Exhaust gas recirculation (EGR) system

Abstract

This invention relates to electronically controlled exhaust gas recirculation valves and more particularly to systems incorporating an electrical vacuum regulator.It is therefore an object of the present invention to provide an EGR system that is less susceptible to output flow changes caused by carbon build up. A further object of the invention is to provide a vacuum regulator that can be used with simple, low cost EGR valves. Simple valves can be used by virtue of the closed loop vacuum regulation feature of the present invention since the flow rate/vacuum signal relationship is not important. A further object of the present invention is to provide an EGR flow regulation system which automatically compensates for pressure variations which result in changes in the pressure differential across the EGR valve due to changes in exhaust system pressure and intake manifold pressure.Many other objects and purposes of the invention will be clear from the following detailed description of the drawing.

Description

Claims

1. In combination a vacuum actuated EGR pressure regulation system (10) comprising:

an EGR valve (12) adapted to control the EGR flow between the exhaust system and the intake manifold of an engine, the EGR valve (12) defining a controlled pressure chamber (42) between the exhaust system and intake manifold and pressure means for generating and for communicating a pressure difference signal indicative of the EGR flow rate, said pressure means including a first port (50) communicated to the controlled pressure chamber (42) and a second port (52) located downstream of said controlled pressure chamber communicated to said intake manifold, said first port and said second port generating a pressure difference signal indicative of the EGR flow;

electric vacuum regulator means (14) comprising: a housing (90) defining an atmospheric vent (92);

a coil (92) mounted in said housing and responsive to control signals, for generating a magnetic field in proportion to a desired EGR flow;

vent means (100, 102, 104, 106) for defining a valve seat (106) in communication with the controlled pressure chamber and a vacuum supply;

passage means (97, 99, 101, 103) for communicating said atmospheric vent (92) to said valve seat (106);

diaphragm means (130) supported within said hosing defining first and second chambers (114, 140) sealed relative to one another and movable in response to the force differential thereacross;

first means (110) for communicating the intake manifold pressure signal to one of said chambers;

second means (120) for communicating the controlled pressure signal to the other of said chambers;

pin means (154) attached to and movable with said diaphragm means (130) and mounted for engagement with said valve seat (106), said pin means responsive to the magnetic field generated upon energization of said coil (94);

bias means (144) interposing said housing (90) and said diaphragm (130) for biasing said diaphragm relative to said valve seat (106).

2. A system as defined in claim 1 wherein said EGR valve includes an orifice separating said controlled pressure chamber from said intake manifold and located between said first pot and said second port.

3. The system as defined in claim 2 wherein said vent tube means (100) is received within said housing (90) having a bore (102) therethrough, the bore terminating at a first end (102) external to said housing and at a second end (104), for defining a valve seat (106), said first end (102) communicated to the controlled pressure chamber (42) of said EGR and with a vacuum supply and wherein said passage means communicate said second end (104) to said atmospheric vent (92).

4. The system as defined in claims 1 or 3 wherein:

when said pin means (154) is seated upon said valve seat (106) full vacuum, as established by a vacuum source, is communicated to the EGR valve (12) and said pin means (154) is urged relative to said valve seat (106) in response to the pressure differential across said diaphragm (130) to communicate atmospheric pressure to said EGR valve (12) during instances when the EGR flow increases from the desired flow.

5. The system as defined in claim 4 wherein:

said vacuum source is a ported vacuum source.

6. A flow regulator (14) for use within an EGR system having an EGR valve (12) of the type which generates a pressure differential signal in response to EGR flow therethrough, the flow regulator (14) comprising:

a diaphragm (130) movable in response to the pressure differential signal;

housing means (90, 110, 120) for defining a cavity (114, 140) for supporting said diaphragm, said diaphragm dividing said cavity into a lower or first chamber (114) and an upper or second chamber (140), means for receiving the pressure differential signal including first port means (110,112) for communicating a first pressure to said first chamber (114) and second port means (120, 142) for communicating a second pressure signal to said second chamber (140), said housing means further including vent port means (96, 174) for communicating atmospheric pressure thereto;

vent tube means received within said housing and adapted to communicate said vent port means to the EGR valve, including a vent tube (100) having a central bore, terminating in one end (102) external to said housing and at another end (104) internal thereto, said another end (104) terminating at a valve seat (106);

passage means (97, 99, 101, 103) for communicating said vent port means with said another end (104);

coil means responsive to control signals for developing a magnetic field proportional to the desired EGR flow;

armature means (154, 160, 162, 164) movable with said diaphragm (130) in response to the pressure differential thereacross and to the magnetic field for seating upon said valve seat;

bias means (144) fitted within said either first chamber (114) or second chamber (140) for biasing said pin means relative to said valve seat.

7. The flow regulator as defined in claim 6 wherein said bias means (144) is lodged in said second chamber (140) for biasing said diaphragm towards said valve seat (106).