CONTROL DEVICE OF SPARK-IGNITION GASOLINE ENGINE

• US 20120216776A1
• Filed: 02/07/2012
• Published: 08/30/2012
• Est. Priority Date: 02/24/2011
• Status: Active Grant

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Nagatsu, Kazuhiro, Yamakawa, Masahisa, Iwai, Kouhei, Ota, Noriyuki, Watanabe, Kazutoyo, Watanabe, Naoya, Kurita, Hiroyuki, Oba, Shuji, Nou, Yoshihisa, Koga, Tatsuya
• Granted Patent: US 8,838,364 B2
• Time in Patent Office: Days
• US Class Current: 123/305
• 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 23/101 the injector being placed on or close to the cylinder centre axis, e.g. with mixture formation using spray guided concepts
• CPC Class Codes: F02B 29/0418 the intake air cooler having a bypass or multiple flow paths within the heat exchanger to vary the effective heat transfer surface
• CPC Class Codes: F02B 29/0437 Liquid cooled heat exchangers
• CPC Class Codes: F02D 13/0234 changing the valve timing only
• CPC Class Codes: F02D 13/0242 Variable control of the exhaust valves only
• CPC Class Codes: F02D 13/0273 Multiple actuations of a valve within an engine cycle
• CPC Class Codes: F02D 41/0057 Specific combustion modes combustion modes per se F02D41/3017
• CPC Class Codes: F02D 41/3041 with means for triggering compression ignition, e.g. spark plug
• CPC Class Codes: F02D 41/3836 Controlling the fuel pressure
• 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: F02M 26/25 with coolers having bypasses
• CPC Class Codes: F02M 26/28 with liquid-cooled heat exchangers
• CPC Class Codes: F02M 26/47 the characteristics being temperatures, pressures or flow rates
• CPC Class Codes: F02M 35/10177 Engines having multiple fuel injectors or carburettors per cylinder
• CPC Class Codes: F02M 35/1038 for temperature or pressure
• CPC Class Codes: F02M 35/10386 for flow rate air flow meters in air cleaners F02M35/021; circuit arrangements for generating control signals by measuring intake air flow F02D41/18
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A control device of a spark-ignition gasoline engine is provided. The control device includes a controller for operating the engine body by controlling at least a fuel injection valve, an ignition plug, and a fuel pressure variable mechanism. Depending on the engine load range, the controller sets the combustion mode to a compression-ignition mode or a spark-ignition mode. In each mode, the controller also controls the fuel pressure, and the timing of fuel injection and ignition. The controller may also performs external EGR control in each mode.

Claims

1. A control device of a spark-ignition gasoline engine, comprising:

an engine body having a cylinder of which a geometric compression ratio is set to 14;

1 or above, and being supplied with fuel containing at least gasoline;

a fuel injection valve for injecting the fuel into the cylinder;

an ignition plug arranged to be oriented inside the cylinder and for igniting an air-fuel mixture within the cylinder;

a fuel pressure variable mechanism for changing a pressure of the fuel that is injected by the fuel injection valve; and

a controller for operating the engine body by controlling at least the fuel injection valve, the ignition plug, and the fuel pressure variable mechanism,

wherein when an operating state of the engine body is within a predetermined low engine load range, the controller sets a combustion mode to a compression-ignition mode in which a compression-ignition combustion is performed,

wherein when the operating state is within a high engine load range where an engine load is higher than the compression ignition mode, the controller sets the combustion mode to a spark-ignition mode in which the controller controls the fuel pressure variable mechanism so that the fuel pressure is higher than that within a lower-half engine load range of the compression-ignition mode, the controller also operates the fuel injection valve to perform at least a fuel injection during a retard period from a late stage of compression stroke to an early stage of expansion stroke, and the controller also operates the ignition plug to ignite during the retard period and after the fuel injection,

wherein when the operating state is within a range where the engine load is higher than a predetermined engine load of the spark-ignition mode, the controller performs an external EGR control of circulating a part of the burned gas back to an intake system of the engine body through an EGR passage, and the controller also controls an EGR ratio to be relatively high when the engine load is low in the spark-ignition mode, and

wherein when the operating state is within a range where the engine load is below the predetermined load of the spark-ignition mode, the controller performs the external EGR control while setting the EGR ratio higher than that within the range where the engine load is higher than the predetermined engine load, and also performs a charging amount control of reducing an intake air charging amount to be less than in the compression-ignition mode.

2. The control device of claim 1, wherein in the spark-ignition mode, the controller operates the engine body at an air-fuel ratio λ

=1.

3. The control device of claim 1, wherein in the spark-ignition mode, the fuel pressure variable mechanism sets the fuel pressure to 40 MPa or above.

4. The control device of claim 1, wherein within the range where the engine load is below the predetermined engine load of the spark-ignition mode, the controller sets the EGR ratio to 30% or above.

5. The control device of claim 1, wherein in the spark-ignition mode, the controller operates the fuel injection valve to perform a plurality of fuel injections and sets a timing of the final fuel injection among the plurality of fuel injections to be during the retard period.

