Patent Grant
11352986
The present description relates generally to methods and systems for controlling a flow of recirculating exhaust gas through a heat exchanger, and more particularly to methods and systems for a rotary valve controlling the flow of recirculating exhaust gas through a dual-core heat exchanger including a bypass.
Vehicle engine systems may utilize an external exhaust gas recirculation (EGR) system to reduce NOx emissions and increase engine efficiency. For example, the external EGR system may couple an engine exhaust manifold to an engine intake manifold via an EGR passage. An EGR valve disposed within the EGR passage may be controlled to achieve a desired intake air dilution for the given engine operating conditions (e.g., engine speed, engine load, engine temperature, and fuel injection parameters such as requested fuel injection amount) to maintain desirable combustion stability while providing emissions and fuel economy benefits. Further, the efficiency of the NOx reduction may be further increased by cooling the EGR prior to mixing with the intake air via a heat exchanger positioned in the EGR passage, referred to as an EGR cooler. However, because the EGR passage is frequently coupled to the exhaust manifold or exhaust passage upstream of any catalysts or emission control devices, the EGR that flows through the EGR cooler may include hydrocarbons, particulate matter, and other emissions that may lead to deposition within the EGR cooler, referred to as fouling. EGR cooler fouling may eventually block EGR flow through the EGR cooler, increasing engine backpressure and lowering desired EGR flow, each of which may negatively impact engine performance and/or emissions.
Other attempts to reduce EGR cooler fouling include positioning a catalyst, such as a hydrocarbon trap and/or particulate filter, upstream of the EGR cooler. One example approach is shown by Styles et al. in U.S. Pat. No. 7,461,641. Therein, a dedicated EGR catalyst (which may be a hydrocarbon trap or particulate filter) is positioned upstream of an EGR cooler. The inclusion of the dedicated EGR catalyst in the EGR system may allow for an additional EGR cooler core to be placed in series with an initial EGR cooler core. The two EGR cooler cores may provide additional cooling of the EGR, while the dedicated EGR catalyst prevents fouling of the EGR cooler cores that may otherwise occur, particularly in the second EGR cooler core where low EGR temperatures are attained.
However, the inventors herein have recognized that a dedicated EGR catalyst is expensive and increases the packaging space of the EGR system, which may make the inclusion of the EGR catalyst impractical in some engine systems. Further, while the system shown by Styles et al. includes a bypass passage controlled by a bypass valve that allows EGR to bypass the EGR cooler cores under some conditions (e.g., engine warm-up or when fouling is still predicted to occur), the bypass valve configuration may still allow at least some flow through the EGR cooler cores when the EGR is intended to bypass the EGR cooler cores, which may cause fouling over time.
In one example, the issues described above may be addressed by a method including flowing EGR through an EGR cooler positioned in an EGR passage, the EGR cooler comprising a bypass passage, a first cooler core flow path, and a second cooler core flow path, and adjusting a valve to selectively block or allow flow of EGR though the bypass passage, the first cooler core flow path, and the second cooler core flow path. In this way, cooling of the EGR may be achieved when demanded, while minimizing EGR cooler fouling, by routing EGR through the bypass passage only, through the bypass passage and one of the cooler core flow paths, or through both of the cooler core flow paths. For example, during conditions where EGR cooler fouling is likely (such as lower EGR flow and/or lower engine load conditions), all EGR may be directed through one of the cooler core flow paths, which may increase the velocity of the EGR and thus reduce fouling. During conditions where EGR cooler fouling is less likely (such as higher EGR flow and/or higher engine load conditions), the EGR may be split between the two cooler core flow paths, thereby providing increased EGR cooling and reduced pressure drop across the EGR cooler.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The following description relates to systems and methods for modulating flow of exhaust gas through an exhaust gas recirculation (EGR) system including a cooling system (e.g., EGR cooler) in a vehicle, such as the hybrid vehicle shown in
The dual-core EGR cooler having a bypass passage and being controlled by the rotary valve may allow for bypassing both EGR cooler core flow paths, EGR flow through only one or through both EGR cooler core paths, or EGR flow through one cooler core path and the bypass passage, based on EGR flow and EGR cooler demands, as shown by the method of
The EGR cooler including the rotary valve described herein may provide several advantages. The inclusion of two smaller EGR cooler core paths rather than a single, larger EGR cooler core with a single flow path may reduce EGR cooler fouling, as EGR flow may be limited to only one EGR cooler core path during low flow conditions, which may maintain a relatively high flow rate through the EGR cooler core. During low EGR cooling demand conditions (e.g., engine warm-up) and low EGR flow conditions, flow through one or both of the EGR cooler core paths may be blocked by the rotary valve. The rotary valve may seal the EGR cooler cores on both the upstream and the downstream ends, which may prevent inadvertent admission of EGR into the EGR cooler cores, further lowering EGR cooler fouling. Additionally, the rotary valve may allow for a partial EGR cooler bypass, where some EGR flows through one of the EGR cooler core paths and some EGR bypasses the EGR cooler core paths, which may help facilitate flow during low differential pressure conditions.
Combustion chamber 30 and the rest of the cylinders of engine 10 may receive intake air from an intake manifold 44 via an intake passage 42 and may exhaust combustion gases via an exhaust passage 48. Intake manifold 44 and exhaust passage 48 can selectively communicate with combustion chamber 30 via an intake valve 52 and an exhaust valve 54, respectively. In some embodiments, combustion chamber 30 may include two or more intake valves and/or two or more exhaust valves. In this example, intake valve 52 may be controlled by controller 12 by cam actuation via a cam actuation system 51. Similarly, exhaust valve 54 may be controlled by controller 12 via a cam actuation system 53. Cam actuation systems 51 and 53 may each include one or more cams and may utilize one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT) and/or variable valve lift (VVL) systems that may be operated by controller 12 to vary valve operation. The position of intake valve 52 and exhaust valve 54 may be determined by valve position sensors (not shown) and/or camshaft position sensors 55 and 57, respectively. In alternative embodiments, intake valve 52 and/or exhaust valve 54 may be controlled by electric valve actuation. For example, cylinder 30 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation, including CPS and/or VCT systems. In still other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or actuation system or a variable valve timing actuator or actuation system.
