DESCRIPTION
DPF REGENERATION CONTROL DEVICE
TECHNICAL FIELD
5 [0001] The present disclosure relates to a DPF regeneration control device used for an
exhaust gas processing device of a diesel engine, the exhaust gas processing device including
a diesel oxidation catalyst (DOC) disposed in an exhaust channel and a diesel particulate filter
(DPF) disposed on the downstream side of the DOC.
10 BACKGROUND ART
[0002] A diesel engine is equipped with an exhaust gas processing device including a
diesel oxidation catalyst (DOC) disposed in an exhaust channel and a diesel particulate filter
(DPF) disposed on the downstream side of the DOC. A diesel particulate filter (DPF) is a
device for collecting particulate matters (PM) contained in exhaust gas discharged from the
15 diesel engine. A DPF is normally formed of ceramic or the like in a honeycomb-shaped
monolith with adjacent vents closed alternately on an inlet side and an outlet side so that
exhaust gas passes through filtering walls, which remove PM. A DPF may support a catalyst.
Accumulation of PM in a DPF eventually brings about clogging, which leads to not only a
decrease in the PM-collecting performance of the DPF but also to an increase in an exhaust
20 pressure and thus has a negative effect on fuel efficiency. Thus, it is necessary to perform
forced regeneration to remove PM accumulated on the DPF every time when a PMaccumulation
amount reaches a predetermined amount or when an engine operation time
reaches a predetermined period.
[0003] Forced regeneration of a DPF is performed by forcedly increasing the inlet
25 temperature of the DPF. In general, the inlet temperature of a DPF is forcedly increased by
supplying non-combusted fuel to an exhaust-gas processing device by post injection, which is
to inject fuel after a main-combustion injection timing, and oxidizing the non-combusted fuel
with a diesel oxidization catalyst (DOC) so that the temperature of the non-combusted fuel
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increases. Further, combustion may be supplied by exhaust-duct injection to an exhaust
channel on the downstream side of the engine. A DOC is normally formed of ceramic or the
like in a honeycomb-shaped monolith, similarly to the above described DPF, and supports an
oxidization catalyst on the inner surface of the DOC.
5 [0004] In such an exhaust-gas post treatment device, if a state with a low operation load
and a low exhaust-gas temperature continues, SOF or soot of non-combusted fuel or the like
adheres to an upstream end surface of the DOC, and clogging of the DOC gradually
progresses. If the DOC gets clogged, the exhaust pressure increases and the fuel efficiency
decreases, and the non-combusted fuel is not sufficiently oxidized by the DOC in the forced
10 regeneration and slips. In response, more and more non-combusted fuel is supplied to the
DOC to increase the inlet temperature of the DPF to a predetermined temperature, thereby
deteriorating fuel efficiency. Further, the slipped fuel is oxidized and heated by the DPF
supporting a catalyst, and thus promotes abnormal combustion of the PM, thereby raising a
risk of heat damage to the DPF. Further, if the temperature is increased by late post
15 injection, the post injection amount increases and a risk of oil dilution increases in
accordance.
[0005] To prevent such clogging of the DOC, Patent Document 1 discloses a technique,
with an exhaust-gas purification device for a diesel engine, to calculate an adhering amount of
non-combusted fuel adhering to the surface of the DOC, reduce the opening degree of an
20 intake throttle if the calculated adhering amount of the non-combusted fuel is greater than a
predetermined value to increase the exhaust-gas temperature by decreasing the air excess
ratio, and promote oxidization removal of HC adhering to the surface of the DOC.
[0006] Further, Patent Document 2 discloses a technique to combust and remove noncombusted
fuel adhering to a surface of a DOC by maintaining an exhaust-gas temperature at
25 a predetermined temperature with an exhaust-gas temperature maintaining unit after
completion of a regeneration process of a DPF in a diesel engine.
Citation List
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Patent Literature
[0007]
Patent Document 1: JP2011-69323A
Patent Document 2: 2012-127297A
5
SUMMARY
Problems to be Solved
[0008] However, the above described Patent Document 1 does not disclose a relationship
between the process of removing non-combusted fuel adhering to a surface of a DOC and
10 normal forced regeneration of a DPF. In the first place, non-combusted fuel that adheres to a
surface of a DOC mostly comes from post injection or exhaust-duct injection in forced
regeneration of a DPF. Thus, to remove non-combusted fuel adhering to a surface of a DOC
efficiently, it is necessary to control removal of the non-combusted fuel adhering to the
surface of the DOC and forced regeneration of a DPF in a unified manner.
15 [0009] Further, the technique disclosed in the above described Patent Document 2 is to
maintain the exhaust gas temperature at a predetermined temperature always after completion
of forced regeneration regardless of the clogging condition of a DOC, to remove noncombusted
fuel adhering to the DOC. With this technique, the exhaust-gas temperature is
maintained at a predetermined temperature even if there is substantially no risk of clogging of
20 the DOC, and thus energy may be unnecessarily consumed. Further, Patent Document 2
does not mention any measure to be taken after clogging of the DOC has actually taken place.
[0010] At least one embodiment of the present invention was made in view of the above
conventional problem, and an object of the at least one embodiment of the present invention is
to provide a DPF regeneration control device whereby it is possible to prevent clogging of a
25 DOC more efficiently than conventional techniques, and to recover the DOC securely from a
clogging condition even if the DOC is actually clogged.
Solution to the Problems
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[0011] According to at least one embodiment of the present invention, a DPF
regeneration control device, provided for an exhaust-gas processing device of a diesel engine,
the exhaust-gas processing device including a DOC disposed in an exhaust channel and a DPF
disposed on a downstream side of the DOC, for controlling execution of forced regeneration
5 of heating the DPF to remove PM which accumulates on the DPF, the forced regeneration
comprising automatic regeneration automatically executed if a predetermined forcedregeneration
execution condition is satisfied, and manual regeneration executed by manual
operation to heat the DPF to a higher temperature than in the automatic regeneration,
comprises: a DPF temperature-increase unit including a first temperature-increase unit
10 configured to heat the DPF to a predetermined temperature, and a second temperatureincrease
unit configured to heat the DPF to a temperature higher than the predetermined
temperature in cooperation with the first temperature-increase unit; a DOC clogging detection
unit configured to detect that the DOC is clogged if a clogging parameter detected during
execution of the automatic regeneration exceeds a clogging threshold value determined in
15 advance for a predetermined period, the clogging parameter being related to clogging of the
DOC; and a DOC clogging countermeasure unit configured to stop the automatic regeneration
and issue an alert to prompt execution of the manual regeneration, if the clogging of the DOC
is detected.
