U.S. patent application number 13/997909 was filed with the patent office on 2013-10-31 for reducing agent supply apparatus abnormality diagnosis unit and reducing agent supply apparatus.
This patent application is currently assigned to Bosch Corporation. The applicant listed for this patent is Masayasu Nagata. Invention is credited to Masayasu Nagata.
Application Number | 20130283771 13/997909 |
Document ID | / |
Family ID | 46382680 |
Filed Date | 2013-10-31 |
United States Patent
Application |
20130283771 |
Kind Code |
A1 |
Nagata; Masayasu |
October 31, 2013 |
REDUCING AGENT SUPPLY APPARATUS ABNORMALITY DIAGNOSIS UNIT AND
REDUCING AGENT SUPPLY APPARATUS
Abstract
[Problem] To provide a reducing agent supply apparatus
abnormality diagnosis unit that can reduce the limitation on when
to perform abnormality diagnosis and on the applicability of
abnormality diagnosis to facilitate the implementation of
abnormality diagnosis of a reducing agent supply apparatus and to
provide the reducing agent supply apparatus. [Means for Resolution]
The reducing agent supply apparatus abnormality diagnosis unit
includes: a reducing agent injection valve controller for
determining an energization on/off duty ratio according to an
instructed injection amount of the reducing agent to issue an
instruction for driving the reducing agent injection valve; a pump
controller for determining an energization on/off duty ratio to
issue an instruction for driving the pump so that the pressure in
the reducing agent passage is maintained at a predetermined system
pressure, based on the difference between the detected pressure in
the reducing agent passage and the system pressure; and an
abnormality determiner for performing abnormality determination of
the reducing agent supply apparatus based on the duty ratio of the
reducing agent injection valve and the duty ratio of the pump in a
predetermined period.
Inventors: |
Nagata; Masayasu; (Saitama,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nagata; Masayasu |
Saitama |
|
JP |
|
|
Assignee: |
Bosch Corporation
Tokyo
JP
|
Family ID: |
46382680 |
Appl. No.: |
13/997909 |
Filed: |
September 7, 2011 |
PCT Filed: |
September 7, 2011 |
PCT NO: |
PCT/JP2011/070321 |
371 Date: |
June 25, 2013 |
Current U.S.
Class: |
60/282 |
Current CPC
Class: |
F01N 3/2066 20130101;
F01N 2900/0418 20130101; F01N 2610/02 20130101; F01N 2610/146
20130101; Y02T 10/40 20130101; F01N 3/08 20130101; F01N 11/00
20130101; Y02T 10/12 20130101; F01N 2900/1806 20130101; Y02T 10/24
20130101; F01N 2900/1822 20130101; F01N 2610/144 20130101; F01N
2900/1808 20130101; F01N 2610/1433 20130101; F01N 2550/14 20130101;
F01N 2900/1821 20130101; Y02T 10/47 20130101; F01N 2900/0416
20130101; F01N 2550/05 20130101; F01N 2560/08 20130101 |
Class at
Publication: |
60/282 |
International
Class: |
F01N 3/08 20060101
F01N003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2010 |
JP |
2010-294095 |
Claims
1. A reducing agent supply apparatus abnormality diagnosis unit for
performing abnormality diagnosis of a reducing agent supply
apparatus, the reducing agent supply apparatus comprising: a
storage tank for storing liquid reducing agent; a pump for pumping
the reducing agent; a reducing agent injection valve for injecting
the reducing agent pumped by the pump in an exhaust pipe of an
internal-combustion engine; a reducing agent passage connecting the
pump to the reducing agent injection valve; and a pressure sensor
for detecting pressure in the reducing agent passage, wherein the
reducing agent supply apparatus abnormality diagnosis unit
comprises: a reducing agent injection valve controller for
determining an energization on/off duty ratio according to an
instructed injection amount of the reducing agent to issue an
instruction for driving the reducing agent injection valve; a pump
controller for determining an energization on/off duty ratio to
issue an instruction for driving the pump so that the pressure in
the reducing agent passage is maintained at a predetermined system
pressure, based on the difference between the detected pressure in
the reducing agent passage and the system pressure; and an
abnormality determiner for performing abnormality determination of
the reducing agent supply apparatus based on the duty ratio of the
reducing agent injection valve and the duty ratio of the pump in a
predetermined period.
2. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 1, wherein the abnormality determiner performs
the abnormality determination by determining whether or not the
instruction for driving the pump with an output power assumed from
the integration of the reducing agent injection valve duty ratio
during the predetermined period has been issued.
3. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 1, wherein the abnormality determiner performs
the abnormality determination based on the reducing agent injection
valve duty ratio and the pump duty ratio when the reducing agent
injection valve duty ratio is within a range in which the change in
the pump duty ratio is in proportion to the change in the reducing
agent injection valve duty ratio.
4. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 1, wherein the abnormality determiner performs
the abnormality determination such that the predetermined period is
a period from when the integration of the reducing agent injection
valve duty ratio is started to when the calculated integration
reaches a predetermined determination start value.
5. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 1, wherein the abnormality determiner performs
the abnormality determination by setting as a reference duty ratio
the pump duty ratio when the reducing agent injection valve duty
ratio is zero, then comparing the ratio of the integration of the
reducing agent injection valve duty ratio during the predetermined
period to the integration of the difference between the pump duty
ratio and the reference duty ratio during the predetermined period,
with a determination threshold.
6. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 1, wherein the abnormality determiner performs
the abnormality determination by setting as a reference duty ratio
the pump duty ratio when the reducing agent injection valve duty
ratio is zero, then comparing the integration of the product of the
reducing agent injection valve duty ratio and the difference
between the pump duty ratio and the reference duty ratio during the
predetermined period, with a determination threshold assumed from
the integration of the reducing agent injection valve duty ratio
during the predetermined period.
7. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 1, wherein the abnormality determiner performs
the abnormality determination by setting as a reference duty ratio
the pump duty ratio when the reducing agent injection valve duty
ratio is zero, then comparing the integration of the difference
between the pump duty ratio and the reference duty ratio during the
predetermined period, with a determination threshold assumed from
the integration of the reducing agent injection valve duty ratio
during the predetermined period.
8. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 1, wherein an upper threshold and a lower
threshold are set as a determination threshold, and the abnormality
determiner uses the upper threshold and the lower threshold to
separately determine an abnormality of excessive injection amount
condition and an abnormality of insufficient injection amount
condition.
9. A reducing agent supply apparatus comprising the reducing agent
supply apparatus abnormality diagnosis unit according to claim
1.
10. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 2, wherein the abnormality determiner performs
the abnormality determination based on the reducing agent injection
valve duty ratio and the pump duty ratio when the reducing agent
injection valve duty ratio is within a range in which the change in
the pump duty ratio is in proportion to the change in the reducing
agent injection valve duty ratio.
11. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 10, wherein the abnormality determiner performs
the abnormality determination such that the predetermined period is
a period from when the integration of the reducing agent injection
valve duty ratio is started to when the calculated integration
reaches a predetermined determination start value.
12. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 11, wherein the abnormality determiner performs
the abnormality determination by setting as a reference duty ratio
the pump duty ratio when the reducing agent injection valve duty
ratio is zero, then comparing the ratio of the integration of the
reducing agent injection valve duty ratio during the predetermined
period to the integration of the difference between the pump duty
ratio and the reference duty ratio during the predetermined period,
with a determination threshold.
13. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 12, wherein the abnormality determiner performs
the abnormality determination by setting as a reference duty ratio
the pump duty ratio when the reducing agent injection valve duty
ratio is zero, then comparing the integration of the product of the
reducing agent injection valve duty ratio and the difference
between the pump duty ratio and the reference duty ratio during the
predetermined period, with a determination threshold assumed from
the integration of the reducing agent injection valve duty ratio
during the predetermined period.
14. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 11, wherein the abnormality determiner performs
the abnormality determination by setting as a reference duty ratio
the pump duty ratio when the reducing agent injection valve duty
ratio is zero, then comparing the integration of the difference
between the pump duty ratio and the reference duty ratio during the
predetermined period, with a determination threshold assumed from
the integration of the reducing agent injection valve duty ratio
during the predetermined period.
