U.S. patent application number 11/439166 was filed with the patent office on 2006-12-21 for further improved reversing flow catalytic converter for internal combustion engines.
Invention is credited to Bernie Deschner, Edward A. Mirosh, Graham T. Reader, Ming Zheng.
Application Number | 20060283173 11/439166 |
Document ID | / |
Family ID | 37451435 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060283173 |
Kind Code |
A1 |
Zheng; Ming ; et
al. |
December 21, 2006 |
Further improved reversing flow catalytic converter for internal
combustion engines
Abstract
A further improved compact reversing flow catalytic converter
with protection from overheating includes an improved valve unit
which directs exhaust gases through a container filled with
catalytic material to permit a bypass of catalytic material when a
temperature of the material exceeds a predetermined threshold. The
container defines a U-shaped gas passage that communicates with two
chambers at the top of the container. The improved valve unit is
mounted to the top of the container and includes two container
chamber extension cavities, an improved intake cavity and an
improved exhaust cavity. The improved valve unit includes an
improved valve flapper and two conjoined valve walls each wall with
two openings therethrough. The improved valve flapper rotates
around normal central axis between a first, a second and third
positions. When overheating of the catalytic material is predicted,
a controller relinquishes control of the improved valve flapper and
an improved center return mechanism rotates the improved valve
flapper to a third position, in which each of the valve openings
communicates with both inlet and exhaust ports so that the exhaust
gas flow bypasses catalytic material. A fuel injection system under
control of the controller is used so that measured amounts of fuel
can be injected into the container reaction core to enhance
oxidation. The catalytic material is thus protected from damage due
to overheating. The advantage is a compact, reliable, highly
efficient further improved catalytic converter that is inexpensive
to manufacture, durable, and adapted for extended service life. The
improved valve may driven by a stepper motor that moves and holds
the valve to its three positions including bypass, forward and
reverse flow. An alternate version also replaces the oxidizing
flow-through monolith with an oxidizing filter trap.
Inventors: |
Zheng; Ming; (Windsor,
CA) ; Mirosh; Edward A.; (Calgary, CA) ;
Reader; Graham T.; (Lakeshore, CA) ; Deschner;
Bernie; (Calgary, CA) |
Correspondence
Address: |
GOWLING LAFLEUR HENDERSON LLP
SUITE 1400, 700 2ND ST. SW
CALGARY
AB
T2P 4V5
CA
|
Family ID: |
37451435 |
Appl. No.: |
11/439166 |
Filed: |
May 24, 2006 |
Current U.S.
Class: |
60/274 ;
60/288 |
Current CPC
Class: |
F01N 2410/00 20130101;
F01N 3/2093 20130101; F01N 3/24 20130101; F01N 2390/00 20130101;
Y02T 10/47 20130101; F01N 3/035 20130101; F01N 11/002 20130101;
F01N 1/084 20130101; F01N 3/2053 20130101; F01N 13/0097 20140603;
F01N 3/031 20130101; F01N 2470/22 20130101; Y02T 10/40 20130101;
F01N 2560/06 20130101; F01N 2410/08 20130101; F01N 2410/02
20130101 |
Class at
Publication: |
060/274 ;
060/288 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
May 24, 2005 |
CA |
2,508,159 |
Claims
1. A further improved reversing flow catalytic converter for
treating exhaust gases from an internal combustion engine
comprising: a container having a gas flow passage therein and a top
end having a first chamber and a second chamber that respectively
communicate with the gas flow passage; a catalytic material in the
gas flow passage adapted for contacting the exhaust gases that flow
through the gas flow passage; an improved valve for reversing an
exhaust gas flow through the gas flow passage, including an
improved valve housing with an improved intake cavity and an
improved exhaust cavity, mounted to the top end of the container
with extended cavities to container chambers one and two within the
improved valve, the improved intake cavity adapted for connection
to an exhaust gas pipe from said engine and the improved exhaust
cavity adapted for connection to a tail pipe for egress of said
exhaust gas from said converter; and an improved valve component
for reversing gas flow operably mounted to the improved valve
housing, adapted to be moved between a first position in which the
intake cavity communicates with the first container chamber through
its associated extended valve cavity and the exhaust cavity
communicates with the second container chamber through its
associated extended valve cavity, a second position in which the
intake cavity communicates with the second container chamber
through its associated extended valve cavity and the exhaust cavity
communicates with the first container chamber through its
associated extended valve cavity, and a third position which allows
the intake cavity to communicate with the exhaust cavity; and a
controller for controlling movement of the improved valve component
between the first and second positions during normal operating
temperatures for the catalytic converter and to the third to permit
bypass of some exhaust gas without passing through said catalyst
material during certain other temperatures for the further improved
catalytic converter.
2. A further improved reversing flow catalytic converter as claimed
in claim 1 wherein the improved valve housing comprises an enclosed
cavity with two ports in a bottom thereof and two conjoined walls
that divides the cavity into four compartments that respectively
form the intake cavity, the exhaust cavity, a valve extension
cavity to container chamber one and a valve extension cavity to
container chamber two.
3. A further improved reversing flow catalytic converter as claimed
in claim 2 wherein the improved valve component includes a flapper
that is symmetrical and rotatably mounted to the improved valve
housing by a shaft mounted at the openings in the center of the
improved valve bottom and top cover plates thereof and rotates
about a central axis that is normal to the flapper, the flapper
being constrained to rotating between the improved valve walls that
define the inlet and exhaust cavities, each wall having a first
opening and second opening therethrough which communicate
respectively with one of the container chambers and its associated
extended valve cavity in each of the first and second positions,
and one of the intake and exhaust cavities.
4. A further improved reversing flow catalytic converter as claimed
in claim 2 wherein each of the first and second openings in the
improved valve walls uncovered by the flapper in the third position
communicate with both the intake cavity and the exhaust cavity so
that the gas flow is not forced through the catalytic material in
the container.
5. A further improved reversing flow catalytic converter as claimed
in claim 4 wherein the flapper further comprises a drive shaft
driven by an actuator means.
6. A further improved reversing flow catalytic converter as claimed
in claim 5 wherein the actuator is activated by the controller to
rotate the flapper between the first and second positions, and said
third position.
7. A further improved reversing flow the catalytic converter as
claimed in claim 6 wherein the flapper returns to and is maintained
in the third position when the actuator is deactivated by the
controller.
8. A further improved reversing flow catalytic converter as claimed
in claim 2 wherein the gas flow passage is formed within an
interior chamber of the container, the interior chamber being
separated by a transverse plate that forms a first chamber and a
second chamber, the first and second chambers communicating with
each other, and each of the chambers communicating with the first
and second ports of the improved valve housing.
9. A further improved reversing flow catalytic converter as claimed
in claim 8 wherein the catalytic material is spaced below the first
and second ports of the improved valve housing to form an empty
chamber between the first and second ports and the catalytic
material, the empty chamber being divided by the transverse plate
into two separate compartments beneath the first and second ports
of the improved valve housing, respectively, the improved valve
housing of the improved valve being mounted to the top of the
container in an orientation so that the container transverse plate
is normal to the diametrical line that bisects the angle formed by
the two conjoined improved valve walls that form the inlet and
exhaust cavities within the improved valve housing.
10. A further improved reversing flow catalytic converter as
claimed in claim 9 wherein the improved valve flapper is positioned
between the transverse walls of the inlet and exhaust cavities, the
improved valve flapper being normal to both transverse walls, and
each of the two openings in each of the valve walls is smaller than
a half section of each of the first and second ports of the valve
bottom plate.
11. A further improved reversing flow catalytic converter as
claimed in claim 10 further comprising a mechanism for accurately
positioning the improved valve on the top of the container and
removeably securing same.
12. A further improved reversing flow catalytic converter as
claimed in claim 1 further comprising a sensor device for measuring
temperatures of the catalytic material.
13. A further improved reversing flow catalytic converter as
claimed in claim 7 further comprising an improved center return
mechanism associated with the drive shaft of the flapper to
maintain the flapper in the third position, and adapted to be
overridden by the actuator.
14. A further improved reversing flow catalytic converter as
claimed in claim 13 wherein the improved center return mechanism
comprises of a four-spring mechanism in which uneven spring forces
produce a torque adapted to rotate the drive shaft until the disk
is in the third position.
15. A safeguard system for a further improved reversing flow
catalytic converter to inhibit overheating of a catalytic material
used to treat the exhaust gases from an internal combustion engine,
the further improved reversing flow catalytic converter including:
a container having a gas flow passage therein and a top end having
a first chamber and a second chamber that respectively communicate
with the passage; a catalytic material in the gas flow passage
adapted to contact the exhaust gases which flow through the
passage; and an improved valve mechanism for reversing an exhaust
gas flow through the gas flow passage, including an improved valve
housing with an improved intake cavity, an improved exhaust cavity,
an extended valve cavity to chamber one of the container and an
extended valve cavity to chamber two of the container, mounted to
the top end of the container, the improved intake cavity adapted
for connection to an exhaust gas pipe of said engine and the
improved exhaust cavity being adapted for connection to a tail pipe
to permit egress of exhaust gases from said further improved
converter, the improved valve mechanism further including an
improved valve component for reversing gas flow operably mounted to
the improved valve housing, the improved valve component being
actuated by an actuator to move between a first position in which
the improved intake cavity communicates with the first chamber of
the container through its associated extended valve cavity and the
improved exhaust cavity communicates with the second chamber of the
container through its associated extended valve cavity, and a
second position in which the improved intake cavity communicates
with the second chamber of the container and its associated
extended valve cavity and the improved exhaust cavity communicates
with the first chamber of the container through its associated
extended valve cavity, the system comprising: at least one
temperature sensor for measuring a temperature of the catalytic
material in the container; and a controller for controlling
movement of the improved valve component between the first and
second positions.
