METHOD AND DEVICE FOR CONTROLLING DIESEL ENGINE

• US 20120046854A1
• Filed: 08/10/2011
• Published: 02/23/2012
• Est. Priority Date: 08/20/2010
• Status: Active Grant

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Sangkyu, Kim, Shimo, Daisuke, Nishimoto, Kyotaro, Kakuda, Yoshie
• Granted Patent: US 8,770,174 B2
• Time in Patent Office: Days
• US Class Current: 701/108
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 2250/02 filtering and catalytic conversion
• CPC Class Codes: F02B 1/12 with compression ignition with fuel-air charge ignited by compression ignition of an additional fuel F02B7/00
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: F02B 37/013 with exhaust-driven pumps arranged in series
• CPC Class Codes: F02D 41/0057 Specific combustion modes combustion modes per se F02D41/3017
• CPC Class Codes: F02D 41/403 with pilot injections
• CPC Class Codes: F02M 26/08 for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor
• CPC Class Codes: F02M 26/10 having means to increase the pressure difference between the exhaust and intake system, e.g. venturis, variable geometry turbines, check valves using pressure pulsations or throttles in the air intake or exhaust system
• CPC Class Codes: F02M 26/24 with two or more coolers
• CPC Class Codes: F02M 26/25 with coolers having bypasses
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

This disclosure provides a method of controlling a diesel engine. The method includes adjusting an EGR ratio according to an engine load so that a cylinder O₂ concentration decreases gradually to a predetermined load with an increase in the load of the engine, while the O₂ concentration increases gradually above the predetermined load, operating the engine in a premix combustion mode where the fuel injection is terminated before a top dead center of a compression stroke in a low load operating range including the predetermined load where the O₂ concentration is lowest and, after that, the fuel ignites and combusts, and operating in a diffusion combustion mode where the fuel injection is executed in parallel to the ignition and combustion of the fuel in an operating range where the load is higher than that of the operating range in the premix combustion mode and the O₂ concentration is relatively high.

Claims

1. A diesel engine with control device, comprising:

an engine unit having a geometric compression ratio that is set to 15;

1 or less, and that is configured to cause compression self ignition of fuel supplied into a cylinder;

a fuel injection valve arranged facing to the inside of the cylinder and for directly injecting the fuel into the cylinder;

an injection control module for controlling an injection mode of the fuel into the cylinder through the fuel injection valve; and

an EGR ratio control system for adjusting an O₂ concentration within the cylinder by adjusting an EGR ratio associated with an adjustment of an EGR gas volume introduced into the cylinder;

wherein the EGR ratio control system adjusts the EGR ratio according to a load of the engine unit so that the O₂ concentration within the cylinder decreases gradually to a predetermined load with an increase in the load of the engine unit, while the O₂ concentration increases gradually above the predetermined load; and

wherein the injection control module sets to a premix combustion mode where a fuel injection is terminated before a top dead center of a compression stroke in an operating range of a low load including the predetermined load where the O₂ concentration within the cylinder is lowest and, after that, the fuel ignites and combusts, while the injection control module sets to a diffusion combustion mode where the fuel injection is executed in parallel to the ignition and combustion of the fuel in an operating range where the load is higher than that of the operating range in the premix combustion mode and the O₂ concentration within the cylinder is relatively high.

2. The diesel engine with control device of claim 1, wherein the EGR ratio control system changes the O₂ concentration within the cylinder by adjusting the EGR ratio through a control of a cooled EGR device for recirculating a low-temperature EGR gas to an intake passage of the engine unit.

3. The diesel engine with control device of claim 2, wherein the EGR ratio control system includes a high-pressure EGR system that branches from an exhaust passage of the engine unit, at a location upstream of a turbine of a turbocharger and recirculates the EGR gas to the intake passage of the engine unit, and a low-pressure EGR system that branches at a location downstream of the turbine and recirculates the EGR gas to the intake passage of the engine unit;

and

wherein the EGR ratio control system changes the O₂ concentration within the cylinder by adjusting the EGR ratio through a control of the low-pressure EGR system.

4. The diesel engine with control device of claim 3, wherein the injection control module executes in the diffusion combustion mode, a main injection for injecting the fuel to perform main combustion where diffusion combustion is mainly caused, and two or more pre-stage injections for injecting the fuel at a timing before the main injection to perform pre-stage combustion before the main combustion;

wherein the injection control module controls an injection mode of the pre-stage injection and an injection mode of the main injection so that a heat release rate due to the main combustion starts increasing after a heat release rate due to the pre-stage combustion reaches a peak and the heat release rate then begins to decrease; and

wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

5. The diesel engine with control device of claim 3, wherein the injection control module executes in the diffusion combustion mode a main injection for injecting the fuel to perform main combustion where diffusion combustion is mainly caused, and two or more pre-stage injections for injecting the fuel at timings before the main injection to perform pre-stage combustion before the main combustion;

wherein the injection control module controls an injection mode of the pre-stage injection and an injection mode of the main injection so that an ignition delay from a start of the main injection until a start of the main combustion becomes 0.1 to 0.3 msec by the pre-stage combustion increasing temperature and pressure within the cylinder; and

wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

6. The diesel engine with control device of claim 2, wherein the injection control module executes in the diffusion combustion mode, a main injection for injecting the fuel to perform main combustion where diffusion combustion is mainly caused, and two or more pre-stage injections for injecting the fuel at a timing before the main injection to perform pre-stage combustion before the main combustion;

