Diagnosis of sensor failure in airflow-based engine control system

• US 8,521,354 B2
• Filed: 08/12/2008
• Issued: 08/27/2013
• Est. Priority Date: 08/12/2008
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Sasaki, Shizuo
• Primary Examiner(s): Nguyen, Kim T
• Application Number:
  US12/190,354
• Publication Number:
  US 20100042284A1
• Time in Patent Office: 1,841 Days
• Field of Search: 701/29, 701/35, 701/102, 701/29.1, 701/29.7, 701/30.5, 60601-603, 123/435, 123/304
• US Class Current: 701/29.1
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 2200/0402 the parameter being determined by using a model of the engine intake or its components
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: F02D 41/144 Sensor in intake manifold
• CPC Class Codes: F02D 41/18 by measuring intake air flow
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An air-flow based control system for an internal combustion engine has various sensors that are used to calculate various control commands. By comparing pairs of values calculated from different sensors, errors in connection with the sensors can be detected.

Claims

1. A method of diagnosing failure in connection with a mass airflow sensor used in an airflow-based engine control system for an internal combustion engine, the engine having one or more cylinders and an exhaust gas recirculation (EGR) system that recirculates exhaust at a variable EGR rate, comprising:

obtaining a measured airflow mass value from the mass airflow sensor;

obtaining a measured intake oxygen concentration value;

obtaining a measured exhaust oxygen concentration value;

calculating an EGR rate based on the relationship between the intake oxygen concentration value and the exhaust oxygen concentration value;

obtaining a measured intake manifold pressure value;

obtaining a measured intake manifold temperature value;

calculating a total gas flow rate into the cylinders, based on the measured intake pressure value and the measured intake manifold temperature value;

subtracting the EGR rate from the total gas flow rate, thereby obtaining a calculated value for a mass air flow rate, which is not based on the measured airflow mass value;

comparing the measured airflow mass value to the calculated airflow mass value; and

generating airflow mass sensor failure data if the comparing step does not result in a match.

2. The method of claim 1, further comprising the steps of accessing a mapped EGR rate from a stored EGR map, and of generating airflow mass failure data only if the calculated EGR rate and the mapped EGR rate are matched.

3. The method of claim 1, wherein the measured intake oxygen concentration value is measured by a first oxygen sensor in the air intake line and the measured exhaust oxygen concentration value is measured by a second oxygen sensor in the exhaust line.

4. A method of diagnosing failure in connection with an intake oxygen sensor or exhaust oxygen sensor of an engine having an exhaust gas recirculation (EGR) system that recirculates exhaust at a variable EGR rate, and having a control system that uses an EGR base map to determine the EGR rate, comprising:

calculating a first calculated EGR rate by subtracting a measured intake air flow rate from a total as flow rate into the cylinders;

obtaining a measured intake oxygen concentration value using the intake oxygen sensor;

obtaining a measured exhaust oxygen concentration value using the exhaust oxygen sensor;

calculating a second calculated EGR rate based on the relationship between the intake oxygen concentration value and the exhaust oxygen concentration value;

accessing the EGR base map stored in memory of the control system, the map providing EGR rates for given engine operating conditions, such that for a current operating condition the EGR rate provided by the map is the EGR rate used to control the EGR rate of the engine; and

comparing the first calculated EGR rate and the second calculated EGR rate with the EGR rate provided by the EGR base map for the same engine speed and intake O2 mass value; and

if the first calculated EGR rate and EGR rate provided by the EGR base map match each other but do not match the second calculated EGR rate, generating data indicating failure of the intake oxygen sensor or the exhaust oxygen sensor.