CONTROL STRATEGY FOR MULTI-STROKE ENGINE SYSTEM

• US 20090277434A1
• Filed: 05/08/2008
• Published: 11/12/2009
• Est. Priority Date: 05/08/2008
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Surnilla, Gopichandra
• Granted Patent: US 8,132,546 B2
• Time in Patent Office: Days
• US Class Current: 123/65.R
• CPC Class Codes: F01L 13/0036 the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
• CPC Class Codes: F01L 2009/2169 Position sensors
• CPC Class Codes: F01L 9/20 by electric means
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: F02B 2075/027 four
• 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: F02B 23/104 the injector being placed on a side position of the cylinder
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02D 13/0215 changing the valve timing only
• CPC Class Codes: F02D 13/0253 Fully variable control of valve lift and timing using camless actuation systems such as hydraulic, pneumatic or electromagnetic actuators, e.g. solenoid valves
• CPC Class Codes: F02D 13/0261 Controlling the valve overlap
• CPC Class Codes: F02D 13/028 for two-stroke engines
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 2400/02 Four-stroke combustion engines with electronic control
• CPC Class Codes: F02D 2400/04 Two-stroke combustion engines with electronic control
• CPC Class Codes: F02D 37/02 one of the functions being ignition
• CPC Class Codes: F02D 41/3058 the engine working with a variable number of cycles
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

An engine system and a method of operation are described. As one example, the method may include: during a first operating condition, operating a cylinder of the engine in a two stroke cycle to combust a first mixture of air and fuel, and adjusting an opening overlap between an intake poppet valve and an exhaust poppet valve of the cylinder to vary a composition of exhaust gases exhausted by the cylinder via the exhaust poppet valve; and during a second operating condition, operating a cylinder of the engine in a four stroke cycle to combust a second mixture of air and fuel, and adjusting a relative amount of fuel contained in the second mixture of air and fuel to vary the composition of exhaust gases exhausted by the cylinder via the exhaust poppet valve.

Claims

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

during a first operating condition, operating a cylinder of the engine in a two stroke cycle to combust a first mixture of air and fuel, and adjusting an opening overlap between an intake poppet valve and an exhaust poppet valve of the cylinder to vary a composition of exhaust gases exhausted by the cylinder via the exhaust poppet valve; and

during a second operating condition, operating the cylinder of the engine in a four stroke cycle to combust a second mixture of air and fuel, and adjusting a relative amount of fuel contained in the second mixture of air and fuel to vary the composition of exhaust gases exhausted by the cylinder via the exhaust poppet valve.

2. The method of claim 1, further comprising, during the first operating condition, adjusting a level of boosted intake air provided to the cylinder via the intake poppet valve to further vary the composition of the exhaust gases exhausted by the cylinder via the exhaust poppet valve.

3. The method of claim 1, wherein said composition of exhaust gases includes an elemental oxygen content of the exhaust gases;

where the method further comprises varying the composition of the exhaust gases in response to feedback received from an exhaust gas sensor; and

where said adjusting an opening overlap between an intake poppet valve and an exhaust poppet valve includes increasing the opening overlap to increase the elemental oxygen content of the exhaust gases and reducing the opening overlap to reduce the elemental oxygen content of the exhaust gases.

4. The method of claim 1, wherein the first mixture of air and fuel is richer than the second mixture of air and fuel for a given composition of the exhaust gases exhausted by the cylinder via the exhaust poppet valve.

5. A method of operating an internal combustion engine, comprising:

operating the engine in a two stroke cycle by;

initiating combustion of an air and fuel mixture in a cylinder of an internal combustion engine;

receiving intake air at the cylinder via an intake poppet valve of the cylinder after initiating said combustion of the air and fuel mixture;

exhausting an exhaust gas mixture from the cylinder via an exhaust poppet valve, said exhaust gas mixture including at least some of the received intake air and the combusted rich mixture; and

adjusting a timing of at least one of the intake poppet valve and the exhaust poppet valve of the cylinder to vary a composition of the exhaust gas mixture.

6. The method of claim 5, wherein said composition of the exhaust gas mixture includes a concentration of elemental oxygen in the exhaust gas mixture, where said timing is adjusted in response to feedback from an exhaust gas oxygen sensor so that the composition approaches a desired composition.

