SYSTEMS AND METHOD FOR A COMPRESSED AIR STORAGE TANK COUPLED TO A TURBINE

Abstract

Method for a turbocharged engine (10), comprising: as a reaction to a tip-in, reducing turbo lag by releasing pressurized charge from a compressed air reservoir (54) into an exhaust manifold (36); and during a first tip-out at a higher engine speed after the tip-in, the compressed air reservoir (54) is charged with at least some compressed intake air from an intake manifold (22); and during a second tip-out at a lower engine speed after the tip-in, the compressed air reservoir (54) is charged with at least some burnt exhaust gases from the exhaust manifold (36).

Description

Field of invention

[0001] The present application relates to the field of automotive engineering and in particular to the intake of air in motor vehicle engine systems. Background and brief description of the invention

[0002] A turbocharged engine can offer higher fuel efficiency and lower emissions than a naturally aspirated engine of similar power output. However, during transitional conditions, the power, fuel efficiency, and emissions control performance of a turbocharged engine can suffer. Such transitional conditions can include rapidly increasing or decreasing engine loads, engine speeds, or airflow rates. For example, if the engine load increases rapidly, the compressor of a turbocharger may require increased torque to deliver an increased airflow rate. However, such torque may not be available if the turbine driving the compressor has not reached full spool-up. As a result, an undesirable power lag may occur before the intake airflow builds up to the required strength.

[0003] It has already been recognized that a turbocharged engine system can be configured to store compressed air and use the stored compressed air to supplement the air charge from the turbocharger's compressor. For example, Pursifull et al. describe in US Patent 2011 / 0132335A1 a system in which compressed air is stored in a compressed air reservoir and released into the intake manifold when insufficient compressed air is available from the turbocharger's compressor. Specifically, the compressed air reservoir is charged with intake air and / or exhaust gas from one or more non-fueled cylinders. By releasing additional compressed air from the reservoir into the intake manifold, torque equal to the amount of air released can be provided to meet the torque demand during turbine spool-up.Further state of the art is known from FR 2 906 309 A1, DE 198 33 134 C1, DE 80 23 061 U1 and DE 10 2006 055 591 A1.

[0004] The inventors of this system, however, have recognized potential problems. For example, if the compressed air reservoir has a small volume, the charge air may initially supply enough air to provide the desired increased torque, but after the air supply is exhausted, for example at higher engine speeds, the turbine may still not have reached full speed, and thus the torque may drop again after the initial increase. Such performance can be worse than no compensation at all. Furthermore, the pressure of the air supplied by the compressed air reservoir may not be high enough to overcome the boost pressure, or the charge in the reservoir may be primarily exhaust gas and thus provide little excess oxygen for combustion to compensate for turbo lag.

[0005] The object of the present invention is to provide an improved compressed air storage system for a vehicle. This object is achieved by the features of the independent claims. Advantageous embodiments of the invention are the subject of the dependent claims.

[0006] Thus, at least some of the problems described above can be resolved with a method for a turbocharged engine. In one embodiment, the method involves reducing turbo lag in response to a tip-in by releasing pressurized charge from a compressed air reservoir into an exhaust manifold. In this way, pressurized charge is released into the exhaust manifold to rapidly increase exhaust pressure.

[0007] For example, during the preceding engine operation before tip-in, the compressed air reservoir may already be filled with primarily combusted exhaust gas from the exhaust manifold. In response to tip-in, the pressurized charge, including the combusted exhaust gas, can be discharged into the exhaust manifold. Consequently, the intake pressure at the turbine can be increased to accelerate turbine spool-up. By delivering the charge to the exhaust manifold, it can be more easily distributed over a longer period, as the turbine delivers the gas at a lower rate than the engine's intake side. In this way, the increased intake pressure can help eliminate turbo lag and maintain a steadily increasing engine output while responding to tip-in.

[0008] It is understood that the foregoing brief description serves to present a selection of concepts, which are described in detail in the detailed description, in a simplified form. It is not intended to highlight any decisive or essential features of the claimed subject matter, the scope of which is clearly defined by the claims following the detailed description. Furthermore, the subject matter is not limited to implementations that eliminate disadvantages mentioned above or in part of this disclosure. Brief description of the drawings Fig. Figure 1 schematically represents aspects of an exemplary motor system according to an embodiment of the present disclosure. Fig. Figure 2 illustrates an exemplary procedure for charging a compressed air storage tank with combustion exhaust gas and / or drawn-in fresh air. Fig. Figure 3 illustrates an exemplary procedure for releasing pressurized cargo from a compressed air reservoir into an intake or exhaust manifold. Fig. Figure 4 illustrates an exemplary procedure for releasing pressurized charge from a compressed air reservoir to provide high-pressure EGR. Fig. Figure 5 illustrates an exemplary procedure for releasing pressurized charge from a compressed air reservoir into an intake manifold, while the compressor's boost pressure is pre-charged. Fig. 6 to Fig. Figure 8 shows exemplary charging and draining processes of a compressed air storage tank according to the present disclosure. Detailed description

[0009] The following description concerns systems and methods for reducing turbo lag in a turbocharged engine that incorporates a compressed air reservoir, such as in the engine system of Fig. 1. By releasing pressurized charge from the compressed air reservoir into the intake or exhaust manifold in response to a tip-in, exhaust gas temperatures and pressures can be rapidly increased, and the turbine of a turbocharger can be quickly spooled up. An engine control unit can be designed to execute a control program such as the exemplary procedure described by Fig. 2. To charge the compressed air storage tank with combustion exhaust gas from the exhaust manifold and / or fresh air drawn in from the intake manifold when charging opportunities are available. The control system can also be configured to run a control program such as the exemplary method described by Fig. 3. To execute the pressurized charge from the compressed air reservoir into the intake manifold and / or the exhaust manifold, based on engine operating conditions and the composition of the charge available in the reservoir. The control system can be configured to execute a control program, such as the exemplary procedure described above, when venting into the intake manifold. Fig. 4. To execute a procedure to vent pressurized charge from the reservoir into the intake manifold while holding one intake throttle valve closed, and then to open the throttle valve once the throttle intake pressures have been raised sufficiently. This tuning allows for the advantageous increase of throttle intake pressures while the torque demand is met by charge vented from the compressed air reservoir. As in Fig. As shown in Figure 5, the control system can also be designed, during selected charging conditions when high-pressure EGR is requested, to increase the pressure of combustion exhaust gas stored in the accumulator by mixing it with compressed intake air and then releasing the high-pressure charge mixture into the intake manifold. Exemplary charge and discharge operations are described in Figure 5. Fig. 6 to Fig. Figure 8 illustrates this. By increasing the exhaust gas temperature and pressures, the turbine's spool-up can be accelerated to reduce turbo lag. Using the compressed air reservoir to provide high-pressure EGR during turbocharged operating conditions can improve the turbocharged engine's performance.

[0010] Fig. Figure 1 schematically shows aspects of an exemplary engine system 100, which includes an engine 10. In the illustrated embodiment, the engine 10 is a turbocharged engine connected to a turbocharger 13, which includes a compressor 14 driven by a turbine 16. Specifically, fresh air is guided along the intake line 42 via the air cleaner 12 to the engine 10 and flows to the compressor 14. The compressor can be any suitable intake air compressor, such as an engine-driven or a turbocharger-driven compressor. In the engine system 10, however, the compressor is a turbocharger-driven compressor mechanically connected to a turbine 16 via a shaft 19, with the turbine 16 being driven by expanding engine exhaust gas. In one embodiment, the compressor and turbine can be integrated within a twin-scroll turbocharger.In another embodiment, the turbocharger can be a variable turbine geometry turbocharger (VTG turbocharger) in which the turbine geometry is actively varied depending on the engine speed.

[0011] As in Fig. As shown in Figure 1, the compressor 14 is connected to the throttle valve 20 via the charge air cooler 18. The throttle valve 20 is connected to the intake manifold 22 of the engine. From the compressor, the compressed air flows through the charge air cooler and the throttle valve into the intake manifold. The charge air cooler can be, for example, an air-to-air or an air-to-water heat exchanger. In the Fig. In the embodiment shown in Figure 1, the pressure of the air charge in the intake manifold is measured by the manifold pressure sensor (MAP sensor) 24. A bypass valve (not shown) can be connected in series between the inlet and outlet of the compressor 14. The compressor bypass valve can be a normally closed valve designed to open under selected operating conditions to relieve excess boost pressure. For example, the compressor bypass valve can open during deceleration to prevent compressor surging.

[0012] The intake manifold 22 is connected to a series of combustion chambers 30 via a series of intake valves (not shown). The combustion chambers are further connected to the exhaust manifold 36 via a series of exhaust valves (not shown). In the illustrated embodiment, a single exhaust manifold 36 is shown. In other embodiments, however, the exhaust manifold can include several exhaust manifold sections. Designs with multiple exhaust manifold sections can allow exhaust gases from different combustion chambers to be routed to different locations in the engine system.

[0013] In one embodiment, the exhaust and intake valves can each be electronically actuated or controlled. In another embodiment, the exhaust and intake valves can each be actuated or controlled via a camshaft. Regardless of whether they are actuated electronically or via a camshaft, the timing of the opening and closing of the exhaust and intake valves can be adjusted as required for the desired combustion and emission control performance.

[0014] Fig. Figure 1 shows the electronic control system 38, which can be any electronic control system of the vehicle into which the engine system 10 is installed. In embodiments in which at least one intake or exhaust valve is designed to open and close according to an adjustable timing, the adjustable timing can be controlled by the electronic control system to control the amount of exhaust gas in a combustion chamber during ignition. The electronic control system can also be designed to control the opening, closing, and / or adjustment of various other electronically actuated valves in the engine system—for example, throttle valves, compressor bypass valves, boost pressure control valves, EGR valves and shut-off valves, and various accumulator intake and exhaust valves required to perform the control functions described herein.Furthermore, to evaluate operating conditions related to the control functions of the engine system, the electronic control system can be functionally connected to several sensors located throughout the engine system – flow sensors, temperature sensors, pedal position sensors, pressure sensors, etc.

[0015] One or more fuels, such as gasoline, alcohol-fuel mixtures, diesel, biodiesel, compressed natural gas, etc., can be supplied to the combustion chambers 30. The fuel can be introduced into the combustion chambers via direct injection, port injection, throttle valve injection, or any combination thereof. Combustion in the combustion chambers can be initiated by ignition via spark plugs and / or by auto-ignition.

