Diesel engine exhaust particulate filter with intake throttling incineration control

Diesel exhaust filter and incineration control systems are disclosed which provide intake throttling of the diesel engine as a primary means of raising exhaust temperature in the filter for the periodic burn-off of collected particulates. Various embodiments and supplemental means of increasing exhaust temperatures are also disclosed.

Technical Field 
This invention relates to diesel engine exhaust gas treatment, in 
particular to the filtering of particulates from diesel engine exhaust 
gases and, more specifically, to the periodic incineration of collected 
particulates in the filter through temporarily increasing exhaust gas 
temperature with a system including throttling of the engine air intake. 
BACKGROUND OF THE INVENTION 
It is known in the art to provide a diesel engine with exhaust filter means 
comprising a particulate trap to collect particulates from the exhaust gas 
stream during the engine operation. Such particulates consist largely of 
carbon particles which, with continued operation, tend to plug the exhaust 
filter, causing a restriction to normal exhaust gas flow. Such a 
restriction may be avoided by periodically cleaning the particulates from 
the exhaust gas filter. 
The cleaning of particulates from an exhaust filter may be accomplished by 
any practical method. One suggested method is incineration in place, 
brought about by increasing the engine exhaust gas temperature to the 
combustion temperature of the collected particulates. This may be 
accomplished, for example, by heating the exhaust gas stream in the manner 
disclosed in the co-pending United States patent application Ser. No. 
872,360 filed Jan. 26, 1978, now U.S. Pat. No. 4,167,852, in the name of 
Otto A. Ludecke and assigned to the assignee of the present invention. 
Under some circumstances, the normal operating temperature of the diesel 
engine exhaust gases may be sufficiently high to incinerate collected 
particulates in an appropriately located exhaust filter. For example, U.S. 
Pat. No. 3,937,015 Adako et al discloses a particular construction of 
exhaust manifold mounted filter which, it is asserted, will be cleaned by 
the burning of collected carbon particles caused by high exhaust gas 
temperatures reached during heavy load operation of the engine. However, 
such a system does not provide control of the frequency or extent of the 
burn periods nor of the maximum temperatures reached which, if these are 
excessive, may shorten the life of or permanently damage the exhaust 
filter element. 
Also, in some engine applications, particularly those for use in lighter 
automotive vehicles, operation under heavy load may rarely occur. In this 
case, the engine exhaust temperatures may not be sufficient to burn off 
collected particulates at the time such action is desirable. For example, 
in a currently produced automotive diesel engine operated in simulated 
city driving conditions at 25 miles per hour road load, the exhaust 
manifold temperature was measured at only 360.degree. F., which is far 
below the temperature of approximately 900.degree. F. required to 
incinerate trapped particulates from a filter device in the exhaust. Thus, 
in order to adequately control the periods and temperatures of 
incineration, we consider it desirable to provide controllable means for 
increasing the exhaust gas temperature to accomplish the desired periodic 
burn off of particulates. 
SUMMARY OF THE INVENTION 
We have found that a substantial increase in the exhaust gas temperature of 
a diesel engine may be obtained by partially throttling the engine air 
intake, thus reducing the excess air passing through the engine. Since 
diesel engines normally run unthrottled, load control is generally 
accomplished by varying the fuel input to the engine, without a like 
variation in the amount of air flow. In addition, the combustion 
characteristics of fuel injected engine cylinders require for proper 
combustion that a certain amount of air in excess of the stoichiometric 
requirements be supplied to the engine under all operating conditions. 
Accordingly, reduction of the engine load from the full fuel operating 
condition results in a substantial increase of the amount of excess air 
which passes through the engine, resulting in much lower exhaust gas 
temperatures than are normally found in comparable gasoline engines. 
The present invention provides intake throttling means as a main element of 
an exhaust filter particulate incineration control system provided to 
periodically burn off collected particulates from an exhaust filter. While 
the intake throttle is utilized as a primary method of increasing exhaust 
temperature, other means may also be included to provide additional 
increases in exhaust temperature where necessary. Such means may include 
for example heating devices in the engine exhaust system or devices to 
modify operation of the engine by cutting out cylinders, retarding timing, 
providing excess fuel or any combination of these and other features 
needed to accomplish the desired purposes. By properly combining such 
features in an overall control system, it is possible to provide 
controlled incineration of particulates at predetermined desirable 
intervals and to control the incineration temperatures to avoid impairing 
the life of the exhaust filter. 
These and other features and advantages of the invention will be more fully 
understood from the following description of certain preferred 
embodiments, taken together with the accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawings in detail, FIG. 1 illustrates a preferred 
embodiment of the invention as installed in an automotive vehicle 
generally indicated by numeral 10. Vehicle 10 is driven in conventional 
fashion by a diesel engine 12 having an air induction system including an 
air cleaner 14 and a combustion products exhaust system including an 
exhaust manifold 16 connecting with individual exhaust ports in the side 
of an engine cylinder head 18. The exhaust manifold connects with an 
exhaust pipe 20 in which there is mounted a particulate trap 22 containing 
at least one filter element 24 through which the exhaust gases from the 
engine are required to pass. 
