Control system for compression-ignition engine and method of determining in-cylinder temperature

Patent metadata

Field	Value
Publication number	US-10900460-B2
Application number	US-201916450792-A
Country	US
Kind code	B2
Filing date	Jun 24, 2019
Priority date	Jul 26, 2018
Publication date	Jan 26, 2021
Grant date	Jan 26, 2021

Abstract

A control system for a compression-ignition engine includes a combustion chamber, an injector, an ignition plug, a sensor device, and a controller having a circuitry. The ignition plug forcibly ignites mixture gas to start combustion accompanied by flame propagation of a part of the mixture gas, and again ignites remaining unburnt mixture gas at a timing at which the unburnt mixture gas combusts by self-ignition. The controller is configured to execute an ignition controlling module to output an ignition signal to the ignition plug before a target timing so that the unburnt mixture gas self-ignites at the target timing, an ignition timing estimating module to estimate an actual CI timing indicative of a timing at which the unburnt mixture gas actually self-ignited based on an in-cylinder pressure parameter, and an in-cylinder temperature determining module to determine the in-cylinder temperature at a given crank angle based on the estimated result.

First claim

What is claimed is:

1. A control system for a compression-ignition engine, comprising:
a combustion chamber of the engine defined by a cylinder, a piston configured to reciprocate in the cylinder, and a cylinder head closing one end of the cylinder;
an injector attached to the cylinder head and configured to inject fuel to be supplied into the combustion chamber;
an ignition plug disposed so as to be oriented in the combustion chamber and configured to ignite a mixture gas inside the combustion chamber;
a sensor device configured to measure a parameter related to operation of the engine and send a measurement signal; and
a controller having circuitry connected with the ignition plug, the injector, and the sensor device, and configured to perform a calculation in response to the measurement signal from the sensor device and output a signal to the ignition plug and the injector,
wherein the ignition plug forcibly ignites the mixture gas to start combustion accompanied by flame propagation of a portion of the mixture gas, and again ignites a remaining portion of unburnt mixture gas at a timing at which the unburnt mixture gas combusts by self-ignition,
wherein the controller is configured to execute:
an ignition controlling module to output an ignition signal to the ignition plug before a target timing so that the unburnt mixture gas self-ignites at the target timing;
an ignition timing estimating module to estimate an actual compression ignition (CI) timing indicative of a timing at which the unburnt mixture gas actually self-ignites based on an in-cylinder pressure parameter related to a pressure inside the combustion chamber measured by the sensor device; and
an in-cylinder temperature determining module to determine the in-cylinder temperature at a given crank angle based on the estimated result by the ignition timing estimating module,

wherein the controller calculates a crank angle at which a combustion mass ratio becomes a given value based on the parameter measured by the sensor device, and
wherein the in-cylinder temperature determining module determines the in-cylinder temperature based on the actual CI timing and the crank angle.

2. The control system of claim 1 , further comprising an exhaust gas recirculation (EGR) system connected with the controller and configured to adjust the in-cylinder temperature in response to a signal from the controller,
wherein the controller outputs the signal to the EGR system so as to reduce the in-cylinder temperature when the in-cylinder temperature determining module determines that the in-cylinder temperature is high, and raise the in-cylinder temperature when the in-cylinder temperature determining module determines that the in-cylinder temperature is low.

3. The control system of claim 2 ,
wherein the controller calculates a target value of a property corresponding to an operating state of the engine, and determines a target in-cylinder temperature corresponding to the target value, and
wherein the in-cylinder temperature determining module estimates the in-cylinder temperature based on the actual CI timing, and the in-cylinder temperature determining module determines the in-cylinder temperature is high when the estimated result is higher than the target in-cylinder temperature, and determines that the in-cylinder temperature is low when the estimated result is lower than the target in-cylinder temperature.

4. The control system of claim 3 , wherein the controller controls the signal outputted to the EGR system based on a difference between the estimated value of the in-cylinder temperature and the target in-cylinder temperature.

5. The control system of claim 3 , wherein the in-cylinder temperature determining module estimates the in-cylinder temperature higher as the actual CI timing becomes earlier.

6. The control system of claim 1 ,
wherein the controller determines a target value of a heat amount ratio as an index related to a ratio of an amount of heat generated when the mixture gas combusts by flame propagation to the entire amount of heat generated when the mixture gas inside the combustion chamber combusts, and determines a target value of the timing at which the unburnt mixture gas self-ignites,
wherein the controller determines the target in-cylinder temperature based on the target value, and
wherein the controller outputs the signal to the ignition plug so that the target in-cylinder temperature is achieved.

7. The control system of claim 2 ,
wherein the EGR system is provided to the engine and configured to change an amount of EGR gas included in the mixture gas inside the combustion chamber, and
wherein the EGR system comprises at least one of:
an internal EGR system configured to adjust a length of an overlap period where both an intake valve and an exhaust valve open; and
an external EGR system configured to adjust a flow rate of exhaust gas through an EGR passage connected between an air intake passage and an exhaust passage.

8. The control system of claim 1 , wherein the ignition timing estimating module estimates a timing at which the in-cylinder pressure parameter measured by the sensor device exceeds a threshold after the forced ignition by the ignition plug, as the actual CI timing.

9. The control system of claim 8 ,
wherein the sensor device includes an in-cylinder pressure sensor disposed so as to be oriented in the combustion chamber and configured to measure the pressure inside the combustion chamber, and
wherein the ignition timing estimating module uses a measurement signal of the in-cylinder pressure sensor as the signal indicative of the in-cylinder pressure parameter.

10. The control system of claim 9 ,
wherein the controller has a first band-pass filter configured to pass a signal component of the measurement signal of the in-cylinder pressure sensor, at a frequency higher than a first frequency and lower than a second frequency, and
wherein the ignition timing estimating module estimates a timing at which the measurement signal passed the first band-pass filter exceeds a first threshold, as the actual CI timing, and the first frequency and the second frequency are set within a range of 0.5 kHz to 4.0 kHz.

11. The control system of claim 9 ,
wherein the controller has a second band-pass filter configured to pass a signal component of the measurement signal of the in-cylinder pressure sensor, at a frequency higher than a third frequency and lower than a fourth frequency, and
wherein the controller has a second ignition timing estimating module configured to estimate a timing at which the measurement signal passed the second band-pass filter exceeds a second threshold, as the actual CI timing, and the third frequency and the fourth frequency are set within a range of 5.5 kHz to 8.0 kHz.

12. The control system of claim 1 ,
wherein the controller is further configured to execute:
a CI existence determining module to determine whether the unburnt mixture gas actually self-ignited based on the in-cylinder pressure parameter related to the pressure inside the combustion chamber measured by the sensor device, and
a CI probability calculating module to calculate a CI probability indicative of a probability that the self-ignition actually occurred when operating the engine, based on the determination result by the CI existence determining module, and

wherein the in-cylinder temperature determining module determines the in-cylinder temperature based on the CI probability when the actual CI timing is not able to be estimated.

13. A method of determining an in-cylinder temperature of a compression-ignition engine, the engine comprising a combustion

Assignees

• Mazda Motor

Inventors

• Maekawa Kota
• Nishimoto Kyotaro
• Tsumura Yuichiro
• Ujihara Kenko

Classifications

• Y02T10/40

  Engine management systems · CPC title

• F02D37/02 Primary

  one of the functions being ignition · CPC title

• F02D2200/0414

  Air temperature · CPC title

• F02D2200/08

  Exhaust gas treatment apparatus parameters · CPC title

• F02D2200/0602

  Fuel pressure · CPC title