16. A safeguard system as claimed in claim 15 which provides for
the movement of the improved valve component to a third position in
which the exhaust gas flow bypasses the catalytic material in the
container.
17. A safeguard system as claimed in claim 16 wherein the
controller is adapted to activate the actuator to rotate the
improved valve component for a normal reversing flow operation when
the temperature of the catalytic material is above a first
predetermined threshold.
18. A safeguard system is as claimed in claim 17 wherein the
controller is adapted to activate the actuator and resume normal
reversing flow operation when the temperature of the catalytic
material drops below a second predetermined threshold.
19. A safeguard system as claimed in claim 16 further comprising an
improved center return mechanism for moving the improved valve
component to and maintaining the improved valve component in the
third position when the controller deactivates the actuator.
20. A safeguard system as claimed in claim 19 wherein the
controller is adapted to deactivate the actuator to stop the normal
reversing flow operation and send a signal to an engine controller
to adjust the fuel supply to the engine when a rate of rise of the
temperature of the catalytic material is higher than a
predetermined threshold retrieved from a look-up table.
21. A safeguard system as claimed in claim 20 wherein the
controller is adapted to deactivate the actuator to stop normal
reversing flow operation and send a signal to an engine controller
to adjust the fuel supply to the internal combustion engine when
the temperature of the catalytic material exceeds a third
predetermined threshold.
22. A safeguard system as claimed in claim 21 further comprising an
auxiliary catalytic converter connected thereto for treating the
exhaust gases only when the exhaust gases bypass the further
improved reverse flow catalytic converter.
23. A method for preventing overheating of a catalytic material in
the further improved reversing flow catalytic converter which is
used for treating exhaust gas from an internal combustion engine
which further improved converter includes an improved valve for
controlling an exhaust gas flow through a catalytic material in the
container, the method comprising: monitoring a temperature of the
catalytic material; and controlling the exhaust gas flow to bypass
the catalytic material when the temperature of the catalytic
material is predicted to cause overheating of the catalytic
material.
24. A method as claimed in claim 23 further comprising a step of:
periodically measuring the temperatures of the catalytic material;
periodically calculating a rate of rise of the temperature of the
catalytic material using the temperatures measured; and controlling
the exhaust gas flow to bypass the catalytic material when the rate
of rise of the temperature of the catalytic material exceeds a
pre-determined threshold.
25. A method as claimed in claim 24 further comprising a step of:
adjusting engine operation to reduce oxidyzable components in the
exhaust gases when the rate of rise of the temperature of the
catalytic material exceeds the predetermined threshold
26. A method as claimed in claim 25 further comprising a step of:
adjusting engine operation to reduce total hydrocarbon and carbon
monoxide volume in the exhaust gases when the rate of rise of the
temperature of the catalytic material exceeds the predetermined
threshold.
27. A method as claimed in claim 24 wherein the predetermined
threshold of the rate of rise of the temperature is determined by
comparing a rate of temperature rise of the catalytic material and
an instant temperature of the catalytic material with corresponding
entries in a look-up table.
28. A method as claimed in claim 23 further comprising a step of:
adjusting engine operation to reduce total hydrocarbon and carbon
monoxide volume in the exhaust gases when the rate of rise of the
temperature of the catalytic material exceeds the predetermined
threshold.
29. A method as claimed in claim 23 further comprising a step of:
directing the exhaust gases through in an auxiliary catalytic
converter when the exhaust gases bypass the further improved
reverse flow catalytic converter.
30. A method as claimed in claim 23 further comprising a step of:
actuating and resuming normal control of the exhaust gas flow
through the catalytic material in the container when an instant
temperature of the catalytic material drops below the predetermined
threshold.
31. An improved valve structure for a further improved reversing
flow catalytic converter for exhaust gases, the further improved
converter having a container which has a top end with a first
chamber and a second chamber which are in fluid communication with
each other so that the exhaust gases introduced into one of the
first and second chambers flows through a catalytic material in the
container, comprising: an improved valve housing including an
improved intake cavity, an improved exhaust cavity, a valve cavity
extension to chamber one of the container and a valve cavity
extension to hamber two of the container, adapted to be mounted to
the top end of the container, the improved intake cavity adapted
for connection to an engine exhaust gas pipe of said engine and the
improved exhaust cavity being adapted for connection to a tail pipe
to permit egress of exhaust gases from said converter; an improved
valve component for reversing gas flow operably mounted in the
improved valve housing, adapted to be moved between a first
position in which the improved intake cavity communicates with the
first container chamber through its associated extended valve
cavity and the improved exhaust cavity communicates with the second
container chamber through its associated extended valve cavity and
a second position in which the improved intake cavity communicates
with the second container chamber through its associated extended
valve cavity and the improved exhaust cavity communicates with the
first container chamber through its associated extended valve
cavity.
32. An improved valve structure as claimed in claim 31 wherein the
improved valve housing includes two conjoined transverse walls that
divide the cavity into four compartments that respectively form the
improved intake cavity, the improved exhaust cavity, the extended
valve cavity to container chamber one and the extended valve cavity
to container chamber two.
33. A valve structure as claimed in claim 32 wherein the improved
valve component includes: an improved valve flapper which is
rotatably mounted to a bottom and a top plate of the valve housing,
and rotates about a central axis that is normal to the improved
valve flapper, the improved valve flapper rotating between the two
conjoined walls defining the inlet and exhaust cavities and each of
the two conjoined walls having a first opening and second opening
therethrough which communicate respectively with each of the
chambers of the container through their associated extended valve
cavities, and one of the intake cavity and exhaust cavity of the
valve housing.
34. An improved valve structure as claimed in claim 33 wherein the
first and second chambers of the container are substantially
semi-circular in plan view and the bottom plate openings of the
improved valve housing are also substantially semi-circular in
cross-section and oriented without offset with respect to the
container chambers. Each of the four openings in the four wall
sections of the two conjoined valve walls is positioned to
communicate with only one of the container chambers through their
associated extended valve cavities and one of the inlet or exhaust
cavities when the valve flapper is in one of the first and second
positions.
35. An improved valve structure as claimed in claim 34 wherein each
of the openings in the improved valve conjoined wall system is
adapted to communicate with both the intake port and the exhaust
port when the valve component is in the third position.
36. An improved valve structure as claimed in claim 35 wherein the
flapper further comprises a drive shaft affixed to the central
axis, extending axially through the improved valve housing with one
end projecting from the top of the improved valve housing.
37. An improved valve structure as claimed in claim 36 wherein the
improved valve housing further comprises a mechanism for accurately
positioning the valve housing on the top of the container and
removebly securing the same.
38. An improved valve structure as claimed in claim 37 wherein the
semi-circular shape of the extended valve container port cavities
and the semi-circular shape of the container chambers are
substantially similar, and each of the openings in the improved
valve conjoined walls is slightly smaller than half the area of the
semi-circular cross-section of the extended valve container ports
in the bottom plate of the valve.
39. An improved valve structure as claimed in claim 38 further
comprising a rotary actuator operablely associated with drive shaft
at the projecting end, the rotary actuator being adapted to
override the improved center return mechanism.
40. An improved valve structure as claimed in claim 39 wherein the
improved center return mechanism includes a four-spring system in
which uneven spring forces produce a torque adapted to rotate the
drive shaft until the flapper is in the third position.
41. An improved valve structure as claimed in claim 39 wherein the
improved valve component includes: an improved center return
mechanism associated with the improved valve component for moving
the improved valve component to and maintaining the improved valve
component in a third position in which exhaust gases are conveyed
from the intake cavity to the exhaust cavity without passing
through the catalytic material.
42. A further improved reversing flow catalytic converter
incorporating the safeguard system as claimed in one or more of
claims 15-30.
43. A further improved reversing flow catalytic converter
incorporating the improved valve structure as claimed in claims
31-37.
44. A further improved revering flow catalytic converter
incorporating the improved valve structure as claimed in claim 31,
said further improved converter having a container that has a top
end with a first chamber and a second chamber that are in fluid
communication with each other so that the exhaust gases introduced
into one of the first and second chambers flow through a catalytic
material in the container and pass out of the container through the
other second or first chamber, is substantially described.
45. A further improved reversing flow catalytic converter as
claimed in claim 1 wherein the catalytic material is optionally a
catalytic filter trap monolith
46. A further improved reversing flow catalytic converter as
claimed in claim 45 wherein a fuel injector is affixed to a fuel
manifold and diesel fuel is injected from the manifold into the
container flow redirection bowl and pulses fuel into the reactor
core for vaporization with time duration pulses provided from a
controller with an algorithm that is based on measuring monolith
static temperature and on calculating monolith rate of temperature
change and reacting to increase monolith temperature by the
addition of fuel when determined necessary as dictated by the
algorithm.
47. A further improved reversing flow catalytic converter as
claimed in claim 46 wherein the fuel injector is mounted on a
manifold and the manifold also contains a fuel strainer and flow
control orifice for restricting fuel flow and the manifold receives
a fuel supply from the low pressure fuel supply pump feeding the
diesel injector pump.
48. A further improved reversing flow catalytic converter as
claimed in claim 47 wherein the fuel injector is mounted on a
manifold along with a purge air supply solenoid and check valve
connected such that when the engine is shut down, a pulse of
vehicle air blows diesel fuel out of the injection line to prevent
caking.
