Engine control method and apparatus

• US 8,783,227 B2
• Filed: 01/24/2011
• Issued: 07/22/2014
• Est. Priority Date: 01/27/2010
• Status: Active Grant

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Yamakawa, Masahisa, Iwai, Kouhei, Oba, Shuji
• Primary Examiner(s): Vo, Hieu T
• Assistant Examiner(s): MANLEY, SHERMAN D
• Application Number:
  US13/012,406
• Publication Number:
  US 20110180038A1
• Time in Patent Office: 1,275 Days
• Field of Search: 123/254, 123/435, 123/436, 123/681, 123/682, 1235591-565, 123/605.1, 123/295, 123/299, 123/305, 123/472, 701103-105, 701/110, 701/111, 60600-603, 606/051
• US Class Current: 123/435
• 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 29/0437 Liquid cooled heat exchangers
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: F02B 3/08 Methods of operating F02B3/12 takes precedence
• 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 13/0238 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 13/0269 Controlling the valves to perform a Miller-Atkinson cycle
• CPC Class Codes: F02D 15/04 by alteration of volume of compression space without changing piston stroke
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: F02D 35/026 using an estimation
• CPC Class Codes: F02D 41/0007 for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• CPC Class Codes: F02D 41/0057 Specific combustion modes combustion modes per se F02D41/3017
• 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 41/3035 a mode being the premixed charge compression-ignition mode
• 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
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An engine is designed to allow a compression self-ignition combustion under an air-fuel ratio leaner than a stoichiometric air-fuel ratio to be performed at least in a partial-load range of the engine. Under a condition that an engine speed varies at a same load in an engine operating region of the compression self-ignition combustion, a compression end temperature Tx, which is an in-cylinder temperature just before an air-fuel mixture self-ignites, is controlled to be raised higher in a higher engine speed side than in a lower engine speed side. As one example of control for the compression end temperature Tx, an internal EGR amount is controlled to be increased larger in the higher engine speed side than in the lower engine speed side, to raise a compression initial temperature T0 which is an in-cylinder temperature at a start timing of a compression stroke. This makes it possible to perform the compression self-ignition combustion under a lean air-fuel ratio in a wider engine speed range to effectively enhance engine thermal efficiency.

Claims

1. A method for controlling an engine, comprising steps of:

allowing a compression self-ignition combustion under an air-fuel ratio leaner than a stoichiometric air-fuel ratio to be performed at least in a partial-load range of the engine, and

acquiring a compression end temperature which is an in-cylinder temperature just before an air-fuel mixture self-ignites,

wherein, under a condition that an engine speed varies at a same load in an engine operating region of the compression self-ignition combustion, the compression end temperature is controlled to be raised higher in a higher engine speed side than in a lower engine speed side.

2. The method as defined in claim 1, wherein the control for raising the compression end temperature includes a control for raising a compression initial temperature which is an in-cylinder temperature at a start timing of a compression stroke, and wherein, the compression initial temperature is controlled to be raised higher in the higher engine speed side than in the lower engine speed side.

3. The method as defined in claim 2, wherein the control for raising the compression initial temperature includes a control for performing internal EGR for causing burned gas to remain in a cylinder, and wherein, an internal EGR amount is controlled to be increased larger in the higher engine speed side than in the lower engine speed side.

4. The method as defined in claim 3, wherein, when the internal EGR is performed at a same engine speed, the internal EGR amount is increased as the load becomes lower.

5. The method as defined in claim 2, further comprising a step of raising a compression initial pressure which is an in-cylinder pressure at a start timing of a compression stroke, according to a rise in the compression initial temperature, by means of supercharging.

6. The method as defined in claim 1, further comprising a step of setting a geometric compression ratio of the engine to 16 or more.

7. The method as defined in claim 1, wherein, throughout the engine operating region subject to the compression self-ignition combustion, an excess air ratio λ

which is a ratio of an actual air-fuel ratio to the stoichiometric air-fuel ratio, is set to 2 or more.

8. An apparatus for controlling an engine, comprising:

a controller adapted to control respective sections of the engine to allow a compression self-ignition combustion under an air-fuel ratio leaner than a stoichiometric air-fuel ratio to be performed at least in a partial-load range of the engine,

wherein the controller is operable, under a condition that an engine speed varies at a same load in an engine operating region of the compression self-ignition combustion, to control a compression end temperature, which is an in-cylinder temperature just before an air-fuel mixture self-ignites, in such a manner that it is raised higher in a higher engine speed side than in a lower engine speed side.

9. The apparatus as defined in claim 8, wherein the control for raising the compression end temperature includes a control for raising a compression initial temperature which is an in-cylinder temperature at a start timing of a compression stroke, and wherein the controller is operable to control the compression initial temperature in such a manner that it is raised higher in the higher engine speed side than in the lower engine speed side.

10. The apparatus as defined in claim 9, wherein the control for raising the compression initial temperature includes a control for performing internal EGR for causing burned gas to remain in a cylinder, and wherein the controller is operable to control an internal EGR amount in such a manner that it is increased larger in the higher engine speed side than in the lower engine speed side.

11. The apparatus as defined in claim 10, wherein the controller is operable, when the internal EGR is performed at a same engine speed, to increase the internal EGR amount as the load becomes lower.

12. The apparatus as defined in claim 9, wherein the engine is equipped with a supercharger operable to supercharge fresh air, and wherein the controller is operable to activate the supercharger to raise a compression initial pressure which is an in-cylinder pressure at a start timing of a compression stroke, according to a rise in the compression initial temperature.

13. The apparatus as defined in claim 8, wherein a geometric compression ratio of the engine is set to 16 or more.

14. The apparatus as defined in claim 8, wherein the controller is operable, throughout the engine operating region subject to the compression self-ignition combustion, to set an excess air ratio λ

which is a ratio of an actual air-fuel ratio to the stoichiometric air-fuel ratio, to 2 or more.