Laser ignition system based diagnostics
Methods and systems are provided for using an engine laser ignition system to perform a visual inspection of an engine and diagnose various cylinder components and conditions based on engine positional measurements. Laser pulses may be emitted at a lower power level during an intake and/or exhaust stroke to illuminate a cylinder interior while a photodetector captures images of the cylinder interior. Additionally, laser pulses may be emitted at a higher power level to initiate cylinder combustion while the photodetector captures images of the cylinder interior using the light generated during cylinder combustion.
1. A method for an engine, comprising:
over an engine cycle,
operating a laser ignition device in each engine cylinder;
identifying a piston position in each cylinder based on the operating; and
differentiating between a twisted crankshaft and a broken crankshaft based on the piston position of each cylinder.
2. The method of claim 1 , wherein identifying a piston position in each cylinder based on the operating includes:
for each cylinder,
sensing light reflected off a top surface of the piston; and
estimating the piston position based on a time elapsed between the operating of the laser ignition device and the sensing of the light.
3. The method of claim 1 , wherein the operating includes operating the laser ignition device at a lower power in one of a compression stroke, a power stroke, and an exhaust stroke of each engine cylinder to identify the piston position, the lower power below a threshold power required to initiate cylinder combustion.
4. The method of claim 1 , further comprising operating the laser ignition device at a higher power in a compression stroke of each cylinder to initiate cylinder combustion, the higher power above a threshold power required to only illuminate the cylinder.
5. The method of claim 1 , wherein the differentiating includes indicating that the crankshaft is twisted based on a difference between the piston position of a first cylinder relative to a second cylinder being higher than a threshold amount, the second cylinder selected based on the first cylinder.
6. The method of claim 1 , wherein the differentiating includes indicating that the crankshaft is broken based on the piston position of at least some cylinders of the engine not changing.
7. A method for an engine, comprising:
over an engine cycle,
operating a laser ignition device in each engine cylinder;
identifying a cylinder valve position in each cylinder based on the operating; and
differentiating between a twisted camshaft and a broken camshaft based on the valve position of each cylinder.
8. The method of claim 7 , wherein the cylinder valve is a cylinder intake valve.
9. The method of claim 8 , wherein identifying a valve position in each cylinder based on the operating includes:
for each cylinder,
sensing light reflected off the cylinder valve; and
estimating a camshaft position based on a time elapsed between the operating of the laser ignition device and the sensing of the light.
10. The method of claim 7 , wherein the operating includes operating the laser ignition device at a lower power in one of an intake stroke or an exhaust stroke of each engine cylinder, the lower power below a threshold power required to initiate cylinder combustion.
11. The method of claim 10 , further comprising operating the laser ignition device at a higher power in a compression stroke of each cylinder to initiate cylinder combustion, the higher power above a threshold power required to only illuminate the cylinder.
12. The method of claim 9 , wherein the indicating includes indicating camshaft degradation based on a difference between the valve position of a first cylinder and a second cylinder being higher than a threshold amount, the second cylinder selected based on the first cylinder.
13. The method of claim 7 , wherein the differentiating includes:
indicating that the camshaft is twisted based on each cylinder having a cam event and a cam event timing of all the cylinders having an unexpected offset; and
indicating the camshaft is broken based on some cylinders having no cam event while remaining cylinders have the cam event.
14. The method of claim 7 , wherein indicating degradation of the camshaft includes indicating that an electric cam system coupled to the camshaft is degraded.
15. A method, comprising:
operating a laser ignition device in an engine cylinder over an engine cycle;
identifying a cylinder piston position and a cylinder valve position based on the operating, the piston position identified during a compression, power, or exhaust stroke of the engine cycle based on a reflected laser signal, the cylinder valve position identified during an intake stroke of the engine cycle based on a blocked laser signal; and
indicating misalignment of a crankshaft relative to a camshaft based on a deviation of the identified cylinder valve position from an expected valve position, the expected valve position based on the identified cylinder piston position.
16. The method of claim 15 , wherein the cylinder valve position includes a cylinder intake valve position.
17. The method of claim 16 , wherein the identifying includes:
identifying the cylinder valve position based on a time taken to detect a laser signal reflected off of a cylinder valve, the cylinder valve substantially blocking the laser signal; and
identifying the cylinder piston position based on a time taken to detect a laser signal reflected off the cylinder piston.
18. The method of claim 15 , wherein operating the laser ignition device includes operating at a power level lower than a threshold power required for initiating cylinder combustion.
19. The method of claim 16 , wherein indicating misalignment includes setting a diagnostic code, and in response to the indication, advancing an intake cam timing to compensate for degraded flow through the cylinder intake valve.