] In continuation with Fig. 3, the method includes, at 310, determining a desired boost according to engine operating conditions. The evaluated conditions may be measured directly with sensors, such as sensors 112, 118, 120, 122, 123, and 134, and / or the conditions may be estimated from other engine operating conditions. The evaluated conditions may include engine coolant temperature, engine oil temperature, mass air flow (MAF), manifold pressure (MAP), boost (e.g., BOOST from sensor 123), engine speed, idle speed, barometric pressure, driver-requested torque (e.g., from pedal position sensor 134), air temperature, vehicle speed, etc.

[0029] Next, at 320, an actual boost may be determined. The actual boost may be measured directly by a sensor, such as sensor 123. The measurement may be sent to controller 12 via the BOOST signal and stored in a computer-readable storage medium. In an alternative embodiment, the actual boost may be estimated based on other operating parameters, such as MAP and RPM.

[0030] Next, at 330, barometric pressure may be determined. For example, barometric pressure may be measured by the MAP sensor at engine start-up and / or estimated based on engine operating conditions, including MAF, MAP, throttle position, etc. The measurement may be sent to controller 12 and stored in a computer-readable storage medium. In an alternative embodiment, atmospheric pressure may be estimated based on other operating parameters.

[0031] Next, at 340, the operating condition of a wastegate actuator may be determined. For example, the wastegate actuator may be the Fig. 1. The actuator is actuated based on the determined operating condition, which may be either a normal operating condition or a degraded operating condition.

[0032] As described above, a boost pressure limiter (e.g. boost pressure limiter 26 in Fig. 1) be actuated by an actuator (e.g. actuator 150). Fig. 4 is shown to provide additional details of the acts performed at 340. Method 401 may be performed, for example, by an engine control unit (e.g., control unit 12). Specifically, method 401 determines the operating condition of the wastegate actuator and actuates the wastegate actuator based on the determined operating condition. Although method 401 is shown as being performed after method 301, it should be understood that method 401 may be performed before method 301 without departing from the scope of this disclosure.

[0033] At 410 of method 401, it is determined whether or not the operating condition of the wastegate actuator has deteriorated. Various suitable methods may be used to evaluate the operating condition of the wastegate actuator and may include monitoring the power drawn by the actuator. For example, a position of the actuator may be compared to a desired position to determine whether the wastegate valve is being controlled as requested. Further, current or voltage monitoring may be used. If it is determined that the operating condition of the actuator has deteriorated, method 401 proceeds to 412.

[0034] At 412 of method 401, a degraded mode of operation is employed. A wastegate preload (e.g., preload 210) may be relied upon to provide a closing force to a wastegate valve (e.g., wastegate valve 206) up to a threshold pressure, as described above, particularly with reference to Fig. 2, without any adjustment of actuator current in response to operating conditions. Method 401 may take further optional action at 412, including indicating to a vehicle driver that the wastegate operating condition has deteriorated, for example, via an instrument panel indicator and / or setting a diagnostic code. At 412, method 402 may also take actions via controller 12 to limit engine load, which may include moving various throttle bodies toward closed positions in response to engine airflow being greater than a threshold limit, as well as reducing fuel injection to lean combustion in the engine cylinders.

[0035] If method 401 determines at 410 that wastegate actuator operation has not degraded, method 401 proceeds to 414.

[0036] At 414 of method 401, the wastegate actuation force is calculated according to the invention based on a pressure differential across the wastegate, the exhaust flow, the closing force provided by the preload 210, and / or the angle of the wastegate valve. The wastegate may be adjusted according to the wastegate actuation force. The wastegate actuation force may closely resemble a pressure differential across the wastegate. The wastegate actuation force is used according to the invention as input to an inverse wastegate model.According to the invention, the inverse wastegate model maps a desired wastegate pressure or wastegate valve position to a wastegate duty cycle for a given wastegate actuation force, wherein the duty cycle signal is generated by the controller and sent to the wastegate actuator to adjust the actuation force. Mapping to a wastegate duty cycle may include using lookup tables or calculating the wastegate duty cycle. A wastegate control (WGC) signal may include pulse width modulation over the wastegate duty cycle to adjust the wastegate. The desired wastegate pressure or wastegate valve position may be determined, for example, from feedforward, feedback, or other control algorithms.

[0037] The wastegate actuation force can also affect wastegate dynamics. A compensation term can account for wastegate actuator delays, as described herein with respect to the controller, where zeros cancel poles of the wastegate actuator model. Additionally, the compensation term can further include adjustments based on the movement of dual independent cams, which can affect boost pressure. For example, if the intake cam is moved in a manner that would increase boost pressure relative to barometric pressure, the magnitude of the compensation term can be decreased. Likewise, if the intake cam is moved in a manner that would decrease boost pressure relative to barometric pressure, the magnitude of the compensation term can be increased.

