Control system of compression-ignition engine

Patent metadata

Field	Value
Publication number	US-10704524-B2
Application number	US-201916415658-A
Country	US
Kind code	B2
Filing date	May 17, 2019
Priority date	May 22, 2018
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

A control system of a compression-ignition engine which performs SPCCI combustion in which mixture gas is ignited with a spark plug to be partially combusted by SI combustion and the rest of mixture gas self-ignites to be combusted by CI combustion, is provided. When the engine is operated at least in a given first operating range, a controller of the device controls a variable intake mechanism so that an A/F lean environment where an air-fuel ratio in a cylinder becomes higher than a stoichiometric air-fuel ratio is formed, while causing the spark plug to perform spark ignition at a given timing so that the mixture gas combusts by SPCCI combustion, and controls so that, under the same engine load condition, an intake valve close timing is more retarded as the engine speed decreases, within a range where an amount of air inside the cylinder decreases by retarding the close timing.

First claim

What is claimed is:

1. A control system of a compression-ignition engine including a cylinder, an intake passage, an exhaust passage, an intake port communicating the intake passage to the cylinder, an intake valve configured to open and close the intake port, an exhaust port communicating the exhaust passage to the cylinder, an exhaust valve configured to open and close the exhaust port, an injector configured to inject fuel into the cylinder, and a spark plug configured to ignite a mixture gas containing the fuel injected by the injector and air, the engine performs partial compression-ignition combustion in which the mixture gas is spark-ignited with the spark plug to be partially combusted by spark ignition (SI) combustion and the remaining mixture gas self-ignites to be combusted by compression ignition (CI) combustion, comprising:
a variable intake mechanism configured to change an open timing and a close timing of the intake valve; and
a controller including a processor configured to control parts of the engine, including the variable intake mechanism and the spark plug,
wherein when the engine is operated at least in a given first operating range, the controller controls the variable intake mechanism so that an air-fuel ratio (A/F) lean environment where an air-fuel ratio that is a ratio of air to fuel in the cylinder becomes higher than a stoichiometric air-fuel ratio is formed, while causing the spark plug to perform spark ignition at a given timing so that the mixture gas combusts by the partial compression-ignition combustion, and the controller controls the variable intake mechanism so that, under the same engine load condition, the close timing of the intake valve is more retarded as the engine speed decreases, within a range where an amount of air inside the cylinder decreases by retarding the valve close timing.

2. The control system of claim 1 , wherein the variable intake mechanism simultaneously changes the open timing and the close timing of the intake valve.

3. The control system of claim 1 , wherein
the controller controls the variable intake mechanism and the spark plug so that the partial compression-ignition combustion under the A/F lean environment is performed when the engine is operated in a second operating range set to the high load side of the first operating range, and
the controller controls the variable intake mechanism so that the close timing of the intake valve is more retarded as the engine speed increases under the same engine load condition, and a rate of change in the valve close timing becomes smaller than the rate of change in the first operating range, or controls the variable intake mechanism so that the close timing of the intake valve is fixed, regardless of the engine speed.

4. The control system of claim 3 , wherein
the controller controls the variable intake mechanism and the spark plug so that the partial compression-ignition combustion under the A/F lean environment is performed when the engine is operated in a third operating range set to a higher load side of the second operating range, and
the controller controls the variable intake mechanism in a partial range of the third operating range where the engine speed is higher so that the close timing of the intake valve is more retarded as the engine speed increases, within a range where the amount of air inside the cylinder increases by retarding the valve close timing.

5. The control system of claim 4 , wherein the controller controls the variable intake mechanism in a partial range of the third operating range where the engine speed is lower, so that the close timing of the intake valve is fixed, regardless of the engine speed, or so that the close timing of the intake valve is advanced as the engine speed increases.

6. The control system of claim 1 , further comprising a variable exhaust mechanism configured to change a close timing of the exhaust valve,
wherein the controller controls the variable exhaust mechanism so that, when the engine is operated in the first operating range, the close timing of the exhaust valve is more advanced within a range on a retarded side of an exhaust top dead center as the engine speed decreases.

7. The control system of claim 1 , wherein the cylinder includes a plurality of cylinders, and
wherein the controller controls the variable intake mechanism so that, when the engine is operated in a reduced cylinder range set as at least part of the first operating range, and a preset reduced-cylinder operation executing condition is satisfied, a reduced-cylinder operation is carried out in which only some of the cylinders are operated by injecting fuel from the injector into the cylinders, while suspending the fuel injection into the remaining cylinders, and when the reduced-cylinder operation is carried out within a higher load range of the reduced cylinder range, the close timing of the intake valve is more retarded as the engine speed increases within a range where the amount of air inside the cylinder increases by retarding the valve close timing.

8. The control system of claim 7 , wherein the controller controls an exhaust variable mechanism configured to change the close timing of the exhaust valve so that, when the reduced-cylinder operation is carried out in a higher load range of the reduced cylinder range, the close timing of the exhaust valve is more advanced as the engine speed increases within a range on a retarded side of an exhaust top dead center.

9. The control system of claim 1 , wherein the controller sets a target SI ratio that is a target value of a ratio of an amount of heat generation by SI combustion to a total amount of heat generation in one cycle according to an engine operating condition when performing the partial compression-ignition combustion, and sets an ignition timing of the spark plug based on the target SI ratio.

Assignees

• Mazda Motor

Inventors

• SUEOKA Masanari
• Inoue Atsushi
• Maruyama Keiji
• Ohura Takuya
• Nishida Tomohiro
• Kawai Yusuke
• Chikada Tetsuya
• Tokunaga Tatsuhiro

Classifications

• F02D13/0219

  by shifting the phase, i.e. the opening periods of the valves are constant · CPC title

• F02D13/0215 Primary

  changing the valve timing only · CPC title

• F01L1/34

  characterised by the provision of means for changing the timing of the valves without changing the duration of opening {and without affecting the magnitude of the valve lift} · CPC title

• F02B31/085

  having two inlet valves · CPC title

• F02D2200/101

  Engine speed · CPC title