U.S. patent application number 13/393871 was filed with the patent office on 2012-11-08 for exhaust gas purification system for hydraulic operating machine.
This patent application is currently assigned to HITACHI CONSTRUCTION MACHINERY CO., LTD.. Invention is credited to Yasushi Arai, Kouji Ishikawa, Shohei Kamiya, Tsuyoshi Nakamura, Hidenobu Tsukada.
Application Number | 20120279203 13/393871 |
Document ID | / |
Family ID | 44319383 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120279203 |
Kind Code |
A1 |
Arai; Yasushi ; et
al. |
November 8, 2012 |
EXHAUST GAS PURIFICATION SYSTEM FOR HYDRAULIC OPERATING MACHINE
Abstract
When an output value of an exhaust resistance sensor 34 has
reached or exceeded a set value .DELTA.Pa, a controller 20 executes
recovery control of a filter of an exhaust gas purification device
32 after conducting exhaust temperature increasing control by
operating a pump discharge pressure increasing device (solenoid
proportional valve) 38 so that exhaust gas temperature as an output
value of an exhaust temperature sensor 33 reaches a preset value
Ta. Thus, the recovery process of the exhaust gas purification
device can be executed with reliability by increasing the exhaust
gas temperature irrespective of the operating environment and the
fuel consumption can be kept at a minimum necessary level.
Inventors: |
Arai; Yasushi;
(Tsuchiura-shi, JP) ; Ishikawa; Kouji;
(Kasumigaura-shi, JP) ; Kamiya; Shohei;
(Kasumigaura-shi, JP) ; Tsukada; Hidenobu;
(Ushiku-shi, JP) ; Nakamura; Tsuyoshi;
(Tsuchiura-shi, JP) |
Assignee: |
HITACHI CONSTRUCTION MACHINERY CO.,
LTD.
Tokyo
JP
|
Family ID: |
44319383 |
Appl. No.: |
13/393871 |
Filed: |
January 27, 2011 |
PCT Filed: |
January 27, 2011 |
PCT NO: |
PCT/JP2011/051647 |
371 Date: |
March 2, 2012 |
Current U.S.
Class: |
60/276 |
Current CPC
Class: |
F01N 3/023 20130101;
F02D 41/1448 20130101; B01D 53/9495 20130101; E02F 9/2235 20130101;
Y02T 10/26 20130101; B01D 53/944 20130101; F01N 2560/08 20130101;
F02D 41/0245 20130101; E02F 9/0866 20130101; F01N 9/002 20130101;
E02F 9/2066 20130101; Y02T 10/12 20130101; B01D 2258/012 20130101;
F02D 29/04 20130101; F01N 2560/06 20130101; E02F 9/2296 20130101;
F01N 2590/08 20130101; F02D 41/029 20130101; F02D 2041/026
20130101 |
Class at
Publication: |
60/276 |
International
Class: |
F01N 11/00 20060101
F01N011/00; F01N 3/023 20060101 F01N003/023 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2010 |
JP |
2010-017447 |
Claims
1. An exhaust gas purification system for a hydraulic operating
machine equipped with a diesel engine (1), an exhaust gas
purification device (32) provided in an exhaust line (31) of the
engine, a variable displacement hydraulic pump (2) driven by the
engine, a pump displacement adjusting device (14, 14A) for
controlling the displacement of the hydraulic pump, and at least
one hydraulic actuator (25) driven by hydraulic fluid discharged
from the hydraulic pump, comprising: an exhaust resistance sensor
(34) for detecting exhaust resistance of the exhaust gas
purification device (32); an exhaust temperature sensor (33) for
detecting temperature of exhaust gas in the exhaust gas
purification device; a pump discharge pressure increasing device
(38) provided in a hydraulic line (2a), through which the hydraulic
fluid discharged from the hydraulic pump (2) flows, for increasing
discharge pressure of the hydraulic pump; and a recovery control
device (20, 20A) for executing recovery of the exhaust gas
purification device by combusting and removing particulate matter
accumulated in the exhaust gas purification device when the exhaust
resistance detected by the exhaust resistance sensor has reached or
exceeded a set value, wherein the recovery control device includes
an exhaust temperature increasing control device (20, 20A) which
increases the exhaust gas temperature so as to make the exhaust gas
temperature detected by the exhaust temperature sensor reach a
preset value by increasing absorption torque of the hydraulic pump
by operating at least the latter one of the pump displacement
adjusting device (14, 14A) and the pump discharge pressure
increasing device (38) when the exhaust resistance detected by the
exhaust resistance sensor has reached or exceeded the set
value.
