Method for an exhaust gas recirculation (EGR) system with an EGR cooler and system for an engine in a vehicle

Abstract

Method for an exhaust gas recirculation (EGR) system with an EGR cooler (158) connected to an engine (10) in a vehicle, comprising: under selected operating conditions: Directing an initial amount of EGR through the cooler (158); Directing a second EGR quantity through a bypass (154) around the cooler (158) to a point downstream of the cooler (158) and upstream of an intake port inlet (42) to mix with the first EGR quantity and to create a first mixture of cooled EGR and uncooled EGR; Supplying the first mixture to the intake port (42) where it is mixed with fresh air to produce a second mixture; Adjustment of a first valve (156) based on a temperature of the first mixture (T mix1 ); and Adjustment of a second valve (152) based on a temperature of the second mixture (T mix,2 ).

Description

Technical field

[0001] The present application relates generally to a low-pressure exhaust gas recirculation system connected to an engine in a motor vehicle. Specifically, the application relates, on the one hand, to a method for an exhaust gas recirculation (EGR) system with an EGR cooler connected to an engine in a vehicle, and, on the other hand, to a system for an engine in a vehicle comprising an exhaust gas recirculation (EGR) system with an EGR cooler and an EGR cooler bypass, an EGR cooler bypass valve, and a control system. Background and Summary

[0002] It may be desirable to perform at least some low-pressure exhaust gas recirculation (LP-EGR) during the warm-up phase of the engine and catalytic converter to increase heat flow to the aftertreatment devices and reduce pump surge, while ensuring sufficient EGR is performed during warm-up to minimize NO xto control. However, EGR coolers can condense water, especially before the engine coolant temperature reaches its operating temperature (e.g., when the engine coolant is below its warmed-up operating temperature). This can be problematic with any EGR system, but water droplets formed in a low-pressure EGR circuit can be particularly degrading on an aluminum compressor wheel operating at high speed. One solution is to use only low-pressure EGR during selected coolant temperature ranges; however, this limits the amount of EGR that can be used due to intake manifold temperature and pump pulse limitations.

[0003] A method for reducing condensation is disclosed in US 7,469,691 B. In that document, EGR is routed through a bypass around an EGR cooler to an intake manifold of the engine. The EGR is then mixed with intake air in the intake manifold before mixing with cooled EGR. However, when cooled EGR is added shortly before the mixture enters a turbocharger compressor, a possibility of condensation remains in the gases entering the compressor.

[0004] Other exhaust gas recirculation systems are known from US 2007 10 144 501 A1 and US 2007 / 0 089 400 A1, which propose recirculating uncooled and cooled exhaust gases into the intake manifold at different points, such that the cooled exhaust gas is recirculated downstream of the uncooled exhaust gas. Alternatively, it is proposed that in a diesel engine, high exhaust gas temperatures be generated to heat the exhaust aftertreatment devices by maintaining cylinder pressures below ambient pressure for most of the intake stroke, thereby achieving rapid fuel vaporization and higher combustion temperatures.

[0005] In view of the problems described, the present invention proposes a method with the features of claim 1 and a system with the features of claim 9. Preferred embodiments of the invention are the subject of the dependent claims.

[0006] It is therefore proposed to route a first EGR quantity through the cooler and a second EGR quantity through a bypass around the cooler to a point downstream of the cooler and upstream of an intake manifold inlet. This second EGR quantity mixes with the first, creating a first mixture of cooled and uncooled EGR. This first mixture is then delivered to the intake manifold, where it is mixed with fresh air to create a second mixture. A first valve is adjusted based on the temperature of the first mixture, and a second valve is adjusted based on the temperature of the second mixture. These first and second valves can, in particular, be an EGR cooler bypass valve and a throttle connected to the intake manifold.

