Method and system for controlling engine ignition timing

1. An ignition timing control method for an internal combustion engine, comprising:

determining if conditions for ignition retardation control exist;

calculating a basic ignition timing value based on a knocking learning value, an ignition timing value according to an engine speed and an intake air pressure, and an ignition timing value according to an intake air temperature, if it is determined that the conditions exist;

calculating an ignition timing retardation value;

calculating an ignition retardation coefficient based on a coolant temperature; and

calculating a final ignition timing value based on the basic ignition timing value, the ignition timing retardation value, and the ignition retardation coefficient.

2. The method of claim 1 , wherein said determining comprises:

detecting one or more vehicle operating conditions;

comparing the detected vehicle operating conditions to predetermined values; and

determining if the conditions for the ignition retardation control exist based on said comparing.

3. The method of claim 2 , wherein the vehicle operating conditions comprise at least one of a period of time after engine starting, an engine speed, an engine load state, a shift range, and a coolant temperature.

4. The method of claim 1 , wherein it is determined that the conditions for ignition retardation control exist if the period of time after engine starting is larger than a predetermined value, the engine speed is higher than a predetermined speed, the engine load state is a predetermined state, the shift range is a predetermined shift range, and the coolant temperature is within a predetermined range.

5. The method of claim 4 , wherein the predetermined engine load state is an idle state or a partial load state, and the predetermined shift range is a neutral range.

6. The method of claim 5 , wherein the shift range is detected by an inhibitor switch.

7. The method of claim 1 , wherein the ignition timing value according to the engine speed and the intake air pressure is determined by a predetermined ignition timing map.

8. The method of claim 1 , wherein the basic ignition timing value is calculated according to the following equation:

θ base =K — knl *θ( N e , P b )+θ( AT )

where θ base is the basic ignition timing value, K_kn 1 is a knocking learning value, θ(N e , P b ) is an ignition timing value according to an engine speed and an intake air pressure, and θ(AT) is an ignition timing value according to an intake air temperature.

9. The method of claim 1 , wherein the ignition timing retardation value is calculated based on an engine speed and an intake air pressure.

10. The method of claim 1 , wherein the ignition retardation coefficient is determined to be inversely proportional to an engine coolant temperature.

11. The method of claim 1 , wherein the final ignition timing value is determined by the following equation:

θ=min[( K WT *θ rtd +(1- K WT )*θ base ), θ base ]

where θ is the final ignition timing value, K WT is the ignition retardation coefficient, θ rtd is the ignition timing retardation value, θ base is the basic ignition timing value, and “min” is a function to select a smaller value.

12. An ignition timing control method for an internal combustion engine, comprising:

determining if predetermined conditions for ignition retardation control exist;

calculating a basic ignition timing value based on a knocking learning value, an engine speed, an intake air pressure, and an intake air temperature, if it is determined that the predetermined conditions exist;

calculating an ignition timing retardation value based on an engine speed and an intake air pressure;

calculating an ignition retardation coefficient based on an engine coolant temperature;

calculating a final ignition timing value based on the basic ignition timing value, the ignition timing retardation value, and the ignition retardation coefficient; and

controlling ignition timing according to the final ignition timing value.

13. The method of claim 12 , wherein it is determined that the predetermined condition for ignition timing retardation control exists if the period of time after engine starting is larger than a predetermined value, the engine speed is higher than a predetermined speed, the mode of engine load is a predetermined mode, the shift range is a predetermined shift range, and the coolant temperature is within a predetermined range.

14. The method of claim 12 , wherein the final ignition timing value is calculated according to the following equation:

θ=min[( K WT *θ rtd +(1- K WT )*θ base ), θ base ]

where θ is the final ignition timing value, K WT is the ignition retardation coefficient, θ rtd is the ignition timing retardation value, θ base is the basic ignition timing value, and “min” is a function to select a smaller value.

15. An ignition timing control system for an internal combustion engine, comprising:

an ignition device; and

a control unit configured for: receiving inputs of one or more vehicle operating conditions, determining an ignition timing value based on the vehicle operating conditions, and outputting a signal representative of the determined ignition timing value to the ignition device, where the control unit is programmed to execute steps comprising:

determining if a predetermined condition for ignition timing retardation control exists;

calculating a basic ignition timing value based on a knocking learning value, an engine speed, an intake air pressure, and an intake air temperature, if it is determined that the predetermined condition exist;

calculating an ignition timing retardation value based on an engine speed and an intake air pressure;

calculating an ignition retardation coefficient based on an engine coolant temperature;

calculating a final ignition timing value based on the basic ignition timing value, the ignition timing retardation value, and the ignition retardation coefficient; and

controlling ignition timing according to the final ignition timing value.

16. The system of claim 15 , wherein it is determined that the predetermined condition for the ignition retardation control exists if the engine coolant temperature is within a predetermined range.

17. The system of claim 15 , wherein the final ignition timing value is determined according to the following equation:

θ=min[( K WT *θ rtd +(1- K WT )*θ base ), θ base ]

where θ is the final ignition timing value, K WT is the ignition retardation coefficient, θ rtd is the ignition timing retardation value, θ base is the basic ignition timing value, and “min” is a function to select a smaller value.