7. The method of claim 6, wherein said adjusting the timing of at least one of the intake poppet valve and exhaust poppet valve of the cylinder includes increasing an opening overlap between the intake poppet valve and the exhaust poppet valve to increase the oxygen content of the exhaust gas mixture.

8. The method of claim 6, wherein said adjusting the timing of at least one of the intake poppet valve and exhaust poppet valve of the cylinder includes reducing an opening overlap between the intake poppet valve and the exhaust poppet valve to reduce the oxygen content of the exhaust gas mixture.

9. The method of claim 5, further comprising:

boosting intake air by operating a boosting device fluidly coupled with the cylinder via the intake poppet valve; and

adjusting a level of said boosting to further vary the composition of the exhaust gas mixture.

10. The method of claim 5, further comprising:

varying a relative amount of the fuel contained in the air and fuel mixture by adjusting a fuel injector pulse-width in response to an opening overlap between the intake poppet valve and exhaust poppet valve to further vary the composition of the exhaust gas mixture, and further adjusting the relative amount of the fuel in response to feedback from an exhaust gas oxygen sensor.

11. The method of claim 5, further comprising:

during a first operating condition, operating the engine in the two stroke cycle; and

during a second operating condition, operating the engine in a four stroke cycle.

12. An engine system for a vehicle propulsion system, comprising:

an internal combustion engine including at least one cylinder having a piston;

an intake passage in fluid communication with the cylinder via at least one intake poppet valve;

an intake valve actuator coupled to the intake poppet valve;

an exhaust passage in fluid communication with the cylinder via at least one exhaust poppet valve;

an exhaust valve actuator coupled to the exhaust poppet valve;

a control system configured to;

operate the cylinder in a two stroke cycle during a first operating condition by combusting an air and fuel mixture in the cylinder every two strokes of the piston, and operating the intake and exhaust valve actuators to adjust an opening overlap between the intake poppet valve and the exhaust poppet valve to vary a resulting composition of an exhaust gas mixture provided to the exhaust passage from the cylinder via the exhaust poppet valve;

operate the cylinder in a four stroke cycle during a second operating condition by combusting an air and fuel mixture in the cylinder every four strokes of the piston.

13. The engine system of claim 12, wherein the first operating condition includes a lower engine speed and the second operating condition includes a higher engine speed.

14. The engine system of claim 12, wherein the first operating condition includes a higher engine torque output and the second operating condition includes a lower engine torque output.

15. The engine system of claim 12, wherein the first operating condition includes a lower engine temperature and the second engine operating condition includes a higher engine temperature.

16. The engine system of claim 12, wherein the control system is further configured to:

adjust the air and fuel mixture combusted in the cylinder while operating in the two stroke cycle to a richer air-fuel ratio to produce the resulting exhaust gas mixture having a leaner air-fuel ratio; and

adjust the air and fuel mixture combusted in the cylinder while operating in the four stroke to the leaner air-fuel ratio to produce the resulting exhaust gas mixture having the leaner air-fuel ratio.

17. The engine system of claim 16, further comprising:

a fuel injector configured to deliver the fuel to cylinder and wherein the control system is further configured to adjust the air and fuel mixture combusted in the cylinder by varying a pulse-width of the fuel injector;

an exhaust gas sensor arranged along the exhaust passage and configured to identify the resulting composition of the exhaust gas mixture provided to the exhaust passage; and

a boosting device arranged along the intake passage and configured to boost intake air provided to the cylinder via the intake poppet valve; and

wherein the control system is further configured to vary the level of boost provided to the cylinder by the boosting device while operating the cylinder in the two stroke cycle to further vary the resulting composition of the exhaust gas mixture.

18. The engine system of claim 12, wherein one or more of the intake valve actuator and the exhaust valve actuator include an electromagnetic valve actuator.

19. The engine system of claim 12, wherein one or more of the intake valve actuator and the exhaust valve actuator include a cam profile switching device;

and wherein the control system is further configured to actuate one or more of the intake poppet valve and the exhaust poppet valve via a first cam profile of the cam profile switching system while operating the cylinder in the two stroke cycle and actuate one or more of the intake poppet valve and the exhaust poppet valve via a second cam profile of the cam profile switching system while operating the cylinder in the four stroke cycle.

20. The engine system of claim 19, wherein one or more of the intake valve actuator and exhaust valve actuator further include a variable valve timing device configured to vary a position of at least the first cam profile relative to a position of the piston to adjust the opening overlap between the intake poppet valve and the exhaust poppet valve.