2. The exhaust gas purification system for a hydraulic operating
machine according to claim 1, wherein the exhaust temperature
increasing control device (20, 20A) controls an operation amount of
at least the latter one of the pump displacement adjusting device
(14, 14A) and the pump discharge pressure increasing device (38) so
that an increment of the absorption torque of the hydraulic pump
(2) amounts to 20%-30% of maximum torque of the engine (1).
3. The exhaust gas purification system for a hydraulic operating
machine according to claim 1, wherein the exhaust temperature
increasing control device (20,20A) includes an exhaust temperature
adjusting device which adjusts at least one selected from an
operation amount of the pump displacement adjusting device (14,
14A), an operation amount of the pump discharge pressure increasing
device (38) and an increment of revolution speed of the engine so
that the exhaust gas temperature remains within a preset range
after the exhaust gas temperature detected by the exhaust
temperature sensor (33) has been increased to the preset value.
4. The exhaust gas purification system for a hydraulic operating
machine according to claim 1, wherein the recovery control device
is an automatic recovery control device (20, 20A) which
automatically starts operation when the exhaust resistance detected
by the exhaust resistance sensor has reached or exceeded the set
value.
5. The exhaust gas purification system for a hydraulic operating
machine according to claim 4, further comprising operation
detecting means for detecting whether the hydraulic actuator (25)
is being driven or not, wherein the exhaust temperature increasing
control device (20, 20A) increases the exhaust gas temperature by
increasing the absorption torque of the hydraulic pump by operating
at least the latter one of the pump displacement adjusting device
(14, 14A) and the pump discharge pressure increasing device (38)
when the hydraulic actuator (25) is being driven.
6. The exhaust gas purification system for a hydraulic operating
machine according to claim 5, wherein when the hydraulic actuator
(25) is not being driven, the exhaust temperature increasing
control device (20, 20A) increases the exhaust gas temperature by
increasing revolution speed of the engine to a preset revolution
speed and increasing the absorption torque of the hydraulic pump
(2) by operating the pump displacement adjusting device (14, 14A)
and the pump discharge pressure increasing device (38).
7. The exhaust gas purification system for a hydraulic operating
machine according to claim 1, further comprising: operation
permission state detecting means (13) for detecting whether the
hydraulic operating machine is in an operation permission state or
not; and manual recovery instruction means (36), wherein: the
recovery control device is a manual recovery control device (36,
20, 20A) which issues an alarm when the exhaust resistance detected
by the exhaust resistance sensor (34) has reached or exceeded the
set value and starts operation when the operation permission state
detecting means detects that the hydraulic operating machine is not
in the operation permission state and there is an instruction by
the manual recovery instruction means, and the exhaust temperature
increasing control device (20, 20A) increases the exhaust gas
temperature by increasing revolution speed of the engine to a
preset revolution speed and increasing the absorption torque of the
hydraulic pump (2) by operating the pump displacement adjusting
device (14, 14A) and the pump discharge pressure increasing device
(38).
8. The exhaust gas purification system for a hydraulic operating
machine according to claim 4, wherein the exhaust temperature
increasing control device (20, 20A) previously stores an exhaust
resistance threshold value, for judging whether the recovery of the
exhaust gas purification device by the automatic recovery control
device (20, 20A) is necessary or not, as a function of engine
revolution speed and an engine load, determines the exhaust
resistance threshold value by referring to current engine
revolution speed and engine load and inputting them to the
function, and sets the determined exhaust resistance threshold
value as the set value.
