Premixed compression ignition engine and method for controlling premixed compression ignition engine

Patent metadata

Field	Value
Publication number	US-10968859-B2
Application number	US-201716464667-A
Country	US
Kind code	B2
Filing date	Nov 22, 2017
Priority date	Nov 29, 2016
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

Control is performed so as to occur SPCCI combustion in which, after an air-fuel mixture in a first area of a combustion chamber that includes an electrode portion of an ignition device is burned by receiving ignition energy, an air-fuel mixture formed in a second area located on an outer periphery of the first area is self-ignited. Control is also performed such that, in a high load operation region of an SPCCI combustion execution region, an air-fuel ratio in the entire combustion chamber becomes richer than a stoichiometric air-fuel ratio and that an air-fuel ratio of the air-fuel mixture in the first area becomes leaner than an air-fuel ratio of the air-fuel mixture in the second area.

First claim

The invention claimed is:

1. A premixed compression ignition engine that includes an engine body formed with a combustion chamber and self-ignites a mixture of fuel and air in the combustion chamber, the engine comprising:
a fuel injection device that injects fuel into the combustion chamber;
an ignition device having an electrode portion that faces an inside of the combustion chamber and ignites an air-fuel mixture in the combustion chamber to apply ignition energy to the air-fuel mixture; and
a control device that controls the ignition device and the fuel injection device so as to occur, in at least a part of an operation region of the engine, SPCCI combustion in which an air-fuel mixture formed in a first area of the combustion chamber that includes the electrode portion of the ignition device is burned by receiving the ignition energy applied from the ignition device, and thereafter, an air-fuel mixture formed in a second area of the combustion chamber located on an outer periphery of the first area is self-ignited and burned by a pressure rise in the combustion chamber due to the combustion of the air-fuel mixture in the first area,
wherein when the control device determines that the engine is operated in a high load operation region serving as an operation region in which an engine load is higher than a reference load set to a value equal to or more than half of a maximum load of the engine and in which the SPCCI combustion is executed, in a case where an air-fuel ratio of the air-fuel mixture in the first area is set to a first air-fuel ratio at an ignition timing of the ignition device and an air-fuel ratio of the air-fuel mixture in the second area is set to a second air-fuel ratio at the ignition timing, the fuel injection device is controlled so that both the first air-fuel ratio and the second air-fuel ratio become richer than a stoichiometric air-fuel ratio, that both the first air-fuel ratio and the second air-fuel ratio decrease as the engine load increases, that a decreasing rate of the second air-fuel ratio to an increase amount of the engine load is greater than a decreasing rate of the first air-fuel ratio to the increase amount of the engine load, that an air-fuel ratio in the entire combustion chamber becomes richer than the stoichiometric air-fuel ratio, and that an air-fuel ratio of the air-fuel mixture in the first area becomes leaner than an air-fuel ratio of the air-fuel mixture in the second area at the ignition timing, and
wherein when the control device determines that the engine is operated in a state in which the engine load is the reference load, the fuel injection device is controlled so that the air-fuel ratio in the entire combustion chamber becomes the stoichiometric air-fuel ratio and that the air-fuel ratio of the air-fuel mixture in the first area and the air-fuel ratio of the air-fuel mixture in the second area both become the stoichiometric air-fuel ratio at the ignition timing.

2. The premixed compression ignition engine according to claim 1 , wherein
when the control device determines that the engine is operated in the high load operation region, the fuel injection device is caused to perform a first fuel injection for injecting fuel in an intake stroke or in a first half of a compression stroke and a second fuel injection for injecting fuel after an end of the first fuel injection.

3. The premixed compression ignition engine according to claim 2 , wherein
the engine body is provided with a piston that reciprocates in a cylinder defining the combustion chamber, the piston has a crown surface facing a ceiling portion of the combustion chamber,
the ignition device is provided at a center of the ceiling portion of the combustion chamber,
the fuel injection device is provided at the center of the ceiling portion of the combustion chamber and injects fuel toward the crown surface of the piston, and
when the control device determines that the engine is operated in the high load operation region, the fuel injection device is caused to perform the first fuel injection so that an air-fuel mixture is formed in both the first area and the second area, and thereafter, the fuel injection device is caused to perform the second fuel injection so that the fuel is added to the air-fuel mixture formed in the second area.

4. The premixed compression ignition engine according to claim 1 , further comprising:
a water injection device that injects water into the combustion chamber and supplies injection water to an air-fuel mixture,
wherein when the control device determines that the engine is operated in the high load operation region, the water injection device is controlled so that the injection water exists in at least the second area at the ignition timing.

5. The premixed compression ignition engine according to claim 1 , wherein
a geometric compression ratio of the engine body is 16 or more and 35 or less.

6. A method for controlling a premixed compression ignition engine, the engine including a fuel injection device that injects fuel into a combustion chamber and an ignition device provided with an electrode portion that faces an inside of the combustion chamber and ignites a mixture of fuel and air in the combustion chamber to apply ignition energy to the mixture, where SPCCI combustion in which an air-fuel mixture formed in a first area of the combustion chamber that includes the electrode portion of the ignition device is burned by receiving the ignition energy applied from the ignition device, and thereafter, an air-fuel mixture formed in a second area of the combustion chamber located on an outer periphery of the first area is self-ignited and burned by a pressure rise in the combustion chamber due to the combustion of the air-fuel mixture in the first area is performed in at least a part of an operation region of the engine, the method comprising:
a step of determining whether or not the engine is operated in a high load operation region serving as an operation region in which an engine load is higher than a reference load set to a value equal to or more than half of a maximum load of the engine and in which the SPCCI combustion is performed; and
a step of controlling the fuel injection device executed when the engine is operated in the high load operation region, so that an air-fuel ratio in the entire combustion chamber becomes richer than a stoichiometric air-fuel ratio and that an air-fuel ratio of the air-fuel mixture in the first area becomes leaner than an air-fuel ratio of the air-fuel mixture in the second area at an ignition timing of the ignition device,
wherein in the step executed when it is determined that the engine is operated in the high load operation region, in a case where the air-fuel ratio of the mixture in the first area is set to a first air-fuel ratio at the ignition timing and the air-fuel ratio of the air-fuel mixture in the second area is set to a second air-fuel ratio at the ignition timing, the fuel injection device is controlled so that both the first air-fuel ratio and the second air-fuel ratio become richer than the stoichiometric air-fuel ratio, that both the first air-fuel ratio and the second air-fuel ratio decrease as the engine load increases, and that a decreasing rate of the second air-fuel ratio to an increase amount of the engine load is greater than a decreasing rate of the first air-fuel ratio to the increase amount of the engine load.

7. The method for controlling the premixed compression ignition engine according to claim 6 , further comprising:
a step of determining whether or not the engine is operated in a state in which the engine load is the reference load; and
a step of controlling the fuel injection device executed when it is determined that the engine is operated in the state in which

Assignees

• Mazda Motor

Inventors

• Ota Noriyuki
• Ono Ryohei

Classifications

• F02D41/3035

  a mode being the premixed charge compression-ignition mode · CPC title

• F02B11/00

  Engines characterised by both fuel-air mixture compression and air compression, or characterised by both positive ignition and compression ignition, e.g. in different cylinders · CPC title

• F02B75/02

  Engines characterised by their cycles, e.g. six-stroke · CPC title

• F02B23/02

  with compression ignition · CPC title

• F02M25/03

  into the cylinder {or the pre-combustion chamber} · CPC title