Methods and systems for engine fuel and torque control

Patent metadata

Field	Value
Publication number	US-9845760-B2
Application number	US-201615076212-A
Country	US
Kind code	B2
Filing date	Mar 21, 2016
Priority date	Mar 21, 2016
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

Methods and systems are provided for accurately estimating intake aircharge based on the output of an intake oxygen sensor while flowing EGR, purge, or PCV hydrocarbons to the engine. The unadjusted aircharge estimate is used for engine fuel control while the hydrocarbon adjusted aircharge estimate is used for engine torque control. A controller is configured to sample the oxygen sensor at even increments in a time domain, stamp the sampled data in a crank angle domain, store the sampled data in a buffer, and then select one or more data samples corresponding to a last firing period from the buffer for estimating the intake aircharge.

First claim

The invention claimed is:

1. A method for an engine, comprising:
sampling an intake oxygen sensor signal at even increments of time;
storing each sampled signal in a buffer;
processing the stored sampled signals in the buffer at even increments of engine crank angle; and
adjusting an engine operating parameter based on a selected two or more of the processed sampled signals.

2. The method of claim 1 , wherein adjusting an engine operating parameter based on a selected two or more of the processed sampled signals comprises adjusting a fuel injection amount based on an average of the selected two or more of the processed sampled signals.

3. The method of claim 1 , wherein processing the stored sampled signals in the buffer at even increments of engine crank angle comprises processing the stored sampled signals at an engine firing frequency.

4. The method of claim 1 , further comprising, prior to storing each sampled signal in the buffer, stamping each sampled signal with an engine crank angle stamp that corresponds to an engine crank angle at a time the sampled signal was sampled.

5. The method of claim 4 , wherein the processing is performed once every engine firing event, and wherein processing the stored sampled signals in the buffer at even increments of engine crank angle comprises:
at a firing event for a given cylinder, selecting at least two sampled signals from the buffer having an engine crank angle stamp that corresponds to an engine crank angle for an immediately previous firing event (of the given cylinder);
processing the selected sampled signals to estimate intake manifold aircharge; and wherein adjusting the fuel injection amount comprises adjusting the fuel injection amount based on the estimated intake manifold aircharge.

6. The method of claim 5 , wherein estimating the intake manifold aircharge includes estimating a net oxygen flow rate into engine cylinders.

7. The method of claim 5 , wherein the intake oxygen sensor is coupled to an engine intake passage, and wherein the sampling, storing, and processing is performed while recirculating exhaust gas from an exhaust passage to the intake passage.

8. The method of claim 7 , further comprising correcting the fuel injection amount responsive to a fuel injector error learned based on an exhaust air-fuel ratio sensor, fuel injector error learned while recirculating the exhaust gas; and adjusting a fuel injector pulse-width to inject fuel at the corrected fuel injection amount to a given cylinder.

9. The method of claim 8 , further comprising correcting the estimated intake manifold aircharge based on a hydrocarbon concentration of the recirculating exhaust gas, and adjusting an engine torque actuator based on the corrected intake manifold aircharge.

10. The method of claim 9 , wherein the hydrocarbon concentration of the recirculating exhaust gas is estimated by an air-fuel ratio sensor coupled to an EGR passage, and wherein the engine torque actuator includes an EGR valve coupled to the EGR passage.

11. A method for an engine, comprising:
sampling an intake manifold oxygen sensor signal at predetermined time intervals to generate a data set including a plurality of samples;
stamping each sample of the data set with an engine crank angle; and
in response to a fuel injection request, adjusting fuel injection based on an intake aircharge amount estimated based on a selected two or more samples of the data set, the selected two or more samples having an engine crank angle stamp corresponding to one firing period immediately preceding the fuel injection request.

12. The method of claim 11 , wherein the fuel injection request comprises a fuel injection request for a given cylinder of the engine, and wherein at least one of the selected two or more samples has a crank angle stamp that is closest to a designated engine crank angle relative to all other samples in the data set, the designated engine crank angle corresponding to an intake valve closing event for the given cylinder.

13. The method of claim 11 , wherein stamping each sample of the data set with an engine crank angle comprises, for a given sample, retrieving a crank angle of the engine at a point in time when the given sample was sampled and stamping the given sample with the retrieved crank angle.

14. The method of claim 11 , further comprising storing the data set in a buffer of a memory of a controller operably coupled to the intake oxygen sensor.

15. The method of claim 14 , further comprising, after adjusting the fuel injection based on the intake aircharge amount estimated based on the selected two or more samples, discarding remaining samples of the data set from the buffer.

16. A system, comprising:
an engine having a cylinder supplied with intake air from an intake passage;
an oxygen sensor coupled to the intake passage;
a fuel system including a fuel tank coupled to a canister for storing fuel vapors, a purge passage for purging canister fuel vapors to the intake passage, and a purge valve coupled to the purge passage;
an exhaust gas sensor coupled to an exhaust passage;
a direct fuel injector for injecting fuel into the cylinder; and
a controller with computer readable instructions stored on non-transitory memory for:
while purging fuel vapors from the canister to the intake passage,
sampling a signal from the oxygen sensor at a predetermined sampling rate;
for each sample, stamping the sample with a corresponding engine crank angle;
storing each stamped sample in a buffer; and
responsive to a request to inject fuel into the cylinder,
retrieving at least two samples from the buffer having a crank angle stamp corresponding to a firing period immediately preceding the request;
calculating an aircharge estimate for the cylinder based on an average of the retrieved at least two samples;
determining a fuel injection amount based on the calculated aircharge estimate;
correcting the fuel injection amount based on a learned fuel injector error; and
commanding a pulse width to the fuel injector based on the corrected fuel injection amount.

17. The system of claim 16 , wherein the direct fuel injector is configured to inject a first, liquid fuel into the cylinder, the system further comprising a port fuel injector for injecting a second, gaseous fuel into an intake port of the cylinder.

18. The system of claim 16 , wherein the fuel injection amount based on the calculated aircharge estimate is independent of a purge fuel vapor concentration, and wherein the controller includes further instructions for:
correcting the aircharge estimate responsive to the purge fuel vapor concentration, the purge fuel concentration based on a purge sensor coupled to the purge passage; and
adjusting one or more engine torque actuators based on the corrected aircharge estimate, the one or more engine torque actuators including the purge valve.

19. The system of claim 16 , wherein the controller includes further instructions for adaptively learning the fuel injector error based on an output of the exhaust gas sensor while purging the canister fuel vapors to the intake passage.

20. The system of claim 16 , wherein sampling the signal from the oxygen sensor includes applying a reference voltage where water molecules do not dissociate to the oxygen sensor and sampling a pumping current output upon application of the reference voltage.

Assignees

• Ford Global Tech Llc

Inventors

• Pursifull Ross Dykstra
• Trzeciak Justin
• Ulrey Joseph Norman
• Surnilla Gopichandra

Classifications

• F02D41/263 Primary

  the program execution being modifiable by physical parameters · CPC title

• F02D35/028

  by determining the combustion timing or phasing · CPC title

• F02M35/10373

  Sensors for intake systems (throttle position sensors F02D9/105) · CPC title

• F02D41/0077

  Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position (EGR valve position sensor F02M26/48) · CPC title

• F02D41/144 Primary

  Sensor in intake manifold · CPC title