[0016] As in Fig. As shown in Figure 1, exhaust gas from one or more exhaust manifold sections is directed to the turbine 16 to drive the turbine. If reduced turbine torque is desired, a portion of the exhaust gas can instead be routed through a boost pressure control valve (not shown), bypassing the turbine. The combined flow from the turbine and the boost pressure control valve then flows through the emission control device 70. In general, one or more emission control devices 70 can include one or more exhaust aftertreatment catalysts designed to catalytically treat the exhaust gas stream, thereby reducing the amount of one or more substances in the exhaust gas stream. For example, an exhaust aftertreatment catalyst can be designed to reduce NOₓ. x to capture from the exhaust stream when the exhaust stream is lean, and the captured NO xto reduce NO when the exhaust gas flow is rich. In other examples, an exhaust aftertreatment catalyst may be designed to reduce NO. x to disproportionate or NO x to selectively reduce the emissions with the aid of a reducing agent. In further examples, an exhaust aftertreatment catalyst can be designed to oxidize residual hydrocarbons and / or carbon monoxide in the exhaust stream. Various exhaust aftertreatment catalysts with this type of functionality can be arranged separately or together in special coatings (washcoats) or elsewhere in the exhaust aftertreatment stages. In some embodiments, the exhaust aftertreatment stages can include a regenerable diesel particulate filter designed to capture and oxidize soot particles in the exhaust stream.

[0017] All or part of the treated exhaust gas from the emission control device 70 can be discharged into the environment via the exhaust line 35. Depending on the operating conditions, however, a portion of the exhaust gas can instead be diverted into the EGR line 51, through the EGR cooler 50 and the EGR valve 52 to the compressor inlet 14. In this way, the compressor is designed to draw in exhaust gas diverted downstream from the turbine 16. The EGR valve can be opened to allow a controlled quantity of cooled exhaust gas into the compressor inlet for desired combustion and emission control performance. Thus, the engine system 10 is designed to provide external low-pressure (LP) EGR. The rotation of the compressor, in addition to the relatively long flow path of the LP EGR in the engine system 10, provides excellent homogenization of the exhaust gas into the intake air charge.Furthermore, the arrangement of the EGR take-off and mixing points provides a very effective cooling of the exhaust gas for the purpose of increased available EGR mass and improved performance.

[0018] In engine system 10, the compressor 14 is the primary source of compressed intake air, but under certain conditions, the amount of intake air available from the compressor may be insufficient. Such conditions include periods of rapidly increasing engine load, such as immediately after starting, during tip-in, or after exiting overrun fuel cut-off. During overrun fuel cut-off, fuel injection to one or more engine cylinders is selectively deactivated in response to specific vehicle deceleration or braking conditions. During at least part of these rapidly increasing engine load conditions, the amount of compressed intake air available from the compressor may be limited because the turbine has not reached a sufficiently high rotational speed (for example, due to low exhaust gas temperature or low exhaust pressure).The time required for the turbine to spool up and drive the compressor so that it can provide the necessary amount of compressed intake air is therefore called turbo lag. During turbo lag, the level of torque may not match the torque demand, resulting in a drop in engine power.

[0019] In light of the aforementioned problems, the engine system 100 includes a compressed air reservoir 54. The compressed air reservoir can be any reservoir of suitable size designed to store pressurized charge for later release. For the purposes of this document, the pressurized charge is defined as the gas stored in the reservoir 54. Therefore, the pressurized charge stored in the compressed air reservoir can consist exclusively of clean intake air (e.g., compressed intake air drawn from the intake manifold), exclusively of combustion exhaust gas (e.g., combustion exhaust gases drawn from the exhaust manifold), or a combination thereof (e.g., a mixture of intake air and exhaust gas with a defined EGR percentage). In one embodiment, the compressed air reservoir can be designed to store charge at a maximum pressure generated by the compressor 14.Various inlets, outlets, and sensors can be connected to the compressed air reservoir, as will be explained below. In the section on... Fig. In the embodiment shown in Figure 1, the pressure sensor 56 is connected to the compressed air reservoir and is designed to react to the charge pressure therein.

[0020] In the engine system 100, the compressed air reservoir 54 is selectably connected upstream and downstream of the intake throttle valve 20 to the intake manifold 22. More specifically, the compressed air reservoir 54 is designed to discharge pressurized charge downstream of the intake throttle valve 20 into the intake manifold via the compressed air reservoir intake discharge valve 84. The compressed air reservoir intake discharge valve can be a normally closed valve that is instructed to open when a flow of charge from the compressed air reservoir to the intake manifold is desired. In some scenarios, the pressurized charge can be discharged when the throttle valve is at least partially open. Therefore, the check valve 94 can be connected upstream of the throttle valve and oriented to prevent the discharge of pressurized charge from the compressed air reservoir backward through the throttle valve.In other embodiments, the check valve can be omitted, and other measures can be taken to prevent backflow through the throttle valve. In some embodiments, a pressure recovery cone (not shown) can be connected in fluid communication between the compressed air reservoir and the intake manifold, so that pressurized charge, after being discharged from the compressed air reservoir, is routed through the pressure recovery cone. If present, the pressure recovery cone converts flow energy back into pressure energy under flow conditions by preventing flow separation from the pipe wall. However, in alternative embodiments, the pressure recovery cone may not be included.

[0021] In further embodiments, for example, when the pressurized charge is routed to the intake manifold during supercharged engine operating conditions, the pressurized charge can be discharged while the intake throttle valve is held closed for a period of time. As in Fig. As shown in more detail in Figure 5, the throttle valve can be kept closed until the compressed air reservoir is fully charged or until a limit for the throttle intake pressure is reached. Then, the intake bleed valve can be closed while the intake throttle valve opens to allow compressed intake air to be vented from the compressor into the intake manifold. By temporarily keeping the throttle valve closed while the pressurized charge is vented into the supercharged engine, backflow into the reservoir can be reduced, while also allowing the pressure of the compressed intake air to be raised beyond what would otherwise be possible.A combination of releasing air from the reservoir under high pressure followed by high-pressure air from the compressor allows for better satisfaction of torque demand at the time of tip-in, while also accelerating the turbine's spin-up and reducing turbo lag.

[0022] In some embodiments, keeping the throttle valve closed for a period of time can lead to problems with the compressor priming when the throttle valve is subsequently opened. If supercharged operation is limited by priming when the throttle valve opens, the control system can open a pressure relief valve during throttle valve opening to prevent compressor priming.

[0023] The compressed air reservoir 54 can also be charged with air drawn from the intake manifold downstream of the compressor 14 and charge air cooler 18. More specifically, the compressed air reservoir 54 is configured to be charged via the compressed air reservoir charging valve 82 with compressed intake air from the intake manifold, drawn downstream of the compressor 14 and upstream of the intake throttle valve 20. The compressed air reservoir charging valve 82 can be a normally closed valve that is instructed to open when a flow of pressurized intake air charge from the intake manifold to the compressed air reservoir is desired. In one example, during low-charge conditions, the charging valve can be opened to force at least some of the compressor-pressurized intake air into the compressed air reservoir 54.As another example, during high-boost conditions, the intake charge valve can be opened to force some compressed intake air into the compressed air reservoir 54, where it is mixed with pre-stored exhaust gas to generate high-pressure EGR. Then, when a transient EGR request is received under boosted conditions, the high-pressure EGR is vented into the intake manifold via the intake vent valve 84 to provide the requested high-pressure EGR. A check valve 92, connected upstream of the intake charge valve 82, allows compressed air from the compressor to flow into and be stored in the compressed air reservoir under high throttle inlet pressure (TIP) conditions, but prevents compressed air from flowing back into the compressor under low throttle inlet pressure conditions.

[0024] The compressed air reservoir 54 is also shown as being selectably connectable to the exhaust manifold 36 upstream of the turbine 16. More specifically, the compressed air reservoir 54 is configured to discharge pressurized charge upstream of the turbine 16 into the exhaust manifold via the compressed air reservoir exhaust valve 88. The compressed air reservoir exhaust valve 88 can be a normally closed valve that is instructed to open when a flow of charge from the compressed air reservoir to the exhaust manifold is desired. A check valve 98 can be connected downstream of the exhaust valve and configured to prevent the backflow of the pressurized charge into the compressed air reservoir. In other embodiments, the check valve can be omitted, and other measures can be taken to prevent backflow into the reservoir.

[0025] The compressed air storage tank 54 can also be charged with combustion exhaust gases drawn upstream of the turbine 16 from the exhaust manifold. More specifically, the compressed air storage tank 54 is configured to be charged with combustion exhaust gases drawn upstream of the turbine 16 from the exhaust manifold via the compressed air storage tank exhaust gas charging valve 86. The compressed air storage tank exhaust gas charging valve 86 can be a normally closed valve that is instructed to open when a flow of combustion exhaust gas from the exhaust manifold to the compressed air storage tank is desired. In one example, during low-boost or low-engine-speed load conditions, the exhaust gas charging valve can be opened to force at least some combustion exhaust gas into the compressed air storage tank 54. In this way, the EGR percentage of the compressed air storage tank charge can be increased.A check valve 96, connected upstream of the exhaust gas charging valve 86, allows combustion exhaust gas from the exhaust manifold to flow into the compressed air reservoir and be stored there, but prevents the exhaust gas from flowing back.

[0026] In this way, during a first condition, the compressed air storage tank can be selectively charged exclusively with intake air from the intake manifold downstream of a compressor, whereas during a second condition, the compressed air storage tank can be selectively charged exclusively with combustion exhaust gas from the exhaust manifold upstream of a turbine.

[0027] More precisely, the design of the compressed air reservoir 54, relative to the engine's intake and exhaust manifolds, allows for various options for charging and discharging the reservoir. As a first example, when the engine system is operating in a first mode, the reservoir can be charged with compressed intake air from the intake manifold. This compressed intake air can then be discharged into the intake manifold in response to a tip-in (or during high-boost conditions) to reduce turbo lag and assist turbine spool-up. As a second example, when the engine system is operating in a second mode, the reservoir can be charged with compressed intake air from the intake manifold, and this compressed intake air can be discharged into the exhaust manifold to increase exhaust gas temperatures and assist turbine spool-up.As a third example, the accumulator can be charged with exhaust gas from the exhaust manifold, for instance, when the engine system is operating in a third mode. Then, during boosted conditions, when EGR is requested, the exhaust gas can be vented into the intake manifold to provide the desired EGR. As a fourth example, the accumulator can be charged with exhaust gas from the exhaust manifold, for instance, when the engine system is operating in a fourth mode. Then, in response to a tip-in, the exhaust gas can be vented into the exhaust manifold to increase the exhaust pressure upstream of the turbine and assist in turbine spin-up. In still other examples, the accumulator can be charged with at least some exhaust gas and at least some compressed intake air to provide a boost charge of a selected composition (e.g.,desired EGR percentage, desired air-fuel ratio, etc.), and then at a later time the pressurized charge can be released either into the intake manifold (for example, to provide EGR) or into the exhaust manifold (for example, to increase the exhaust pressure).

