Control system for compression-ignition engine

• US 10,641,193 B2
• Filed: 11/13/2018
• Issued: 05/05/2020
• Est. Priority Date: 12/15/2017
• Status: Active Grant

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Sueoka, Masanari, Ohura, Takuya, Tokunaga, Tatsuhiro, Maruyama, Keiji, Nishida, Tomohiro
• Primary Examiner(s): Mo, Xiao En
• Application Number:
  US16/189,857
• Publication Number:
  US 20190186395A1
• Time in Patent Office: 539 Days
• CPC Class Codes: F02B 1/10 Methods of operating
• CPC Class Codes: F02B 1/14 Methods of operating
• CPC Class Codes: F02D 13/0261 Controlling the valve overlap
• CPC Class Codes: F02D 2041/0015 for engines with means for controlling swirl or tumble flow, e.g. by using swirl valves
• CPC Class Codes: F02D 2200/101 Engine speed
• CPC Class Codes: F02D 35/026 using an estimation
• CPC Class Codes: F02D 41/0057 Specific combustion modes combustion modes per se F02D41/3017
• CPC Class Codes: F02D 41/006 using internal EGR control of valve overlap for internal EGR F02D13/0261; arrangements for internal EGR F02M26/01
• CPC Class Codes: F02D 41/0062 Estimating, calculating or determining the internal EGR rate, amount or flow
• CPC Class Codes: F02D 41/0065 Specific aspects of external EGR control constructional details of EGR system F02M26/00
• CPC Class Codes: F02D 41/0077 Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position EGR valve position sensor F02M26/48
• CPC Class Codes: F02D 41/3041 with means for triggering compression ignition, e.g. spark plug
• CPC Class Codes: F02D 41/401 Controlling injection timing F02D41/402 takes precedence
• CPC Class Codes: F02M 26/33 controlling the temperature of the recirculated gases
• CPC Class Codes: F02P 5/1502 using one central computing unit
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A control system for a compression-ignition engine is provided, which includes an engine having a combustion chamber formed by a cylinder, a piston and a cylinder head, an injector, a spark plug, an exhaust gas recirculation (EGR) device configured to introduce into the combustion chamber a portion of burned gas generated inside the combustion chamber as EGR gas, an EGR controller configured to change an EGR ratio, the EGR controller changing the EGR ratio so that a compression start temperature of the combustion chamber rises as an engine load is reduced, and a controller connected to the injector and the spark plug to control them. The controller includes a processor configured to execute a combustion controlling module to output an instruction to the spark plug so as to ignite at an ignition timing after the EGR ratio adjustment so that partial compression-ignition combustion is performed.

Claims

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 exhaust gas recirculation (EGR) device including an EGR passage through which exhaust gas discharged to an exhaust passage from the combustion chamber recirculates into the combustion chamber, and an EGR valve provided to the EGR passage and configured to adjust an external EGR ratio that is a ratio of the exhaust gas recirculated into the combustion chamber through the EGR passage to total gas in the combustion chamber;

an EGR controller configured to adjust an internal EGR ratio that is a ratio of residual burned gas to the total gas in the combustion chamber, the EGR controller adjusting the internal EGR ratio so that a compression start temperature of the combustion chamber rises as an engine load is reduced; and

a controller connected to the injector and the spark plug, and configured to output a control instruction 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 internal 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 the combustion controlling module controls the EGR valve to increase the external EGR ratio as the engine load increases, within a first engine operating range where the partial compression-ignition combustion forms 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,

wherein within a second engine load range where the engine load is higher than the first engine 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-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 the stoichiometric air-fuel ratio, and

wherein the external EGR ratio in the second engine load range is larger than the external EGR ratio in the first engine load range.

2. The control system of claim 1, wherein the EGR controller is a variable valve mechanism configured to adjust the internal EGR ratio by changing open and close timings of at least one of an intake valve and an exhaust valve, and

wherein during the partial compression-ignition combustion, the combustion controlling module controls the variable valve mechanism to increase the internal EGR ratio as the engine load is reduced.

