Control device for engine

Patent metadata

Field	Value
Publication number	US-10480479-B2
Application number	US-201816058122-A
Country	US
Kind code	B2
Filing date	Aug 8, 2018
Priority date	Aug 25, 2017
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

Abstract

A control device for an engine in which partial compression-ignition combustion including SI combustion performed by forcibly combusting a portion of mixture gas inside a cylinder followed by CI combustion performed by causing the rest of the mixture gas inside the cylinder to self-ignite is executed within a part of an operating range of the engine, is provided. The device includes a detector configured to detect a parameter related to noise caused by the combustion inside the cylinder, a memory configured to store a characteristic defining a relationship between a start timing of the CI combustion and a combustion noise index, and a processor configured to specify a given combustion noise index value based on the detection value of the detector, and control the start timing of the CI combustion.

First claim

What is claimed is:

1. A control system for a compression-ignition engine, comprising:
an engine including a cylinder, a piston, a cylinder head, and a combustion chamber formed by the cylinder, the piston, and the cylinder head;
a spark plug disposed in the combustion chamber;
a fuel injection valve disposed to be oriented into the combustion chamber;
an in-cylinder pressure sensor connected to the combustion chamber and configured to detect pressure inside the combustion chamber; and
a control unit including a processor connected to the spark plug, the fuel injection valve, and the pressure sensor, and configured to output a control signal to the spark plug, the fuel injection valve, and the pressure sensor, respectively, the control unit executing:
a combustion noise index value calculating module to calculate, based on the output value of the in-cylinder pressure sensor, a first combustion noise index value that is an in-cylinder pressure level at a given high frequency, and a second combustion noise index value that is an in-cylinder pressure level at a given low frequency;
a limit value calculating module to calculate a limit value of a start timing of the CI combustion based on the first combustion noise index value and the second combustion noise index value;
an ignition timing setting module to set an ignition timing so that the start timing of the CI combustion does not advance beyond the limit value; and
a spark plug controlling module to output an ignition instruction to the spark plug at the ignition timing set by the ignition timing setting module.

2. The control system of claim 1 , wherein the control unit obtains a distribution of a plurality of combustion noise index values calculated at a plurality of time points, sets an allowable limit of the first and second combustion noise index values based on the distribution, determines a target θci that is a target start timing of the CI combustion based on the allowable limit and a characteristic, and controls the combustion inside the cylinder to achieve the determined target θci.

3. The control system of claim 1 ,
wherein the control unit is further configured to execute:
a detection period setting module to set a crank angle period in which the in-cylinder pressure sensor sequentially performs the detection; and
an amplitude value calculating module to calculate an amplitude value of the in-cylinder pressure for each frequency based on an output value of the in-cylinder pressure sensor during the detection period,

wherein the combustion noise index value calculating module calculates the first combustion noise index value and the second combustion noise index value based on an output value of the amplitude value calculating module.

4. The control system of claim 3 , wherein the limit value calculating module calculates the start timing limit value of the CI combustion based on an allowable limit map in which the allowable value of the first combustion noise index value is set higher as an engine speed increases, and an allowable limit map in which the allowable value of the second combustion noise index value is set higher as the engine speed increases.

5. The control system of claim 3 , wherein the limit value calculating module calculates the start timing limit value of the CI combustion based on an allowable limit map in which the allowable value of the first combustion noise index value is set higher as an engine load increases, and an allowable limit map in which the allowable value of the second combustion noise index value is set higher as the engine load increases.

6. A control device for an engine in which partial compression-ignition combustion including spark ignition (SI) combustion performed by forcibly combusting a portion of mixture gas inside a cylinder followed by compression ignition (CI) combustion performed by causing the rest of the mixture gas inside the cylinder to self-ignite is executed within a part of an operating range of the engine, comprising:
a detector configured to detect a parameter related to noise caused by the combustion inside the cylinder;
a memory configured to store a characteristic defining a relationship between a start timing of the CI combustion and a combustion noise index; and
a processor configured to:
specify a given combustion noise index value based on the detection value of the detector; and
control the start timing of the CI combustion based on the characteristic and the combustion noise index value.

7. The control device of claim 6 , wherein the processor obtains a distribution of a plurality of combustion noise index values calculated at a plurality of time points, sets an allowable limit of the combustion noise index value based on the distribution, determines a target θci that is a target start timing of the CI combustion based on the allowable limit and the characteristic, and controls the combustion inside the cylinder to achieve the determined target θci.

8. The control device of claim 7 , wherein the processor specifies, based on the detection value of the detector, an SI knock index value correlated with SI knock in which unburned gas outside an area of the cylinder where the SI combustion of the mixture gas occurs combusts rapidly by abnormal local self-ignition, and a CI knock index value correlated with CI knock in which noise at a lower frequency than that in the SI knock occurs during the CI combustion, as the combustion noise index value,
wherein the memory stores, as the characteristic, a first characteristic defining the relationship between the start timing of the CI combustion and the SI knock index value, and a second characteristic defining the relationship between the start timing of the CI combustion and the CI knock index value, and
wherein the processor sets an allowable limit of the SI knock index value based on a distribution of a plurality of SI knock index values specified at a plurality of time points and the first characteristic, and an allowable limit of the CI knock index value based on a distribution of a plurality of CI knock index values specified at a plurality of time points and the second characteristic, obtains a first θci limit that is a limit of the start timing of the CI combustion by which the SI knock index value is kept below the allowable limit based on the first characteristic stored in the memory, obtains a second θci limit that is a limit of the start timing of the CI combustion by which the CI knock index value is kept below the allowable limit based on the first characteristic stored in the memory, determines a timing that is the same as or later than either one of the first θci limit and the second θci limit as the target θci, and controls the combustion inside the cylinder so that the determined target θci is achieved.

9. The control device of claim 8 , wherein the processor calculates a standard deviation among the plurality of SI knock index values; sets, as the allowable limit of the SI knock index value, a value obtained by subtracting the standard deviation among the SI knock index values from a given reference limit of the SI knock index value; calculates a standard deviation among the plurality of CI knock index values; and sets, as the allowable limit of the CI knock index value, a value obtained by subtracting the standard deviation among the CI knock index values from a given reference limit of the CI knock index value.

10. A method of controlling a compression-ignition engine including a cylinder, a piston, a cylinder head, a combustion chamber formed by the cylinder, the piston, and the cylinder head, a spark plug disposed in the combustion chamber, and a fuel injection valve disposed to be oriented into the combustion chamb

Assignees

• Mazda Motor

Inventors

• Nakashima Kenichi
• Ezumi Keitaro
• Tsumura Yuichiro
• Tanaka Daisuke
• Maiguma Taiki
• Okumura Takuji
• Ashikaga Kensuke
• Higashio Masayoshi

Classifications

• F02P5/153

  dependent on combustion pressure · CPC title

• F02P5/152 Primary

  dependent on pinking (detecting or indicating knocks in internal-combustion engines G01L23/22) · CPC title

• F02P5/1502 Primary

  using one central computing unit · CPC title

• F02P5/045

  combined with electronic control of other engine functions, e.g. fuel injection (in general F02D37/02) · CPC title

• F02D2041/0015

  for engines with means for controlling swirl or tumble flow, e.g. by using swirl valves · CPC title