9. The exhaust gas purification system for a hydraulic operating
machine according to claim 4, wherein the automatic recovery
control device (20, 20A) sets the set value of the exhaust
resistance at a lower value when the hydraulic actuator is not
being driven compared to cases where the hydraulic actuator is
being driven.
10. The exhaust gas purification system for a hydraulic operating
machine according to claim 1, wherein: the recovery control device
includes an automatic recovery control device (20, 20A) which
automatically starts operation when the exhaust resistance detected
by the exhaust resistance sensor has reached or exceeded the set
value and a manual recovery control device (36, 20, 20A) which
issues an alarm when the exhaust resistance detected by the exhaust
resistance sensor (34) has reached or exceeded the set value and
starts operation when the operation permission state detecting
means detects that the hydraulic operating machine is not in the
operation permission state and there is an instruction by the
manual recovery instruction means, and the set value in the
automatic recovery control device (20, 20A) is set lower than the
set value in the manual recovery control device (36, 20, 20A).
Description
TECHNICAL FIELD
[0001] The present invention relates to an exhaust gas purification
system for a hydraulic operating machine. In particular, the
invention relates to an exhaust gas purification system for a
hydraulic operating machine (e.g., hydraulic shovel) for recovering
a filter of an exhaust gas purification device installed in the
hydraulic operating machine by combusting and removing deposits
accumulated on the filter.
BACKGROUND ART
[0002] Conventional exhaust gas purification systems for purifying
the exhaust gas of a diesel engine include those described in
Patent Literatures 1 and 2, for example. In the exhaust gas
purification system described in the Patent Literature 1, an
exhaust gas purification device including a filter called
"particulate filter" (DPF: Diesel Particulate Filter) is placed in
the exhaust system of the engine of a transporting vehicle (e.g.,
truck) and the amount of particulate matter (hereinafter referred
to as "PM") discharged to the outside is reduced by collecting the
PM contained in the exhaust gas with the filter. In order to
prevent the clogging of the PM filter, the exhaust gas purification
system executes automatic recovery control and manual recovery
control, for example. For the recovery control, an oxidation
catalyst is placed upstream of the filter and the amount of the PM
accumulated on the filter (PM accumulation amount) is estimated by
detecting the differential pressure across the filter. In the
automatic recovery control, the temperature of the exhaust gas is
increased automatically when the PM accumulation amount has
exceeded a prescribed value, by which the oxidation catalyst is
activated and the PM accumulated on the filter is combusted and
removed. In the manual recovery control, when the PM accumulation
amount has exceeded a prescribed value, a warning lamp is lit up so
as to urge the operator to start recovery control by manual
operation in a state in which the vehicle is stopped. When a manual
recovery switch is turned ON by the operator, the temperature of
the exhaust gas is increased, by which the oxidation catalyst is
activated and the PM accumulated on the filter is combusted and
removed.
[0003] In the exhaust gas purification system described in the
Patent Literature 2, an exhaust resistance sensor is installed in
an exhaust gas processing device of a hydraulic operating machine.
For the automatic recovery control, the degree of the filter
clogging is detected. Before the filter clogging proceeds to a
level at which burnout is caused, a hydraulic load is exerted on
the engine by simultaneously increasing the discharge rate and the
discharge pressure of a hydraulic pump. With the increase in the
engine load, the output power of the engine increases and the
exhaust gas temperature rises, by which the deposits accumulated on
the filter are combusted and the filter is recovered.
PRIOR ART LITERATURE
Patent Literature
[0004] Patent Literature 1: JP, A 2005-120895 [0005] Patent
Literature 2: Japanese Patent No. 3073380
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0006] For transporting vehicles like trucks, the purification of
the exhaust gas is commonly conducted today by installing an
exhaust gas purification device as described in the Patent
Literature 1. Also for hydraulic operating machines typified by
hydraulic shovels, etc., exhaust gas regulations (exhaust emission
control) are being tightened stepwise in recent years from the
viewpoint of environmental preservation and various control
technologies related to exhaust gas purification systems are being
discussed as described in the Patent Literature 2.