3. The control system of claim 2, wherein during the partial compression-ignition combustion, the combustion controlling module controls the variable valve mechanism to retard the close timing of the intake valve with respect to an intake bottom dead center as the engine load is reduced.

4. The control system of claim 3, wherein the variable valve mechanism adjusts an exhaust opened state extending period that is a period during which the exhaust valve opens after an exhaust top dead center, and

wherein during the partial compression-ignition combustion, the combustion controlling module controls the variable valve mechanism to extend the exhaust opened state extending period as the engine load is reduced.

5. The control system of claim 2, 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 controls the variable valve mechanism to increase the internal EGR ratio as the engine load is reduced, and performs the partial compression-ignition combustion.

6. The control system of claim 1, further comprising a swirl valve configured to generate a swirl flow inside the combustion chamber,

wherein at least in a low engine load segment of an engine operating range where the partial compression-ignition combustion is performed, the combustion controlling module controls the swirl valve to generate the swirl flow while controlling the injector to inject the fuel toward the swirl flow.

7. The control system of claim 6, wherein the injector at least has a first nozzle port and a second nozzle port disposed at a center portion of a ceiling surface of the combustion chamber and separated from each other in a circumferential direction of the injector, the first and second nozzle ports simultaneously injecting the fuel,

wherein the swirl flow is an inclined swirl flow flowing nonparallel to a plane perpendicular to a center axis of the combustion chamber, and

wherein the first and second nozzle ports are positioned and orientated so that a first fuel portion injected by the first nozzle port that has reached the swirl flow moves downstream along the swirl flow and then joins with a second fuel portion injected by the second nozzle port that has reached the swirl flow.

8. The control system of claim 1, wherein a geometric compression ratio of the engine is 14:

1 or higher and 18;

1 or lower.

9. The control system of claim 1, wherein during the partial compression-ignition combustion, the combustion controlling module adjusts a given control amount at least including a timing of the spark-ignition so that a spark ignition (SI) ratio that is a ratio of a heat generation amount by the spark-ignition combustion to a total heat generation amount matches a target SI ratio determined in advance for each operating condition of the engine.

10. A control system for a compression-ignition engine including an injector configured to supply fuel into a combustion chamber;

a spark plug configured to ignite a mixture gas containing fuel supplied from the injector and air; and

an exhaust gas recirculation device including an EGR passage through which exhaust gas discharged to an exhaust passage from the combustion chamber recirculates into the combustion chamber, and an EGR valve provided to the EGR passage and configured to adjust an external EGR ratio that is a ratio of the exhaust gas recirculated into the combustion chamber through the EGR passage to total gas in the combustion chamber, the engine performing partial compression-ignition combustion including SI combustion performed by combusting a portion of the mixture gas through spark-ignition by the spark plug, followed by compression ignition (CI) combustion performed by causing the remaining mixture gas to self-ignite, the control system comprising;

an EGR controller to adjust an internal EGR ratio that is a ratio of residual burned gas to the total gas in the combustion chamber; and

a processor configured to execute a combustion controlling module to, during the partial compression-ignition combustion, adjust the internal EGR ratio by using the EGR controller so that a compression start temperature of the combustion chamber rises as an engine load is reduced, and cause the spark plug to perform spark-ignition at a given ignition timing so that the SI combustion of the mixture gas is performed followed by the CI combustion,

wherein the combustion controlling module controls the EGR valve to increase the external EGR ratio as the engine load increases, within a first engine operating range where the partial compression-ignition combustion forms 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,

wherein within a second engine load range where the engine load is higher than the first engine 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-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 the stoichiometric air-fuel ratio, and

wherein the external EGR ratio in the second engine load range is larger than the external EGR ratio in the first engine load range.