[0012] The above DPF regeneration control device includes the DOC clogging detection
20 unit for detecting clogging of the DOC during the automatic regeneration. If clogging of the
DOC is detected during the automatic regeneration, the automatic regeneration is stopped and
an operator or the like of the diesel engine is prompted by an alert to execute the manual
regeneration, which is to increase the temperature of the DPF higher than that in the automatic
regeneration. Thus, it is possible to recover the DOC from clogging securely even if the
25 DOC is clogged.
[0013] In some embodiments, the DPF regeneration control device further comprises: a
DOC clogging initial stage detection unit configured to detect that the DOC is in an initial
stage of the clogging if the clogging parameter detected during execution of the automatic
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regeneration is not greater than the clogging threshold value and greater than a second
clogging threshold value smaller than the clogging threshold value for a predetermined period,
or if the clogging parameter is not greater than the clogging threshold value and a change
amount of the clogging parameter is greater than a change-amount threshold value set in
5 advance for a predetermined period; and a DOC clogging initial stage countermeasure unit
configured to operate the first temperature-increase unit for a predetermined period after
completion of the automatic regeneration if the DOC is detected to be in the initial stage of
the clogging.
[0014] The above DPF regeneration control device includes the DOC clogging initial
10 stage detection unit for detecting the clogging initial stage of the DOC during the automatic
regeneration. Then, if the clogging initial stage of the DOC is detected during the automatic
regeneration, the first temperature-increase unit is executed for a predetermined period after
completion of the automatic regeneration.
With the above DPF regeneration control device, the temperature of the DOC is
15 increased by the first temperature-increase unit only if the clogging initial stage of the DOC is
detected. If the clogging initial stage of the DOC is not detected, the temperature of the
DOC is not increased by the first temperature-increase unit. In this way, it is possible to
prevent clogging of the DOC more efficiently than conventional techniques.
[0015] In some embodiments, the DPF regeneration control device further comprises: a
20 DOC clogging dangerous state detection unit configured to detect that the DOC is in a
clogging dangerous state if the diesel engine is under an operation state in which clogging of
the DOC is likely to occur during normal operation in which none of the forced regenerations,
which are the automatic regeneration and the manual regeneration, is executed; and a DOC
clogging dangerous state countermeasure unit configured to operate the first temperature25
increase unit for only a predetermined period if the DOC is detected to be in the clogging
dangerous state.
[0016] In the above embodiment, the DOC clogging dangerous state detection unit
detects that the DOC is in the clogging dangerous state if one or more of the following
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conditions are satisfied: the temperature of the exhaust gas is continuously not greater than a
predetermined temperature for a predetermined period or longer; the number of times per unit
time that the change rate of the engine rotation speed of the diesel engine exceeds a preset
rotation-speed threshold value continuously exceeds a threshold value for a predetermined
5 period or longer; or a mean value of a PM discharge-amount estimate value is continuously at
least a preset threshold value for a predetermined period or longer.
Herein, the change rate of the engine rotation speed is given by an expression of
(rotation speed after change - rotation speed before change) / Δt. Further, the ECU estimates
a PM discharge amount successively from the engine rotation speed, the fuel injection amount,
10 and the air flow rate, for instance, and a mean value per unit time of the estimate value of the
PM discharge amount can be used.
[0017] According to the above embodiment, the clogging dangerous state of the DOC is
detected from the operation state of the engine, and if it is detected that the DOC is in the
clogging dangerous state, the first temperature-increase unit increases the temperature of the
15 DOC. Thus, it is possible to prevent clogging of the DOC in advance during normal
operation.
[0018] In some embodiments, the first temperature-increase unit comprises at least one
of: a throttle valve control unit configured to control an opening degree of a throttle valve
disposed in an intake channel; an early post injection control unit configured to control a fuel
20 injection amount of early post injection of injecting fuel after a time of main combustion
injection, or a rail-pressure control unit configured to control a rail pressure at which the fuel
is injected, and the second temperature-increase unit comprises: a late post injection control
unit configured to control a fuel injection amount of late post injection of injecting fuel at a
timing which does not contribute to combustion in a combustion chamber after the early post
25 injection, or an exhaust-duct injection control unit configured to control a fuel injection
amount of exhaust-duct injection of injecting fuel to an exhaust channel on an engine
downstream side.
[0019] In some embodiments, the clogging parameter is set on the basis of a temperature
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difference between an inlet temperature of the DPF and an outlet temperature of the DPF.
[0020] If clogging of the DOC progresses, fuel is not sufficiently oxidized by the DOC
during forced regeneration, and the DPF inlet temperature does not sufficiently increase.
Further, the non-combusted fuel having slipped the DOC is combusted by the DPF at the
5 downstream side, and thus the DPF outlet temperature increases excessively. Thus, the
clogging parameter Pr1 can be set by the following equation (1), for instance, where Tp1 is
the inlet temperature of the DPF and Tp2 is the outlet temperature of the DPF. In this case,
the clogging parameter Pr1 increases with progress of clogging of the DOC.
Pr1 = (Tp2 - Tp1) (1)
10 [0021] According to the above embodiment, clogging of the DOC and the clogging initial
stage of the DOC can be detected by detecting the inlet temperature and the outlet temperature
of the DPF.
[0022] In some embodiments, the clogging parameter is set as an outlet temperature of the
DPF.
15 [0023] Specifically, if clogging of the DOC progresses, non-combusted fuel having
slipped the DOC is combusted by the DPF at the downstream side of the DOC, and thus the
DPF outlet temperature increases excessively, as described above. Thus, the clogging
parameter Pr2 can be set by the following equation (2), where Tp2 is the outlet temperature of
the DPF. In this case, the clogging parameter Pr2 increases with progress of clogging of the
20 DOC.
Pr2 = Tp2 (2)
[0024] According to the above embodiment, clogging of the DOC and the clogging initial
stage of the DOC can be detected by detecting the outlet temperature of the DPF.
[0025] In some embodiments, the clogging parameter is set on the basis of a temperature
25 difference between an outlet temperature and an inlet temperature of the DOC, a flow rate of
exhaust gas flowing through the DOC, and a fuel-injection amount of the late post injection or
the exhaust-duct injection.
[0026] If clogging of the DOC progresses, fuel injected by a late post injection unit or an
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exhaust-duct injection unit is not oxidized sufficiently by the DOC, and the calorific value of
the DOC with respect to the fuel injection amount decreases. Thus, the clogging parameter
Pr3 can be set by the following equation (3), where ΔTo is a temperature difference between
the outlet temperature and the inlet temperature of the DOC, Qe is the flow rate of exhaust gas
5 flowing through the DOC, and Qfe is the fuel injection amount of late post injection or
exhaust-duct injection. In this case, the clogging parameter Pr3 increases with progress of
clogging of the DOC.
Pr3 = Qfe / ΔTo ･ Qe (3)
[0027] According to the above embodiment, clogging of the DOC and the clogging initial
10 stage of the DOC can be detected by detecting the inlet temperature and the outlet temperature
of the DOC and the fuel injection amount of late post injection or exhaust-duct injection.
[0028] In some embodiments, the above clogging parameter is set on the basis of an
increasing speed of the inlet temperature of the DPF and an increasing speed of the inlet
temperature of the DPF in an initial state in which the DOC is not clogged.