In some embodiments, each cylinder of engine 10 may include a spark plug 92 for initiating combustion. An ignition system 88 can provide an ignition spark to combustion chamber 30 via spark plug 92 in response to a spark advance signal SA from controller 12, under select operating modes. Although spark ignition components are shown, in some embodiments, combustion chamber 30 or one or more other combustion chambers of engine 10 may be operated in a compression ignition mode, with or without an ignition spark.
In some embodiments, each cylinder of engine 10 may be configured with one or more fuel injectors for providing fuel thereto. As a non-limiting example, cylinder 30 is shown including one fuel injector 66. Fuel injector 66 is shown coupled directly to combustion chamber 30 for injecting fuel directly therein in proportion to the pulse width of a signal FPW received from controller 12 via an electronic driver 68. In this manner, fuel injector 66 provides what is known as direct injection (hereafter also referred to as “DI”) of fuel into combustion chamber 30. While
Fuel may be delivered to fuel injector 66 from a high pressure fuel system 172 including fuel tanks, fuel pumps, and a fuel rail. Alternatively, fuel may be delivered by a single stage fuel pump at a lower pressure, in which case the timing of the direct fuel injection may be more limited during the compression stroke than if a high pressure fuel system is used. Further, while not shown, the fuel tanks may have a pressure transducer providing a signal to controller 12. Fuel tanks in fuel system 172 may hold fuel with different fuel qualities, such as different fuel compositions. These differences may include different alcohol content, different octane, different heptane, different heat of vaporizations, different fuel blends, and/or combinations thereof, etc.
Continuing with
An exhaust gas sensor 128 is shown coupled to exhaust passage 48 upstream of an emission control device 70. Upstream exhaust gas sensor 128 may be any suitable sensor for providing an indication of exhaust gas air-fuel ratio, such as a linear wideband oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state narrowband oxygen sensor or EGO, a HEGO (heated EGO), a NOx sensor, an HC sensor, or a CO sensor. In the example of
Emission control device 70 is shown arranged along exhaust passage 48 downstream of exhaust gas sensor 128. Emission control device 70 may be a three-way catalyst (TWC) configured to reduce NOx and oxidize CO and unburnt hydrocarbons. In some embodiments, emission control device 70 may be a lean NOx trap, a particulate filter, various other emission control devices, or combinations thereof. In some examples, one or more additional emission control devices may be coupled to exhaust passage 48. Further, in some examples, one or more additional exhaust gas sensors may be coupled to exhaust passage 48 downstream of emission control device 70 to indicate an AFR of the exhaust gas after passing through emission control device 70 and before exiting to the atmosphere through tailpipe 77.
As shown in
Under some conditions, the EGR system may be used to regulate the temperature of the air and fuel mixture within the combustion chamber. Further, EGR may be desired to attain a desired engine dilution, thereby improving fuel efficiency and emissions quality, in particular, emissions of nitrogen oxides. For example, EGR may be requested at low to mid engine loads. Additionally, EGR may be desired after emission control device 70 has attained its light-off temperature. An amount of EGR requested may be based on engine operating conditions, including engine load (as estimated via pedal position sensor 134), engine speed (as estimated via a crankshaft position sensor), engine temperature (as estimated via an engine coolant temperature sensor 112), etc. For example, controller 12 may refer to a look-up table having the engine speed and load as the input, and output a desired amount of EGR corresponding to the input engine speed-load. In another example, controller 12 may determine the desired amount of EGR (e.g., desired EGR flow rate) through logic rules that directly take into account parameters such as engine load, engine speed, engine temperature, etc. In still other examples, controller 12 may rely on a model that correlates a change in engine load with a change in a dilution requirement, and further correlates the change in the dilution requirement with a change in the amount of EGR requested. For example, as the engine load increases from a low load to a mid load, the amount of EGR requested may increase, and then as the engine load increases from a mid load to a high load, the amount of EGR requested may decrease. Controller 12 may further determine the amount of EGR requested by taking into account a best fuel economy mapping for a desired dilution rate. After determining the amount of EGR requested, controller 12 may refer to a look-up table having the requested amount of EGR as the input, and a signal corresponding to a degree of opening to apply to the EGR valve (e.g., as sent to the stepper motor) as the output.
The EGR system may additionally include an EGR cooler 202, through which recirculated exhaust gas may flow. Exhaust gas may flow through the EGR cooler 202 and interact with one or more cooler cores, which may lower the exhaust gas temperature. In some examples, the EGR cooler 202 may have two cooler cores. In other examples, the EGR cooler 202 may have one cooler core that includes two separate flow paths (e.g., an inlet of the cooler core may be bifurcated such that part of the inlet leads to a first set of cooling channels and another part of the inlet leads to a second set of cooling channels). The EGR cooler 202 may comprise a bypass passage through which exhaust gas may flow when requested by the controller 12, bypassing the cooler core(s). The EGR cooler may additionally comprise a valve which may modulate the flow of exhaust gas through the cooler, allowing the exhaust gas to pass through the EGR cooler core(s) and/or the bypass passage as needed. For example, the entirety of the recirculated exhaust gas may flow through the bypass passage when the volume of EGR is low and/or when a threshold temperature, such as the emission control device 70 light off temperature, has not been met, and cooling of the recirculated exhaust gas may be undesirable. In still another example, the exhaust gas may flow through both EGR cooler core flow paths, through only one EGR cooler core flow path, or the exhaust gas may flow through one EGR cooler core flow path and the bypass passage, for example. In some examples, controller 12 may send signals to an actuator of the valve which may adjust the position of the valve in order to modulate the flow of exhaust gas within the EGR cooler 202. Additional details about the EGR cooler and the valve are provided below with respect to
In some examples, vehicle system 100 may include a turbocharger (not shown) including a turbine positioned in exhaust passage 48 and a compressor positioned in intake passage 44, with the turbine coupled to the compressor via a shaft. Exhaust gas may spin the turbine which in turn spins the compressor, thereby compressing intake air provided to the engine. The turbine may be positioned upstream of the junction of exhaust passage 48 and EGR passage 140, thereby providing what is referred to as low-pressure EGR through EGR passage 48. In other examples, the turbine may be positioned downstream of the junction of exhaust passage 48 and EGR passage 140, thereby providing what is referred to as high-pressure EGR through EGR passage 48. In still further examples, both low-pressure and high-pressure EGR may be provided (necessitating an additional EGR passage).