49. A further improved reversing flow catalytic converter as
claimed in claim 45 wherein the catalytic material is optionally
replaced by a filter monolith without catalytic coating.
50. A further improved reversing flow catalytic converter as
claimed in claim 49 wherein a circular bottom plate is attached to
the valve bottom and has two semi circular and diametrically
opposed ports each subtended by an approximately 120 degree angle
of opening and the openings extend from near the bottom plate
center, to the inner radius of the bottom plate with the
orientation of the center line diameter bifurcating the center of
the two 120 degree ports being at right angles to the container
transverse wall such that each port communicates only with one side
of the container as divided by the container transverse plate.
51. A further improved reversing flow catalytic converter as
claimed in claim 50 wherein the improved valve structure is mounted
on the container in such a way that a diametrical line bifurcating
the two conjoined walls defining the inlet and exhaust cavities of
said improved valve structure is at normal angle, as guided by
positioning pins in the container flange, to the container
transverse wall.
52. A further improved catalytic converter as claimed in claim 50
wherein an improved valve flapper combined with four rectangular
openings in the four wall sections of the two conjoined valve walls
is provided, said walls separated at an approximately 60 degree
angle of opening from the center of the valve and extending from
the valve center to the valve outer wall in two diametrically
opposed directions such that the flapper covers two ports when in
either position one or position two and the valve port openings
optimally are sealed by the flapper with minimum leakage when in
cyclical operation and fully closed on either side.
53. A further improved reversing flow catalytic converter as
claimed in claim 52 wherein the improved valve flapper is adapted
to be rotated by a normal shaft that is connected at the flapper
along the shaft length, and at the top end coupled to an electric
stepper motor actuator that is attached to the improved valve
structure and that rotates the valve flapper, as directed by the
controller that activates the stepper motor actuator, to three
operating positions, namely a position to permit: forward flow
reverse flow bypass flow
54. A further improved reversing flow catalytic converter as
claimed in claim 53 wherein the stepper motor is a pneumatic
stepper motor.
55. A further improved reversing flow catalytic converter as
claimed in claim 54 wherein a controller provides power to move and
position the valve flapper in each of the operating positions based
on an algorithm embedded in the controller, the controller acting
upon temperature measurements sent to it from sensors embedded in
the filter monolith.
56. A safeguard system as claimed in claim 16 for the further
improved reversing flow catalytic converter wherein the controller
is adapted to move and position the improved valve flapper to a
bypass position and send a signal to an engine controller to adjust
the fuel supply to the internal combustion engine when a rate of
rise of the temperature of the filter monolith is higher than a
predetermined threshold retrieved from a look-up table embedded in
the controller.
57. A safeguard system as claimed in claim 56 for the further
improved reversing flow catalytic converter wherein the controller
is adapted to move and hold the valve flapper to a bypass position
and send a signal to an engine controller to adjust the fuel supply
to an internal combustion engine when the temperature of the filter
monolith exceeds a third predetermined threshold.
58. A safeguard system as claimed in claim 57 for the further
improved reversing flow catalytic converter further comprising an
auxiliary catalytic converter connected thereto for treating the
exhaust gases only when the exhaust gases bypass the further
improved reversing flow catalytic converter.
59. A safeguard system as claimed in claim 57 for the further
improved reversing flow catalytic converter wherein during an
overheating event said system will cause power to be blocked from
the fuel injector by an interlock between the controller and
injector valve.
60. An improved valve structure as claimed in claim 37 wherein the
semi-circular shape of the container cavities extends over a 180
degree angle and the semi-circular shape of the valve bottom plate
openings extends over a 120 degree angle, and each of the openings
in the valve walls is slightly smaller than half the area of the
semi-circular cross-section of each valve bottom plate port, the
openings in the walls being oriented at an angle of about 60
degrees with respect to each other, this being the flapper travel
zone.
Description
[0001] The present invention relates to catalytic converters for
internal combustion engines, and in particular, to a further
improved reversing flow catalytic converter over that disclosed in
U.S. patent application Ser. No. 11/218,608 filed Aug. 29, 2005 in
the name of some of the inventors herein for treating exhaust gases
from internal combustion engines.
BACKGROUND OF THE INVENTION
[0002] A problem relating to catalytic converters for internal
combustion engines, such as the prior art reversing flow catalytic
converter for internal combustion engines disclosed in U.S. Pat.
No. 6,148,613, is overheating Lean burn combustion systems for
fuel-efficient vehicles are particularly hard on exhaust
after-treatment systems because excessive oxygen is always present
in the exhaust. For example, the exhaust of diesel dual fuel (DDF)
engines, which is one type of diesel engine, normally contains more
than 5% volumetric oxygen after combustion. Under partial load the
surplus of oxygen in the exhaust may be higher than 10% by volume.
Under such circumstances, any engine management problems that
result in excessive fuel in the exhaust, will generally damage
exhaust after-treatment system due to overheating.
[0003] If a fuel management problem occurs, a large amount of the
excess fuel delivered to the engine can pass through it and into
the engine exhaust. That fuel will burn inside the catalyst if
sufficient oxygen is available and the catalyst has reached
catalytic temperature. For example, the complete burning of 2% of
methane in the exhaust, can raise the temperature of exhaust gases
by about 420.degree. C., in addition to the 600.degree. C.
temperature of the exhaust as it is ejected from the engine.
Consequently, the rate of temperature rise in the catalyst can
reach 20 to 30.degree. C./second, if the monoliths are metallic.
Besides the catalytic burning of methane, any combustible matter
such as soot accumulated on the catalyst surface, will also be
rapidly oxidized under such high temperatures. The burning of
accumulated soot will escalate and prolong the temperature rise.
The thermal wave oscillation produced by the reverse flow process
will also expedite the rise of the peak temperature of the catalyst
substrate. Once the catalyst temperature reaches 1200.degree. C., a
metallic substrate will begin to soften and subsequently lose
mechanical strength. Further temperature rise will cause collapse
of the substrate and eventual melt-down will occur when it is
heated to 1400-1450.degree. C. A detrimental uncontrolled
temperature rise can damage a catalyst in less than 20 seconds.
[0004] In the prior art, when a catalyst protection mode is
required for a gasoline engine, an extremely rich fuel/air mixture
is delivered to the engine. Since all oxygen is basically consumed
inside the engine during the over-rich combustion process, the
engine exhaust contains no oxygen. The large amount of excessive
fuel from the engine pulls down the catalyst temperature. In this
type of catalyst protection mode, however, the carbon monoxide
content of the exhaust gas is undesirably very high.
[0005] However, for lean burn systems such as diesel or dual fuel
engines, the excessive fuel will not cool down the catalyst
temperature because of the presence of a high concentration of
oxygen in the exhaust. Furthermore, lean burn systems cannot burn
stoichiometric fuel/air mixtures because of knocking restrictions.
For knock-free operation of a dual fuel engine, the original
compression ratio of the baseline diesel engine requires the
pre-mixed natural gas/air mixture to be generally leaner than
.lamda.=1.5.
[0006] As well, the concept of the reversing flow catalytic
converter has been found to offer nearly continuous oxidation of
exhaust components, mainly unburned hydrocarbons and carbon
monoxide, when used after natural gas or dual fuel engines, in a 13
mode test cycle. For this reason, such a catalytic converter will
likely not require supplementary heat added to the converter to
maintain oxidation temperature. However, for a diesel engine there
are fewer hydrocarbons and CO in the exhaust stream providing less
fuel in the emissions. Engine fuel will need to be added to the
exhaust stream during idle and low power operation of the engine in
order to maintain an oxidation temperature sufficient to convert CO
and hydrocarbons (including particulates), however, a considerably
lesser amount of fuel than would be required by a conventional
uni-directional oxidation catalyst. For this reason, addition of
fuel can also result in overheating of the catalyst, if too much
fuel is added.
[0007] U.S. Pat. No. 6,148,613 discloses a prior art reversing flow
catalytic converter for internal combustion engines. Such device 10
includes a valve housing 14 which reversibly directs exhaust gases
through a "U" shaped passage having a catalytic material therein. A
valve disk 42 having two openings 48 therein rotates around a
central axis, wherein in a first position of such rotatable valve
disk 42 the exhaust gases enter the exhaust cavity from an exhaust
pipe and pass through one of the openings in valve disk 42 into the
"U" shaped passage. In the second position of the rotatable valve
disk 42, the disk 42 and corresponding openings 48 therein are
rotated 90.degree. so that each opening 48 communicates with the
same cavity within the valve housing 14, but a different one of the
ports communicating with the U-shaped passage, so that gas flow
through the u-shaped passage is thereby able to be reversed.
[0008] Disadvantageously, prior art devices such as the type
disclosed in U.S. Pat. No. 6,148,613 lack a safeguard system to
protect such reversing flow catalytic converter from overheating,
as may arise under any one or more of the conditions explained
above.
[0009] Further, there exists a need for a continuously oxidizing
filter particulate trap for diesel engine exhausts.
[0010] An improved patent application Ser. No. 11/212,608 addresses
the above problems and disadvantages and presents solutions and
improvements.
[0011] The improved patent however, suffers from use of a rotating
compact valve that is prone to having a high degree of friction
drag due to its design and requirement for low leakage of exhaust
gas across the valve. For each percent of exhaust gas leakage
across the valve, the effectiveness of the destruction of exhaust
methane or exhaust particulates diminishes by about one percentage
point. Leakage and drag at the valve are reduced in this new
invention by a re-configuration of the valve rotor and stator ports
from being rotated as a sliding assembly perpendicular to and
rotated about a shaft, to the rotor now being a symmetrical flapper
and four stator ports now being fixed in the two conjoined inner
valve walls parallel to the shaft intersecting each other at the
center of the valve at the shaft area, and the rotor flapper being
rotated about the shaft between two stator walls with four ports.