15 [0029] If clogging of the DOC progresses, fuel is not sufficiently oxidized by the DOC,
and the increase speed of the DPF inlet temperature slows down. Thus, the clogging
parameter Pr4 can be set by the following equation (4), where Vt is an increase speed of the
inlet temperature of the DPF and Vt’ is an increase speed of the inlet temperature of the DPF
in an initial state in which the DOC is not clogged. In this case, the clogging parameter Pr4
20 increases with progress of clogging of the DOC.
Pr4 = Vt’ / Vt (4)
[0030] According to the above embodiment, clogging of the DOC and the clogging initial
stage of the DOC can be detected by having obtained in advance an increase speed of the DPF
inlet temperature in the initial state and detecting the increase speed of the DPF inlet
25 temperature.
The increase speed Vt of the DPF inlet temperature and the increase speed Vt’ of the
inlet temperature of the DPF in the initial state in the above embodiment are detected under
the same conditions which affect the increase speed, such as the fuel injection amount and the
Specification
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injection timing.
[0031] In some embodiments, the late post injection control unit or the exhaust-duct
injection control unit is configured to control a fuel injection amount so that an inlet
temperature of the DPF reaches a target temperature required to execute the forced
5 regeneration. Further, the clogging parameter is set: on the basis of a cumulative fuelinjection
amount of the late post injection or the exhaust-duct injection of injecting fuel while
an inlet temperature of the DPF increases by a predetermined temperature, and a cumulative
fuel-injection amount of the late post injection or the exhaust-duct injection of injecting fuel
while the inlet temperature of the DPF increases by the predetermined temperature in an
10 initial state in which the DOC is not clogged; or on the basis of a mean injection amount of
the late post injection or the exhaust-duct injection of injecting fuel in a stable state in which
the inlet temperature of the DPF has reached a target control temperature, and a mean
injection amount of the late post injection or the exhaust-duct injection of injecting fuel in a
stable state in which the inlet temperature of the DPF has reached a target control temperature
15 in an initial state in which the DOC is not clogged.
[0032] The late post injection control unit or the exhaust-duct injection control unit is
configured so as to control the fuel injection amount so that the inlet temperature of the DPF
reaches a target temperature required to execute forced regeneration. Thus, if clogging of
the DOC progresses and fuel is not sufficiently oxidized by the DOC with an insufficient
20 increase of the DPF inlet temperature, the late post injection control unit or the exhaust-duct
injection control unit performs a control to increase the fuel injection amount of the late post
injection or exhaust-duct injection. Accordingly, the clogging parameter Pr5 can be set by
the following equation (5) , for instance, where ΣQfl is a cumulative fuel-injection amount of
late post injection or exhaust-duct injection of injecting fuel while the inlet temperature of the
25 DPF increases by a predetermined temperature, and ΣQfl’ is a cumulative fuel-injection
amount of late post injection or exhaust-duct injection of injecting fuel while the DPF inlet
temperature increases by a predetermined temperature in an initial state in which the DOC is
not clogged. In this case, the clogging parameter Pr5 increases with progress of clogging of
Specification
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the DOC.
Pr5 = ΣQfl / ΣQfl’ (5)
[0033] Alternatively, a clogging parameter Pr5’ can be set by, for instance, the following
equation (5)’, where QgI is a mean fuel-injection amount of late post injection or exhaust-duct
5 injection of injecting fuel in a stable state in which the inlet temperature of the DPF has
reached a target control temperature, and Qgl’ is a mean fuel-injection amount of late post
injection or exhaust-duct injection of injecting fuel in a state in which the inlet temperature of
the DPF has reached a target control temperature in an initial state in which the DOC is not
clogged. In this case, the clogging parameter Pr5’ increases with progress of clogging of the
10 DOC.
Pr5’ = Qgl / Qgl’ (5)’
[0034] According to the above embodiment, clogging of the DOC and the clogging initial
stage of the DOC can be detected by having obtained in advance the cumulative fuel-injection
amount of late post injection or exhaust-duct injection of injecting fuel while the DPF inlet
15 temperature increases by a predetermined temperature in the initial state, and detecting the
cumulative amount of late post injection or exhaust-duct injection of injecting fuel while the
DPF inlet temperature increases by a predetermined temperature. Alternatively, it is possible
to detect clogging of the DOC and the initial stage of clogging of the DOC by detecting the
mean fuel-injection amount of late post injection or exhaust-duct injection of injection in a
20 stable state in which the inlet temperature of the DPF has reached a target control
temperature, and the mean injection amount of late post injection or exhaust-duct injection of
injection in a state in which the inlet temperature of the DPF has reached a target control
temperature in an initial state in which the DOC is not clogged.
Further, in the above embodiment, the above described ΣQfl, ΣQfl’, Qgl, and Qgl’ are
25 detected under the same conditions which affect the cumulative amount of late post injection
or exhaust-duct injection, such as a fuel-injection timing and an increase speed of the DPF
inlet temperature.
Specification
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Advantageous Effects
[0035] According to at least one embodiment of the present invention, it is possible to
provide a DPF regeneration control device whereby it is possible to prevent clogging of a
DOC more efficiently than conventional techniques, and to recover the DOC securely from
5 clogging even if the DOC is actually clogged.
BRIEF DESCRIPTION OF DRAWINGS
[0036] FIG. 1 is an overall configuration diagram of an exhaust-gas processing device for
a diesel engine according to an embodiment of the present invention.
10 FIG. 2 is a block diagram for describing functions of an ECU.
FIG. 3 is an explanatory diagram for describing late post injection of a DPF regeneration
control device.
FIG. 4 is a flowchart of a control flow of the DPF regeneration control device.
FIG. 5 is a graph showing temperature changes of DPF inlet and outlet temperatures and
15 DOC inlet and outlet temperatures during automatic regeneration.
FIG. 6 is a graph showing temperature changes of DPF inlet and outlet temperatures and
DOC inlet and outlet temperatures during an initial stage of the automatic regeneration.
DETAILED DESCRIPTION
20 [0037] Embodiments of the present invention will now be described in more detail with
reference to the accompanying drawings.
However, the scope of the present invention is not limited to the following embodiments.
It is intended that dimensions, materials, shapes, relative positions and the like of components
described in the embodiments shall be interpreted as illustrative only and not limitative of the
25 scope of the present invention.
[0038] FIG. 1 is an overall configuration diagram of an exhaust-gas processing device for
a diesel engine according to an embodiment of the present invention.
As illustrated in FIG. 1, an exhaust channel 21 is connected to the downstream side of a
Specification
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diesel engine 1. An exhaust-gas processing device 33 is disposed in the exhaust channel 21,
the exhaust-gas processing device 33 including a diesel oxidation catalyst (DOC) 35 and a
diesel particulate filter (DPF) 37 disposed on the downstream side of the DOC 35. The
DOC 35 has a function to oxidize and remove non-combusted fuel (HC) and carbon
5 monoxide (CO) in exhaust gas and to oxidize nitrogen monoxide (NO) in exhaust gas to
produce nitrogen dioxide (NO2). Further, the DOC 35 increases the temperature of passing
exhaust gas with oxidation heat of injected fuel to increase the inlet temperature of the DPF
37. The DPF 37 is a device which collects particulate matters (PM), such as soot, contained
in exhaust gas with a filter to remove the particulate matters from exhaust gas.
