Exhaust restriction device

An exhaust restriction device for an internal combustion engine is disclosed. The exhaust restriction device includes a main valve and a bypass valve for restricting the flow of exhaust gas. The main valve is located in a main passage and may be selectively closed. The bypass valve is located in a bypass passage and is biased into a position closing a port connecting the main passage and the bypass passage. Closing the main valve may cause exhaust back pressure to build against the bypass valve and an actuator therefor until the biasing force is overcome. When the biasing force is surpassed by the exhaust back pressure, the bypass valve opens to relieve the back pressure. The bypass valve closes when back pressure falls below the biasing force. A method of operating the exhaust restriction device is also disclosed.

FIELD OF THE INVENTION 
The present invention relates to devices used to restrict exhaust gas flow 
through an internal combustion engine. More specifically, the invention 
relates to control of the flow of exhaust gas through an engine in order 
to accelerate warm-up of the engine. 
BACKGROUND OF THE INVENTION 
Presently, it is not uncommon for vehicles, such as trucks and buses, to be 
equipped with an exhaust restriction device. Such devices may be used for 
exhaust braking or for engine warm-up. Fundamentally, an exhaust 
restriction device need only comprise some means for restricting the flow 
of exhaust gas from an internal combustion engine. Restricting the exhaust 
gas increases the exhaust manifold pressure, i.e. "back pressure." The 
exhaust manifold pressure may be used to oppose the motion of the engine 
pistons for engine retarding or for warm up by increasing fueling rates 
and heat rejection. Thus, the engine and vehicle may be slowed and/or 
heated in relation to exhaust manifold pressure. Selective restriction of 
the flow of exhaust gas from the engine may therefore be used to 
selectively brake or warm up a vehicle. 
Exhaust manifold pressure produced by an exhaust restriction device may be 
particularly useful in warming an engine during positive power operation. 
A cold engine may be more quickly warmed by placing the engine under load 
during positive power operation. Closing an exhaust restriction device 
during positive power creates an engine load because it makes it more 
difficult for the pistons to cycle in the cylinders. The exhaust 
restriction device creates this load by backing up warm exhaust gases in 
the engine and exhaust manifold which causes the engine to increase fuel 
consumption and increase heat rejection. Placing the engine under load 
increases the rate of raising vehicle cab temperature and decreases warm 
up time. Placing the engine under load by increasing exhaust manifold 
pressure is also desirable because it raises exhaust temperature, which 
promotes combustion and decreases carbon build up. Decreases in carbon 
help to alleviate emissions concerns, as well as problems with engine 
valve sticking. 
One device for producing exhaust back pressure using a butterfly valve to 
restrict exhaust flow from a turbo charger outlet is disclosed in U.S. 
Pat. No. 5,079,921 to McCandless et al. In the device disclosed in this 
patent, the control of exhaust pressure results solely from opening and 
closing a butterfly valve adjacent to an engine turbocharger. 
A device for producing a desired level of intake manifold pressure, as 
opposed to exhaust manifold pressure, is disclosed in U.S. Pat. No. 
4,005,578 to McInerney. This device is also for use in conjunction with a 
turbocharger. The turbo compressor output is regulated by control of 
exhaust flow through the turbo turbine. This device does not control 
exhaust flow in response to the pressure in the exhaust system. 
Devices for modulating exhaust flow are disclosed in U.S. Pat. No. 
5,372,109 to Thompson et al. One of the disclosed devices includes a 
plunger to cover a bleed flow path. The plunger is controlled by computer 
controlled application of air or hydraulic fluid to the plunger. The 
plunger is not controlled by the application of exhaust gas to any 
actuation means. Another of the disclosed devices in Thompson includes a 
reed valve to cover a bleed flow path. The amount of deflection of the 
reed valve is the direct result of the application of exhaust pressure 
through the bleed flow path to the reed valve. 