The improved valve is divided into four cavities separated from
each other by the internal valve walls The valve cavities extending
from container chambers one and two and constrained between valve
bottom ports one and two, the two valve inner walls, the outer wall
and the cover plate are now better described as extended cavities
to chambers one and two of the container. The valve cavities
extending from the inlet and outlet piping ports and constrained by
the valve top and bottom covers and between two valve walls are now
better called inlet and outlet cavities through which the flapper
moves to redirect flow as directed by the controller, actuator,
spring return and rotor The rotor is now better described as a
symmetrical flapper without ports and the stator is now better
described as two pairs of conjoined walls intersecting at the
center of the valve housing, each wall section having a valve port
which the flapper covers two at a time while leaving the other two
completely uncovered on a cyclic basis This type of valve action
occurs with very little drag even at operating temperature, and the
flapper is able to cover valve ports effectively and in this manner
improve exhaust component destruction efficiency. The valve action
of the flapper alternately covering two ports and uncovering the
other two ports on a cyclic basis, is controlled by a temperature
control system and has the effect of reversing the flow of exhaust
gas cyclically flowing through the monolith in the container.
[0012] The improved patent application also suffers from a
neutralizing spring return design with two compressed springs such
that the spring return is not force-balanced at the shaft and
therefore prone to shaft wear. Therefore an improvement is made to
create a force-balanced spring return with the use of four
compressed springs mounted in such a way as to balance out forces
on the shaft that were prevalent with the original two spring
design.
[0013] The improved patent application used diesel injection as
required into the inlet pipe taking exhaust gases from the diesel
engine into the valve and oxidation or filter monolith and also
mentioned that injection of diesel was alternately possible into
the space at the central core of the monolith. It is preferred to
add diesel fuel within the central core since the heat in this area
is prevalently greater than in the inlet to the monolith, giving
greater opportunity for complete diesel vaporization within the
core thereby effecting a greater oxidation efficiency of the added
fuel.
SUMMARY OF THE INVENTION
[0014] It is accordingly an object of the present invention to
provide a further improved reversing flow catalytic converter
system for treating exhaust gases from an internal combustion
engine, which system includes an improved compact valve structure
incorporated in the converter as well as an improved safeguard
system to protect the catalyst and converter from overheating and
including an improved method for monolith heat addition by diesel
injection into the central core of the monolith.
[0015] Another object of the present invention is to provide a
further improved reversing flow catalytic converter system for
treating exhaust gases from an internal combustion engine which has
a compact structure for efficient performance, minimal heat loss,
and mechanical simplicity.
[0016] Yet another object of the present invention is to provide an
improved three-way valve for a further improved reversing flow
catalytic converter which overcomes the shortcomings of the prior
art discussed above.
[0017] A further object of the present invention is to provide a
further improved reversing flow catalytic converter having an
improved bypass system to protect the further improved reversing
flow catalytic converter from overheating.
[0018] A still further object of the present invention is to
provide an improved three-way valve for a further improved
reversing flow catalytic converter that is maintained in a neutral
position to permit exhaust gases to bypass the further improved
catalytic converter when the improved valve is not actuated.
[0019] A further object of the present invention is to optionally
provide a further improved reversing flow catalytic converter with
an oxidizing filter trap that may or may not be coated with
catalytic material, to trap, hold and oxidize particulates, in
place of the oxidation catalytic substrate within the further
improved reversing flow catalytic converter.
[0020] A further object of the present invention is to provide a
further improved reversing flow catalytic converter with an
improved means of injecting a controlled amount of diesel engine
fuel within the core of the further improved reversing flow
catalytic converter, when required to maintain a continuous
oxidation temperature. The catalytic converter monolith may or may
not be coated with catalytic material, depending on the application
and upon the amount of fuel normally present in the exhaust stream
and additionally injected into the middle of the further improved
reversing flow catalytic converter.
[0021] A still further object of the present invention is the
provision of an improved force-balanced spring return design
component such that the improved valve can be reliably and quickly
returned to a neutral or bypass position upon detection of damaging
impending temperatures within the monolith of the further improved
reversing flow catalytic converter.
[0022] Accordingly, in one broad aspect of the invention, a further
improved reversing flow catalytic converter for treating exhaust
gases from an internal combustion engine is provided, comprising:
[0023] a container having a gas flow passage therein and a top end
having a first chamber and a second chamber that respectively
communicate with the gas flow passage; [0024] a catalytic material
in the gas flow passage adapted for contacting the exhaust gases
that flow through the gas flow passage; [0025] an improved valve
for reversing an exhaust gas flow through the gas flow passage,
including an improved valve housing with two extended valve
cavities connecting to chambers one and two of the container and
mounted to the top end of the container, an improved intake cavity
and an improved exhaust cavity, the improved intake cavity adapted
for connection to an exhaust gas pipe from said engine and the
improved exhaust cavity adapted for connection to a tail pipe for
egress of said exhaust gas from said converter; and [0026] an
improved valve component for reversing gas flow operably mounted to
the improved valve housing, adapted to move between a first
position in which the intake cavity communicates with the first
valve opening and container chamber and the exhaust cavity
communicates with the second valve opening and container chamber, a
second position in which the intake cavity communicates with the
second valve opening and container chamber and the exhaust cavity
communicates with the first valve opening and container chamber,
and a third position which allows the intake cavity to communicate
with the exhaust cavity; and [0027] a controller for controlling
movement of the improved valve component between the first and
second positions during normal operating temperatures for the
further improved reversing flow catalytic converter and otherwise
permitting movement of the improved valve component to the third
position for abnormal operating temperatures.
[0028] Alternatively, in another aspect of such first aspect, the
present invention comprises a further improved reversing flow
catalytic converter for treating exhaust gases from an internal
combustion engine is provided, comprising: [0029] a container
having a gas flow passage therein and a top end having a first
chamber and a second chamber that respectively communicate with the
gas flow passage; [0030] a catalytic material in the gas flow
passage adapted for contacting the exhaust gases that flow through
the gas flow passage; [0031] an improved valve for reversing an
exhaust gas flow through the gas flow passage, including an
improved valve housing with a bottom plate mounted to the top end
of the container and containing two openings, one connecting to
each of the first and second container chambers, and extended valve
cavities within the valve connecting the container chambers to an
improved intake cavity and an improved exhaust cavity, separated
from the container chambers and associated extended valve cavity by
two conjoined walls intersecting at the center of the valve
housing, each wall section having an opening that allows
communication between the container first and second chambers and
connected extended valve cavities and the intake and exhaust
cavities when the valve flapper is positioned to allow such
communication. The improved intake cavity is adapted for connection
to an exhaust gas pipe from said engine and the improved exhaust
cavity is adapted for connection to a tail pipe for egress of said
exhaust gas from said converter; and [0032] an improved valve
component for reversing gas flow operably mounted to the improved
valve housing, adapted to the be moved between a first position in
which the improved intake cavity communicates with the first
chamber of the container through the first extended valve cavity
and the improved exhaust cavity communicates with the second
chamber of the container through the second extended valve cavity,
a second position in which the improved intake cavity communicates
with the second chamber of the container through the second
extended valve cavity and the improved exhaust cavity communicates
with the first chamber of the container through the first extended
exhaust cavity, and a third position which allows the improved
intake cavity to communicate with the improved exhaust cavity; and
[0033] a controller for controlling movement of the improved valve
component between the first and second positions during normal
operating temperatures for the further improved reversing flow
catalytic converter and to the third position to permit bypass of
exhaust gas without passing through said catalyst material during
certain other temperatures for the further improved reversing flow
catalytic converter.
[0034] Preferably, the improved valve housing has an interior
cavity with two openings in the bottom plate and two transverse
walls that divide the cavity into four parts, two parts that, with
the outer wall and cover plate, respectively form cavity extensions
of the container chambers one and two, and the other two parts that
respectively connect to the engine exhaust valve inlet pipe and the
engine tailpipe outlet pipe The improved valve component may
include a flapper plate which is symmetrical and rotatably mounted
to the center of the valve housing at the shaft, and rotates about
a central axis that is perpendicular to the improved valve cover
plate and the two openings therein that communicate with one of the
inlet and exhaust cavities. The improved valve bottom plate has a
first opening and second opening therethrough which communicate
respectively with each of the two container chambers.
[0035] More preferably, the gas flow passage is formed within an
interior chamber of the container, the interior chamber being
separated by a transverse plate into two parts which respectively
form a first chamber section and a second chamber section. The two
sections communicate with each other, and each of the chamber
sections communicates with one of the first and second valve
openings. The container further comprises a gas permeable material
which contains the catalytic material. The gas permeable material
preferably comprises a plurality of monoliths having a plurality of
cells extending therethrough, the monoliths being coated with a
catalytic material.
