Model-based combustion timing and torque control for internal combustion engine assemblies

Patent metadata

Field	Value
Publication number	US-2019128233-A1
Application number	US-201715796019-A
Country	US
Kind code	A1
Filing date	Oct 27, 2017
Priority date	Oct 27, 2017
Publication date	May 2, 2019
Grant date	—

Abstract

Disclosed are model-based combustion timing systems and control logic for engine assemblies, methods for making/operating such engine assemblies, and motor vehicles with spark-ignited engine assemblies implementing model-based combustion timing. A method for controlling torque output of an engine assembly includes receiving a requested torque demand for the engine, and determining a current fuel command and valve timing for the engine's power cylinder(s). A first math model is used to determine a desired CA50 based on the requested torque demand, a power cylinder indicated mean effective pressure (IMEP), an expander cylinder IMEP, and the current fuel command/valve timing. A second math model is used to determine a maximum brake torque (MBT) CA50 based on power cylinder and expander cylinder IMEPs, and current fuel command/valve timing. An engine control unit determines a final spark timing based on a correlation between the desired CA50 and MBT CA50, modified by a spark timing gain.

First claim

1 . A method for controlling torque output of an engine assembly, the engine assembly including an engine block with a power cylinder of a first size selectively fluidly coupled to an expander cylinder of a second size, pistons each reciprocally movable in a respective one of the power and expander cylinders, and an electronic igniter controlled by an engine control unit (ECU) to ignite a cylinder charge in the power cylinder, the method comprising:
receiving, via the ECU, an input signal indicative of a requested torque demand for the engine assembly; determining, via the ECU, a current fuel command and/or a current valve timing for the power cylinder; determining, from a first math model, a desired CA50 (a crank angle where 50 percent of a mass of injected fuel is combusted within the power cylinder) based on the requested torque demand, a power cylinder indicated mean effective pressure (IMEP), an expander cylinder IMEP, and the current fuel command and/or the current valve timing; determining, from a second math model, a maximum brake torque (MBT) CA50 based on the power cylinder IMEP, the expander cylinder IMEP, and the current fuel command and/or the current valve timing; determining, via the ECU, a final spark timing based on a CA50-spark correlation, the CA50-spark correlation including a correlation between the desired CA50 and the MBT CA50; and modulating a torque output of the engine assembly by controlling activation of the electronic igniter by the ECU based on the determined final spark timing.

2 . The method of claim 1 , wherein the first math model is an inverse CA50 end of combustion (EOC) model in which:

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Assignees

• Gm Global Tech Operations Llc

Inventors

• Zhao Junfeng
• Kang Jun-Mo
• Hu Yiran

Classifications

• F02D2250/18

  Control of the engine output torque · CPC title

• F02P5/142

  dependent on a combination of several specific conditions (F02P5/075, F02P5/106 takes precedence) · CPC title

• F02P5/1502 Primary

  using one central computing unit · CPC title

• F02B75/02

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

• F02P5/153

  dependent on combustion pressure · CPC title