Exhaust gas recirculation apparatus

An exhaust gas recirculation flow control apparatus is proposed for use in an exhaust gas recirculation system of an electronically controlled engine where flow from each of two exhaust manifold banks converges into a common area incorporating a port therein communicating to a passageway of an intake manifold with flow from each of the exhaust banks being balanced. The valve seat in the valve housing port and the valve body are tapered to provide a side seal of the valve body and the tapered seat as the valve is moved linearly into the port from the exhaust manifold side to isolate the banks from one another, as well as to control flow through the communication port under direction of an ECU.

BACKGROUND OF THE INVENTION 
The present invention relates to relates to internal combustion engines, 
particularly engines of the V-type having two banks of cylinders, and more 
particularly, to apparatus for controlling exhaust gas recirculation(EGR). 
More specifically, the apparatus of the present invention includes a 
three-way valve housing having a pair of exhaust inlets supplied 
respectively from first and second side banks converging in a common 
exhaust inlet port, an exhaust outlet to the intake manifold, and a 
tapered valve seat, a valve having a tapered head seating in the valve 
wherein the body of the valve extends across the common area and isolates 
the banks from one another, avoiding cross talk therebetween upon closure 
of the valve, the apparatus being operable by an ECU of the engine to 
produce a maximal instantaneous level of balanced recirculation without 
compromising optimal performance of the engine and without need of 
dedicated feedback for operability of the apparatus. 
THE PRIOR ART 
Heretofore, numerous embodiments of apparatus for controlling exhaust gas 
recirculation have been proposed. Of particular interest is U.S. Pat. No. 
4,969,445 which discloses a twin flow exhaust manifold arrangement wherein 
the common port between the exhaust inlet side and the intake manifold 
side is closed by a valve disk. The valve head extends into the exhaust 
manifold port to partially separate exhaust flow between the exhaust 
manifolds. The extended portion of the valve head is shown in the drawings 
to have taper-like surfaces, perhaps to facilitate smooth flow through the 
port. 
However, this twin flow exhaust arrangement does not provide a complete 
closure between the exhaust manifolds. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary object of the invention to provide an internal 
combustion engine having apparatus for controlling exhaust gas 
recirculation in a manner where optimal engine performance is not 
compromised, with the flow of exhaust gas entering an engine intake 
manifold from the exhaust manifolds of each of two banks of an engine, the 
exhaust manifolds of the banks being completely isolated from one another 
by the body of the control valve of the apparatus and with appropriate 
valve actuation under ECU control providing a maximal instantaneous level 
of recirculation without compromising optimal engine performance. 
This object, as well as others which may become more apparent hereinafter, 
is specifically met by the EGR control apparatus of the present invention 
for an internal combustion engine of the V-type having two banks of 
cylinders, each bank having a source of exhaust flow which engages a 
respective inlet port in a three-way valve housing having a common outlet 
connected to an intake manifold and a tapered valve seat, and a valve 
having a tapered body for engaging said tapered valve seat, the valve body 
extending across the exhaust side of the housing when closed to isolate 
the exhaust bank flow paths from each other while sealing the inlet port, 
and being retractable to allow opening of the port in response to signals 
generated by an ECU of the engine with the flow area increasing 
geometrically as the retraction increases.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings in greater detail, there is illustrated in 
FIG. 1 a schematically exemplary embodiment of a turbocharged internal 
combustion engine 16 having an exhaust gas recirculation system generally 
identified by the reference numeral 10. The engine 16 is of V-type 
configuration having left and right banks of cylinders 11, 13. 
Typically, pressurized air from a compressor 12 of a turbocharger 14 enters 
a common intake manifold 15 feeding into both banks of the engine 16 where 
air mixes with fuel which, when compressed by piston action, undergoes 
combustion, with chemical remnants of combustion, such as NOx, being 
carried away from the engine 16 via an exhaust manifold 22 of the engine 
16 disposed on each bank 11, 13, the exhaust manifolds 22 feeding first 
and second passages 18 and 20, respectively, connected to a turbine 24 of 
the turbocharger 14 which drivingly engages the compressor 12 thereof. 