Some other exhaust restriction devices have been designed to provide a 
fixed maximum level of back pressure over a range of engine speeds. In 
such exhaust devices, control of the exhaust manifold pressure may be 
achieved by control of the restriction of exhaust gas flow by the device. 
These exhaust restriction devices may typically allow back pressure to 
build to a preset limit. Back pressure which exceeds the preset limit is 
relieved via a bypass around the closed exhaust restriction device. For 
example, U.S. Pat. No. 5,638,926 to McCrickard discloses an exhaust brake 
having a main tube and a bypass tube. During exhaust braking, the main 
tube is blocked with a rotatable valve. Back pressure is relieved by 
opening a bypass valve located at the downstream end of the bypass tube. 
Also see U.S. Pat. Nos. 4,750,459 and 4,682,674 to Schmidt, and U.S. Pat. 
No. 5,372,109 to Thompson et al., which disclose alternative bypass 
arrangements for an exhaust restriction device. 
One impediment to the operation of known exhaust restriction devices is 
that they may expose the bypass valve, including its actuation means, to 
harsh temperatures and pollutants. 
Bypass systems, preferably, should be constructed to remain operable under 
the harsh conditions experienced within an exhaust restriction device or 
removed from such harsh conditions. Exhaust gas typically contains carbon 
particles, water moisture, and other contaminants within it. Exposure of 
the moving parts of a bypass system to exhaust gas and its contaminants 
can cause the moving parts to corrode/oxidize and become coked/coated with 
carbon. Bypass valves, such as the one disclosed in the above-referenced 
McCrickard, Schmidt, and Thompson et al. patents, may become inoperable 
because of the build up of contaminants on the moving parts in the system. 
Accordingly, there is a need for an exhaust bypass system that is less 
prone to malfunction as a result of carbon, rust, or other contaminant 
build up on the moving parts of the bypass. 
Furthermore, bypass systems should preferably be designed to avoid the 
exposure of heat sensitive elements of the bypass from being over exposed 
to high temperature exhaust gas. A bypass system may use a spring and/or 
electronic activators to open and close the bypass. These types of 
elements may not operate well under the fluctuating or extreme temperature 
conditions experienced within an exhaust restriction device. Accordingly, 
there is a need for an exhaust restriction device with a bypass actuator 
that is sufficiently thermally isolated and/or that has an acceptable 
tolerance of high temperature exhaust gas. 
One of the designs described herein is a bolt-on bypass circuit which may 
be very effective at reducing the exposure of the bypass spring and/or 
electronic activators to exhaust gas temperatures. A bolt-on bypass may 
also add the benefit of flexible manufacturability which allows for a 
fixed flow area device or a variable area device with minimal 
manufacturing set up changes. A bolt-on bypass may be used with an exhaust 
restriction device that is pre-configured to accept the bypass. The 
exhaust restriction device may be provided originally with two or more 
plugged ports. The ports may be unplugged when a bolt-on bypass is added 
to provide exhaust gas flow to and from the bypass. 
Another advantage of the exhaust restriction designs described herein, is 
the suitability of the designs to provide both an exhaust brake and a warm 
up device. 
OBJECTS OF THE INVENTION 
It is therefore an object of the present invention to provide an exhaust 
restriction device that may serve as both an exhaust brake and a warm up 
device. 
It is another object of the present invention to provide an exhaust 
restriction device with a bypass around a main valve in the exhaust 
restriction device. 
It is a further object of the present invention to provide selective 
activation of a bypass valve in an exhaust restriction device. 
It is still another object of the present invention to isolate a means for 
operating a bypass valve in an exhaust restriction device from exhaust gas 
born contaminants. 
It is still another object of the present invention to isolate a means for 
operating a bypass valve in an exhaust restriction device from high 
temperature exhaust gas. 
It is yet another object of the present invention to provide selective 
activation of a bypass valve in an exhaust restriction device responsive 
to an engine condition. 