Controller 12 is shown in
Controller 12 may receive various signals from sensors coupled to engine 10, in addition to those signals previously discussed, including measurement of inducted mass air flow (MAF) from mass air flow sensor 120; engine coolant temperature (ECT) from temperature sensor 112 coupled to a cooling sleeve 114; a profile ignition pickup signal (PIP) from a Hall effect sensor 118 (or other type) coupled to crankshaft 40; throttle position (TP) from the throttle position sensor; and absolute manifold pressure (MAP) signal from MAP sensor 122. Engine speed, RPM, may be generated by controller 12 from signal PIP. Controller 12 receives signals from the various sensors of
In some examples, vehicle system 100 may be a hybrid vehicle with multiple sources of torque available to one or more vehicle wheels. For example, vehicle system 100 may include engine 10 and an electric machine 152, which may be a motor or a motor/generator. In other examples, vehicle 100 is a conventional vehicle with only an engine. In the example shown, vehicle system 100 includes engine 10 and electric machine 152. Crankshaft 40 of engine 10 and electric machine 152 are connected via transmission 154 to vehicle wheels 155 when one or more clutches 156 are engaged. In the depicted example, a first clutch 156 is provided between crankshaft 40 and electric machine 152, and a second clutch 156 is provided between electric machine 152 and transmission 154. Controller 12 may send a signal to an actuator of each clutch 156 to engage or disengage the clutch, so as to connect or disconnect crankshaft 40 from transmission 154 and the components connected thereto, and/or connect or disconnect electric machine 152 from transmission 154 and the components connected thereto. Transmission 154 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various manners, including as a parallel, a series, or a series-parallel hybrid vehicle.
Electric machine 152 receives electrical power from a traction battery 158 to provide torque to vehicle wheels 155. Electric machine 152 may also be operated as a generator to provide electrical power to charge battery 158, for example during a braking operation.
As described above,
As mentioned above, an EGR system may recirculate a portion of exhaust gas to an intake manifold of an engine in order to provide a desired engine dilution. Recirculated exhaust gas may increase fuel economy and reduce emissions, for example. Because the recirculated exhaust gas is typically at relatively high temperature, the EGR system may include an EGR cooler to reduce the temperature of the EGR before admission to the engine, which may reduce engine misfire and other issues. However, in some engines, particularly engine configurations where the EGR is sourced before the aftertreatment system, compounds carried with the EGR have the potential to deposit in the EGR cooler. This fouling of the EGR cooler reduces the cooling effectiveness, increases pressure drop across the EGR cooler, and can lead to plugging of the cooler. Deposit formation is a function of coolant temperature, EGR temperature, and EGR flow velocity through the EGR cooler. While some EGR cooler configurations include a bypass circuit to prevent fouling under some conditions, flow through the bypass circuit limits the ability to cool the EGR. Additionally, in some configurations, while the bypass circuit is open, the heat exchanger component of the EGR cooler (referred to as the cooler core) is not completely isolated from the EGR gasses, and pulsations can cause deposits to form in the cooler core.
Thus, according to embodiments disclosed herein, an EGR cooler, such as EGR cooler 202 described above, may include three flow paths which can be selected for different operating conditions. Two paths include heat exchangers (e.g., cooler cores) for cooling the EGR, and one path bypasses the heat exchangers. The EGR cooler is thus configured to operate in four modes: 1) only the bypass is open; 2) the bypass and one heat exchanger are open; 3) only one heat exchanger is open; and 4) the two heat exchangers are open and the bypass is closed. An actuator moves a four position valve assembly to select between these modes. The actuator and valve assembly may be referred to herein as a rotary valve. Compared to prior EGR coolers, the EGR cooler described herein provides two additional modes: 1) bypass and a small cross section of heat exchanger in parallel to allow some cooling with low pressure drop; and 2) all flow through a small cross section of heat exchanger to keep velocity higher and reduce deposit formation. Additionally, the rotary valve described herein positively seals off both ends of the heat exchangers during bypass operation to prevent deposits from forming in the heat exchangers due to pulsation flow.
In some examples, rather than including two separate EGR cooler cores each with a respective inlet and outlet as shown in
The flow of exhaust gas through and/or around the EGR cooler cores and through and/or around the bypass passage may be modulated by the action of the rotary valve 212. The rotary valve 212 may comprise a first end plate 214, positioned at the downstream end of the EGR cooler 202, intermediate an EGR cooler outlet 224 and the respective outlets of the first EGR cooler core 206, the second EGR cooler core 208, and the bypass passage 210. The rotary valve 212 may additionally comprise a second end plate 216, positioned at the upstream end of the EGR cooler 202, intermediate an EGR cooler inlet 222 and the respective inlets of the first EGR cooler core 206, the second EGR cooler core 208, and the bypass passage 210. The rotary valve 212 may couple fluidly to the bypass passage 210, the first EGR cooler core 206, and the second EGR cooler core 208.
The first end plate 214 of the rotary valve and the second end plate 216 of the rotary valve may rotate around a shaft 218, which may be located in the center of the rotary valve. The shaft 218 may extend along or parallel to a central longitudinal axis of the EGR cooler 202, in one example. The shaft may be rotationally coupled to a motor 220, which may rotate the shaft 218 and therefore the rotary valve 212 when commanded by a controller, such as controller 12.