10 [0039] Further, an intake channel 9 is connected to the upstream side of the diesel engine
1 via an intake manifold 13. An exhaust turbocharger 7 is disposed between the intake
channel 9 and the exhaust channel 21. The exhaust turbocharger 7 includes an exhaust
turbine 3 disposed in the exhaust channel 21 and a compressor 5 disposed in the intake
channel 9, and the compressor 5 is configured to be driven coaxially with the exhaust turbine
15 3. Further, an inter cooler (not depicted) and the throttle valve 11 are disposed in the intake
channel 9. The opening degree of the throttle valve 11 is controlled by an ECU 10 described
below. Then, the inter cooler cools compressed intake air discharged from the compressor 5,
the throttle valve 11 controls the intake flow rate of the compressed intake air, and the
compressed intake air flows into the combustion chamber 39 of each cylinder of the diesel
20 engine 1 via an intake port 15.
[0040] Further, the diesel engine 1 includes a fuel injection valve 19 for injecting a highpressure
fuel to the combustion chamber 39. The fuel injection valve 19 is connected to a
common rail (not depicted) accumulating a high-pressure fuel, and the ECU 10 described
below controls the injection timing and the fuel injection amount of the fuel injection valve 19.
25 The high-pressure fuel injected into the combustion chamber 39 is mixed with the above
described intake air and combusted in the combustion chamber 39.
[0041] Further, the EGR duct 23 branches from the exhaust channel 21 at a position
immediately downstream an exhaust port 29 disposed in the exhaust channel 21. The EGR
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duct 23 is connected to the intake manifold 13 disposed on the downstream side of the throttle
valve 11. An EGR valve 25 is disposed in the EGR duct 23, and is controlled so that a part
of exhaust gas discharged from the diesel engine 1 flows through the EGR duct 23 to
recirculate in the diesel engine 1.
5 [0042] The exhaust gas discharged from the diesel engine 1 drives the above described
exhaust turbine 3 to drive the compressor 5 coaxially. Then, after flowing through the
exhaust channel 21, the exhaust gas flows into the DOC 35 and the DPF 37 of the above
described exhaust-gas processing device 33. The exhaust gas having flowed into the
exhaust-gas processing device 33 is discharged outside the engine after oxidative removal of
10 non-combusted fuel (HC) and carbon monoxide (CO) in the exhaust gas by the DOC 35 and
removal of particulate matters (PM) in the exhaust gas by the DPF 37.
[0043] While a part of PM removed by the DPF 37 is combusted by high-temperature
exhaust gas discharged from the engine in operation (natural regeneration), the rest of PM is
accumulated on the filter of the DPF. Excessive accumulation of PM may bring about a
15 decrease in the PM collecting performance and a decrease in the engine output, for instance.
Thus, for the exhaust-gas processing device 33 including the DPF 37, forced regeneration
needs to be performed at an appropriate timing to combust PM accumulating on the filter
forcedly to regenerate the filter.
[0044] There are at least two types of forced regeneration: automatic regeneration
20 executed automatically by the ECU 10; and manual regeneration executed manually by an
operator. The automatic regeneration is automatically executed if predetermined forcedregeneration
execution conditions are met, regardless of whether a vehicle is moving or
standing. In contrast, the manual regeneration is executed by, for instance, button operation
of an operator or the like, basically while a vehicle is standing. Thus, the regeneration
25 temperature is high in the manual regeneration than in the automatic regeneration. For
example, the inlet temperature of the DPF 37 is 600 to 610°C in the automatic regeneration,
and is 620 to 630°C in the manual regeneration.
[0045] Various sensors are disposed in the exhaust channel 21, the sensors including a
Specification
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DOC inlet temperature sensor 48, a DPF inlet temperature sensor 49, a DPF outlet
temperature sensor 50, a DPF inlet pressure sensor 52, a DPF outlet pressure sensor 54, and a
DPF differential-pressure sensor 56. Signals related to the DOC inlet temperature, the DPF
inlet temperature, the DPF outlet temperature, the DPF differential pressure measured by the
5 above sensors are inputted to the ECU 10.
[0046] The ECU 10 is configured as a microcomputer including a central processing unit
(CPU), a random access memory (RAM), a read only memory (ROM), and an I/O interface.
[0047] FIG. 2 is a block diagram for describing functions of an ECU.
As illustrated in FIG. 2, the ECU 10 of the present embodiment is configured as a DPF
10 regeneration control device 10 for controlling a regeneration process of the DPF 37, the DPF
regeneration control device 10 at least including a DPF temperature-increase unit 10A, an
automatic regeneration execution unit 10B, a DOC clogging countermeasure unit 10C, a DOC
clogging detection unit 10D, a DOC clogging initial stage countermeasure unit 10E, and a
DOC clogging initial stage detection unit 10F.
15 [0048] The DPF temperature-increase unit 10A includes the first temperature-increase
unit 12 which increases the temperature of the DPF 37 to a predetermined temperature, and
the second temperature-increase unit 14 which increases the temperature of the DPF 37 to a
temperature higher than the predetermined temperature in cooperation with the first
temperature-increase unit 12. The first temperature-increase unit 12 includes at least one of
20 a throttle valve control unit 12a for controlling the opening degree of the throttle valve 11, an
early post injection control unit 12b for controlling the fuel injection amount of early post
injection, and a common-rail pressure control unit 12c for controlling a common-rail pressure
at which fuel is injected. The second temperature-increase unit 14 includes a late post
injection control unit 14 for controlling the fuel injection amount of late post injection, which
25 is to inject fuel after the early post injection. Further, instead of or in addition to the late post
injection control unit 14, the second temperature-increase unit 14 may comprise an exhaustduct
injection control unit 14 for controlling the fuel injection amount injected into the
exhaust channel 21 from an exhaust-duct injection valve 24 disposed between the turbine 3 of
Specification
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the exhaust turbocharger 7 and the downstream side of the branching position of the EGR
duct 23.
[0049] FIG. 3 is an explanatory diagram for describing late post injection of a DPF
regeneration control device. Early post injection is the first-time post injection of injecting a
5 smaller amount of fuel than main injection while the pressure in the combustion chamber 39
is still high immediately after injection of the main fuel. The early post injection makes it
possible to increase the exhaust-gas temperature without affecting the output of the diesel
engine 1. The DOC 35 can be activated by the heated exhaust gas flowing into the DOC 35.
[0050] The late post injection is the second-time post injection of injecting fuel at a
10 timing (in the vicinity of the bottom dead center) that does not contribute to combustion
inside the combustion chamber 39 after the above described early post injection. The late
post injection causes non-combusted fuel to flow out from the combustion chamber 39 into
the exhaust channel 21, and the discharged non-combusted fuel is oxidized by the DOC 35 to
increase the temperature of the DPF 37, thereby combusting the PM accumulated on the DPF
15 37.
