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DE-102014204624-B4 - INTRUSIVE EGR MONITOR FOR A HYBRID VEHICLE

DE102014204624B4DE 102014204624 B4DE102014204624 B4DE 102014204624B4DE-102014204624-B4

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.

Inventors

  • Douglas Raymond Martin
  • Richard Paul Taylor
  • Freeman Gates

Assignees

  • FORD GLOBAL TECHNOLOGIES, LLC

Dates

Publication Date
20260513
Application Date
20140313
Priority Date
20130315

Claims (7)

  1. Method for controlling an EGR system in a hybrid vehicle (100) comprising: increasing the EGR flow through an EGR valve (42) when a 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.
  2. Procedure 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).
  3. Procedure according to Claim 1 , wherein the first derived MAP and the second derived MAP are based on mass airflow into an intake manifold (22) of a machine (10) measured by a sensor (70) connected to an inlet (48) of the intake manifold (22).
  4. Procedure 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.
  5. Procedure according to Claim 4 , wherein the first measured MAP, the second measured MAP, the first inferred MAP and the second inferred MAP are collected and averaged over a predetermined number of cycles.
  6. Procedure according to Claim 5 , wherein the first measured MAP, the second measured MAP, the first derived MAP and the second derived MAP are collected and averaged while input states are maintained.
  7. Procedure according to 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.

Description

The present disclosure relates to systems and methods for monitoring exhaust gas recirculation systems in hybrid vehicles. 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. 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). 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 synchronize. In non-hybrid vehicles, VCT is not used aggressively, meaning that highly delayed valve timing is not frequently used and the rate of valve timing change is typically small. Therefore, the delay issue has not been shown to significantly affect the accuracy of onboard EGR diagnostic programs in non-hybrid vehicles. However, in hybrid vehicles, more aggressive use of VCT, both with highly delayed control and rapid valve timing change rates, can be expected. Therefore, there is a need to provide a robust and systematic means of monitoring EGR systems in hybrid vehicles. Based on the current state of the art, the US 6 257 214 B1 known. 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. The 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. 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. The problem is solved by the features of the independent patent claim. Advantageous embodiments of the invention are described in the dependent claims. 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. 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. 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 de