[0038] At 414, determining a wastegate actuation force also includes determining the position of the actuator (e.g., actuator 150). A measurement is first taken, which depends on the particular type of actuator used. In one example, a sensor is provided and used to measure the linear displacement of a rod actuated by the actuator. Alternatively, the actuator may include a motor, which in turn may include a rotary encoder housed within the motor. The encoder may be coupled to the slowest rotating element in the motor, which is coupled to an actuation rod. Such an encoder may collect measurements over the entire range over which the element rotates, which may be, for example, 180 degrees. In this case, the output of the encoder changes as the motor rotates. In another example, the motor includes a worm (e.g.,A ball screw, for example, whose rotation can be measured and used to determine the position of the motor. However, a different position encoder may be used because the ball screw or other rotating element can rotate over a range greater than 180 and / or 360 degrees. Various suitable encoders can be used, for example, detecting changes in angular position as opposed to absolute position.

[0039] Determining a wastegate actuation force also includes determining flow forces acting on the wastegate. In one example, flow forces are determined based on a model. Alternatively, a pressure differential across the wastegate is calculated and used to determine the flow forces. In another example, a lookup table with inputs, including wastegate position, is generated to determine the flow forces. Such methods may employ the use of one or more sensors or sensor signals disposed within engine 10, including a mass air flow sensor 120, a manifold air pressure sensor 122, a throttle position signal TP, BOOST from sensor 123, and a turbocharger speed signal, and may optionally employ the use of one or more load sensors.

[0040] The compensation term described above may further account for the closing force provided by the preload (e.g., preload 210), which is a function of the spring constant and the valve position. By considering both flow forces and spring forces, among other quantities, an appropriate wastegate actuation force may be determined. In the embodiment where preload 210 is a spring, method 401 may account for the instantaneous spring force due to the pre-compression / preload of the spring in the fully closed position. In some examples, the spring force is determined based on the relationship F = kx + preload, where F is the spring force, k is the spring constant, and x is the linear displacement or deflection of the valve from the fully closed position. The spring constant k may be determined ahead of time or determined during engine operation.If it is determined that the wastegate valve should be moved toward a fully open position, the associated wastegate actuator (e.g., actuator 150) may move the wastegate valve in a direction opposite that of the closing force provided by the preload. Consequently, a greater actuation force is required than would be the case without including a preload. The compensation term may thus include an adjustment to cause an increased first current, an increased first voltage, an increased first signal, or an increased first duty cycle to be supplied to the wastegate actuator.If, instead, it is determined that the wastegate valve should be moved toward a fully closed position, the wastegate actuator may move the wastegate valve in a direction substantially parallel to the direction of the closing force provided by the preload. A smaller actuation force may thus be applied. The compensation term may then include an adjustment to cause a reduced second current, a reduced second voltage, a reduced second signal, or a reduced second duty cycle to be supplied to the wastegate actuator. In some embodiments, the second current, the second voltage, the second signal, or the second duty cycle may be less than the first current, the first voltage, the first signal, or the first duty cycle.Of course, however, the second current, the second voltage, the second signal, or the second duty cycle may be greater than the first current, the first voltage, the first signal, or the first duty cycle, and the present disclosure may be adapted for this case and also for embodiments in which a preload provides an opening force that is substantially opposite to the closing force discussed above.The compensation term may further include an adjustment to cause a third current, voltage, signal, or duty cycle to be provided to the wastegate actuator, which may, for example, be greater than the second current, voltage, signal, or duty cycle when the wastegate valve is in a third position that is more open than that for which the second current, voltage, signal, or duty cycle was used. Further, the compensation term may include an adjustment to cause a current to be provided to the wastegate actuator in response to the current position of the wastegate valve. In some cases, method 401 may determine a wastegate actuation force that is substantially equal to zero—i.e., no force needs to be provided to the wastegate.Such a determination may be made during instances where the closing force provided by the preload 210 is sufficient to maintain the wastegate valve in a position that facilitates, for example, the appropriate delivery of boost to the engine.

[0041] Furthermore, as described above, the actuating current applied to the actuator can vary even while the valve is in the fully closed position. Such adjustments can account for the preload force as well as varying differential pressure forces across the actuator pin faces. Such an approach can reduce the current required in the fully closed position while still maintaining the fully closed position.

