Multi-stage boost pressure control flap

Abstract

A method for controlling a turbocharger of an engine via a multi-stage boost pressure control valve, comprising: during a first condition, actuating a first stage of the boost pressure control valve based on the boost pressure generated by the turbocharger; and actuating a second stage of the boost pressure control valve based on the temperature of a catalyst located downstream of the turbocharger, wherein the first stage of the boost pressure control valve controls an opening located in the second stage of the boost pressure control valve.

Description

[0001] The present invention relates to a boost pressure control flap for a turbocharger.

[0002] Before reaching operating temperature, some exhaust gases may pass untreated through a catalyst located in an engine exhaust. Therefore, a general strategy for improving cold-start emissions is to increase heat flow through the engine to bring the catalyst up to operating temperature. However, an exhaust system can lose heat between the engine and the catalyst because the path length, surface area, number and shape of bends, heat flow, heat transfer coefficients, etc., between the combustion chamber and the catalyst surface provide opportunities for heat loss. A turbocharger located along this path absorbs a measurable amount of heat, which can further delay catalyst light-off time. The turbocharger can also have a negative impact on cold-start fuel economy because more air and fuel are required to overcome this additional heat loss.Document US 8 528 327 B2 shows a method for controlling a turbocharger of an engine via a multi-stage boost pressure control flap.

[0003] One solution to minimize heat loss via the turbocharger is to divert some or all of the exhaust gas around the turbocharger and directly to the catalyst, for example, by opening a wastegate connected to a turbine located in the exhaust. However, these wastegates are typically sized to provide optimal flow control for regulating the amount of boost pressure provided by the turbocharger and, even when fully open, may not provide sufficient diversion to quickly warm up a catalyst.

[0004] According to the invention, a method for controlling a turbocharger of an engine via a multi-stage wastegate comprises actuating a first stage of the wastegate based on the boost pressure generated by the turbocharger, and actuating a second stage of the wastegate based on a temperature of a catalyst downstream of the turbocharger, wherein the first stage of the wastegate controls an opening arranged in the second stage of the wastegate.

[0005] In this way, both boost control and rapid catalyst warm-up can be provided by a conventional wastegate. For example, the wastegate may have a first stage located on top of a second stage. The first stage can be opened based on the desired boost pressure. The second stage can remain closed while the first stage is open and may have an opening controlled by the first stage. The second stage can be opened when maximum turbine bypass is desired, for example, when the catalyst temperature is below the light-off temperature. This allows a relatively large amount of exhaust gas to bypass the turbine to quickly warm the catalyst, while allowing precise control of boost pressure without the need to provide additional bypass piping.

[0006] The above and other advantages and features of the present invention will become apparent from the following detailed description taken alone or in conjunction with the accompanying drawings.

[0007] It will be understood that the above summary is provided to provide, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify principal or essential features of the claimed subject matter, the scope of which is defined solely in the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate potential disadvantages mentioned above or in any part of the disclosure.

[0008] The figures show: Fig. 1 shows an example of a multi-cylinder engine with a turbocharger. Fig. 2A to Fig. 2C shows an example of a two-stage boost pressure control flap in different positions. Fig. 3 is a flowchart illustrating a method for controlling a multi-stage wastegate according to an embodiment of the present invention. Fig. 4 is a flowchart illustrating a method for controlling a multi-stage wastegate according to another method of the present invention. Fig. 5 is a flowchart illustrating a method for determining degradation of a multi-stage wastegate according to an embodiment of the present invention.

[0009] A wastegate may be provided in an engine exhaust system to allow exhaust gas to be bypassed around a turbocharger turbine, for example, so that the boost pressure generated by the turbocharger does not exceed a desired limit. Wastegates are typically sized to provide precise control of boost pressure. Due to this limitation, wastegates are often restricted in the amount of bypass they can provide. Under certain conditions, for example, when heating a catalytic converter, additional bypass beyond that allowed by the wastegate may be desired to avoid cooling exhaust gas en route to the turbine.A multi-stage wastegate may be configured with a first stage sized and controlled to provide the desired boost control, but also with a second stage larger than the first to provide additional bypass. The two-stage wastegate may be configured as a dual-blow valve or in another suitable configuration. Fig. 1 shows an engine system with a multi-stage boost pressure control valve, which is described in more detail in the Fig. 2A to Fig. 2C, and with a controller which is used to carry out the Fig. 3 to Fig. 5 is configured.