Exhaust gas may enter the EGR cooler 202 from the EGR cooler inlet 222, positioned at an upstream end of the EGR cooler 202, and flow into a second EGR chamber 228. The second EGR chamber 228 may be fluidly coupled to all or some of the bypass passage, first EGR cooler core, second EGR cooler core, depending on the position and engagement of the rotary valve 212. The second end plate 216 may either block or allow passage of exhaust gas through the bypass passage or the EGR cooler cores, depending on its position.
A first EGR chamber 226 may be fluidly coupled to all or some of the bypass passage, first EGR cooler core, and second EGR cooler core, depending on the position and engagement of the rotary valve 212. The first end plate 214 may either block or allow passage of exhaust gas through the bypass passage 210 or the EGR cooler cores, depending on its position. The position of the first end plate 214 may correspond to the position of a second end plate 216 (e.g., as the shaft 218 rotates the end plates in tandem), such that when the rotary valve 212 is positioned to block flow through the bypass passage 210, the first EGR cooler core 206, and/or the second EGR cooler core 208, each end of the blocked passage or core is sealed. In this way, the blocked passage or core(s) does not experience inadvertent flow of exhaust during EGR pressure pulsations.
The first poppet valve 306 and the second poppet valve 308 are aligned along a common first axis 320. Likewise, the first opening 302 and the second opening 304 are aligned along a common second axis 322, parallel to the first axis 320. The first opening 302 and the first poppet valve 306 are aligned along a common third axis 324, perpendicular to the first axis 320. The second opening 304 and the second poppet valve 308 are aligned along a common fourth axis 326, parallel to the third axis 324.
The second end plate 216 includes a third opening 310, a fourth opening 312, a third poppet valve 314, and a fourth poppet valve 316. The third poppet valve 314 and the fourth poppet valve 316 of the second end plate 216 are positioned on an interior side of the second end plate 216, facing into the interior of the EGR cooler 202 (e.g., away from the second chamber 228).
The third poppet valve 314 and the fourth poppet valve 316 are aligned along a common fifth axis 328. Likewise, the third opening 310 and the fourth opening 312 of the second end plate are aligned along a common sixth axis 330, parallel to the fifth axis 328. The third opening 310 and the third poppet valve 314 are aligned along a common seventh axis 332, parallel to the third axis 324. The fourth opening 312 and the fourth poppet valve 316 of the second end plate are aligned along a common eighth axis 334, parallel to the seventh axis 332.
In the dual-cooler position shown in
In the position pictured in
The third poppet valve 314 seals the bypass passage 210, preventing exhaust gas from flowing into the bypass passage 210. The first poppet valve 306 is similarly sealingly engaged with the bypass passage 210.
The fourth poppet valve 316 and the second poppet valve 308 are not sealing any passage or cooler in the dual-cooler position shown in
Because the bypass passage 210 is sealed from the upstream and downstream ends, substantially no exhaust may enter the bypass passage. Exhaust may flow only through the first EGR cooler core 206 and the second EGR cooler core 208.
The rotary valve 212 is positioned such that the second opening 304 is aligned with and fluidly coupled to the bypass passage 210 and the fourth opening 312 is aligned with and fluidly coupled to the bypass passage 210. The fluid coupling of the bypass passage 210 with an opening in each of the end plates (e.g., second opening 304 and fourth opening 312) allows exhaust gas to flow through the bypass passage 210. By travelling through the bypass passage 210, the exhaust gas may experience substantially no cooling, and may exit the EGR cooler 202 at substantially the same temperature at which the exhaust gas entered the EGR cooler 202. The rotary valve may be positioned in the bypass passage position during low engine load where EGR flow is relatively low, for example. The bypass position may additionally be used when there is little or no desire for the recirculating exhaust gas to be cooled, such as during start up, or when a temperature of the engine, such as a temperature of the engine 10 and/or the emission control device 70, is below a desired temperature.
In the bypass position shown in
The first EGR cooler core 206 may be sealed by the first poppet valve 306 and by the third poppet valve 314. The first poppet valve 306, when sealing the outlet of the first EGR cooler core 206, may prevent exhaust gas from passing into or exiting the first EGR cooler core 206 from the downstream first EGR chamber 226, shown in
Similarly, the second poppet valve 308 of the first end plate (blocked from view in
When the first EGR cooler core 206 or the second EGR cooler core 208 are blocked by the rotary valve 212 in the bypass position, the exhaust gas may flow entirely through the bypass passage 210. Because the exhaust gas is not flowing through the first EGR cooler core 206 or the second EGR cooler core 208, the exhaust gas may not be substantially cooled during its path through the EGR cooler 202. In other words, the exhaust gas may exit the EGR cooler 202 at substantially the same temperature at which the exhaust gas entered the EGR cooler 202. This maintenance of exhaust gas temperature may be beneficial in increasing the engine 10 and/or emission control device 70 temperature, if desired.
The rotary valve 212 may be rotated to two other positions (e.g., in addition to the illustrated bypass position and dual-core position). The two other positions may include a single cooler position where all EGR flows through one of the EGR cooler cores, and a cooler-bypass position where the EGR flow is split between one of the EGR cooler cores and the bypass passage. For example, the motor 220 may be activated via a command sent from the controller to move into the single cooler position, and as a result, the motor 220 may rotate the shaft 218 by 90° clockwise (relative to the position shown in
As another example, the motor 220 may be activated via a command sent from the controller to move into the cooler-bypass position, and as a result, the motor 220 may rotate the shaft 218 by 90° counterclockwise (relative to the position shown in
While the rotary valve 212 is illustrated and described herein as including poppet valves to seal the various passages/cores of the EGR cooler 202, in other examples, the rotary valve may include other mechanisms to seal the bypass passage and the EGR cooler core(s), such as a flat surface of each end plate configured to be in face-sharing contact with the inlet or outlet of the bypass passage or EGR cooler core(s), or the bypass and EGR cooler cores may be sealed by another sealing mechanism, such as a gasket, on the end plate.
