WO2002038940A1

WO2002038940A1 - Hot/cold exhaust gas recirculation system

Info

Publication number: WO2002038940A1
Application number: PCT/US2001/031473
Authority: WO
Inventors: Craig Randall Markyvech; Paul L. Powell, Iii; Joseph A. Williamson
Original assignee: Detroit Diesel Corp
Current assignee: Detroit Diesel Corp
Priority date: 2000-11-10
Filing date: 2001-10-08
Publication date: 2002-05-16
Anticipated expiration: 2003-05-10
Also published as: AU2002211533A1

Abstract

The invention involves a system and method of controlling an internal combustion engine having an air intake system, an exhaust system (10) with an exhaust passage (58), and an exhaust gas recirculation (EGR) system (66). The EGR system has a cooled EGR passage (64a) extending from the exhaust passage and through a cooler to the intake system for cooled EGR flow and a hot EGR passage (64b) by-passing the cooler to the intake system for hot EGR flow. The method includes determining an operating condition of the internal combustion engine, regulating EGR flow to the intake system based on the condition of the internal combustion engine, and varying EGR flow temperature to the intake system based on the condition of the internal combustion engine.

Description

HOT/COLD EXHAUST GAS RECIRCULATION SYSTEM

TECHNICAL FIELD

The present invention relates generally to exhaust gas recirculation (EGR) systems.

BACKGROUND ART

In the control of heavy duty internal combustion engines, the conventional practice utilizes electronic control units having volatile and non-volatile memory, input and output driver circuitry, and a processor that executes instructions to control the engine and its various systems and sub-systems. A particular electronic control unit communicates with numerous valves, sensors, actuators, and other electronic control units to control various functions, which may include various aspects of transmission and engine control.

However, the heavy duty engine business is extremely competitive. Increased demands are being placed on engine manufacturers to design and build engines that provide better engine performance, improved reliability, and greater durability while meeting more stringent emission and noise requirements. One important object for internal combustion engine designers is to reduce NO_x emissions, while minimizing any negative impact on engine fuel economy and durability. An internal combustion engine having an exhaust gas recirculation (EGR) system reduces NO_x emissions while substantially maintaining fuel economy and durability. In many systems, for example, EGR is cooled to reduce NO_x emission levels at high engine loads. Systems in which EGR is not cooled may experience relatively high NO_x emissions during heavy engine throttle or loads. On the other hand, at low engine loads, systems in which EGR is cooled experience fuel droplets vaporization which is not enhanced. Large fuel droplets affect emission by producing soot. Due to increased demands, designers have been challenged to further improve the efficiency of engines having an EGR system. For the foregoing reasons, there is a need for an improved method and system for controlling an internal combustion engine including an exhaust gas recirculation (EGR) system with improved performance and more precise control than existing systems.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide an improved method of controlling a condition of an internal combustion engine having an air intake system, an exhaust system with an exhaust passage, and an exhaust gas recirculation (EGR) system having an EGR passage and a cooler. The EGR passage extends from the engine exhaust passage and through the cooler to the intake system for cooled EGR flow. The method includes providing a hot passage which extends from the EGR passage and by-passes the cooler to the intake system for hot EGR flow. The method further includes determining the condition of the internal combustion engine and regulating EGR flow to the intake system based on the condition of the internal combustion engine. The method further includes varying EGR flow temperature to the intake system based on the condition of the internal combustion engine.

It is another object of the present invention to provide an improved method of controlling temperature of EGR flow to an air intake system of an internal combustion engine, wherein the engine has an exhaust system with an exhaust passage and an exhaust gas recirculation (EGR) system. The EGR system has an EGR passage and a cooler. The EGR passage extends from the engine exhaust passage and through the cooler to the intake system for cooled EGR flow. The method comprises providing data representing temperature of EGR flow for predetermined engine loads and providing a hot passage extending from the EGR passage and by-passing the cooler to the intake system for hot EGR flow. The method further includes determining the engine load of the internal combustion engine and regulating EGR flow to the intake system based on the engine load. Furthermore, the method includes varying the temperature of EGR flow based on the engine load. It is another object of the present invention to provide an improved system for controlling a condition of an internal combustion engine having an air intake system, an exhaust system with an exhaust passage, and an exhaust gas recirculation (EGR) system connected to the exhaust system and having an EGR passage with a cooler. The EGR passage extends from the engine exhaust passage through the cooler and to the intake system for cooled EGR flow. The system includes a hot passage which is disposed in the EGR system and by-passes the cooler to the intake system. The system further includes at least one EGR regulating valve disposed in the EGR system to regulate EGR flow to the intake system based on the condition of the internal combustion engine.