[0028] In some embodiments, the compressed air reservoir 54 can also be charged with the residues from one or more cylinders that are not supplied with fuel (that is, with fuel-free, unburned exhaust gases). Specifically, when the engine 10 is operated in overrun fuel cut-off mode, in which some of the combustion chambers do not receive fuel and merely pump the intake air through their respective intake valves, the air pumped and thereby compressed by the combustion chambers that are not supplied with fuel can be drawn from the exhaust manifold via the exhaust gas charging valve 86 and stored in the compressed air reservoir 54.

[0029] In the various engine systems described above, as well as in other systems that fully comply with this disclosure, pressurizing air or an air / exhaust gas mixture in a compressed air reservoir can cause water to condense inside the reservoir. Therefore, in one embodiment, a drain valve (not shown) can be connected to the compressed air reservoir 54. The drain valve can be opened as needed by the electronic control system 38 to allow the condensate to drain in liquid form from the compressed air reservoir onto the road surface below the vehicle, or to direct it to the vehicle's exhaust system, where it is vaporized and released as steam.

[0030] The design of Fig. 1. This allows the venting of air stored in the compressed air reservoir in response to at least one tip-in condition, where the throttle valve opens suddenly and the compressor is spinning too slowly to provide the desired manifold manifold manifold pressure (MAP). As explained in detail below, during at least some tip-in conditions (for example, when the boost level at tip-in is lower and the expected turbo lag is greater), a larger degree of ignition retard can be used while venting air from the compressed air reservoir to rapidly raise the exhaust gas temperature and assist turbine spin-up. During other tip-in conditions (for example, when the boost level at tip-in is higher and the expected turbo lag is less pronounced), a smaller degree of ignition retard can be used while venting air from the compressed air reservoir (e.g.,(no ignition delay) to provide additional engine torque (corresponding to the amount of charge air released) to meet the torque demand while the compressor reaches the desired capacity.

[0031] In some embodiments, at least some of the engine's cylinders can be configured to retard their ignition timing during the discharge of charge air into the intake manifold to heat the exhaust gas and assist turbine spool-up. Simultaneously, other cylinders can be configured to maintain their ignition timing during charge air discharge to generate torque. To mitigate potential problems arising from a torque differential between cylinders, the cylinders enabling exhaust gas heating and those enabling torque generation can be selected based on their firing order. In this way, accelerating turbine spool-up during torque delivery can reduce turbo lag while increasing the engine's net combustion torque.

[0032] The designs described above enable various methods for supplying charge from air and / or combustion exhaust gas to a combustion chamber of an engine or for spinning up a turbine. Accordingly, some of these methods are now described by way of example with reference to the above design. It is understood, however, that the methods described here, as well as others that are fully within the scope of this disclosure, can also be implemented using other designs. The methods presented herein include various measurement and / or detection processes that can be carried out using one or more sensors arranged in the engine system. The methods also include various calculation, comparison, and decision-making processes that can be performed in an electronic control system functionally connected to these sensors.The procedures also include various hardware actuation processes that the electronic control system can selectively instruct in response to the decision-making processes.

[0033] Now, with reference to Fig. 2 is an example program 200 for charging the compressed air reservoir of Fig. Figure 1 illustrates this. By charging the compressed air accumulator with combustion exhaust gas from the exhaust manifold, exhaust gas energy can be stored in advance and released later to either provide EGR (if released into the intake manifold) or to increase the exhaust gas temperature (if released into the exhaust manifold). By charging the compressed air accumulator with pressurized intake air from the intake manifold, charging energy can be stored in advance and released later to either provide additional boost (if released into the intake manifold) or to increase the exhaust gas temperature (if released into the exhaust manifold). In particular, turbine energy can be increased by raising the exhaust pressure upstream of the turbine. In any case, storing charge in the compressed air accumulator for later use can improve the performance of a turbocharged engine.

[0034] Step 202 of program 200 involves estimating and / or deriving engine operating conditions. These can include, for example, engine speed, torque requirement, boost requirement, exhaust gas temperature, barometric pressure, compressed air storage conditions, etc.

[0035] In one example, the compressed air storage conditions can be estimated using one or more sensors connected to the storage unit, such as pressure, temperature, and air-fuel ratio sensors. In other examples, however, one or more compressed air storage conditions can be derived from or retrieved from a control unit data store instead of being measured directly. For example, if the compressed air storage unit was previously charged with air from the intake manifold, the state of charge in the compressed air storage unit can be derived from the compressor conditions, the intake air temperature and pressure conditions, and the EGR requirement at the time of charging. As another example, if the compressed air storage unit was previously charged with exhaust gas from the exhaust manifold, the state of charge in the compressed air storage unit can be derived from the engine operating conditions, the exhaust gas conditions, and the EGR requirement at the time of charging.Similarly, the duration of the discharge and the charging conditions during the discharge can be used to determine the state of any charge remaining in the compressed air reservoir (if applicable), provided the compressed air reservoir was previously discharged into the intake manifold. Similarly, the duration of the discharge and the engine conditions can be used to determine the state of any charge remaining in the compressed air reservoir (if applicable), provided the compressed air reservoir was previously discharged into the exhaust manifold.

[0036] In step 204, based on the estimated conditions, it can be determined whether an opportunity exists to charge the compressed air reservoir. For example, reservoir charging conditions may exist if the compressed air reservoir is sufficiently empty (e.g., the pressure in the compressed air reservoir is below a threshold). Another example is when the engine is operating with a sufficiently high boost pressure (e.g., with a boost pressure exceeding a threshold). Yet another example is when reservoir charging conditions can be confirmed during engine operation in overrun fuel cut-off. Finally, another example is when reservoir charging conditions can be confirmed during a transition following a tip-out operation.Thus, based on engine operating conditions at the time the charging opportunity is confirmed, it can be determined whether the compressed air reservoir should be charged with compressed air from the intake manifold and / or with combustion exhaust gas from the exhaust manifold. As explained in detail below, the compressed air reservoir can, for example, be selectively charged based on engine speed, vehicle speed, manifold pressure, etc., at the time of the charging opportunity.

[0037] If the charging conditions are confirmed, the compressed air reservoir can be charged in step 206 with compressed intake air from the intake manifold and / or with exhaust gas from the exhaust manifold. Specifically, the reservoir's intake charging valve can be opened for a certain period to charge the reservoir with compressed intake air from the intake manifold, and / or the reservoir's exhaust charging valve can be opened for a certain period to charge the reservoir with exhaust gas from the exhaust manifold. The duration of opening the intake charging valve and / or the exhaust charging valve can be adjusted to fine-tune the composition of the charge stored in the reservoir to provide a desired EGR percentage (or EGR dilution) of the compressed air reservoir charge.In one example, the compressed air reservoir can be charged with air and combustion exhaust gas to provide a charge with a desired EGR percentage and pressure, so that when the pressurized charge is finally released during a subsequent turbocharged engine operation, high-pressure EGR is enabled.

[0038] For example, during a first condition, when tip-in is anticipated at high engine speeds, the compressed air storage tank can be charged exclusively with exhaust gases. In this case, the engine can operate at higher engine speeds with a pedal position close to closed and a vehicle speed exceeding a speed limit, but with an exhaust pressure exceeding a pressure limit. In contrast, during a second condition, when tip-in is anticipated at low engine speeds, the compressed air storage tank can be charged with a combination of intake fresh air and exhaust gases, with the ratio of intake fresh air to exhaust gases adjusted based on a desired compressed air storage EGR percentage. Alternatively, during the second condition, the compressed air storage tank can be charged exclusively with intake fresh air.The engine can operate at lower engine speeds with a pedal position near closed and a vehicle speed below a certain limit, but with an exhaust manifold pressure exceeding a certain pressure limit. For example, the engine can operate with an overpressure in the exhaust manifold from the intake to the exhaust side.

[0039] As in Fig. As explained in section 5, under certain conditions the compressed air accumulator can be charged with an initial quantity of combustion exhaust gas at a lower pressure from the exhaust manifold upstream of the turbine. This initial charge increases the EGR percentage of the accumulator charge, but the stored exhaust gas has a lower pressure. To further increase the pressure of the stored charge, the compressed air accumulator can subsequently be charged with a second quantity of intake fresh air at a higher pressure from the intake manifold downstream of the compressor. This subsequent charge slightly reduces the EGR percentage of the accumulator charge but increases the charge pressure. The initial and second quantities can be adjusted to provide a desired EGR percentage of the pressurized charge.The stored charge can then be advantageously released during selected turbocharged engine conditions to provide the benefits of high-pressure EGR.

[0040] As another example, the compressed air reservoir can be charged with at least some combustion exhaust gas (e.g., exclusively with combustion exhaust gases) during a tip-out at lower engine speeds. In contrast, the control unit can charge the compressed air reservoir with at least some compressed intake air from the intake manifold (e.g., exclusively with compressed intake air) during a tip-out at higher engine speeds. As yet another example, if charging conditions are confirmed during engine operation with fuel cut-off, the reservoir can be charged with unburned exhaust gas released from cylinders with the fuel supply shut off.

[0041] Thus, after charging, the compressed air storage conditions can be updated in the controller's data memory. In one example, the compressed air storage conditions can be updated using one or more sensors connected to the storage tank, such as pressure, temperature, and air-fuel ratio sensors. In other examples, however, the compressed air storage conditions can be derived and updated in the controller's data memory instead of being measured directly. For example, if the compressed air storage tank was recently charged with air from the intake manifold, the charge state of the compressed air storage tank can be derived and updated based on the compressor conditions, intake air temperature, pressure conditions, and the EGR demand at the time of charging.As another example, based on engine operating conditions, exhaust gas conditions and EGR requirements at the time of charging, a state of charge in the compressed air storage tank can be derived and updated if the compressed air storage tank was recently charged with combustion exhaust gas from the exhaust manifold.

