CA2012844A1 - Method of and an apparatus for regenerating a diesel particulate exhaust filter - Google Patents
Method of and an apparatus for regenerating a diesel particulate exhaust filterInfo
- Publication number
- CA2012844A1 CA2012844A1 CA 2012844 CA2012844A CA2012844A1 CA 2012844 A1 CA2012844 A1 CA 2012844A1 CA 2012844 CA2012844 CA 2012844 CA 2012844 A CA2012844 A CA 2012844A CA 2012844 A1 CA2012844 A1 CA 2012844A1
- Authority
- CA
- Canada
- Prior art keywords
- exhaust
- diesel
- filter
- upstream
- diesel filter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- Y02T10/47—
Landscapes
- Processes For Solid Components From Exhaust (AREA)
Abstract
ABSTRACT
A Method Of And An Apparatus For Regenerating A
Diesel Particulate Exhaust Filter A method of and an apparatus for regenerating a diesel filter (1) mounted in the exhaust pipe (3) of a diesel engine (2) are characterized in that, for initiating re-generation, the exhaust flow is throttled in the exhaust pipe (3) and/or in an exhaust feedback passage (7) by means of a control unit (10) responsive to setpoint exhaust tem-peratures measured upstream and downstream of the diesel filter (1) in the exhaust pipe (3), and that the air ratio is set to a value between 1.2 and 1.3 to inhibit regener-ation.
A Method Of And An Apparatus For Regenerating A
Diesel Particulate Exhaust Filter A method of and an apparatus for regenerating a diesel filter (1) mounted in the exhaust pipe (3) of a diesel engine (2) are characterized in that, for initiating re-generation, the exhaust flow is throttled in the exhaust pipe (3) and/or in an exhaust feedback passage (7) by means of a control unit (10) responsive to setpoint exhaust tem-peratures measured upstream and downstream of the diesel filter (1) in the exhaust pipe (3), and that the air ratio is set to a value between 1.2 and 1.3 to inhibit regener-ation.
Description
~ t" f~
A Method Of And An Apparatus For Regenerating A
Diesel Particulate Exhaust Filter The invention is directed to a method of and an a~naratus for regenerating a diesel particulate exhaust soot filter (briefly: diesel filter) mounted in the exhaust pipe of a diesel engine.
In a known method of the specified kind (EP 87 100 911.4~
the exhaust gas is throttled upstream of the diesel filter, as viewed in the direction of flow, so that the regener-ating temperature is either reached or exceeded. Then, the particulate deposited in the diesel filter is burnt off.
It is the object of the present invention to provide a method and an apparatus of the specified kind, in which fully automatic regeneration during operation of the diesel engine, on the one hand, and protection against uncon-trolled regeneration, i.e. against unintentional burning-off of the particulate deposited in the diesel filter, onthe other hand, can be achieved.
In accordance with the present invention the specified object is solved in that the actual temperatures of the exhaust gas upstream and downstream of the diesel filter are detected, that the regenerating operation is automatic-ally initiated when a first setpoint exhaust temperature is reached upstream of the diesel filter in operation of the diesel engine, that the regenerating operation is automa-tically turned off when a second setpoint exhaust tempera-ture upstream of the diesel filter is exceeded and that, when a predetermined exhaust temperature downstream of the (d ~
~ 2 diesel filter is exceeded, regeneration of the di~sel filter is inhibited by either setting the air ratio (lambda) to a setpoint within a range of more than 1, especially of 1.2 to 1.3, or temporarily cutting the diesel filter out of the exhaust stream by passing the exhaust through a bypass passage which bypasses the diesel filter.