It is yet another object of the present invention to provide an improved system for controlling a condition of an internal combustion engine including an air intake system and an exhaust system having an engine exhaust passage and an exhaust gas recirculation (EGR) passage with a cooler. The system generally includes a hot-cooled EGR valve, a cool passage, a hot passage, and an EGR metering valve. The hot-cooled EGR valve is mounted in the engine exhaust passage for controllably diverting a selected portion of the exhaust gas to the EGR passage for mixture with intake air. The hot-cooled valve is disposed in the EGR passage for regulating a percent mixture of hot and cooled EGR flow through the EGR passage. The hot-cooled valve is in fluid communication with the exhaust system. The cooled passage extends from the hot-cooled valve and through the cooler for cooled recirculated exhaust gas flow. The hot passage extends from the hot-cooled valve and by-passes the cooler for hot recirculated exhaust gas flow. Finally, the EGR metering valve receives the cooled and hot passages and regulates a mixture of cooled and hot EGR flow into the intake system.

It is yet still another object of the present invention to provide an improved system for controlling a condition of an internal combustion engine having an air intake system, an exhaust system with an exhaust passage, and an exhaust gas recirculation (EGR) system having an EGR passage and a cooler. The system includes a first mechanism for determining the condition of the internal combustion engine. The system further includes a second mechanism for regulating EGR flow to the intake system based on the condition of the internal combustion engine and a third mechanism for varying EGR flow temperature to the intake system based on the condition of the internal combustion engine.

A more complete appreciation of the invention and many of the attendant advantages thereof may be readily obtained by reference to the following detailed description when considered with the accompanying drawing figures, in which like reference characters indicate corresponding parts in all the views, wherein:

BRIEF DESCRIPTION OF DRAWINGS

FIGURE 1 is a schematic diagram of an internal combustion engine and engine control system made in accordance with an embodiment of the present invention; and

FIGURE 2 is a flow chart illustrating one method for controlling temperature of EGR flow to an air intake system of an internal combustion engine

BEST MODE FOR CARRYING OUT THE INVENTION

In accordance with the present invention, Figure 1 schematically illustrates an internal combustion engine including a recirculated exhaust gas flow system having control logic for controlling temperature of EGR flow to an air intake system of the engine. With reference to Figure 1, an internal combustion engine and associated control systems and subsystems are generally indicated at 10. System 10 includes an engine 12 having a plurality of cylinders (not shown), each fed by a fuel injector (not shown). In a preferred embodiment, engine 12 is a compression- ignition internal combustion engine, such as a heavy duty diesel engine. The injectors receive pressurized fuel from a fuel supply in a known manner. Various sensors are in electrical communication with a controller 22 via input ports 24. Controller 22 preferably includes a microprocessor 26 in communication with various computer readable storage media 28 via data and control bus 30. Computer readable storage media 28 may include any of a number of known devices which function as read only memory 32, random access memory 34, and non-volatile random access memory 36.

Computer readable storage media 28 have instructions stored therein that are executable by controller 22 to perform methods of controlling the internal combustion engine, including variable flow exhaust gas recirculation (EGR) valve 80 and variable geometry turbocharger 52. The program instructions direct controller 22 to control the various systems and subsystems of the vehicle, with the instructions being executed by microprocessor 26, and optionally, instructions may also be executed by any number of logic units 50. Input ports 24 receive signals from various sensors, and controller 22 generates signals at output ports 38 that are directed to the various vehicle components. A data, diagnostics, and programming interface 44 may also be selectively connected to controller 22 via a plug 46 to exchange various information therebetween. Interface 44 may be used to change values within the computer readable storage media 28, such as configuration settings, calibration variables, instructions for EGR and VGT control and others.

In operation, controller 22 receives signals from the various vehicle sensors and executes control logic embedded in hardware and/or software to control the engine. In a preferred embodiment, controller 22 is the DDEC controller available from Detroit Diesel Corporation of Detroit, Michigan. Various other features of this controller are described in detail in United States Patent Nos. 6,000,221; 5,477,827; and 5,445,128, the disclosures of which are hereby incorporated by reference.