[0007] Low-pressure EGR (LP-EGR) can be desirable, for example, under cold start conditions where the coolant temperature is below a certain threshold. An EGR cooler bypass valve can be modified so that at least a portion of the EGR is routed around the EGR cooler and thus remains uncooled. This allows the temperature of the mixture of cooled and uncooled EGR, and therefore the temperature of the EGR entering the intake manifold, to be controlled so that it remains above a certain threshold. This reduces condensation, thereby minimizing the risk of compressor degradation due to condensation in the LP-EGR system during a cold engine start. Brief description of the drawings Fig. Figure 1 shows a schematic diagram of an engine with a turbocharger and an exhaust gas recirculation system. Fig. Figure 2 shows a block diagram of an engine that includes a low-pressure exhaust gas recirculation system with an exhaust gas recirculation cooler and a cooler bypass. Fig. Figure 3 shows a flowchart illustrating a control routine for a low-pressure exhaust gas recirculation system. Fig. Figure 4 shows a flowchart illustrating a different control routine for a low-pressure exhaust gas recirculation system. Detailed description

[0008] The following description concerns a method for an exhaust gas recirculation (EGR) system connected to a turbocharged engine in a motor vehicle. In one example, a proportional EGR cooler bypass is connected to a low-pressure EGR system to modulate the amounts of cooled and uncooled EGR. The amount diverted around the cooler (e.g., a certain amount of uncooled EGR) can be adjusted to control the mixture temperature downstream of the cooler, where the cooled and uncooled EGR are combined, to a desired temperature, for example, by means of a control system. In one example, the bypass value is adjusted to provide a mixture temperature high enough to reduce water condensation downstream of the mixing point. This can enable low-pressure EGR without reducing (e.g., when holding) the overall EGR rate at a desired overall EGR rate, even during engine and catalyst warm-up.In some embodiments, the mixture temperature of low-pressure EGR and intake air can also be controlled to further reduce condensate formation in the intake duct upstream of the compressor. For example, a throttle valve in the intake duct can be adjusted to control the mixture temperature of intake air and EGR, or a low-pressure EGR valve can be adjusted. The above approach can thus enable the use of low-pressure EGR at low coolant temperatures (e.g., during warm-up and while the coolant temperature is below a certain threshold) without causing any durability problems for the compressor.

[0009] With reference to now Fig. Figure 1 shows a schematic diagram of a cylinder of a multi-cylinder engine 10, which may be included in a propulsion system of a motor vehicle. The engine 10 can be controlled, at least partially, by a control system comprising a control unit 12, as well as by input from a vehicle operator 132 via an input device 130. In this example, the input device 130 comprises an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. A combustion chamber (i.e., cylinder) 30 of the engine 10 may comprise combustion chamber walls 32 with a piston 36 positioned therein. In some embodiments, the surface of the piston 36 in the cylinder 30 may have a recess. The piston 36 may be connected to a crankshaft 40, so that a reciprocating motion of the piston is converted into a rotary motion of the crankshaft.The crankshaft 40 can be connected to at least one drive wheel of a vehicle by means of an intermediate transmission system. Furthermore, a starter motor can be connected to the crankshaft 40 by means of a flywheel to enable the engine 10 to be started.

[0010] The combustion chamber 30 can draw in intake air from an intake manifold 44 via an intake port 42 and can discharge combustion gases via an exhaust port 48. The intake manifold 44 and the exhaust port 48 can communicate selectively with the combustion chamber 30 via an intake valve 52 and an exhaust valve 54, respectively. In some embodiments, the combustion chamber 30 can include two or more intake valves and / or two or more exhaust valves.

[0011] The inlet valve 52 can be controlled by the control unit 12 via an electric valve actuator (EVA) 51. Similarly, the exhaust valve 54 can be controlled by the control unit 12 via EVA 53. Alternatively, the adjustable valve actuator can be electro-hydraulic or another conceivable mechanism to enable valve actuation. Under certain conditions, the control unit 12 can modify the signals supplied to the actuators 51 and 53 to control the opening and closing of the respective inlet and exhaust valves. The position of the inlet valve 52 and the exhaust valve 54 can be determined by means of valve position sensors 55 and 57, respectively. In other embodiments, one or more of the inlet and exhaust valves can be actuated by one or more cams and can employ one or more systems of: cam profile switching (CPS), variable cam control (VCT), or variable cam timing (VCT).Variable Cam Timing (VCT), Variable Valve Timing (VVT), and / or Variable Valve Lift (VVL) are used to modify valve operation. For example, cylinder 30 may alternatively include an electrically actuated intake valve and a cam-actuated exhaust valve, including CPS and / or VCT.

