EGR differential pressure sensor auto calibration method

• US 7,474,954 B1
• Filed: 08/23/2007
• Issued: 01/06/2009
• Est. Priority Date: 08/23/2007
• Status: Expired due to Fees

• Current Assignee: Detroit Diesel Corporation (Mercedes-Benz Group AG)
• Original Assignee: Detroit Diesel Corporation (Mercedes-Benz Group AG)
• Inventors: Zagone, Peter
• Primary Examiner(s): KWON, JOHN
• Application Number:
  US11/843,853
• Time in Patent Office: 502 Days
• Field of Search: 701/101, 701/108, 701/114, 701/115, 123/568.11, 123/568.12, 123/568.21, 123/568.22, 123/568.16, 731/146.9, 731/147.4, 731/147.6
• US Class Current: 701/108
• CPC Class Codes: F02D 2041/0075 by using flow sensors
• 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 41/1448 the characteristics being an exhaust gas pressure
• CPC Class Codes: F02D 41/2441 characterised by the learning conditions
• CPC Class Codes: F02D 41/2474 Characteristics of sensors
• CPC Class Codes: F02M 26/46 for determining the characteristics of gases, e.g. composition
• CPC Class Codes: F02M 26/47 the characteristics being temperatures, pressures or flow rates
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for operating an electronic controlled internal combustion engine with an electronic control unit (ECU) having at least nonvolatile memory and tables resident therein to automatically recalibrate an exhaust gas recirculation (EGR) differential pressure sensor.

Claims

1. A method for operating an electronic controlled internal combustion engine with an electronic control unit (ECU) having at least nonvolatile memory and tables resident therein to automatically recalibrate an exhaust gas recirculation (EGR) differential pressure sensor:

determining whether a drive-cycle is completed;

simultaneously determining engine status, EGR differential pressure sensor status, engine coolant temperature;

determining actual zero offset by observing EGR differential pressure sensor output;

determining whether actual zero offset is within acceptable limits; and

storing actual zero offset in nonvolatile memory.

2. The method of claim 1, wherein said drive cycle is determined by an ignition stature going from on to off.

3. The method of claim 1, wherein said EGR status is determining whether said EGR differential pressure sensor is enabled and whether said EGR differential pressure sensor is not fixed.

4. The method of claim 1, wherein said engine status includes simultaneously determining whether said engine has run a predetermined calibratable period of time;

whether engine speed has gone from non zero to zero, and whether engine speed remains zero for a predetermined calibratable period of time.

5. The method of claim 4, further including determining whether engine shut down protection and idle shut down programs are operating.

6. The method of claim 1, further including no auto calibration of said EGR differential pressure sensor, logging a fault, actuating a warning alert and storing a minimal zero offset in nonvolatile memory when said actual zero offset is outside predetermined calibratable acceptable limits.

7. The method of claim 5, further including no auto calibration of said EGR Differential pressure sensor if at least one of EGR differential pressure sensor is not enabled or is fixed, engine speed is not zero, engine speed has not gone from non zero to zero, engine has not been running longer than a preset time, engine protection shutdown is operating or engine idle shutdown is operating.

8. The method of claim 1 further includes setting a counter in said ECU for debouncing EGR leak fault until said faults occur a predetermined number of times.

9. The method of claim 1, wherein auto calibrating said EGR differential pressure sensor occurs at said drive cycle end.

10. The method of claim 1 further includes performing auto calibration of said EGR differential pressure sensor when engine ignition is on if auto calibration is enabled, auto calibration at ignition off is disabled, ignition is on, engine speed is zero, coolant temperature is greater than an auto calibrated minimum coolant temperature and said EGR differential pressure sensor is not failed.

11. The method of claim 1, further including

logging a fault that remains active during current and subsequent drive cycles until a successful auto calibration of said EGR differential Pressure Sensor occurs.

12. The method of claim 1, further including auto calibrating said EGR Differential Pressure Sensor in response to a command from a service tool when said ignition is on, a command is reviewed by the ECU from a service tool to auto calibrate said EGR differential pressure sensor engine speed is zero and said EGR differential pressure sensor has not failed.

13. The method of claim 1, further including determining whether EGR differential pressure sensor voltages are within a differential pressure zero minimum and a differential pressure maximum to compute the EGR differential pressure.

14. The method of claim 13, further including generating an active fault, shutting off EGR engine operation mode and setting the EGR differential pressure sensor error back to zero when the differential pressure counts are outside a differential pressure zero minimum and differential pressure zero maximum range.

15. The method of claim 1, further including operating the engine in boost mode when a fault is logged.