[0051] The automatic regeneration execution unit 10B is configured to execute the
automatic regeneration with the above described DPF temperature-increase unit 10A
automatically, if the forced regeneration execution conditions for the automatic regeneration
are met. The forced regeneration execution conditions for the automatic regeneration may
20 include, for instance: an estimate value of the PM accumulation amount on the DPF 37
exceeds a predetermined value; the operation time of the diesel engine 1 exceeds a
predetermined period; or the cumulative of the fuel injection amount of the diesel engine 1
exceeds a predetermined amount. The PM accumulation amount on the DPF 37 can be
estimated by detecting a differential pressure between the upstream and downstream sides of
25 the DPF 37 with the DPF differential-pressure sensor 56, for instance. Further, the PM
accumulation amount can be also estimated by detecting the engine rotation speed, the fuel
injection amount, the air flow rate, and the DPF temperature, estimating a PM regeneration
amount inside the DPF and a PM discharge amount from the diesel engine 1 on the basis of a
Specification
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map stored in advance in the ECU 10, and subtracting the PM regeneration amount from the
PM discharge amount.
[0052] The DOC clogging countermeasure unit 10C is configured to stop the above
automatic regeneration and to issue an alert to prompt an operator or the like of the diesel
5 engine 1 to execute the manual regeneration, if clogging of the DOC 35 is detected. The
DOC clogging detection unit 10D detects clogging of the DOC 35. The DOC clogging
detection unit 10D detects that the DOC 35 is clogged if a clogging parameter related to
clogging of the DOC 35 described below detected during execution of the automatic
regeneration is greater than a clogging threshold value determined in advance.
10 [0053] The DOC clogging initial stage countermeasure unit 10E is configured to continue
operation of only the first temperature-increase unit 12 without stopping operation of the
second temperature-increase unit 14 after completion of the automatic regeneration, if no
clogging of the DOC 35 is detected but the the DOC 35 is detected to be in the initial stage of
clogging. The initial stage of clogging of the DOC 35 is detected by the DOC clogging
15 initial stage detection unit 10F. The DOC clogging initial stage detection unit 10F detects
that the DOC 35 is in the initial stage of clogging if a clogging parameter, which will be
described below, detected during execution of the automatic regeneration is not greater than a
clogging threshold value set in advance and is greater than the second clogging threshold
value smaller than the clogging threshold value, or, if the clogging parameter described below
20 is not greater than the clogging threshold value set in advance and a change amount of the
clogging parameter is greater than a change-amount threshold value set in advance.
[0054] For instance, the DOC clogging detection unit 10D detects clogging of the DOC
35 if a relationship of ΔTp > 70°C is satisfied, where the clogging parameter is a DPF inletoutlet
temperature difference ΔTp, the clogging threshold value is 70°C, the second clogging
25 threshold value is 30°C, and the change-amount threshold value is 10°C. Also, the DOC
clogging initial stage detection unit 10F detects that the DOC 35 is in the initial stage of
clogging if a relationship of 70°C > ΔTp > 30°C is satisfied. Also, the DOC clogging initial
stage detection unit 10F detects that the DOC 35 is in the initial stage of clogging if a
Specification
- 18-
relationship of 70°C > ΔTp and a relationship of dΔTp / dt > 10°C are satisfied.
[0055] FIG. 4 is a flowchart of a control flow of the DPF regeneration control device.
In the drawings, it is firstly determined whether the automatic regeneration is being
executed (step 1). If the automatic regeneration is being executed (step 2), the DOC
5 clogging detection unit 10D detects whether the DOC 35 is clogging (step 3). In contrast, if
the automatic regeneration is not being executed, it is determined that the normal operation is
being performed (step 9), and the process advances to step 10 described below.
[0056] If clogging of the DOC 35 is detected in step S3, the DOC clogging
countermeasure unit 10C suspends the automatic regeneration (step S4), and issues an alert to
10 an operator or the like of the diesel engine 1 to prompt execution of the manual regeneration
(step 5).
[0057] If clogging of the DOC 35 is not detected in step 3, the automatic regeneration is
continued (step S6). Then, the DOC clogging initial stage detection unit 10F detects
whether the DOC 35 is in the clogging initial stage (step S7). If it is detected that the DOC
15 35 is in the clogging initial stage, the DOC clogging initial stage countermeasure unit 10E
continues to operate only the first temperature-increase unit 12 for a predetermined period
after completion of the automatic regeneration (step 8). In contrast, if it is detected that the
DOC 35 is not in the clogging initial stage, operation of the first temperature-increase unit 12
is ended after completion of the automatic regeneration.
20 [0058] FIG. 5 is a graph showing temperature changes of DPF inlet and outlet
temperatures and DOC inlet and outlet temperatures during automatic regeneration. FIG. 5A
is a temperature graph of a case where only the first temperature-increase unit 12 is operated
continuously for a predetermined period after completion of the automatic regeneration, and
FIG. 5B is a temperature graph of a case where operation is ended for both of the first
25 temperature-increase unit 12 and the second temperature-increase unit 14 simultaneously with
completion of the automatic regeneration.
As indicated by the reference sign (A) in FIG. 5A, after completion of the automatic
regeneration, if only the first temperature-increase unit 12 is operated for a predetermined
Specification
- 19-
period, the DOC inlet temperature is maintained to be high for a predetermined period also
after completion of the automatic regeneration. In this way, it is possible to remove noncombusted
fuel adhering to the upstream end surface of the DOC 35 by late post injection
(exhaust-duct injection) during the automatic regeneration.
5 [0059] The DPF regeneration control device (ECU) 10 of the diesel engine 1 according to
an embodiment of the present invention with the above configuration includes the DOC
clogging detection unit 10D for detecting clogging of the DOC 35 during the automatic
regeneration. If clogging of the DOC 35 is detected during the automatic regeneration, the
automatic regeneration is stopped and an operator or the like of the diesel engine 1 is
10 prompted by an alert to execute the manual regeneration, which is to increase the temperature
of the DPF 37 higher than that in the automatic regeneration. Thus, it is possible to recover
the DOC 35 from clogging securely even if the DOC 35 is clogged.
[0060] Further, the DPF regeneration control device 10 includes the DOC clogging initial
stage detection unit 10F for detecting the clogging initial stage of the DOC 35 during the
15 automatic regeneration, as described above. Then, if the clogging initial stage of the DOC
35 is detected during the automatic regeneration, the first temperature-increase unit 12 is
operated for a predetermined period after completion of the automatic regeneration. Thus,
the temperature of the DOC 35 is increased by the first temperature-increase unit 12 only if
the clogging initial stage of the DOC 35 is detected. If the clogging initial stage of the DOC
20 35 is not detected, the temperature increase of the DOC 35 by the first temperature-increase
unit 12 is ended at the same time as completion of the automatic regeneration. In this way, it
is possible to prevent clogging of the DOC 35 more efficiently than conventional techniques.
[0061] In some embodiments, as illustrated in FIG. 2, the above described DPF
regeneration control device 10 further includes a DOC clogging dangerous state
25 countermeasure unit 10G and a DOC clogging dangerous state detection unit 10H.