As is appreciated by one of ordinary skill in the art, control logic may be implemented in hardware, firmware, software, or combinations thereof. Further, control logic may be executed by controller 22, in addition to being executed by any of the various systems and subsystems of the vehicle cooperating with controller 22. Further, although in a preferred embodiment, controller 22 includes microprocessor 26, any of a number of known programming and processing techniques or strategy may be used to control an engine in accordance with the present invention. Further, it is to be appreciated that the engine controller may receive information in a variety of ways. For example, engine systems information could be received over a data link, from a digital input or from a sensor input of the engine controller.

With continuing reference to Figure 1, controller 22 provides enhanced engine performance by controlling a variable flow exhaust gas recirculation valve 80 and by controlling a variable geometry turbocharger 52. Variable geometry turbocharger 52 includes a turbine 54 and a compressor 56. The pressure of the engine exhaust gasses causes the turbine to spin. The turbine drives the compressor, which is typically mounted on the same shaft. The spinning compressor creates turbo boost pressure which develops increased power during combustion.

A variable geometry turbocharger has moveable components in addition to the rotor group. These moveable components can change the turbocharger geometry by changing the area or areas in the turbine stage through which exhaust gasses from the engine flow, and/or changing the angle at which the exhaust gasses enter or leave the turbine. Depending upon the turbocharger geometry, the turbocharger supplies varying amounts of turbo boost pressure to the engine. The variable geometry turbocharger may be electronically controlled to vary the amount of turbo boost pressure based on various operating conditions. In a variable geometry turbocharger, the turbine housing is generally oversized for a particular engine, and the air flow is choked down to the desired level. There are several designs for the variable geometry turbocharger. In one design, a variable inlet nozzle has a cascade of moveable vanes which are pivotable to change the area and angle at which the air flow enters the turbine wheel. In another design, the turbocharger has a moveable side wall which varies the effective cross-sectional area of the turbine housing. It is appreciated that embodiments of the present invention are not limited to any particular structure for the variable geometry turbocharger. That is, the term VGT as used herein means any controllable air pressurizing device including the above examples, and including a modulated waste gate valve.

An exhaust gas recirculation system introduces a metered portion of the exhaust gasses into the intake manifold. The EGR system dilutes the incoming fuel charge and lowers combustion temperatures to reduce the level of oxides of nitrogen. However, as mentioned above, depending on the load placed on the engine, the temperature of the EGR may affect the efficiency of reducing NO_x emissions while substantially maintaining fuel economy and durability. Thus, with implementation of the system and method provided by the present invention, temperature of EGR flow may be varied in accordance with a condition of the engine. It has been found that the system and method of controlling EGR flow temperature based on engine load further reduces NO_x emissions while substantially maintaining fuel economy and durability of the engine. It should be noted that the condition may be any desired operating condition of the engine, but preferably engine load.

As shown in one embodiment of the present invention in Figure 1 , the amount of exhaust gas to be recirculated is controlled by EGR metering valve 80 and VGT 52. In accordance with the present invention, the EGR metering valve is a variable flow valve that is electronically controlled by controller 22. The geometry of the variable geometry turbocharger is also electronically controlled by controller 22. It is appreciated that there are many possible configurations for a controllable EGR metering valve, and embodiments of the present invention are not limited to any particular structure for the EGR metering valve. Further, it is appreciated that various sensors at the EGR metering valve may be disposed therein to detect temperature and/or differential pressure to allow the engine control to determine the mass flow rate through the valve. In addition, it is appreciated that various different sensor configurations may be utilized in various parts of the exhaust flow paths to allow controller 22 to determine the various mass flow rates throughout the exhaust system, including flow through the EGR system, flow through the compressor, and any other flows. In this embodiment, temperature of EGR flow is varied by hot-cooled EGR valve 66. Exhaust gas from exhaust line 58 enters the EGR system through hot-cooled EGR valve 66 in path or passage 64. As shown, exhaust gas exits hot- cooled EGR valve 66 through paths 64A and 64B. In path 64A, a cooler 68 is provided to cool the flow therethrough to reintroduce cooled EGR flow to engine 12 by EGR metering valve 80. Likewise, a cooler 62 is provided to cool the charge air coming from compressor 56. Path 64A through which EGR flow is cooled defines a cooled EGR passage for cooled EGR flow. In this embodiment, path 64B extends from hot-cooled EGR valve 66 and by-passes cooler 68. Path 64B through which EGR flow is not cooled defines a hot EGR passage for hot EGR flow. The EGR flow through the hot passage remains hot or uncooled EGR, and is eventually mixed with EGR flow of the cooled passage to attain the EGR flow temperature as desired. As shown, at a point downstream cooler 68, paths 64A and 64B are connected such that the EGR flow may be mixed and reintroducted at a desired temperature to engine 12 by EGR metering valve 80. However, it is appreciated that valve 66 may direct an entire EGR flow through either hot or cold passage only, if desired.

