INTRUSIVE EGR MONITOR FOR A HYBRID VEHICLE

Abstract

Method for controlling an EGR system in a hybrid vehicle (100) comprising the following: Increasing the EGR flow through an EGR valve (42) when the sum of a first difference between a first and a second measured MAP and a second difference between a first and a second derived MAP is below a first threshold, and Reducing the EGR flow through the EGR valve (42) when the sum of the first difference and the second difference exceeds a second threshold.

Description

[0001] The present disclosure relates to systems and methods for monitoring exhaust gas recirculation systems in hybrid vehicles.

[0002] Exhaust gas recirculation (EGR) systems are used in motor vehicles to recirculate a controlled portion of the engine's exhaust gases into the engine's intake manifold to reduce emissions and improve fuel efficiency. Such systems typically use an EGR valve located between the engine's exhaust manifold and intake manifold. When in an open position, the valve allows a portion of the exhaust gases to be recirculated from the exhaust side of the engine to the intake side. In such systems, the EGR flow rate to the intake manifold is varied according to one or more conditions, such as engine temperature, the charge of air entering the intake manifold, and engine speed.

[0003] It is desirable to monitor the operation of an EGR system using onboard diagnostic software to determine whether the system is functioning as expected. One approach to EGR monitoring in vehicles involves the use of a non-intrusive monitor. The non-intrusive EGR monitor requires operation at low load and high load with low EGR quantities. These operating points are inefficient, and hybrid engine operation typically avoids them, thus preventing the non-intrusive monitor from completing a diagnostic test. In contrast, an intrusive monitor only requires the highly efficient mid-load points to complete a diagnostic test. However, in hybrid vehicles, the test results can be corrupted by variable camshaft timing (VCT).

[0004] An onboard EGR diagnostic program can be confused by rapid VCT adjustments. Rapid VCT changes cause a manifold filling delay such that the mass airflow (MAF) into the intake manifold and the manifold absolute pressure (MAP) do not follow each other. In non-hybrid vehicles, VCT is not used aggressively, meaning that highly delayed valve timing is not used often and the rate of valve timing change is typically small. Therefore, the delay issue has not been shown to significantly impair the accuracy of onboard EGR diagnostic programs in non-hybrid vehicles. However, in hybrid vehicles, more aggressive use of VCT, both with highly delayed valve timing and rapid valve timing change rates, can be taken into account.Therefore, there is a need to provide a robust and systematic means for monitoring EGR systems in hybrid vehicles.

[0005] The prior art is known from US Patent 6,257,214 B1. This describes a method for controlling an EGR system based on a difference between a first and a second measured MAP and a first and a second derived MAP.

[0006] US 4 173 205 A describes a method for controlling an EGR system, whereby the EGR flow through an EGR valve is either increased or decreased based on a difference between a measured MAP and a threshold value.

[0007] The purpose of the invention is to provide a reliable diagnostic method for exhaust gas recirculation systems in hybrid vehicles that works precisely despite variable and fast camshaft control.

[0008] The problem is solved by the features of the independent patent claim.

[0009] Advantageous embodiments of the invention are described in the dependent claims.

[0010] A system and method for monitoring an exhaust gas recirculation (EGR) system in a hybrid vehicle, which uses an intrusive monitor, are disclosed. The system and method may include the use of measured manifold absolute pressure (MAP) and derived MAP to determine the operational capability of the EGR system. Embodiments may also include adjusting the EGR flow through the EGR valve to compensate for clogging and throttling of the EGR valve. Embodiments of this disclosure may be used in various EGR control applications where improvements in detecting the operational capability of the EGR system are desired.