15. The reducing agent supply apparatus abnormality diagnosis unit
according to claim 14, wherein an upper threshold and a lower
threshold are set as a determination threshold, and the abnormality
determiner uses the upper threshold and the lower threshold to
separately determine an abnormality of excessive injection amount
condition and an abnormality of insufficient injection amount
condition.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a reducing agent supply
apparatus abnormality diagnosis unit for performing abnormality
diagnosis of a reducing agent supply apparatus that injects in an
exhaust pipe reducing agent for purifying exhaust gas, and also
relates to a reducing agent supply apparatus including the
abnormality diagnosis unit.
[0002] Conventionally, as one aspect of an exhaust gas purification
apparatus for removing nitrogen oxides (hereinafter referred to as
"NOx") contained in exhaust gas from an internal-combustion engine
included in a vehicle or the like, an apparatus is practically used
which includes: an NOx purification catalyst, provided in the
middle of an exhaust passage, for speeding up reduction reaction
between NOx and reducing agent; and a reducing agent supply
apparatus that injects liquid reducing agent, such as urea aqueous
solution and unburnt fuel, upstream of the NOx purification
catalyst. The reducing agent supply apparatus used in such an
exhaust gas purification apparatus includes: a storage tank for
storing liquid reducing agent; a pump for sucking up and pumping
reducing agent stored in the storage tank; and a reducing agent
injection valve for injecting the pumped reducing agent in the
exhaust pipe.
[0003] In this configuration, when the injection amount of reducing
agent is too large with respect to the amount of NOx, reducing
agent components, such as ammonia and unburnt fuel component, flow
out to the downstream side of the NOx purification catalyst. On the
other hand, when the injection amount of reducing agent is too
small with respect to the amount of NOx, NOx purification rate
decreases to cause NOx to flow out to the downstream side of the
NOx purification catalyst. Thus, in order to inject just enough
reducing agent with respect to the amount of nitrogen oxides
contained in exhaust gas, the reducing agent supply apparatus is
configured to determine an instructed injection amount of reducing
agent based on the operating condition of the internal-combustion
engine to perform injection control.
[0004] In such a reducing agent supply apparatus, crystallization
of reducing agent, invasion of foreign material from the exhaust
pipe side into the reducing agent supply apparatus through an
injection nozzle of the reducing agent injection valve or the like
may cause a reducing agent passage and the injection nozzle
connecting the pump to the reducing agent injection valve to be
partially or completely blocked, causing the actual reducing agent
injection amount to be less than the instructed injection amount.
In order to solve this problem, an apparatus has been proposed that
is configured so as to determine clogging of a reducing agent
supply chain using the pressure value of reducing agent supplied to
the reducing agent injection valve. Specifically, an apparatus has
been disclosed that determines whether or not clogging has occurred
in the reducing agent supply chain based on the relation between
the amount of reducing agent injected with the pump stopped and the
amount of decrease in the pressure of reducing agent (see
JP-A-2008-2426).
SUMMARY OF INVENTION
[0005] However, the apparatus described in JP-A-2008-2426 needs to
stop the pump while performing abnormality diagnosis. So, in order
to perform abnormality diagnosis, the apparatus needs to interrupt
the usual injection control of reducing agent or needs to perform
abnormality diagnosis only when exhaust gas purification control is
not performed, which imposes a limitation on when to perform
abnormality diagnosis.
[0006] Furthermore, the reason of difference between the actual
reducing agent injection amount and the instructed injection amount
is not only the clogging of the reducing agent supply chain, but
may be deterioration or damage of a component of the reducing agent
supply apparatus, electrical failure or the like, so a diagnosis
method for reliably detecting the occurrence of abnormality as
described above is desired.
[0007] The present inventors found that the above-described problem
can be solved by performing abnormality diagnosis of the reducing
agent supply apparatus based on the duty ratio of the reducing
agent injection valve and the duty ratio of the pump while usual
injection control of reducing agent is being performed, and thus
completed the invention.
[0008] That is, it is an object of the present invention to provide
a reducing agent supply apparatus abnormality diagnosis unit that
can reduce the limitation on when to perform abnormality diagnosis
and can reliably detect an abnormality of a reducing agent supply
apparatus and to provide a reducing agent supply apparatus.
[0009] According to the invention, a reducing agent supply
apparatus abnormality diagnosis unit for performing abnormality
diagnosis of a reducing agent supply apparatus is provided, the
reducing agent supply apparatus including: a storage tank for
storing liquid reducing agent; a pump for pumping the reducing
agent; a reducing agent injection valve for injecting the reducing
agent pumped by the pump in an exhaust pipe of an
internal-combustion engine; a reducing agent passage connecting the
pump to the reducing agent injection valve; and a pressure sensor
for detecting pressure in the reducing agent passage, wherein the
reducing agent supply apparatus abnormality diagnosis unit
includes: a reducing agent injection valve controller for
determining an energization on/off duty ratio according to an
instructed injection amount of the reducing agent to issue an
instruction for driving the reducing agent injection valve; a pump
controller for determining an energization on/off duty ratio to
issue an instruction for driving the pump so that the pressure in
the reducing agent passage is maintained at a predetermined system
pressure, based on the difference between the detected pressure in
the reducing agent passage and the system pressure; and an
abnormality determiner for performing abnormality determination of
the reducing agent supply apparatus based on the duty ratio of the
reducing agent injection valve and the duty ratio of the pump in a
predetermined period. This reducing agent supply apparatus
abnormality diagnosis unit can solve the above-described
problem.
[0010] Specifically, when the pump is drive-controlled so that the
pressure in the reducing agent passage is maintained at a system
pressure, the reducing agent supply apparatus abnormality diagnosis
unit exploits the fact that there is a correlation between the
change in the reducing agent injection valve duty ratio and the
change in the pump duty ratio to perform abnormality diagnosis
based on the duty ratios. This eliminates the need for interrupting
usual reducing agent injection control and enables reliable
detection of an abnormality of the reducing agent supply
apparatus.
[0011] Furthermore, in configuring the reducing agent supply
apparatus abnormality diagnosis unit of the invention, the
abnormality determiner preferably performs abnormality
determination by determining whether or not the instruction for
driving the pump with an output power assumed from the integration
of the reducing agent injection valve duty ratio during the
predetermined period has been issued.
[0012] The reducing agent supply apparatus abnormality diagnosis
unit of the invention performs abnormality diagnosis using the
integration of the reducing agent injection valve duty ratio. So,
even when the sensitivity of the pump duty ratio to the reducing
agent injection valve duty ratio reduces temporarily, the
possibility of erroneous determination as a result of abnormality
diagnosis may be reduced.
[0013] Furthermore, in the reducing agent supply apparatus
abnormality diagnosis unit, the abnormality determiner preferably
performs abnormality determination based on the reducing agent
injection valve duty ratio and the pump duty ratio when the
reducing agent injection valve duty ratio is within a range in
which the change in the pump duty ratio is in proportion to the
change in the reducing agent injection valve duty ratio.
[0014] In the reducing agent supply apparatus abnormality diagnosis
unit of the invention, the range of the reducing agent injection
valve duty ratio and the pump duty ratio, based on which the
determination is performed, is limited to a predetermined range so
that abnormality diagnosis is performed based on the duty ratios
when the sensitivity of the pump duty ratio to the reducing agent
injection valve duty ratio is relatively stable, which can improve
the precision of the diagnosis.
[0015] Furthermore, in configuring the reducing agent supply
apparatus abnormality diagnosis unit of the invention, the
abnormality determiner preferably performs the abnormality
determination such that the predetermined period is a period from
when the integration of the reducing agent injection valve duty
ratio is started to when the calculated integration reaches a
predetermined determination start value.
