METHOD OF OPERATING AN INTERNAL COMBUSTION ENGINE

• US 20080178836A1
• Filed: 01/11/2008
• Published: 07/31/2008
• Est. Priority Date: 01/30/2007
• Status: Active Grant

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Yamashita, Hiroyuki, Tanaka, Tatsuya, Watanabe, Tomomi
• Granted Patent: US 7,669,578 B2
• Time in Patent Office: Days
• US Class Current: 123/295
• 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 17/00 Engines characterised by means for effecting stratification of charge in cylinders
• 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 2275/16 Indirect injection
• CPC Class Codes: F02D 13/0211 the change of valve timing is caused by the change in valve lift, i.e. both valve lift and timing are functionally related
• CPC Class Codes: F02D 13/0265 Negative valve overlap for temporarily storing residual gas in the cylinder
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 41/006 using internal EGR control of valve overlap for internal EGR F02D13/0261; arrangements for internal EGR F02M26/01
• CPC Class Codes: F02D 41/3041 with means for triggering compression ignition, e.g. spark plug
• CPC Class Codes: F02D 41/3047 said means being a secondary injection of fuel
• CPC Class Codes: F02D 41/3064 with special control during transition between modes
• CPC Class Codes: F02M 26/01 Internal exhaust gas recirculation, i.e. wherein the residual exhaust gases are trapped in the cylinder or pushed back from the intake or the exhaust manifold into the combustion chamber without the use of additional passages
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A method of operating an internal combustion engine having a combustion chamber with a piston and a spark plug, comprising during a first mode, bringing the temperature of the combustion chamber to auto-ignition temperature by adjusting engine operating conditions and producing auto-ignition in said combustion chamber without requiring spark from said spark plug; and during a second mode, bringing the temperature of the combustion chamber close to auto-ignition temperature by adjusting engine operating conditions, forming a small cloud of stratified air-fuel mixture near said spark plug, igniting said fuel cloud by a spark form said spark plug, and then causing cylinder pressure to rise, thereby producing auto-ignition at other sites in said combustion chamber wherein said first mode is implemented in a first operating range and said second mode is implemented only in a second operating range where engine speed and load are lower than said first operating range.

Claims

1. A method of operating an internal combustion engine having a combustion chamber with a piston and a spark plug, comprising:

during a first mode, bringing the temperature of the combustion chamber to auto-ignition temperature by adjusting engine operating conditions and producing auto-ignition in said combustion chamber without requiring spark from said spark plug; and

during a second mode, bringing the temperature of the combustion chamber close to auto-ignition temperature by adjusting engine operating conditions, forming a small cloud of stratified air-fuel mixture near said spark plug, igniting said fuel cloud by a spark form said spark plug, and then causing cylinder pressure to rise, thereby producing auto-ignition at other sites in said combustion chamber;

wherein said first mode is implemented in a first operating range and said second mode is implemented only in a second operating range where engine speed and load are lower than said first operating range.

2. The method as described in claim 1 further comprising producing substantially homogenous air-fuel mixture at said other sites in said combustion chamber by providing fuel into said combustion chamber in at least an intake stroke of said piston, and wherein said small cloud of stratified air-fuel mixture is formed by providing fuel into said combustion chamber in at least a compression stroke of said piston.

3. The method as described in claim 2, wherein said spark ignites said fuel cloud such that said auto-ignition of said substantially homogenous air-fuel mixture is produced at predetermined timing near the top dead center of said compression stroke.

4. The method as described in claim 2, wherein said providing fuel into said combustion chamber in at least a compression stroke includes providing a specific amount of fuel into said combustion chamber, which is independent from said engine load.

5. The method as described in claim 3, wherein said adjusting engine operating conditions comprises adjusting at least intake and exhaust valve timing of said engine.

6. The method as described in claim 5, wherein said adjusting at least of intake and exhaust valve timing of said engine includes providing a negative overlap period wherein both of an intake and an exhaust valve are closed to increase temperature inside of said combustion chamber by using burned gas kept in said combustion chamber.

7. The method as described in claim 6, further comprising producing active air-fuel mixture having high ignition performance by injecting fuel directly into said combustion chamber in said negative overlap period.

8. The method as described in claim 7, wherein said engine comprises a first injector capable of injecting fuel into said combustion chamber directly and a second injector capable of injecting fuel into a intake air passage of said engine, and wherein said active air-fuel mixture is produced by injecting fuel directly into said combustion chamber with said first injector in said negative overlap period, said substantially homogenous air-fuel mixture is produced in said combustion chamber by injecting fuel with said second injector in said intake stroke and said small cloud of stratified air-fuel mixture is formed near said spark plug by injecting fuel directly near said spark plug with said first injector in said compression stroke.

9. The method as described in claim 1, further comprising a third mode where substantially homogenous air-fuel mixture having substantially stoichiometric air fuel ratio is produced in said combustion chamber and said spark plug ignites said substantially homogenous air-fuel mixture, wherein said third mode is implemented in a third operating range where engine speed and load are lower than said second operating range.