Alternatively, an apparatus according to the present invention is characterized by a lambda probe for sensing the oxygen content in the exhaust gas, temperature sensors for sensing the actual exhaust temperatures in the exhaust pipe upstream and downstream of the diesel filter, and a control unit to which the measured actual exhaust tempera-tures and the setpoint exhaust temperatures are applied as inputs and which provides as outputs control signals for the throttle device, or by a bypass passage branching off from the exhaust pipe upstream of the diesel filter, as viewed in the direction of exhaust flow, and bypassing the diesel filter, with a check valve disposed in said bypass passage, temperature sensors for measuring the actual exhaust temperature in the exhaust pipe upstream and down-stream of the diesel filter, and a control unit to which the measured actual exhaust temperatures and the setpoint exhaust temperatures are applied as inputs and which pro-26 vides as outputs control signals for the throttle deviceand the check valve to open said check valve and to close the throttle device for inhibiting regeneration.
The present invention is based on the following findings:
Experiments have shown that combustion of the air-fuel mixture in the diesel engine at an air ratio of lambda = 1.2 to 1.3 leads to a residual oxygen content of 5% to 7%
in the exhaust gas. The inventor has found that, when the air ratio is maintained at a lambda value as specified, uncontrolled burning-off of the particulate deposited on , ~ the diesel filter can no longer happen. It becomes possible '.' !
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A Method Of And An Apparatus For Regenerating A
Diesel Particulate Exhaust Filter The invention is directed to a method of and an a~naratus for regenerating a diesel particulate exhaust soot filter (briefly: diesel filter) mounted in the exhaust pipe of a diesel engine.
In a known method of the specified kind (EP 87 100 911.4~
the exhaust gas is throttled upstream of the diesel filter, as viewed in the direction of flow, so that the regener-ating temperature is either reached or exceeded. Then, the particulate deposited in the diesel filter is burnt off.
It is the object of the present invention to provide a method and an apparatus of the specified kind, in which fully automatic regeneration during operation of the diesel engine, on the one hand, and protection against uncon-trolled regeneration, i.e. against unintentional burning-off of the particulate deposited in the diesel filter, onthe other hand, can be achieved.
In accordance with the present invention the specified object is solved in that the actual temperatures of the exhaust gas upstream and downstream of the diesel filter are detected, that the regenerating operation is automatic-ally initiated when a first setpoint exhaust temperature is reached upstream of the diesel filter in operation of the diesel engine, that the regenerating operation is automa-tically turned off when a second setpoint exhaust tempera-ture upstream of the diesel filter is exceeded and that, when a predetermined exhaust temperature downstream of the (d ~
~ 2 diesel filter is exceeded, regeneration of the di~sel filter is inhibited by either setting the air ratio (lambda) to a setpoint within a range of more than 1, especially of 1.2 to 1.3, or temporarily cutting the diesel filter out of the exhaust stream by passing the exhaust through a bypass passage which bypasses the diesel filter.
Alternatively, an apparatus according to the present invention is characterized by a lambda probe for sensing the oxygen content in the exhaust gas, temperature sensors for sensing the actual exhaust temperatures in the exhaust pipe upstream and downstream of the diesel filter, and a control unit to which the measured actual exhaust tempera-tures and the setpoint exhaust temperatures are applied as inputs and which provides as outputs control signals for the throttle device, or by a bypass passage branching off from the exhaust pipe upstream of the diesel filter, as viewed in the direction of exhaust flow, and bypassing the diesel filter, with a check valve disposed in said bypass passage, temperature sensors for measuring the actual exhaust temperature in the exhaust pipe upstream and down-stream of the diesel filter, and a control unit to which the measured actual exhaust temperatures and the setpoint exhaust temperatures are applied as inputs and which pro-26 vides as outputs control signals for the throttle deviceand the check valve to open said check valve and to close the throttle device for inhibiting regeneration.
The present invention is based on the following findings:
Experiments have shown that combustion of the air-fuel mixture in the diesel engine at an air ratio of lambda = 1.2 to 1.3 leads to a residual oxygen content of 5% to 7%
in the exhaust gas. The inventor has found that, when the air ratio is maintained at a lambda value as specified, uncontrolled burning-off of the particulate deposited on , ~ the diesel filter can no longer happen. It becomes possible '.' !