[0042] If you now Fig. Turning to Figure 5, an example protocol 501 for determining a wastegate actuation force is shown. A first graph 510 is shown illustrating a relationship between the force generated by a preload and the position of a wastegate valve. In this example, forces acting along the wastegate actuator axis (e.g., perpendicular to the surface of wastegate valve 206) are assumed to be positive, while forces acting in substantially the opposite direction are assumed to be negative. As described above, the relationship may be modeled, for example, by the function F = kx + preload. Due to the precompression / preload, the spring force is positively offset along the y-axis when the preload provides a closing force when the wastegate valve is in the fully closed position.A second graph 520 is also shown, illustrating the relationship between the net flow force (e.g., the net sum of all flow forces in the exhaust manifold, pressure differential across the wastegate, etc.) and the wastegate valve position. Of course, graph 520 illustrates a relationship for a specific set of operating conditions (e.g., engine speed, load, etc.), and the relationship varies as the operating conditions vary. Based on these graphs, protocol 501 may determine a wastegate actuation force for a specific wastegate valve position and specific operating conditions. Protocol 501 may determine a spring force 530 at a specific wastegate valve position (e.g., the current wastegate valve position) and also determine a net flow force 540 at the same valve position.Protocol 501 may then add a spring force 530 to the net flow force 540 to obtain a wastegate actuation force 550. Of course, protocol 501 is included as a non-limiting example, and various other suitable methods may be used to determine a wastegate actuation force.

[0043] Return to Fig. 4, at 416 of method 401, the wastegate may be adjusted according to the desired boost. For example, the desired boost may be used as input to a feedforward control algorithm for adjusting the wastegate. The feedforward control algorithm may calculate a target wastegate pressure or valve position, which may be used as a component of an input to an inverse wastegate model to determine a wastegate duty cycle.

[0044] At 418 of method 410, a boost error may be calculated as the difference between the desired boost and the actual boost. The boost limiter may be adjusted according to the boost error. For example, the boost error may be used as input to a feedback control algorithm to calculate a target boost limiter pressure or target boost limiter valve position, which may be used as a component of an input to the inverse boost limiter model to determine the boost limiter duty cycle. The control algorithm may include a compensation term, as described above.

[0045] In this way, undesirable turbocharger and engine operation due to degraded wastegate control can be reduced and / or eliminated. By including a preload that provides a closing force to a wastegate valve, the wastegate valve can be maintained in a fully closed position up to a threshold pressure, ensuring that sufficient boost is delivered to an engine even in the event of wastegate degradation. When the pressure exceeds the threshold pressure, the wastegate valve can be moved toward a fully open position, limiting boost.Thus, a first increased current, voltage, signal, or duty cycle may be provided to a wastegate actuator when the wastegate valve is moved toward a fully open position, while a second decreased current, voltage, signal, or duty cycle may be provided when the wastegate valve is moved toward a fully closed position. Such a configuration may reduce the amount of downsizing and fuel economy gains in downsized engines. Furthermore, the size and power consumption of a wastegate actuator may be reduced due to the closing force provided by the preload.

[0046] It should be noted that the example control and estimation methods included herein may be used with various engine and / or vehicle system configurations. The specific methods described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, various illustrated acts, operations, or functions may be performed in parallel in the illustrated sequence, or in some cases, omitted. Likewise, 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 explanation and description.One or more of the illustrated actions or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, the described actions may graphically represent code to be programmed into the computer-readable storage medium in the engine control system.

[0047] It should be appreciated that the configurations and methods disclosed herein are exemplary in nature, and that these specific embodiments should not be considered in a limiting sense, as numerous variations are possible. For example, the above technology may be applied to V-6, R-4, R-6, V-12, horizontally opposed four, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or characteristics disclosed herein.

[0048] The following claims specifically point to certain combinations and sub-combinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims should be construed as encompassing the incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope from the original claims, are also considered to be included within the subject matter of the present disclosure.