[0010] Fig. 1 is a schematic diagram illustrating an example engine 10 that may be included in a propulsion system of an automobile. The engine 10 is shown with four cylinders 30. However, other numbers of cylinders may be used in accordance with the invention. 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 the reciprocal 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 starting operation of the engine 10.

[0011] Combustion chambers 30 may receive intake air from intake manifold 44 via intake passage 42 and expel combustion gases via exhaust passage 48. Intake manifold 44 and exhaust passage 48 may selectively communicate with combustion chamber 30 via the corresponding intake valve or exhaust valve (not shown). In some embodiments, combustion chamber 30 may include two or more intake valves and / or two or more exhaust valves.

[0012] The fuel injectors 50 are directly coupled to the combustion chamber 30 for injecting fuel, depending on the pulse width of the FPW signal received from the controller 12. In this way, the fuel injectors 50 provide what is known as direct injection of fuel into the combustion chamber 30. The fuel injector can be mounted, for example, on the side of the combustion chamber or on the top of the combustion chamber. The fuel can be supplied to the fuel injectors 50 via a fuel system (not shown) that includes 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 commonly known as port injection of fuel into the intake manifold upstream of each combustion chamber 30.

[0013] Intake passage 42 may include throttle bodies 21 and 23 with throttle discs 22 and 24, respectively. In this particular example, the position of throttle discs 22 and 24 may be varied by controller 12 via signals provided to an electric motor or actuator included with throttle bodies 21 and 23, in a configuration commonly referred to as electronic throttle control (ETC). In this manner, throttle bodies 21 and 23 may be operated to vary the intake air provided to combustion chamber 30 and other engine cylinders. The position of throttle discs 22 and 24 may be provided by controller 12 via throttle position signals TP. Intake passage 42 may further include a mass air flow sensor 120 and a manifold air pressure sensor 122 for providing the corresponding MAF and MAP signals to controller 12.

[0014] The exhaust passage 48 may receive exhaust gases from the cylinders 30. The exhaust gas sensor 128 is shown coupled to the exhaust passage 48 upstream of the turbine 62 and the emissions control device 78. The sensor 128 may be selected from various suitable sensors for providing an indication of an exhaust air / fuel ratio, such as a linear or wideband oxygen sensor (UEGO), a dual-mode oxygen sensor (EGO), a heated EGO (HEGO), an HC, or a CO sensor. The emissions control device 78 may be a three-way catalyst (TWC), a NOx trap, various other emissions control devices, or combinations thereof.

[0015] 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 derived based on engine operating conditions such as speed, load, air-fuel ratio (AFR), light-off delay, etc.

[0016] The control 12 is in Fig. 1 as a microcomputer including the microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this example as a read-only memory chip 106, random access memory 108, keep-alive memory 110 and a data bus.The controller 12 may receive various signals from sensors coupled to the engine 10 in addition to the previously described signals, including measurements of the induced mass air flow (MAF) from the mass air sensor 120; the engine coolant temperature (ECT) from the temperature sensor 112, which is schematically illustrated at a location in the engine 10; a profile ignition pickup (PIP) signal from the Hall effect sensor 118 (or other type) coupled to the crankshaft 40; the throttle position (TP) from a throttle position sensor, as discussed; and the absolute manifold pressure signal MAP from sensor 122. The engine speed signal, RPM, may be generated by the controller 12 from the PIP signal. The manifold pressure signal MAP from the manifold pressure sensor may be used to provide an indication of the 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, and vice versa. During stoichiometric operation, the MAP sensor may provide an indication of engine torque. Further, this sensor, along with the sensed engine speed, may provide an estimate of the charge (including air) induced into the cylinder. For example, sensor 118, which is also used as an engine torque sensor, may generate a predetermined number of equally spaced pulses for each revolution of crankshaft 40. In some examples, read-only storage medium 106 may be programmed with computer-readable data executable by processor 102 for performing the methods described below, as well as other variations that may be anticipated but are not specifically listed.