[0016] In the reducing agent supply apparatus abnormality diagnosis
unit of the invention, abnormality diagnosis is performed based on
the reducing agent injection valve duty ratio and the pump duty
ratio in a period in which the integration of the reducing agent
injection valve duty ratio reaches a predetermined determination
start value so that abnormality diagnosis is performed when the
instructed injection amount is equal to or more than a
predetermined amount, which causes the variation depending on
whether or not an abnormality has occurred to be seen clearly,
allowing the possibility of erroneous determination to be
reduced.
[0017] Furthermore, in the reducing agent supply apparatus
abnormality diagnosis unit of the invention, the abnormality
determiner preferably performs abnormality determination by setting
as a reference duty ratio the pump duty ratio when the reducing
agent injection valve duty ratio is zero, then comparing the ratio
of the integration of the reducing agent injection valve duty ratio
during the predetermined period to the integration of the
difference between the pump duty ratio and the reference duty ratio
during the predetermined period, with a determination
threshold.
[0018] The reducing agent supply apparatus abnormality diagnosis
unit of the invention performs abnormality diagnosis using the
ratio of the integration of the reducing agent injection valve duty
ratio during the predetermined period to the integration of the
change in the pump duty ratio during the predetermined period,
which can facilitate the detection of a condition in which the
sensitivity of the pump duty ratio to the change in the reducing
agent injection valve duty ratio is abnormal, improving the
reliability of the diagnosis.
[0019] Furthermore, in configuring the reducing agent supply
apparatus abnormality diagnosis unit of the invention, the
abnormality determiner preferably performs abnormality
determination by setting as a reference duty ratio the pump duty
ratio when the reducing agent injection valve duty ratio is zero,
then comparing the integration of the product of the reducing agent
injection valve duty ratio and the difference between the pump duty
ratio and the reference duty ratio during the predetermined period,
with a determination threshold assumed from the integration of the
reducing agent injection valve duty ratio during the predetermined
period.
[0020] The reducing agent supply apparatus abnormality diagnosis
unit performs abnormality diagnosis using the integration of the
product of the reducing agent injection valve duty ratio during the
predetermined period and the change in the pump duty ratio, which
causes the variation depending on whether or not an abnormality has
occurred to be seen clearly, facilitating the determination whether
or not an abnormality has occurred.
[0021] Furthermore, in configuring the reducing agent supply
apparatus abnormality diagnosis unit of the invention, the
abnormality determiner preferably performs abnormality
determination by setting as a reference duty ratio the pump duty
ratio when the reducing agent injection valve duty ratio is zero,
then comparing the integration of the difference between the pump
duty ratio and the reference duty ratio during the predetermined
period, with a determination threshold assumed from the integration
of the reducing agent injection valve duty ratio during the
predetermined period.
[0022] The reducing agent supply apparatus abnormality diagnosis
unit can perform abnormality diagnosis more easily, using the
integration of the pump duty ratio during the predetermined period,
than performing abnormality diagnosis using the integration of the
product of the reducing agent injection valve duty ratio and the
change in the pump duty ratio.
[0023] Furthermore, in configuring the reducing agent supply
apparatus abnormality diagnosis unit of the invention, it is
preferable that an upper threshold and a lower threshold are set as
a determination threshold, and the abnormality determiner uses the
upper threshold and the lower threshold to separately determine an
abnormality of excessive injection amount condition and an
abnormality of insufficient injection amount condition.
[0024] Using the upper threshold and the lower threshold, the
reducing agent supply apparatus abnormality diagnosis unit can
separately determine an abnormality of excessive injection amount
condition and an abnormality of insufficient injection amount
condition, enabling prompting an action depending on the
abnormality condition after the abnormality is detected.
[0025] Furthermore, another aspect of the invention is a reducing
agent supply apparatus including any reducing agent supply
apparatus abnormality diagnosis unit described above.
[0026] Namely, the reducing agent supply apparatus of the invention
includes an abnormality diagnosis unit that eliminates the need for
interrupting usual reducing agent injection control and enables
reliable detection of an abnormality of the reducing agent supply
apparatus, so the reducing agent supply apparatus can supply just
enough reducing agent necessary for NOx purification and, when an
abnormality occurs, can quickly detect the abnormality.
[0027] Note that, in the description, the energization on/off duty
ratio refers to the ratio of the energization ON time to the unit
time, unless otherwise stated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is an overall diagram showing a configuration example
of an exhaust gas purification apparatus including a reducing agent
supply apparatus in accordance with a first embodiment of the
invention.
[0029] FIG. 2 is a block diagram showing a configuration example of
a reducing agent injection valve abnormality diagnosis unit in
accordance with the first embodiment of the invention.
[0030] FIG. 3 is a diagram showing the change in the pressure in a
(second) reducing agent passage and the change in pump duty ratio
when reducing agent injection valve duty ratio is changed.
[0031] FIG. 4 is a diagram for describing an overview of an
abnormality diagnosis method of the reducing agent supply apparatus
in accordance with the first embodiment of the invention.
[0032] FIG. 5 is a flowchart showing a specific example for
implementing the abnormality diagnosis method of the reducing agent
supply apparatus in accordance with the first embodiment of the
invention.
[0033] FIG. 6 is a flowchart showing a specific example of time
integration calculation method.
[0034] FIG. 7 is a flowchart showing a specific example for
abnormality determination in accordance with the first embodiment
of the invention.
[0035] FIG. 8 is a diagram for describing an overview of an
abnormality diagnosis method of a reducing agent supply apparatus
in accordance with a second embodiment of the invention.
[0036] FIG. 9 is a flowchart showing a specific example for
implementing the abnormality diagnosis method of the reducing agent
supply apparatus in accordance with the second embodiment of the
invention.
[0037] FIG. 10 is a flowchart showing a specific example for
abnormality determination in accordance with the second embodiment
of the invention.
DETAILED DESCRIPTION
[0038] Embodiments of a reducing agent supply apparatus abnormality
diagnosis unit and a reducing agent supply apparatus in accordance
with the invention are specifically described below with reference
to the drawings as appropriate. However, the embodiments described
below are intended to show only an aspect of the invention and not
intended to limit the invention, so may be appropriately modified
within the scope of the invention.
[0039] Note that, through the drawings, like numerals denote like
components, and duplicative descriptions will be appropriately
omitted.
First Embodiment
1. Overall Configuration of Exhaust Gas Purification Apparatus
[0040] First, an overview of an overall configuration of an exhaust
gas purification apparatus including a reducing agent supply
apparatus is described.
[0041] FIG. 1 shows an example configuration of an exhaust gas
purification apparatus 10. This exhaust gas purification apparatus
10 is an exhaust gas purification apparatus that purifies NOx
contained in exhaust gas from an internal-combustion engine 1
included in a vehicle or the like, in NOx purification catalyst 11,
using reducing agent.
[0042] The exhaust gas purification apparatus 10 includes as main
components: the NOx purification catalyst 11 provided in the middle
of an exhaust pipe 3 connected to an exhausted system of the
internal-combustion engine 1; a reducing agent supply apparatus 20
that supplies reducing agent by injection in the exhaust pipe 3
upstream of the NOx purification catalyst 11; and a control
processing unit 40 for controlling the operation of the reducing
agent supply apparatus 20.
[0043] The NOx purification catalyst 11 is capable of speeding up a
reaction between reducing agent injected in the exhaust pipe 3 (or
reducing component produced from the reducing agent) and NOx
contained in exhaust gas. As an NOx purification catalyst 11, an
NOx selective reduction catalyst or an NOx adsorber catalyst is
used.
[0044] NOx selective reduction catalyst is catalyst capable of
adsorbing reducing agent and using the reducing agent to
selectively purify NOx contained in exhaust gas flowing into the
catalyst. In using the NOx selective reduction catalyst, urea
aqueous solution or unburnt fuel is used as reducing agent. When
urea aqueous solution is used as reducing agent, urea in urea
aqueous solution is decomposed to produce ammonia (NH3) that reacts
with NOx, which decomposes the NOx into nitrogen (N2) and water
(H2O). Or when unburnt fuel is used as reducing agent, carbon
hydride (HC) in unburnt fuel reacts with NOx, which decomposes the
NOx into nitrogen (N2), carbon dioxide (CO2) and water (H2O).