[0011] In one embodiment, a hybrid vehicle comprises a machine, a MAP sensor connected to an intake manifold of the machine, and a MAF sensor connected to an inlet of the machine's intake manifold. The hybrid vehicle also comprises an EGR line connected to the machine's intake manifold and an exhaust manifold, the EGR line having an EGR valve configured to recirculate exhaust gas from the exhaust manifold into the machine's intake manifold. The hybrid vehicle further comprises a control device communicating with the machine, the MAP sensor, the MAF sensor, and the EGR valve. The control device is configured to increase the EGR flow through the EGR valve when the sum of the first difference between a first and a second measured MAP and the second difference between a first and a second derived MAP is below a first threshold value.The control device is also configured to reduce the EGR flow through the EGR valve if the sum of the first difference and the second difference exceeds a second threshold.

[0012] In another embodiment, a method for monitoring an EGR system in a hybrid vehicle includes increasing the EGR flow through an EGR valve when the sum of a first difference between a first and a second measured MAP and a second difference between a first and a second derived MAP is below a first threshold. The method also includes decreasing the EGR flow through the EGR valve when the sum of the first difference and the second difference exceeds a second threshold. The first measured MAP and the second measured MAP can be based on a pressure signal generated by a sensor located in an engine's intake manifold. Similarly, the first derived MAP and the second derived MAP can be based on the mass airflow in the engine's intake manifold, measured by a sensor connected to an inlet of the intake manifold.Additionally, the first measured MAP and the first derived MAP are recorded when the EGR valve is in an open position, and the second measured MAP and the second derived MAP are recorded when the EGR valve is in a closed position.

[0013] In yet another embodiment, a method for monitoring an EGR system includes acquiring a first and second measured MAP and a first and second derived MAP when the camshaft timing position change is below a corresponding threshold. The method also includes storing a diagnostic code when the sum of the first difference between the first and second measured MAP and the second difference between the first and second derived MAP is below a first threshold and greater than a second threshold. The method may further include increasing an adaptive parameter by a predetermined factor to increase the EGR flow when the sum is below a third threshold, and decreasing the adaptive parameter by the predetermined factor to decrease the EGR flow when the sum exceeds a fourth threshold.The procedure may involve activating an indicator within the vehicle if the sum of the first difference and the second difference is below the first threshold and greater than the second threshold. The indicator may be a light, a sound, and / or a message.

[0014] Various embodiments according to the present disclosure may provide one or more associated advantages. For example, the use of an intrusive EGR monitor according to embodiments of the present disclosure does not depend on the operation of the machine at inefficient low-load and high-load operating points and is therefore more suitable for hybrid vehicle applications. Embodiments according to the present disclosure also avoid the complexity and potential precision deficiencies associated with compensating for VCT position measurements by invalidating tests in which the VCT position changes near the end of the test.

[0015] The advantages listed above, as well as further advantages and features, are clearly evident from the following detailed description, either alone or in conjunction with the accompanying drawings. Fig.Figure 1 is a schematic representation of a single cylinder of an internal combustion engine in accordance with embodiments of the present disclosure; Fig. Figure 2 is a schematic representation of a hybrid electric vehicle (HEV) which has both an electric motor and an internal combustion engine for propulsion in accordance with embodiments of the present disclosure; Fig. 3a is a plotter representation of the intake manifold absolute pressure (MAP) and load with EGR ON and EGR OFF in accordance with embodiments of the present disclosure; Fig. 3b is a plotter representation of the mass airflow (MAF) through an intake of the machine and load with EGR ON and EGR OFF in accordance with embodiments of the present disclosure; the Fig. 4a and Fig.4b are plotter representations illustrating the average pressure difference between a functional and a non-functional EGR system in accordance with embodiments of the present disclosure; the Fig. 5a, Fig. 5b and Fig. 5c illustrate the relationship between variance (noise), measured MAP and derived MAP in accordance with embodiments of the present disclosure; Fig. Figure 6 is a flowchart illustrating a control system and / or a method for monitoring an EGR system in a hybrid vehicle in accordance with an embodiment of the present disclosure.

[0016] As required, detailed embodiments of the claimed subject matter are disclosed here. However, it must be understood that the disclosed embodiments are only exemplary and can be implemented in various and alternative forms. The figures are not necessarily to scale; certain features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed here should therefore not be interpreted as limiting, but only as a representative basis for instructing a person skilled in the art on different uses of embodiments of the claimed subject matter.