As shown in
As shown in
When the rotary valve is in the single-cooler position 530, the first EGR cooler core inlet 506 may be open, thereby allowing EGR to flow through the first EGR cooler core, while the bypass passage inlet 504 and the second EGR cooler core inlet 508 are both blocked by poppet valves of the rotary valve. In this way, exhaust gas may flow through the first EGR cooler core, a poppet valve may be sealingly engaged with the second EGR cooler core inlet 508, preventing exhaust gas from flowing through the second EGR cooler core, and another poppet valve is sealingly coupled to the bypass passage inlet 504, preventing exhaust gas from flowing through the bypass passage.
When the rotary valve is in the dual cooler position 540, the first EGR cooler core inlet 506 is open, allowing exhaust gas to flow through the first EGR cooler core inlet 506 and into the first EGR cooler core. The second EGR cooler core inlet 508 is also open, allowing exhaust gas to flow through the second EGR cooler core. One of the poppet valves may be sealingly engaged with the bypass passage inlet 504 such that no exhaust gas may flow through the bypass passage. The other poppet valve may not be engaged because there may be no passage or EGR cooler core for the other poppet valve to engage with.
When the rotary valve is in the bypass-cooler position 550, the second EGR cooler core inlet 508 and the bypass passage inlet 504 are each open, such that exhaust gas may flow into and then out of the second EGR cooler core and the bypass passage. One of the poppet valves may seal the first EGR cooler core inlet 506 such that substantially no exhaust gas may flow through the first EGR cooler core inlet or the first EGR cooler core.
The passage 602 may be a bypass passage, the first EGR cooler core, or the second EGR cooler core, as the bypass passage, first EGR cooler core, and second EGR cooler core may engage with the rotary valve in substantially the same or identical ways. The end plate 606 may be the first end plate, but the first end plate and the second end plate may have structures which are substantially identical, but mirrored across a plane that is perpendicular to the axis of rotary valve shaft 612. For example, the second end plate may include similar poppet valves to the poppet valve 616 shown in
The passage 602 extends longitudinally towards the end plate 606. The passage may comprise a cylindrical tube through which exhaust may flow. The passage may terminate at an outlet plate 614 that extends radially outward from the walls of the passage. In some examples, the outlet plate 614 may include openings for and be coupled to each of the bypass passage, the first EGR cooler core, and the second EGR cooler core, and may have a shape and size that match the inner dimensions of the EGR cooler housing. The EGR cooler may include a similar plate at the inlet end, e.g., an inlet plate as described above with respect to
The poppet valve 616 may sealingly engage with the plate 614, preventing exhaust gas from flowing into or out of the passage 602. The poppet valve 616 may comprise a valve head 604 coupled to a valve stem 608. The valve stem 608 may comprise a central shaft, engaged with the end plate 606 to secure the valve stem 608 in position and to rotate the poppet valve 616 about the central longitudinal axis (e.g., the shaft 612). The valve head 604 may be seated on the plate 614 so that the valve head 604 extends across and seals the passage 602, with the edges of the valve head 604 in face-sharing contact with the plate 614.
A spring 610 may be coupled to the valve stem 608, and wrapped around a portion of the outer circumferential area of the valve stem 608. The spring 610 may be coupled to the valve head 604 such that the spring 610 may push the valve head longitudinally towards the plate 614, thereby maintaining the valve head 604 in contact with the plate 614.
The end plate 606 and coupled components (e.g. the poppet valve and spring) may rotate around the shaft 612. The rotary valve shaft 612 may extend longitudinally, perpendicular to the end plate 606. The rotary valve shaft 612 may be engaged with a second end plate (not pictured in
At 702, the method 700 includes determining operating parameters. The operating parameters may include engine load, engine speed, engine temperature, EGR valve position, and other operating parameters. At 704, method 700 includes determining if EGR is flowing. EGR may be determined to be flowing based on the determined operating parameters (e.g., engine speed and load, engine temperature), based on a current position of the EGR valve (e.g., EGR valve 142 of
If at 708 the EGR cooler bypass conditions have been met, the method proceeds to 710, in which the EGR cooler rotary valve is adjusted or maintained to be in the bypass position. The bypass position of the rotary valve is shown in
If the EGR cooler bypass conditions have not been met at 708, the method proceeds to 714 to determine if the engine speed and engine load are in a first speed-load region. The first speed-load region may include high engine loads across all engine speeds (e.g., 90% maximum load or greater) and at higher engine speeds, also include mid-to-high engine loads (e.g., 65 or 75% maximum load or greater). An example speed-load map including four regions for controlling the four rotary valve positions described herein is shown in
It is to be appreciated that while method 700 as described herein monitors engine speed and load and adjusts the position of the rotary valve to the dual-core position in response to engine load increasing above a threshold load for a given engine speed, other engine operating parameters may be monitored in addition or alternative to engine load. For example, an amount or rate of EGR flowing into the EGR cooler may be monitored, based on a position of the EGR valve, commanded EGR rate (which may be based on engine speed and load), and/or engine fueling parameters (e.g., fuel injection amounts). If the EGR amount or rate exceeds a threshold, the rotary valve may be adjusted to the dual-core position.
Returning to 714, if the engine speed and load are not in the first region, the method proceeds to 720 (shown in
If the engine is operating in the second speed-load region, the method continues to 722, which includes adjusting (or maintaining) the EGR cooler rotary valve into the single-core position. The single-core position may be the single-core position 530 of
Returning to 720, if the engine is not operating in the second speed-load region, the method proceeds to 726, which comprises adjusting (or maintaining) the EGR cooler rotary valve position to the bypass-cooler position, and at 728, exhaust gas is recirculated through a single EGR cooler core flow path and the bypass passage. The bypass-cooler position may be the bypass-cooler position 550 of
The Y axis for plot 802 indicates engine load, which increases continuously from bottom to top of plot 802. Curve 804 indicates the relation between load and time, in this example.