[0012] A fuel injection device 66 for injecting fuel directly into the combustion chamber 30 proportionally to the pulse width of a signal FPW received by the control unit 12 via an electronic driver 68 is directly connected to the combustion chamber 30. In this way, the fuel injection device 66 provides a direct injection of fuel into the combustion chamber 30. The fuel injection device can be installed, for example, in the side of the combustion chamber or at the top of the combustion chamber. Fuel can be supplied to the fuel injection device 66 by means of a fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distribution pipe.

[0013] An ignition system 88 can supply a spark to the combustion chamber 30 under selected operating modes by means of a spark plug 92 in response to an advance ignition signal SA from the control unit 12. Even if spark ignition components are shown, the combustion chamber 30 or one or more other combustion chambers of the engine 10 can, in some embodiments, be operated in a compression ignition mode with or without a spark.

[0014] The intake duct 42 can include throttles 62 and 63 with throttle valves 64 and 65, respectively. In this particular example, the positions of the throttle valves 64 and 65 can be modified by the control unit 12 using signals supplied to an electric motor or an actuator included with the throttles 62 and 63, a configuration often referred to as electronic throttle control (ETC). In this way, the throttles 62 and 63 can be operated to modify the intake air supplied to the combustion chamber 30, along with other engine cylinders. The positions of the throttle valves 64 and 65 can be supplied to the control unit 12 by throttle position signals TP. The intake duct 42 can include an air flow meter 120 and a manifold pressure sensor 122 for supplying the respective MAF and MAP signals to the control unit 12.

[0015] Furthermore, in the disclosed embodiments, an exhaust gas recirculation (EGR) system can direct a desired portion of the exhaust gas from the exhaust port 48 to the intake port 44 via a high-pressure EGR (HP-EGR) port 140 and / or a low-pressure EGR (LP-EGR) port 150. The amount of EGR supplied to the intake port 44 can be varied by the control unit 12 using an HP-EGR valve 142 or an LP-EGR valve 152. In some embodiments, a throttle may be included in the exhaust port to assist in controlling the EGR. Furthermore, an EGR sensor 144 may be arranged in the EGR port and may provide an indication of one or more parameters of the exhaust gas pressure, temperature, and concentration. Alternatively, the EGR can be controlled by a calculated value based on signals from the MAF sensor (upstream), MAP (intake manifold), MAT (manifold gas temperature) and the crankshaft speed sensor.Furthermore, the EGR can be controlled based on an exhaust gas O2 sensor and / or an intake oxygen sensor (intake manifold). Under certain conditions, the EGR system can be used to regulate the temperature of the air-fuel mixture in the combustion chamber. Fig. Figure 1 shows a high-pressure EGR system in which EGR is routed from upstream of a turbocharger turbine to downstream of a turbocharger compressor, and a low-pressure EGR system in which EGR is routed from downstream of a turbocharger turbine to upstream of a turbocharger compressor. Further details are shown in Figure 1. Fig. As shown in Figure 1, the high-pressure EGR system can include a high-pressure EGR cooler 146, and the low-pressure EGR system can include a low-pressure EGR cooler 158, for example, to dissipate heat from the EGR gases to the engine coolant. In alternative embodiments, the engine 10 can include only a high-pressure EGR system or only a low-pressure EGR system.

[0016] Thus, the engine 10 can further include a compression device, for example a turbocharger or supercharger, which comprises at least one compressor 162 arranged along the intake manifold 44. In the case of a turbocharger, the compressor 162 can be driven at least partially by a turbine 164 (e.g., by means of a shaft) arranged along the outlet channel 48. In the case of a supercharger, the compressor 162 can be driven at least partially by the engine and / or an electric machine and might not include a turbine. Thus, the amount of compression supplied to one or more cylinders of the engine by means of a turbocharger or supercharger can be modified by the control unit 12.

[0017] An exhaust gas sensor 126 is shown connected upstream of a pollutant limitation system 70 and downstream of the turbine 164 to the exhaust port 48. The sensor 126 can be any suitable sensor for providing an indication of the air / fuel ratio of the exhaust gas, for example, a linear oxygen sensor or UEGO (universal or wideband exhaust gas oxygen), a dual-state oxygen sensor or EGO, a HEGO (heated EGO), or an NO x -, HC or CO sensor.

