Induction diagnostics for skip fire engine

• US 9,835,522 B2
• Filed: 10/21/2015
• Issued: 12/05/2017
• Est. Priority Date: 10/23/2014
• Status: Active Grant

• Current Assignee: Tula Technology, Incorporated
• Original Assignee: Tula Technology, Incorporated
• Inventors: Chen, Shikui Kevin, Kotwicki, Allan J., Van Ess, Joel D., Bailey, Robert S., Pirjaberi, Mohammad R.
• Primary Examiner(s): Gray, Francis
• Application Number:
  US14/919,385
• Publication Number:
  US 20160116371A1
• Time in Patent Office: 776 Days
• CPC Class Codes: F02D 2200/101 Engine speed
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/221 relating to the failure of actuators or electrically driven elements
• CPC Class Codes: F02M 35/1038 for temperature or pressure
• CPC Class Codes: G01M 15/05 by combined monitoring of two or more different engine parameters
• CPC Class Codes: G01M 15/09 by monitoring pressure in fluid ducts, e.g. in lubrication or cooling parts

Abstract

A variety of methods and arrangements for detecting failure of the commanded air induction in an internal combustion engine are described. In some embodiments, the intake manifold pressure is monitored. An air induction event generates a fluctuation in the intake manifold pressure, which is recorded. The signal is processed through a diagnostic filter to help determine whether the actual induction matched the commanded induction. In other embodiments, measured crankshaft acceleration is compared with estimated crankshaft acceleration. If the two quantities differ by a threshold amount an induction fault is detected. The two detection methods may also be combined. The describe approaches are particularly well suited for use in engines operating in a skip fire mode with cylinder deactivation and/or a dynamic firing level modulation mode.

Claims

1. A method of detecting an induction fault of a cylinder in an internal combustion engine having an intake manifold, the method comprising:

operating the engine in a skip fire mode using an engine control unit, the engine control unit including a firing timing determining unit arranged for determining the timing of working chamber firings of the engine when operating in the skip fire mode;

sensing the intake manifold pressure and generating an intake manifold pressure signal indicative of the intake manifold pressure;

filtering the intake manifold pressure signal to reduce low frequency signal components of the intake manifold pressure signal;

comparing the filtered intake manifold pressure signal or a processed version of the filtered intake manifold pressure signal to a fault threshold; and

generating a fault signal when an induction fault is detected, wherein the induction fault detection is based at least in part on a determination that the filtered intake manifold pressure signal or the processed version of the filtered intake manifold pressure signal has passed the fault threshold,

wherein the fault signal is generated when the engine is operating in the skip fire mode.

2. A method as recited in claim 1 wherein a complementary filter is used to filter the intake manifold signal.

3. A method as recited in claim 1 wherein the fault signal is generated during the same engine cycle in which the fault occurs.

4. A method as recited in claim 1 wherein the induction fault indicates the failure of an intake valve to open as desired.

5. A method as recited in claim 1 wherein the fault threshold is a valve activation failure threshold and the fault signal is generated when the filtered manifold pressure signal or the processed version of the filtered intake manifold pressure signal exceeds the valve activation failure threshold, whereby the induction fault indicates that an intake valve failed to open when it was expected to open.

6. A method as recited in claim 1 wherein the fault threshold is a valve deactivation failure threshold and the fault signal is generated when the filtered manifold pressure signal or the processed version of the filtered intake manifold pressure signal falls below the valve deactivation failure threshold, whereby the induction fault indicates that an intake valve opened when the intake valve was intended to remain closed.

10. A method as recited in claim 1 wherein the filtered intake manifold pressure signal has a zero centered output.

11. A method as recited in claim 2 wherein the filtering further comprises summing an output of the complementary filter with a delayed output of the complementary filter to obtain the filtered manifold pressure signal.

7. An engine control unit arranged to control the operation of an engine, the engine control unit including an induction fault detection unit, the induction fault detection unit comprising:

a filter arranged to filter an intake manifold pressure signal indicative of an intake manifold pressure to reduce low frequency signal components of the intake manifold pressure signal;

a comparator that compares the filtered intake manifold pressure signal to a fault threshold; and

wherein the induction fault detection unit is configured to generate a fault signal when an induction fault is detected, wherein the induction fault detection is based at least in part on a determination that filtered intake manifold pressure signal has passed the fault threshold,

wherein the induction fault corresponds to a valve lift fault in which an intake valve opens but fails to open a desired amount.

8. An engine control unit as recited in claim 7 wherein the fault threshold is a valve lift too low threshold and the fault signal is generated when the filtered manifold pressure signal or the processed version of the filtered intake manifold pressure signal exceeds the valve lift too low threshold, whereby the induction fault indicates that an intake valve lift was lower than intended.

9. An engine control unit as recited in claim 7 wherein the fault threshold is a valve lift too high threshold and the fault signal is generated when the filtered manifold pressure signal or the processed version of the filtered intake manifold pressure signal falls below the valve lift too high threshold, whereby the induction fault indicates that an intake valve lift was higher than intended.