The filter element or elements 24 may be made of any suitable material and 
configuration capable of trapping and holding substantial quantities of 
particulates from the engine exhaust gases without creating an excessive 
restriction to exhaust gas flow and able to withstand the elevated 
temperatures to be reached in the subsequent incineration of particulates 
during engine operation. Examples of materials which may be suitable for 
such a purpose are ceramic beads, monolithic ceramic structures, metal 
wire mesh or multiple screen elements such as of stainless steel; however, 
any other suitable materials and structures may also be utilized. At 
present we prefer to utilize alumina coated stainless steel wire packed 
into a container to form the desired filter material. The alumina material 
may be of the type disclosed in U.S. Pat. No. 3,231,520 to Leak and Le 
Bleu except that the catalytic coating referred to in the patent is not 
applied to the wire. 
In order to provide for periodic removal of particulates from the 
particulate trap 22 by incineration, the vehicle 10 is provided with a 
particulate incineration control system including throttling means on the 
engine air intake. In the present case, to provide a finer degree of 
control and for test purposes, the air cleaner 14 is provided with a 
conventional main air inlet tube 26 and a second smaller auxiliary air 
inlet tube 28. Inlet tube 26 is further provided with a main throttle 
valve and control servo motor 30 which are controllable to open or close, 
in part or completely, the main inlet to the flow of intake air. In like 
manner, the auxiliary inlet 28 is provided with a smaller vernier throttle 
and servo motor control 32 which are operable to open or controllably 
close the auxiliary inlet 28 to the passage of intake air. 
Experience has shown that in normal engine operation the temperature in the 
exhaust system varies substantially under different conditions of engine 
load and speed and that, depending upon the position of the particulate 
trap in the exhaust system, temperatures in the trap may never reach the 
level required to burn off the particulates collected therein. This is 
especially true if the engine is seldom operated under full throttle, as 
is typical of many automotive vehicle applications, or if the particulate 
trap is mounted externally of the engine exhaust manifold, as is the case 
in the arrangement shown in FIG. 1 of the drawings. Thus, it is necessary, 
in order to periodically incinerate the collected particulates, to provide 
some other means for raising the exhaust temperature to the necessary 
level of about 900.degree. F. 
A number of possible methods may be used singly or in combination in order 
to obtain the desired temperature levels. One such method which may be 
used under all engine operating conditions, except the full fuel or full 
load condition, is throttling of the engine air intake system. We have 
found that appropriate throttling of the air intake is capable of 
increasing substantially the engine exhaust temperature and may in some 
cases be sufficient to raise the temperature in the particulate trap to 
the incineration level. 
This method is utilized in the system disclosed in FIG. 1 of the drawings. 
Here, the main and vernier throttle servo motors are controlled by means 
of a microcomputer control 34 having inputs connected with the diesel 
engine fuel rack position 36, an engine speed sensor 38, an engine exhaust 
temperature sensor 40 and a particulate trap bed temperature sensor 42, 
which inputs are processed by the microcomputer to control the position of 
the throttles in an appropriate manner. The design criteria of this system 
include the following: 
1. The trap must be cleaned out often enough so that the collected 
particulates do not cause an excessive restriction to exhaust gas flow. 
2. The throttling of the engine intake must be controlled so as not to 
change significantly the driveability or performance of the vehicle. 
3. The controlling process should not cause a significant or noticeable 
increase in smoke emanating from the vehicle exhaust pipe. 
4. The burn cycle should be controlled so that only the particulates are 
incinerated and the bed of the trap is not damaged. 
In order to accomplish these purposes, the microcomputer of the present 
invention is programmed to operate in the following manner: 
1. A periodic burn cycle is programmed to begin 150,000 engine revolutions 
after completion of the previous burn. This is approximately equivalent to 
50 kilometers of vehicle travel, and since it should take about 500 
kilometers of driving for the trap to become overloaded, the 50 kilometer 
cleaning interval appears adequate. 
2. Since throttling the intake air to the engine decreases the potential 
power output, the program includes an override in the system that opens 
all the throttles during a burn cycle, if the driver advances the fuel 
control to the full rack position. As the driver eases up on the rack, the 
burn cycle is continued. Also, it is recognized that the maximum limit to 
which the engine can be throttled without adversely effecting driveability 
varies with both speed and load. Since these conditions are likely to be 
changing constantly during any burn cycle, the computer program constantly 
updates its information as to the speed and load of the engine in order to 
correct the position of the throttles as required. 
3. It has also been found experimentally that throttling of the engine air 
intake must be limited to avoid creation of excessive exhaust smoke and 
that the limit on the amount of throttling varies with the engine speed 
and load. In order to program the computer for a particular engine, the 
smoke creating conditions for throttling at various speeds and loads must 
be experimentally determined. The resulting three dimensional curve is 
then programmed into the computer which then controls the throttles as a 
function of engine speed and rack position so that the creation of 
excessive smoke is avoided. 