[0036] According to a second aspect of the present invention, there
is provided a further improved reversing flow catalytic converter
for exhaust gases, the converter comprising a container which has a
top end with a first chamber and a second chamber that are in fluid
communication with each other so that the exhaust gases introduced
into one of the first and second chambers flow through a catalytic
material in the container. The improved valve structure comprises
an improved valve housing including two openings in the bottom
plate of the improved valve housing, opening one that connects to
the first chamber of the container and opening two that connects to
the second chamber of the container and two extended valve
cavities, one connected to container chamber one through improved
valve opening one and the other connected to chamber two through
improved valve opening two, and an improved intake cavity and an
improved exhaust cavity. The improved intake and exhaust cavities
are separated from the container first and second chambers and
their associated extended valve cavities by two conjoined walls
that intersect at the center of the improved valve housing, each
wall making two wall sections and each section containing one
opening such that two of the four openings are blocked by the
flapper alternately as dictated by the controller. The improved
intake cavity is adapted for connection of an exhaust gas pipe and
the improved exhaust cavity is adapted for connection of a tail
pipe. An improved valve component is provided for reversing gas
flow operably mounted in the valve housing. The improved valve is
adapted to move the flapper between a first position in which the
improved intake cavity communicates with the first container
chamber through its associated extended valve cavity and the
improved exhaust cavity communicates with the second container
chamber through its associated extended valve cavity, and a second
position in which the improved intake cavity communicates with the
second container chamber through its associated extended valve
cavity and the improved exhaust cavity communicates with the first
container chamber through its associated extended valve cavity. The
improved valve structure further includes an improved center return
mechanism associated with the improved valve component for moving
the improved valve component to a third position in which the
improved intake cavity communicates with the improved exhaust
cavity through the improved valve component when the improved valve
component is not actuated to move to one of the first and second
positions. Alternatively, the third position may be achieved by
positive action of a controller and actuator.
[0037] According to a third aspect of the present invention, there
is provided a further improved reversing flow catalytic converter
for treating exhaust gases from an internal combustion engine. The
catalytic converter includes a container having a gas flow passage
therein and a top end having a first chamber and a second chamber
which respectively communicate with the passage. A catalytic
material is provided in the gas flow passage and contacts the
exhaust gases which flow through the passage. The further improved
catalytic converter has an improved valve for reversing the exhaust
gas flow through the gas flow passage, including an improved valve
housing with an improved intake cavity and an improved exhaust
cavity, and two extended valve cavities mounted to the top end of
the container. The improved intake cavity is adapted for connection
of an exhaust gas pipe and the improved exhaust cavity is adapted
for connection of a tail pipe. The improved valve also includes an
improved valve component for reversing gas flow, operably mounted
in the improved valve housing, and adapted to be moved between the
first, second, and third positions.. In the first position, the
improved intake cavity communicates with the first container
chamber through its associated extended valve cavity and the
improved exhaust cavity communicates with the second container
chamber through its associated extended valve cavity In the second
position, the improved intake cavity communicates with the second
container chamber through its associated extended valve cavity and
the improved exhaust cavity communicates with the first container
chamber through its associated extended valve cavity. In the third
position, the improved intake cavity communicates with the improved
exhaust cavity. A controller controls movement of the improved
valve component between the first and second positions, and
movement of the improved valve component to the third position, if
required to protect the catalytic material from overheating.
[0038] According to a fourth aspect of the present invention, a
safeguard system is provided to inhibit overheating the further
improved reversing flow catalytic converter. In addition to
controlling the improved valve component for reversing flow bypass
operation, the controller is also adapted to indirectly control
fuel supply to the engine, in order to protect the catalytic
material from overheating.
[0039] According to fifth aspect of the invention, there is
provided a method for preventing overheating of the further
improved reversing flow catalytic converter. The further improved
reversing flow catalytic converter includes an improved valve
adapted for connection of an exhaust gas pipe and a tail pipe, and
associated with first and second ports of a container and their
respective associated extended valve cavities for reversing exhaust
gas flow through a catalytic material in the container. The method
comprises steps of monitoring temperatures of the catalytic
material, and controlling an improved valve mechanism to permit the
exhaust gases to flow from the exhaust gas pipe to the tail pipe
without passing through the catalytic material when the temperature
of the catalytic converter exceeds a predetermined threshold. The
method also preferably includes steps of calculating the rate of
temperature rise in the catalytic material, and controlling the
improved valve mechanism to permit the exhaust gases to flow from
the exhaust gas pipe to the tail pipe without passing through the
catalytic material when the rate of temperature rise exceeds a
predetermined threshold. A further optional step adjusts engine
operation to reduce total hydrocarbon and carbon monoxide volume in
the exhaust gas flow.
[0040] The safeguard system in accordance with the present
invention, protects the catalytic material from overheating when an
abnormal rate of temperature rise is detected. The bypass of
exhaust gases around the catalyst is the primary safeguard
mechanism. During bypass, the exhaust gases do not flow through the
monoliths in the catalytic converter. Thus, the inner catalyst is
shielded from the flow of the fuel-oxygen mixture contained in the
engine exhaust. Extensive testing has shown that once the exhaust
flow to the catalyst is stopped by the improved bypass mechanism,
the catalyst center temperature comes down quickly even if the
exhaust gases are rich in both fuel and oxygen. However, if
overheating occurs, the engine fuel supply is preferably adjusted
to reduce the total hydrocarbon and carbon monoxide volume in the
exhaust, as well as the temperature of the exhaust gases. In bypass
mode, exhaust gases rich in fuel and oxygen will burn in the
improved valve housing if the temperature of the improved valve
housing is high enough The high temperature resulting from the
burning of the fuel in the improved valve housing retards cooling
of the catalyst, and may damage the improved valve structure.
Therefore, control of the fuel supply is preferable when
overheating occurs. Besides, in the bypass mode, the exhaust gases
are not treated by the catalyst and therefore, the concentrations
of hydrocarbons and carbon monoxide in the exhaust gas generally
increases.
[0041] According to a sixth aspect of the invention, there is
provided an option to replace the oxidation catalyst within the
further improved reversing flow catalytic converter with a
catalytic filter trap. In this variation of the reversing flow
catalytic converter, a method is provided to entrap particulates
and to hold them for a period of time to allow effective oxidation
of the particulate matter when the trap is held at a continuous
oxidation temperature by the temperature monitoring and control
system. In this sixth aspect and as a second option, the oxidation
catalyst may be replaced by a filter monolith that is not coated
with catalyst.
[0042] According to a seventh aspect of the invention, there is
provided a method by which diesel engine fuel may be injected
through an injector valve that provides vaporized engine fuel into
the central area of the further improved reversing flow catalytic
converter within the flow redirection bowl. Diesel engine fuel
passes into the flow redirection bowl through a bulkhead fitting
into a coiled small diameter tubing section that provides
sufficient heating surface to vaporize diesel fuel components into
the flow redirection bowl. Diesel fuel is provided to the bulkhead
fitting from a connecting pipe that connects a diesel fuel supply
manifold that in turn receives diesel fuel supply from the high
pressure diesel injector low pressure supply pump. The manifold
contains the diesel injector, an associated flow orifice to control
diesel flow, an associated check valve to block diesel flow during
air purge and an associated strainer to filter diesel fuel within
the manifold block before the injector. The manifold also contains
an air injection solenoid valve that purges diesel fuel from the
line downstream of the diesel injector by briefly injecting vehicle
air into the diesel injection line when the engine is shut down.
The method comprises of steps of monitoring temperature of the
monolith material and controlling a fuel injector valve mounted on
the flow redirection bowl of the further improved reversing flow
converter to inject metered quantities of fuel required to maintain
a preset oxidation temperature of the monolith material. The method
includes the provision of a control interlock such that in the
event of overheating for any reason, the power to the fuel injector
valve will be locked out until the overheat condition is removed.
Additionally, when an overheat event occurs, the engine fuel supply
will be adjusted to reduce total hydrocarbons and carbon monoxide
volume in the exhaust.
[0043] According to an eighth aspect of the invention, there is
optionally provided, a three position valve and rotary stepper
motor actuator which includes valve positions for; forward, reverse
and bypass flow. In this aspect, the valve position is determined
by a pneumatic or electric stepper motor that is driven by a
control method similar to that described earlier for the reverse
flow oxidizing catalytic converter, comprised of steps of
monitoring temperature and rate of temperature rise of the
oxidizing filter trap and controlling valve position such that
exhaust gases are permitted to flow from the engine to the tail
pipe without passing through the oxidizing filter trap when the
temperature of the monolith exceeds a predetermined threshold. This
is the third or bypass valve position
[0044] Other features and advantages of the invention will be more
clearly understood with reference to the preferred embodiments
described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] The invention will now be further described by way of
example only, and with reference to the accompanying drawings, in
which:
[0046] FIG. 1 is a side elevation view of the further improved
reverse flow catalytic converter of the present invention which
includes an improved bypass mechanism to control overheating of the
catalytic material in the catalytic converter, an improved valve to
operate with low drag and low leakage and an improved diesel fuel
injection system;
[0047] FIG. 2 is a cross-sectional plan view taken along line A-A
of the actuator 202 of FIG. 1 to show the structure of a rotary
actuator for driving the valve;
[0048] FIG. 3a is a cross-sectional plan view taken along line B-B
of the improved bypass mechanism 316 of FIG. 1 to illustrate an
improved center return mechanism in a first position corresponding
to that of the actuator shown in FIG. 2, and in dashed lines in a
second position corresponding to a second position of the actuator
shown in dashed lines in FIG. 2;
[0049] FIG. 3b is a cross-sectional plan view taken along line B-B
of the improved bypass mechanism 316 of FIG. 1 to illustrate an
improved center return mechanism in position for bypass mode
corresponding to the actuator neutral position shown in dashed
lines in FIG. 2;
[0050] FIG. 4a is a top plan view of the improved valve housing
301, showing the inlet and outlet piping with flanges and the
actuator and improved spring return in a stack mounted at the
center of the improved valve top cover plate.
[0051] FIG. 4b is a elevation view of the improved valve housing
301, showing the inlet and outlet piping with flanges and the
actuator and improved spring return stack mounted on the improved
valve top cover.
