Method to optimize engine operation using active fuel management

• US 9,903,283 B1
• Filed: 08/24/2016
• Issued: 02/27/2018
• Est. Priority Date: 08/24/2016
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Rayl, Jr., Allen B., Dibble, Donovan L., Burleigh, Darrell W., Haase, Steven J.
• Primary Examiner(s): Low, Lindsay
• Assistant Examiner(s): Jin, George
• Application Number:
  US15/245,652
• Publication Number:
  US 20180058345A1
• Time in Patent Office: 552 Days
• CPC Class Codes: F02D 17/02 Cutting-out cutting-out engines in multiple engine arrangements F02D25/04
• CPC Class Codes: F02D 2200/1004 Estimation of the output torque
• CPC Class Codes: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 2250/41 Control to generate negative pressure in the intake manifold, e.g. for fuel vapor purging or brake booster
• CPC Class Codes: F02D 2700/02 Controlling by changing the air or fuel supply
• CPC Class Codes: F02D 2700/05 Controlling by preventing combustion in one or more cylinders
• CPC Class Codes: F02D 37/02 one of the functions being ignition
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/1406 with use of a optimisation method, e.g. iteration
• CPC Class Codes: F02D 41/26 using computer, e.g. microprocessor
• CPC Class Codes: F02P 5/1504 with particular means during a transient phase, e.g. acceleration, deceleration, gear change during starting F02P5/1506

Abstract

A method for operating an internal combustion engine includes providing a vehicle having an internal combustion gasoline engine including multiple cylinders and wherein the engine is capable of running on at least one of a plurality firing fractions, providing a vacuum offset (Offset_vac) to adjust airflow capacity for each of the plurality of firing fractions, determining a torque capacity of each of the plurality firing fractions and a plurality of available firing fractions that provides at least enough torque capacity to accommodate a current torque requested (T_req), determining a plurality of viable firing fractions of the plurality of available firing fractions, and determining and implementing an optimal firing fraction of the viable firing fractions if the optimal firing fraction provides enough fuel economy benefit over a current firing fraction.

Claims

1. A method for operating an internal combustion engine, the method comprising:

providing a vehicle having an internal combustion gasoline engine including multiple cylinders and wherein the engine is capable of running on at least one of a plurality of firing fractions;

providing a vacuum offset (Offset_vac) to adjust airflow capacity for each of the plurality of firing fractions;

determining a torque capacity of each of the plurality of firing fractions and a plurality of available firing fractions that provides at least enough torque capacity to accommodate a current torque requested (T_req), and wherein determining the torque capacity of each of the plurality of firing fractions comprises;

determining a net torque capacity (T_net) of the engine;

determining a maximum brake torque (T_FF) for each firing fraction; and

determining a minimum firing fraction that produces at least enough brake torque T_FF to accommodate the current torque request T_req;

determining a plurality of viable firing fractions of the plurality of available firing fractions; and

determining and implementing an optimal firing fraction of the viable firing fractions if the optimal firing fraction provides enough fuel economy benefit over a current firing fraction.

2. The method of operating an internal combustion engine of claim 1 wherein providing the vacuum offset (Offset_vac)) to adjust airflow capacity for each of the firing fractions further comprises:

increasing Offset_vac if an intake manifold vacuum (Vac) is less than a first predetermined threshold for a period of time (T);

decreasing Offset_vac if an intake manifold vacuum (Vac) is greater than a first predetermined threshold for a period of time (T) and an engine load is high; and

maintaining a current Offset_vac.

3. The method of operating an internal combustion engine of claim 1 wherein determining the net torque capacity (T_net) of the engine further comprises determining the T_net as a function of engine speed (RPM), maximum torque cam position, barometric pressure, Vac, Offset_vac, temperature, and humidity.

4. The method of operating an internal combustion engine of claim 1 wherein determining the maximum brake torque (T_FF) for each firing fraction further comprises determining T_FF by the equation:

T_FF=T_net*FF+T_friction

wherein T_friction is a constant torque loss due to friction losses of the engine.

5. The method of operating an internal combustion engine of claim 1 wherein determining a plurality of viable firing fractions of the plurality of available firing fractions further comprises:

determining a new engine speed EngSpd_new and a transit engine speed EngSpd_transit for one of the plurality of available firing fractions;

determining a minimum engine speed EngSpd_min of the one of the plurality of available firing fractions;

determining a maximum engine speed EngSpd_max of the one of the plurality of available firing fractions, and wherein EngSpd_max is the highest of a current engine speed EngSpd_current, EngSpd_new, and EngSpd_transit;

determining a net torque T_netES_min and T_netES_max for each of EngSpd_min and EngSpd_max;

determining a torque limit T_limit as the minimum of TnetES_min and TnetES_max;

assigning the one of the plurality of available firing fractions as a viable firing fraction if a brake torque limit of a firing fraction T_brklim is greater than the requested brake torque T_brkreq in addition to a hysteresis and if T_limit is greater than a requested net torque T_netreq in addition to the hysteresis; and

assigning the one of the plurality of available firing fractions as a nonviable firing fraction if the brake torque limit of the firing fraction T_brklim is not greater than the requested brake torque T_brkreq in addition to the hysteresis or if T_limit is not greater than a requested net torque T_netreq in addition to the hysteresis.