4. To prevent the trap bed from being damaged while particulates are being 
burned, the computer is further programmed to adjust the throttles to 
control the rise in temperature in the particulate trap bed to a 
reasonable rate, to maintain the bed temperature during the burn between 
950.degree. and 1,000.degree. F. and to cancel the burn immediately if the 
bed temperature exceeds 1,200.degree. F., which is still some 300.degree. 
below the temperature at which the bed itself will burn. If the bed 
temperature should reach 1,500.degree. F., the computer is programmed to 
initiate a signal indicating that the trap has been damaged. 
FIG. 2 comprises a flow diagram of the operation of the control system as 
pre-established by the programming of the microcomputer, the operation of 
which is self-explanatory to those knowledgeable in the art. 
Referring now to FIGS. 3a and 3b of the drawings, there is shown an 
alternative embodiment of diesel particulate filter and incineration 
system as applied to an in-line four cylinder engine generally indicated 
by numeral 50. Engine 50 includes an intake manifold 52 having an inlet 
pipe 54 with a throttle 56 controlled by any suitable means, not shown. 
The engine is also provided with an exhaust manifold 58 defining an 
internal chamber 60 containing a particulate filter element 62. The 
manifold includes individual inlet legs 64 leading from the four engine 
exhaust ports to the interior of the manifold 58 where the gas is 
conducted via a passage 66 to the filter element 62 and thence to an 
outlet pipe 68. A heating grid 70, which may be electrically operated, is 
provided at the inlet to the filter element to provide supplemental heat 
to the system when required. 
The outlet pipe 68 connects with an EGR passage 72 by means of which 
cleaned exhaust gases may be recirculated to the intake manifold 52. An 
additional trapping element 74 may be provided in the EGR passage, if 
desired, and flow through the passage is controlled by an EGR valve 76. 
The system is also provided with a particulate trap bypass line 78 which 
extends from the inlet passage 66 of the manifold to the outlet pipe 68. A 
bypass valve 80 is provided in the bypass line to control the flow of 
exhaust gases around the filter. 
Control of this system may be provided by any suitable means such as for 
example the microcomputer of the arrangement disclosed in FIG. 1. The 
control inputs include the position of the inlet throttle 56 as well as 
exhaust back pressure indicated by a sensor 82 in the exhaust manifold and 
the particulate filter temperature as indicated by a sensor 84 embedded 
within the filter element. 
In operation, a burn off of particulates collected in the exhaust filter is 
initiated by suitable automatic or manual control means. These close the 
intake throttle as necessary to increase the temperature in the manifold 
filter to the combustion temperature of the particulates. The temperature 
sensor indicates the temperature reached, which may be displayed on a 
visual indicator viewable by the operator or fed into an automatic control 
unit that controls the amount of throttling in the manner described for 
the system of FIG. 1. The bypass line and control valve may be utilized to 
permit exhaust gas flow to bypass the filter element under conditions such 
as full throttle where the restriction to flow through the filter may 
otherwise limit engine horsepower to some extent. The EGR line is provided 
for use in controlling emissions of oxides of nitrogen in known manner 
with the supplemental trapping element 74 provided to reduce the 
possibility of recycling particulates through the engine. 
Referring now to FIG. 4 of the drawings, there is shown another embodiment 
of the invention with a V-type eight cylinder diesel engine generally 
indicated by numeral 86. Engine 86 has two banks 88, 90 of cylinders with 
individual solenoid controlled injectors 92 and an intake manifold 94 
supplying air to the cylinders of both banks and incorporating separate 
intake throttles 96, 98, one for each cylinder bank. The cylinder banks 
are likewise provided with separate exhaust manifolds 100, 102, each of 
which incorporates an exhaust particulate trap, the manifolds being 
provided with outlet pipes connecting with a common exhaust line 104. 
In operation, suitable controls, not shown, are provided for controlling 
both the intake throttles and the injectors. In normal operation, the 
intake throttles would both be fully opened and the injectors would 
operate normally to provide equal amounts of fuel to all cylinders. 
However, when a periodic burn off of particulates in the particuate traps 
is desired, one of the throttles is closed and the injectors on the 
associated bank are shut off so that the engine then operates completely 
with power developed in the other active cylinder bank. The increased load 
on the four cylinders of the active bank raises the exhaust temperature in 
this bank a significant amount which may be sufficient to burn off the 
particulates in the trap located in the exhaust manifold of that cylinder 
bank. If this is not sufficient, the throttle of the active bank may be 
partially closed so as to limit air flow to that bank and further increase 
the exhaust temperature in the manner of the previously described 
embodiments. 
Additionally, if desired, any of the engine embodiments disclosed may be 
controlled in a manner whereby certain of the injectors are shut off to 
reduce the number of active cylinders driving the vehicle. This combined 
with throttling the air can increase the exhaust temperature without the 
need for a split cylinder arrangement as shown in the embodiment of FIG. 
4. Since these and other changes may be made within the spirit and scope 
of the inventive concepts disclosed, it is intended that the invention not 
be limited, except by the language of the following claims.