[0045] NOx adsorber catalyst is catalyst capable of adsorbing NOx
in a state of exhaust gas flowing into catalyst having a lean
air-fuel ratio (i.e., in fuel-lean state), and, when the air-fuel
ratio is switched to a rich state, discharging NOx and using
hydrocarbon (HC) in exhaust gas to purify the NOx. NOx reacting
with hydrocarbon (HC) is decomposed into nitrogen (N2), carbon
dioxide (CO2) and water (H2O). In using the NOx adsorber catalyst,
in order to change the air-fuel ratio of exhaust gas into a rich
state, unburnt fuel as reducing agent is supplied by injection in
the exhaust pipe 3.
2. Reducing Agent Supply Apparatus
[0046] Next, the configuration of the reducing agent supply
apparatus 20 is described in detail.
[0047] The reducing agent supply apparatus 20 includes: a storage
tank 21 for storing liquid reducing agent; a pump unit 22 including
a pump 23 for pumping reducing agent; and a reducing agent
injection valve 25 for injecting in the exhaust pipe 3 the reducing
agent pumped by the pump 23. Among them, the pump 23 and the
reducing agent injection valve 25 are drive-controlled by the
control processing unit 40.
[0048] The storage tank 21 is connected to the pump 23 by a first
reducing agent passage 31. The pump 23 is connected to the reducing
agent injection valve 25 by a second reducing agent passage 33. The
second reducing agent passage 33 is connected with a return passage
35 with the other end connected to the storage tank 21. The return
passage 35 is provided with a relief valve 37 and an orifice 38 in
this order from the second reducing agent passage 33 side.
Furthermore, the second reducing agent passage 33 is provided with
a pressure sensor 27 for detecting a pressure Pu in the second
reducing agent passage 33. However, the pressure sensor 27 only
needs to be able to detect pressure of reducing agent supplied to
the reducing agent injection valve 25, and does not need to be
directly provided on the second reducing agent passage 33.
[0049] For the reducing agent injection valve 25, an
electromagnetic valve is used in which the open/close of the valve
is switched by energizing/non-energizing the valve. The reducing
agent injection valve 25 is configured so that an actual injection
amount Qact is adjusted by adjusting an energization on/off duty
ratio per unit time DV_duty (hereinafter simply referred to as
"injection valve duty ratio") depending on an instructed injection
amount Qtgt determined by calculation.
[0050] For the pump 23, an electric pump is used in which a
discharge amount Vpump is adjusted by adjusting an energization
on/off duty ratio per unit time Pump_duty (hereinafter simply
referred to as "pump duty ratio"). The pump 23 is
feedback-controlled so that the pressure Pu in the second reducing
agent passage 33 is maintained at a preset system pressure Ptgt
(e.g., 0.9 MPa). The pump duty ratio Pump_duty is determined based
on the difference .DELTA.P between the pressure Pu detected by the
pressure sensor 27 and the system pressure Ptgt.
[0051] Furthermore, the pump unit 22 is provided with a reverting
valve 24 for changing the flowing direction of reducing agent
pumped by the pump 23. The reverting valve 24 is, for example, an
electromagnetic changeover valve driven by the control processing
unit 40. In the embodiment, when the reverting valve 24 is
energized, the inlet of the pump 23 is connected to the first
reducing agent passage 31, and the outlet of the pump 23 is
connected to the second reducing agent passage 33; and when the
reverting valve 24 is not energized, the outlet of the pump 23 is
connected to the first reducing agent passage 31, and the inlet of
the pump 23 is connected to the second reducing agent passage
33.
[0052] Then, in controlling the reducing agent injection in the
exhaust pipe 3, the energization to the reverting valve 24 is
stopped, and the passage is switched so that reducing agent flows
from the storage tank 21 side to the reducing agent injection valve
25 side. On the other hand, in performing purge process of
collecting reducing agent into the storage tank 21, the reverting
valve 24 is energized and the passage is switched so that reducing
agent flows from the reducing agent injection valve 25 side to the
storage tank 21 side. Alternatively, the purge process may be
performed by reversing the direction of rotation of the pump 23
without the reverting valve 24.
[0053] The relief valve 37 is a one-way valve for blocking the flow
of reducing agent from the storage tank 21 side to the second
reducing agent passage 33 side, and is configured to open when the
pressure Pu in the second reducing agent passage 33 exceeds the
valve opening pressure of the relief valve 37. Furthermore, in the
purge process of collecting reducing agent from the reducing agent
injection valve 25 and the second reducing agent passage 33, the
relief valve 37 becomes closed in response to depressurization of
the inside of the second reducing agent passage 33. The orifice 38
provided downstream of the relief valve 37 is capable of preventing
the pressure in the second reducing agent passage 33 from pulsating
too much in response to opening/closing of the relief valve 37.
3. Control Processing Unit
Abnormality Diagnosis Unit
[0054] (1) Overall Configuration
[0055] FIG. 2 is a functional block diagram showing a part of the
configuration of the control processing unit 40 included in the
reducing agent supply apparatus 20 of the embodiment, relating to
operation control and abnormality diagnosis of the reducing agent
supply apparatus 20. The control processing unit 40 can serve as an
abnormality diagnosis unit of the reducing agent supply apparatus
20 in accordance with the invention.
[0056] The control processing unit 40 is based on a well known
microcomputer and includes as main components a pressure detector
41, a reducing agent injection valve controller 43, a reverting
valve controller 45, a pump controller 47 and an abnormality
determiner 49. Specifically, these components are implemented by
execution of a program by the microcomputer.
[0057] In addition, the control processing unit 40 includes a
memory device not shown, such as a random access memory (RAM) and a
read only memory (ROM), and a drive circuit and the like not shown
for energizing the pump 23, the reverting valve 24 and the reducing
agent injection valve 25. Furthermore, sensor signals, including a
sensor signal of the pressure sensor 27, are input to the control
processing unit 40 from various sensors provided in the reducing
agent supply apparatus 20, internal-combustion engine 1 and the
like.
[0058] (2) Pressure Detector
[0059] Among them, the pressure detector 41 reads a sensor signal
of the pressure sensor 27 to detect the pressure Pu in the second
reducing agent passage 33.
[0060] (3) Reducing Agent Injection Valve Controller
[0061] When the internal-combustion engine 1 is operating, the
reducing agent injection valve controller 43 calculates an
instructed reducing agent injection amount Qu based on a exhaust
gas temperature Tgas, a catalyst temperature Tcat, an NOx
concentration N downstream of the NOx purification catalyst 11,
even information on operation state of the internal-combustion
engine 1 and the like, then determines the injection valve duty
ratio DV_duty in response to the instructed injection amount Qu,
and then issues an instruction to the drive circuit of the reducing
agent injection valve 25. That is, the larger the instructed
injection amount Qu is, the larger the injection valve duty ratio
DV_duty is.
[0062] On the other hand, when the internal-combustion engine 1 is
stopped, the reducing agent injection valve controller 43, in order
to perform the purge process, issues an instruction to the drive
circuit of the reducing agent injection valve 25 so that the
reducing agent injection valve 25 is kept open.
[0063] (4) Reverting Valve Controller
[0064] When the internal-combustion engine 1 is operating, the
reverting valve controller 45 stops energizing the reverting valve
24 and switches the passage so that reducing agent flows from the
storage tank 21 side to the reducing agent injection valve 25 side.
On the other hand, when the internal-combustion engine 1 is
stopped, the reverting valve controller 45 energizes the reverting
valve 24 to perform the purge process and switches the passage so
that reducing agent flows from the reducing agent injection valve
25 side to the storage tank 21 side.
