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Control system for compression-ignition engine

  • US 10,641,192 B2
  • Filed: 11/13/2018
  • Issued: 05/05/2020
  • Est. Priority Date: 12/15/2017
  • Status: Active Grant
First Claim
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1. A control system for a compression-ignition engine, comprising:

  • an engine having a combustion chamber formed by a cylinder, a piston and a cylinder head;

    an injector attached to the engine and configured to supply fuel into the combustion chamber;

    a spark plug disposed to be oriented into the combustion chamber;

    an external exhaust gas recirculation (EGR) device configured to recirculate into the combustion chamber a portion of burned gas discharged to an exhaust passage from the combustion chamber as EGR gas;

    an EGR controller configured to adjust an external EGR ratio that is a ratio of the EGR gas recirculated into the combustion chamber by the external EGR device to total gas in the combustion chamber, the EGR controller adjusting the external EGR ratio so that a compression start temperature of the combustion chamber rises as an engine speed increases; and

    a controller connected to the injector and the spark plug, and configured to output a control signal to the injector and the spark plug, respectively, the controller including a processor configured to execute a combustion controlling module to output an ignition instruction to the spark plug so as to ignite at a given ignition timing after the external EGR ratio adjustment, so that partial compression-ignition combustion in which a mixture gas combusts by flame propagation and then combusts by compression ignition is performed,wherein, during the partial compression-ignition combustion, the combustion controlling module controls the EGR controller to increase the external EGR ratio as the engine speed increases,wherein at least in a part of a low engine load segment of an engine operating range where the partial compression-ignition combustion is performed, the combustion controlling module performs the partial compression-ignition combustion while forming an air-fuel (A/F) lean environment in which an air-fuel ratio that is a ratio of air to fuel inside the combustion chamber is larger than a stoichiometric air-fuel ratio, andwherein within the operating range in which the partial compression-ignition combustion is performed in the A/F lean environment, the combustion controlling module controls the EGR controller to increase the external EGR ratio as the engine load increases, and within a higher engine load range than the operating range, the combustion controlling module performs the partial compression-ignition combustion while forming a gas-fuel (G/F) lean environment in which a gas air-fuel ratio that is a ratio of the total gas to fuel inside the combustion chamber is larger than the stoichiometric air-fuel ratio and the air-fuel ratio substantially matches with the stoichiometric air-fuel ratio.

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