[0018] Emission control devices 71 and 72 are shown arranged along the exhaust channel 48 downstream of the exhaust gas sensor 126. The devices 71 and 72 can be a selective catalytic reduction (SCR) system, a three-way catalyst (TWC), or a NOₓ sensor. x-filter, various other pollutant control devices, or combinations thereof. For example, device 71 may be a TWC, and device 72 may be a particulate filter (PF). In some embodiments, the PF 72 may be positioned downstream of the TWC 71 (as in Fig. 1 shown), while in other embodiments the PF 72 may be positioned upstream of the TWC 72 (not in Fig. 1 shown). Furthermore, in some embodiments, during the operation of engine 10, the pollutant limiting devices 71 and 72 can be regularly reset by operating at least one cylinder of the engine in a specific air / fuel ratio.

[0019] Control unit 12 is in Fig. Figure 1 is shown as a microcomputer comprising: a microprocessor 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 106, a working memory 108, a battery-powered memory 110, and a data bus. The control system 12 can receive various signals from sensors coupled to the engine 10, in addition to the signals already described, including: a measurement of the mass airflow (MAF) from an air flow meter 120; engine coolant temperature (ECT) from a temperature sensor 112 connected to a cooling jacket 114; a timing profile sensor (PIP) signal from a Hall sensor 118 (or another type) connected to the crankshaft 40; a throttle position (TP) signal from a throttle position sensor; and a manifold absolute pressure (MAP) signal from a sensor 122.An engine speed signal (RPM) can be generated by control unit 12 from the PIP signal. The manifold pressure signal (MAP) from a manifold pressure sensor can be used to provide an indication of vacuum or pressure in the intake manifold. It should be noted that various combinations of the aforementioned sensors can be used, for example, a MAF sensor without a MAP sensor, or vice versa. During stoichiometric operation, the MAP sensor can provide an indication of engine torque. Furthermore, this sensor, together with the detected engine speed, can provide an estimate of the charge (including air) being drawn into the cylinder. In one example, sensor 118, which is also used as an engine speed sensor, can generate a predetermined number of evenly spaced pulses per crankshaft revolution.

[0020] The storage medium read-only memory 106 can be programmed with machine-readable data that constitutes instructions executable by the processor 102 to perform the procedures described below, as well as other variants that are considered but not explicitly listed.

[0021] As described above, Fig. 1 only one cylinder of a multi-cylinder engine and that each cylinder can analogously include its own set of inlet / outlet valves, fuel injection device, spark plug, etc.

[0022] With reference to Fig. Figure 2 schematically shows another exemplary embodiment of an engine with a low-pressure exhaust gas recirculation system. In particular, the one shown in Fig. The configuration shown in 2 is a vehicle system 6 comprising a low-pressure EGR system having a cooler 158 with a bypass 154. The vehicle system 6 further comprises an internal combustion engine 10 connected to a transmission 14, which was described above with particular reference to Fig. The transmission 14 can be a manual transmission, an automatic transmission, or a combination thereof, as described in Figure 1. Furthermore, it can include various additional components, such as a torque converter and / or other transmissions, for example, an axle drive, etc. The transmission 14 is shown connected to a drive wheel 16, which in turn is in contact with the road surface 13.

[0023] Furthermore, the vehicle system 6 can include an outlet channel 48, which ultimately leads to a (in Fig. 2 (not shown) tailpipe, which ultimately directs exhaust gas to the atmosphere. As described above, the exhaust channel 48 of the vehicle system 6 can include one or more emission control devices, for example, a three-way catalytic converter 71 and a particulate filter 72. The vehicle system 6 can further include a turbocharger with a compressor 162, which is at least partially driven by a turbine 164 arranged along the exhaust channel 48 as described above.

[0024] The vehicle system 6 can include a control system 41. The control system 41 is shown to have a control unit 12, which receives information from several sensors 61 (various examples of which are described herein) and sends control signals to several actuators 81 (various examples of which are described herein). For example, the sensors 61 can include a temperature sensor 159 located in the low-pressure EGR system for determining the temperature of a mixture of cooled and uncooled EGR. As another example, actuators 81 can include control valves, such as the low-pressure EGR valve 152 and the throttle 63 in the intake manifold 44.