[0062] The DOC clogging dangerous state countermeasure unit 10G is configured to
operate only the first temperature-increase unit 12 without operating the second temperatureincrease
unit 14, if it is detected that the DOC 35 is under a clogging dangerous state.
Specification
- 20-
Whether the DOC 35 is in the clogging dangerous state is detected by the DOC clogging
dangerous state detection unit 10H. The DOC clogging dangerous state detection unit 10H
detects that the DOC 35 is in the clogging dangerous state if the diesel engine 1 is under an
operation condition which is likely to cause clogging of the DOC 35 during normal operation,
5 in which none of forced regenerations, the automatic regeneration or the manual regeneration,
is executed. Specifically, it is detected that the DOC 35 is in the clogging dangerous state if
one or more of the following conditions are met: the temperature of the exhaust gas is
continuously not greater than a predetermined temperature for a predetermined period or
longer; the number of times per unit time that the change rate of the engine rotation speed of
10 the diesel engine 1 exceeds a preset rotation-speed threshold value continuously exceeds a
threshold value for a predetermined period or longer; or a mean value of a PM dischargeamount
estimate value is continuously at least a preset threshold value for a predetermined
period or longer.
[0063] For instance, the clogging dangerous state of the DOC 35 is detected if the exhaust
15 gas temperature is continuously not greater than 250 °C for at least three hours, if the change
rate of the engine rotation speed exceeds a rotation-speed threshold value of 500rpm/sec more
times per unit time than the threshold value of 200 times per hour continuously for at least
three hours, or if the time mean value of the PM discharge amount estimate value calculated
by the ECU 10 is continuously at least a threshold value of 1.5g/h for at least three hours.
20 [0064] As illustrated in FIG. 4, in step S1, if it is determined that the automatic
regeneration is not performed, it is determined that the normal operation is being performed
(step 9), and the process advances to step 10. Then, the DOC clogging dangerous state
detection unit 10H detects whether the DOC 35 is in the clogging dangerous state (step S10).
If it is detected that the DOC 35 is in the clogging dangerous state, recovery operation is
25 performed in which the DOC clogging dangerous state countermeasure unit 10G continues to
operate only the first temperature-increase unit 12 for a predetermined period (step 11). In
this way, the exhaust gas temperature is increased by the first temperature-increase unit 12 for
a predetermined period, which makes it possible to remove soot or the like adhering to the
Specification
- 21-
upstream end surface of the DOC 35 under an operation condition which is likely to bring
about clogging of the DOC 35. In contrast, if it is detected that the DOC 35 is not in the
clogging dangerous state, the above recovery operation is not performed.
[0065] According to the above embodiment, the clogging dangerous state of the DOC 35
5 is detected from the operation state of the diesel engine 1, and if it is detected that the DOC 35
is in the clogging dangerous state, the first temperature-increase unit 12 increases the
temperature of the DOC 35. Thus, it is possible to prevent clogging of the DOC 35 in
advance during normal operation.
[0066] FIG. 6 is a graph showing temperature changes of DPF inlet and outlet
10 temperatures and DOC inlet and outlet temperatures during an initial stage of the automatic
regeneration.
In some embodiments, the above clogging parameter is set on the basis of the inlet
temperature of the DPF 37 and the outlet temperature of the DPF 37.
Specifically, if clogging of the DOC 35 progresses, fuel is not sufficiently oxidized by
15 the DOC 35, and the DPF inlet temperature does not sufficiently increase. Further, the noncombusted
fuel having slipped the DOC 35 is combusted by the DPF 37 at the downstream
side, and thus the DPF outlet temperature increases excessively. Thus, if clogging of the
DOC 35 progresses, in the temperature graph illustrated in FIG. 6, the temperature difference
(ΔTp) between the DPF outlet temperature and the DPF inlet temperature increases.
20 [0067] Thus, the clogging parameter Pr1 can be set by the following equation (1) as a
temperature difference between Tp1 and Tp2, where Tp1 is the inlet temperature of the DPF
37 and Tp2 is the outlet temperature of the DPF 37. In this case, the clogging parameter Pr1
increases with progress of clogging of the DOC 35.
Pr1 = (Tp2 - Tp1) (1)
25 [0068] According to the above embodiment, clogging of the DOC 35 and the clogging
initial stage of the DOC 35 can be detected by detecting the inlet temperature of the DPF 37
and the outlet temperature of the DPF37.
[0069] In some embodiments, the above clogging parameter is set as the outlet
Specification
- 22-
temperature of the DPF 37.
Specifically, if clogging of the DOC 35 progresses as described above, non-combusted
fuel having slipped the DOC 35 is combusted by the DPF 37 at the downstream side, and thus
the DPF outlet temperature increases excessively. Thus, the clogging parameter Pr2 can be
5 set by the following equation (2), where Tp2 is the outlet temperature of the DPF. In this
case, the clogging parameter Pr2 increases with progress of clogging of the DOC 35.
Pr2 = Tp2 (2)
[0070] According to the above embodiment, clogging of the DOC 35 and the clogging
initial stage of the DOC 35 can be detected by detecting the outlet temperature of the DPF 37.
10 [0071] In some embodiments, the clogging parameter is set on the basis of the
temperature difference between the outlet temperature and the inlet temperature of the DOC
35, the flow rate of exhaust gas flowing through the DOC 35, and the fuel injection amount of
late post injection (or exhaust-duct injection).
Specifically, if clogging of the DOC 35 progresses, fuel injected by late post injection
15 (exhaust-duct injection) is not oxidized sufficiently by the DOC 35, and the calorific value of
the DOC 35 with respect to the fuel injection amount decreases. Thus, the clogging
parameter Pr3 can be set by the following equation (3), where ΔTo is a temperature difference
between the outlet temperature and the inlet temperature of the DOC 35, Qe is the flow rate of
exhaust gas flowing through the DOC 35, and Qfe is the fuel injection amount of late post
20 injection (or exhaust-duct injection). In this case, the clogging parameter Pr3 increases with
progress of clogging of the DOC 35.
Pr3 = Qfe / ΔTo ･ Qe (3)
[0072] According to the above embodiment, clogging of the DOC 35 and the clogging
initial stage of the DOC 35 can be detected by detecting the inlet temperature and the outlet
25 temperature of the DOC 35, and the fuel injection amount of late post injection (or exhaustduct
injection).
[0073] In some embodiments, the above clogging parameter is set on the basis of an
increasing speed of the inlet temperature of the DPF 37 and an increasing speed of the inlet
Specification
- 23-
temperature of the DPF 37 in an initial state in which the DOC 35 is not clogged.
Specifically, if clogging of the DOC 35 progresses, fuel is not sufficiently oxidized by
the DOC 35, and the increase speed of the DPF inlet temperature slows down. Thus, the
clogging parameter Pr4 can be set by the following equation (4), where Vt is an increase
5 speed of the inlet temperature of the DPF 37 and Vt’ is an increase speed of the inlet
temperature (single-dotted chain line in FIG. 6) of the DPF 37 in an initial state in which the
DOC 35 is not clogged. In this case, the clogging parameter Pr4 increases with progress of
clogging of the DOC 35.
