COMBUSTION PHASING CONTROL IN SPARK-ASSISTED HCCI COMBUSTION MODE

• US 20120118267A1
• Filed: 11/16/2010
• Published: 05/17/2012
• Est. Priority Date: 11/16/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Kang, Jun-Mo, Yun, Hanho, Chang, Chen-Fang
• Granted Patent: US 8,469,002 B2
• Time in Patent Office: Days
• US Class Current: 123/406.26
• CPC Class Codes: F02B 1/12 with compression ignition with fuel-air charge ignited by compression ignition of an additional fuel F02B7/00
• CPC Class Codes: F02B 2075/125 Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
• CPC Class Codes: F02D 13/0207 changing valve lift or valve lift and timing
• CPC Class Codes: F02D 13/0219 by shifting the phase, i.e. the opening periods of the valves are constant
• CPC Class Codes: F02D 13/0265 Negative valve overlap for temporarily storing residual gas in the cylinder
• CPC Class Codes: F02D 35/028 by determining the combustion timing or phasing
• CPC Class Codes: F02D 41/0052 Feedback control of engine parameters, e.g. for control of air/fuel ratio or intake air amount
• CPC Class Codes: F02D 41/0057 Specific combustion modes combustion modes per se F02D41/3017
• CPC Class Codes: F02D 41/0085 Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio
• CPC Class Codes: F02D 41/3041 with means for triggering compression ignition, e.g. spark plug
• CPC Class Codes: F02M 26/21 with EGR valves located at or near the connection to the intake system
• CPC Class Codes: F02P 5/1512 with particular means concerning an individual cylinder
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for controlling combustion in a multi-cylinder spark-ignition direct-injection internal combustion engine includes determining a desired combustion phasing for maintaining acceptable combustion properties, monitoring combustion phasing of each cylinder, selecting a target combustion phasing corresponding to one of the cylinders having a most retarded combustion phasing, adjusting spark timing in each cylinder not having the most retarded combustion phasing to achieve the target combustion phasing to balance the combustion phasing in all the cylinders at the target combustion phasing, and adjusting an external EGR percentage to converge the balanced combustion phasing in all the cylinders toward the desired combustion phasing.

Claims

1. Method for controlling combustion in a multi-cylinder spark-ignition direct-injection internal combustion engine, comprising:

determining a desired combustion phasing for maintaining acceptable combustion properties;

monitoring combustion phasing of each cylinder;

selecting a target combustion phasing corresponding to one of the cylinders having a most retarded combustion phasing;

adjusting spark timing in each cylinder not having the most retarded combustion phasing to achieve the target combustion phasing to balance the combustion phasing in all the cylinders at the target combustion phasing; and

adjusting an external EGR percentage to converge the balanced combustion phasing in all the cylinders toward the desired combustion phasing.

2. The method of claim 1 wherein the combustion properties comprise combustion noise, combustion efficiency and combustion stability.

3. The method of claim 1 wherein adjusting spark timing in each cylinder not having the most retarded combustion phasing comprises:

comparing the monitored combustion phasing of each cylinder to the target combustion phasing; and

determining a respective combustion phasing difference for each respective cylinder based on the comparison; and

adjusting spark timing in each cylinder not having the most retarded combustion phasing by an amount based on the respective combustion phasing difference.

4. The method of claim 3 wherein the adjusting spark timing in each cylinder not having the most retarded combustion phasing comprises generating a respective integrator value for each cylinder based on the respective combustion phasing difference, the respective integrator value directly corresponding to the amount the spark timing in the corresponding cylinder not having the most retarded combustion phasing must be adjusted to achieve the target combustion phasing.

5. The method of claim 4 wherein the respective integrator value is utilized in a feedback control loop for adjusting spark timing in each cylinder not having the most retarded combustion phasing in an immediately subsequent engine cycle.

6. The method of claim 3 wherein adjusting spark timing in each cylinder not having the most retarded combustion phasing comprises retarding the spark timing in each cylinder not having the most retarded combustion phasing by an amount based on the respective combustion phasing difference for each respective cylinder.

7. The method of claim 1 further comprising monitoring an operator torque request;

and

wherein adjusting the external EGR percentage comprises adjusting the external EGR percentage to a value corresponding to the operator torque request.

8. The method of claim 7 wherein adjusting the external EGR percentage to a value corresponding to the operator torque request comprises adjusting the external EGR percentage to maintain a stoichiometric air fuel ratio.

9. The method of claim 7 further comprising:

Increasing an injected fuel mass in response to an increased operator torque request; and

wherein adjusting the external EGR percentage comprises decreasing the external EGR percentage to achieve the value corresponding to the monitored operator torque request.

10. The method of claim 1 wherein selecting the target combustion phasing comprises determining achievability of the cylinders not having the most retarded combustion phasing to converge combustion phasing to the target combustion phasing through individual spark timing adjustment.

11. Method for controlling combustion in a multi-cylinder spark-ignition direct-injection internal combustion engine, comprising:

monitoring an operator torque request;

determining a desired combustion phasing for maintaining acceptable combustion noise and combustion efficiency based on the monitored operator torque request;

monitoring combustion phasing of each cylinder;

selecting a target combustion phasing corresponding to one of the cylinders having a most retarded combustion phasing;

balancing the combustion phasing in all of the cylinders comprising;

comparing the monitored combustion phasing in each cylinder to the target combustion phasing;

determining a combustion phasing difference for each respective cylinder based on the comparing;

retarding a spark timing in each cylinder by an amount based on the respective combustion phasing difference; and

adjusting an external EGR percentage to converge the balanced combustion phasing in all of the cylinders toward the desired combustion phasing.

12. The method of claim 11 further comprising:

operating the engine in a high-load homogeneous charge compression ignition mode including spark-assisted ignition, including, for each cylinder;

delivering an injected fuel mass using a single injection during an intake stroke based on the operator torque request;

spark-igniting the injected fuel mass subsequent to the single injection during a compression stroke effective to initiate flame propagation sufficient to increase temperature of the injected fuel mass to effect auto-ignition.

13. The method of claim 12 wherein spark igniting the injected fuel mass retards auto-ignition to extend the high-load operating limit of controlled auto-ignition combustion.

14. The method of claim 11 further comprising:

utilizing an exhaust recompression strategy including a negative valve overlap period to provide residual heat adequate for controlled auto-ignition.

15. The method of claim 14 wherein monitoring an operator torque request comprises:

operating the engine in a high-load homogenous charge compression ignition mode including spark-assisted ignition based on the operator torque request;

decreasing the negative valve overlap to increase cylinder volume availability for mass air flow to enter each cylinder; and

decreasing the external EGR percentage to maintain an air-fuel ratio based on the operator torque request.