[0025] Furthermore, in the disclosed embodiments, an exhaust gas recirculation (EGR) system can direct a desired portion of the exhaust gas from the exhaust port 48 upstream of the turbine 164 to the intake port 44 via an EGR port 140, with the exhaust gas entering the intake port 44 downstream of the compressor 162. Thus, the EGR system can be a high-pressure EGR system (HP-EGR system). The amount of HP-EGR supplied to the intake manifold 44 can be varied by the control unit 12 via the HP-EGR valve 142 in response to engine operating conditions, such as engine speed, engine load, etc. The HP-EGR port 140 can include an EGR cooler 146, which is connected to a cooling system of the vehicle (in Fig. 2 not shown) is connected and can lower the temperature of the exhaust gas flowing through the high-pressure EGR channel.

[0026] Furthermore, another exhaust gas recirculation system can direct a desired portion of exhaust gas from the exhaust duct 48 downstream of the turbine 164 to the intake duct 44 upstream of the compressor 162 via an EGR channel 150; thus, the EGR system can be a low-pressure EGR (LP-EGR) system. The total amount of LP-EGR supplied to the intake duct 44 can be varied by the control unit 12 via the LP-EGR valve 152 in response to engine operating conditions. The LP-EGR channel 150 can include a cooler 158 equipped with a (in Fig. 2 (not shown) the vehicle's cooling system for dissipating heat from EGR gases to the engine coolant.

[0027] Furthermore, the low-pressure EGR system can include a bypass 154 for routing exhaust gas around the EGR cooler 158 to a point in the low-pressure EGR channel 150 located downstream of the EGR cooler 158 and upstream of a connection to the intake channel 42. The low-pressure EGR system can also include a bypass valve 156, which can be controlled by the control unit 12 to modulate the amount of exhaust gas flowing through the bypass 154 (e.g., the bypass valve 156 can be opened to allow 60% of the total low-pressure EGR to flow into the bypass 154 and 40% of the total low-pressure EGR to flow into the cooler 158). In this way, some of the low-pressure EGR can remain uncooled and thus at a higher temperature than the low-pressure EGR flowing through the cooler 158. The low-pressure EGR system may also include one or more sensors for measuring the exhaust gas temperature. Although in Fig. 2 only temperature sensor 159 for determining the temperature of the mixture of cooled and uncooled EGR (T mix,1As shown, the ND-EGR system can alternatively use sensors to determine the temperature of the exhaust gas before it enters the EGR cooler 158 (T in ), a temperature of the exhaust gas after it leaves the cooler 158 (T out ) etc. include, through which T mix,1 for example, it could be estimated.

[0028] Exemplary control routines for a low-pressure exhaust gas recirculation system connected to an engine, for example, the one described above with reference to Fig. 1 and Fig. The ND-EGR systems described in section 2, which are connected to engine 10, are in Fig. 3 and Fig. 4 shown. Fig. Figure 3 illustrates a routine for controlling the temperature of a first mixture of cooled and uncooled low-pressure EGR. Fig. Figure 4 illustrates a routine for controlling a second mixture of low-pressure EGR and fresh air in the engine's intake manifold.

[0029] Referring first to Fig. Figure 3 shows a routine 300 for controlling a first mixture temperature in a low-pressure exhaust gas recirculation (LP-EGR) system. Specifically, routine 300 controls the EGR flow through an LP-EGR cooler based on a desired mixture temperature of cooled and uncooled EGR.

[0030] At step 310 of routine 300, it is determined whether the engine is under cold start conditions or whether the ambient temperature (e.g., the temperature outside the vehicle) is lower than a threshold temperature. As defined herein, "cold start" implies that the engine is started under conditions where the engine has cooled down to ambient temperatures, which may be relatively hot or cold. Furthermore, the engine coolant temperature may be below a threshold during cold start conditions (e.g., the temperature at which a thermostat opens). If it is determined that the engine is under cold start conditions or that the ambient temperature is below the threshold temperature, routine 300 advances to step 312, where it is determined whether the temperature of the initial mixture (T1) is below the threshold temperature. mix,1) is lower than a desired temperature. The desired temperature can be based, for example, on the instantaneous engine coolant temperature or the ambient temperature and the percentage of low-pressure EGR flow to the total flow (including fresh air). In other examples, the desired temperature can be adjusted based on an instantaneous low-pressure EGR coolant temperature. In some embodiments, the first mixture temperature can be measured by a temperature sensor positioned in the low-pressure EGR system. In other embodiments, the temperature of the exhaust gas entering the cooler and the temperature of the EGR exiting the cooler, as well as the amounts of EGR flowing through the bypass and the cooler, can be used to determine the temperature of the cooled and uncooled EGR mixture.If it is determined that the engine is not under cold start conditions or that the ambient temperature is not lower than the threshold temperature, or if T. mix,1 If the desired temperature is exceeded, the routine moves from 300 to 324, where the engine operation continues under the current operating parameters.

