SUPERCHARGED DIRECT-INJECTION ENGINE

• US 20110067679A1
• Filed: 03/22/2010
• Published: 03/24/2011
• Est. Priority Date: 03/31/2009
• Status: Active Grant

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: HITOMI, Mitsuo, NISHIMOTO, Toshiaki, ARAKI, Keiji, YAMAKAWA, Masahisa, YOUSO, Takashi
• Granted Patent: US 8,468,823 B2
• Time in Patent Office: Days
• US Class Current: 123/564
• CPC Class Codes: F02D 41/3035 a mode being the premixed charge compression-ignition mode
• CPC Class Codes: F02D 41/3041 with means for triggering compression ignition, e.g. spark plug
• CPC Class Codes: F02D 41/402 Multiple injections
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Disclosed is a supercharged direct-injection engine, which comprises a supercharging device (25, 30) for compressing intake air, and an injector 10 for directly injecting fuel into a combustion chamber 5. In the engine, an excess air factor λ as a ratio of an actual air-fuel ratio to a stoichiometric air-fuel ratio, at least in an engine warmed-up mode, is set to 2 or more in the entire engine-load region. Further, compressed self-ignited combustion is performed in a low engine-load region, and a supercharging amount by the supercharging device (25, 30) is increased along with an increase in engine load in a high engine-load region to allow the excess air factor λ to be kept at 2 or more. The engine of the present invention can effectively reduce NOx emission, while improving fuel economy.

Claims

1. A supercharged direct-injection engine comprising a supercharging device for compressing intake air, and an injector for directly injecting fuel into a combustion chamber, wherein:

an excess air factor λ

as a ratio of an actual air-fuel ratio to a stoichiometric air-fuel ratio, at least in an engine warmed-up mode, is set to 2 or more in an entire engine-load region;

compressed self-ignited combustion is performed in a low engine-load region; and

a supercharging amount by the supercharging device is increased along with an increase in engine load in a high engine-load region to allow the excess air factor λ

to be kept at 2 or more.

2. The supercharged direct-injection engine as defined in claim 1, wherein:

the excess air factor λ

is gradually changed to a rich side in the range of 2 or more, along with an increase in engine load in the low engine-load region; and

a fuel injection amount of the injector and the supercharging amount by the supercharging device are increased in the high engine-load region to allow the excess air factor λ

to be kept at 2 or more.

3. The supercharged direct-injection engine as defined in claim 1, wherein:

an engine operating region for performing the compressed self-ignited combustion is set in an engine-speed region except for at least a high engine-speed region; and

spark-ignited combustion is performed in the high engine-speed region.

4. A supercharged direct-injection engine comprising:

a supercharging device for compressing intake air;

an injector for directly injecting fuel into a combustion chamber;

a compression-ratio adjuster configured to variably set a compression ratio of the engine; and

a dp/dθ

controller configured to control an increase rate of an in-cylinder combustion pressure,

wherein;

an air-fuel ratio at least in an engine warmed-up mode is set to a value leaner than a stoichiometric air-fuel ratio in an entire engine-load region; and

compressed self-ignited combustion is performed, in a first engine operating region including a low engine-load region, under a relatively high compression ratio, and, in a second engine operating region on a high engine-load side relative to the first engine operating region, under conditions that;

the compression ratio is set to a value less than that in the first engine operating region by the compression-ratio adjuster;

the increase rate of the in-cylinder combustion pressure is reduced by the dp/dθ

controller; and

a supercharging amount by the supercharging device is increased.

5. The supercharged direct-injection engine as defined in claim 4, wherein the compression-ratio adjuster is configured to change a closing timing of an intake valve to control the compression ratio, the compression-ratio adjuster being operable, during the operation of reducing the compression ratio in the second engine operating region, to increase a shift amount of the closing timing of the intake valve with respect to bottom dead center of an intake stroke.

6. The supercharged direct-injection engine as defined in claim 4, wherein the dp/dθ

controller is configured to change a fuel injection timing of the injector to control the increase rate of the combustion pressure, the dp/dθ

controller being operable, during the operation of reducing the increase rate of the combustion pressure in the second engine operating region, to change the fuel injection timing to a timing causing combustion of an air-fuel mixture to become slower.

7. The supercharged direct-injection engine as defined in claim 6, wherein the dp/dθ

controller is operable, during the operation of reducing the increase rate of the combustion pressure in the second engine operating region, to divide the fuel injection timing into a plurality of timings.