Claims

[1] Procedure comprising: Adjusting a wastegate actuator (150) coupled to a wastegate valve (206) in an engine outlet to control an engine boost level of an engine (10), the adjustment being based on a force provided by a preload (210), wherein a boost pressure limiter actuation force (550) is calculated based on a pressure differential across the boost pressure limiter, the exhaust gas flow, the closing force provided by the preload (210) and / or the angle of the boost pressure limiter valve (206), and the boost pressure limiter actuation force (550) is used as input to an inverse boost pressure limiter model that maps a desired boost pressure limiter pressure or a desired boost pressure limiter valve position to a boost pressure limiter duty cycle for a given boost pressure limiter actuation force (550), wherein the duty cycle signal is generated by the control unit and sent to the boost pressure limiter actuator (150) to adjust the boost pressure limiter actuation force (550). [2] The method of claim 1, wherein the adjustment comprises adjusting a current supplied to the wastegate actuator (150), wherein the preload (210) comprises a spring, the spring being preloaded when the wastegate (206) is fully closed. [3] The method of claim 1, wherein the adjustment comprises adjusting a voltage supplied to the wastegate actuator (150), wherein the preload (210) comprises a spring, wherein the spring is preloaded when the wastegate (206) is fully closed. [4] The method of claim 1, wherein the adjustment comprises adjusting a duty cycle provided to the wastegate actuator (150), wherein the preload (210) comprises a spring, the spring being preloaded when the wastegate (206) is fully closed. [5] The method of claim 2, wherein the adjustment further comprises providing a first current when the wastegate valve (206) moves toward a fully open position and providing a second current when the wastegate valve (206) moves toward a fully closed position. [6] The method of claim 5, wherein the first current is greater than the second current, both currents producing a force in the same direction. [7] Boost pressure limiter, which includes: a wastegate valve (206) disposed along an exhaust manifold (46); a boost pressure limiter actuator (150) operatively coupled to the boost pressure limiter valve (206); and a preload (210) coupled to the boost pressure limiter valve (206), the preload (210) providing a closing force to the boost pressure limiter valve (206) and being preloaded in a fully closed position, wherein a control unit (12) is provided by means of which a boost pressure limiter actuation force (550) can be calculated on the basis of a pressure difference across the boost pressure limiter, the exhaust gas flow, the closing force supplied by the preload (210) and / or the angle of the boost pressure limiter valve (206), and the boost pressure limiter actuation force (550) can be used as input to an inverse boost pressure limiter model by means of which a desired boost pressure limiter pressure or a desired boost pressure limiter valve position can be mapped to a boost pressure limiter duty cycle for a given boost pressure limiter actuation force (550), wherein the duty cycle signal can be generated by the control unit (12) and sent to the boost pressure limiter actuator (150) in order to adjust the boost pressure limiter actuation force (550). [8] Boost pressure limiter according to claim 7, wherein the preload (210) is a spring. [9] Boost pressure limiter according to claim 8, wherein the spring has a spring constant selected to allow sufficient build-up of boost. [10] A boost pressure limiter according to claim 7, wherein the preload (210) maintains the boost pressure limiter valve (206) in a fully closed position up to a threshold pressure. [11] A method for controlling an engine turbocharger boost pressure limiter via an electric boost pressure limiter actuator (150), comprising: in a first, fully closed position, supplying a first current; in a second, partially open position, supplying a second current which is greater than the first; and in a third open position which is greater than the second, supplying a third current which is greater than the second, wherein a boost pressure limiter actuation force (550) is calculated based on a pressure differential across the boost pressure limiter, the exhaust gas flow, the closing force provided by the preload (210) and / or the angle of the boost pressure limiter valve (206), and the boost pressure limiter actuation force (550) is used as input to an inverse boost pressure limiter model that maps a desired boost pressure limiter pressure or a desired boost pressure limiter valve position to a boost pressure limiter duty cycle for a given boost pressure limiter actuation force (550), wherein the duty cycle signal is generated by the control unit and sent to the boost pressure limiter actuator (150) to adjust the boost pressure limiter actuation force (550). [12] The method of claim 11, further comprising, in the first fully closed position, adjusting the first current in response to operating conditions. [13] The method of claim 12, wherein the first flow is increased in the first fully closed position in response to an increase in exhaust manifold pressure, the wastegate (206) remaining in the first fully closed position. [14] The method of claim 13, wherein the first flow is reduced in the first fully closed position in response to a reduction in exhaust manifold pressure, the wastegate (206) remaining in the first fully closed position. [15] The method of claim 12, wherein the operating conditions include one or more of an exhaust pressure, an engine speed, an engine load, a spark retard, and an air / fuel ratio. [16] The method of claim 11, further comprising applying a current in response to a current position. [17] The method of claim 11, further comprising limiting an engine load in a degraded operating mode. [18] The method of claim 11, further comprising: Determining a preload force; Determining a net flow force; and Determining a boost pressure limiter actuation force (550) by adding the net flow force to the spring force. [19] The method of claim 11, wherein a desired wastegate valve position is mapped to a wastegate duty cycle for a given wastegate actuation force (550). [20] The method of claim 19, wherein the boost pressure limiter (206) is adjusted by adjusting the duty cycle provided by a control unit (12) to the electric boost pressure limiter actuator (150).

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