[0031] If, on the other hand, it is determined that T mix1IIf the temperature is lower than the desired temperature, routine 300 proceeds to 314, where it determines whether the bypass valve of the low-pressure EGR cooler is open (e.g., whether exhaust gas is being routed through the bypass). If the bypass valve is not open, routine 300 advances to 316, where the bypass valve is opened. If it is determined that the bypass valve is open, routine 300 moves to 320, where it determines whether the bypass valve is open to a maximum extent. As stated herein, "the bypass valve is open to a maximum extent" implies that the cooler's bypass valve is in such a position that a maximum amount of exhaust gas flows through the bypass, and essentially no exhaust gas flows through the EGR cooler.In some embodiments, depending on the design of the cooler bypass, opening the bypass valve at a maximum value might not significantly block the flow through the cooler, but rather open the bypass, which may be the path of least resistance; thus, the flow through the bypass line is maximized.

[0032] As soon as the bypass valve opens at 316, or if it is determined at 320 that the bypass valve is not open at a maximum amount, routine 300 moves from Fig. 3 to 318, where the bypass valve is based on the temperature of the mixture of cooled and uncooled EGR (T mix,1 ) is adjusted. For example, the opening of the bypass valve can be increased to allow more exhaust gas to flow through the bypass (and less exhaust gas to flow through the EGR cooler), thereby increasing T mix,1 is raised.

[0033] In some examples, if it is determined that the bypass valve is open at its maximum value, routine 300 continues to 322, where the low-pressure EGR valve is adjusted to control the total amount of exhaust gas entering the low-pressure EGR system to address water condensation. For example, the low-pressure EGR valve can be adjusted to reduce the total amount of low-pressure EGR if the bypass valve is open at its maximum value and T mix,1 The temperature is still below the desired level. This reduces the total amount of low-pressure EGR because the mixture temperature cannot reach the desired value, increasing the likelihood of condensation.

[0034] The bypass valve can be adjusted as described above to provide the desired mixture temperature, which can be determined from the coolant temperature or ambient temperature, while maintaining a desired overall low-pressure EGR flow rate. This reduces the formation of condensate in the low-pressure EGR channel, which would otherwise have difficulty evaporating before entering the turbocharger compressor. In some embodiments, the overall low-pressure EGR flow rate can be adjusted if the desired temperature is not reached and the bypass valve is open to a maximum extent. As described below, the low-pressure EGR valve or a throttle in the intake duct can also be adjusted to control the temperature of a secondary mixture comprising the primary mixture and fresh air.

[0035] Fig. Figure 4 shows a flowchart illustrating Routine 400 for controlling the temperature of a secondary mixture of low-pressure EGR and fresh air. Specifically, based on the current temperature of the secondary mixture and a desired temperature, Routine 400 controls the low-pressure EGR valve and a throttle in the intake manifold.

[0036] At step 410 of routine 400, it is determined whether the engine is under cold-start conditions or whether the ambient temperature is below a threshold temperature. As mentioned above, "cold start" implies that the engine is being started under conditions where it has cooled down to ambient temperatures, which can be relatively hot or cold. If it is determined that the engine is under cold-start conditions, or if the ambient temperature is below the threshold temperature, routine 400 advances to step 412, where it is determined whether the temperature of a secondary mixture (Ta) is below the threshold temperature.mix,2The second mixture can consist of the first mixture (e.g., the mixture of cooled and uncooled low-pressure EGR) and fresh air from outside the vehicle. In some embodiments, the temperature of the second mixture can be measured by a temperature sensor in the intake manifold. In other embodiments, the temperature of the second mixture can be determined based on the amounts of fresh air and EGR in the mixture and their respective temperatures. Furthermore, the desired temperature of the second mixture can be such that no condensate can form in the intake manifold upstream of the compressor when intake air (e.g., fresh air) is combined with the mixture of cooled and uncooled low-pressure EGR. Thus, the desired temperature can be based on the dew point of the air temperature in the intake manifold.If it is determined that the engine is not under cold start conditions, or if the ambient temperature exceeds a threshold, or if T. mix,2 If the temperature is greater than the desired temperature, routine 400 moves to 428, where the engine operation continues with the current operating parameters.

