EGR Control system for internal combustion engine

Claim 2

An EGR (exhaust gas recirculation) control system for an internal combustion engine having means for defining an intake passageway and an exhaust passageway, comprising: means for defining an EGR passage connecting the exhaust passageway to the intake passageway to recirculate a portion of engine exhaust gases back to the engine; an orifice formed in said EGR passage to generate the pressure difference between the upstream and downstream sides thereof; a diaphragm-operated EGR control valve operatively disposed in said EGR passage to control the pressure in the EGR passage downstream of said orifice in accordance with an operating vacuum acting on the diaphragm of said EGR control valve, said operating vacuum being variable in accordance with engine operating conditions; regulating means for controlling said operating vacuum acting on the diaphragm of said EGR control valve in accordance with the pressure in the EGR passage downstream of said orifice, said regulating means includes a valve member secured to a first diaphragm which is biased with a preset load and receives the pressure in the EGR passage downstream of said orifice, said valve member being movable with the diaphragm of said regulating means and controlling the degree of said operating vacuum acting on the diaphragm of said EGR control valve in accordance with the relationship between said preset load and the pressure acting on the diaphragm of said regulating means; and changing means for substantially changing said preset load of the diaphragm of said regulating means in accordance with the engine operating conditions, said changing means including a second diaphragm connected to said diaphragm; a constant vacuum source whose vacuum is substantially constant regardless of the engine operating conditions; and vacuum control means for controlling the vacuum from said constant vacuum source in accordance with the engine operating conditions and applying said controlled vacuum to one side of said second diaphragm.

Claim 3

An EGR control system as claimed in claim 1, in which said EGR control valve includes a movable valve head seatable on a valve seat securely disposed in said EGR passage, the communication between the exhaust and intake passageways being blockable when said valve head is seated on the valve seat, said valve head being securely connected to the diaphragm which defines a first vacuum operating chamber communicable with a vacuum source generating said operating vacuum.

Claim 4

An EGR control system as claimed in claim 2, in which said regulating means includes an air induction pipe whose tip is open and closable with said valve member, said air induction pipe being communicable with the first vacuum operating chamber to supply air into the first vacuum operating chamber, a first spring for biasing said first diaphragm in the direction to cause said valve member to separate from the tip of said air induction pipe, a second spring for biasing said first diaphragm in the direction to cause said valve member to close the tip of said air induction pipe, said second spring being located in a pressure operating chamber which is at least partially defined by said first diaphragm and in communication with said EGR passageway downstream of said orifice.

Claim 5

An EGR control system as claimed in claim 3, in which said changing means includes a third spring for biasing said second diaphragm to compress said second spring in its axial direction, said second diaphragm defining a second vacuum operating chamber to which is applied said controlled vacuum, said second diaphragm being connected to said second spring to move said second spring with the movement of said second diaphragm.

Claim 6

An EGR control system as claimed in claim 4, in which said vacuum control means includes an air induction passage through which said second vacuum operating chamber is communicable with ambient air, valve means for controlling the amount of air inducted through said air induction passage into said second vacuum operating chamber of said spring moving means, and operating means for operating said valve means in accordance with the engine operating conditions.

Claim 7

An EGR control system as claimed in claim 5, in which said operating means includes sensing means for sensing the engine operating conditions, and a control circuit for controlling the operation of said valve means in accordance with the engine operating conditions sensed by said sensing means.

Claim 8

An EGR control system as claimed in claim 6, in which said regulating means further includes a first casing in which said first diaphragm is securely disposed to separate the interior of said casing into an atmospheric chamber communicable with ambient air and said pressure operating chamber, said first and second springs being located in said atmospheric chamber and said pressure operating chamber, respectively.

Claim 9

An EGR control system as claimed in claim 7, in which said changing means further includes a second casing secured to said first casing of said regulating means, a spring retainer for retaining thereon said second spring, said second spring retainer being movably disposed in said pressure operating chamber and mechanically connected to said second diaphragm through a rod which extends out of said first casing of said spring moving means.

Claim 10

An EGR control system as claimed in claim 6, further comprising a casing in which said first and second diaphragms are parallelly securely disposed, said first diaphragm defining an atmospheric chamber communicating with ambient air and said pressure operating chamber, said second diaphragm defining said second vacuum operating chamber, said first, second and third springs being disposed in said atmospheric chamber, said pressure operating chamber and said vacuum operating chamber, respectively.