It is still yet another object of the present invention to provide an 
exhaust restriction device that is useful as a warm-up device for an 
engine. 
It is yet a further object of the present invention to provide an exhaust 
restriction device that makes use of bolt-on bypass system. 
It is still a further object of the present invention to provide a method 
of operating an exhaust restriction device to warm up an engine. 
Additional objects and advantages of the invention are set forth, in part, 
in the description which follows and, in part, will be apparent to one of 
ordinary skill in the art from the description and/or from the practice of 
the invention. 
SUMMARY OF THE INVENTION 
In response to the foregoing challenge, Applicants have developed an 
innovative, exhaust restriction device for carrying out engine warm-up, 
comprising: a main valve provided in a main passage running through the 
device; a bypass valve provided in a bypass passage running through the 
device, said bypass passage being connected to the main passage at a 
connection point upstream of the main valve; means for biasing the bypass 
valve to block the upstream connection point between the main passage and 
the bypass passage; means for opening the bypass valve responsive to a 
level of exhaust back pressure applied to the opening means; and means for 
transferring exhaust back pressure from the main passage to a chamber 
included in the opening means. 
Applicants have also developed an innovative method of operating an exhaust 
restriction device to carry out engine warm-up, the method comprising the 
steps of: providing an exhaust restriction device with a main valve and a 
bypass valve, said bypass valve including a bypass valve stopper and a 
bypass valve actuator; selectively biasing the bypass valve into a closed 
position; selectively closing the main valve; increasing exhaust back 
pressure in the exhaust restriction device as a result of closing the main 
valve; applying the exhaust back pressure to the bypass valve stopper and 
the bypass valve actuator; and opening the bypass valve responsive to the 
level of exhaust back pressure applied to (1) the bypass valve stopper and 
(2) the bypass valve actuator. 
It is to be understood that both the foregoing general description and the 
following detailed description are exemplary and explanatory only, and are 
not restrictive of the invention as claimed. The accompanying drawings, 
which are incorporated herein by reference, and which constitute a part of 
this specification, illustrate certain embodiments of the invention, and 
together with the detailed description serve to explain the principles of 
the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference will now be made in detail to a preferred embodiment of the 
present invention, an example of which is illustrated in the accompanying 
drawings. A preferred embodiment of the present invention is shown in FIG. 
1 as exhaust restriction device 10. 
In a preferred embodiment, the exhaust restriction device 10 comprises a 
main housing 100, a bypass valve 200, and an actuator 300. The main 
housing 100 may be further broken down into a primary exhaust housing 110 
and a bypass exhaust housing 150, although the primary and bypass exhaust 
housings may be integrally formed in some instances. Both the primary and 
bypass exhaust housings may be cast and machined metal housings in a 
preferred embodiment of the invention. In a preferred embodiment of the 
invention, the bypass exhaust housing 150 may be bolted on the primary 
exhaust housing 110. 
The primary exhaust housing 110 may have a main passage 112 extending 
therethrough, and an upstream inlet 114 and a downstream outlet 116. The 
inlet 114 may be connected to an upstream exhaust conduit (not shown) 
leading from an engine exhaust manifold or turbocharger outlet. 
Alternatively, the inlet 114 may be directly connected to a turbocharger 
outlet, or in a further alternative, the primary exhaust housing 110 may 
be integral with a turbocharger housing. The outlet 116 may be connected 
to the remainder of a vehicle exhaust system, which may include a muffler 
and exhaust pipe, and/or a turbocharger (not shown). 
The primary exhaust housing 110 also includes a main exhaust valve, or gate 
118 which may be used to selectively block and unblock the passage 112. 