The Y axis for plot 806 indicates the value of EGR valve position. The Y value may be a position ranging continuously from closed at the bottom to open at the top. This value may correspond to the amount of exhaust gas flowing into the EGR cooler, at least during most operating conditions. Curve 808 indicates the relationship between EGR valve position and time, in this example.
The Y axis of plot 810 indicates the position of the rotary valve of the EGR cooler. The value refers to a discrete position of the rotary valve, which may be in position 1, corresponding to the bypass position; position 2, corresponding to the single-cooler position; position 3, corresponding to the dual-cooler position; or position 4, corresponding to the bypass-cooler position. Curve 812 indicates the relation between rotary valve position and time, in this example.
Five time points of interest are presented as dashed vertical lines. At time t1, the engine, which may be the engine 10 shown in
At t2, the load is still low but is increasing (e.g., as the vehicle is launched), and due to the increased load, the EGR valve begins to open. However, the engine is still warming up and thus cooling of the EGR is not desired. As a result, the position of the rotary valve may be maintained in the first (bypass) position, allowing all of the recirculated exhaust gas to flow through the bypass passage.
At t3 the load has increased to medium load (above a first threshold T1), and the EGR valve is partially opened (e.g., 25% open) to allow exhaust gas to circulate through the EGR system. At time t3, the engine is warmed up. Accordingly, the controller, such as the controller shown in
Between t3 and t4, the load increases and the opening of the EGR valve increases. At t4, the load has reached and exceeds a second threshold load T2 and the opening of the EGR valve continues to increase, thereby allowing more exhaust to flow through the EGR system. To accommodate the increased volume of exhaust gas and prevent increased exhaust backpressure, the controller sends a signal to rotate the rotary valve to a third (dual-core) position, allowing all of the recirculated exhaust gas to flow through the two EGR cooler core flow paths.
Between t4 and t5, the load plateaus and then begins to decrease; the EGR valve also begins to close as the load decreases. At t5, the load has decreased to back below the first threshold, and as a result, EGR flow through both EGR cooler core flow paths is not indicated. However, a low differential pressure may be present in the EGR system, and thus the controller sends a signal to the rotary valve to rotate to the fourth (bypass-cooler) position. In this state, exhaust gas may flow through only one EGR cooler core and the bypass passage.
Thus, the position of the rotary valve may be adjusted to flow EGR through none, one, or both cooler core flow paths, based on engine speed and load, likelihood of cooler fouling, and/or other parameters. During high loads where higher levels of cooling are demanded, the EGR may be directed through two cooler core flow paths (e.g., through both EGR cooler cores). During low loads where no cooling is demanded, the EGR may be directed though only the bypass passage, to avoid cooling the EGR.
During medium loads where only moderate levels of cooling are demanded, the EGR may be directed through a single cooler core flow path (e.g., through only one EGR cooler core), and there is sufficient pressure drop over the system to flow the demanded EGR rate in this configuration. The higher velocities through the EGR cooler due to only flowing through half the normal cross section of the EGR cooler core(s) also inhibit fouling and is beneficial for medium load conditions with high soot concentrations and fouling risk. Conversely, if the soot concentrations are relatively low and even more moderate levels of cooling are demanded, EGR may be directed through one cooler core flow path and the bypass passage. This may provide an even lower level of cooling than flowing all the EGR through one cooler core flow path and be more appropriate for the lower end of the low/medium load regime where having sufficient pressure drop over the system to flow EGR is also an issue.
Four operation modes are presented, which may be discrete operation modes resulting from the four positions of the rotary valve. These positions may be influenced by continuous values along the X and Y axes, corresponding to values of engine load and engine speed, respectively.
A first mode 902 corresponds to the bypass position of the rotary valve, in which EGR flows only through the bypass passage. In the first mode 902, the engine, which may be the engine 10 shown in
The second mode 904 corresponds to the bypass-cooler mode, in which EGR flows through the bypass passage and an EGR cooler core flow path. In the second mode 904, the engine operates with low to medium loads (e.g., 30%-50% load), and the engine speed may be low to high. When load increases above the first threshold 910, the controller may send a signal to rotate the rotary valve into the bypass-cooler operation mode. A second threshold 912 may define a boundary between the second mode 904 and a third mode 906. The second threshold 912 may also decrease with increasing engine speed.
The third mode 906 corresponds to the single-core mode. When engine load increases past the second threshold 912, the controller may send a signal to rotate the rotary valve into single-core position, so that cooling of the EGR may be performed by flowing the EGR through one cooler core flow path of the EGR cooler only. A third threshold 914 may define a boundary between the third mode 906 and a fourth mode 908, and the third threshold 914 may decrease with increasing engine speed. The third threshold 914 may have a negative slope that is steeper than the slopes of the first threshold and second threshold. When engine load increases above the third threshold 914, the rotary valve may be operated/moved according to the fourth mode 908, which corresponds to the dual-core position, allowing exhaust gas to flow through two EGR cooler core flow paths.
Thus, graph 900 illustrates four different modes for controlling the rotary valve and flow of EGR though the EGR cooler. The four modes correspond to four regions of a speed-load plot that may be stored in memory of the controller. During engine operation, current engine speed and engine load may be entered as input to the speed-load plot, and based on the speed-load plot, the current region (or mode) of engine operation may be determined. The rotary valve may be controlled accordingly. For example, the rotary valve may be moved from the bypass position to the bypass-cooler position when engine speed and/or load increase from the first region (e.g., operation in the first mode 902) to the second region (e.g., operation in the second mode 904). The rotary valve may be moved from the bypass-cooler position to the single-core position when engine speed and/or load increase from the second region (e.g., operation in the second mode 904) to the third region (e.g., operation in the third mode 906). The rotary valve may be moved from the single-core position to the dual-core position when engine speed and/or load increase from the third region (e.g., operation in the third mode 906) to the fourth region (e.g., operation in the fourth mode 908).