[0065] (5) Pump Controller
[0066] When the internal-combustion engine 1 is operating, the pump
controller 47 determines the pump duty ratio Pump_duty based on the
difference .DELTA.P between the detected pressure Pu in the second
reducing agent passage 33 and the preset system pressure Ptgt and
issues an instruction to the drive circuit of the pump 23 so that
the pressure so that the pressure Pu becomes equal to the system
pressure Ptgt. The larger the actual reducing agent injection
amount Qact is, the more likely to decrease the pressure Pu in the
second reducing agent passage 33 is, so the pump duty ratio
Pump_duty is relatively large. On the other hand, the smaller the
actual reducing agent injection amount Qact is, the more unlikely
to decrease the pressure Pu in the second reducing agent passage 33
is, so the pump duty ratio Pump_duty is relatively small.
[0067] Particularly, the reducing agent supply apparatus 20 of the
embodiment is configured so that the pump 23 continues to be driven
even when the reducing agent injection amount Qact is zero, and
pumped reducing agent flows in the return passage 35 and circulates
to the storage tank 21. Specifically, the reducing agent supply
apparatus 20 of the embodiment is configured so that, basically,
with respect to the pump duty ratio Pump_duty when the reducing
agent injection amount Qu is zero (hereinafter referred to as
reference duty ratio Pump_duty_default) as the minimum value, the
larger the injection valve duty ratio DV_duty is, the larger the
pump duty ratio Pump_duty is.
[0068] Furthermore, when the internal-combustion engine 1 is
stopped, the pump controller 47 issues an instruction to the drive
circuit of the pump 23 so that the pump 23 is drive-controlled at a
predetermined pump duty ratio Pump_duty_A for a predetermined time
after an ignition switch is turned off.
[0069] (6) Abnormality Determiner
[0070] The abnormality determiner 49 performs a processing for
determining whether or not an abnormality has occurred in the
reducing agent supply apparatus 20. The abnormality determiner 49
is configured to determine whether or not an abnormality has
occurred in the reducing agent supply apparatus 20, based on the
injection valve duty ratio DV_duty and the pump duty ratio
Pump_duty. Particularly, in the embodiment, the abnormality
determiner 49 is configured to determine whether or not an
abnormality has occurred in the reducing agent supply apparatus 20,
using a time integration .SIGMA.(dv_duty.times..DELTA.pump_duty) of
the product of the injection valve duty ratio DV_duty and the
difference .DELTA.pump_duty between the pump duty ratio Pump_duty
and the reference duty Pump_duty_default.
[0071] (6-1) Relation Between Injection Valve Duty Ratio and Pump
Duty Ratio
[0072] Here, the changes in the pressure Pu in the second reducing
agent passage 33 and in the pump duty ratio Pump_duty versus the
change in the injection valve duty ratio DV_duty are shown in FIG.
3. FIG. 3 shows the changes in various values when the injection
valve duty ratio DV_duty is caused to change such that
0.fwdarw.Dd1.fwdarw.Dd2.fwdarw.Dd1.fwdarw.0 (Dd2>Dd1>0) for
the purpose of illustrating, when the reducing agent injection
valve 25 of the reducing agent supply apparatus 20 has three
injection nozzles, the difference among the various values with
respect to the difference in the extent of clogging of the
injection nozzles of the reducing agent injection valve 25.
[0073] Note that the pressure Pu and the pump duty ratio Pump_duty
pulsate because the pressure Pu in the second reducing agent
passage 33 pulsates along to the discharge of reducing agent by the
pump 23, in response to which the pump duty ratio Pump_duty
increases and decreases.
[0074] First, in the period A in which the injection valve duty
ratio DV_duty is set to 0, all of the reducing agent discharged by
the pump 23 is returned to the storage tank 21 through the return
passage 35, so the pump duty ratio Pump_duty varies with respect to
the reference duty ratio Pump_duty_default as center, irrespective
of the extent of clogging of the reducing agent injection valve
25.
[0075] In the next period B in which the injection valve duty ratio
DV_duty is set to Dd1, reducing agent injection is started by the
reducing agent injection valve 25, so the pressure Pu in the second
reducing agent passage 33 temporarily decreases. At this time, even
when the reducing agent injection valve 25 is opened in the same
way, the larger the extent of clogging of the injection nozzles is,
the smaller the rate of decrease in the pressure Pu is. So, the
larger the extent of clogging of the injection nozzles is, the
smaller the rate of increase in the pump duty ratio Pump_duty
immediately after the injection valve duty ratio DV_duty is changed
to Dd1 is.
[0076] Subsequently, in the period B, the pump duty ratio Pump_duty
is maintained at a value larger than the reference duty ratio
Pump_duty_default, which maintains the pressure Pu at the system
pressure Ptgt. However, the larger the extent of clogging of the
injection nozzles is, the smaller the rate of decrease in the
pressure Pu is, so the larger the extent of clogging of the
injection nozzles is, the smaller the pump duty ratio Pump_duty in
the period B is
(.DELTA.Dpc(Dd1)<.DELTA.Dpb(Dd1)<.DELTA.Dpa(Dd1)).
[0077] In the next period C in which the injection valve duty ratio
DV_duty is set to Dd2, the amount of reducing agent injection by
the reducing agent injection valve 25 increases, so the pressure Pu
and the pump duty ratio Pump_duty vary depending on the extent of
clogging of the injection nozzles, as with the period B.
Specifically, the larger the extent of clogging of the injection
nozzles is, the smaller the rate of decrease in the pressure Pu
immediately after the injection valve duty ratio DV_duty is changed
to Dd2 and the rate of increase in the pump duty ratio Pump_duty
are, and furthermore, subsequently, in the period C, the larger the
extent of clogging of the injection nozzles is, the smaller the
pump duty ratio Pump_duty is
(.DELTA.Dpc(Dd2)<.DELTA.Dpb(Dd2)<.DELTA.Dpa(Dd2)).
[0078] In the next period D in which the injection valve duty ratio
DV_duty is set to Dd1, the amount of reducing agent injection by
the reducing agent injection valve 25 decreases, so the pressure Pu
in the second reducing agent passage 33 temporarily increases. At
this time, even when the reducing agent injection valve 25 is
opened in the same way, the larger the extent of clogging of the
injection nozzles is, the smaller the rate of increase in the
pressure Pu is. So, the larger the extent of clogging of the
injection nozzles is, the smaller the rate of decrease in the pump
duty ratio Pump_duty immediately after the injection valve duty
ratio DV_duty is changed to Dd1 is. Subsequently, in the period D,
the pump duty ratio Pump_duty is maintained at a value similar to
that in the period B, and the larger the extent of clogging of the
injection nozzles is, the smaller the pump duty ratio Pump_duty is
(.DELTA.Dpc(Dd1)<.DELTA.Dpb(Dd1)<.DELTA.Dpa(Dd1)).
[0079] Similarly, in the next period E in which the injection valve
duty ratio DV_duty is set to 0, the larger the extent of clogging
of the injection nozzles is, the smaller the rate of decrease in
the pressure Pu immediately after the injection valve duty ratio
DV_duty is changed to 0 and the rate of decrease in the pump duty
ratio Pump_duty are. However, subsequently, in the period E,
reducing agent injection is not performed, so the pump duty ratio
Pump_duty again varies with respect to the reference duty ratio
Pump_duty_default as center, irrespective of the extent of clogging
of the reducing agent injection valve 25.
[0080] As seen from the above, even when the reducing agent
injection valve 25 is drive-controlled with the same injection
valve duty ratio DV_duty, the pump duty ratio Pump_duty varies
depending on the extent of clogging of the injection nozzles. In
other words, even when the reducing agent injection valve 25 is
drive-controlled with the same injection valve duty ratio DV_duty,
the pump duty ratio Pump_duty when the injection amount of the
reducing agent supply apparatus 20 is excessive or insufficient may
be different from the pump duty ratio Pump_duty in normal
state.
[0081] The abnormality determiner 49 attempts to detect an
abnormality occurring in the reducing agent supply apparatus 20 by
determining whether or not the relation between the injection valve
duty ratio DV_duty and the pump duty ratio Pump_duty is normal.