The gate 118 is shown to be a butterfly valve in FIG. 1. The gate 118 may 
have an axle 120 running through a central region of the gate. The axle 
120 may extend from the gate 118 through the primary exhaust housing 110 
to an actuator (not shown) for the gate outside of the primary exhaust 
housing. The gate actuator may comprise a solenoid, air, vacuum, 
hydraulic, electronic, or other type of actuation device. The gate 
actuator may be operably linked to the gate 118 so that it can rotate the 
gate in the passage 112 between blocking and unblocking positions. In 
alternative embodiments, the gate 118 may be provided by a sliding gate, 
flapper, iris type, rotary, or any other means for selectively blocking 
the flow of exhaust gas through the passage 112. 
In the preferred embodiment, when the gate 118 is in a blocking position, 
exhaust gas back pressure is increased on the upstream inlet 114 side of 
the main passage 112. When the gate 118 is in an unblocking position, the 
restriction imposed on the flow of exhaust gas through the main passage is 
minimized. The gate 118 may also be capable of holding a position 
intermediate of the blocking and unblocking positions to provide a 
predetermined level of exhaust restriction. 
The bypass exhaust housing 150 may have a bypass passage 152 extending 
therethrough, which is adapted to permit the flow of exhaust gas through 
the bypass exhaust housing. The bypass exhaust housing 150 may also 
include a bore through the wall of the housing in which a bushing 154 is 
provided. The bushing 154 may provide a sealing arrangement between the 
bypass exhaust housing 150 and a bypass valve rod 210 that extends through 
the bushing 154. 
The bypass exhaust housing 150 may be bolted, screwed, or welded onto the 
primary exhaust housing 110. Alternatively, the bypass exhaust housing 150 
may be integrally cast with the main housing. Means for sealing 156 (such 
as a gasket) the bypass exhaust housing 150 to the primary exhaust housing 
110 may be provided between the two housings. The sealing means 156 may be 
adapted to seal the two housings together to withstand the elevated 
exhaust temperatures and pressures of at least 80 psi that may occur 
within the housings during engine retarding, and of at least 30 psi during 
engine warm up 
The primary exhaust housing 110 may have two ports 122 and 124 formed in 
the wall of the housing 110 at upstream and downstream locations, 
respectively, relative to the gate 118. The ports 122 and 124 provide 
communication between the main passage 112 and the bypass passage 152. In 
a preferred embodiment of the invention, the upstream port 122 may be 
frusto-conically shaped to provide a valve seat adapted to receive a 
mating frusto-conical stopper 220, discussed below. 
The primary exhaust housing 110 and the bypass exhaust housing 150 also may 
each include integrally formed exhaust pressure passages, 128 and 158, 
respectively. The exhaust pressure passages may communicate with each 
other such that exhaust gas pressure is transmitted from the upstream side 
of the main passage 112, through the exhaust pressure passages 128 and 
158, to an exhaust pressure tube 310. The exhaust pressure tube 310 may be 
connected to the actuator 300, so that the upstream exhaust pressure in 
main passage 112 is ultimately transmitted to a chamber in the interior of 
actuator 300. 
The bypass valve 200 includes a bypass valve stopper 220 connected to a rod 
210. The connection of the stopper 220 to the rod 210 may be accomplished 
using a fastener such as a screw, weld, or rivet. The bypass valve stopper 
220 may have a frusto-conical shape in a preferred embodiment of the 
invention. The conical shape of the stopper 220 may make it less likely 
that the stopper will jam against the mating valve seat formed by the wall 
of upstream port 122. The bypass stopper 220 is preferably provided such 
that it selectively blocks and unblocks the upstream port 122. The bypass 
stopper 220 is designed such that exhaust gas pressure applied from the 
main passage 112 on the stopper tends to assist in opening the bypass 
valve. 
The rod 210 connects the stopper 220 with the actuator 300. The rod 210 may 
be slidable through the bushing 154, while at the same time being 
sufficiently sealed against the bushing to prevent exhaust gas from 
escaping past the bushing 154. The rod 210 and the stopper 220, 
preferably, may be made of stainless steel. 