[0052] FIG. 4c is a bottom plan view of the improved valve housing
301 showing the improved valve bottom plate and its two openings to
communicate with the two container chambers.
[0053] FIG. 5a is an elevational view of the oxidation catalyst or
filter catalyst monolith of the further improved reverse flow
catalytic converter showing the monolith and transverse separation
wall of the inlet section of the can in dashed lines.
[0054] FIG. 5b shows the can top plan view of the can and monolith
302 (section E-E of FIG. 1) and FIG. 5c shows the bottom plan view
of the can and monolith 302.
[0055] FIG. 6a shows the flow re-direction bowl 303 in elevational
view with capillary tubing shown in dashed lines.
[0056] FIG. 6b shows the flow re-direction bowl 303 from its top
plan view (section G-G of FIG. 1) showing the diesel injection
capillary tubing and bulkhead fitting as well as an RTD mounted
within the bowl.
[0057] FIG. 6c is a schematic showing the injection manifold 347
with its associated flow components.
[0058] FIG. 7 is a cross-sectional plan view (section C-C of FIG.
1) of the improved valve housing 301 with inlet and outlet openings
in the valve cover plate superimposed in dashed lines and the
flapper shown covering two wall ports.
[0059] FIG. 8a is an elevational cross-sectional view (section H-H
of FIG. 7) showing wall sections 350 and 351 within the improved
valve structure housing 301 in a first direction.
[0060] FIG. 8b is an elevational cross-sectional view (section J-J
of FIG. 7) of the flapper 348 mounted within the improved valve
structure housing 301 in a second direction.
[0061] FIG. 8c is an elevational cross-sectional view (section K-K
of FOG. 7) showing wall sections 352 and 353 within the improved
valve structure housing 301 in a second direction.
[0062] FIG. 9a is a bottom diagrammatic plan view of the bottom of
the improved valve 301 showing exhaust flow paths for one position
of the improved valve flapper in which exhaust gas from the engine
enters the bottom inlet pipe and is redirected to the right hand
side bottom plate valve opening and into the monolith and the flow
that leaves the monolith enters the valve through the left hand
opening of the improved valve bottom plate and is directed into the
valve exhaust piping to the tail pipe. FIG. 9b is a similar
improved valve 301 bottom view showing the flapper in the second
position redirecting engine exhaust flow into the monolith on the
left hand side and out of the monolith on the right hand side and
into the valve exhaust opening into the tail pipe. FIG. 9c is a
similar bottom plan view of the improved valve 301 with the flapper
in the bypass position allowing direct communication from the
engine exhaust to the tail pipe directly through the valve and
bypassing the monolith.
[0063] FIG. 10 is a schematic plan for the control system 262
employed by the further improved reversing flow catalytic converter
300.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0064] FIG. 1 illustrates a further improved catalytic converter
300 in accordance with an embodiment of the present invention which
incorporates a safeguard system to inhibit overheating the catalyst
monoliths, an improved valve assembly, an improved spring return
and an improved monolith can and re-direction bowl with improved
diesel fuel injection.
[0065] With reference to FIG. 1, the catalytic converter 300
comprises a improved container 302 and improved valve housing 301
with a similar function as described in U.S. patent application
Ser. No. 11/212,608. A rotary actuator 202 and a center return
mechanism 316 are mounted on the drive shaft 50 of the valve
flapper parts 348 and 349. The rotary actuator 202 is controlled to
periodically rotate the valve flapper parts 348 and 349 between the
first and the second positions to reverse gas flow through the
container 302.
[0066] As shown in FIG. 2, the rotary actuator 202 includes a
housing 206 which encloses a pressure chamber 208. A moveable vane
210 is mounted to drive shaft 212 which is adapted to be connected
to the shaft 50 of the valve flapper parts 348 and 349 to rotate
together therewith. The housing 206 has a first opening 214 and a
second opening 216 in the respective side walls of the housing 206
so that the moveable vane 210 rotates clockwise until it abuts a
left stop member 218 when pressurized fluid is injected into the
pressure chamber 208 through the first opening 214. This position
of the moveable vane 210 corresponds to the first position of the
valve flapper parts 348 and 349 as shown in FIGS. 7 and 9b, to
permit the exhaust gases to flow through the container in a first
direction. Similarly, the moveable vane 218 rotates counter
clockwise until it abuts a right stop member 220, as shown in
broken lines at the right side, when the pressurized fluid is
injected into the pressure chamber 208 through the second opening
216. This position corresponds to the second position of the valve
flapper parts 348 and 349, as shown in FIG. 9a, to permit the
exhaust gases to flow through the container 302 in the opposite
direction.
[0067] As shown in FIGS. 3a and 3b, the center return mechanism 316
includes a base block 323 having a circular bore 321 at an apex of
triangular cavities 324 and 325. A swivel arm 322 is connected on
both ends to a pivot shaft 358 that is rotatably mounted in the
bore 321 of the base block. Four coil springs 317,318,319 and 320
are retained in the annular grooves 359 and 360, each is restrained
between one end of the grooves 359 and 360 and one side of the
swivel arm 322. A connector (not shown) is integrally formed with
the pivot shaft 358, having a square cross-section adapted to
receive a square top end of pivot shaft 212(not shown) of the
rotary actuator 202. The swivel arm members 322 are adapted to
swivel within the triangular cavities 324 and 325 and compress two
of the springs 317, 318, 319 and 320 as they swivel. The other of
the springs 317, 318, 319 and 320 are free to expand within the
annular grooves. A cover 243 (not shown) is provided to retain the
swivel arms 322 and springs 317, 318, 319 and 320 within the base
block 323. When the pressure vane 210 of the rotary actuator 202 is
at the left side, corresponding to the first position of the valve
flapper 348 shown in FIGS. 7 and 9b, the swivel arm 322 of the
center return mechanism 316 compresses springs 317 and 318. When
the pressure vane 210 of the rotary actuator 202 pivots to the
right side as shown in the broken line at the right side of FIG. 2,
the valve flapper parts 348 and 349 are in the second position as
shown in FIG. 9a. However, when the rotary actuator 202 is
deactivated (no fluid pressure is applied to either side of the
pressure vane 210), the swivel arm 322 of the center return
mechanism 316 is forced by two of the springs 317 and 318, to
return to the central position shown in FIG. 3b. This moves the
pressure vane 210 of the rotary actuator 202 to the central
position shown in broken lines in FIG. 2. It also moves the valve
flapper parts 348 and 349 to the bypass position shown in FIG.
9c.
[0068] FIGS. 4a, 4b and 4c illustrate features of the improved
valve housing. FIG. 4a is a plan view of the valve housing showing
inlet flange 312 and inlet pipe 313 receiving exhaust gas from a
diesel engine and outlet pipe 315 and outlet flange 314 discharging
purified exhaust gas to the vehicle tail pipe. FIG. 4a also
illustrates valve cover plate 310 and the two openings in the cover
plate 329 and 328 allowing gas to pass into and out of the valve
housing inlet and outlet compartments formed by valve interior
walls 350, 351, 352 and 353 of FIG. 7 FIGS. 4a and 4b also show
improved spring return 316 and actuator 202 mounted to the valve
cover 310 and to each other by a bracket (not shown) and connected
to shaft 50 that also connects to improved valve flapper parts 348
and 349 of FIG. 7. FIG. 4b also shows the outer improved valve
outer assembly consisting of outer wall 330 that is welded to top
flange 311 that fastens to valve cover plate 310 and valve bottom
flange 309 that also is welded to outer wall 330.
[0069] FIG. 4c is is a bottom view cross-sectional along line D-D
of FIG. 1 showing the valve bottom plate 309 and its two ports 326
and 327 that connect to can chambers 333 and 334 of FIG. 5b.
[0070] FIGS. 5a, 5b and 5c illustrate the further improved
reversing flow catalytic converter can and substrate section 302.
FIG. 5a is an elevational view of the can and substrate section 302
including can upper and lower flanges 308 and 306 respectively
attached to wall section 331, and transverse wall section 335 in
dashed lines and attached to flange 308 and wall 331 and sealed to
the upper surface of monolith or substrate 336 surface also in
dashed line. FIG. 5a also shows the preferred mountings of
resistance temperature detectors (RTDs) 307, approximately 1/4 and
1/2 of the way down the substrate on each side of the transverse
wall and below the substrate 336 surface. FIG. 5b is a top plan
view of the can or cross-sectional vied along line E-E of FIG. 1
showing the transverse wall 335 and the substrate 336 visible
through can chamber openings 333 and 334. FIG. 5c is a bottom can
or cross-sectional view along line F-F of FIG. 1 showing the
exposed substrate 336 mounted flush with bottom flange 306.
[0071] FIGS. 6a, 6b and 6c illustrate the further improved
reversing flow catalytic converter flow re-direction bowl 303 and
diesel fuel injection capillary tubing 337 as well as a schematic
showing the diesel injection block 347 with its integral
components. FIG. 6a shows an elevational view of the flow
re-direction bowl 303 comprised of flange 305 and bowl container
332. Also shown in FIG. 6a is a tubing bulkhead fitting 304,
internal coiled tubing 337 in dashed lines supported by a bracket
(not shown) and RTD 307. FIG. 6b is a plan view of cross-sectional
area along line G-G of FIG. 1, showing flange 305 and bowl
container 332, bulkhead fitting 304, coiled tubing 337 and RTD 307.