6. The control device of claim 1, wherein within the range where the engine load is below the predetermined engine load of the spark-ignition mode, the controller adjusts the EGR ratio by performing a throttle control of a throttle valve that is provided within an intake passage.

7. The control device of claim 1, further comprising a variable valve mechanism (VVL) for changing an actuation state of an exhaust valve,

wherein in the compression-ignition mode, the controller adjusts the EGR ratio by opening the exhaust valve twice during an exhaust stroke and an intake stroke, respectively.

8. The control device of claim 1, wherein in the compression-ignition mode (CI), a ratio of an amount of fresh air and an amount of EGR gas is adjusted by fully opening a throttle valve that is provided within an intake passage, fully closing an EGR valve that is provided within the EGR passage, setting closing timings of an exhaust valve and an intake valve to predetermined constant timings, respectively, advancing an opening timing of the intake valve as the engine load increases, and increasing a lift of the intake valve corresponding to an increase of the engine load.

9. The control device of claim 1, wherein in the spark-ignition mode (SI), a ratio of an amount of fresh air and an amount of EGR gas is adjusted by keeping a throttle valve provided within an intake passage fully opened, setting opening and closing timings of an intake valve constant, keeping a lift of the intake valve at a maximum value, and adjusting an opening of an EGR valve that is provided within the EGR passage.

10. The control device of claim 1, wherein in the compression-ignition mode (CI), a ratio of an amount of fresh air and an amount of EGR gas is adjusted by increasing an opening of a throttle valve that is provided within an intake passage corresponding to an increase of the engine load, fully closing an EGR valve that is provided within the EGR passage, setting closing timings of an exhaust valve and an intake valve to a predetermined constant timings, respectively, setting an opening timing of the intake valve to be constant regardless of the engine load, and setting a lift of the intake valve to be constant regardless of the engine load.

11. The control device of claim 1, wherein in the spark-ignition mode (SI), a switching range is set within a middle engine load range relating to a switch to the compression-ignition mode, and

wherein within the switching range, a ratio of an amount of fresh air and an amount of EGR gas is adjusted by throttling a throttle valve that is provided within an intake passage rather than a fully opened state, fully opening an EGR valve that is provided within the EGR passage, retarding a closing timing of an intake valve as the engine load increases, setting an opening timing of the intake valve and a closing timing of an exhaust valve constant, and keeping a lift of the intake valve at a maximum value.

12. The control device of claim 1, wherein the controller calculates a knock variable and then calculates the fuel pressure in the spark-ignition mode (SI) based on the knock variable.

13. The control device of claim 1, wherein the controller calculates a knock variable and then calculates a ratio of the fuel injection during the retard period of the spark-ignition mode (SI) to a total injection amount based on the knock variable.

14. The control device of claim 1, wherein the controller calculates a knock variable and then calculates a retarding amount of an injection timing in the spark-ignition mode (SI) based on the knock variable.

15. The control device of claim 1, wherein the controller determines to switch the combustion mode to either one of the compression-ignition mode and the spark-ignition mode based on a determination variable that is calculated from an accelerator opening, an engine speed, a charging amount of intake air, an engine coolant temperature, and an intake air temperature.

16. A method of controlling a spark-ignition gasoline engine including an engine body having a cylinder of which a geometric compression ratio is set to 14:

1 or above, and being supplied with fuel containing at least gasoline, a fuel injection valve for injecting the fuel into the cylinder, an ignition plug arranged to be oriented inside the cylinder and for igniting air-fuel mixture within the cylinder, and a fuel pressure variable mechanism for changing a pressure of the fuel that is injected by the fuel injection valve, the engine operating the engine body by controlling at least the fuel injection valve, the ignition plug, and the fuel pressure variable mechanism, the method comprising;

setting, when an operating state of the engine body is within a predetermined low engine load range, a combustion mode to a compression-ignition mode in which a compression-ignition combustion is performed;

setting, when the operating state is within a high engine load range where an engine load is higher than the compression ignition mode, the combustion mode to a spark-ignition mode in which the controller controls the fuel pressure variable mechanism so that the fuel pressure is higher than that within a lower-half engine load range of the compression-ignition mode, also operating the fuel injection valve to perform at least a fuel injection during a retard period from a late stage of compression stroke to an early stage of expansion stroke, and also operating the ignition plug to ignite during the retard period and after the fuel injection;

performing, when the operating state is within a range where the engine load is higher than a predetermined engine load of the spark-ignition mode, an external EGR control of circulating a part of the burned gas back to an intake system of the engine body through an EGR passage, and also controlling an EGR ratio to be relatively high when the engine load is low in the spark-ignition mode; and

performing, when the operating state is within a range where the engine load is below the predetermined engine load of the spark-ignition mode, the external EGR control while setting the EGR ratio higher than that within the range where the engine load is higher than the predetermined engine load, and also a charging amount control of reducing an intake air charging amount to be less than in the compression-ignition mode.