. , ' ~
',"
:, ~
,,~ ,.",""_ ., : :
' ' :
', ~ ' :
`
~` , ` .
;.
2 ~, 1,~`, !' /1.
to throttle the exhaust ~low in a controlled way in the exhaust pipe main stream and/or in an exhaust feedback flow so that controlled regeneration, i.e. burning-off of par-ticulate, in the diesel filter is achieved.
Alternatively, when critical temperature values are reachedthe exhaust flow automatically bypasses the diesel filter so that the latter is protected against uncontrolled burning-off.
The setpoint exhaust temperatures specified in claim 1 are advantaqeously varied in response to the pressure drop in the exhaust pressure across the diesel filter in accordance with prescribed functions.
Below, an embodiment of the invention will be described in detail with reference to schematic drawings, in which:
Fi~. 1 is a schematic view of an apparatus for regener-ating a diesel particulate exhaust filter in accordance with the invention, Fig. 2 is a diagram in which the setpoint exhaust tem-peratures are plotted versus the drop in the exhaust flow pressure across the diesel filter, and Fig. 3 is a modification of an apparatus according to the invention.
Fig. I illustrates schematically the fully automatic regeneration of a particulate exhaust filter 1 for a diesel engine 2, the diesel filter 1 being mounted in an exhaust pipe 3. A variable throttle device 4 is mounted in the exhaust pipe 3 intermediate the diesel filter 1 and the diesel enqine 2. The necessary air for combustion is supplied to the diesel engine 2 through an intake pipe S.
~_~ 4 A second variable throttle device 6 is mounted in an exhaust feedback passaqe 7 branching off the exhaust pipe 3 between the diesel engine 2 and the first throttle device 4 and terminating in the intake pipe 6.
Temperature sensors 8, 9 are mounted in the exhaust pipe 3 upstream and downstream of the diesel filter 1 for measuring the temperatures T~ and Th in the exhaust pipe 3 and providing said temperatures as inputs to a control unit 10. Also, a lambda probe 11 is mounted in the exhaust pipe downstream of the diesel filter 1 for measuring the oxygen content of the exhaust, the output signal of said probe being also provided as an input to the control unit 10. The measured oxygen content is a criterion for the air ratio.
Finally, a differential pressure sensor indicated at 12 is used to measure the pressure drop ~p across the diesel soot filter. The output signal from the differential pressure sensor 12 is provided as input to a functional module 13 in which setpoint exhaust temperatures are determined, viz. a minimum exhaust temperature Tlmin for automatically initiating a regeneration of the diesel filter 1 when said temperature is reached in operation of the diesel engine 2, a setpoint exhaust temperature TlmaX upstream of the diesel filter for automatically turning the reqeneration off when said temperature is exceeded, and a setpoint exha~st tem-perature ThmaX downstream of the diesel filter 1 for auto-matically inhibiting regeneration of the diesel filter when said temperature is exceeded. The specified setpoint tem-peratures are varied in the functional module 13 in accordance with prescribed functions for the specified temperatures in response to the variation of the pressure drop ~p across the diesel filter 1. Fig. 2 illustrates examples of such functions with a linear characteristic.
,, The control operation performed in the control unit 10 results in control signals which are supplied via control signal lines 14, 16 either selectively or jointly to both .
r~ J' ,~, f;J~ '~'J l.'3A 1.
S
throttle devices ~, ~ to thereby cause controlled regener-ation or the ~esired protection from uncontrolled regener-ation of the diesel filter 1, respectively.
The control operation is simplified due to the fact that the pressure drop ~p need not be measured inside a speci-fic rotational speed window in operation of the diesel engine 2. In other words, the value Qp measured by means of the differential pressure sensor 12 is an instantaneous value measured at the respective operating condition of the diesel engine.
The examples of functions illustrated in Fig. 2 are linear.
lmin f3 ( ~P) has a larger relative inclination than the two other functions so as to adapt the regenerating operation to the frequent vehicle operation in "crawling n traffic.