Pr4 = Vt’ / Vt (4)
10 [0074] According to the above embodiment, clogging of the DOC 35 and the clogging
initial stage of the DOC 35 can be detected by having obtained in advance the increase speed
of the DPF inlet temperature in the initial state and detecting the increase speed of the DPF
inlet temperature.
The increase speed Vt of the DPF inlet temperature and the increase speed Vt’ of the
15 inlet temperature of the DPF in the initial state in the above embodiment are detected under
the same conditions which affect the increase speed, such as the fuel injection amount and the
injection timing.
[0075] In some embodiments, the above described late post injection control unit (or
exhaust-duct injection control unit ) 14 are configured so as to control the fuel injection
20 amount so that the inlet temperature of the DPF 37 reaches the target temperature required to
execute forced regeneration. The above described clogging parameter is set on the basis of:
the cumulative fuel-injection amount of late post injection (or exhaust-duct injection) of
injecting fuel while the inlet temperature of the DPF 37 increases by a predetermined
temperature, and the cumulative fuel-injection amount of late post injection (or exhaust-duct
25 injection) of injecting fuel while the DPF inlet temperature increases by a predetermined
temperature in an initial state in which the DOC 35 is not clogged; or the mean injection
amount of late post injection (or exhaust-duct injection) of injection in a stable state in which
the inlet temperature of the DPF 37 has reached a target control temperature, and the mean
Specification
- 24-
injection amount of late post injection (or exhaust-duct injection) of injection in a stable state
in which the inlet temperature of the DPF 37 has reached a target control temperature in an
initial state in which the DOC 35 is not clogged.
[0076] Specifically, the late post injection control unit (or exhaust-duct injection control
5 unit ) 14 are configured to control the fuel injection amount so that the inlet temperature of the
DPF 37 reaches a target temperature required to execute forced regeneration. Thus, if
clogging of the DOC 35 progresses and the fuel is not sufficiently oxidized by the DOC 35
with an insufficient increase of the DPF inlet temperature, the late post injection control unit
(or exhaust-duct injection control unit) 14 performs a control to increase the late post injection
10 amount (or exhaust-duct injection amount). Accordingly, the clogging parameter Pr5 can be
set by, for instance, the following equation (5), where ΣQfl is the cumulative fuel-injection
amount of late post injection (exhaust-duct injection) of injecting fuel while the inlet
temperature of the DPF 37 increases by a predetermined temperature, and ΣQfl’ is the
cumulative fuel-injection amount of late post injection (or exhaust-duct injection) of injecting
15 fuel while the DPF inlet temperature increases by a predetermined temperature in an initial
state in which the DOC 35 is not clogged. In this case, the clogging parameter Pr5 increases
with progress of clogging of the DOC 35.
Pr5 = ΣQfl / ΣQfl’ (5)
[0077] Alternatively, the clogging parameter Pr5’ can be set by, for instance, the
20 following equation (5)’, where QgI is the mean fuel-injection amount of late post injection
(exhaust-duct injection) of injection in a stable state in which the inlet temperature of the DPF
37 has reached a target control temperature, and Qgl’ is the mean fuel-injection amount of late
post injection (or exhaust-duct injection) of injection in a state in which the inlet temperature
of the DPF 37 has reached a target control temperature in an initial state in which the DOC 35
25 is not clogged. In this case, the clogging parameter Pr5’ increases with progress of clogging
of the DOC 35.
Pr5’ = Qgl / Qgl’ (5)’
[0078] According to the above embodiment, clogging of the DOC 35 and the clogging
Specification
- 25-
initial stage of the DOC 35 can be detected by having obtained in advance the cumulative
fuel-injection amount of late post injection (or exhaust-duct injection) of injecting fuel while
the DPF inlet temperature increases by a predetermined temperature in the initial state, and
detecting the cumulative amount of late post injection (or exhaust-duct injection) of injecting
5 fuel while the DPF inlet temperature increases by a predetermined temperature.
Further, in the above embodiment, the above described ΣQfl, ΣQfl’, Qgl, and Qgl’ are
detected under the same conditions which affect the cumulative amount of late post injection
or exhaust-duct injection, such as the fuel-injection timing and the increase speed of the DPF
inlet temperature.
10 [0079] In some embodiments, the above described clogging threshold value and the
second clogging threshold value are set so as to increase with thermal deterioration of the
DOC 35.
If thermal deterioration progresses in the DOC 35, the oxidization performance
deteriorates, thus affecting the value of the clogging parameter to become larger. Thus,
15 according to the above embodiment, clogging of the DOC 35 and the clogging initial stage of
the DOC 35 can be detected accurately regardless of the thermal deterioration of the DOC 35
by setting the clogging threshold value taking account of the influence of the thermal
deterioration of the DOC 35.
[0080] The embodiments of the present invention have been described above. However,
20 the present invention is not limited thereto. For instance, various modifications may be
applied as long as they do not depart from the object of the present invention.
Industrial Applicability
[0081] At least one embodiment of the present invention can be suitably used as a DPF
25 regeneration control device for an exhaust-gas processing device of a diesel engine, in an
engine not only for automobiles but also for ships and the industrial use.
Description of Reference Numerals
Specification
- 26-
[0082]
1 Diesel engine
3 Exhaust turbine
5 Compressor
5 7 Exhaust turbocharger
9 Intake channel
10 ECU (DPF regeneration control device)
10A DPF temperature-increase unit
10B Automatic regeneration execution unit
10 10C DOC clogging countermeasure unit
10D DOC clogging detection unit
10E DOC clogging initial stage countermeasure unit
10F DOC clogging initial stage detection unit
10G DOC clogging dangerous state countermeasure unit
15 10H DOC clogging dangerous state detection unit
11 Throttle valve
12 First temperature-increase unit
12a Throttle valve control unit
12b Early post injection control unit
20 12c Common-rail pressure control unit
13 Intake manifold
14 Second temperature-increase unit (late post injection control unit or exhaust-duct
injection control unit)
15 Intake port
25 19 Fuel injection valve
21 Exhaust channel
23 EGR duct
24 Exhaust-duct injection valve
Specification
- 27-
25 EGR valve
29 Exhaust port
33 Exhaust-gas processing device
35 DOC (diesel oxidization catalyst)
5 37 DPF (diesel particulate filter)
39 Combustion chamber
48 DOC inlet temperature sensor
49 DPF inlet temperature sensor
50 DPF outlet temperature sensor
10 52 DPF inlet pressure sensor
54 DPF outlet pressure sensor
56 DPF differential-pressure sensor
Specification
- 28-
CLAIMS
1. A DPF regeneration control device, provided for an exhaust-gas processing device of a
diesel engine, the exhaust-gas processing device including a DOC disposed in an exhaust
5 channel and a DPF disposed on a downstream side of the DOC, for controlling execution of
forced regeneration of heating the DPF to remove PM which accumulates on the DPF, the
forced regeneration comprising automatic regeneration automatically executed if a
predetermined forced-regeneration execution condition is satisfied, and manual regeneration
executed by manual operation to heat the DPF to a higher temperature than in the automatic
10 regeneration, and the DPF regeneration device comprising:
a DPF temperature-increase unit including a first temperature-increase unit configured
to heat the DPF to a predetermined temperature, and a second temperature-increase unit
configured to heat the DPF to a temperature higher than the predetermined temperature in
cooperation with the first temperature-increase unit;
15 a DOC clogging detection unit configured to detect that the DOC is clogged if a
clogging parameter detected during execution of the automatic regeneration exceeds a
clogging threshold value determined in advance for a predetermined period, the clogging
parameter being related to clogging of the DOC; and
a DOC clogging countermeasure unit configured to stop the automatic regeneration and
20 issue an alert to prompt execution of the manual regeneration, if the clogging of the DOC is
detected.