[0017] The engine 10 may further include a compression device such as a turbocharger or a supercharger having at least one compressor 60 disposed along the intake manifold 44. With 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 for driving the compressor. With 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. Therefore, the amount of compression provided to one or more cylinders of the engine via a turbocharger or supercharger is varied by the controller 12. In some cases, the turbine 62 may, for example, drive an electric generator 64 to provide power to a battery 66 via a turbo drive 68.The power from battery 66 can then be used to drive compressor 60 via an electric motor 70. Furthermore, a sensor 123 can be disposed in intake manifold 44 to provide a BOOST signal to controller 12.

[0018] Furthermore, the exhaust passage 48 may include a wastegate 26 for bypassing exhaust gas 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 emissions control device 78. Additional details regarding the wastegate 26 are presented below. The intake passage 42 may include a compressor bypass valve 27 configured to redirect intake air around the compressor 60. The wastegate 26 and / or the compressor bypass valve 27 may be controlled by the controller 12 to open when, for example, lower boost pressure is desired.

[0019] Intake passage 42 may further include a charge air cooler (CAC) 80 for reducing the temperature of turbocharged or boosted intake gases. In some embodiments, charge air cooler 80 may be an air-to-liquid heat exchanger. In other embodiments, charge air cooler 80 may be an air-to-liquid heat exchanger.

[0020] 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 the EGR passage 140. The amount of EGR provided to the intake manifold 42 may be varied by the controller 12 via the EGR valve 142. Further, an EGR sensor (not shown) may be disposed in the EGR passage and indicate pressure, temperature, and / or exhaust gas concentration. Alternatively, EGR may be controlled using a calculated value based on signals from the MAF (upstream), MAP (intake manifold), MAT (manifold gas temperature), and crankshaft speed sensors. Further, EGR may be controlled based on the exhaust O2 sensor and / or an intake manifold oxygen sensor. Under certain conditions, the EGR system can be used to regulate the temperature of the air and fuel mixture in the combustion chamber. Fig. 1 shows a high-pressure EGR system, where the 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, where the EGR is routed from downstream of a turbocharger turbine to upstream of a turbocharger compressor.

[0021] Fig. 2A to Fig. 2C show a two-stage wastegate 200 according to an embodiment of the present invention. The wastegate 200 is a non-limiting example of the wastegate 26 of Fig. 1 and is arranged in a bypass line of a turbocharger turbine, such as the turbine 62 of Fig. 1. Fig. 2A shows the wastegate 200 in the closed position. The wastegate 200 includes a first stage 202 disposed substantially atop a second stage 204. The second stage 204 includes an opening 206 configured for exhaust gas to pass therethrough. The first stage 202, when closed, seals the opening 206. Therefore, when the wastegate 200 is in a fully closed position, no exhaust gas bypasses the turbine.

[0022] Fig. Figure 2B shows the boost pressure control flap 200 in a half-open position. The first stage 202 has been opened, causing exhaust gas (which is Fig. 2B and Fig. 2C) can flow through the opening 206 and bypass the turbine. The first stage 202 can be actuated using a suitable mechanism such as a vacuum adjuster, or electronically in response to a signal sent from a controller. In the half-open position, the second stage 204 remains closed, allowing a first, smaller amount of exhaust gas to bypass the turbine via the wastegate 200.

[0023] Fig. Figure 2C shows the wastegate 200 in the fully open position. The second stage 204 has been opened in response to a signal from a controller. Like the first stage 202, the second stage 204 can be opened via a vacuum adjuster, electronically, or by another suitable mechanism. In the fully open position, a second, larger amount of exhaust gas bypasses the turbine via the wastegate 200. Although the first stage 202 is in Fig. 2C as remaining in the open position when the second stage 204 is opened, other configurations are also possible. For example, when the second stage is opened, the first stage may be closed. In some embodiments, the first stage may move adjacent to the second stage such that if the first stage is open when the second stage is commanded to open, the first stage may maintain its open position when the second stage is open. If the first stage is closed when the second stage is commanded to open, the first stage may remain in its closed position when the second stage is open. In other embodiments, the first stage may have a default position, open or closed, to which it returns once the second stage is opened.

[0024] The first stage 202 and the second stage 204 may be sized to provide optimal turbine bypass for various operating conditions. The first stage 202 may be smaller than the second stage 204. For example, the first stage 202 may be configured to control an opening sized according to conventional wastegate openings. The second stage 204 may be configured to control a larger opening to allow for a greater amount of bypass than that typically used to control boost pressure.