[0037] If, on the other hand, it is determined that T mix,2If the temperature is lower than the desired temperature, routine 400 moves to 414, where it is determined whether the bypass valve is open to its maximum extent. If, as described above, the bypass valve is open to its maximum extent, a maximum amount of exhaust gas flows through the bypass, and essentially no exhaust gas flows through the EGR cooler. If the bypass is not open to its maximum extent, routine 400 moves to 430, where the opening of the bypass is increased (e.g., more exhaust gas flows through the bypass). In this way, the first mixture contains a larger amount of uncooled EGR, and the temperature of the second mixture can be raised.

[0038] If at 414 of routine 400 in Fig. If it is determined that the bypass valve is open to a maximum extent, routine 400 advances to 416, where it is determined whether the low-pressure EGR valve is open to a maximum extent (e.g., whether a maximum amount of low-pressure EGR flows through the low-pressure EGR system). If it is determined that the low-pressure EGR valve is not open to a maximum extent, the routine advances to 418, where the low-pressure EGR quantity is increased. In this way, a larger quantity of the first mixture, which can be controlled to a desired temperature, can be added to the second mixture, thereby raising the temperature of the second mixture.

[0039] If, on the other hand, the ND-AGR valve is open at a maximum value, routine 400 moves from Fig. From step 4 to 420, it is determined whether the throttle is open at its maximum extent. If the throttle is open at its maximum extent, a maximum amount of fresh air from outside the vehicle flows into the intake manifold. Thus, the throttle does not need to be modulated to increase the amount of fresh air in the secondary mixture. If it is determined that the throttle is open at its maximum extent, the routine moves from step 400 to 424, where the total amount of low-pressure EGR is reduced. In some examples, a low-pressure EGR rate based on the amount of low-pressure EGR may be increased to maintain a total EGR rate. In this way, the amount of low-pressure EGR entering the intake manifold is reduced, and the possibility of condensation upstream of the compressor can be reduced.

[0040] If, however, the throttle is not open at its maximum value, routine 400 advances to 422, where it is determined whether the ambient temperature is greater than a second threshold. If the ambient temperature is not greater than the second threshold, increasing the amount of fresh air in the second mixture can lower its temperature rather than raise it, thus helping to achieve the desired temperature. If the ambient temperature is lower than the second threshold, routine 400 moves to 424, where, as described above, the amount of low-pressure EGR is reduced.

[0041] If it is determined that the ambient temperature is greater than a second threshold temperature, routine 400 proceeds. Fig.4 to 426 continues, where the throttle opening is increased. The amount by which the throttle opening is increased can depend, for example, on the humidity of the fresh air and / or the desired temperature of the second mixture. In this way, the temperature of the second mixture (T) can be controlled. mix,2 ) be raised to reduce the possibility of condensation forming upstream of the compressor.

[0042] This reduces condensation and degradation of the turbocharger compressor while still utilizing low-pressure exhaust gas recirculation (LPEG) during cold starts or periods when the ambient temperature is below a certain threshold. As described above, the LPEG system can include a bypass with a controllable valve to divert at least some exhaust gas around the EGR cooler within the LPEG system. This allows the cooled and uncooled EGR mixture temperature to be controlled to a desired level. Furthermore, the LPEG valve and / or a throttle can be adjusted to control the temperature of the LPEG / fresh air mixture in the intake manifold, further reducing the possibility of condensation upstream of the compressor in the engine's intake manifold.

[0043] In another embodiment, to maintain the mixture temperature above the desired mixture temperature, a first step would be to reduce the high-pressure EGR quantity (with the option of correspondingly increasing the low-pressure EGR to maintain the desired overall EGR rate or the desired intake oxygen concentration at the target value). Then, as a second step, if reducing the low-pressure EGR causes the mixture of cooled and uncooled EGR (T mix,1 If the airflow falls below a certain threshold, the intake throttle can be used to reduce the intake airflow.