6. The method of operating an internal combustion engine of claim 1 wherein determining and implementing an optimal firing fraction of the viable firing fractions if the optimal firing fraction provides enough fuel economy benefit over a current firing fraction further comprises:

determining a most fuel efficient of the plurality of viable firing fractions FF_best;

determining a fuel efficiency of the current firing fraction FF_current;

determines a ratio of a fuel efficiency Effratio of the most fuel efficient firing fraction FF_best to the efficiency of the current firing fraction FF_current;

maintaining the FF_current if the Effratio is greater than a first threshold ratio TH1;

switching to the FF_best if the Effratio is less than a second threshold ratio TH2;

maintaining the FF_current and determining the most fuel efficient of the plurality of viable firing fractions FF_best if the Effratio is less than a first threshold ratio TH1 and greater than a second threshold ratio TH2.

7. The method of operating an internal combustion engine of claim 6 wherein maintaining the FF_current if the Effratio is greater than a first threshold ratio TH1 further comprises maintaining the FF_current if the Effratio is greater than 98.5% and switching to the FF_best if the Effratio is less than a second threshold ratio TH2 further comprises switching to the FF_best if the Effratio is less than 95%.

8. A method for operating an internal combustion engine, the method comprising:

providing a vehicle having an internal combustion gasoline engine including multiple cylinders and wherein the engine is capable of running on at least one of a plurality firing fractions;

providing a vacuum offset (Offset_vac) to adjust airflow capacity for each of the plurality of firing fractions providing a vacuum offset (Offset_vac) to adjust airflow capacity for each of the firing fractions by;

increasing Offset_vac if an intake manifold vacuum (Vac) is less than a first predetermined threshold for a period of time (T);

decreasing Offset_vac if an intake manifold vacuum (Vac) is greater than a first predetermined threshold for a period of time (T) and an engine load is high; and

maintaining a current Offset_vac.;

determining a torque capacity of each of the plurality firing fractions and a plurality of available firing fractions that provides at least enough torque capacity to accommodate a current torque requested (T_req) by;

determining the net torque capacity (T_net) of the engine;

determining the maximum brake torque (T_FF) for each firing fraction; and

determining a minimum firing fraction that produces at least enough brake torque T_FF to accommodate a current torque request T_req;

determining a plurality of viable firing fractions of the plurality of available firing fractions; and

determining and implementing an optimal firing fraction of the viable firing fractions if the optimal firing fraction provides enough fuel economy benefit over a current firing fraction.

9. The method of operating an internal combustion engine of claim 8 wherein determining the net torque capacity (T_net) of the engine further comprises determining the T_net as a function of engine speed (RPM), maximum torque cam position, barometric pressure, Vac, Offset_vac, temperature, and humidity.

10. The method of operating an internal combustion engine of claim 8 wherein determining the maximum brake torque (T_FF) for each firing fraction further comprises determining T_FF by the equation:

T_FF=T_net*FF+T_friction

wherein T_friction is a constant torque loss due to friction losses of the engine.

11. The method of operating an internal combustion engine of claim 8 wherein determining a plurality of viable firing fractions of the plurality of available firing fractions further comprises:

determining a new engine speed EngSpd_new and a transit engine speed EngSpd_transit for one of the plurality of available firing fractions;

determining a minimum engine speed EngSpd_min of the one of the plurality of available firing fractions;

determining finds the maximum engine speed EngSpd_max of the one of the plurality of available firing fractions, and wherein EngSpd_max is the highest of a current engine speed EngSpd_current, EngSpd_new, and EngSpd_transit;

determining a net torque T_netES_min and T_netES_max for each of EngSpd_min and EngSpd_max;

determining a torque limit T_limit as the minimum of T_netES_min and T_netES_max;

assigning the one of the plurality of available firing fractions as a viable firing fraction if the brake torque limit of the firing fraction T_brklim is greater than the requested brake torque T_brkreq in addition to the hysteresis and if T_limit is greater than a requested net torque T_netreq in addition to a hysteresis; and

assigning the one of the plurality of available firing fractions as a nonviable firing fraction if the brake torque limit of the firing fraction T_brklim is not greater than the requested brake torque T_brkreq in addition to the hysteresis or if T_limit is not greater than a requested net torque T_netreq in addition to the hysteresis.