[0082] The rate of change in the pressure Pu immediately after the
injection valve duty ratio DV_duty is changed also varies depending
on the extent of clogging of the injection nozzles, but, as time
elapses after that, the pressure Pu returns to the system pressure
Ptgt. On the other hand, even after the injection valve duty ratio
DV_duty is changed, the pump duty ratio Pump_duty still varies
depending on the extent of clogging of the injection nozzles. Due
to this, in the embodiment, the pump duty ratio Pump_duty is used
that is more likely to vary significantly when integrated.
[0083] (6-2) Specific Example of Abnormality Diagnosis Method
[0084] Next, an overview of a method for diagnosing an abnormality
of the reducing agent supply apparatus 20 implemented by the
abnormality determiner 49 based on the relation between the
injection valve duty ratio DV_duty and the pump duty ratio
Pump_duty is given with reference to a time chart shown in FIG.
4.
[0085] FIG. 4 shows the transition of the on/off of the ignition
switch, the injection valve duty ratio DV_duty, the pump duty ratio
Pump_duty, the time-integration .SIGMA.dv_duty of the injection
valve duty ratio DV_duty, the time-integration
.SIGMA..DELTA.pump_duty of the difference of pump duty ratio
.DELTA.pump_duty and the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty) of the product of the
injection valve duty ratio DV_duty and the difference of pump duty
ratio .DELTA.pump_duty.
[0086] With the ignition switch being on and the
internal-combustion engine 1 operating, when reducing agent
injection is performed, the reducing agent injection valve 25 is
drive-controlled with the injection valve duty ratio DV_duty larger
than 0. Furthermore, since the pressure Pu in the second reducing
agent passage 33 decreases in association with reducing agent
injection, the pump duty ratio Pump_duty also varies so as to
follow the injection valve duty ratio DV_duty in order to maintain
the pressure Pu at the system pressure Ptgt.
[0087] Accordingly, in the period during which reducing agent
injection is performed, the time integrations .SIGMA.dv_duty,
.SIGMA..DELTA.pump_duty and .SIGMA.(dv_duty.times..DELTA.pump_duty)
increase. On the other hand, in the period during which reducing
agent injection is not performed, the time integrations
.SIGMA.dv_duty, .SIGMA..DELTA.pump_duty and
.SIGMA.(dv_duty.times..DELTA.pump_duty) do not increase.
[0088] Then, when a predetermined period elapses, it is determined
whether or not the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty) of the product of the
injection valve duty ratio DV_duty in the period and the difference
of pump duty ratio .DELTA.pump_duty is within a range assumed based
on the time integration .SIGMA.dv_duty of the injection valve duty
ratio DV_duty in the period, which allows the diagnosis whether or
not an abnormality has occurred in the reducing agent supply
apparatus 20.
[0089] Specifically, when the injection amount of the reducing
agent supply apparatus 20 is excessive, the pump duty ratio
Pump_duty during the injection period is larger (broken line) than
the pump duty ratio Pump_duty in normal state (solid line). On the
other hand, when the injection amount of the reducing agent supply
apparatus 20 is insufficient, the pump duty ratio Pump_duty during
the injection period is smaller (alternate long and short dash
line) than the pump duty ratio Pump_duty in normal state (solid
line).
[0090] Due to this, when an abnormality has occurred to cause the
excessive injection amount condition of the reducing agent supply
apparatus 20, the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty) of the product of the
injection valve duty ratio DV_duty and the difference of pump duty
ratio .DELTA.pump_duty is, as shown by the broken line, larger than
that in normal state (solid line). On the other hand, when an
abnormality has occurred to cause the insufficient injection amount
condition of the reducing agent supply apparatus 20, the time
integration .SIGMA.(dv_duty.times..DELTA.pump_duty) of the product
of the injection valve duty ratio DV_duty and the difference of
pump duty ratio .DELTA.pump_duty is, as shown by the alternate long
and short dash line, smaller than that in normal state (solid
line).
[0091] Thus, it can be determined whether or not an abnormality has
occurred in the reducing agent supply apparatus 20, by setting an
upper threshold Thre_max for determining the excessive injection
amount condition and a lower threshold Thre_min for determining the
insufficient injection amount condition, then comparing the time
integration .SIGMA.(dv_duty.times..DELTA.pump_duty) after the
predetermined period elapses with each of the thresholds. The
thresholds Thre_max and Thre_min can be set considering temperature
of reducing agent, tolerance and the like.
[0092] In the example shown in FIG. 4, the determination is
performed using the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty) over the period from when
the time integration of the injection valve duty ratio DV_duty is
started to when this time integration .SIGMA.dv_duty reaches a
determination start value .SIGMA.dv_duty_thre. This causes the
variation in the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty) depending on whether or not
an abnormality has occurred in the reducing agent supply apparatus
20 to be seen clearly.
[0093] The determination can also be performed using the time
integration .SIGMA..DELTA.pump_duty of the difference of pump duty
ratio .DELTA.pump_duty, but, in the example shown in FIG. 4, the
time integration .SIGMA.(dv_duty.times..DELTA.pump_duty) of the
product of the injection valve duty ratio DV_duty and the
difference of pump duty ratio .DELTA.pump_duty is used for the
determination. As a result, the variation depending on whether or
not an abnormality has occurred in the reducing agent supply
apparatus 20 can be seen more clearly, which facilitates the
setting of the upper threshold Thre_max and lower threshold
Thre_min.
[0094] (6-3) Specific Example of Abnormality Diagnosis
Flowchart
[0095] Next, one example of flowchart in which the abnormality
diagnosis method shown in FIG. 4 is implemented by the control
processing unit 40 is described with reference to FIGS. 5-7.
[0096] First, the control processing unit 40, in step S1 of FIG. 5,
starts injection control of reducing agent, then, in step S2,
resets the currently stored time integration .SIGMA.dv_duty,
.SIGMA.(dv_duty.times..DELTA.pump_duty)_final. Next, in step S3,
the control processing unit 40 reads the pump duty ratio Pump_duty
when the injection valve duty ratio DV_duty is 0% and sets it as
the reference duty ratio Pump_duty_default.
[0097] Next, in step S4, the control processing unit 40 determines
whether or not the time integration .SIGMA.dv_duty of the injection
valve duty ratio DV_duty is less than the determination start value
.SIGMA.dv_duty_thre. If YES in step S4, it is determined that the
precise abnormality determination is not ready, so the process does
not proceed to step S8 for performing abnormality determination,
but proceeds to step S5.
[0098] In step S5, the control processing unit 40 determines
whether or not the injection valve duty ratio DV_duty is within a
predetermined range over which the integration is to be performed.
This range may be simply set to be equal to or more than 0%.
However, for example, the lower limit of the injection valve duty
ratio DV_duty may also be set to be larger than 0% so that the
integration is performed only when reducing agent is injected with
a flow rate equal to or larger than a predetermined flow rate. Or a
range of the injection valve duty ratio DV_duty in which the ratio
of the variation in the pump duty ratio Pump_duty to the variation
in the injection valve duty ratio DV_duty is constant may be
previously determined so that the integration is performed only
when the injection valve duty ratio DV_duty is within the range.
This way of setting the range of the injection valve duty ratio
DV_duty over which the integration is to be performed can improve
the precision of the diagnosis.
[0099] If NO in step S5, it is determined that both the injection
valve duty ratio DV_duty and the pump duty ratio Pump_duty are not
varying. Then, since the integration step is not needed, the
process returns to step S4 with no particular action. On the other
hand, if YES in step S5, the control processing unit 40, in step
S6, calculates the time integration .SIGMA.dv_duty of the injection
valve duty ratio DV_duty, then in step S7, calculates the time
integration .SIGMA.(dv_duty.times..DELTA.pump_duty)_final of the
product of the injection valve duty ratio DV_duty and the
difference of pump duty ratio .DELTA.pump_duty.
[0100] FIG. 6 is a flowchart specifically showing the process of
calculating the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty)_final.
[0101] In this example, in step S11, the control processing unit 40
multiplies the injection valve duty ratio DV_duty by the difference
of pump duty ratio Pump_duty-Pump_duty_default and by the time
On_time during which the injection is performed of the period from
the previous integration to the current integration to determine
the time integration .SIGMA.(dv_duty.times..DELTA.pump_duty)_Pre to
be added this time.