[0017] With reference to Fig. 1, an internal combustion engine 10, which has a plurality of cylinders, one of which is in Fig.Figure 1 shows the control device 12 being controlled by the control device. The control device 12 can be implemented, for example, by an electronic control unit (ECU) and / or a powertrain control module (PCM). The control device 12 is in Fig.1 shown as a conventional microcomputer, comprising: microprocessor unit (CPU) 60, input / output interfaces 62, read-only memory (ROM) 64, random access memory (RAM) 66 and a conventional data bus 68.The control device 12 is shown receiving several signals from sensors connected to the machine 10, in addition to the signals discussed above, including: a mass airflow (MAF) signal from the mass airflow sensor 70, which is connected to the intake manifold 22 upstream of the throttle 38; a manifold absolute pressure (MAP) measurement from the pressure sensor 72; an intake manifold temperature (MT) signal from the temperature sensor 74; an engine coolant temperature (ECT) from the temperature sensor 78, which is connected to the cooling sleeve 80; and a profiled ignition pulse (PIP) signal from the Hall effect sensor 82, which is connected to the crankshaft 20 and is used as an engine speed signal, generating a predetermined number of evenly spaced pulses per revolution of the crankshaft. A barometer 76 for measuring the barometric pressure BP is also included.

[0018] The machine 10 has a combustion chamber 14 and cylinder walls 16 with pistons 18 positioned therein and connected to the crankshaft 20. The combustion chamber 14 is shown connected to the intake manifold 22 and the exhaust manifold 24 via the intake valve 26 and the exhaust valve 28, respectively. A cam 29, belonging to a camshaft (not shown), actuates the exhaust valve 28 when the tip of the cam 29 presses down on the exhaust valve 28. Similarly, the cam 29 actuates the intake valve 27. The control of the intake valve 27 can be varied by a variable cam timing (VCT) device 31.

[0019] The intake manifold 22 can have a fuel injector 30 connected to it for supplying fuel to the engine cylinders. Fuel is supplied to the fuel injector 30 by a conventional fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distribution system. Alternatively, the engine can be configured such that the fuel is injected directly into the engine cylinder, a configuration known to those skilled in the art as a direct injection engine. The intake manifold 22 is connected to the throttle body 34 via the throttle valve 36. The throttle position sensor 38 measures the angular position of the throttle valve 36 and transmits a throttle position signal to the control device 12.

[0020] The ignition system 50 supplies a spark to the combustion chamber 14 via the spark plug 52. Bistable exhaust gas oxygen sensors 54 and 58 are connected to the exhaust manifold 24, respectively, upstream and downstream of the catalytic converter 56. The sensors 54 and 58 each supply the signals EGO1 and EGO2 to the control device 12, which can convert these signals into signals with two states: one state indicating that the exhaust gases are richer than a reference air / fuel ratio, and the other state indicating that the exhaust gases are leaner than the reference air / fuel ratio.

[0021] An activated carbon canister 84 is connected to the intake 22 via a drain valve 90. Fuel vapors displaced from the fuel tank during filling (not shown) enter the activated carbon canister 84 through the inlet 88. The fuel is absorbed by activated carbon pellets 86 in the activated carbon canister 84, and air is released into the environment through the opening 92. When the machine 10 is operating, the valve 90 can be opened. The vacuum in the intake 22 draws ambient air through the activated carbon canister 84 via the opening 92. The ambient air strips the fuel vapors from the activated carbon pellets 86 into the intake 22 and into the combustion chamber 14 to be burned. In this way, the activated carbon canister 84 is emptied so that the activated carbon pellets 86 can absorb fuel vapor when air loaded with fuel vapors is introduced into the activated carbon canister 84 during a refueling event.In one embodiment, the valve 90 is a solenoid valve that can be controlled to assume a position between fully open and fully closed by providing a pulse-width modulated signal. Based on the control to valve 90 and on a pressure difference between the intake 22 and atmospheric pressure (BP), the amount of air drawn into the machine 10 through the activated carbon canister 84 can be estimated.