The criterion for decreasing TlmaX and ThmaX resides in keeping the maximum wall temperature of the ceramic diesel filter approximately constant during regeneration, because this maximum wall temperature increases with increasing load on the diesel filter.
26 A coarser although considerably simpler control can be achieved by assuming that the setpoint exhaust temperatures ThmaX and TlmaX are constant, i.e., they are not varied with the pressure drop ~. and by varying Tlmin step-wise with the pressure drop.
In Fig. 3 the same or similar parts are indicated by the same reference numerals and will not be described again. A
lambda probe and exhaust feedback are not provided herein.
Instead, a bypass passage 20 having a check valve 21 mounted therein branches off the exhaust pipe 3 downstream of the diesel engine. This check valve, which alternatively - realizes only an open-closed position, is actuated to the '' ~ ~sJJ' ~
open state by the control unit via the giqnal flow line 22 while the throttle device 4 is simultaneously closed when-ever ThmaX downstream of the diesel filter 1 is exceeded, so that the diesel filter is automatically cut out of the exhaust gas flow and is thereby protected against uncon-trolled burning-off. Inversely, in the normal case and for regenerating the diesel filter the check valve 21 is auto-matically kept closed while the throttle device 4 is kept open. For the rest, the control operation is the same as that explained with reference to Figs. 1 and 2.
..... .
to throttle the exhaust ~low in a controlled way in the exhaust pipe main stream and/or in an exhaust feedback flow so that controlled regeneration, i.e. burning-off of par-ticulate, in the diesel filter is achieved.
Alternatively, when critical temperature values are reachedthe exhaust flow automatically bypasses the diesel filter so that the latter is protected against uncontrolled burning-off.
The setpoint exhaust temperatures specified in claim 1 are advantaqeously varied in response to the pressure drop in the exhaust pressure across the diesel filter in accordance with prescribed functions.
Below, an embodiment of the invention will be described in detail with reference to schematic drawings, in which:
Fi~. 1 is a schematic view of an apparatus for regener-ating a diesel particulate exhaust filter in accordance with the invention, Fig. 2 is a diagram in which the setpoint exhaust tem-peratures are plotted versus the drop in the exhaust flow pressure across the diesel filter, and Fig. 3 is a modification of an apparatus according to the invention.
Fig. I illustrates schematically the fully automatic regeneration of a particulate exhaust filter 1 for a diesel engine 2, the diesel filter 1 being mounted in an exhaust pipe 3. A variable throttle device 4 is mounted in the exhaust pipe 3 intermediate the diesel filter 1 and the diesel enqine 2. The necessary air for combustion is supplied to the diesel engine 2 through an intake pipe S.
~_~ 4 A second variable throttle device 6 is mounted in an exhaust feedback passaqe 7 branching off the exhaust pipe 3 between the diesel engine 2 and the first throttle device 4 and terminating in the intake pipe 6.
Temperature sensors 8, 9 are mounted in the exhaust pipe 3 upstream and downstream of the diesel filter 1 for measuring the temperatures T~ and Th in the exhaust pipe 3 and providing said temperatures as inputs to a control unit 10. Also, a lambda probe 11 is mounted in the exhaust pipe downstream of the diesel filter 1 for measuring the oxygen content of the exhaust, the output signal of said probe being also provided as an input to the control unit 10. The measured oxygen content is a criterion for the air ratio.
Finally, a differential pressure sensor indicated at 12 is used to measure the pressure drop ~p across the diesel soot filter. The output signal from the differential pressure sensor 12 is provided as input to a functional module 13 in which setpoint exhaust temperatures are determined, viz. a minimum exhaust temperature Tlmin for automatically initiating a regeneration of the diesel filter 1 when said temperature is reached in operation of the diesel engine 2, a setpoint exhaust temperature TlmaX upstream of the diesel filter for automatically turning the reqeneration off when said temperature is exceeded, and a setpoint exha~st tem-perature ThmaX downstream of the diesel filter 1 for auto-matically inhibiting regeneration of the diesel filter when said temperature is exceeded. The specified setpoint tem-peratures are varied in the functional module 13 in accordance with prescribed functions for the specified temperatures in response to the variation of the pressure drop ~p across the diesel filter 1. Fig. 2 illustrates examples of such functions with a linear characteristic.