[0007] In the technique of the Patent Literature 2, the degree of
the clogging is detected by the exhaust resistance sensor installed
in the exhaust gas processing device. Before the filter clogging
proceeds to the level at which burnout is caused, the discharge
rate and the discharge pressure of the hydraulic pump are
simultaneously increased to increase the engine load and raise the
exhaust gas temperature, thereby carrying out the recovery of the
filter.
[0008] However, the atmospheric temperature changes in a wide range
(e.g., -30.degree. C.-40.degree. C.) in the actual operating
environment of a hydraulic operating machine and the exhaust gas
temperature rises accordingly when the atmospheric temperature
rises. Therefore, the technique of the Patent Literature 2 can
increase the exhaust gas temperature to an unnecessary high level
by the exhaust gas temperature increasing control and consume the
fuel wastefully.
[0009] Further, the technique of the Patent Literature 2 specifies
that the exhaust gas temperature increasing control is desired to
be executed in a non-operating state (in which the operator is not
operating the machine/vehicle). In this case, an operation
interruption time (during which the operation or work has to be
interrupted) becomes necessary.
[0010] A first object of the present invention is to provide an
exhaust gas purification system for a hydraulic operating machine
that is capable of executing the recovery process of the exhaust
gas purification device with reliability by increasing the exhaust
gas temperature irrespective of the operating environment and
capable of keeping the fuel consumption at a minimum necessary
level.
[0011] A second object of the present invention is to provide an
exhaust gas purification system for a hydraulic operating machine
that is capable of executing the recovery process of the exhaust
gas purification device with reliability by increasing the exhaust
gas temperature irrespective of the operating environment, capable
of keeping the fuel consumption at a minimum necessary level, and
capable of reducing the operation interruption frequency of the
machine.
Means for Solving the Problem
[0012] (1) In order to achieve the above first object, an invention
described in claim 1 provides an exhaust gas purification system
for a hydraulic operating machine equipped with a diesel engine, an
exhaust gas purification device provided in an exhaust line of the
engine, a variable displacement hydraulic pump driven by the
engine, a pump displacement adjusting device for controlling the
displacement of the hydraulic pump, and at least one hydraulic
actuator driven by hydraulic fluid discharged from the hydraulic
pump. The exhaust gas purification system comprises: an exhaust
resistance sensor for detecting exhaust resistance of the exhaust
gas purification device; an exhaust temperature sensor for
detecting temperature of exhaust gas in the exhaust gas
purification device; a pump discharge pressure increasing device
provided in a hydraulic line, through which the hydraulic fluid
discharged from the hydraulic pump flows, for increasing discharge
pressure of the hydraulic pump; and a recovery control device for
executing recovery of the exhaust gas purification device by
combusting and removing particulate matter accumulated in the
exhaust gas purification device when the exhaust resistance
detected by the exhaust resistance sensor has reached or exceeded a
set value. The recovery control device includes an exhaust
temperature increasing control device which increases the exhaust
gas temperature so as to make the exhaust gas temperature detected
by the exhaust temperature sensor reach a preset value by
increasing absorption torque of the hydraulic pump by operating at
least the latter one (i.e., the pump discharge pressure increasing
device) of the pump displacement adjusting device and the pump
discharge pressure increasing device when the exhaust resistance
detected by the exhaust resistance sensor has reached or exceeded
the set value.
[0013] In the present invention configured as above, when the
exhaust resistance detected by the exhaust resistance sensor has
reached or exceeded the set value, the exhaust gas temperature is
increased so as to make the exhaust gas temperature detected by the
exhaust temperature sensor reach the preset value by operating at
least the pump discharge pressure increasing device. Therefore, the
recovery process of the exhaust gas purification device can be
executed with reliability by increasing the exhaust gas temperature
irrespective of the operating environment and the economic
efficiency can be improved by keeping the fuel consumption at a
minimum necessary level.