[0022] The machine 10 also features an exhaust gas recirculation (EGR) system to return a controlled proportion of the exhaust gases generated by the machine 10 from an exhaust manifold 24 to the intake manifold 22 via an EGR line 44. The amount of exhaust gas recirculated from the exhaust manifold to the intake manifold can be controlled by an EGR valve 42, which is controlled by a conventional DC stepper motor 94 that receives EGR_RATE_DES signals from the control device 12. This allows the EGR valve 42 to be moved axially in steps such that its position relative to an inlet 48 connected to the intake manifold 22 is controlled.

[0023] The MAF sensor 70 is located upstream of the inlet 48 to the intake manifold 22, and the MAP sensor 72 is located downstream of the inlet 48. The MAF sensor 70 only measures fresh air supplied to the engine 10; that is, it does not measure the EGR flow. However, a signal from the MAP sensor 72 is affected by EGR. A derived MAP can be calculated based on the signal from the MAF sensor 70, a PIP signal indicating engine speed, and an engine displacement (known). The measured MAP (pressure measured by a MAP sensor) and the derived MAP can be used to determine whether the EGR system is operating correctly. A method for deriving pressure in the intake manifold based on air mass flow is also disclosed in US patents numbered 5,654,501 and 5,331,936, granted to the proprietor of the present disclosure and hereby incorporated by reference.

[0024] Machine 10, as in Fig. Shown in 1, it can be part of a powertrain system for a hybrid electric vehicle (HEV) 100, as schematically shown in Fig. Figure 2 shows that the front wheels are connected to a front axle 102. A differential and a final drive gear set 104 are also connected to the front axle 102. The vehicle drivetrain system is connected to the differential 104 via a transmission 106. The transmission 106 is connected to an electric motor 110 via a clutch 108. The electric motor 110 is connected to the machine 10 via a clutch 114. In the embodiment shown in Figure 2, the front wheels are connected to a front axle 102. The differential and a final drive gear set 104 are also connected to the front axle 102. The vehicle drivetrain system is connected to the differential 104 via a transmission 106. The transmission 106 is connected to an electric motor 110 via a clutch 108. The electric motor 110 is connected to the machine 10 via a clutch 114. Fig.As shown in Figure 2, a chain drive 112 is provided between the machine 10 and the electric motor 110 such that the machine 10 rotates along a first axis and the electric motor 110 and the gearbox 106 rotate along a second axis, essentially parallel to the first axis. The electric motor 110 can operate as a motor that supplies torque to the associated axis or as a generator that absorbs torque from the associated axis, that is, provides a braking force on wheels belonging to the axis. The electric motor 110 is connected to the high-voltage battery 116, which acts as a source and sink of electrical energy. The control device 12 is shown connected to the machine 10, the gearbox 106, the electric motor 110, the clutch 114, and the high-voltage battery 116. The configuration in Figure 2 is shown in Figure 2. Fig.Figure 2 simply illustrates an HEV configuration. There are many alternatives for configuring an HEV that do not deviate from the scope of this disclosure.

[0025] It is desirable to monitor the operation of an EGR system to determine whether it is functioning as expected. Additionally, effective EGR monitoring systems and procedures are helpful in determining when the EGR valve begins to throttle. Increased clogging or EGR valve throttling is a consequence of the engine operating with EGR at colder temperatures, which is typical for improved fuel economy in hybrid vehicles. The EGR flow rate through the EGR valve can be adjusted to extend its service life. The overall functionality of the EGR system can be determined using the various systems and procedures described below.