In this way, an EGR rotary valve positioned in an EGR cooler may be adjusted to one of four positions in order to direct EGR flow through a bypass passage (e.g., bypassing cooler cores of the EGR cooler), through a single cooler core flow path of the EGR cooler, through two cooler core flow paths of the EGR cooler, or through both the bypass passage and one of the cooler core flow paths of the EGR cooler. By providing two EGR cooler core flow paths and the rotary valve described herein, the velocity of the EGR through a cooler core flow path of the EGR cooler during low EGR flow conditions may be increased by directing the EGR through only the single cooler core flow path, thereby lowering the risk of fouling in the cooler core. During higher flow conditions, the EGR may be directed through both cooler core flow paths. Further, during conditions where cooling of the EGR is not indicated, the EGR may be directed through the bypass passage and not through the cooler core(s). Additionally, during lower flow conditions where differential pressure across the EGR cooler is low, the EGR flow may be split between one of the cooler core flow paths and the bypass passage. In doing so, the EGR may be cooled as indicated, when EGR cooler fouling is not indicated. Further, the rotary valve described herein may include mechanisms (e.g., poppet valves) to seal the bypass passage or the cooler core(s) on both the upstream and the downstream ends, which may prevent inadvertent admission of EGR into any sealed passages/cores.
The technical effect of controlling a valve in an EGR cooler is to selectively block or allow flow through a bypass passage, a first EGR cooler core, and a second EGR cooler core, as desired, which may prevent EGR cooler fouling while providing sufficient/demanded EGR cooling
Another technical effect of the disclosure is bidirectional sealing of the bypass passage, first cooler core, and second cooler core, which may reduce cooler fouling, maintain desired EGR flow to the exhaust intake, and produce desired cooling of the EGR. By sealing both the upstream and downstream ends of the bypass passage and cooler core(s) when requested, exhaust may be prevented from entering into the bypass passage and the first and second cooler cores.
The structure of the EGR cooler comprising two end plates may allow for EGR to enter the EGR cooler through a central upstream inlet and exit the EGR cooler through a central downstream exit. Thus the exhaust gas may be split within the EGR cooler to traverse the appropriate passage (e.g. the bypass passage, the first EGR cooler core, or the second EGR cooler core), but combine downstream to flow through one pipe. Thus, the portion of the exhaust system which comprises multiple pipes may be minimized, and the expense and packaging needs of having multiple pipes may be avoided.
Utilizing two end plates to seal the EGR cooler cores and the bypass passage may allow for a reduction in costly and bulky actuators. One actuator may be used to rotate the two endplates, eliminating the need for a valve actuator for each of the valves of the bypass passage and the two EGR cooler cores. By using passive sealing mechanisms, (e.g. poppet valves sealingly engaged with the inlet and outlet of the bypass passage or EGR cooler cores, or by a flat endplate in fluidically-sealing, face-sharing contact with the inlet and outlet of the bypass passage or EGR cooler core), the passage may be sealed without the need for an actuator to change their state, further reducing the number of actuators needed.
The disclosure also provides support for a method, comprising: flowing exhaust gas recirculation (EGR) through an EGR cooler positioned in an EGR passage, the EGR cooler comprising a bypass passage, a first cooler core flow path, and a second cooler core flow path, and adjusting a valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core flow path, and the second cooler core flow path. In a first example of the method, the valve of the EGR cooler is a rotary valve positioned at least partially within a housing of the EGR valve, and wherein flowing EGR through the EGR cooler comprises opening an EGR valve positioned in the EGR passage upstream or downstream of the EGR cooler. In a second example of the method, optionally including the first example, adjusting the valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core flow path, and the second cooler core flow path comprises, responsive to a first condition, adjusting the valve into a first position where the first cooler core flow path and the second cooler core flow path are each blocked, and flowing the EGR through the bypass passage and not through the first cooler core flow path or the second cooler core flow path. In a third example of the method, optionally including the first and/or second examples, adjusting the valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core flow path, and the second cooler core flow path comprises, responsive to a second condition, adjusting the valve into a second position where the second cooler core flow path and the bypass passage are each blocked, and flowing the EGR through the first cooler core flow path and not through the second cooler core flow path or the bypass passage. In a fourth example of the method, optionally including one or more or each of the first through third examples, adjusting the valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core flow path, and the second cooler core flow path comprises, responsive to a third condition, adjusting the valve into a third position where the bypass passage is blocked, and flowing the EGR through the first cooler core flow path and the second cooler core flow path and not through the bypass passage. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, adjusting the valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core flow path, and the second cooler core flow path comprises, responsive to a fourth condition, adjusting the valve into a fourth position where the first cooler core flow path is blocked, and flowing the EGR through the second cooler core flow path and the bypass passage and not through the first cooler core flow path. In a sixth example of the method, optionally including one or more or each of the first through fifth examples, the valve includes a first end plate and a second end plate coupled via a shaft, and wherein adjusting the valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core flow path, and the second cooler core flow path comprises activating a motor coupled to the shaft to rotate the shaft, the first end plate, and the second end plate. In a seventh example of the method, optionally including one or more or each of the first through sixth examples, the first cooler core flow path comprises a first cooler core of the EGR cooler and the second cooler core flow path comprises a second cooler core of the EGR cooler, and wherein adjusting the valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core flow path, and the second cooler core flow path comprises adjusting the valve of the EGR cooler to selectively block flow of the EGR through the bypass passage, the first cooler core, and the second cooler core.
The disclosure also provides support for a method for an engine system including an exhaust gas recirculation (EGR) cooler, comprising: during low EGR flow conditions where EGR cooling is demanded, directing EGR through only a first cooler core flow path of the EGR cooler and not through a second cooler core flow path of the EGR cooler, via a valve in a first position, and during high EGR flow conditions, directing EGR through both the first cooler core flow path and the second cooler core flow path, via the valve in a second position, where the valve, in the first position, seals the second cooler core flow path at both an upstream end and a downstream end of the second cooler core flow path. In a first example of the method, the method further comprises: during low EGR flow conditions where EGR cooling is not demanded, directing EGR through a bypass passage of the EGR cooler and not through the first cooler core flow path or the second cooler core flow path, via the valve in a third position. In a second example of the method, optionally including the first example, the method further comprises: during low differential pressure conditions, directing EGR through both the bypass passage and the second cooler core flow path and not through the first cooler core flow path, via the valve in a fourth position. In a third example of the method, optionally including the first and/or second examples, the valve is a rotary valve positioned at least partially within a housing of the EGR cooler, and further comprising moving the rotary valve to the first position, the second position, the third position, and/or the fourth position by rotating a motor-driven shaft coupling a first end plate of the rotary valve to a second end plate of the rotary valve. In a fourth example of the method, optionally including one or more or each of the first through third examples, the first cooler core flow path comprises a flow path through a first cooler core of the EGR cooler and the second cooler core flow path comprises a flow path through a second cooler core of the EGR cooler, wherein the rotary valve, in the first position, seals the second cooler core at both the upstream end and the downstream end of the second cooler core by positioning a first poppet valve of the first end plate in face-sharing contact with an outlet of the second cooler core and a second poppet valve of the second end plate in face-sharing contact with an inlet of the second cooler core, wherein the first end plate further includes a first opening and the second end plate further includes a second opening, and in the first position of the rotary valve, the first opening is aligned with an outlet of the first cooler core and the second opening is aligned with an inlet of the first cooler core. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, the method further comprises: adjusting an amount of EGR flowing into the EGR cooler by adjusting an EGR valve positioned upstream or downstream of the EGR cooler, and wherein the low flow EGR conditions include engine load being below a threshold load and wherein the high flow EGR conditions include engine load being above the threshold load.
The disclosure also provides support for a system, comprising: an exhaust gas recirculation (EGR) cooler positioned in an EGR passage coupled between an exhaust manifold and an intake manifold of an engine, the EGR cooler including: a housing, a first cooler core, a second cooler core, a bypass passage, each of the first cooler core, the second cooler core, the bypass passage positioned in the housing, and a rotary valve at least partially positioned in the housing, the rotary valve including a first end plate positioned in an outlet chamber of the EGR cooler and a second end plate positioned in an intake chamber of the EGR cooler, the first end plate and second end plate coupled to a motor via a common shaft and movable, via the motor, to four positions in order to block or allow flow of EGR through the first cooler core, the second cooler core, and the bypass passage. In a first example of the system, each of the first cooler core and the second cooler core includes a plurality of gas-flowing passages in thermal contact with a heat-transfer medium. In a second example of the system, optionally including the first example, the first cooler core includes a first outlet, the second cooler core includes a second outlet, and the bypass passage includes a third outlet, and the first end plate of the rotary valve includes a first opening, a second opening, a first poppet valve, and a second poppet valve, wherein the rotary valve is movable, via the motor, to selectively fluidly couple an outlet of the EGR cooler to the first outlet, the second outlet, and/or the third outlet via the first opening and the second opening and to selectively seal the first outlet, the second outlet, and/or the third outlet via the first poppet valve and the second poppet valve. In a third example of the system, optionally including the first and/or second examples, the first cooler core includes a first inlet, the second cooler core includes a second inlet, and the bypass passage includes a third inlet, and the second end plate of the rotary valve includes a third opening, a fourth opening, a third poppet valve, and a fourth poppet valve, wherein the rotary valve is movable, via the motor, to selectively fluidly couple an inlet of the EGR cooler to the first inlet, the second inlet, and/or the third inlet via the third opening and the fourth opening and to selectively seal the first inlet, the second inlet, and/or the third inlet via the third poppet valve and the fourth poppet valve. In a fourth example of the system, optionally including one or more or each of the first through third examples, the system further comprises: a controller storing instructions in non-transitory memory executable to: responsive to a first condition, activate the motor to move the rotary valve into a first position where the first inlet and the first outlet are each sealed, the second inlet and the second outlet are each sealed, and the third inlet is fluidly coupled to the inlet of the EGR cooler and the third outlet is fluidly coupled to the outlet of the EGR cooler, responsive to a second condition, activate the motor to move the rotary valve into a second position where the first inlet is fluidly coupled to the inlet of the EGR cooler and the first outlet is fluidly coupled to the outlet of the EGR cooler, the second inlet and the second outlet are each sealed, and the third inlet and the third outlet are each sealed, responsive to a third condition, activate the motor to move the rotary valve into a third position where the first inlet is fluidly coupled to the inlet of the EGR cooler and the first outlet is fluidly coupled to the outlet of the EGR cooler, the second inlet is fluidly coupled to the inlet of the EGR cooler and the second outlet is fluidly coupled to the outlet of the EGR cooler, and the third inlet and the third outlet are each sealed, and responsive to a fourth condition, activate the motor to move the rotary valve into a fourth position where the second inlet and the third inlet are each fluidly coupled to the inlet of the EGR cooler and the second outlet and the third outlet are each fluidly coupled to the outlet of the EGR cooler, and the first inlet and the first outlet are each sealed. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, the system further comprises: an EGR valve positioned in the EGR passage, and wherein the instructions are further executable to adjust a position of the EGR valve to control an amount of EGR flowing through the EGR passage and the EGR cooler.
Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations, and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with the electronic controller.
It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. Moreover, unless explicitly stated to the contrary, the terms “first,” “second,” “third,” and the like are not intended to denote any order, position, quantity, or importance, but rather are used merely as labels to distinguish one element from another. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.
As used herein, the term “approximately” is construed to mean plus or minus five percent of the range unless otherwise specified.
The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
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| 19936241 | Feb 2001 | DE |
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| 20220120243 A1 | Apr 2022 | US |