,, The control operation performed in the control unit 10 results in control signals which are supplied via control signal lines 14, 16 either selectively or jointly to both .
r~ J' ,~, f;J~ '~'J l.'3A 1.
S
throttle devices ~, ~ to thereby cause controlled regener-ation or the ~esired protection from uncontrolled regener-ation of the diesel filter 1, respectively.
The control operation is simplified due to the fact that the pressure drop ~p need not be measured inside a speci-fic rotational speed window in operation of the diesel engine 2. In other words, the value Qp measured by means of the differential pressure sensor 12 is an instantaneous value measured at the respective operating condition of the diesel engine.
The examples of functions illustrated in Fig. 2 are linear.
lmin f3 ( ~P) has a larger relative inclination than the two other functions so as to adapt the regenerating operation to the frequent vehicle operation in "crawling n traffic.
The criterion for decreasing TlmaX and ThmaX resides in keeping the maximum wall temperature of the ceramic diesel filter approximately constant during regeneration, because this maximum wall temperature increases with increasing load on the diesel filter.
26 A coarser although considerably simpler control can be achieved by assuming that the setpoint exhaust temperatures ThmaX and TlmaX are constant, i.e., they are not varied with the pressure drop ~. and by varying Tlmin step-wise with the pressure drop.
In Fig. 3 the same or similar parts are indicated by the same reference numerals and will not be described again. A
lambda probe and exhaust feedback are not provided herein.
Instead, a bypass passage 20 having a check valve 21 mounted therein branches off the exhaust pipe 3 downstream of the diesel engine. This check valve, which alternatively - realizes only an open-closed position, is actuated to the '' ~ ~sJJ' ~
open state by the control unit via the giqnal flow line 22 while the throttle device 4 is simultaneously closed when-ever ThmaX downstream of the diesel filter 1 is exceeded, so that the diesel filter is automatically cut out of the exhaust gas flow and is thereby protected against uncon-trolled burning-off. Inversely, in the normal case and for regenerating the diesel filter the check valve 21 is auto-matically kept closed while the throttle device 4 is kept open. For the rest, the control operation is the same as that explained with reference to Figs. 1 and 2.
..... .
Claims (9)
1. A method of regenerating a diesel particulate exhaust soot filter mounted in the exhaust pipe of a diesel engine, the exhaust being throttled upstream of the diesel filter, as viewed in flow direction, so that the re-generating temperature is either reached or exceeded, characterized in that the actual exhaust temperatures (T1 and Th) upstream and downstream of the diesel filter (1) are measured, that the regeneration is automatically initiated when a first setpoint exhaust temperature (T1min) is reached upstream of the diesel filter in operation of the diesel engine, that the regeneration is automatically turned off when a second setpoint exhaust temperature (T1max) upstream of the diesel filter is exceeded, and that, when a predetermined exhaust temperature (Thmax) downstream of the diesel filter is exceeded, regenera-tion of the diesel filter is inhibited by setting the air ratio (lambda) to a setpoint within a range of more than 1, especially of 1.2 to 1.3.
2. The method as claimed in claim 1, characterized in that the air ratio is adjusted by controlled throttling of the exhaust in the exhaust pipe main stream upstream of the diesel filter and is verified by measuring the oxygen content in the exhaust.
3. The method as claimed in claim 1 or claim 2, character-ized in that the air ratio is adjusted to the setpoint by controlled throttling of an exhaust feedback flow and is verified by meausuring the oxygen content in the exhaust.
