Method and system for knock sensor diagnostic

• US 10,156,220 B1
• Filed: 02/08/2018
• Issued: 12/18/2018
• Est. Priority Date: 02/08/2018
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Dudar, Aed
• Primary Examiner(s): Nguyen, Hung Q
• Assistant Examiner(s): MO, XIAO EN
• Application Number:
  US15/891,946
• Time in Patent Office: 313 Days
• CPC Class Codes: F02D 35/027 using knock sensors
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/042 for stopping the engine
• CPC Class Codes: F02D 41/065 at hot start or restart F02D41/067 takes precedence
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: F02N 11/0814 comprising means for controlling automatic idle-start-stop
• CPC Class Codes: F02N 11/0829 related to special engine control, e.g. giving priority to engine warming-up or learning
• CPC Class Codes: F02N 19/005 Aiding engine start by starting from a predetermined position, e.g. pre-positioning or reverse rotation
• CPC Class Codes: F02N 2019/008 the engine being stopped in a particular position
• CPC Class Codes: F02P 23/04 Other physical ignition means, e.g. using laser rays
• CPC Class Codes: F02P 5/1506 with particular means during starting
• CPC Class Codes: F02P 5/1526 with means for taking into account incorrect functioning of the pinking sensor or of the electrical means
• CPC Class Codes: F02P 7/077 Circuits therefor, e.g. pulse generators
• CPC Class Codes: G01L 23/221 for detecting or indicating knocks in internal combustion engines
• CPC Class Codes: G01M 15/11 by detecting misfire
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Methods and systems are provided for diagnosing a knock sensor of an engine system by actively inducing knock in an engine cylinder. A laser ignition device is operated in an engine cylinder located closest to the knock sensor while the engine is at rest and with the cylinder parked with an intake valve and an exhaust valve closed to generate and trap heat in the cylinder. Spark timing is advanced in the cylinder on the subsequent restart, which in combination with the trapped heat induces knock, and elicits a response from a functional knock sensor.

Claims

1. A method for an engine, comprising:

inducing a knock event in a cylinder via operation of a laser ignition device; and

diagnosing a knock sensor based on knock sensor output following the induced knock event.

2. The method of claim 1, further comprising, selecting the cylinder based on a position of the cylinder relative to a position of the knock sensor on an engine block.

3. The method of claim 2, wherein the selecting includes selecting the cylinder that is closest to the knock sensor relative to remaining engine cylinders.

4. The method of claim 1, wherein the diagnosing includes indicating knock sensor degradation responsive to a lower than threshold knock sensor output following the induced knock event.

5. The method of claim 4, further comprising, responsive to the indicating, reducing an intake air charge to limit an engine load.

6. The method of claim 1, wherein the knock event is further induced via application of spark advance in the cylinder.

7. The method of claim 6, wherein the inducing includes:

during an engine shutdown, spinning the engine to rest at a position where the cylinder is sealed with each of an intake and an exhaust valve closed;

operating the laser ignition device in the sealed cylinder for a duration while the engine is at rest; and

during a subsequent engine restart, resuming fuel delivery to the cylinder with spark timing of the cylinder advanced from MBT.

8. The method of claim 7, wherein the duration of operating the laser ignition device in the cylinder is based on target cylinder temperature and wherein an amount of spark advance applied to the cylinder is based on engine temperature.

9. The method of claim 7, wherein the position where the cylinder is sealed includes top dead center of an exhaust stroke of the cylinder.

10. The method of claim 7, wherein spinning the engine to rest at a position where the cylinder is sealed includes adjusting an engine spin-down speed profile, via an electric motor, to park the cylinder in the sealed position when the engine is at rest.

11. A method, comprising:

operating a laser ignition system in an unfueled cylinder while an engine is at rest, the cylinder parked in a position with each of an intake and an exhaust valve closed;

restarting the engine by resuming fueling to the cylinder with spark timing advanced; and

indicating knock sensor degradation responsive to lower than threshold knock sensor output following the restarting.

12. The method of claim 11, further comprising, reducing an intake aircharge to limit an engine load responsive to the indicating knock sensor degradation.

13. The method of claim 11, further comprising selecting the cylinder based on a location of the cylinder relative to the knock sensor on an engine block, the selected cylinder located closer to the knock sensor relative to remaining engine cylinders.

14. The method of claim 11, wherein the position includes an end of an exhaust stroke of the cylinder, inside of a region of negative intake to exhaust valve overlap.

15. The method of claim 11, further comprising, disabling engine fueling responsive to idle-stop conditions being met, and rotating the engine, unfueled, via an electrically actuated motor, to the position where the exhaust valve and the intake valve of the cylinder is closed, and then disabling engine rotation via the motor.

16. The method of claim 11, wherein operating the laser ignition system includes operating the laser ignition at a high power setting used for initiating cylinder combustion.

17. The method of claim 11, further comprising, adjusting a degree of spark advance applied during the restarting based on cylinder head temperature.

18. A vehicle system, comprising:

an engine including a cylinder, the cylinder having a laser ignition device and a fuel injector;

a knock sensor coupled to an engine block; and

a controller with computer readable instructions stored on non-transitory memory for;

disabling fuel to an engine and spinning the engine to rest with the cylinder parked in a position with an intake and an exhaust valve closed;

operating the laser ignition device coupled to the cylinder to raise cylinder temperature to above a threshold temperature;

resuming fuel delivery to the engine and combusting fuel in the cylinder with an amount of spark timing advance; and

indicating degradation of the knock sensor based on sensor output following the resuming.

19. The system of claim 18, wherein the cylinder is one of a plurality of engine cylinders, and wherein the controller includes further instructions for selecting the cylinder from the plurality of cylinders based on a location of the cylinder relative to the knock sensor on the engine block.

20. The system of claim 18, wherein the position where the cylinder is parked includes a top dead center of an exhaust stroke of the cylinder.