In accordance with the present invention, the EGR metering valve is a variable three-way valve that is electronically controlled by controller 22. In this embodiment, hot-cooled EGR valve 66 is controlled to move between a closed position (i.e., none of the exhaust gas is diverted for recirculation into the charge air), a single, factory-selected open position which diverts a portion of the gas for recirculation into the hot passage, a single, factory-selected open position which diverts a portion of the gas for recirculation into the cooled passage, and a selected open position which diverts predetermined portions of the gas for recirculation into the hot passage and the cooled passage. However, hot-cooled EGR valve 66 may be provided with a plurality of discrete controllable vane positions, or an infinitely positionable vane which may be controlled as described herein to vary the mix of recirculated exhaust gas into hot and cooled passages.

Figure 2 depicts one method for controlling temperature of EGR flow to an air intake system of an internal combustion engine. In accordance with the present invention, data representing temperature of EGR flow at predetermined engine loads of engine 12 is inputted into controller 22. Such data is typically expirically determined and stored in calibration tables in non- volatile memory, such as memory 36 (Fig. 1). The EGR temperature data is indexed by an engine condition or operating parameter, such as engine load, for example. Engine load may be represented as a ratio, fraction or percentage of full load. In one embodiment, however, it is to be noted that any other condition of the engine may be used to determine desired temperature of EGR flow. Moreover, it is appreciated that any other data may be inputted into controller 22 to be implemented in the present invention. Such implementations would not fall beyond the scope or spirit of the present invention.

During operation, controller 22 determines a condition of the internal combustion engine 12. Preferably, controller 22 determines operating load of engine 12. Engine load may be determined using any of a number of measured, sensed, calculated, or estimated parameters based on one or more engine sensors or actuators as well know by those of skill in the art. Time intervals at which controller 22 determines operating load of engine 12 are predetermined as desired, but preferably on the order of milliseconds based on the processing strategy and speed of controller 22. Based on the operating load of engine 12, controller 22 determines the EGR flow at which EGR metering valve 80 regulates EGR flow to the intake system. Also, based on the operating load of engine 12, temperature of EGR flow to the intake system is varied by hot-cooled EGR valve 66.

It is to be noted that other embodiments not shown may be implemented in practicing the present invention. For example, separate hot and cooled EGR valves may be used for separate hot and cooled passages. Moreover, separate metering valves may be used to control flow of separate passages. It is also to be noted that the location of each valve in the EGR system is not limited to the embodiment depicted in Figure 1. Disposing the valves implemented herein at other locations in the EGR system, e.g., upstream or downstream of the cooler, does not fall beyond the scope or spirit of this invention. Embodiments of the present invention include control logic that processes various inputs representing various engine conditions, and in turn, provides an EGR command signal and a VGT command signal. The EGR command signal commands a position for the variable flow EGR metering valve 80 to control gas flow through path 65, while the VGT command signal commands a geometry for VGT 52 to control gas flow through path 60.

It is appreciated that there are many possible configurations for a controllable hot-cooled EGR valve, and embodiments of the present invention are not limited to any particular structure for the hot-cooled EGR valve. Further, it is appreciated that various sensors at the hot-cooled EGR valve may be disposed therein to detect temperature and/or differential pressure to allow the engine control to determine the mass flow rate through the valve and through paths 64A and 64B. Hot-cooled EGR valve 66 is preferably but not necessarily controlled via an actuator, e.g. , a pneumatic actuator. The pneumatic actuator may be activated by a solenoid valve. The solenoid valve may be connected to outputs from the controller to receive suitable control signals to regulate pressure from a compressed air supply which pneumatically activates and deactivates the actuator to position the EGR metering valve, as desired.