To remove the NOx from the engine exhaust gas, such exhaust gas is 
preferably recirculated back through EGR valve 40 and passage 17 into the 
intake manifold 15, directly or indirectly, and is reburned, the 
instantaneous amount of exhaust gas capable of being accommodated for 
recirculation without compromising optimal engine 16 performance being 
dependent upon operational parameters of the engine 16 monitored by an ECU 
25 thereof. In this respect, if there is an excessive amount of exhaust 
gas being recirculated into the intake manifold 15, it will cause the 
engine 16 to operate at a level of performance which is less than optimal, 
as well as potentially causing damage thereto. 
Consequently, the amount of exhaust gas to be recirculated (level of 
recirculation) is controlled by the ECU 25 in response to sensed 
operational parameters of the engine 16 as compared to those required for 
optimal engine 16 performance. The ECU 25 analyzes readings received from 
various engine sensors, compares the readings to parameter values stored 
in a memory 26 thereof which are predetermined to produce optimal engine 
16 performance and causes necessary actions in various devices controlled 
thereby to maintain the engine 16 at an optimal level of performance. 
Specific sensors which could be used in establishing appropriate control 
of exhaust gas recirculation could be, as an example, one or more of an 
intake manifold temperature sensor 30, a mass air flow sensor 32, an 
engine speed sensor 34 and a pedal position sensor 36 
A tapered valve 50 incorporated into the exhaust gas recirculation control 
apparatus 40 disclosed herein has been designed to be operable under 
control of the ECU 25, in a predefined manner, in response to readings of 
parameters already being monitored by the ECU 25, instantaneously, without 
requiring a dedicated sensor or feedback circuit for appropriate 
activation thereof. 
Turning now to FIGS. 2 and 3, a valve housing 51 has a first exhaust inlet 
port 53 connected to the left bank exhaust passage 18 and a second exhaust 
inlet port 55 connected to the right bank exhaust passage 20 and an outlet 
passage 17 leading to the intake manifold 15. A port 54, having a tapered 
valve seat 57 narrowing toward the outlet passage 17, is disposed in a 
wall 56 between the adjacent common portion 58 of the exhaust inlet 
passage and the outlet passage 17. Thus, the port 54 extending through the 
common wall 56 communicates each of the exhaust passages 18 and 20 with 
the intake manifold passage 17. The body 64 of the valve 50 is configured 
in a trapezoidal shape as shown, with the tip 66 thereof being narrower 
than the port 54, so that at least a line-contact engagement between the 
valve body 64 and port 54, is created at a medial point on the tapered 
surface portion between the tip 66 and a base portion 67. When in the 
closed position, the valve body to extends across the entire extent of the 
common exhaust passage area 58, thereby isolating the exhaust passages 18 
and 20 from one another, while a tip 66 of the valve body 64 extends 
through port 54 into the intake manifold passage 17. 
Inasmuch as the valve body 64 must fill the cross sectional extent of the 
exhaust passage in common portion 58 to produce isolation of the banks 18 
and 20 from one another, a chamber 70 is provided on the opposite side of 
the exhaust passage 58 from the port 54 to allow for retraction of the 
valve body 64 to open the port 54, the chamber 70 extending outwardly of 
common area 58 to receive a base portion 72 of the valve body 64 which is 
tapered at a similar angle as the valve seat 57 to seal against the 
similarly-tapered side walls 80 of the chamber 70 when the valve 50 is in 
the closed position but does not interfere with sealing between the body 
64 and the port 54. An end wall 74 of the chamber 70 has a throughbore 76 
therein through which a stem 78 of the valve 50 extends so that, upon 
linear retraction of the stem 78, the valve body 64 can be drawn into the 
chamber 70, opening the port 54 and the exhaust passages 53, 55. It will 
be appreciated that when the valve is in the closed position, the force of 
the back pressure in the intake manifold passage and, to a small extent, 
the vertical component of the exhaust pressure force on the valve body act 
to assist in opening the valve. 
The linear motion of the valve stem 78 required for operation of the valve 
50 may be provided through use of any suitable actuator 80, such as, for 
example, a solenoid actuator or a pneumatic actuator 80. The actuator 80 
may provide a fully open or a fully closed position or preferably may 
accommodate degrees of linear retraction and extension. 
As described above, provides a number of advantages, some of which have 
been described above and others of which are inherent in the invention. 
Also, it will be apparent to those of skill in the art, upon reading the 
foregoing specification, that modifications can be proposed to the 
embodiment described without departing from the teachings herein. 
Accordingly, the scope of the invention should only be limited as 
necessitated by the accompanying claims.