Combustion control device for compression autoignition engine

Patent metadata

Field	Value
Publication number	US-10677187-B2
Application number	US-201616087053-A
Country	US
Kind code	B2
Filing date	Nov 25, 2016
Priority date	Nov 25, 2016
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

A combustion control device for a compression autoignition engine includes an engine, a state quantity setting device, a spark plug, a controller, and a sensor. The spark plug receives a control signal from the controller and ignites air-fuel mixture at predetermined ignition timing such that the ignited air-fuel mixture is combusted by flame propagation and then unburned air-fuel mixture in a combustion chamber is combusted by autoignition. The controller outputs a control signal to an injector such that, in a compression stroke, fuel is injected at specific timing at which a line obtained by extending an axis of each hole of the injector overlaps with a specific portion including an opening edge of a cavity in an upper surface of a piston.

First claim

The invention claimed is:

1. A combustion control device for a compression autoignition engine, the combustion control device comprising:
an engine configured to cause autoignition of air-fuel mixture in a combustion chamber formed by a cylinder and a piston;
a state quantity setting device mounted to the engine, the state quantity setting device configured to set an inside of the combustion chamber to a desired state by adjusting introduction of fresh air and burned gas into the combustion chamber;
an injector mounted to a roof of the combustion chamber, the injector configured to inject fuel into the combustion chamber;
a spark plug disposed so as to face the inside of the combustion chamber, the spark plug configured to ignite air-fuel mixture in the combustion chamber;
a controller connected to the state quantity setting device, the injector, and the spark plug, the controller configured to operate the engine by outputting control signals to the state quantity setting device, the injector, and the spark plug; and
a sensor connected to the controller, the sensor configured to detect a parameter regarding an operation state of the engine and output a detection signal to the controller, wherein
the piston has a cavity that is recessed from an upper surface of the piston and that faces the injector,
the injector has a plurality of holes each having a hole axis inclined relative to a cylinder axis of the cylinder and injects the fuel toward the upper surface of the piston,
the spark plug receives a control signal from the controller and ignites the air-fuel mixture at predetermined ignition timing such that the ignited air-fuel mixture is combusted by flame propagation and then unburned air-fuel mixture in the combustion chamber is combusted by autoignition,
the controller outputs a control signal to the injector such that, in a compression stroke, the fuel is injected at specific timing at which a line obtained by extending the axis of each hole of the injector overlaps with a specific portion including an opening edge of the cavity in the upper surface of the piston,
when the operation state of the engine is in a predetermined operation region based on a detection signal from the sensor, the controller outputs control signals to the state quantity setting device, the injector, and the spark plug such that the ignited air-fuel mixture is combusted by flame propagation and then unburned air-fuel mixture in the combustion chamber is combusted by autoignition,
when the operation state of the engine is in a low load region in which a load is lower than that in the predetermined operation region, or in a high load region in which the load is higher than that in the predetermined operation region, based on a detection signal from the sensor, the controller outputs control signals to the state quantity setting device, the injector, and the spark plug such that air-fuel mixture in the combustion chamber is combusted by flame propagation without occurrence of combustion by autoignition,
the predetermined operation region includes an undivided injection region in which the load is lower than a predetermined load, and
when the operation state of the engine is in the undivided injection region, the controller outputs a control signal to the injector such that the fuel is injected at once at the specific timing.

2. The combustion control device for the compression autoignition engine of claim 1 , wherein
the injector is disposed at a center portion of the combustion chamber such that a central axis of the injector is parallel to the cylinder axis of the cylinder, and injects the fuel from the center portion of the combustion chamber toward a radially outer side, and
the cavity is located on an extension of the central axis of the injector.

3. The combustion control device for the compression autoignition engine of claim 1 , wherein
the state quantity setting device has a supercharging system mounted to the engine and configured to perform supercharging with gas to be introduced into the combustion chamber,
the predetermined operation region is divided into a supercharge region and a non-supercharge region in which the load is lower than that in the supercharge region,
the supercharging system receives a control signal from the controller, performs supercharging when the operation state of the engine is in the supercharge region, and does not perform supercharging when the operation state of the engine is in the non-supercharge region, and
the undivided injection region is included in the non-supercharge region.

4. The combustion control device for the compression autoignition engine of claim 3 , wherein: when the operation state of the engine is in the predetermined operation region, the controller sets an SI rate representing an index associated with a ratio of an amount of heat generated when air-fuel mixture is combusted by the flame propagation, relative to a total amount of heat generated when air-fuel mixture in the combustion chamber is combusted, such that the SI rate is less than 100%; and when the operation state of the engine is in the supercharge region, the controller sets the SI rate such that the SI rate is higher than that when the operation state of the engine is in the non-supercharge region.

5. The combustion control device for the compression autoignition engine of claim 1 , wherein, when the operation state of the engine is in the low load region, the controller outputs a control signal to the injector such that the fuel is injected in the intake stroke.

6. The combustion control device for the compression autoignition engine of claim 1 , wherein the specific timing is 70±5° C.A before a compression top dead center.

7. The combustion control device for the compression autoignition engine of claim 1 , further comprising a fuel supply system connected to the injector and configured to supply the fuel to the injector, wherein
when the fuel is injected at the specific timing, the controller outputs a control signal to the fuel supply system such that a pressure of the fuel is a predetermined pressure or greater.

8. The combustion control device for the compression autoignition engine of claim 1 , wherein the controller sets a state inside the combustion chamber such that a G/F representing an index associated with a mass ratio between total gas and the fuel in the combustion chamber is in a range from 18.5 to 30 and an excess air ratio X is 1.0±0.2, by outputting control signals to the state quantity setting device and the injector.

Assignees

• Mazda Motor

Inventors

• Matsumoto Kota
• Urushihara Tomonori
• Inoue Atsushi
• Kawai Yusuke
• Miyamoto Toru
• Koshiro Yudai

Classifications

• F02B23/0669

  having multiple fuel spray jets per injector nozzle · CPC title

• Y02T10/144

  Cross-Sectional Technologies · mapped topic

• F02D41/0052

  Feedback control of engine parameters, e.g. for control of air/fuel ratio or intake air amount · CPC title

• F02B1/08

  with separate admission of air and fuel into cylinder · 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