[0042] In one example, the EGR percentage of the compressed air storage can be estimated or derived from one or more of the following: an output from an exhaust gas air-fuel ratio sensor, a mass airflow (MAF) sensor, and a fuel injector pulse width. The control system can be designed to estimate a volume of gas stored in the compressed air storage based on the storage pressure. The control system can then estimate, based on changes in the mass airflow after the pressurized charge is released, what proportion of this volume was air, and, based on fuel injection adjustments after the pressurized charge is released, what proportion of this volume contained fuel (e.g., based on a fuel injector pulse width). An estimated air-fuel ratio can then be derived from these air and fuel estimates.In an alternative example, the estimated air-fuel ratio can be based on the output of a lambda sensor. The estimated air-fuel ratio can then be compared to a measured air-fuel ratio to record any deviation. This deviation can then be used to update an estimate of the EGR percentage of the compressed air charge. The stored compressed air conditions can be retrieved by the control unit during a subsequent venting operation. It is understood that in all cases, charging can be performed during an engine cycle preceding a tip-in operation in which the pressurized charge is vented.

[0043] In this way, the compressed air storage tank can be selectively charged with fresh air drawn in from an intake manifold and / or exhaust gas from an exhaust manifold. Charging with fresh air and exhaust gas can be implemented to allow the storage of a compressed air tank charge with a selected EGR percentage. As shown here, Fig. As explained in section 3, after selective charging, for example in response to a tip-in, the pressurized charge from the compressed air reservoir can be released into the intake manifold and / or the exhaust manifold based on engine operating conditions at the time of the tip-in, in order to reduce turbo lag and improve the performance of the turbocharged engine.

[0044] Now, with reference to Fig. 3 is an example program 300 for draining the compressed air reservoir of Fig. Figure 1 illustrates this. By releasing compressed air into the intake or exhaust manifold, based at least on a specific charge composition within the compressed air reservoir, the compressed air charge can be advantageously used to increase the exhaust gas temperature or exhaust gas pressure. In any case, releasing compressed air from the reservoir in response to a tip-in can reduce turbo lag and improve the performance of the turbocharged engine.

[0045] In step 302, the engine operating conditions can be estimated and / or derived. These may include, for example, engine speed, torque demand, boost requirement, exhaust gas temperature, barometric pressure, compressed air storage conditions, etc. In step 304, the details of the compressed air storage charge can be retrieved. The pressurized charge may itself contain a variable mixture of combustion exhaust gas and compressed intake air, thus exhibiting a specific charge pressure and a specific charge-to-EGR percentage (or a specific EGR dilution). The retrieved details may include, for example, a charge composition that includes a fresh air content of the charge as well as a combustion exhaust gas content of the charge. The retrieved details may further include the charge temperature, charge pressure, charge-to-EGR percentage, etc.As previously explained, the compressed air storage details can be stored in the controller's data memory and can be derived and updated after each charging cycle. Furthermore, after each charging cycle, the compressed air storage details can be updated to reflect the most recent state of the charge remaining in the compressed air storage (if applicable).

[0046] In step 306, a tip-in can be confirmed. For example, a tip-in might be confirmed in response to the accelerator pedal being moved beyond a limit position and the torque demand exceeding a limit. If no tip-in is confirmed, the program can terminate. Upon confirmation of a tip-in, step 308 of the program determines whether the pressurized charge should be released into the intake or exhaust manifold.

[0047] In one example, the choice (whether to vent to the intake or exhaust manifold) can be based on the composition (or EGR percentage) of the charge stored in the compressed air accumulator. For instance, if the compressed air accumulator has a high fresh air content (e.g., if the fresh air percentage of the stored charge is higher than a threshold) or a low EGR content (e.g., if the EGR percentage of the stored charge is lower than a threshold), the charge air can be vented to the intake manifold to provide increased torque to alleviate turbo lag as the turbine spools up. As another example, if the compressed air accumulator has a low fresh air content (e.g., if the fresh air percentage of the stored charge is lower than a threshold) or a high EGR content (e.g., if the EGR percentage of the stored charge is lower than a threshold), the charge air can be vented to the intake manifold to provide increased torque to counteract turbo lag while the turbine spins up.(If the EGR percentage of the stored charge is higher than a certain threshold), the charge air is applied to the exhaust manifold to extract energy from the compressed air charge and use it to accelerate the turbine's spin-up. Thus, during a first tip-in, when the discharged charge has a lower EGR percentage, it is discharged into the intake manifold, whereas during a second tip-in, when the discharged charge has a higher EGR percentage, it is discharged into the exhaust manifold.

[0048] In yet another example, the choice of whether to release the compressed air into the intake manifold or the exhaust manifold can be based on the charge pressure of the pressurized charge stored in the accumulator. For instance, if the charge pressure of the compressed air accumulator is higher than a threshold pressure, the higher-pressure charge can be selectively released into the intake manifold to quickly raise the exhaust gas temperature and reduce turbo lag. In an alternative example, if the charge pressure of the compressed air accumulator is lower than the threshold pressure, the lower-pressure charge can be selectively released into the exhaust manifold to quickly raise the exhaust pressure and reduce turbo lag.

[0049] In another example, the choice can be based on the boost pressure at the time of tip-in. For instance, if the boost pressure at tip-in is higher than a threshold boost pressure, the compressed air charge can be vented into the intake manifold. Conversely, if the boost pressure at tip-in is lower than a threshold boost pressure, the compressed air charge can be vented into the exhaust manifold. In an alternative example, the engine boost pressure at a first tip-in, where the pressurized charge is vented into the intake manifold, can be lower than the engine boost pressure at a second tip-in, where the pressurized charge is vented into the exhaust manifold.In further embodiments, the choice of whether the compressed air charge should be released into the intake manifold or the exhaust manifold can be based on other engine operating conditions such as engine speed, exhaust gas temperature and the air-fuel ratio in the exhaust gas, etc.

[0050] As another example, the selection can also be based on an EGR demand at the time of tip-in. For instance, the compressed air accumulator can be charged with combustion exhaust gas and compressed intake air in such a way that a charge with a defined charge pressure and a defined charge-EGR percentage is stored. If the charge strength during tip-in is then lower than the charge pressure of the compressed air accumulator, the pressurized charge can be released into the intake manifold if EGR is required, and into the exhaust manifold if no EGR is required. Conversely, if the charge strength during tip-in is higher than the charge pressure of the compressed air accumulator, the pressurized charge can be released exclusively into the exhaust manifold.

[0051] It is understood that while the depicted program suggests venting during a tip-in either into the intake manifold or the exhaust manifold, in some embodiments the pressurized charge can be vented into both the intake and exhaust manifolds during a given tip-in. Specifically, in these embodiments, the pressurized charge can be vented sequentially into both the intake and exhaust manifolds during the same tip-in. Accordingly, it can be determined before venting whether the pressurized charge should be vented first into the intake manifold and then into the exhaust manifold, or whether the pressurized charge should be vented first into the exhaust manifold and then into the intake manifold. In one example, the sequence of venting could be based on the boost pressure, the exhaust pressure, and the compressed air storage pressure.

[0052] In step 310, you can confirm whether the compressed air charge should be vented into the intake manifold (e.g., whether the compressed air charge should be vented only into the intake manifold or first into the intake manifold). If so, the program in step 312 involves venting pressurized charge from the compressed air reservoir into the intake manifold. Specifically, into the intake manifold downstream of a turbocharger compressor and downstream of an intake throttle valve. Furthermore, during the venting process, the ignition timing can be retarded based on the amount of pressurized charge vented from the compressed air reservoir. However, the applied ignition retard can be less than a threshold value based on a combustion torque corresponding to the amount of pressurized air vented.This means that the ignition cannot be delayed by an amount that reduces the net combustion torque. For example, the ignition delay can maintain the torque or increase it beyond the torque level that would be generated during cylinder operation without additional pressurized air released from the compressed air reservoir. This allows for an increase, or at least the maintenance, of the engine's net combustion torque during the ignition timing delay.

[0053] In one example, venting into the intake manifold can occur outside of valve overlap. For instance, venting can take place during an intake stroke and / or a compression stroke, but not during portions of these strokes where both the intake and exhaust valves are open simultaneously. This allows the air-fuel mixture to combust in the cylinder in such a way that the heated exhaust gas, after being released, can be used to drive the turbine in a subsequent combustion cycle. By venting the pressurized gas outside of the overlap period, rather than during it, greater air-fuel mixing and improved exhaust gas heating can be achieved. In an alternative example, however, venting into the intake manifold can occur during valve overlap.For example, the timing of the air release can be adjusted to coincide with positive valve overlap. Alternatively, the camshaft timing of a variable camshaft timing mechanism can be adjusted based on the air release to provide high valve overlap when the compressed air reservoir is released. After the release, the camshaft timing of a variable camshaft timing mechanism can then be reset based on the engine operating conditions.

[0054] In one embodiment, based on Fig. As explained in section 4, a portion of the pressurized charge from the compressed air reservoir can be released downstream of an intake throttle valve into the intake manifold while the intake throttle valve is held closed (or while the throttle valve is being adjusted closer to a closed position). Then, any remaining pressurized charge can be released after the throttle valve is opened. As in the example of Fig. As explained in section 8, the throttle valve can be kept closed until a limiting intake pressure is generated upstream of the throttle valve by the compressor. By keeping the throttle valve closed, the boost pressure generated at the compressor can be increased more quickly than would otherwise be possible with an open throttle valve. Simultaneously, the torque demand can be met, and the turbine's spool-up can be accelerated by releasing pressurized charge into the intake manifold.

[0055] In step 314, during the exhaust process, the amount of exhaust gas recirculated from the exhaust manifold to the intake manifold can be reduced. Specifically, reducing the EGR can be based on the amount of pressurized air released. This allows for improved combustion stability and the use of increased ignition retardation for exhaust gas heating. For example, where the engine system has an EGR line with an EGR valve to recirculate exhaust gas from the engine exhaust manifold to the engine intake manifold, an engine control unit can reduce the opening of the EGR valve to decrease the amount of exhaust gas recirculated to the intake side via the EGR line.

[0056] In step 316, it can be determined whether the exhaust gas temperature (Texh) exceeds a limit. This limit can correspond to a temperature above which the turbine can be rotated and spun up, thus driving the compressor and providing the desired boost. For example, the limit can be based on a turbine speed. In this way, if the exhaust gas temperature is above the limit, the release of pressurized charge from the compressed air reservoir into the intake manifold can be suspended in step 318. Additionally, in step 330, the turbine can be spun and the turbocharger compressor operated to provide the boost required to meet the torque demand.If the exhaust gas limit temperature has not been reached in step 316, the release of pressurized charge into the intake manifold continues during the ignition delay until the exhaust gas temperature exceeds the limit temperature.