The schematic shown in FIG. 6c reveals the manifold block 347 with
internally mounted components; check valves 342, filter screen 340
and orifice 341. A diesel supply from the diesel fuel supply pump
345 enters the manifold block 347, is filtered by screen 340 before
passing to a diesel injector valve 339 that is under control of
converter controller 262 of FIG. 10 and then passing through a flow
control orifice 341 and check valve 342 and thence out of the
manifold block into tubing leading directly to bulkhead fitting
304. The manifold block 347 also contains flow passages tha direct
air from vehicle air supply 346 directly to air purge solenoid 344
and then through check valve 343 and directly to tubing leading to
bulkhead fitting 304. When the vehicle is shut down, the converter
controller 262 will de-activate diesel injection solenoid 339
blocking diesel flow and briefly activate air purge solenoid 344
sufficient to clear diesel fuel from the tubing leading to bulkhead
filling 304 and from capillary tubing 337 so that caking of the
tubing is prevented.
[0072] FIG. 7 is a cross-sectional plan view along line C-C of FIG.
1 illustrating the internal wall system consisting of walls 350,
351, 352 and 353 that converge near the center of the valve and
around valve shaft 50 that is connected to valve flapper sections
348 and 349. The angles subtended by the wall system are about 60
degrees in the directions of inlet opening 328 and outlet opening
329 in valve cover plate 311 and about 120 degrees in the
directions of valve bottom plate 309 openings 326 and 327 that
connect to can cavities 333 and 334 of FIG. 5b. As shown in FIG. 7,
valve flapper section 348 completely covers the opening 354 of FIG.
8a in wall 350 and valve flapper section 349 completely covers the
opening 356 of FIG. 8c in wall 352.
[0073] FIGS. 8a, 8b and 8c all illustrate cross-sectional
elevations of the internal improved valve structure of wall
sections and flapper sections. FIG. 8a shows the internal
cross-sectional elevation along line H-H of FIG. 7 displaying wall
sections 350 and 351 and wall openings 354 and 355 respectively.
This view also shows top cover plate opening 329 that connects to
the inlet pipe 313 and bottom plate opening 326 that connects to
can inlet cavity 334 of FIG. 5b. FIG. 8b shows the valve internal
cross-sectional elevation along line J-J of FIG. 7 displaying the
flapper sections 348 and 349 with connected shaft 50 and wall
sections 352 and 353 in behind the flapper sections and also
showing wall openings 356 and 357 in dashed lines. In this
illustration, the flapper section completely seals wall opening 356
in wall section 352 and completely uncovers wall section opening
357 in wall section 353. FIG. 5c shows the valve internal
cross-sectional elevation along line K-K of FIG. 7 displaying wall
sections 352 and 353 along with wall section openings 356 and 357
respectively. In the position of valve flapper sections 348 and 349
shown in FIG. 7, opening 356 of wall section 352 is completely
sealed by flapper section 349 and opening 357 of wall section 353
is completely uncovered. With the valve flapper position shown in
FIG. 7, engine exhaust gases enter the valve housing through
opening 329 and then through wall opening 355 of wall section 351
and then through opening 326 of the valve bottom plate into can
cavity 334 and into the oxidation or filter monolith 336 down the
left hand side in FIG. 5b and then into the flow re-direction bowl
303 of FIG. 6a and then up and into the oxidation or filter
monolith right hand side of FIG. 5b and into can cavity 333 and
then through valve bottom plate opening 327 and then through
opening 357 of wall section 353 and out of the valve housing
through top valve cover opening 328.
[0074] FIGS. 9a, 9b and 9c illustrate the valve flapper sections
348 and 349 in their three positions, for respectively forward and
reverse exhaust flow through the container 302 and for bypassing
the oxidation or filter catalytic material. For clearer
illustration, these figures illustrate only a bottom plan schematic
view of the valve housing with valve bottom plate 309 removed
exposing flapper sections 348 and 349, wall sections 350, 351, 352
and 353 and valve inlet opening 329 and valve outlet 328. The four
wall sections divide the interior cavity of the valve housing 301
into the intake cavity and exhaust cavity, and into two other valve
cavities that are essentially extensions of the two can
cavities.
[0075] When the valve flapper sections 348 and 349 are in the first
position as shown in FIG. 9a, the gas flow enters intake cavity
from the inlet opening 329. The gas flow passes through the valve
wall opening 355 in wall section 351 to enter the container through
valve bottom plate opening 326 and disperse container cavity 334
and into the cells of the catalytic material above within the
container on the left hand side of the transverse wall 335. After
the exhaust gas flow is forced through the catalytic material it
exits on the opposite side of the container transverse wall which
is on the right hand side of the transverse wall 335, and passes
first through second container cavity 333 and then through the
valve bottom plate opening 327 to the exhaust cavity through wall
opening 357 in wall section 353. The gas flow then exits through
the outlet opening 328.
[0076] As shown in FIG. 9b, when the valve flapper sections are in
the second position, it is rotated about 60.degree.
counter-clockwise so that the gas flow entering the intake cavity
through the inlet opening 329 passes through valve wall opening 356
in wall section 352. Therefore the gas flow must enter the
container through the valve bottom plate opening 327 and first move
into container cavity 333 and exit the container through container
cavity 334 and then through valve bottom plate opening 325 and
through valve exhaust opening 328 so that the gas flow in the
container is reversed, in comparison to the gas flow shown in FIG.
9a
[0077] If during the reversing flow operation of the further
improved catalytic converter 300, the temperature of the catalyst
material rises too quickly or is predicted to overheat the
catalytic material, a controller places the catalytic converter in
bypass mode. In bypass mode, the rotary actuator is deactivated by
interrupting the pressurized fluid supply (not shown) or electric
power Supply. When the rotary actuator 202 is deactivated, the
swivel arm 322 of the improved center return mechanism 316 is
forced by two of the springs 317, 318, 319 or 320, to return to its
central position as shown in FIG. 3b. Thus, the center return
mechanism 316 moves the valve flapper sections 348 and 349 to the
third (bypass) position which is between the first and second
positions, as shown in FIG. 9c. The valve flapper sections 348 and
349 are maintained in the third position until the rotary actuator
202 is reactivated. When the valve flapper sections 348 and 349 are
in the third position, the valve wall openings 354, 355, 356 and
357 communicate with both the intake cavity and the exhaust cavity.
Thus, the gas flow entering the intake cavity through the inlet
opening 329 passes directly through the valve wall openings, enters
the valve exhaust cavity, and exits the valve outlet opening 328.
Even though the valve wall openings 354, 355, 356 and 357
communicate through the first and second valve bottom plate
openings 326 and 327 with the container, the gas flow through the
valve wall openings does not enter the container 302 because the
gas pressure at the first valve bottom plate opening 326 is equal
to the gas pressure at the second valve bottom plate opening 327.
Thus, when the valve flapper sections 348 and 349 are in the third
position, the exhaust gases bypass the container 302.
[0078] The further improved catalytic converter 300 described above
with reference to FIGS. 1 through 9c is preferably controlled by a
control system, a preferred embodiment of which is illustrated in
FIG. 10. During normal engine operation and normal reverse flow
catalytic converter operation, a controller 250 monitors the
temperature of the catalytic material in the catalytic converter.
Resistance temperature detectors (RTDs) 307 attached to the
catalytic converter 302 and 303, or imbedded in the catalytic
material, are preferably used to measure temperatures of the
catalytic material.
[0079] As long as the temperature measured is within a
predetermined range, the controller controls the rotary actuator
202 to achieve cyclic reverse flow through the catalytic converter
by periodically rotating valve 301 so that the reverse flow valve
301 is moved between the first and second positions. If an
abnormally sharp rise in temperature is detected, or if the
temperature of the catalytic material rises above a threshold that
will predictably damage the catalytic material, the controller 250
enters the bypass mode. During the bypass mode, the controller 250
deactivates the rotary actuator 202. When the rotary actuator 202
is deactivated, the improved center return mechanism 316 forces the
reverse flow valve 301 into the third position to cause the gas
flow to bypass the catalytic converter 302/303, as described above
with reference to FIG. 9c.
[0080] Exhaust flow bypass is a first safeguard action to prevent
damage to the reversing flow catalytic converter. Adjusting engine
fuel supply is another. Therefore, when the controller enters
bypass mode, it sends a signal to the engine controller 252. The
engine controller responds to the signal by adjusting the engine
fuel supply to reduce total hydrocarbon and carbon monoxide volume
in the exhaust gases.
[0081] As seen in FIG. 10, an auxiliary catalytic converter 254
connected in series to the engine exhaust system downstream of the
reverse flow catalytic converter 302/303 may be optionally
installed During bypass mode, the controller 250 activates the
valve 256 to direct the exhaust flow to pass through the auxiliary
catalytic converter 254, which will oxidize at least a part of the
carbon monoxide and hydrocarbons during the bypass mode. The
auxiliary catalytic converter may be smaller and less expensive
than the reversing flow catalytic converter 300.
[0082] A look-up table 258 may be accessed at the controller 250.
The look-up table 258 stores data defining a dynamic limit of a
rate of rise of the temperature of the catalytic converter 300.
Each time the controller 250 samples the temperature of the
catalyst using the RTDs 307, the controller 250 calculates the
dynamic rate of rise in the temperature and compares the dynamic
rate of rise in the temperature with entries in the look-up table
258, to obtain an early indication of overheating in the catalyst.
The controller 250 must promptly respond to an indication of
overheating in the catalytic material. The more quickly the
controller 250 responds to the prediction of overheating in the
catalytic converter, the better the catalyst is protected. A quick
response will protect the washcoat from damage whereas a delayed
response may only protect the monolith from meltdown. The control
system therefore needs to be sensitive enough to protect the
washcoat most of time and invariably prevent meltdown of the
monolith substrate. However, over-sensitivity will trigger catalyst
protection when it is not required. Frequent triggering of
unwarranted catalyst protection will compromise engine performance
in the case of engine management-systems and unnecessarily increase
emissions in the case where bypass protection is used.