[0014] (2) In order to achieve the above second object, in an
invention described in claim 2, the exhaust temperature increasing
control device in the exhaust gas purification system according to
claim 1 controls an operation amount of at least the latter one of
the pump displacement adjusting device and the pump discharge
pressure increasing device so that an increment of the absorption
torque of the hydraulic pump amounts to 20%-30% of maximum torque
of the engine.
[0015] The present inventors have confirmed that the exhaust gas
temperature can be increased to approximately 250.degree.
C.-350.degree. C. without causing any problem to the operation of
the hydraulic operating machine driving hydraulic actuators if the
hydraulic absorption torque generated by the pump displacement
adjusting device and the pump discharge pressure increasing device
is approximately 20%-30% of the maximum torque of the engine. The
present invention has been made based on these findings. By
controlling at least the operation amount of the pump discharge
pressure increasing device so that the increment of the absorption
torque of the hydraulic pump amounts to 20%-30% of the maximum
torque of the engine, unnecessary and excessive increase in the
exhaust gas temperature can be avoided, the fuel consumption can be
kept at a minimum necessary level, and the economic efficiency can
be improved. Further, even in an operating state (in which the
operator is operating the machine), the recovery process of the
exhaust gas purification device can be performed by increasing the
exhaust gas temperature by the exhaust temperature increasing
control without causing any problem to the operation of the
hydraulic operating machine. Consequently, working efficiency can
be increased through the improvement of workability during the
execution of the recovery control and the reduction of the
operation interruption frequency of the hydraulic operating
machine.
[0016] (3) In an invention described in claim 3, in the exhaust gas
purification system according to claim 1 or 2, the exhaust
temperature increasing control device includes an exhaust
temperature adjusting device which adjusts at least one selected
from an operation amount of the pump displacement adjusting device,
an operation amount of the pump discharge pressure increasing
device and an increment of revolution speed of the engine so that
the exhaust gas temperature remains within a preset range after the
exhaust gas temperature detected by the exhaust temperature sensor
has been increased to the preset value.
[0017] With this configuration, the exhaust gas temperature T can
be reliably controlled and kept within the preset temperature
range. Consequently, ill effect on the operation can be minimized
in the recovery control in the operating state. In the recovery
control in the non-operating state, unnecessary increase in the
engine load can be avoided, the fuel consumption can be kept at a
minimum necessary level, and the economic efficiency can be
improved.
[0018] (4) In an invention described in claim 4, in the exhaust gas
purification system according to any one of claims 1-3, the
recovery control device is an automatic recovery control device
which automatically starts operation when the exhaust resistance
detected by the exhaust resistance sensor has reached or exceeded
the set value.
[0019] With this configuration, the recovery process of the exhaust
gas purification device can be executed with reliability by
increasing the exhaust gas temperature even in low-load operation
in the operating state.
[0020] (5) In an invention described in claim 5, the exhaust gas
purification system according to claim 4 further comprises
operation detecting means for detecting whether the hydraulic
actuator is being driven or not. The exhaust temperature increasing
control device increases the exhaust gas temperature by increasing
the absorption torque of the hydraulic pump by operating at least
the latter one of the pump displacement adjusting device and the
pump discharge pressure increasing device when the hydraulic
actuator is being driven.
[0021] With this configuration, the recovery process of the exhaust
gas purification device can be executed with reliability by
increasing the exhaust gas temperature even in low-load operation
in the operating state.
[0022] (6) In an invention described in claim 6, in the exhaust gas
purification system according to claim 5, when the hydraulic
actuator is not being driven, the exhaust temperature increasing
control device increases the exhaust gas temperature by increasing
revolution speed of the engine to a preset revolution speed and
increasing the absorption torque of the hydraulic pump by operating
the pump displacement adjusting device and the pump discharge
pressure increasing device.
[0023] With this configuration, the recovery process of the exhaust
gas purification device can be executed with reliability even in
the non-operating state by securely increasing the exhaust gas
temperature by the combination of the absorption torque increasing
control of the hydraulic pump and the engine revolution speed
increasing control.