2. The DPF regeneration control device according to claim 1, further comprising:
a DOC clogging initial stage detection unit configured to detect that the DOC is in an
25 initial stage of the clogging if the clogging parameter detected during execution of the
automatic regeneration is not greater than the clogging threshold value and greater than a
second clogging threshold value smaller than the clogging threshold value for a
predetermined period, or if the clogging parameter is not greater than the clogging threshold
Specification
- 29-
value and a change amount of the clogging parameter is greater than a change-amount
threshold value set in advance for a predetermined period; and
a DOC clogging initial stage countermeasure unit configured to operate the first
temperature-increase unit for a predetermined period after completion of the automatic
5 regeneration if the DOC is detected to be in the initial stage of the clogging.
3. The DPF regeneration control device according to claim 1, further comprising:
a DOC clogging dangerous state detection unit configured to detect that the DOC is in a
clogging dangerous state if the diesel engine is under an operation state in which clogging of
10 the DOC is likely to occur during normal operation in which none of the forced regenerations,
which are the automatic regeneration and the manual regeneration, is executed; and
a DOC clogging dangerous state countermeasure unit configured to operate the first
temperature-increase unit for only a predetermined period if the DOC is detected to be in the
clogging dangerous state.
15
4. The DPF regeneration control device according to claim 3,
wherein the DOC clogging dangerous state detection unit is configured to detect that the
DOC is in the clogging dangerous state, if one or more of following conditions are satisfied:
a temperature of exhaust gas is not greater than a predetermined temperature
20 continuously for a predetermined period or longer;
the number of times, per unit time, which a change rate of an engine rotation speed
of the diesel engine exceeds a predetermined rotation-speed threshold value exceeds a
threshold value continuously for a predetermined period or longer; and
a mean value of a PM discharge-amount estimate value is at least a predetermined
25 threshold value continuously for a predetermined period or longer.
5. The DPF regeneration control device according to claim 1,
wherein the first temperature-increase unit comprises at least one of
Specification
- 30-
a throttle valve control unit configured to control an opening degree of a throttle
valve disposed in an intake channel,
an early post injection control unit configured to control a fuel injection amount of
early post injection of injecting fuel after a time of main combustion injection, or
5 a rail-pressure control unit configured to control a rail pressure at which the fuel is
injected, and
wherein the second temperature-increase unit comprises
a late post injection control unit configured to control a fuel injection amount of
late post injection of injecting fuel at a timing which does not contribute to combustion in a
10 combustion chamber after the early post injection, or
an exhaust-duct injection control unit configured to control a fuel injection amount
of exhaust-duct injection of injecting fuel to an exhaust channel on an engine downstream
side.
15 6. The DPF regeneration control device according to claim 1,
wherein the clogging parameter is set on the basis of a temperature difference between
an inlet temperature of the DPF and an outlet temperature of the DPF.
7. The DPF regeneration control device according to claim 1,
20 wherein the clogging parameter is set as an outlet temperature of the DPF.
8. The DPF regeneration control device according to claim 5,
wherein the clogging parameter is set on the basis of a temperature difference between
an outlet temperature and an inlet temperature of the DOC, a flow rate of exhaust gas flowing
25 through the DOC, and a fuel-injection amount of the late post injection or the exhaust-duct
injection.
9. The DPF regeneration control device according to claim 1,
Specification
- 31-
wherein the clogging parameter is set on the basis of an increase speed of an inlet
temperature of the DPF, and an increase speed of the inlet temperature of the DPF in an initial
state in which the DOC is not clogged.
5 10. The DPF regeneration control device according to claim 5,
wherein the late post injection control unit or the exhaust-duct injection control unit is
configured to control a fuel injection amount so that an inlet temperature of the DPF reaches a
target temperature required to execute the forced regeneration, and
wherein the clogging parameter is set
10 on the basis of a cumulative fuel-injection amount of the late post injection or the
exhaust-duct injection of injecting while an inlet temperature of the DPF increases by a
predetermined temperature, and a cumulative fuel-injection amount of the late post injection
or the exhaust-duct injection of injecting while the inlet temperature of the DPF increases by
the predetermined temperature in an initial state in which the DOC is not clogged, or
15 on the basis of a mean injection amount of the late post injection or the exhaustduct
injection of injecting in a stable state in which the inlet temperature of the DPF has
reached a target control temperature, and a mean injection amount of the late post injection or
the exhaust-duct injection of injecting in a stable state in which the inlet temperature of the
DPF has reached a target control temperature in an initial state in which the DOC is not
20 clogged.
11. The DPF regeneration control device according to claim 5,
wherein the late post injection control unit or the exhaust-duct injection control unit is
configured to control a fuel injection amount so that an inlet temperature of the DPF reaches a
25 target temperature required to execute the forced regeneration, and
wherein the clogged parameter comprises at least two of:
a clogging parameter set on the basis of a temperature difference between an inlet
temperature of the DPF and an outlet temperature of the DPF;
Specification
- 32-
a clogging parameter set as an outlet temperature of the DPF;
a clogging parameter set on the basis of a temperature difference between an outlet
temperature and an inlet temperature of the DOC, a flow rate of exhaust gas flowing through
the DOC, and a fuel-injection amount of the late post injection or the exhaust-duct injection;
5 the clogging parameter set on the basis of an increase speed of the inlet temperature of
the DPF, and an increase speed of the inlet temperature of the DPF in an initial state in which
the DOC is not clogged; and
a clogging parameter set on the basis of a cumulative fuel-injection amount of the late
post injection or the exhaust-duct injection of injecting while an inlet temperature of the DPF
10 increases by a predetermined temperature, and a cumulative fuel-injection amount of the late
post injection or the exhaust-duct injection of injecting while the inlet temperature of the DPF
increases by the predetermined temperature in an initial state in which the DOC is not clogged,
or on the basis of a mean injection amount of the late post injection or the exhaust-duct
injection of injecting in a stable state in which the inlet temperature of the DPF has reached a
15 target control temperature, and a mean injection amount of the late post injection or the
exhaust-duct injection of injecting in a stable state in which the inlet temperature of the DPF
has reached a target control temperature in an initial state in which the DOC is not clogged.