10. The method as described in claim 9, further comprising:

for a predetermined time period in transition between said second mode and said third mode, producing only stratified air-fuel mixture in said combustion chamber by providing fuel into said combustion chamber directly in compression stroke and igniting said stratified air-fuel mixture by said spark plug.

11. A method of operating an internal combustion engine having a combustion chamber with a piston and a spark plug, comprising:

during a first mode, bringing the temperature of the combustion chamber to auto-ignition temperature by adjusting engine operating conditions and producing auto-ignition in said combustion chamber with no spark from said spark plug;

during a second mode, bringing the temperature of the combustion chamber close to auto-ignition temperature by adjusting engine operating conditions, forming a small cloud of stratified air-fuel mixture near said spark plug, igniting said fuel cloud by a spark form said spark plug, and then causing cylinder pressure to rise, thereby producing auto-ignition at other sites in said combustion chamber; and

during a third mode, producing substantially homogenous air-fuel mixture having substantially stoichiometric air fuel ratio in said combustion chamber and igniting said substantially homogenous air-fuel mixture by a spark form said spark plug;

wherein said first mode is implemented in a first operating range, said second mode is implemented only in a second operating range where engine speed and load are lower than said first operating range and said third mode is implemented in a third operating range where engine speed and load are lower than said second operating range; and

wherein, for a predetermined time period in transition between said second mode and said third mode, only stratified air-fuel mixture is produced in said combustion chamber by providing fuel into said combustion chamber directly in a compression stroke and said stratified air-fuel mixture is ignited by a spark form said spark plug.

12. An engine operating system for operating an internal combustion engine having a combustion chamber with a piston and a spark plug, comprising:

a speed sensor for detecting a value related to engine speed;

an engine load sensor for detecting a value related to engine load;

an actuator for driving at least one engine component except for said spark plug, capable of adjusting the temperature of inside of said combustion chamber; and

a controller configured to;

communicate with said speed sensor and said engine load sensor;

receive signals related to engine speed and signals related to engine load from said sensors;

when said engine is in a first operating range, control said actuators so that the temperature of said combustion chamber reaches an auto-ignition temperature and auto-ignition in said combustion chamber is produced without requiring spark from said spark plug; and

only when said engine is in a second operating range where engine speed and load are lower than said first operating range, control said actuators so that the temperature of said combustion chamber approaches to the auto-ignition temperature, control a fuel injector so that a small cloud of stratified air-fuel mixture is formed near said spark plug, and control said spark plug so that said fuel cloud is ignited and then cylinder pressure is raised, thereby producing the auto-ignition at other sites in said combustion chamber.

13. The system as described in claim 12, wherein said engine components comprise an intake valve and an exhaust valve of said engine;

and

wherein said controller is configured to operate at least one of each actuators provided for at least one of said intake and exhaust valve so that there is a negative overlap period wherein both of said intake and exhaust valve are closed in at least part of the exhaust stroke of said piston and at least part of the intake stroke of said piston to increase temperature inside of said combustion chamber by using burned gas kept in said combustion chamber.

14. The system as described in claim 13, wherein, when said engine is in said second operating range, said controller is configured to operate a first fuel injector so that substantially homogenous air-fuel mixture is produced in said combustion chamber by providing fuel at least in said intake stroke and then to operate a second injector so that said small cloud of stratified air-fuel mixture is produced near said spark plug by providing fuel in said compression stroke.

15. The system as described in claim 14, wherein said controller is configured to operate said spark plug so that a spark from said spark plug ignites said small cloud of stratified air-fuel mixture such that said auto-ignition of said substantially homogenous air-fuel mixture is produced at a predetermined timing near the top dead center of said compression stroke.

16. The system as described in claim 14, wherein said controller is configured to operate said second injector so that a specific amount of fuel is provided to said combustion chamber, which is independent from the engine load, to produce said small cloud of stratified air-fuel mixture.

17. The system as described in claim 14, wherein said controller is configured to operate said second injector so that an active air-fuel mixture having high ignition performance is produced in said combustion chamber by injecting fuel into said combustion chamber in said negative overlap period.

18. The system as described in claim 14, wherein said first injector is provided so that said first injector can inject fuel into an intake passage and said second injector is provided so that said second injector can inject fuel directly into said combustion chamber.

19. The system as described in claim 12, wherein said controller is further configured to control a fuel injector in a third operating range where engine speed and load are lower than said second operating range so that a substantially homogenous air-fuel mixture having substantially stoichiometric air fuel ratio is produced in said combustion chamber, and then control said spark plug so that said substantially homogenous air-fuel mixture combusts.

20. The system as described in claim 19, wherein said controller is further configured to control said fuel injector for a predetermined time period in engine condition transition between said second operating range and said third operating range so that only stratified air-fuel mixture is produced in said combustion chamber by providing fuel into said combustion chamber directly in compression stroke and then control said spark plug so that said stratified air-fuel mixture combusts.