[0025] While Fig. 2A to Fig. 2C illustrates a wastegate valve in which a first stage is configured directly to and for regulating an opening in a second stage, other wastegate configurations are also possible. For example, the valve may be a flap valve with a first flap that opens to admit a smaller amount of exhaust gas than that permitted by the second flap. Additionally or alternatively, the valve may have more than two stages for providing further varying amounts of exhaust bypass.

[0026] In relation to Fig. 3, a method 300 for controlling a multi-stage wastegate is illustrated. Method 300 may be executed by a controller according to instructions stored thereon for regulating a wastegate, such as wastegate 26 and / or wastegate 200. Method 300 includes, at 302, determining engine operating parameters. The engine operating parameters may include engine speed, engine load, engine temperature, boost pressure, catalyst temperature, etc. At 304, method 300 includes determining whether the catalyst temperature is below a threshold. The catalyst temperature may be determined from a temperature sensor located in or near the catalyst or may be estimated based on operating conditions such as engine temperature and exhaust mass air flow.The temperature threshold may be a fixed temperature, such as the catalyst light-off temperature, below which the catalyst no longer properly converts emissions in the exhaust. If the catalyst temperature is below the threshold, the method proceeds to 310, which is described in more detail below.

[0027] If the catalyst temperature is below the temperature threshold, method 300 proceeds to 306 to open the second stage of the wastegate. By opening the second stage, a relatively larger amount of exhaust gas bypasses the turbine before reaching the catalyst than when the first stage of the wastegate is opened. Therefore, additional cooling of the exhaust gases that occurs as it passes through the turbine may be prevented, and the catalyst may reach its light-off temperature more quickly. To compensate for airflow disturbances that may occur due to the large amount of exhaust gas bypassing the turbine, additional operating parameters may be adjusted at 308. For example, the turbine may not receive a sufficient amount of exhaust gas to effectively operate the compressor. Therefore, intake air may bypass the compressor via the compressor bypass valve (CBV) opening.The CBV can be opened in conjunction with the second stage of the wastegate. Additional operating parameters can be adjusted to compensate for the reduced intake air compression, such as throttle valve adjustment, air-fuel ratio adjustment, etc.

[0028] Returning to 304, if the catalyst temperature is not below the threshold, method 300 proceeds to 310 to determine whether the desired boost pressure is less than the measured boost pressure. The boost pressure may be measured by a sensor, such as sensor 123 of Fig. 1 . The desired turbocharger pressure may be dependent on engine speed, driver requested torque, and / or other parameters. If the desired boost pressure is less than the measured boost pressure, method 300 proceeds to 312 to close or maintain the first and second stages in the fully closed position to direct exhaust gas immediately upstream of the turbine without bypassing the turbine, thereby providing maximum boost pressure to achieve the desired boost pressure value. If the desired boost pressure is less than the measured boost pressure, method 300 proceeds to 314 to open the first stage of the wastegate based on the desired boost pressure. The first stage of the wastegate opens according to a difference between the desired and measured boost pressure.Further, the second stage of the wastegate may be maintained in the closed position at 316 to allow a smaller amount of exhaust gas to bypass the turbine.

[0029] Although Fig. 3 illustrates the control of a multi-stage boost pressure control valve based on boost pressure and catalyst temperature, under certain circumstances the boost pressure control valve can be controlled based on additional operating parameters.

[0030] Fig. 4 is a flowchart illustrating a method 400 for adjusting wastegate position under various operating conditions. Method 400 includes determining engine operating parameters at 402. These engine operating parameters may include engine speed and load, engine temperature, boost pressure, MAF, MAP, etc. At 404, it is determined whether the engine is operating under steady-state conditions. Steady-state conditions may be engine speed and load and other operating parameters that remain relatively constant over a predetermined period of time. If no steady-state conditions are indicated, the engine may be operating in a transient condition, such as a sudden torque request due to the driver opening the throttle or a torque reduction due to the driver closing the throttle. Therefore, the amount of desired boost pressure may change rapidly.Therefore, if the engine is not operating under steady-state conditions, method 400 proceeds to 406 to control the wastegate to provide a fast transient boost request. Depending on the type of transient condition, controlling the wastegate to provide a fast transient boost request may include closing the second stage of the wastegate even if the catalyst temperature is below the threshold to prevent a reduction in boost during the transient condition. In other transient conditions, the second stage may be opened even if the catalyst temperature is above the threshold to avoid potential compressor surge and / or turbine degradation during the transient condition.

[0031] If the engine is operating under steady-state conditions, method 400 proceeds to 408 to determine if the compressor is operating with a surge below a threshold. The compressor surge may be a result of a high pressure ratio in the compressor combined with low flow through the compressor, and may result in noise and compressor degradation. The threshold surge may be an amount of surge that is greater than that which can be delivered by opening the first stage of the wastegate and / or the CBV. Therefore, if the compressor surge is above the threshold, method 400 proceeds to 410 to open the second stage of the wastegate and provide maximum bypass to reduce the pressure ratio in the compressor and release the surge.Under these conditions, the second stage can be opened even when the catalyst is at its warmed-up operating temperature.

[0032] If the compressor is operating with the surge pressure below the threshold, method 400 proceeds to 412 to determine if the turbine temperature is below a threshold. Under certain conditions, such as during clean operation or a regeneration event of a downstream emissions control device, the exhaust gas may be heated to such high levels that turbine degradation is possible. To prevent this degradation, the exhaust gas may be routed to the catalyst without passing through the turbine. If the turbine is above the threshold temperature, method 400 proceeds to 410 to open the second stage of the wastegate to bypass the very hot exhaust gas around the turbine.If the turbine is below the threshold temperature, method 400 proceeds to 414 to control the first stage of wastegate based on boost pressure and the second stage of wastegate based on catalyst temperature, as described above with respect to FIG. Fig. 3 described.

[0033] As with regard to Fig. 3 and Fig. As explained in Section 4, controlling the wastegate so that the second stage can be opened independently of the first stage enables optimal boost control, prevents possible turbine and compressor degradation, and / or maintains strict emissions control. However, this control depends on the appropriate operation of both the first and second stages. Should degradation of one of the stages occur, Fig.5 illustrates a method 500 that may be performed to maintain control in response to the wastegate degradation. Method 500 may be performed during conditions where fluctuations in boost pressure are only attributable to changes in wastegate position, e.g., during steady-state conditions.

[0034] At 502, method 500 includes monitoring boost pressure in response to wastegate actuation. If both the first and second stages are commanded to open, the amount of boost provided by the turbocharger should decrease; if one stage is commanded to open and close, the amount of boost should increase. If boost pressure does not change in a manner consistent with wastegate actuation, degradation of one of the stages may be indicated. Therefore, at 504, method 500 includes determining whether a change in boost pressure differs from wastegate actuation. For example, if the first stage is open, boost pressure should drop by a certain amount corresponding to the position of the first stage. If boost pressure remains the same or does not decrease by the expected amount, degradation of the first stage may be indicated.If the amount of boost pressure and actuation do not differ, method 500 proceeds to 506 where no degradation is indicated and method 500 exits.

[0035] If the boost amount and the actuation amount are different, method 500 proceeds to 508 to indicate wastegate impairment and to determine at 510 whether the first stage of the wastegate is impaired, for example, by determining which stage was actuated during the monitoring of 502. Alternatively or additionally, the first and second stages may be commanded to close, wherein the first stage may thereafter be commanded to open and a subsequent change in boost pressure is monitored to check if the first stage is impaired. If the first stage is impaired, method 500 proceeds to 512 to control actuation of the second stage of the wastegate based on the boost pressure and the catalyst temperature.In this way, even if the first stage is impaired, boost control can be provided by the second stage; since the second stage controls an opening that is larger than the opening controlled by the first stage, the boost control provided by the second stage can be coarser control than that provided by the first stage.

[0036] If the first stage is not degraded, the second stage is indicated as degraded, and method 500 proceeds to 514 to control actuation of the first stage of the wastegate based on the boost pressure and the catalyst temperature. This may include opening the first stage of the wastegate when the catalyst temperature is below the threshold (e.g., when the catalyst temperature is below the light-off temperature), even if the measured boost pressure is not greater than the desired boost pressure. After 512 or 514, method 500 proceeds to 516 to signal the degradation to an operator of the vehicle, for example, by illuminating a malfunction indicator and / or setting a diagnostic code indicating degradation of the first and / or second stages of the wastegate.

[0037] Therefore, the methods and systems described herein provide a method for controlling a turbocharger of an engine using a multi-stage wastegate. The method includes, during a first condition, actuating a first stage of the wastegate based on the boost pressure generated by the turbocharger and actuating a second stage of the wastegate based on a temperature of a catalyst downstream of the turbocharger. The method further includes, during a second condition, actuating the second stage of the wastegate based on both the boost pressure and the catalyst temperature. The first condition may include a non-degradation state of the wastegate, and the second condition may include degradation of the first stage of the wastegate.

[0038] For example, a method includes, during a first set of conditions, bypassing a first amount of exhaust gas past a turbocharger via a first opening controlled by a first stage of a wastegate, and during a second set of conditions, bypassing a second, larger amount of exhaust gas past the turbocharger via a second opening controlled by a second stage of the wastegate.

[0039] For example, an engine system includes an exhaust system having a turbocharger turbine located upstream of a catalyst, a two-stage wastegate, and a controller with instructions to, when the catalyst temperature is above a threshold, actuate a first stage of the two-stage wastegate based on the closed two-stage wastegate, and, when the catalyst temperature is below the threshold, open the second stage of the two-stage wastegate.

[0040] It will be appreciated that the configurations and methods disclosed herein are exemplary, and that these specific embodiments are not to be considered limiting, as numerous variations thereof are possible. For example, the technology described above may be applied to V-6, I-4, I-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.

[0041] The following claims highlight certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or an equivalent thereof. Such claims are to be construed as including the inclusion of one or more such elements and neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims that are broader, narrower, the same, or different in scope than the original claims are intended to be included within the subject matter of the present disclosure.

Claims

[1] A method for controlling a turbocharger of an engine via a multi-stage wastegate, comprising: during a first condition, actuating a first stage of the wastegate based on the boost pressure generated by the turbocharger; and actuating a second stage of the wastegate based on the temperature of a catalyst disposed downstream of the turbocharger, wherein the first stage of the wastegate controls an opening disposed in the second stage of the wastegate. [2] The method of claim 1, wherein actuating the first stage of the wastegate further comprises opening the wastegate by a first, smaller amount, and wherein actuating the second stage of the wastegate further comprises opening the wastegate by a second, larger amount. [3] The method of claim 1, wherein actuating the second stage of the wastegate based on the temperature of the catalyst further comprises opening the second stage when the catalyst temperature is below a first threshold. [4] The method of claim 3, wherein actuating the second stage of the wastegate based on the temperature of the catalyst further comprises closing the second stage of the wastegate when the catalyst temperature is above a second threshold. [5] The method of claim 3, further comprising opening a compressor bypass valve when the catalyst temperature is below the first threshold. [6] The method of claim 1, further comprising determining a desired boost pressure according to engine operating conditions and actuating the first stage of the wastegate according to a difference between the measured boost pressure and the desired boost pressure. [7] A method for controlling a turbocharger of an engine via a multi-stage wastegate, comprising: during a first condition comprising a non-impairment state of the boost pressure control valve, Actuating a first stage of the wastegate based on the boost pressure generated by the turbocharger; and actuating a second stage of the wastegate based on the temperature of a catalyst located downstream of the turbocharger during a second condition involving impairment of the first stage of the boost pressure control valve, Actuate the second stage of the wastegate based on both boost pressure and catalyst temperature. [8] An engine system comprising: an exhaust system having a turbocharger turbine upstream of a catalyst; a two-stage wastegate; and a controller having instructions: when the catalyst temperature is above a threshold, actuating a first stage of the two-stage wastegate based on boost pressure, wherein a second stage of the two-stage wastegate remains closed; and when the catalyst temperature is below the threshold, opening the second stage of the two-stage wastegate, wherein the first stage is disposed on the second stage, and wherein the second stage has an opening configured to admit exhaust gas when the first stage is open. [9] The engine system of claim 8, wherein the threshold temperature is the catalyst light-off temperature and wherein the first stage of the two-stage wastegate is less than the second stage of the two-stage wastegate. [10] The engine system of claim 8, further comprising a compressor of the turbocharger disposed at an inlet of the engine, wherein the controller further comprises instructions to open a compressor bypass valve corresponding to the opening of the second stage of the two-stage wastegate. [11] The engine system of claim 8, wherein the controller further comprises instructions to maintain the first stage of the two-stage wastegate in a default position when the catalyst temperature is below the threshold.

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