Claim 11

An EGR (exhaust gas recirculation) control system for an internal combustion engine having means for defining an intake passageway and an exhaust passageway, comprising: means for defining an EGR passage connecting the exhaust passageway to the intake passageway to recirculate a portion of engine exhaust gases back to the engine; an orifice formed in said EGR passage to generate the pressure difference between the upstream and downstream sides thereof; a diaphragm-operated EGR control valve operatively disposed in said EGR passage to control the pressure in the EGR passage downstream of said orifice in accordance with an operating vacuum acting on the diaphragm of said EGR control valve, said operating vacuum being variable in accordance with engine operating conditions, said EGR control valve including a movable valve head seatable on a valve seat securely disposed in said EGR passage, the communication between the exhaust and intake passageways being blockable when said valve head is seatable on the valve seat, said valve head being securely connected to the diaphragm which defines a first vacuum operating chamber communicable with a vacuum source generating said operating vacuum; regulating means for controlling said operating vacuum action on the diaphragm of said EGR control valve in accordance with the pressure in the EGR passage downstream or said orifice, said regulating means including a valve member secured to a first diaphragm which is biased with a preset load and receives the pressure in the EGR passage downstream of said orifice, said valve member being movable with the diaphragm of said regulating means and controlling the degree of said operating vacuum acting on the diaphragm of said EGR control valve in accordance with the relationship between said preset load and the pressure acting on the diaphragm of said regulating means, said regulating means including an air induction pipe whose tip is open and closable with said valve member, said air induction pipe being communicable with the first vacuum operating chamber to supply air into the first vacuum operating chamber, a first spring for biasing said first diaphragm in the direction to cause said valve member to separate from the tip of said air induction pipe, a second spring for biasing said first diaphragm in the direction to cause said valve member to close the tip of said air induction pipe, said second spring being located in a pressure operating chamber which is defined at least partially by said first diaphragm and communicating with said EGR passageway downstream of said orifice; and changing means for substantially changing said preset load of the first diaphragm of said regulating means in accordance with the engine operating conditions, said changing means including a second diaphragm at least partially defining a second vacuum operating chamber which is controllably communicable with a constant vacuum source whose vacuum is substantially constant regardless of the engine operating conditions, said second diaphragm being connected to said second spring to move said second spring with the movement of said second diaphragm, a third spring for biasing said second diaphragm to compress said second spring in its axial direction, and vacuum control means for controlling the vacuum from the constant vacuum source in accordance with the engine operating conditions and applying said controlled vacuum to said second vacuum operating chamber.

Claim 12

An EGR (exhaust gas recirculation) control system for an internal combustion engine having means for defining an intake passageway and an exhaust passageway, comprising: means for defining an EGR passage connecting the exhaust passageway to the intake passageway to recirculate a portion of engine exhaust gases back to the engine; an orifice formed in said EGR passage to generate the pressure difference between the upstream and downstream sides thereof; a diaphragm-operated EGR control valve operatively disposed in said EGR passage to control the pressure in the EGR passage downstream of said orifice in accordance with an operating vacuum acting on the diaphragm of said EGR control valve, said operating vacuum being variable in accordance with engine operating conditions, said EGR control valve including a movable valve head seatable on a valve seat securely disposed in said EGR passage, the communication between the exhaust and intake passageways being blockable when said valve head is seatable on the valve seat, said valve head being securely connected to the diaphragm which defines a first vacuum operating chamber communicable with a vacuum source generating said operating vacuum; regulating means for controlling said operating vacuum action on the diaphragm of said EGR control valve in accordance with the pressure in the EGR passage downstream or said orifice, said regulating means including a valve member secured to a first diaphragm which is biased with a preset load and receives the pressure in the EGR passage downstream of said orifice, said valve member being movable with the diaphragm of said regulating means and controlling the degree of said operating vacuum acting on the diaphragm of said EGR control valve in accordance with the relationship between said preset load and the pressure acting on the diaphragm of said regulating means, said regulating means including an air induction pipe whose tip is open and closable with said valve member, said air induction pipe being communicable with the first vacuum operating chamber to supply air into the first vacuum operating chamber, a first spring for biasing said first diaphragm in the direction to cause said valve member to separate from the tip of said air induction pipe, a second spring for biasing said first diaphragm in the direction to cause said valve member to close the tip of said air induction pipe, said second spring being located in a pressure operating chamber which is defined at least partially by said first diaphragm and communicating with said EGR passageway downstream of said orifice; and changing means for substantially changing said preset load of the first diaphragm of said regulating means in accordance with the engine operating conditions, said changing means including a second diaphragm at least partially defining a second vacuum operating chamber which is controllably communicable with a constant vacuum source whose vacuum is substantially constant regardless of the engine operating conditions, said second diaphragm being connected to said second spring to move said second spring with the movement of said second diaphragm, a third spring for biasing said second diaphragm to compress said second spring in its axial direction, and vacuum control means for controlling the vacuum from the constant vacuum source in accordance with the engine operating conditions and applying said controlled vacuum to said second vacuum operating chamber.