The actuator 300 may be used to provide an opening force for the bypass 
valve 200. The actuator 300 may include the exhaust pressure tube 310, an 
actuator housing 320, a piston 330, a spring 340, a bypass pressure 
adjuster 350, and an actuator mount 360. The actuator housing 320 may be 
connected to the main housing 100 by the mount 360. The mount 360 may 
provide sufficient separation of the actuator housing 320 from the main 
housing 100 as to provide some thermal isolation of the actuator housing 
and components contained therein. The mount 360 may include open interior 
spaces through which cooling air may flow. The thermal isolation of the 
actuator housing 320 from the main housing 100 may enhance the consistent 
operation of the spring 340 within the actuator housing. The mount may be 
connected to the actuator housing 320 and the main housing 100 by a bolt, 
weld, rivet, or equivalent. 
The actuator housing 320 may contain a piston 330 sealed with a rolling 
diaphragm, and a spring 340 within the interior of the actuator housing. 
The interior of the actuator housing 320 is effectively divided by the 
piston 330 such that the spring 340 is on one side of the piston, and a 
hollow space or chamber 322 is on the other side of the piston. The piston 
330, rod 210, and stopper 220, may be connected together such that they 
may slide up and down as a unit. The spring 340 may bias the piston 330, 
the rod 210 and the stopper 220 combination downward, causing the stopper 
220 to seat in the upstream port 122. The spring 340 may have a length 
sufficient to remove the spring from excessive thermal loading which could 
effect the biasing force provided by the spring. The spring 340 may be 
selected to provide a relatively constant force on the piston 330 
throughout the operational travel of the spring. 
When the exhaust restriction device 10 is activated, the gate 118 may be 
rotated into a blocking position, as shown in FIG. 1. Exhaust gas flows 
into the upstream side of the main passage 112 through inlet 114 and is 
blocked by the gate 118. The blocked exhaust gas creates back pressure 
within the upstream side of the device 10. 
The opening and closing of the bypass valve 200 may be 
mechanically/pneumatically controlled responsive to the level of exhaust 
back pressure on the upstream side of the main passage 112. This back 
pressure is applied to the stopper 220, and flows through passages 128, 
158, and 310 into a chamber 322, where it is applied to the piston 330. 
The piston 330 is slidable within the actuator housing 320 and sealed to 
the wall of the actuator housing so that the exhaust back pressure does 
not substantially leak from the rod side of the piston 330 to the spring 
side of the piston. 
Because the piston 330 slides within the actuator housing 320, the chamber 
322 is variable in volume, depending upon the position of the piston 330 
in the actuator housing. When the back pressure reaches a predetermined 
limited within the chamber 322 (e.g. 30 psi), determined by the biasing 
force of the spring 340, the pressure under the piston 330, alone or in 
combination with the pressure on the stopper 220, overcomes the biasing 
force of the spring 340 and the piston is displaced upward. As the piston 
330 slides upward, it carries the rod 210 and the stopper 220 with it, 
such that the upstream port 122 is opened. Opening the upstream port 122 
tends to relieve the back pressure on the upstream side of the main 
passage 112 by allowing exhaust gas to be diverted through the bypass 
passage 152 and out of the downstream port 124 to the downstream side of 
the main passage 112. As exhaust gas flows to the downstream side of the 
main passage 112, the exhaust back pressure asserted against the stopper 
220 and the piston 330 falls until the downward biasing force of the 
spring 340 is sufficient to overcome the exhaust back pressure and re-seat 
the stopper 220 in the upstream port 122. 
The biasing force applied by the spring 340 to the stopper 220 may be 
adjusted to control the exhaust back pressure level at which the stopper 
will be opened. The biasing force may equal the maximum exhaust back 
pressure the engine valve train can accommodate. The biasing force may 
changed by adjusting the position of a nut 352. Tightening of the nut 352 
may further compress the spring 340 and increase the effective downward 
biasing force of the spring. Conversely, loosening of the nut 352 may 
decrease the effective biasing force of the spring 340. A control system 
(not shown) may be provided to adjust the nut 352 during vehicle 
operation. 
