Exhaust gas recirculation system

• US 6,205,785 B1
• Filed: 07/21/1999
• Issued: 03/27/2001
• Est. Priority Date: 07/21/1999
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Coleman, Gerald N.
• Primary Examiner(s): KOCZO JR, MICHAEL
• Application Number:
  US09/358,620
• Time in Patent Office: 615 Days
• Field of Search: 606/052
• US Class Current: 60/605.2
• CPC Class Codes: F01N 13/107 More than one exhaust manifold or exhaust collector
• CPC Class Codes: F02B 37/005 Exhaust driven pumps being combined with an exhaust driven auxiliary apparatus, e.g. a ventilator
• CPC Class Codes: F02B 37/24 by using pumps or turbines with adjustable guide vanes
• CPC Class Codes: F02D 21/08 the other gas being the exhaust gas of engine
• CPC Class Codes: F02M 26/05 High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• 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 26/27 with air-cooled heat exchangers
• CPC Class Codes: F02M 26/28 with liquid-cooled heat exchangers
• CPC Class Codes: F02M 26/34 with compressors, turbines or the like in the recirculation passage
• CPC Class Codes: F02M 26/38 with two or more EGR valves disposed in parallel
• CPC Class Codes: F02M 26/42 having two or more EGR passages; EGR systems specially adapted for engines having two or more cylinders
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A system and method for exhaust gas recirculation (EGR) in a heavy-duty diesel engine is disclosed. The disclosed EGR system comprises an EGR conduit, an EGR valve, an EGR cooler, and an EGR driver such as an auxiliary compressor driven by the exhaust gas driven turbine of the engine to forcibly drive the recirculated exhaust gas from the exhaust manifold via an EGR conduit to the intake manifold when the EGR valve is open. The disclosed EGR system also includes an EGR bypass conduit, the flow through which is governed by an electronically controlled EGR bypass valve. The EGR system also includes an ECM that controls the EGR bypass valve such that a flow of exhaust gas is directed through the EGR conduit and EGR driver during selected engine operating conditions where the primary EGR valve is open (i.e. EGR is on) and directs a flow of air from the intake through the EGR bypass conduit and EGR driver when EGR valve is closed (i.e. EGR is off). In addition, the ECM optionally controls the EGR bypass valve such that a flow of exhaust gas from the exhaust manifold is directed through the EGR bypass conduit to the intake manifold when the exhaust manifold pressure is greater than the intake manifold pressure.

Claims

1. An exhaust gas recirculation system for an internal combustion engine comprising:

an exhaust gas recirculation primary conduit fluidically coupling an exhaust manifold with an intake manifold;

an exhaust gas recirculation valve disposed along said exhaust gas recirculation primary conduit proximate said exhaust manifold;

an exhaust gas recirculation driver disposed along said exhaust gas recirculation conduit and adapted for forcibly driving said recirculated exhaust gas to said intake manifold;

an exhaust gas recirculation bypass conduit in fluidic communication with said exhaust gas recirculation primary conduit while circumventing said exhaust gas recirculation driver; and

an exhaust gas recirculation bypass valve disposed along said exhaust gas recirculation bypass conduit.

2. The exhaust gas recirculation system of claim 1 wherein said exhaust gas recirculation driver is a compressor driven by an exhaust gas driven turbine.

3. The exhaust gas recirculation system of claim 1 wherein said exhaust gas recirculation driver is a blower driven by a crankshaft of said engine.

4. The exhaust gas recirculation system of claim 1 further comprising an engine control module adapted to control flows through said exhaust gas recirculation system in response to various engine operating conditions;

and

wherein said exhaust gas recirculation bypass valve is an electronically controlled valve having a first position that allows flow through said exhaust gas recirculation bypass conduit and a second position that restricts flow through said exhaust gas recirculation bypass conduit.

5. The exhaust gas recirculation system of claim 4 wherein said exhaust gas recirculation bypass valve is oriented in said first position when said exhaust gas recirculation valve is shut.

6. The exhaust gas recirculation system of claim 4 wherein said exhaust gas recirculation bypass valve is oriented in said first position when the pressure in said exhaust manifold is greater than the pressure in said intake manifold.

7. The exhaust gas recirculation system of claim 1 wherein said exhaust gas recirculation bypass valve is a pressure relief valve that opens when the pressure in said exhaust manifold is greater than the pressure in said intake manifold.

8. In an exhaust gas recirculation system for an engine having an intake manifold, an exhaust manifold, an exhaust gas recirculation conduit, an exhaust gas recirculation cooler, an exhaust gas recirculation valve, and an exhaust gas recirculation driver, an improvement to said exhaust gas recirculation system comprising:

an exhaust gas recirculation bypass conduit in flow communication with said exhaust gas recirculation conduit at a first location upstream of said exhaust gas recirculation driver and a second location downstream of said exhaust gas recirculation driver; and

an exhaust gas recirculation bypass valve disposed along said exhaust gas recirculation bypass conduit for controlling flow through said exhaust gas recirculation bypass conduit.

9. The improvement of claim 8 wherein said exhaust gas recirculation driver is a compressor driven by an exhaust gas driven turbine.

10. The improvement of claim 8 wherein said exhaust gas recirculation driver is a blower driven by a crankshaft of said engine.

11. The improvement of claim 8 further comprising an engine control module adapted to control flows through said exhaust gas recirculation system in response to various engine operating conditions and wherein said exhaust gas recirculation bypass valve is an electronically controlled valve having a first position that allows flow through said exhaust gas recirculation bypass conduit and a second position that restricts flow through said exhaust gas recirculation bypass conduit.

12. The improvement of claim 11 wherein said exhaust gas recirculation bypass valve is oriented in said first position when said exhaust gas recirculation valve is shut.

13. The improvement of claim 11 wherein said exhaust gas recirculation bypass valve is oriented in said first position when the pressure in said exhaust manifold is greater than the pressure in said intake manifold.

14. The improvement of claim 8 wherein said exhaust gas recirculation bypass valve is pressure relief valve that is open when the pressure in said exhaust manifold is greater than the pressure in said intake manifold.

15. A method of controlling an exhaust gas recirculation system of an internal combustion engine having an intake manifold, an exhaust manifold, an exhaust gas recirculation conduit, an exhaust gas recirculation valve, and an exhaust gas recirculation driver, said method comprising the steps of:

directing a flow of exhaust gas through said exhaust gas recirculation conduit and said exhaust gas recirculation driver at a first set of engine operating conditions when said exhaust gas is recirculated from said exhaust manifold to said intake manifold; and

directing a bypass flow through an exhaust gas recirculation bypass conduit and said exhaust gas recirculation driver at a second set of engine operating conditions when said exhaust gas is not recirculating from said exhaust manifold to said intake manifold, said exhaust gas recirculation bypass conduit being disposed in flow communication with said exhaust gas recirculation conduit at a first location upstream of said exhaust gas recirculation driver and a second location downstream of said exhaust gas recirculation driver.

16. The method of claim 15 wherein said first set of engine operating conditions corresponds to engine operating conditions where said exhaust gas recirculation valve is open.

17. The method of claim 15 wherein said second set of engine operating conditions corresponds to engine operating conditions where said exhaust gas recirculation valve is closed.

18. The method of claim 15 further comprising the step of directing a flow of exhaust gas from said exhaust manifold through said exhaust gas recirculation bypass conduit to said intake manifold when said exhaust manifold pressure is greater than said intake manifold pressure.