[0024] (7) In an invention described in claim 7, the exhaust gas
purification system according to any one of claims 1-3 further
comprises: operation permission state detecting means for detecting
whether the hydraulic operating machine is in an operation
permission state or not; and manual recovery instruction means. The
recovery control device is a manual recovery control device which
issues an alarm when the exhaust resistance detected by the exhaust
resistance sensor has reached or exceeded a second set value and
starts operation when the operation permission state detecting
means detects that the hydraulic operating machine is not in the
operation permission state and there is an instruction by the
manual recovery instruction means. The exhaust temperature
increasing control device increases the exhaust gas temperature by
increasing revolution speed of the engine to a preset revolution
speed and increasing the absorption torque of the hydraulic pump by
operating the pump displacement adjusting device and the pump
discharge pressure increasing device.
[0025] With this configuration, also in the manual recovery
control, the recovery process of the exhaust gas purification
device can be executed with reliability by increasing the exhaust
gas temperature irrespective of the operating environment and the
economic efficiency can be improved by keeping the fuel consumption
at a minimum necessary level.
[0026] (8) In an invention described in claim 8, in the exhaust gas
purification system according to any one of claims 4-6, the exhaust
temperature increasing control device previously stores an exhaust
resistance threshold value, for judging whether the recovery of the
exhaust gas purification device by the automatic recovery control
device is necessary or not, as a function of engine revolution
speed and an engine load, determines the exhaust resistance
threshold value by referring to current engine revolution speed and
engine load and inputting them to the function, and sets the
determined exhaust resistance threshold value as the set value.
[0027] With this configuration, an appropriate value incorporating
the operating status of the engine can be set as the set value, by
which proper recovery control can be performed.
[0028] (9) In an invention described in claim 9, in the exhaust gas
purification system according to claim 4, the automatic recovery
control device sets the set value of the exhaust resistance at a
lower value when the hydraulic actuator is not being driven
compared to cases where the hydraulic actuator is being driven.
[0029] With this configuration, in the non-operating state (when
the hydraulic actuator is not being driven) in which the exhaust
gas temperature is relatively low and the particulate matter (PM)
tends to accumulate relatively more, the PM accumulated in the
exhaust gas purification device can be combusted more frequently
than in the operating state (when the hydraulic actuator is being
driven) and the exhaust gas purification device can be recovered
efficiently.
[0030] (10) In an invention described in claim 10, in the exhaust
gas purification system according to any one of claims 1-3, the
recovery control device includes an automatic recovery control
device which automatically starts operation when the exhaust
resistance detected by the exhaust resistance sensor has reached or
exceeded the set value and a manual recovery control device which
issues an alarm when the exhaust resistance detected by the exhaust
resistance sensor has reached or exceeded the set value and starts
operation when the operation permission state detecting means
detects that the hydraulic operating machine is not in the
operation permission state and there is an instruction by the
manual recovery instruction means. The set value in the automatic
recovery control device is set lower than the set value in the
manual recovery control device.
[0031] By setting the set value in the automatic recovery control
device lower than the set value in the manual recovery control
device as above, the frequency of the automatic recovery control
increases and the frequency of the manual recovery control
decreases due to the output value of the exhaust resistance sensor
increasing to the second set value less frequently. Consequently,
the operation interruption frequency of the hydraulic operating
machine can be reduced.
Effect of the Invention
[0032] According to the present invention, the recovery process of
the exhaust gas purification device can be executed with
reliability by increasing the exhaust gas temperature irrespective
of the operating environment and the economic efficiency can be
improved by keeping the fuel consumption at a minimum necessary
level.
[0033] According to the present invention, the recovery process of
the exhaust gas purification device can be executed with
reliability by increasing the exhaust gas temperature irrespective
of the operating environment, the economic efficiency can be
improved by keeping the fuel consumption at a minimum necessary
level, and the working efficiency can be increased through the
improvement of workability during the execution of the recovery
control and the reduction of the operation interruption frequency
of the hydraulic operating machine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a schematic diagram showing a hydraulic driving
system of a hydraulic operating machine equipped with an exhaust
gas purification system in accordance with a first embodiment of
the present invention.