[0102] After the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty)_Pre is determined, the
control processing unit 40, in step S12, adds the current time
integration .SIGMA.(dv_duty.times..DELTA.pump_duty)_Pre determined
in step S11 to the currently stored time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty)_final, thereby determining
the current time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty)_final, then updates the
stored value.
[0103] Returning to FIG. 5, when the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty) is calculated in step S7,
the process returns to step S4 again to repeat the previous steps.
Then, when the time integration .SIGMA.dv_duty of the injection
valve duty ratio DV_duty reaches the determination start value
.SIGMA.dv_duty_thre, it is determined to be NO in step S4 and the
process proceeds to step S8. In step S8, the control processing
unit 40 performs abnormality determination based on the time
integration .SIGMA.(dv_duty.times..DELTA.pump_duty)_final.
[0104] FIG. 7 is a flowchart specifically showing the process of
abnormality determination performed in step S8.
[0105] In this example, first, in step S21, the control processing
unit 40 determines whether or not the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty)_final exceeds the upper
threshold Thre_max. If YES in step S21, the control processing unit
40 determines in step S22 that an abnormality causing the excessive
injection amount condition has occurred in the reducing agent
supply apparatus 20, then proceeds to step S25.
[0106] On the other hand, if NO in step S21, the process proceeds
to step S23 in which the control processing unit 40 determines
whether or not the time integration
.SIGMA.(dv_duty.times..DELTA.pump_duty)_final is below the lower
threshold Thre_min. If YES in step S23, the control processing unit
40 determines in step S24 that an abnormality causing the
insufficient injection amount condition has occurred in the
reducing agent supply apparatus 20, then proceeds to step S25. On
the other hand, if NO in step S23, it is determined that no
abnormality has occurred in the reducing agent supply apparatus 20,
so the abnormality determination process ends with no particular
action.
[0107] When it is determined in step S22 that an abnormality
causing the excessive injection amount condition has occurred or
when it is determined in step S24 that an abnormality causing the
insufficient injection amount condition has occurred, the control
processing unit 40, in step S25, issues an instruction to a
notifier or the like in order to notify an operator or the like of
that abnormality. In response to this notification of the
abnormality, the operation of the reducing agent supply apparatus
20 may be stopped or the internal-combustion engine 1 may be
controlled to reduce output power.
[0108] According to the method for diagnosing an abnormality of the
reducing agent supply apparatus 20 implemented by the control
processing unit (abnormality diagnosis unit) 40 of the embodiment
described above, abnormality diagnosis is performed based on the
injection valve duty ratio DV_duty and the pump duty ratio
Pump_duty, which enables abnormality diagnosis of the reducing
agent supply apparatus 20 without changing any component other than
the control processing unit 40 and without interrupting usual
reducing agent injection control.
[0109] Especially, in the embodiment, abnormality determination is
performed using the time integration of the product of the
injection valve duty ratio DV_duty and the difference of pump duty
ratio .DELTA.pump_duty, which causes the variation in the time
integration depending on whether or not an abnormality has occurred
to be seen clearly, thereby improving the precision of the
diagnosis. Furthermore, the period over which the time integration
is performed is a period in which the injection valve duty ratio
DV_duty reaches a predetermined determination start value
DV_duty_thre, which causes the variation in the time integration
depending on whether or not an abnormality has occurred, to be seen
reliably, thereby improving the precision of the diagnosis and
increasing the frequency of the diagnosis.
Second Embodiment
[0110] Next, a reducing agent supply apparatus abnormality
diagnosis unit in accordance with a second embodiment of the
invention is described.
[0111] The reducing agent supply apparatus abnormality diagnosis
unit of the embodiment is to be applied to the reducing agent
supply apparatus 20 described in the first embodiment, and
basically has a configuration similar to that of the control
processing unit 40 of the first embodiment shown in FIG. 2.
However, the abnormality determination method implemented by the
abnormality determiner 49 is different from that of the abnormality
diagnosis unit of the first embodiment.
[0112] In the embodiment, the abnormality determiner 49 is
configured to determine whether or not an abnormality has occurred
in the reducing agent supply apparatus 20 based on the ratio of the
time integration .SIGMA.dv_duty of the injection valve duty ratio
to the time integration .SIGMA..DELTA.pump_duty of the difference
.DELTA.pump_duty between the pump duty ratio Pump_duty and the
reference duty Pump_duty_default.
[0113] 1. Specific Example of Abnormality Diagnosis Method
[0114] FIG. 8 shows the transition of the on/off of the ignition
switch, the injection valve duty ratio DV_duty, the pump duty ratio
Pump_duty, the time-integration .SIGMA.dv_duty of the injection
valve duty ratio, the time-integration .SIGMA..DELTA.pump_duty of
the difference of pump duty ratio, and the time-integration
.SIGMA.dv_duty of the injection valve duty ratio divided by the
time-integration .SIGMA..DELTA.pump_duty of the difference of pump
duty ratio.
[0115] The changes in the pump duty ratio Pump_duty, the time
integration .SIGMA.dv_duty of the injection valve duty ratio and
the time integration .SIGMA..DELTA.pump_duty of the difference of
pump duty ratio in association with the change in the injection
valve duty ratio DV_duty is similar to that described with
reference to FIG. 4.
[0116] Note that the flow rate of reducing agent discharged by the
pump 23 varies in proportion to the flow rate of injected reducing
agent, so the pump duty ratio Pump_duty and the injection valve
duty ratio DV_duty would be almost in a proportional relationship.
Accordingly, theoretically, when the reducing agent supply
apparatus 20 is in normal state, the time integration
.SIGMA.dv_duty of the injection valve duty ratio divided by the
time integration .SIGMA..DELTA.pump_duty of the difference of pump
duty ratio would remain almost constant. Thus, it can be diagnosed
whether or not an abnormality has occurred in the reducing agent
supply apparatus 20, by determining whether or not the time
integration .SIGMA.dv_duty of the injection valve duty ratio
divided by the time integration .SIGMA..DELTA.pump_duty of the
difference of pump duty ratio is within a predetermined range
during a predetermined period.
[0117] Specifically, when the injection amount of the reducing
agent supply apparatus 20 is excessive, the pump duty ratio
Pump_duty during the injection period is larger (broken line) than
the pump duty ratio Pump_duty in normal state (solid line). On the
other hand, when the injection amount of the reducing agent supply
apparatus 20 is insufficient, the pump duty ratio Pump_duty during
the injection period is smaller (alternate long and short dash
line) than the pump duty ratio Pump_duty in normal state (solid
line).
[0118] Due to this, when an abnormality has occurred to cause the
excessive injection amount condition of the reducing agent supply
apparatus 20, the time integration .SIGMA.dv_duty of the injection
valve duty ratio divided by the time integration
.SIGMA..DELTA.pump_duty of the difference of pump duty ratio is, as
shown by the broken line, smaller than that in normal state (solid
line). On the other hand, when an abnormality has occurred to cause
the insufficient injection amount condition of the reducing agent
supply apparatus 20, the time integration .SIGMA.dv_duty of the
injection valve duty ratio divided by the time integration
.SIGMA..DELTA.pump_duty of the difference of pump duty ratio is, as
shown by the alternate long and short dash line, larger than that
in normal state (solid line).
[0119] Thus, it can be determined whether or not an abnormality has
occurred in the reducing agent supply apparatus 20, by setting an
upper threshold Thre_max for determining the insufficient injection
amount condition and a lower threshold Thre_min for determining the
excessive injection amount condition, then comparing the time
integration .SIGMA.dv_duty of the injection valve duty ratio
divided by the time integration .SIGMA..DELTA.pump_duty of the
difference of pump duty ratio after the predetermined period
elapses with each of the thresholds. The thresholds Thre_max and
Thre_min can also be set considering temperature of reducing agent,
tolerance and the like.