wherein the injection control module controls an injection mode of the pre-stage injections and an injection mode of the main injection so that a heat release rate due to the main combustion starts increasing after a heat release rate due to the pre-stage combustion reaches a peak and the heat release rate then begins to decrease; and

wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

7. The diesel engine with control device of claim 2, wherein the injection control module executes in the diffusion combustion mode a main injection for injecting the fuel to perform main combustion where diffusion combustion is mainly caused, and two or more pre-stage injections for injecting the fuel at timings before the main injection to perform pre-stage combustion before the main combustion;

wherein the injection control module controls an injection mode of the pre-stage injection and an injection mode of the main injection so that an ignition delay from a start of the main injection until a start of the main combustion becomes 0.1 to 0.3 msec by the pre-stage combustion increasing temperature and pressure within the cylinder; and

wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

8. The diesel engine with control device of claim 1, wherein the injection control module executes in the diffusion combustion mode, a main injection for injecting the fuel to perform main combustion where diffusion combustion is mainly caused, and two or more pre-stage injections for injecting the fuel at a timing before the main injection to perform pre-stage combustion before the main combustion;

wherein the injection control module controls an injection mode of the pre-stage injections and an injection mode of the main injection so that a heat release rate due to the main combustion starts increasing after a heat release rate due to the pre-stage combustion reaches a peak and the heat release rate then begins to decrease; and

wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

9. The diesel engine with control device of claim 1, wherein the injection control module executes in the diffusion combustion mode a main injection for injecting the fuel to perform main combustion where diffusion combustion is mainly caused, and two or more pre-stage injections for injecting the fuel at timings before the main injection to perform pre-stage combustion before the main combustion;

wherein the injection control module controls an injection mode of the pre-stage injection and an injection mode of the main injection so that an ignition delay from a start of the main injection until a start of the main combustion becomes 0.1 to 0.3 msec by the pre-stage combustion increasing temperature and pressure within the cylinder; and

wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

10. A method of controlling a diesel engine, the engine having a geometric compression ratio set to 15:

1 or less and the engine causing compression self ignition of fuel supplied into a cylinder, the method comprising;

adjusting an EGR ratio according to a load of the diesel engine so that an O₂ concentration within the cylinder decreases gradually to a predetermined load with an increase in the load of the diesel engine, while the O₂ concentration increases gradually above the predetermined load;

operating the diesel engine in a premix combustion mode where a fuel injection is terminated before a top dead center of a compression stroke in an operating range of a low load including the predetermined load where the O₂ concentration within the cylinder is lowest and, after that, the fuel ignites and combusts; and

operating in a diffusion combustion mode where the fuel injection is executed in parallel to the ignition and combustion of the fuel in an operating range where the load is higher than that of the operating range in the premix combustion mode and the O₂ concentration within the cylinder is relatively high.

11. The method of claim 10, wherein the O₂ concentration within the cylinder is changed by recirculating a low-temperature EGR gas to an intake passage of the diesel engine.

12. The method of claim 11, wherein a main injection and a pre-stage injection are performed in the diffusion combustion mode so that main combustion where diffusion combustion is mainly caused and pre-stage combustion before the main combustion are performed;

and

wherein an injection mode of the pre-stage injection and an injection mode of the main injection are determined so that a heat release rate due to the main combustion starts increasing after a heat release rate due to the pre-stage combustion reaches a peak and the heat release rate then begins to decrease.

13. The method of claim 12, wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

14. The method of claim 11, wherein a main injection and a pre-stage injection are performed in the diffusion combustion mode so that main combustion where diffusion combustion is mainly caused and pre-stage combustion before the main combustion are performed;

wherein an injection mode of the pre-stage injection and an injection mode of the main injection are determined so that an ignition delay from a start of the main injection until a start of the main combustion becomes 0.1 to 0.3 msec by the pre-stage combustion increasing temperature and pressure within the cylinder; and

wherein the pre-stage injections are executed for a plurality of times during the compression stroke according to the determined injection mode and, after the pre-stage injection, the main injection is executed according to the determined injection mode.

15. The method of claim 14, wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

16. The method of claim 10, wherein a main injection and a pre-stage injection are performed in the diffusion combustion mode so that main combustion where diffusion combustion is mainly caused and pre-stage combustion before the main combustion are performed;

and

wherein an injection mode of the pre-stage injection and an injection mode of the main injection are determined so that a heat release rate due to the main combustion starts increasing after a heat release rate due to the pre-stage combustion reaches a peak and the heat release rate then begins to decrease.

17. The method of claim 16, wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.

18. The method of claim 10, wherein a main injection and a pre-stage injection are performed in the diffusion combustion mode so that main combustion where diffusion combustion is mainly caused and pre-stage combustion before the main combustion are performed;

wherein an injection mode of the pre-stage injection and an injection mode of the main injection are determined so that an ignition delay from a start of the main injection until a start of the main combustion becomes 0.1 to 0.3 msec by the pre-stage combustion increasing temperature and pressure within the cylinder; and

wherein the pre-stage injections are executed for a plurality of times during the compression stroke according to the determined injection mode and, after the pre-stage injection, the main injection is executed according to the determined injection mode.

19. The method of claim 18, wherein the pre-stage injection is executed at a timing where the fuel injected for every injection reaches in a cavity of a top of a piston fitted in the cylinder.