[0026] With reference to Fig. 3a. As the percentage load (MAP / BP) increases (that is, as the manifold absolute pressure (MAP) approaches barometric pressure (BP)), the difference between the measured MAP with EGR OFF and EGR ON approaches zero. In other words, MAP sensor data alone do not provide an accurate indication of system operability at high loads. One solution is to use both measured and inferred MAP data to determine EGR system operability. As described above, the measured MAP can be determined from the signal transmitted by a MAP sensor, and the inferred MAP can be calculated from a signal from a MAF sensor, a PIP signal indicating engine speed, and engine displacement. As described in Fig.As shown in Figure 3b, the MAF measured with EGR ON is substantially different from the MAF measured with EGR OFF as the percentage load increases. Essentially, adding EGR at low load substantially changes the MAP but does not significantly change the MAF, whereas adding EGR at high load does not significantly change the MAP but significantly changes the MAF.

[0027] With reference to Fig.Figure 4a shows a plotter representation illustrating the mean pressure difference between a functional (unrestricted curve) and a non-functional (fully restricted curve) EGR system when the measured MAP is the only data source. It can be seen that both the functional and non-functional EGR systems could have values ​​between 0.5 and 2.0 in Hg. This can result in an inaccurate indication of the EGR system's operating status, leading to unnecessary visits to repair shops and customer dissatisfaction. In accordance with the embodiments of the present disclosure, one solution to this problem is to add the mean pressure difference between the measured MAP, determined with the EGR ON and OFF positions, to the mean pressure difference between the derived MAP, calculated with the EGR ON and OFF positions. By adding the two mean pressure differences, the Fig.The overlap area shown in 4a is substantially reduced, as shown in the plotter representation of the Fig. 4b shown, which in turn improves the precision of the status indicators of the EGR system.

[0028] This tax strategy is used in the Fig. Figures 5a-5c further illustrate the variance or noise in the pressure difference data using measured MAP and derived MAP. As shown in the Fig. 5a and Fig. As shown in Figure 5b, when the mean pressure difference is used from either measured MAP or inferred MAP, the variance or noise lies essentially above the range from an unthrottled to a fully throttled EGR passage. However, when the mean pressure difference from both measured MAP and inferred MAP is added, the variance or noise is essentially reduced, as shown in Figure 5b. Fig.Figure 5c illustrates this. The reduction in variance makes it less likely that normal operation of the EGR system will result in an inaccurate diagnostic code or other indicator triggered by a pressure difference between EGR ON and EGR OFF that lies within an interval created by a first pressure threshold and a second pressure threshold.

[0029] Furthermore, the EGR position and the corresponding flow rate can be adjusted to compensate for any clogging or throttling in the EGR valve and / or EGR line. A desired EGR valve position can be determined from an EGR valve transfer function, FN_EGRPOS, which is based on a pressure ratio across the EGR valve and a desired EGR mass flow rate. In particular, the required number of engine steps to achieve a desired EGR flow rate can be determined by taking engine output step values ​​from a table corresponding to the EGR valve transfer function. See, for example, the table below. Output of the table is EGR EGR position (steps) Output of the table is EGR EGR mass (pounds / min) 0.6 52 52 52 52 52 52 0.6 0.6 0.6 0.3 0 0.4 30 30 30 52 52 40 0.5 0.5 0.5 0.25 0 0.3 23 23 23 52 52 30 0.4 0.4 0.4 0.2 0 0.2 18 18 18 30 52 20 0.25 0.25 0.25 0.15 0 0.1 10 10 10 18 52 10 0.1 0.1 0.1 0.06 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0.25 0.5 0,75 0 0 0.25 0.5 0.75 1 FN_EGRPOS FN_EGRMAS

[0030] The table values ​​are determined empirically through dynamometer machine tests. The pressure ratio across the valve, egr_pres_rat, is on the horizontal axis of the table, and the desired EGR flow rate is on the vertical axis. Therefore, the table shows the output values ​​of the current EGR mass flow, FN_EGRMASS, with egr_pres_rat on the horizontal axis and the EGR valve position on the vertical axis. The output table is delimited, if necessary, to a maximum value corresponding to the total number of steps the engine can take (for example, 52 steps). The desired EGR valve position can be adjusted by adding an adaptive parameter, egr_step_adapt, to the EGR valve transfer function to compensate for any EGR valve throttling. The normal EGR valve movement can thus be increased or decreased depending on the current engine conditions.A method describing the use of an EGR valve transfer function to achieve a desired EGR position is disclosed in more detail in US Patent No. 6,098,602, granted to the proprietor of the present disclosure and hereby incorporated by reference.

[0031] With reference to Fig. Figure 6 shows a flowchart describing the operation of an EGR monitoring system for a hybrid vehicle in accordance with an exemplary embodiment of the present disclosure. As the average person skilled in the art understands, the functions described in Fig. The functions shown in Figure 6 are executed by software and / or hardware, depending on the specific application and implementation. The various functions can be performed in an order or sequence that differs from that shown in Figure 6. Fig.Figure 6 illustrates how, depending on the specific execution strategy, such as event-driven, interrupt-driven, etc., the functions may be executed. Similarly, one or more steps or functions may be executed repeatedly, in parallel, and / or omitted under specific operating conditions or in specific applications, although this is not explicitly illustrated. In one embodiment, the illustrated functions are implemented primarily by software, instructions, or code stored in a computer-readable memory device and executed by one or more microprocessor-based computers or control devices to control the operation of the vehicle.

[0032] In particular, leads to Fig.6. A control device at 200 initiates a diagnostic test. The control device stops the test at 204 to collect several values ​​of the measured MAP and derived MAP over a specified number of loops, n. The control device then determines whether the machine conditions are suitable to continue the diagnostic program as shown in blocks 204-208, and if so, the data are collected a specified number of times, as shown in blocks 210-218, and averaged at block 216. The machine conditions include maintaining the machine speed and torque 204, acquiring the current machine speed, throttle position, and VCT position 206, and checking that any change in machine speed, throttle position, and VCT is below a corresponding threshold 208. If any change in machine speed, throttle position, or VCT exceeds a corresponding threshold at 208, the diagnostic test is aborted.The test then records or stores the initial machine speed, throttle position and VCT at 220 and returns to the beginning of the test at 200.

[0033] The measured (P ON ) and derived (P ON ( INF MAP data is acquired at 210 with the EGR valve open when the engine conditions at 208 are met. The EGR valve is then closed at 212, and the measured (P OFF ) and derived (P OFF ( INF MAP data is then acquired at 214. The EGR valve is reopened at 216. The pressure difference between the measured MAP with the EGR OFF and ON (P diff = P ON - P OFF ) and the pressure difference between the derived MAP with the EGR OFF and ON (P diff(INF) = P ON ( INF ) - P OFF ( INFThe values ​​are calculated at 218. The process is repeated a predetermined number of times (n loops) as long as the machine states are maintained. After the data has been collected during the specified interval, the control device calculates the mean difference of the measured MAP (P). diff(AVG) ) and the derived MAP (P diff(INF)AVG ) over the interval (n cycles) at 222.

[0034] If at block 224 the sum of the mean difference between measured MAP and derived MAP (P diff(AVG) + P diff(INF)AVG ) is smaller than a first threshold (P THRESH1 ) and greater than a second threshold (P THRESH2An EGR system operating state is confirmed at blocks 228 and 230. If the engine states remain sufficiently constant during the test, the test is considered valid by decision block 230, and a diagnostic code corresponding to the operating state is set at block 232. If the engine states do not remain substantially constant, the diagnostic procedure is repeated as shown in block 234. Various other control actions may be performed based on the set diagnostic code or a diagnostic code stored at block 232, such as activating an in-vehicle indicator to warn a driver, for example, using a light, sound, and / or message, and / or adjusting the EGR valve transfer function at block 236, as explained in more detail below.

[0035] If the sum is not within the interval defined by the first and second threshold values, the diagnostic program exits at block 226 and the control unit continues with block 236. The control unit adjusts the EGR flow rate based on the sum of the mean difference between measured MAP and derived MAP (Pr). diff(AVG) + P diff(INF)AVG ), as shown at blocks 236 and 238. If the test results show that the EGR valve is beginning to throttle, the EGR flow rate is increased. In particular, if the sum of the mean pressure differences (P diff(AVG) + P diff(INF)AVGIf the sum of the mean pressure differences is below a third threshold, the EGR flow rate can be increased by incrementally increasing egr_step_adapt by a predetermined factor (for example, 5) 236 and added to the EGR valve transfer function 238. Likewise, if the sum of the mean pressure differences exceeds a fourth threshold, the EGR flow rate can be decreased by incrementally decreasing egr_step_adapt by a predetermined factor (for example, 5), and this can be added to the EGR valve transfer function 238. The parameter egr_step_adapt can be limited to a maximum value corresponding to the total steps of the engine and stored in the KAM (battery-powered memory for diagnostic information in motor vehicles) 238. After adjusting the EGR flow rate, the diagnostic test ends at 240. By adjusting the flow of exhaust gases through the EGR valve into the intake manifold. The service life of the EGR valve can be extended.

[0036] The use of an intrusive EGR monitor according to embodiments of the present disclosure therefore does not depend on the operation of the machine at inefficient low-load and high-load operating points and is thus more suitable for hybrid vehicle applications. Embodiments according to the present disclosure also avoid the complexity and potential precision deficiencies associated with compensating for VCT position measurements by invalidating tests in which the VCT position changes near the end of the test.

[0037] It is clear that the invention is not limited to the exact EGR control methods illustrated and discussed in this disclosure, but that various modifications can be made without departing from the meaning and scope of the invention.

[0038] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are descriptive and not limiting, and it must be understood that various modifications can be made without departing from the meaning and scope of the invention. Furthermore, the features of the different embodiments can be combined to form further embodiments of the disclosure. Although the best mode has been described in detail, the person skilled in the art will recognize various alternative designs and embodiments within the scope of the following claims.Although various embodiments have been described as offering advantages or being preferable to other embodiments or implementations with respect to one or more desired features, the person skilled in the art recognizes that one or more features may be compromised in order to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to: cost, strength, durability, life-cycle costs, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Embodiments discussed here that are described as less desirable than other embodiments or implementations with respect to one or more features are therefore not outside the scope of the disclosure and may be desirable for certain applications.

Claims

Method for controlling an EGR system in a hybrid vehicle (100) comprising: increasing the EGR flow through an EGR valve (42) when the sum of a first difference between a first and a second measured MAP and a second difference between a first and a second derived MAP is below a first threshold, and decreasing the EGR flow through the EGR valve (42) when the sum of the first difference and the second difference exceeds a second threshold. Method according to claim 1, wherein the first measured MAP and the second measured MAP are based on a pressure signal generated by a sensor (72) positioned in an intake pipe (22) of a machine (10). Method according to claim 1, wherein the first derived MAP and the second derived MAP are based on air mass flow into an intake manifold (22) of a machine (10) which is measured by a sensor (70) connected to an inlet (48) of the intake manifold (22). Method according to claim 1, wherein the first measured MAP and the first derived MAP are obtained when the EGR valve (42) is in an open position, and the second measured MAP and the second derived MAP are obtained when the EGR valve (42) is in a closed position. Method according to claim 4, wherein the first measured MAP, the second measured MAP, the first derived MAP and the second derived MAP are acquired and averaged over a predetermined number of cycles. Method according to claim 5, wherein the first measured MAP, the second measured MAP, the first derived MAP and the second derived MAP are acquired and averaged while input states are maintained. The method of claim 6, wherein the input states are as follows: 1) machine speed is kept substantially constant, 2) machine torque is kept substantially constant, 3) a change in machine speed is below a corresponding threshold, 4) a change in throttle is below a corresponding threshold, and 5) a change in camshaft control position is below a corresponding threshold.

Images