In an alternative embodiment of the invention, a system for applying air 
pressure or vacuum may be substituted for, or assist, the spring 340 as a 
means for biasing the stopper 220. 
A computer may be used to determine when the gate 118 should be opened 
based upon information received from sensors. The sensors may be used to 
sense conditions of the engine/vehicle, such as engine speed, exhaust gas 
pressure, engine temperature, exhaust gas temperature, exhaust gas 
recirculation activation, exhaust restriction device activation, 
foundation restriction device application, compression release braking 
activation, vehicle speed, cylinder pressure, intake manifold pressure, 
fuel rate, throttle position, percent of engine load, ambient temperature, 
air fuel ratio, vehicle start up time, engine coolant temperature, engine 
running time, and head rejection to coolant Btu/min. 
With regard to FIG. 2, in which like elements are identified with like 
reference numerals, in an alternative embodiment of the invention the 
biasing force on the stopper 220 is applied by an actuator 300 in the form 
of a biased pivoting arm. FIG. 3 is a pictorial view of the actuator 300, 
rod 210, and stopper 220 shown in FIG. 2. Although it is shown differently 
in FIG. 2, the stopper 220 may be conically shaped as shown in FIG. 1. 
With reference to FIGS. 2 and 3, the stopper 220 is biased downward over 
the upstream port 122 under the influence of the spring 374. The spring 
374 is under tension, and accordingly, tends to rotate or bias the arm 372 
clockwise. The clockwise rotation or bias of the arm 372 is transferred 
through an L-shaped member 370 to the rod 210. The clockwise rotation or 
bias of the L-shaped member displaces or biases the rod 210 downward, 
which in turn, displaces or biases the stopper 220 downward over the port 
122. 
The L-shaped member 370 may pass through a bushing 154, which allows the 
L-shaped member 370 to rotate within the bushing while maintaining a gas 
tight seal between the L-shaped member and the bushing. In such a manner, 
the bushing 154 may be used to prevent the exhaust gas within the bypass 
housing 150 from escaping, while at the same time allowing the biasing 
means for the actuator 300 to be located outside of the bypass housing, 
away from potentially harmful exhaust contaminants and temperature 
extremes. 
The spring 374 may be provided with an appropriate tension, such that the 
downward biasing force on the stopper 220 is overcome by a predetermined 
level of exhaust back pressure applied through port 122. For example, the 
downward biasing force on the stopper 220 may be in the range of 30 psi. 
When the exhaust back pressure in the main passage 112 exceeds 30 psi, the 
stopper 220 may be forced upwards and exhaust gas in the main passage 112 
will flow through the bypass passage 152. As a result of the diversion of 
exhaust gas through the bypass passage 152, the exhaust back pressure in 
the main passage 112 may fall below 30 psi and the stopper 220 will 
re-seat over the port 122. 
FIG. 4 is a pictorial view of one embodiment of the primary exhaust housing 
110 that illustrates the incorporation of the upstream port 122 and the 
downstream port 124 into the housing. 
It will be apparent to those skilled in the art that various modifications 
and variations can be made in the construction, configuration, and/or 
operation of the present invention without departing from the scope or 
spirit of the invention. For example, in the embodiments mentioned above, 
means other than a spring, such as hydraulic, electronic, air, vacuum, 
etc., may be used to bias the bypass valve stopper into a closed position, 
without departing from the scope of the invention. Further, various 
changes may be made to the shape of the main and bypass housing(s), and to 
the type of gate used to block the main passage, without departing from 
the scope of the invention. The invention also should not be limited to 
application in aftermarket exhaust restriction devices. Thus, it is 
intended that the present invention cover the modifications and variations 
of the invention provided they come within the scope of the appended 
claims and their equivalents.