12. An engine control unit arranged to control the operation of an engine, comprising:

a skip fire module configured to direct operation of the engine in a skip fire operating mode, the skip fire module further comprising a firing timing determining unit arranged to determine the timing of working chamber firings when the engine is operated in the skip fire operating mode,

a filter arranged to filter an intake manifold pressure signal indicative of an intake manifold pressure to reduce low frequency signal components of the intake manifold pressure signal;

a comparator that compares the filtered intake manifold pressure signal or a processed version of the filtered intake manifold pressure signal to a fault threshold; and

an induction fault detection unit is configured to generate a fault signal when an induction fault is detected, wherein the induction fault detection is based at least in part on a determination that filtered intake manifold pressure signal or a processed version of the filtered intake manifold pressure signal has passed the fault threshold,

wherein the induction fault detection unit is further configured to detect induction faults while the engine is operated in the skip fire operating mode.

13. An engine control unit as recited in claim 12 wherein the filter includes a complementary filter.

14. An engine control unit as recited in claim 12 wherein the filter includes cascaded first and second first order low pass filters that filter the intake manifold pressure signal and a subtractor arranged to subtract the output of low pass filters from the intake manifold pressure signal to produce the filtered intake manifold pressure signal.

15. An engine control unit as recited in claim 13 wherein the filter further comprises an adder arranged to sum an output of the complementary filter with a delayed output of the complementary filter to obtain the filtered intake manifold pressure signal.

16. An engine control unit as recited in claim 12 wherein the filtered intake manifold pressure signal has a zero centered output.

20. An engine control unit as recited in claim 12 wherein the engine control unit includes a processor and the functionality of the induction fault detection unit is embodied in computer code executing on the processor.

17. An engine control unit as configured to direct operation of an engine in a dynamic firing level modulation mode, the engine control unit further comprising a firing timing determining unit arranged to determine the magnitude of working chamber firings when the engine is operated in the dynamic firing level modulation mode, the engine control unit further including:

a filter arranged to filter an intake manifold pressure signal indicative of an intake manifold pressure to reduce low frequency signal components of the intake manifold pressure signal;

a comparator that compares the filtered intake manifold pressure signal to a fault threshold; and

an induction fault detection unit configured to generate a fault signal when an induction fault is detected, wherein the induction fault detection is based at least in part on a determination that filtered intake manifold pressure signal has passed the fault threshold,

wherein the induction fault detection unit is configured to detect induction faults while the internal combustion engine is operated in the dynamic firing level modulation mode.

24. An engine control unit as recited in claim 17, wherein the induction fault detection unit is configured to generate the fault signal during the same engine cycle in which a fault occurs.

18. An engine control unit arranged to control the operation of an engine, the engine control unit including an induction fault detection unit, the induction fault detection unit comprising:

a filter arranged to filter an intake manifold pressure signal indicative of an intake manifold pressure to reduce low frequency signal components of the intake manifold pressure signal;

a comparator that compares the filtered intake manifold pressure signal to a fault threshold; and

wherein the induction fault detection unit is configured to generate a fault signal when an induction fault is detected, wherein the induction fault detection is based at least in part on a determination that filtered intake manifold pressure signal has passed the fault threshold,

wherein the induction fault detection unit is configured to generate the fault signal during the same engine cycle in which a fault occurs.

19. An engine control unit arranged to control the operation of an engine, the engine control unit including an induction fault detection unit, the induction fault detection unit comprising:

a filter arranged to filter an intake manifold pressure signal indicative of an intake manifold pressure to reduce low frequency signal components of the intake manifold pressure signal;

a comparator that compares the filtered intake manifold pressure signal to a fault threshold; and

wherein the induction fault detection unit is configured to generate a fault signal when an induction fault is detected, wherein the induction fault detection is based at least in part on a determination that filtered intake manifold pressure signal has passed the fault threshold,

wherein the induction fault detected by the induction fault detection unit is selected from the group consisting of;

a valve activation failure indicative of the failure of an intake valve to open when the valve is expected to open;

a valve deactivation failure indicative of the failure of the intake valve to remain closed when the valve is intended to be kept closed;

a valve lift too low failure indicative of the intake valve lift being lower than intended; and

a valve lift too high threshold indicative of the intake valve lift being higher than intended.

21. An induction fault detection unit for detecting induction faults in an internal combustion engine having an intake manifold, the induction fault detection unit comprising a filter arranged to filter an intake manifold pressure signal to reduce low frequency signal components of the intake manifold pressure signal, the induction fault detection unit being further configured to compare the filtered intake manifold pressure signal or a processed version of the filtered intake manifold pressure signal to a fault threshold and to generate a fault signal when an induction fault is detected,

wherein the induction fault detection is based at least in part on a determination that filtered intake manifold pressure signal or a processed version of the filtered intake manifold pressure signal has passed the fault threshold,

wherein the induction faults detected by the induction fault detection unit is selected from the group consisting of:

a valve activation failure indicative of the failure of an intake valve to open when the valve is expected to open;

a valve deactivation failure indicative of the failure of the intake valve to remain closed when the valve is intended to be kept closed;

a valve lift too low failure indicative of the intake valve lift being lower than intended; and

a valve lift too high threshold indicative of the intake valve lift being higher than intended.

22. An induction fault detection unit as recited in claim 21 wherein the filter includes a complementary filter.

23. An induction fault detection unit as recited in claim 22 wherein the filter further comprises an adder arranged to sum an output of the complementary filter with a delayed output of the complementary filter to obtain the filtered intake manifold pressure signal.