[0035] FIG. 2 is a flow chart showing the contents of a calculation
process for positive control and pump torque limiting control
executed by a controller.
[0036] FIG. 3 is a graph showing an absorption torque property of a
hydraulic pump acquired as a result of pump torque limiting
control.
[0037] FIG. 4 is a schematic diagram showing the external
appearance of a hydraulic shovel as an example of the hydraulic
operating machine equipped with the hydraulic driving system and
the exhaust gas purification system shown in FIG. 1.
[0038] FIG. 5 is a flow chart showing the overall process flow of
automatic recovery control when the hydraulic operating machine is
in an operation permission state.
[0039] FIG. 6 is a flow chart showing the contents of the automatic
recovery control when the hydraulic operating machine is in the
operation permission state and in an operating state.
[0040] FIG. 7 is a flow chart showing the contents of the automatic
recovery control when the hydraulic operating machine is in the
operation permission state and in a non-operating state.
[0041] FIG. 8 is a flow chart showing the contents of manual
recovery control when the hydraulic operating machine is in an
operation prohibition state.
[0042] FIG. 9 is a graph showing the relationship between the
amount of PM accumulated on a filter in an exhaust gas purification
device and the exhaust resistance of the filter (differential
pressure across the filter) at the rated engine revolution speed
and the maximum engine load.
[0043] FIG. 10 is a graph showing changes in the relationship
between the PM accumulation amount and the exhaust resistance shown
in FIG. 9 depending on the engine revolution speed and the engine
load.
[0044] FIG. 11 is a flow chart showing the contents of exhaust gas
temperature increasing control (step S312 in FIG. 6).
[0045] FIG. 12 is a flow chart showing the contents of a process
including exhaust gas temperature increasing control (step S412 in
FIG. 7).
[0046] FIG. 13 is a schematic diagram showing a hydraulic driving
system of a hydraulic operating machine equipped with an exhaust
gas purification system in accordance with a second embodiment of
the present invention.
[0047] FIG. 14 is a flow chart showing the contents of a
calculation process for the positive control of the hydraulic pump
executed by a controller.
[0048] FIG. 15 is a graph like FIG. 3 showing the absorption torque
property of the hydraulic pump acquired as a result of the pump
torque limiting control.
[0049] FIG. 16 is a flow chart showing the details of the hydraulic
absorption torque increasing control in the step S312 in FIG. 6
regarding the automatic recovery control in the operating
state.
[0050] FIG. 17 is a flow chart (corresponding to FIG. 6 in the
first embodiment) showing the contents of the automatic recovery
control in the operating state executed by an exhaust gas
purification system in accordance with a third embodiment of the
present invention.
[0051] FIG. 18 is a flow chart (corresponding to FIG. 7 in the
first embodiment) showing the contents of the automatic recovery
control in the non-operating state executed by the exhaust gas
purification system of the third embodiment of the present
invention.
[0052] FIG. 19 is a flow chart (corresponding to FIG. 8 in the
first embodiment) showing the contents of the manual recovery
control executed by the exhaust gas purification system of the
third embodiment of the present invention when the hydraulic
operating machine is in the operation prohibition state.
MODE FOR CARRYING OUT THE INVENTION
[0053] Referring now to the drawings, a description will be given
in detail of preferred embodiments in accordance with the present
invention.
[0054] FIG. 1 is a schematic diagram showing a hydraulic driving
system of a hydraulic operating machine equipped with an exhaust
gas purification system in accordance with a first embodiment of
the present invention.
[0055] In FIG. 1, the hydraulic driving system comprises a diesel
engine (hereinafter properly abbreviated as an "engine") 1, a main
hydraulic pump 2 of the variable displacement type, a pilot pump 3,
a hydraulic actuator 25, flow/directional control valves 4 and 5, a
control lever device 8 and a main relief valve 9. The hydraulic
pump 2 and the pilot pump 3 are driven by the engine 1. The
hydraulic actuator 25 is driven by hydraulic fluid (oil) discharged
from the hydraulic pump 2. The flow/directional control valve 4
controls the flow rate and the direction of the hydraulic fluid
supplied from the hydraulic pump 2 to the hydraulic actuator 25.