[0120] In the example shown in FIG. 8, the determination is
performed using the time integrations .SIGMA.dv_duty,
.SIGMA..DELTA.pump_duty over the period from when the time
integration of the injection valve duty ratio DV_duty is started to
when this time integration .SIGMA.dv_duty reaches a determination
start value .SIGMA.dv_duty_thre. Thus, even when the change in the
pump duty ratio Pump_duty temporarily shifts with respect to the
change in the injection valve duty ratio DV_duty, the impact of
this shift on the abnormality determination is small.
[0121] 2. Specific Example of Abnormality Diagnosis Flowchart
[0122] Next, one example of flowchart in which the abnormality
diagnosis method shown in FIG. 8 is implemented by the control
processing unit 40 is described with reference to FIGS. 9-10.
[0123] First, the control processing unit 40, in step S31 of FIG.
9, starts injection control of reducing agent, then, in step S32,
resets the currently stored time integrations .SIGMA.dv_duty,
.SIGMA..DELTA.pump_duty. Next, in step S33, the control processing
unit 40 reads the pump duty ratio Pump_duty when the injection
valve duty ratio DV_duty is 0% and sets it as the reference duty
ratio Pump_duty_default.
[0124] Next, in step S34, the control processing unit 40 determines
whether or not the time integration .SIGMA.dv_duty of the injection
valve duty ratio DV_duty is less than the determination start value
.SIGMA.dv_duty_thre. If YES in step S34, it is determined that the
precise abnormality determination is not ready, so the process does
not proceed to step S38 for performing abnormality determination,
but proceeds to step S35.
[0125] In step S35, the control processing unit 40 determines
whether or not the injection valve duty ratio DV_duty is within a
predetermined range over which the integration is to be performed.
Similarly to the first embodiment, this range may be simply set to
be equal to or more than 0%. However, for example, the lower limit
of the injection valve duty ratio DV_duty may also be set to be
larger than 0% so that the integration is performed only when
reducing agent is injected with a flow rate equal to or larger than
a predetermined flow rate. Or a range of the injection valve duty
ratio DV_duty in which the ratio of the variation in the pump duty
ratio Pump_duty to the variation in the injection valve duty ratio
DV_duty is constant may be previously determined so that the
integration is performed only when the injection valve duty ratio
DV_duty is within the range. This way of setting the range of the
injection valve duty ratio DV_duty over which the integration is to
be performed can improve the precision of the diagnosis.
[0126] If NO in step S35, it is determined that both the injection
valve duty ratio DV_duty and the pump duty ratio Pump_duty are not
varying. Then, since the integration step is not needed, the
process returns to step S34 with no particular action. On the other
hand, if YES in step S35, the control processing unit 40, in step
S36, calculates the time integration .SIGMA.dv_duty of the
injection valve duty ratio DV_duty, then in step S37, calculates
the time integration .SIGMA..DELTA.pump_duty of the difference of
pump duty ratio .DELTA.pump_duty.
[0127] When the time integrations .SIGMA.dv_duty,
.SIGMA..DELTA.pump_duty are calculated in step S36 and step S37,
the process returns to step S34 again to repeat the previous steps.
Then, when the time integration .SIGMA.dv_duty of the injection
valve duty ratio DV_duty reaches the determination start value
.SIGMA.dv_duty_thre, it is determined to be NO in step S34 and the
process proceeds to step S38. In step S38, the control processing
unit 40 performs abnormality determination based on the time
integration .SIGMA.dv_duty of the injection valve duty ratio
divided by the time integration .SIGMA..DELTA.pump_duty of the
difference of pump duty ratio.
[0128] FIG. 10 is a flowchart specifically showing the process of
abnormality determination performed in step S38.
[0129] In this example, first, in step S41, the control processing
unit 40 determines whether or not the time integration
.SIGMA.dv_duty of the injection valve duty ratio divided by the
time integration .SIGMA..DELTA.pump_duty of the difference of pump
duty ratio is below the lower threshold Thre_min. If YES in step
S41, the control processing unit 40 determines in step S42 that an
abnormality causing the insufficient injection amount condition has
occurred in the reducing agent supply apparatus 20, then proceeds
to step S45.
[0130] On the other hand, if NO in step S41, the control processing
unit 40 determines in step S43 whether or not the time integration
.SIGMA.dv_duty of the injection valve duty ratio divided by the
time integration .SIGMA..DELTA.pump_duty of the difference of pump
duty ratio exceeds the upper threshold Thre_max. If YES in step
S43, the control processing unit 40 determines in step S44 that an
abnormality causing the excessive injection amount condition has
occurred in the reducing agent supply apparatus 20, then proceeds
to step S45. On the other hand, if NO in step S43, it is determined
that no abnormality has occurred in the reducing agent supply
apparatus 20, so the abnormality determination process ends with no
particular action.
[0131] When it is determined in step S42 that an abnormality
causing the insufficient injection amount condition has occurred or
when it is determined in step S44 that an abnormality causing the
excessive injection amount condition has occurred, the control
processing unit 40, in step S45, issues an instruction to a
notifier or the like in order to notify an operator or the like of
that abnormality. In response to this notification of the
abnormality, the operation of the reducing agent supply apparatus
20 may be stopped or the internal-combustion engine 1 may be
controlled to reduce output power.
[0132] According to the method for diagnosing an abnormality of the
reducing agent supply apparatus 20 implemented by the control
processing unit (abnormality diagnosis unit) 40 of the embodiment
described above, abnormality diagnosis is performed based on the
injection valve duty ratio DV_duty and the pump duty ratio
Pump_duty, which enables abnormality diagnosis of the reducing
agent supply apparatus 20 without changing any component other than
the control processing unit 40 and without interrupting usual
reducing agent injection control.
[0133] Especially, in the embodiment, abnormality determination is
performed using the time integration .SIGMA.dv_duty of the
injection valve duty ratio divided by the time integration
.SIGMA..DELTA.pump_duty of the difference of pump duty ratio, so
even when the change in the pump duty ratio Pump_duty temporarily
shifts with respect to the change in the injection valve duty ratio
DV_duty, the impact of this shift on the abnormality determination
is small, which improves the precision of the diagnosis.
Other Embodiment
[0134] The embodiments described above may also be modified and
implemented as follows.
[0135] For example, the period over which the time integration is
performed in order to obtain data for abnormality determination is
not limited to a period in which the injection valve duty ratio
DV_duty reaches the determination start value DV_duty_thre, but may
be set so that abnormality determination is performed each time an
amount of time elapses in which absolutely a predetermined amount
or more of reducing agent is injected. However, in order to set
that period as above in performing the abnormality determination of
the first embodiment, map information or the like needs to be
previously stored so that a determination threshold is selected
depending on the time integration .SIGMA.dv_duty of the injection
valve duty ratio DV_duty when that period elapses.
[0136] Furthermore, in performing the abnormality diagnosis of the
first embodiment, by setting the period so that the time
integration .SIGMA.pump_duty is relatively large, even when
abnormality diagnosis is performed by comparing the time
integration .SIGMA.pump_duty of the pump duty ratio Pump_duty with
a determination threshold, precise abnormality diagnosis can be
performed.
[0137] Furthermore, in performing the abnormality determination of
the second embodiment, in the above-described embodiment, the time
integration .SIGMA.dv_duty of the injection valve duty ratio
divided by the time integration .SIGMA..DELTA.pump_duty of the
difference of pump duty ratio is compared with a determination
threshold, but the time integration .SIGMA..DELTA.pump_duty of the
difference of pump duty ratio divided by the time integration
.SIGMA.dv_duty of the injection valve duty ratio may also be
compared with a determination threshold. In this case, contrary to
the above-described embodiment, when the time integration
.SIGMA..DELTA.pump_duty of the difference of pump duty ratio
divided by the time integration .SIGMA.dv_duty of the injection
valve duty ratio exceeds the upper threshold Thre_max, it is
determined that an abnormality causing the excessive injection
amount condition has occurred, and when being below the lower
threshold Thre_min, it is determined that an abnormality causing
the insufficient injection amount condition has occurred.
* * * * *