[0057] If, in step 310, the release of the compressed air charge into the intake manifold is not confirmed, step 320 can confirm whether the compressed air charge should be released into the exhaust manifold (e.g., whether the compressed air charge should be released exclusively into the exhaust manifold or first into the exhaust manifold). If so, in step 322, the program includes releasing pressurized charge from the compressed air reservoir into the exhaust manifold, while cylinder fuel injection (including fuel injection quantity and / or timing) is adjusted during the release process based on the released pressurized charge so that the overall exhaust air-fuel ratio (e.g., the exhaust air-fuel ratio measured at a catalytic converter) is stoichiometric or approximately stoichiometric.In the context of this document, venting pressurized charge into the exhaust manifold involves venting it upstream of a turbocharger turbine. For example, this venting can be performed while the engine is running under boost.

[0058] In some embodiments, simultaneous throttle valve adjustment can be performed to compensate for the increased exhaust pressure, thereby reducing the amount of air that can be drawn into the engine's intake manifold and thus the range of torque delivered. For example, the throttle valve opening can be increased simultaneously to increase the intake air and the torque output from the engine.

[0059] Adjusting the cylinder fuel injection during the discharge into the exhaust manifold can involve, for example, performing a rich fuel injection and / or a late fuel injection, based on the quantity and air-fuel ratio of the pressurized charge. By delaying and / or enriching the fuel injection to match the (fresh) air component of the charge delivered from the compressed air reservoir into the exhaust manifold, the overall exhaust mixture (e.g., at a downstream catalytic converter) can be kept essentially stoichiometric. Furthermore, the exothermic reaction of the additional oxygen from the air in the compressed air reservoir with the rich fuel injection generates additional exhaust heat and boost pressure, which also contributes to reducing turbo lag.In one example, rich fuel injection can be implemented when the exhaust gas temperature exceeds a threshold temperature to better ensure that the exothermic reaction occurs as desired in the exhaust manifold and not further downstream. Fuel injection can also be adjusted using feedback from one or more air-fuel sensors, such as those located upstream and / or downstream of the turbine and the catalytic converter in the exhaust manifold. However, the mixing of air and fuel can be problematic when relying solely on feedback from an upstream air-fuel sensor.In some embodiments, during the draining process, the cylinder fuel injection can be adjusted based on feedback from an exhaust-air-fuel sensor located downstream of the turbocharger turbine in the exhaust manifold to allow the reception of more reliable feedback signals.

[0060] Then, in step 324, it can be determined whether the exhaust gas pressure (Pexh) upstream of the turbine exceeds a limit value. This exhaust gas limit pressure can correspond to a pressure above which the turbine can be rotated and spun up, thus driving the compressor and providing the desired boost. For example, the limit pressure can be based on a turbine speed. In this way, if the exhaust gas pressure exceeds the limit pressure, the release of pressurized charge from the compressed air reservoir can be suspended in step 328. Additionally, in step 330, the turbine can be spun and the turbocharger compressor operated to provide the required boost level to meet the torque demand.If the exhaust gas limit pressure has not been reached in step 324, the discharge of pressurized charge into the exhaust manifold continues, while cylinder fuel injection is delayed and / or enriched until the exhaust gas pressure exceeds the limit pressure.

[0061] It is understood that while the depicted program illustrates the venting into the exhaust manifold until a limiting exhaust pressure is reached, in alternative examples the control system may be designed to continue venting into the exhaust manifold until the turbine speed reaches a limiting speed or until the intake boost pressure (e.g., at the supercharger) reaches a limiting boost pressure. For example, venting into the exhaust manifold can occur while there is a pressure boost condition from the intake manifold to the exhaust manifold. If the manifold pressure reaches a limiting pressure and the pressure boost condition no longer exists, venting into the exhaust manifold is stopped. That is, an engine control system can be designed to vent into the exhaust manifold until the turbine speed reaches a limiting speed or until the intake boost pressure reaches a limiting boost pressure.

[0062] In this way, a compressed air reservoir can be charged with at least some exhaust gas from the exhaust manifold during an engine cycle preceding a tip-in. Then, in response to a tip-in, turbo lag can be reduced by releasing pressurized charge from the compressed air reservoir into the exhaust manifold. An example of engine operation involving the release of a compressed air reservoir charge into an exhaust manifold is described here using the following examples: Fig. 6 explained.

[0063] It is understood that in some examples, the pressurized charge can be released into both the intake and exhaust manifolds during the same tip-in. Specifically, during a single tip-in, a portion (e.g., an initial quantity) of the pressurized charge stored in the compressed air reservoir can be released into the exhaust manifold, while the remaining portion (e.g., a second, different quantity) of the stored charge is subsequently released into the intake manifold. In this case, the control system can decide, based on the same considerations described above, whether to release into the intake manifold or the exhaust manifold first. Thus, in one example, if the compressed air reservoir pressure is higher, a portion of the pressurized charge can be released into the intake manifold first, and then the remaining portion can be released into the exhaust manifold later.In an alternative example, if the pressurized charge has a higher EGR content, part of the pressurized charge can first be released into the exhaust manifold and then the remaining part can be released into the intake manifold later.

[0064] By releasing air into both the intake manifold and the exhaust manifold during the same tip-in, it is possible to balance the competing objectives of mixing air and fuel, quickly revving up, and having a sufficient duration of increased output from the compressed air reservoir to essentially fill in all the delay caused by turbo lag.

[0065] It is understood that a tip-out following a tip-in can provide an opportunity to recharge the compressed air reservoir. For example, during the tip-out, the engine control unit can selectively charge the compressed air reservoir with intake air from the intake manifold or with combustion exhaust gas from the exhaust manifold, the selection being based on the reservoir's composition at the time of the tip-out. The selection can further be based on the engine speed and vehicle speed at the time of the tip-out, as is already the case for Fig. 2 was explained.

[0066] In this way, during the first tip-in, pressurized charge is released from a compressed air reservoir into an intake manifold, whereas during a second tip-in, pressurized charge is released from the compressed air reservoir into an exhaust manifold. By releasing pressurized charge from the compressed air reservoir into the intake manifold under some conditions and into the exhaust manifold under other conditions, the benefits of using a pressurized charge stored in a compressed air reservoir can be extended. Specifically, pressurized intake air can be better used to reduce turbo lag while also satisfying an intermediate torque demand. Similarly, pressurized exhaust gas can be better used to reduce turbo lag while also satisfying EGR requirements. Overall, the performance of the turbocharged engine can be improved.

[0067] In Fig. Figure 4 now presents an exemplary program 400 for releasing pressurized charge from a compressed air reservoir into an intake manifold while controlling an intake throttle valve. By releasing a portion of the pressurized charge into the intake manifold with the intake throttle valve closed, boost pressure or throttle valve intake pressure can be quickly increased, enabling the compressor to be "pre-charged" before the charge is released into the intake manifold. Meanwhile, a torque requirement can be met by releasing pressurized charge from the compressed air reservoir downstream of the throttle valve. In an example, the program can be... Fig. 4 as part of the program of Fig. 3, for example, in step 312.

[0068] In step 402, program 400 includes confirmation that the pressurized charge from the compressed air reservoir should be released into the intake manifold. If not, the program can terminate. For example, pressurized charge can be released into the intake manifold in response to a tip-in during turbocharged engine operation. During the tip-in, the throttle valve intake pressure (TIP), estimated upstream of an intake throttle valve, may fall below a certain threshold. The compressed air reservoir itself may have been charged with compressed air from the intake manifold and / or exhaust gas from the exhaust manifold during an engine cycle preceding the tip-in, in order to store pressurized charge with a defined EGR percentage and charge pressure.

[0069] After confirmation, in step 404, the program includes opening the compressed air reservoir intake vent valve while the intake throttle valve is closed. The control unit can then vent the pressurized charge from the compressed air reservoir into the intake manifold, downstream of the intake throttle valve, while keeping the intake throttle valve closed. Venting the pressurized charge into the intake manifold can involve opening the compressed air reservoir intake vent valve while keeping the reservoir intake charge valve closed.

[0070] In step 406, the program involves operating the compressor while monitoring a throttle intake pressure (TIP), which also indicates the boost pressure generated at the compressor while the throttle is closed. In one example, the TIP can be estimated from a pressure sensor located in the intake manifold downstream of the compressor and upstream of the intake throttle. As the turbine gradually spins up, the compressor pressure also gradually increases, and consequently, so does the TIP. Holding the throttle closed can accelerate the rise in boost pressure or TIP. As a result, until the throttle is opened, the compressor can generate and store a sufficient quantity of pressurized charge air, or pre-charge it upstream of the throttle.This boost pressure can then be released into the intake manifold as soon as the throttle valve is opened.

[0071] Thus, the venting of pressurized charge into the intake manifold can continue while the intake throttle valve is held closed for a period of time until the throttle valve intake pressure reaches or exceeds the limit. Alternatively, the venting can continue with the throttle valve held closed for a period of time until the manifold manifold pressure (MAP) downstream of the throttle valve equals the throttle valve intake pressure upstream of the throttle valve.

[0072] Step 408 determines whether the estimated TIP is higher than the limit. For example, the limit might be based on a desired boost level or boost pressure. If the TIP reaches the desired boost level before the compressed air reservoir is completely discharged (or at the time the compressed air reservoir is completely discharged), the program in step 412, after the specified time has elapsed, closes the intake bleed valve while opening the throttle valve from the closed position. Opening the intake throttle valve allows pressurized air, which was stored and pre-charged upstream of the throttle valve, to be discharged from the compressor downstream into the intake manifold. That is, compressed air can be drawn from the compressor into the intake manifold when the throttle valve is open.Introducing compressed air into the intake manifold with the throttle valve open essentially prevents the release of pressurized air into the manifold. In this case, both the accumulator charge valve and the exhaust valve can remain closed.

[0073] The compressed air reservoir can even be emptied before the TIP reaches the limit. This allows the program to determine in step 410 whether the compressed air reservoir has been completely emptied if the TIP is not above the limit. If so, the program proceeds to step 412 to close the extraction valve and open the throttle valve, allowing the pressurized air charge from the compressor to be released into the intake manifold.