4. A method of regenerating a diesel particulate exhaust soot filter mounted in the exhaust pipe of a diesel engine, the exhaust being throttled upstream of the diesel filter, as viewed in flow direction, so that the re-generating temperature is either reached or exceeded, characterized in that the actual exhaust temperatures (T1 and Th) upstream and downstream of the diesel filter (1) are measured, that the regeneration is automatically initiated when a first setpoint exhaust temperature (Tlmin) is reached upstream of the diesel filter in operation of the diesel engine, that the regeneration is automatically turned off when a second setpoint exhaust temperature (T1maX) upstream of the diesel filter is exceeded, and that, when a predetermined exhaust temperature (Thmax) downstream of the diesel filter is exceeded, regenera-tion of the diesel filter (1) is inhibited by temporari-ly cutting the diesel filter out of the exhaust stream by passing the exhaust through a bypass passage (20) which bypasses the diesel filter.
5. The method as claimed in any one of the claims 1 to 4, characterized in that the setpoint exhaust temperatures (T1min' T1max' Thmax) are varied in response to the pressure drop (.DELTA.p) across the diesel filter.
6. An apparatus for regenerating a diesel particulate exhaust soot filter mounted in the exhaust pipe of a diesel engine, in which a variable throttle device (4) is disposed in the exhaust pipe upstream of the diesel filter (1), as viewed in flow direction, characterized by a lambda probe (11) for measuring the oxygen content in the exhaust, by temperature sensors (8, 9) for measuring the actual exhaust temperatures (Tl, Th) in the exhaust pipe (3) upstream and downstream of the diesel filter (1), and by a control unit (10) to which the measured actual exhaust temperatures (T1, Th) and the setpoint exhaust temperatures (T1min, T1max, Thmax) are applied as inputs and which provides as outputs control signals for the throttle device (4).
7. An apparatus for regenerating a diesel particulate exhaust soot filter mounted in the exhaust pipe of a diesel enqine, in which a variable throttle device (4) is dis-posed in the exhaust pipe upstream of the diesel filter (1), as viewed in flow direction, characterized by a bypass passage (20) branching off from the exhaust nipe (3) upstream of the throttle device (4), as viewed in flow direction, and bypassing the diesel filter (1), with a check valve (21) disposed in said bypass passage, by temperature sensors (8, 9) for measuring the actual exhaust temperature (T1, Th) in the exhaust pipe (3) upstream and downstream of the diesel filter (l), and by a control unit (10) to which the measured actual exhaust temperatures (T1, Th) and setpoint exhaust temperatures (T1min, T1max, Thmax) are applied as inputs and which provides as outputs control signals for the throttle device (4) and the check valve (21) to open said check valve and to block the throttle device (4) to thereby inhibit regeneration of the diesel filter (1).
8. The apparatus as claimed in claim 6 or claim 7, charac-terized in that a differential pressure sensor (12) is provided for measuring the pressure drop ( .DELTA.P) in the exhaust across the diesel filter (1), the output signal from said sensor being inputted to a functional module (13) for varying the setpoint exhaust temperatures in accordance with prescribed functions.
9. The apparatus as claimed in claim 6, characterized in that exhaust feedback means (7) is provided including a further variable throttle device (6), and that the control unit (10) provides control signals for actuating said further throttle device (6) either additionally or alone.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2012844 CA2012844A1 (en) | 1990-03-22 | 1990-03-22 | Method of and an apparatus for regenerating a diesel particulate exhaust filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2012844 CA2012844A1 (en) | 1990-03-22 | 1990-03-22 | Method of and an apparatus for regenerating a diesel particulate exhaust filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2012844A1 true CA2012844A1 (en) | 1991-09-22 |
Family
ID=4144575
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2012844 Abandoned CA2012844A1 (en) | 1990-03-22 | 1990-03-22 | Method of and an apparatus for regenerating a diesel particulate exhaust filter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2012844A1 (en) |
-
1990
- 1990-03-22 CA CA 2012844 patent/CA2012844A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |