US20130283771A1 - Reducing agent supply apparatus abnormality diagnosis unit and reducing agent supply apparatus - Google Patents

Reducing agent supply apparatus abnormality diagnosis unit and reducing agent supply apparatus Download PDF

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Publication number
US20130283771A1
US20130283771A1 US13/997,909 US201113997909A US2013283771A1 US 20130283771 A1 US20130283771 A1 US 20130283771A1 US 201113997909 A US201113997909 A US 201113997909A US 2013283771 A1 US2013283771 A1 US 2013283771A1
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Prior art keywords
reducing agent
duty ratio
pump
injection valve
abnormality
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US13/997,909
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English (en)
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Masayasu Nagata
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Bosch Corp
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Bosch Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/05—Systems for adding substances into exhaust
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/14—Systems for adding secondary air into exhaust
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/08—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a pressure sensor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1433—Pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1433—Pumps
    • F01N2610/144—Control thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1453—Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
    • F01N2610/146—Control thereof, e.g. control of injectors or injection valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0416—Methods of control or diagnosing using the state of a sensor, e.g. of an exhaust gas sensor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0418—Methods of control or diagnosing using integration or an accumulated value within an elapsed period
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
    • F01N2900/1806—Properties of reducing agent or dosing system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
    • F01N2900/1806—Properties of reducing agent or dosing system
    • F01N2900/1808—Pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
    • F01N2900/1806—Properties of reducing agent or dosing system
    • F01N2900/1821—Injector parameters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
    • F01N2900/1806—Properties of reducing agent or dosing system
    • F01N2900/1822—Pump parameters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • 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.
  • an 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.
  • NOx purification catalyst provided in the middle of an exhaust passage, for speeding up reduction reaction between NOx and reducing agent
  • 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.
  • 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.
  • an apparatus 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).
  • 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.
  • 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.
  • 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.
  • a reducing agent supply apparatus abnormality diagnosis unit for performing abnormality diagnosis of a reducing agent supply apparatus
  • 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
  • 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
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • Another aspect of the invention is a reducing agent supply apparatus including any reducing agent supply apparatus abnormality diagnosis unit described above.
  • 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.
  • the energization on/off duty ratio refers to the ratio of the energization ON time to the unit time, unless otherwise stated.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • FIG. 6 is a flowchart showing a specific example of time integration calculation method.
  • FIG. 7 is a flowchart showing a specific example for abnormality determination in accordance with the first embodiment of the invention.
  • 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.
  • 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.
  • FIG. 10 is a flowchart showing a specific example for abnormality determination in accordance with the second embodiment of the invention.
  • 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.
  • 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 .
  • 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.
  • an NOx purification catalyst 11 an NOx selective reduction catalyst or an NOx adsorber catalyst is used.
  • 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.
  • urea aqueous solution or unburnt fuel 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).
  • NH3 ammonia
  • H2O water
  • 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).
  • 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).
  • unburnt fuel as reducing agent is supplied by injection in the exhaust pipe 3 .
  • 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 .
  • the pump 23 and the reducing agent injection valve 25 are drive-controlled by the control processing unit 40 .
  • 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.
  • 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 .
  • 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 .
  • 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.
  • Pump duty ratio 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 ⁇ P between the pressure Pu detected by the pressure sensor 27 and the system pressure Ptgt.
  • 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 .
  • the reverting valve 24 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 .
  • 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.
  • 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.
  • the purge process may be performed by reversing the direction of rotation of the pump 23 without the reverting valve 24 .
  • 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 .
  • 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.
  • 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.
  • 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 .
  • 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.
  • 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 .
  • 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.
  • 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.
  • 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.
  • 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.
  • the pump controller 47 determines the pump duty ratio Pump_duty based on the difference ⁇ 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 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.
  • 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 .
  • 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.
  • 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.
  • 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.
  • 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 ⁇ (dv_duty ⁇ pump_duty) of the product of the injection valve duty ratio DV_duty and the difference ⁇ pump_duty between the pump duty ratio Pump_duty and the reference duty Pump_duty_default.
  • FIG. 3 shows the changes in various values when the injection valve duty ratio DV_duty is caused to change such that 0 ⁇ Dd 1 ⁇ Dd 2 ⁇ Dd 1 ⁇ 0 (Dd 2 >Dd 1 >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 .
  • 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.
  • 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 ( ⁇ Dpc(Dd 1 ) ⁇ Dpb(Dd 1 ) ⁇ Dpa(Dd 1 )).
  • the pump duty ratio Pump_duty varies depending on the extent of clogging of the injection nozzles.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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 ⁇ dv_duty of the injection valve duty ratio DV_duty, the time-integration ⁇ pump_duty of the difference of pump duty ratio ⁇ pump_duty and the time integration ⁇ (dv_duty ⁇ pump_duty) of the product of the injection valve duty ratio DV_duty and the difference of pump duty ratio ⁇ pump_duty.
  • 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.
  • the time integrations ⁇ dv_duty, ⁇ pump_duty and ⁇ (dv_duty ⁇ pump_duty) increase.
  • the time integrations ⁇ dv_duty, ⁇ pump_duty and ⁇ (dv_duty ⁇ pump_duty) do not increase.
  • 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).
  • 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).
  • the time integration ⁇ (dv_duty ⁇ pump_duty) of the product of the injection valve duty ratio DV_duty and the difference of pump duty ratio ⁇ pump_duty is, as shown by the broken line, larger than that in normal state (solid line).
  • the time integration ⁇ (dv_duty ⁇ pump_duty) of the product of the injection valve duty ratio DV_duty and the difference of pump duty ratio ⁇ pump_duty is, as shown by the alternate long and short dash line, smaller than that in normal state (solid line).
  • the reducing agent supply apparatus 20 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 ⁇ (dv_duty ⁇ 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.
  • the determination is performed using the time integration ⁇ (dv_duty ⁇ 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 ⁇ dv_duty reaches a determination start value ⁇ dv_duty_thre.
  • This causes the variation in the time integration ⁇ (dv_duty ⁇ pump_duty) depending on whether or not an abnormality has occurred in the reducing agent supply apparatus 20 to be seen clearly.
  • the determination can also be performed using the time integration ⁇ pump_duty of the difference of pump duty ratio ⁇ pump_duty, but, in the example shown in FIG. 4 , the time integration ⁇ (dv_duty ⁇ pump_duty) of the product of the injection valve duty ratio DV_duty and the difference of pump duty ratio ⁇ pump_duty is used for the determination.
  • the time integration ⁇ (dv_duty ⁇ pump_duty) of the product of the injection valve duty ratio DV_duty and the difference of pump duty ratio ⁇ pump_duty is used for the determination.
  • control processing unit 40 starts injection control of reducing agent, then, in step S 2 , resets the currently stored time integration ⁇ dv_duty, ⁇ (dv_duty ⁇ pump_duty)_final.
  • step S 3 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.
  • step S 4 the control processing unit 40 determines whether or not the time integration ⁇ dv_duty of the injection valve duty ratio DV_duty is less than the determination start value ⁇ dv_duty_thre. If YES in step S 4 , it is determined that the precise abnormality determination is not ready, so the process does not proceed to step S 8 for performing abnormality determination, but proceeds to step S 5 .
  • step S 5 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%.
  • 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.
  • 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.
  • step S 5 If NO in step S 5 , 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 S 4 with no particular action. On the other hand, if YES in step S 5 , the control processing unit 40 , in step S 6 , calculates the time integration ⁇ dv_duty of the injection valve duty ratio DV_duty, then in step S 7 , calculates the time integration ⁇ (dv_duty ⁇ pump_duty)_final of the product of the injection valve duty ratio DV_duty and the difference of pump duty ratio ⁇ pump_duty.
  • FIG. 6 is a flowchart specifically showing the process of calculating the time integration ⁇ (dv_duty ⁇ pump_duty)_final.
  • step S 11 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 ⁇ (dv_duty ⁇ pump_duty)_Pre to be added this time.
  • step S 12 adds the current time integration ⁇ (dv_duty ⁇ pump_duty)_Pre determined in step S 11 to the currently stored time integration ⁇ (dv_duty ⁇ pump_duty)_final, thereby determining the current time integration ⁇ (dv_duty ⁇ pump_duty)_final, then updates the stored value.
  • step S 7 when the time integration ⁇ (dv_duty ⁇ pump_duty) is calculated in step S 7 , the process returns to step S 4 again to repeat the previous steps. Then, when the time integration ⁇ dv_duty of the injection valve duty ratio DV_duty reaches the determination start value ⁇ dv_duty_thre, it is determined to be NO in step S 4 and the process proceeds to step S 8 .
  • step S 8 the control processing unit 40 performs abnormality determination based on the time integration ⁇ (dv_duty ⁇ pump_duty)_final.
  • FIG. 7 is a flowchart specifically showing the process of abnormality determination performed in step S 8 .
  • step S 21 the control processing unit 40 determines whether or not the time integration ⁇ (dv_duty ⁇ pump_duty)_final exceeds the upper threshold Thre_max. If YES in step S 21 , the control processing unit 40 determines in step S 22 that an abnormality causing the excessive injection amount condition has occurred in the reducing agent supply apparatus 20 , then proceeds to step S 25 .
  • step S 21 the process proceeds to step S 23 in which the control processing unit 40 determines whether or not the time integration ⁇ (dv_duty ⁇ pump_duty)_final is below the lower threshold Thre_min. If YES in step S 23 , the control processing unit 40 determines in step S 24 that an abnormality causing the insufficient injection amount condition has occurred in the reducing agent supply apparatus 20 , then proceeds to step S 25 . On the other hand, if NO in step S 23 , 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.
  • step S 22 When it is determined in step S 22 that an abnormality causing the excessive injection amount condition has occurred or when it is determined in step S 24 that an abnormality causing the insufficient injection amount condition has occurred, the control processing unit 40 , in step S 25 , 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.
  • 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.
  • 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 ⁇ 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.
  • 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.
  • 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 .
  • the abnormality determination method implemented by the abnormality determiner 49 is different from that of the abnormality diagnosis unit of the first 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 ⁇ dv_duty of the injection valve duty ratio to the time integration ⁇ pump_duty of the difference ⁇ pump_duty between the pump duty ratio Pump_duty and the reference duty Pump_duty_default.
  • 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 ⁇ dv_duty of the injection valve duty ratio, the time-integration ⁇ pump_duty of the difference of pump duty ratio, and the time-integration ⁇ dv_duty of the injection valve duty ratio divided by the time-integration ⁇ pump_duty of the difference of pump duty ratio.
  • the changes in the pump duty ratio Pump_duty, the time integration ⁇ dv_duty of the injection valve duty ratio and the time integration ⁇ 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 .
  • 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).
  • 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).
  • the time integration ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ pump_duty of the difference of pump duty ratio is, as shown by the broken line, smaller than that in normal state (solid line).
  • the time integration ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ 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).
  • the reducing agent supply apparatus 20 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 ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ 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.
  • the determination is performed using the time integrations ⁇ dv_duty, ⁇ 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 ⁇ dv_duty reaches a determination start value ⁇ dv_duty_thre.
  • control processing unit 40 starts injection control of reducing agent, then, in step S 32 , resets the currently stored time integrations ⁇ dv_duty, ⁇ pump_duty.
  • step S 33 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.
  • step S 34 the control processing unit 40 determines whether or not the time integration ⁇ dv_duty of the injection valve duty ratio DV_duty is less than the determination start value ⁇ dv_duty_thre. If YES in step S 34 , it is determined that the precise abnormality determination is not ready, so the process does not proceed to step S 38 for performing abnormality determination, but proceeds to step S 35 .
  • step S 35 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.
  • 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.
  • step S 35 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 S 34 with no particular action. On the other hand, if YES in step S 35 , the control processing unit 40 , in step S 36 , calculates the time integration ⁇ dv_duty of the injection valve duty ratio DV_duty, then in step S 37 , calculates the time integration ⁇ pump_duty of the difference of pump duty ratio ⁇ pump_duty.
  • step S 36 When the time integrations ⁇ dv_duty, ⁇ pump_duty are calculated in step S 36 and step S 37 , the process returns to step S 34 again to repeat the previous steps. Then, when the time integration ⁇ dv_duty of the injection valve duty ratio DV_duty reaches the determination start value ⁇ dv_duty_thre, it is determined to be NO in step S 34 and the process proceeds to step S 38 .
  • step S 38 the control processing unit 40 performs abnormality determination based on the time integration ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ pump_duty of the difference of pump duty ratio.
  • FIG. 10 is a flowchart specifically showing the process of abnormality determination performed in step S 38 .
  • step S 41 the control processing unit 40 determines whether or not the time integration ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ pump_duty of the difference of pump duty ratio is below the lower threshold Thre_min. If YES in step S 41 , the control processing unit 40 determines in step S 42 that an abnormality causing the insufficient injection amount condition has occurred in the reducing agent supply apparatus 20 , then proceeds to step S 45 .
  • step S 41 the control processing unit 40 determines in step S 43 whether or not the time integration ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ pump_duty of the difference of pump duty ratio exceeds the upper threshold Thre_max. If YES in step S 43 , the control processing unit 40 determines in step S 44 that an abnormality causing the excessive injection amount condition has occurred in the reducing agent supply apparatus 20 , then proceeds to step S 45 . On the other hand, if NO in step S 43 , 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.
  • step S 42 When it is determined in step S 42 that an abnormality causing the insufficient injection amount condition has occurred or when it is determined in step S 44 that an abnormality causing the excessive injection amount condition has occurred, the control processing unit 40 , in step S 45 , 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.
  • 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.
  • abnormality determination is performed using the time integration ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ 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.
  • 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.
  • map information or the like needs to be previously stored so that a determination threshold is selected depending on the time integration ⁇ dv_duty of the injection valve duty ratio DV_duty when that period elapses.
  • the time integration ⁇ dv_duty of the injection valve duty ratio divided by the time integration ⁇ pump_duty of the difference of pump duty ratio is compared with a determination threshold, but the time integration ⁇ pump_duty of the difference of pump duty ratio divided by the time integration ⁇ dv_duty of the injection valve duty ratio may also be compared with a determination threshold.

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