[0074] The control system can further be designed to adjust the ignition timing while the pressurized charge is being vented into the intake manifold and while compressed air is being drawn into the intake manifold. For example, the ignition timing can be adjusted to a first pulse during venting while the intake throttle is closed, whereas the ignition timing is adjusted to a second, different pulse during the intake of compressed air with the throttle open. The first pulse can be based on the quantity and EGR percentage of the vented pressurized charge. Similarly, the second pulse can be based on the quantity and pressure of compressed air being drawn into the intake manifold. The second pulse can also be based on the EGR percentage of the drawn compressed air if EGR (e.g.,a high-pressure EGR or a low-pressure EGR via appropriate EGR lines) is carried out, while compressed air from the compressor is fed into the intake manifold.

[0075] In this way, during a tip-in, while a compressor is running, cylinder pressure can be increased by venting pressurized charge from a compressed air reservoir into an intake manifold while an intake throttle valve remains closed. Cylinder pressure can then be further increased during tip-in by introducing compressed air from the compressor into the intake manifold while the closed throttle valve opens. By venting pressurized charge from a compressed air reservoir with the intake throttle valve closed, the released charge can be used to accelerate turbine spool-up and reduce turbo lag, while also meeting engine torque demands during turbo lag. By keeping the intake throttle valve closed for a period of time while the turbine spools up, the pressure of air compressed by the compressor can be rapidly increased.Furthermore, higher boost pressures can be achieved. By releasing the pressurized charge into the intake manifold after the throttle valve has opened, boosting benefits can be realized. Overall, turbo lag is reduced while boosting performance is improved. An exemplary engine operation, in which pressurized charge is released from a compressed air reservoir into the intake manifold while the throttle valve is closed for a period of time, is described here using [reference to relevant example]. Fig. 8 explained.

[0076] In Fig. 5 An exemplary program 500 for charging a compressed air storage tank with combustion exhaust gases and pressurized fresh air is now described in order to generate a pressurized EGR mixture which can then be released into the intake manifold during charged conditions to enable the achievement of the benefits of high-pressure EGR.

[0077] In step 502, engine operating conditions can be estimated and / or derived. In step 504, it can be confirmed that the engine is supercharged, but with a boost level that is lower than a threshold level. For example, it can be confirmed that the boost level is above a lower threshold but below an upper threshold. If not, the program can terminate. After confirmation, in step 506, during low-boost conditions, the program charges the compressed air reservoir with at least some exhaust gas up to a first lower pressure. For example, the compressed air reservoir can be charged exclusively with exhaust gases from the exhaust manifold by opening the compressed air reservoir exhaust charging valve (for a period of time). Alternatively, the reservoir can be charged with exhaust gas from the exhaust manifold and fresh air drawn in from the intake manifold.In the context of this document, charging with combustion exhaust gas involves charging with one or more of the following: low-pressure EGR, high-pressure EGR, and combustion exhaust gas received directly from the exhaust manifold via a valve. Charging the accumulator with combustion exhaust gas involves the selective opening of a first valve connected between the compressed air accumulator and the exhaust manifold. After charging, the pressurized charge in the compressed air accumulator can have a defined EGR percentage (that is, the accumulator can be charged with a ratio of intake air to combustion exhaust gas that must provide the desired EGR percentage of the compressed air accumulator) and can have a first, lower pressure.

[0078] In step 508, after the compressed air reservoir has finished charging, it can be determined whether increased boost is required. For example, increased boost might be requested in response to a further tip-in while the engine is already boosted. In response to the tip-in, the boost can be increased in step 510. For example, the compressor speed could be increased. In step 512, it can be confirmed that the boost has been increased and the boost level is now higher than the threshold. After confirmation, during high-boost conditions, in step 514, the compressed air reservoir can be further charged with compressed intake gas to raise the pressure of the stored charge to a second, higher pressure.Further charging with compressed intake air involves the selective opening of a second valve connected between the compressed air reservoir and the intake manifold, with the second valve being located downstream of the intake throttle valve. By mixing the combustion exhaust gases, stored at a lower pressure in the reservoir, with the higher-pressure compressed intake air, a high-pressure EGR mixture can be generated in situ and stored in the compressed air reservoir for later release when high-pressure EGR is required. In another example, the valve can be located upstream of the throttle valve.

[0079] Step 516 determines whether a temporary increase in EGR is requested. In another example, the temporary increase in EGR might be requested later during engine operation if the boost level is below the threshold (e.g., below the second pressure) and the operator initiates a tip-in. For instance, while the engine is boosted, a tip-in towards full load might be received. As a result, a temporary increase in EGR might be required. In response to the requested temporary increase in EGR, the program in step 518 involves venting pressurized charge from the compressed air reservoir into an engine manifold (e.g., venting into an intake or exhaust manifold). For example, venting into the intake manifold involves venting downstream of a turbocharger compressor and downstream of an intake throttle valve.In this way, high-pressure EGR can be achieved by releasing the pre-stored high-pressure EGR from the compressed air reservoir into the intake manifold in response to a temporary demand for increased EGR. Specifically, the control system can selectively open a third valve, located downstream of the intake throttle valve between the compressed air reservoir and the intake manifold (i.e., the compressed air reservoir intake discharge valve), and release the pressurized charge from the compressed air reservoir downstream of the intake throttle valve into the intake manifold. In one embodiment, the intake throttle valve can be temporarily held closed while the high-pressure EGR is being released from the compressed air reservoir. In another example, the release can continue until the boost pressure equals the compressed air reservoir pressure; thereafter, the release can be stopped.For example, the venting can continue until the boost pressure equals the second pressure.

[0080] The inventors recognized that during turbocharging, when temporary EGR is required, the requested EGR may not always be available as quickly as needed. Specifically, recirculated exhaust gas may not be immediately available via low-pressure EGR due to its slower response time. Simultaneously, recirculated exhaust gas may also not be immediately available via conventional high-pressure EGR due to the pressure differential between the intake and exhaust manifolds, which would cause the high-pressure EGR to flow back into the exhaust manifold. To overcome these problems and still achieve the benefits of high-pressure EGR, the exhaust gas pressure in the accumulator can be increased by mixing it with a quantity of compressed intake air before it is released.This allows high-pressure EGR to be provided in response to a tip-in, even when the boost pressure is already high. An exemplary engine operation, in which a compressed air reservoir is charged with high-pressure EGR and the high-pressure EGR is discharged into the intake manifold during a temporary EGR request, is described here using [reference to relevant example]. Fig. 7 explained.

[0081] In Fig. Figure 6 now shows map 600, illustrating an example of engine operation in which turbo lag is reduced by releasing pressurized charge into an exhaust manifold in response to a tip-in. Specifically, map 600 shows a change in pedal position (PP) in curve 602, a change in boost pressure in curve 604, the opening or closing of a compressed air storage exhaust valve (storage valve_exhaust) in curve 606, a change in exhaust pressure in curve 608, and a change in the cylinder air-fuel ratio (cylinder AFR) relative to the stoichiometry in curve 612.For example, the boost pressure can be estimated with a pressure sensor located downstream of the compressor of a turbocharger in the intake manifold, the exhaust pressure can be estimated with a pressure sensor located upstream of the turbine in the exhaust manifold, and the cylinder-air-fuel ratio can be estimated with an air-fuel sensor connected to an exhaust catalyst in the exhaust manifold.

[0082] Before t1, the engine can operate with low boost pressure. For example, the engine can run without boost or with a low boost level. At t1, a tip-in is confirmed, as indicated by the change in pedal position (curve 602). A control system can be designed to release charge, which includes air and combustion exhaust gas, from a compressed air reservoir into the exhaust manifold, upstream of a turbine, in response to the tip-in, in order to reduce turbo lag. Specifically, a compressed air reservoir exhaust relief valve can be opened for a period of time between t1 and t2 (curve 606).

[0083] As in Fig. As explained in section 1, the compressed air reservoir can be connected to the exhaust manifold via a first exhaust charge valve and a second exhaust discharge valve. Accordingly, releasing charge from the reservoir into the exhaust manifold involves opening the second (exhaust discharge) valve while keeping the first (exhaust charge) valve closed. The compressed air reservoir itself may have been charged with compressed air from the intake manifold and / or with combustion exhaust from the exhaust manifold during a charging event prior to tip-in. When charging the reservoir with combustion exhaust from the exhaust manifold, the second valve may have been opened while the first valve remained closed. When charging the reservoir with compressed intake air from the intake manifold, a reservoir intake charge valve may have been opened while an intake discharge valve remained closed.

[0084] In response to the release of pressurized charge from the compressed air reservoir into the exhaust manifold at t1, the exhaust pressure (curve 608) can begin to rise. This release of pressurized charge from the reservoir into the exhaust manifold in response to the tip-in allows the exhaust pressure to rise more rapidly upstream of the turbine than would otherwise be possible. This rapid increase in exhaust pressure enables the turbine to spin up more quickly. This, in turn, reduces turbo lag and allows for a rapid increase in boost pressure at the compressor (curve 604). In contrast, curve 609 (dashed line) represents a slower increase in exhaust pressure, which would be expected if no pressurized charge were released from a compressed air reservoir into the exhaust manifold.Due to the slower increase in exhaust pressure, the turbine's spool-up can be delayed, resulting in turbo lag, which is reflected in the slower rise in boost pressure (at the compressor), as shown in curve 605 (dashed line). It is understood that in both cases, the exhaust pressure is raised to the same level (see curves 608 and 609) and the boost pressure is also raised to the same level (see curves 604 and 605), but at different rates. However, by diverting pressurized charge into the exhaust manifold, the turbine rotation is accelerated, turbo lag is reduced, and boost pressures are reached quickly. This allows for improved performance of the turbocharged engine.

[0085] During venting into the exhaust manifold and / or later (not shown), the engine control unit can adjust fuel injection to be richer (as illustrated by the enrichment of the cylinder AFR in curve 612). This richness and retardation of fuel injection can be based on the (vented) pressurized charge, so that at an exhaust catalyst, an exhaust-air-fuel ratio is maintained that is essentially stoichiometric or approximately stoichiometric (615). Specifically, the richness and retardation of the cylinder fuel injection can be adjusted to match the compressed fresh air component of the charge being directed from the compressed air reservoir into the exhaust manifold, so that at the exhaust (i.e.,The overall mixture (measured downstream of the turbine and downstream of an exhaust catalyst in the exhaust manifold) is kept essentially stoichiometric or approximately stoichiometric. Furthermore, the reaction of the additional oxygen in the air component of the compressed air charge with the rich fuel injection generates additional exhaust heat, which further aids the acceleration of the turbine's spool-up and the reduction of turbo lag. For example, cylinder fuel injection can be adjusted based on AFR feedback from one or more air-fuel ratio (or oxygen) sensors located downstream of the turbine and the exhaust catalyst in the exhaust manifold. In still other examples, fuel injection can be adjusted based on AFR feedback from an oxygen sensor located upstream of the turbine in the exhaust manifold.

[0086] As explained above, the richness of the fuel injection (that is, the cylinder AFR shown in curve 612) can vary based on the amount of pressurized charge released from the reservoir (or the rate of discharge) and the EGR percentage of the discharged pressurized charge. Thus, with a decreasing EGR percentage of the pressurized reservoir charge (that is, a higher ratio of intake fresh air to exhaust gas in the charge), a richer cylinder fuel injection may be required (as shown in curve 612, solid line).In comparison, as the EGR percentage of the compressed air storage charge increases (i.e., there is an increasing ratio of aspirated fresh air to combustion exhaust gas in the charge), the richness of the fuel injection can be progressively reduced (as shown in curve 613 (dashed line) and curve 614 (dotted line)).

[0087] Between t1 and t2, while the pressurized charge is vented from the compressed air reservoir into the exhaust manifold and the exhaust pressure increases upstream of the turbine, the venting rate from the reservoir to the exhaust manifold decreases. This means that when the exhaust vent valve first opens at t1, pressurized charge can be vented into the exhaust manifold at a faster rate. During this faster venting rate, when a larger quantity of charge is vented into the exhaust manifold, the richness of the fuel injection can be relatively higher. As time t2 approaches, the exhaust pressure (curve 608) begins to approach the limit pressure 610, and pressurized charge can be vented into the exhaust manifold at a slower rate.During this slower exhaust rate, when a smaller amount of charge is discharged into the exhaust manifold, the richness of the fuel injection can therefore be relatively lower. Specifically, a gradual reduction in the richness (and / or delay) of the fuel injection occurs, as illustrated by the gradual reduction of the cylinder AFR richness towards stoichiometry 615.

[0088] The discharge from the accumulator into the exhaust manifold continues for a time period d1 (between t1 and t2) until the exhaust pressure upstream of the turbine equals the limit pressure 610. At t2, when the exhaust pressure upstream of the turbine reaches the limit pressure 610, the compressed air accumulator exhaust valve can be closed (curve 606). The limit pressure 610 can be based on the compressed air accumulator pressure (not shown). During discharge, the exhaust pressure increases and the compressed air accumulator pressure decreases. If the exhaust pressure and the compressed air accumulator pressure are equal, further flow may not be possible, and no further benefits of compressed air accumulator charging can be achieved.Thus, the limit pressure 610 can be based on a projected rate of pressure drop in the compressed air storage tank and include a differential, so that the exhaust gas relief valve closes before the exhaust gas pressure reaches the compressed air storage tank pressure. This means that to maximize the benefits of the compressed air storage tank charging, the exhaust gas relief valve can be closed before the tank is empty and as long as the compressed air storage tank pressure is still higher than the exhaust gas pressure.

[0089] Up until the point at which the compressed air storage exhaust valve closes at t2, the exhaust pressure may be sufficiently high (e.g., higher than the limit of 610) and the turbine may have already spooled up. As a result, the compressor boost pressure may also be sufficiently high. This means that turbo lag may have been reduced. Consequently, after t2, the engine torque demand can be met by the turbocharger's compressor.

[0090] In Fig. Figure 7 now presents map 700 as an example of engine operation in which a compressed air accumulator is charged with high-pressure EGR and then the high-pressure EGR is released into the intake manifold during a temporary demand for increased EGR. Specifically, map 700 shows a change in exhaust pressure in curve 702, a change in boost pressure in curve 704, the opening or closing state of a compressed air accumulator exhaust charging valve (Storage_Abg) in curve 707, the opening or closing state of a compressed air accumulator intake charging and draining valve (Storage_Ans) in curves 708-709, a change in the EGR percentage in the compressed air accumulator in curve 710, and a change in boost pressure in curve 712.For example, boost pressure can be estimated using a pressure sensor located downstream of the compressor of a turbocharger in the intake manifold, exhaust pressure can be estimated using a pressure sensor located upstream of the turbine in the exhaust manifold, and compressed air storage pressure can be estimated using a pressure sensor connected to the compressed air storage tank. The EGR percentage in the compressed air storage tank can be estimated using appropriate sensors or derived based on engine operating conditions at the time of charging and discharging the tank.

[0091] Before t1, the engine can operate at a low boost pressure. For example, the engine can operate without boost or with a low boost level. At t1, the boost level can be increased (curve 712), for example, in response to a tip-in, but can remain below a limit level 713. After t1, during a first engine cycle in which the engine is boosted, but the boost level is lower than the limit level 713, the compressed air reservoir can be charged with at least some exhaust gas from the exhaust manifold to an initial pressure 705 (curve 704). In particular, a compressed air reservoir exhaust gas charging valve can be opened for a period between t1 and t2 (curve 707). As a result of the compressed air reservoir being charged with exhaust gas from the exhaust manifold, the EGR percentage of the reservoir charge can increase (curve 710).

[0092] At t2, during a second, later engine cycle, when the boost pressure is higher than the limit value 713 (curve 712), the compressed air reservoir can be further charged with compressed intake air to a second, higher pressure 706. Specifically, a compressed air reservoir intake charging valve can be opened for a period between t2 and t3 (curve 708). Since boost pressure is used to further charge the reservoir, the boost pressure downstream of the compressor can decrease (curve 712). As a result of charging the compressed air reservoir with compressed intake air from the intake manifold, the EGR percentage of the reservoir charge can decrease slightly (curve 710). However, this slight decrease in the EGR percentage is considered acceptable given the significant increase in pressure. Thus, at t2, a high-pressure mixture of exhaust gas and compressed air can be generated and stored in the compressed air reservoir.This can in itself provide a source of high-pressure EGR, which can be advantageously used to satisfy a temporary EGR demand while the engine is in turbocharged operation.

[0093] In this way, a control unit can actuate a turbocharger to provide engine boost. If the engine boost is then lower than a certain threshold, the control unit can charge the accumulator with at least some exhaust gas from the exhaust manifold to a first pressure. Furthermore, if the engine boost is higher than the threshold, the control unit can charge the accumulator with at least some compressed intake air from the intake manifold to a second, higher pressure. As a result, a high-pressure EGR mixture is stored in the compressed air accumulator. Specifically, even if the exhaust pressure is otherwise not high enough to charge the accumulator to a sufficient pressure for subsequent release into the engine's intake tract during turbocharged engine operation, the addition of higher-pressure intake gases can raise the pressure and thus allow at least some exhaust gas to be released into the intake tract, even when the engine is heavily boosted.

[0094] At a later time (t4), for example, during a third engine cycle following the second, a temporary request for increased EGR may be received. In response to this request, the pressurized charge at the second, higher pressure 706 from the compressed air reservoir can be released into the intake manifold. Specifically, a compressed air reservoir intake release valve can be opened for a period between t4 and t5 (curve 709, dashed line). The release during the third engine cycle can be performed, for example, in response to a tip-in event received during supercharged engine operation, or in response to an EGR request received during supercharged engine operation. During the third engine cycle, the boost pressure itself is lower than the second pressure of the compressed air reservoir.This means that the boost pressure may not be higher than the pressure of the charge (in this case, the high-pressure EGR) that was previously stored in the compressed air reservoir. By releasing high-pressure EGR into the engine's intake manifold, a high-pressure EGR can be quickly provided via a compressed air reservoir to improve combustion control and reduce NOₓ. x -to reduce emissions. Specifically, EGR can be provided during turbocharged engine operation when neither conventional high-pressure EGR nor conventional low-pressure EGR can be delivered to the engine quickly and reliably.

[0095] It is understood that while the preceding example represents the pre-storage of high-pressure EGR and then the provision of high-pressure EGR in response to a temporary demand for increased EGR, the engine control unit can be configured to provide low-pressure EGR as well. In this case, exhaust gas can be recirculated via an EGR line containing an EGR valve, with the EGR line being connected between the intake and exhaust manifolds of the engine. Specifically, during a given engine cycle, the control unit can open the EGR valve of the EGR line to recirculate exhaust gas from the exhaust manifold into the intake manifold (as opposed to recirculating high-pressure EGR via the compressed air reservoir over several engine cycles).

[0096] In this way, exhaust gas can be recirculated via a compressed air reservoir from an exhaust manifold upstream of the turbine to an intake manifold downstream of a compressor. Exhaust gas can also be recirculated via an EGR line (i.e., a low-pressure EGR line) from the exhaust manifold downstream of the turbine to the intake manifold upstream of the compressor. Specifically, the exhaust gas recirculated via the compressed air reservoir can have a higher pressure (i.e., high-pressure EGR) than the exhaust gas recirculated via the EGR line (i.e., low-pressure EGR). This allows the advantages of both low-pressure and high-pressure EGR to be realized. By pre-storing combustion exhaust gas in a compressed air reservoir, the pressurized charge can be released at a later time as needed to supplement conventional high-pressure or low-pressure EGR.

[0097] In Fig.Figure 8 now shows map 800 representing an exemplary engine operation, in which the cylinder pressure is increased by releasing pressurized charge from a compressed air reservoir with the throttle valve closed, while a compressor is actuated to increase the boost pressure. The throttle valve is then opened, and compressed air is directed into the intake manifold. Specifically, map 800 shows a change in throttle valve intake pressure (TIP) in curve 802, a change in manifold pressure (MAP) in curve 804, a change in throttle valve position in curve 806, the opening or closing of a compressed air reservoir intake vent valve in curve 808, a change in pedal position in curve 809, a change in cylinder pressure in curve 810, and a change in compressed air reservoir pressure in curve 812.In one example, the throttle intake pressure can be estimated with a pressure sensor located in the intake manifold downstream of the compressor of a turbocharger and upstream of the air intake throttle valve, the manifold pressure can be estimated with a pressure sensor in the intake manifold downstream of the throttle valve, and the compressed air storage pressure can be estimated with a pressure sensor connected to the compressed air storage tank.

[0098] Before t1, the engine can operate with a low TIP (Temperature Induction Point). For example, the engine can run without forced induction or with a low boost pressure. At t1, in response to a tip-in (indicated by the change in pedal position in curve 809), the compressor of a turbocharger can be activated. As a result of the compressor activation, boost pressure can begin to rise slowly, which is reflected as the slow increase in TIP (curve 802). For the compressor pressure to rise sufficiently, the turbine needs to spin up quickly. Until then, turbo lag can occur. To enable the faster attainment of higher boost pressures, at t1, during tip-in, pressurized charge (containing compressed air and / or exhaust gas) is released from the compressed air reservoir into the intake manifold downstream of an intake throttle valve.The release process is carried out for a period of time (between t1 and t2) while the throttle valve remains closed (curve 806). To release the pressurized charge from the accumulator, the intake release valve, which connects the accumulator to the intake manifold, is opened for a period of time between t1 and t2 (curve 808).

[0099] As the compressed air reservoir is released (see the drop in compressed air reservoir pressure in curve 812), a manifold pressure, estimated downstream of the throttle valve (curve 804), increases. Furthermore, a cylinder air charge increases (curve 810). This pressurized air allows the engine to meet torque demands while the turbine and compressor spool up to provide the desired boost pressure. Additionally, boost pressure can be pre-charged by keeping the throttle valve closed during compressor operation. Specifically, boost pressure (and thus the TIP) can be raised to a limit more quickly than would otherwise be possible.As can be seen from curve 802, between t1 and t2 the compressor pressure (reflected by TIP with the throttle closed) rises at a first, slower rate while the turbine slowly spins up to drive the compressor, and then rises at a second, faster rate while the turbine spins up faster and boost pressure builds upstream of the closed throttle. This closed-throttle operation inherently reduces turbo lag, as shown by a slower rate of reaching the limit TIP when there is no release from a reservoir with the throttle closed (curve 803, dashed line).

[0100] At t2, the pressure upstream of the throttle valve (TIP) can reach or exceed the limit value. Therefore, after the time at t2, the release from the accumulator can be suspended (curve 808), and compressed air from the compressor can be routed into the intake manifold with the intake throttle valve open (curve 806). Specifically, the intake throttle valve can be opened from its previously closed position, and the compressor charge (which was pre-charged upstream of the closed throttle valve) can be routed into the intake manifold. As a result, the MAP (manifold absolute pressure) can rise rapidly, and the cylinder charge can also increase rapidly. In this way, turbo lag is reduced, while boost pressures are quickly achieved by temporarily releasing pressurized air from a compressed air accumulator into the intake manifold with the throttle valve closed.

[0101] In this way, a compressed air reservoir can be advantageously used to store pressurized charge, containing compressed air and / or exhaust gas, for later release. Based on engine conditions, the compressed air reservoir can be charged to achieve a desired boost pressure and EGR percentage. By pre-storing a quantity of intake air and / or exhaust gas in a reservoir and releasing it into the intake or exhaust manifold based on operating conditions, turbo lag can be reduced, even when forced induction is already present. By directing the charge into the intake manifold under certain conditions, turbo lag can be reduced while satisfying a temporary engine torque demand.By directing the charge to the exhaust manifold under other conditions, the use of the charge can be extended over a longer period, as the turbine consumes the charge at a lower rate than the engine's intake tract. As a result, the increased exhaust pressure can help smooth out turbo lag and maintain continuously rising engine power during a tip-in response. By mixing exhaust gas and compressed intake air in the accumulator, high-pressure EGR can be generated and stored for release into the intake manifold, even during highly turbocharged engine operation. The released high-pressure EGR can improve combustion control and reduce NOₓ during turbocharged operation. x-Reduce emissions. By pre-charging the compressor charge air with the throttle closed, the TIP (Temperature Intake Point) can be raised faster than would otherwise be possible. By allowing charge air to be released from the reservoir into the intake manifold while simultaneously increasing the compressor charge air pressure, turbo lag can be better mitigated, while also meeting torque demands. Overall, the performance of the turbocharged engine is improved.

[0102] It should be noted that the exemplary control and estimation programs presented here can be used with various engine and / or vehicle system configurations. The specific programs described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-process operation (multitasking), multi-threading, and the like. Thus, various processes, actions, or functions shown can be executed in the sequence shown, in parallel, or, in some cases, omitted. Likewise, the processing sequence is not necessarily required to achieve the features and advantages of the exemplary embodiments of the invention described here; it is given for the sake of clarity and simplicity.One or more of the described processes or functions can be executed repeatedly, depending on the specific strategy used. Furthermore, the described processes can graphically represent code to be programmed into the computer-readable storage medium in the engine control system.

[0103] It is understood that the designs and programs disclosed herein are exemplary in nature and that these specific embodiments are not to be understood in a limiting sense, as numerous variations are possible. For example, the technology described above can be applied to V6, I4, I6, V12, boxer, and other types of engines. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and designs and other features, functions, and / or properties disclosed herein.

[0104] The following claims specifically identify certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one element" or "a first" element, or an equivalent thereof. Such claims should be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Further combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims shall also be deemed to be included in the subject matter of the present disclosure, regardless of whether their scope of protection is broader, narrower, the same as, or different from, that of the original claims.

Claims

[1] Method for a turbocharged engine (10), comprising: as a reaction to a tip-in, reducing turbo lag by releasing pressurized charge from a compressed air reservoir (54) into an exhaust manifold (36); and during a first tip-out at a higher engine speed after the tip-in, the compressed air reservoir (54) is charged with at least some compressed intake air from an intake manifold (22); and during a second tip-out at a lower engine speed after the tip-in, the compressed air reservoir (54) is charged with at least some burnt exhaust gases from the exhaust manifold (36). [2] Method according to claim 1, wherein the compressed air storage tank (54) is charged with at least some burnt exhaust gases from the exhaust manifold (36) during an engine cycle before the tip-in. [3] Method according to claim 2, further comprising adjusting a cylinder fuel injection during discharge on the basis of the pressurized charge to maintain an overall air-fuel ratio at an exhaust catalyst at or approximately at stoichiometry. [4] Method according to claim 3, wherein adjusting the cylinder fuel injection includes performing a rich fuel injection and / or a late fuel injection based on an amount and air-fuel ratio of the pressurized charge. [5] Method according to claim 4, wherein the adjustment of the cylinder fuel injection further includes the adjustment of the fuel injection based on feedback from an exhaust-air-fuel ratio sensor in the exhaust manifold (36) downstream of a turbine (16) of a turbocharger (13). [6] Method for a turbocharged engine (10), comprising: as a reaction to a tip-in, reducing turbo lag by releasing pressurized charge from a compressed air reservoir (54) into an exhaust manifold (36), wherein the compressed air storage tank (54) is charged with at least some burnt exhaust gases from the exhaust manifold (36) during an engine cycle before the tip-in, where the charging of the compressed air storage unit (54) with at least some combusted exhaust gases includes the following: During a first condition, when a tip-in is predicted at high engine speeds, the compressed air storage (54) is charged only with combusted exhaust gases; and during a second condition, when a tip-in is predicted at low engine speeds, the compressed air storage (54) is charged with fresh intake air and combusted exhaust gases, wherein a ratio of fresh intake air to combusted exhaust gases is based on a desired compressed air storage EGR percentage. [7] Method according to claim 1, wherein the discharge of pressurized charge into the outlet manifold (36) includes the discharge of the pressurized charge upstream of a turbine (16) of the turbocharger (13). [8] Method according to claim 1, wherein the draining includes draining until an outlet pressure reaches a pressure limit, and then stopping the draining. [9] Method according to claim 1, wherein the draining to the exhaust manifold (36) is carried out during a turbocharged engine operation. [10] Method for a turbocharged engine (10) comprising: Selective charging of a compressed air storage tank (54) with fresh air drawn in from an intake manifold (22) via a first valve (82) and / or combustion exhaust gas from an exhaust manifold (36) via a second valve (86); and as a reaction to a tip-in, release of pressurized charge from the compressed air reservoir (54) into the exhaust manifold (36) via a third valve (88), to reduce turbo lag, and In response to an EGR request, pressurized charge is released from the compressed air reservoir (54) into the intake manifold (22) via a fourth valve (84). [11] Method according to claim 10, wherein the selective charging includes charging with fresh intake air and combusted exhaust gas to store a compressed air storage charge with a selected EGR percentage. [12] Method according to claim 10, wherein the draining includes draining during a positive pressure condition from inlet manifold (22) to outlet manifold (36) or draining to the outlet manifold (36) until a turbine speed reaches a velocity limit, or until an inlet boost pressure reaches a pressure limit. [13] Method according to claim 10, further comprising, during the discharge, adjusting a fuel injection quantity and / or a fuel injection timing control to an engine cylinder, wherein the adjustment is based on the discharged pressurized charge to maintain an exhaust-air-fuel ratio at or approximately stoichiometry. [14] Method according to claim 10, wherein the discharge of pressurized charge to the outlet manifold (36) comprises the discharge of a first quantity of pressurized charge from the compressed air reservoir (54) to the outlet manifold (36), wherein the method further comprises, in response to the tip-in, the discharge of a second, different quantity of pressurized charge from the compressed air reservoir (54) to the inlet manifold (22). [15] Motor system (100), comprising: a turbocharged engine (10), a turbocharger (13), a compressed air reservoir (54) which is connected to both an intake manifold (22) and an exhaust manifold (36), and a control system with computer-readable commands for charging the compressed air reservoir (54) with at least some compressed intake air from an intake manifold (22) during a first tip-out at higher engine speed after a tip-in; and during a second tip-out at lower engine speed after the tip-in, charging the compressed air reservoir (54) with at least some combusted exhaust gases from the exhaust manifold (36), and in response to the tip-in, Release of charge including air and burnt exhaust gas from the compressed air storage (54) into the exhaust manifold (36) upstream of a turbine (16) of the turbocharger (13) to reduce turbo lag. [16] Engine system (100) according to claim 15, wherein the compressed air reservoir (54) is coupled to the exhaust manifold (36) via each of a first valve (86) and a second valve (88), and wherein the discharge of charge from the compressed air reservoir (54) into the exhaust manifold (36) involves opening the second valve (88) while the first valve (86) is kept closed. [17] Motor system (100) according to claim 16, wherein the control further contains instructions for: Before the tip-in, the compressed air reservoir (54) is charged with compressed air from the inlet manifold (22) and burnt exhaust gas from the exhaust manifold (36), wherein the charging with burnt exhaust gas from the exhaust manifold (36) involves opening the first valve (86) while keeping the second valve (88) closed. [18] Motor system (100) according to claim 16, wherein the draining continues for a duration until an outlet pressure upstream of the turbine (16) is at a compressed air storage pressure. [19] Motor system (100) according to claim 15, wherein the control further contains instructions for: during the draining to the exhaust manifold (36), adjusting a fuel injection to an engine cylinder so that it is richer and / or later, a richness and a delay in fuel injection based on the pressurized charge to maintain an exhaust-air-fuel ratio at an exhaust catalyst at stoichiometry.

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