In one embodiment, EGR metering valve 80 is controlled to move between a closed position (i.e., none of the exhaust gas is diverted for recirculation into the charge air), and a single, factory-selected open position which diverts a portion of the gas for recirculation. Alternatively, EGR metering valve 80 may be provided with a plurality of discrete controllable vane positions, or an infinitely positionable vane which may be controlled as described herein to vary the mix of recirculated exhaust gas and charge air. The remainder of the exhaust gas is supplied via line 58 to drive turbine 54 of VGT 52 as stated above. VGT 52 is typically also controlled by an actuator, such as a pneumatic actuator which, in one embodiment is activated by a PVH valve controlled by input signals from controller 22. A turbocharger speed sensor may be connected to VGT 56 to provide VGT speed information to controller 22. While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A method of controlling an internal combustion engine having an air intake system, an exhaust system with an exhaust passage, and an exhaust gas recirculation (EGR) system having a cooled EGR passage extending from the exhaust passage and through a cooler to the intake system for cooled EGR flow and a hot EGR passage by-passing the cooler to the intake system for hot EGR flow, the method comprising: dete-rmining an operating condition of the internal combustion engine; regulating EGR flow to the intake system based on the condition of the internal combustion engine; and varying EGR flow temperature to the intake system based on the condition of the internal combustion engine.

2. The method of claim 1 wherein the condition is engine load.

3. The method of claim 1 wherein the condition is engine coolant temperature.

4. The method of claim 1 wherein the regulated EGR flow includes one of hot or cooled EGR flows through the EGR system.

5. The method of claim 1 wherein the regulated EGR flow includes a mixture of hot and cooled EGR flow through the EGR system.

6. The method of claim 1 wherein varying the EGR flow temperature includes varying EGR flow in the hot EGR passage of the EGR system.

7. The method of claim 1 wherein varying the EGR flow temperature includes varying EGR flow in the cooled EGR passage.

8. A method of controlling temperature of exhaust gas recirculation (EGR) flow to an air intake system of an internal combustion engine having an exhaust system with an exhaust passage and an EGR system having a cooled EGR passage, a hot EGR passage and a cooler, the EGR passage extending from the exhaust passage and through the cooler to the intake system for cooled EGR flow, the hot passage extending from the EGR passage and by-passing the cooler to the intake system for hot EGR flow the method comprising: providing data representing temperature of EGR flow at predetermined engine loads of the engine; determining the engine load of the internal combustion engine; regulating EGR flow to the intake system based on the engine load; and varying at least one of the hot EGR flow and the cooled EGR flow based on the engine load to control the temperature of the EGR flow to the intake system.

9. The method of claim 8 wherein engine load is determined as a percentage of full load.

10. A system for controlling an internal combustion engine having an air intake system, an exhaust system with an exhaust passage, and an exhaust gas recirculation (EGR) system connected to the exhaust system and having a cooled EGR passage with a cooler, the cooled EGR passage extending from the engine exhaust passage through the cooler and to the intake system for cooled EGR flow, the system comprising: a hot passage disposed in the EGR system and by-passing the cooler to the intake system for hot EGR flow; and at least one three-way EGR valve disposed in the EGR system to regulate EGR flow to the intake system based on the condition of the internal combustion engine.

11. The system of claim 10 further comprising at least one EGR metering valve disposed in the EGR system upstream the cooler to vary the temperature of EGR flow based on the condition of the internal combustion engine.

12. A system for controlling an internal combustion engine including an air intake system and an exhaust system having an engine exhaust passage and an exhaust gas recirculation (EGR) passage with a cooler in the EGR passage, the system comprising: a hot-cooled valve disposed in the EGR passage for regulating a percent mixture of hot and cooled EGR flow through the EGR passage, the hot- cooled valve being in fluid communication with the engine exhaust passage to controllably divert a selected portion of the exhaust gas to the EGR passage for mixture with intake air; a cooled passage extending from the hot-cooled valve and through the cooler for cooled recirculated exhaust gas flow; a hot passage extending from the hot-cooled valve and by-passing the cooler for hot recirculated exhaust gas flow; and an EGR metering valve for regulating mixture of cooled and hot EGR flow into the intake system.

13. A system for controlling an internal combustion engine having an air intake system, an exhaust system with an exhaust passage, and an exhaust gas recirculation (EGR) system having an EGR passage and a cooler, the system comprising: a mechanism for dete-rmining the condition of the internal combustion engine; a mechanism for regulating EGR flow to the intake system based on the condition of the internal combustion engine; and a mechanism for varying EGR flow temperature to the intake system based on the condition of the internal combustion engine.