12. The method of operating an internal combustion engine of claim 8 wherein determining and implementing an optimal firing fraction of the viable firing fractions if the optimal firing fraction provides enough fuel economy benefit over a current firing fraction further comprises:

determining the most fuel efficient of the plurality of viable firing fractions FF_best;

determining the fuel efficiency of the current firing fraction FF_current;

determines a ratio of the fuel efficiency Effratio of the most fuel efficient firing fraction FF_best to the efficiency of the current firing fraction FF_current;

maintaining the FF_current if the Effratio is greater than a first threshold ratio TH1;

switching to the FF_best if the Effratio is less than a second threshold ratio TH2;

maintaining the FF_current and determining the most fuel efficient of the plurality of viable firing fractions FF_best if the Effratio is less than a first threshold ratio TH1 and greater than a second threshold ratio TH2.

13. The method of operating an internal combustion engine of claim 8 wherein maintaining the FF_current if the Effratio is greater than a first threshold ratio TH1 further comprises maintaining the FF_current if the Effratio is greater than 98.5% and switching to the FF_best if the Effratio is less than a second threshold ratio TH2 further comprises switching to the FF_best if the Effratio is less than 95%.

14. A method for operating an internal combustion engine, the method comprising:

providing a vehicle having an internal combustion gasoline engine including multiple cylinders and wherein the engine is capable of running on at least one of a plurality firing fractions;

providing a vacuum offset (Offset_vac) to adjust airflow capacity for each of the plurality of firing fractions providing a vacuum offset (Offset_vac) to adjust airflow capacity for each of the firing fractions by;

increasing Offset_vac if an intake manifold vacuum (Vac) is less than a first predetermined threshold for a period of time (T);

decreasing Offset_vac if an intake manifold vacuum (Vac) is greater than a first predetermined threshold for a period of time (T) and an engine load is high; and

maintaining a current Offset_vac.;

determining a torque capacity of each of the plurality firing fractions and a plurality of available firing fractions that provides at least enough torque capacity to accommodate a current torque requested (T_req) by;

determining the net torque capacity (T_net) of the engine;

determining the maximum brake torque (T_FF) for each firing fraction by the equation;

T_FF=T_net*FF+T_friction

wherein T_friction is a constant torque loss due to friction losses of the engine; and

determining a minimum firing fraction that produces at least enough brake torque T_FF to accommodate a current torque request T_req;

determining a plurality of viable firing fractions of the plurality of available firing fractions; and

determining and implementing an optimal firing fraction of the viable firing fractions if the optimal firing fraction provides enough fuel economy benefit over a current firing fraction.

15. The method of operating an internal combustion engine of claim 14 wherein determining the net torque capacity (T_net) of the engine further comprises determining the T_net as a function of engine speed (RPM), maximum torque cam position, barometric pressure, Vac, Offset_vac, temperature, and humidity.

16. The method of operating an internal combustion engine of claim 14 wherein determining a plurality of viable firing fractions of the plurality of available firing fractions further comprises:

determining a new engine speed EngSpd_new and a transit engine speed EngSpd_transit for one of the plurality of available firing fractions;

determining a minimum engine speed EngSpd_min of the one of the plurality of available firing fractions;

determining finds the maximum engine speed EngSpd_max of the one of the plurality of available firing fractions, and wherein EngSpd_max is the highest of a current engine speed EngSpd_current, EngSpd_new, and EngSpd_transit;

determining a net torque T_netES_min and T_netES_max for each of EngSpd_min and EngSpd_max;

determining a torque limit T_limit as the minimum of T_netES_min and T_netES_max;

assigning the one of the plurality of available firing fractions as a viable firing fraction if the brake torque limit of the firing fraction T_brklim is greater than the requested brake torque T_brkreq in addition to the hysteresis and if T_limit is greater than a requested net torque T_netreq in addition to a hysteresis; and

assigning the one of the plurality of available firing fractions as a nonviable firing fraction if the brake torque limit of the firing fraction T_brklim is not greater than the requested brake torque T_brkreq in addition to the hysteresis or if T_limit is not greater than a requested net torque T_netreq in addition to the hysteresis.

17. The method of operating an internal combustion engine of claim 14 wherein determining and implementing an optimal firing fraction of the viable firing fractions if the optimal firing fraction provides enough fuel economy benefit over a current firing fraction further comprises:

determining the most fuel efficient of the plurality of viable firing fractions FF_best;

determining the fuel efficiency of the current firing fraction FF_current;

determines a ratio of the fuel efficiency Effratio of the most fuel efficient firing fraction FF_best to the efficiency of the current firing fraction FF_current;

maintaining the FF_current if the Effratio is greater than a first threshold ratio TH1;

switching to the FF_best if the Effratio is less than a second threshold ratio TH2;

maintaining the FF_current and determining the most fuel efficient of the plurality of viable firing fractions FF_best if the Effratio is less than a first threshold ratio TH1 and greater than a second threshold ratio TH2.

18. The method of operating an internal combustion engine of claim 17 wherein maintaining the FF_current if the Effratio is greater than a first threshold ratio TH1 further comprises maintaining the FF_current if the Effratio is greater than 98.5% and switching to the FF_best if the Effratio is less than a second threshold ratio TH2 further comprises switching to the FF_best if the Effratio is less than 95%.