[0044] It is understood that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The specific routines described herein can represent one or more different processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various operations, steps, or functions shown can be executed in the sequence shown, in parallel, or, in some cases, omitted. Similarly, the processing sequence is not strictly necessary to realize the features and benefits of the exemplary embodiments described herein, but is provided for better illustration and description. One or more of the operations or functions shown can be executed repeatedly, depending on the strategy employed.Furthermore, the described work processes can graphically represent a code to be programmed into the machine-readable storage medium in the engine control system.

[0045] It is understood that the configurations and routines disclosed herein are exemplary and that these specific embodiments should not be considered limiting, as numerous modifications are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed-piston, and other engine designs. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions, and / or properties disclosed herein.

Claims

[1] Method for an exhaust gas recirculation (EGR) system with an EGR cooler (158) connected to an engine (10) in a vehicle, comprising: under selected operating conditions: Directing an initial amount of EGR through the cooler (158); Directing a second EGR quantity through a bypass (154) around the cooler (158) to a point downstream of the cooler (158) and upstream of an intake port inlet (42) to mix with the first EGR quantity and to create a first mixture of cooled EGR and uncooled EGR; Supplying the first mixture to the intake port (42) where it is mixed with fresh air to produce a second mixture; Adjustment of a first valve (156) based on a temperature of the first mixture (T mix1 ); and Adjustment of a second valve (152) based on a temperature of the second mixture (T mix,2 ). [2] Method according to claim 1, characterized by , that the first valve (156) is an EGR cooler bypass valve and that adjusting the bypass valve modulates the amount of bypass EGR in the first mixture. [3] Method according to claim 1, characterized by , that the second valve (152) is a throttle connected to the intake port (42) and that adjusting the throttle modulates the amount of fresh air in the second mixture. [4] Method according to claim 1, characterized by , that the second valve (152) is an EGR valve and that adjusting the EGR valve modulates an overall EGR flow rate and an amount of the first mixture in the second mixture. [5] Method according to claim 1, characterized by , that selected operating conditions include engine cold start. [6] Method according to claim 1, characterized by , that selected operating conditions include EGR coolant temperature and a desired temperature of the first mixture (T mix,1) is based on the EGR coolant temperature. [7] The method of claim 1, which further includes estimating the temperature of the first mixture (T mix,1 ) based on an exhaust gas quantity flowing through the bypass (154) and an exhaust gas quantity flowing through the EGR cooler (158) and a temperature of exhaust gas entering the EGR cooler (158) and a temperature of exhaust gas exiting the EGR cooler (158). [8] The method of claim 1, which further includes estimating the temperature of the second mixture (T mix,2 ) based on a quantity and temperature of intake air and a quantity and temperature of the first mixture (T mix,1 ) includes. [9] System for an engine (10) in a vehicle, comprising: an exhaust gas recirculation (EGR) system with an EGR cooler (158) and an EGR cooler bypass; an EGR cooler bypass valve; a control system comprising a machine-readable storage medium, wherein the medium contains commands for: Directing an initial amount of EGR through the cooler (158); Directing a second EGR quantity through the bypass (154) to a point downstream of the cooler (158) and upstream of the intake manifold inlet (42) to create a first mixture of cooled EGR and uncooled EGR; Supplying the first mixture to the intake port (42) where it is mixed with fresh air to form a second mixture; Adjustment of a first valve (156) based on a temperature of the first mixture (T mix,1 ); and Adjustment of a second valve (152) based on a temperature of the second mixture (T mix,2 ) under selected conditions. [10] System according to claim 9, characterized by, that the first valve (156) is the cooler bypass valve and adjusting the cooler bypass valve modulates an amount of bypass EGR in the first mixture. [11] System according to claim 9, characterized by , that selected operating conditions include cold start and a coolant temperature below a threshold temperature. [12] System according to claim 9, which further comprises commands to adjust a flow rate of the total EGR when the bypass valve is in a maximum position and the temperature of the second mixture (T mix,2 ) is lower than desired, wherein the bypass (154) receives a maximum amount of exhaust gas when the bypass valve is in a maximum position, and wherein the second valve (152) is an EGR valve. [13] System according to claim 9, which further comprises commands to adjust the second valve (152) when a temperature of the second mixture (T mix,2) is lower than desired, and wherein the second valve (152) is a throttle in the intake port (42) positioned upstream of the EGR system.

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