[0083] The control algorithm used by the controller 250 therefore
determines when to enter bypass mode based on catalyst temperature
thresholds. Appropriate setting of the temperature thresholds will
safeguard the catalyst from overheating provided there is a slow
climb in catalyst temperature. However, static temperature
thresholds are not sufficient to prevent the catalytic washcoat
from damage if operating conditions cause a serious fuel management
problem. Serious fuel management problems may result in a sustained
rate of temperature rise over 20-30.degree. C./second. Due to the
inherent delay in temperature sensing and processing, and a slight
delay in the response of the bypass mechanism, an early prediction
of overheating is required to protect the washcoat.
[0084] It should be noted that only catalyst temperatures are used
to predict overheating by the control algorithm. The catalyst
temperature and the rate of temperature rise in the catalyst
temperature are used by the control algorithm. The engine exhaust
temperature is not measured or considered, because exhaust
temperatures vary at a much greater rate than catalyst temperature
variation during normal engine operating conditions.
[0085] As an example, described below is a safeguard system for
preventing overheating of a reversing flow catalytic converter used
for a diesel/natural gas duel fuel engine.
[0086] Three Type-K thermocouples were installed in the catalytic
converter, one at each side of the boundary layers, that is, inside
the catalyst substrate, and a third one at the bottom center of the
container structure. Type-K thermocouples are commonly used to
measure temperatures of 0.degree. to 1250.degree. C. in various
industrial processes. For balancing control of a catalyst flow-path
temperature profile, two boundary thermocouples are preferred so
that heat is measured more efficiently. For catalyst overheat
protection, the two boundary thermocouples and the central
thermocouple are required to provide early warning of any fuel
management faults. The control algorithm used by the controller 250
provides the system with the following functionality: [0087] The
reverse flow mode is terminated when all three thermocouples
measure catalyst temperatures lower than 300.degree. C. When any
one of the three thermocouples measure a catalyst temperature
higher than 350.degree. C., the reverse flow mode is turned on.
[0088] The controller continuously computes rates of temperature
rise in the catalyst and compares each computed rate of rise with
predetermined values in the look-up table 258. The controller 250
triggers the system into bypass mode if a rate of temperature rise
listed in the look-up table is exceeded by a computed rate. After
entering bypass mode, the reverse flow catalyst converter is
bypassed, as explained above. A prediction that the catalyst is
about to overheat also triggers the engine controller 252 to switch
to diesel mode. This shuts off the natural gas fuel supply and
causes the engine controller to begin self-diagnostics. The engine
controller 252 is also preferably programmed to operate the engine
in a special diesel mode, in which the diesel injection timing is
advanced as compared to normal diesel mode in order to lower engine
exhaust temperature The reverse flow mode is resumed after the
catalyst has cooled down to a predetermined restart threshold,
580.degree. C., for example. If each of thermocouples indicate
temperatures that are lower than the restart threshold, and a
catalyst damage flag has not been set, the reverse flow mode is
resumed. The controller 250 sets a damage flag when any one of the
thermocouples indicates a temperature that exceeds a temperature
that might damage the catalyst. If a damage flag is set, the
reverse flow mode is not resumed until the catalytic material has
cooled to temperature below a predetermined threshold.
[0089] The effectiveness of the safeguard system is ensured by
multiple thresholds and the combination of static and dynamic
temperature tracking. A performance evaluation test for the
safeguard system was conducted to test the effectiveness of the
catalyst temperature control and the durability of control
functionality under a wide range of engine and vehicle operating
conditions, including fuel management system failures. Evaluation
tests demonstrated that the safeguard system reliably activated
each time the controller determined that protection mode was
required. For slow temperature rise, the onset of the bypass mode
was triggered by either inlet or outlet catalyst temperature
readings exceeding the static temperature threshold. Test results
showed that the onset of bypass mode almost immediately stopped
monolith temperature rise under slow temperature rise conditions.
If an abnormal rate of temperature rise triggers bypass mode, the
onset of bypass mode rapidly reduces and subsequently reverses the
temperature rise. The tests indicted that the safeguard system
reliably prevented meltdown of the catalyst under these
conditions.
[0090] The protection of the catalyst washcoat is more difficult,
mainly because of the narrow line between optimized working
catalyst temperatures and washcoat damage temperatures. The
catalyst tested worked best when bed temperatures were maintained
between 580.degree. and 640.degree. C. and peaked at 720.degree. C.
Catalyst ageing is accelerated above 730.degree. C. and reactivity
deteriorated over 760.degree. C. If high concentrations of
hydrocarbons are present in the exhaust gases, a flame may be
sustained in the valve housing for some time during bypass mode.
Under such circumstances, the cavity of the valve housing is the
hottest zone and conducts heat to the top of the monolith. However,
the flame does not propagate to the inside of the catalyst because
bypass mode stops gas flow through the catalyst. Rapidly adjusting
the engine fuel supply provides improved protection for the
washcoat.
[0091] The monolith material 336 of FIG. 5 can be either an
oxidation substrate or a particulate filter substrate with or
without a catalyst washcoat.. The replacement of the oxidation
monolith with an oxidation particulate filter trap in FIG. 5
monolith 336. When used with a diesel engine, the oxidizing filter
trap will trap and hold particulate matter to allow effective
oxidation of the carbon kernel as well as the volatile organic
fractions of the particulates.
[0092] In FIG. 6, the location and mounting of a fuel injection
valve 339 is illustrated on a diesel injection manifold 347. For a
dual fuel engine, it is not likely that supplementary fuel
injection will be needed, but if it is deemed useful, the injector
valve 339 will be one designed for gaseous fuel injection in time
duration pulses. If the reverse flow oxidizing converter is to
treat exhaust gases from a diesel engine, then the injector valve
339 will be one designed for diesel fuel injection as a fine mistor
vapour. The injector valve 339 supply 345 and a manifold block 347
complete with filter 340, fuel flow control orifice 341 and check
valve 342. The manifold block will also have an air purge system
momentarily activated on engine shut down to clean out the diesel
lines feeding the converter. An air supply 346 is connected to the
manifold block 347 along with a check valve 343 and air purge
solenoid 344. A wiring harness for power to activate the injector
valve 339 and air purge solenoid 344 under command of the converter
controller 250 shown in FIG. 10. Power will be applied to the
injector valve 339 when the temperature profile is insufficient for
oxidation and power will be locked off the injector valve 339 when
the controller 250 is reacting to an overheat event. It is
preferable to install diesel injector valve manifold diesel piping
to bulkheads fitting 304 on the flow re-direction bowl 303. The air
purge solenoid will normally not be activated and will only be
momentarily activated on engine shutdown sufficient to blow all
diesel fuel from the diesel injection circuit including coiled
capillary tubing 337 within the flow re-direction bowl 303.
[0093] In the cases of both the oxidizing catalytic converter and
the oxidizing catalytic filter, it may be feasible to reduce the
amount of catalytic loading and maintain temperature at oxidizing
levels by the use of incremental fuel injection by way of fuel
injector valve 339. In the limit, with sufficient exhaust fuel
injection, catalytic coating may not be required. The amount of
catalytic material may be balanced against the amount of fuel
consumed in a case by case assessment of each application
[0094] The control schematic of FIG. 10 shows a means of diesel
injection with reverse flow controller 250 that can be used for the
oxidizing converter or for the oxidizing particulate trap reverse
flow controller. When the RTDs 307 detect a monolith temperature
moving downward and approaching the catalytic light off
temperature, the converter controller 250 will command the fuel
injection valve 339 to pulse a metered volume of fuel into the
converter re-direction bowl through bulkhead fitting 304. As the
temperature moves upward from the added heat of the oxidizing fuel,
the controller 250 will monitor the rate of temperature rise, and
if below a selected threshold rate of rise, the controller will
pulse more fuel into the converter. This action will continue until
the monolith temperature is detected to be sufficiently above
catalytic light off temperature to sustain continuous oxidation of
particulate matter. Under conditions of catalyst overheat, the
power to the fuel injector 339 will be disconnected until the
overheat event is over. The control algorithm earlier described
will act on both static temperature measurements and rate of
temperature rise calculations for the oxidizing filter monolith in
the same manner as for the oxidizing flow through catalyst
monolith.
[0095] The advantages of the further improved catalytic converter
described above are apparent. No plumbing is required between the
converter unit and the valve unit, which makes the catalytic
converter compact and inhibits heat loss between the valve and the
catalyst. The valve flapper is rotated about a perpendicular axis,
which provides a smooth and reliable valve operation in a minimum
of space. The unique arrangement of the monolith improves catalyst
life and conversion performance. And the reversing exhaust gas flow
ensures maximum efficiency of conversion by keeping the catalyst
material uniformly heated and in addition small incremental fuel
additions help to increase catalytic activity for pollutant
reduction. Furthermore, the safeguard system including the improved
spring return mechanism used with the catalytic converter
effectively safeguards the catalytic converter from damage due to
overheating and effectively improves catalyst life. An additional
advantage is the ability of the reverse flow catalytic converter to
be optionally modified to work effectively and efficiently as a
continuous oxidation particulate filter trap.
[0096] In view of the above, it will be seen that the several
objects of the invention are achieved and other advantageous
results attained. Various changes could be made in the above
methods and constructions without departing from the scope of the
invention, which is limited solely by the scope of the appended
claims.
* * * * *