The flow/directional control valve 5 controls the flow rate and the
direction of hydraulic fluid supplied from the hydraulic pump 2 to
other hydraulic actuators (not shown). The control lever device 8
is used for operating the hydraulic actuator 25. The main relief
valve 9 regulates the maximum pressure of a discharging hydraulic
line of the hydraulic pump 2.
[0056] The control lever device 8 includes pilot valves (pressure
reducing valves) 8a and 8b, to which hydraulic fluid is supplied
from the pilot pump 3. The discharge pressure of the pilot pump 3
is controlled by a pilot relief valve 10 at a constant level. When
a control lever 8c of the control lever device 8 is operated,
either the pilot valve 8a or the pilot valve 8b moves depending on
the direction and the amount of the operation, by which operating
pilot pressure is generated. By the operating pilot pressure, a
spool of the flow/directional control valve 4 is slid and the
hydraulic actuator 25 is operated.
[0057] The hydraulic driving system further comprises a pilot cut
valve 11, a safety lever 12, a switch 13, a regulator 14, pressure
sensors 16 and 17, a revolution sensor 18, an engine control dial
19 and a controller 20. The pilot cut valve 11 is attached to a
discharging hydraulic line of the pilot pump 3. The safety lever 12
(called "gate lock lever") is placed at the entrance to the
operator's seat. The switch 13 (operation permission state
detecting means) operates in conjunction with the safety lever 12.
The regulator 14 (pump displacement adjusting device) adjusts the
tilting angle (capacity or displacement volume) of the hydraulic
pump 2. The pressure sensor 16 (operation detecting means) detects
the operating pilot pressure generated by the pilot valves 8a and
8b as the operation amount of the control lever device 8. The
pressure sensor 17 detects the discharge pressure of the hydraulic
pump 2. The revolution sensor 18 detects the revolution speed of
the engine 1. The engine control dial 19 outputs an instruction
signal which specifies a target revolution speed of the engine
1.
[0058] A plurality of shuttle valves (including shuttle valves 21a
and 21b) are arranged along signal paths for the pressure sensor 16
for detecting the operating pilot pressure. When the operating
pilot pressure is generated by either the pilot valve 8a or 8b, the
operating pilot pressure is lead to the pressure sensor 16 via the
shuttle valves 21a and 21b and is detected by the pressure sensor
16. Also when a control lever device for another actuator (not
shown) is operated and operating pilot pressure is generated
accordingly, the operating pilot pressure is lead to the pressure
sensor 16 via a shuttle valve (not shown) and the shuttle valve 21b
and is detected by the pressure sensor 16.
[0059] When the hydraulic actuator 25 is operated, the controller
20 detects the operation amount of the control lever device 8 and
the engine revolution speed at that time with the pressure sensor
16 and the revolution sensor 18, respectively, calculates a target
tilting angle of the hydraulic pump 2 through a calculation process
for positive control and pump torque limiting control (also called
"pump horsepower control"), and changes the tilting angle of the
hydraulic pump 2 by controlling the regulator 14 to achieve the
target tilting angle.
[0060] The safety lever 12 can be operated to an operation
permission position and an operation prohibition position. The
switch 13 remains in an ON state when the safety lever 12 is at the
operation permission position, and in an OFF state when the safety
lever 12 is at the operation prohibition position. The controller
20 detects the ON/OFF state of the switch 13 operating in
conjunction with the safety lever 12 as above and opens the pilot
cut valve 11 to supply the hydraulic fluid to the pilot valves 8a
and 8b of the control lever device 8 only when the safety lever 12
is at the operation permission position (only when the switch 13 is
ON).
[0061] Further, the instruction signal from the engine control dial
19 is inputted to the controller 20. The controller 20 controls the
revolution speed and torque of the engine 1 by controlling an
electronic governor 1a (which controls the fuel injection quantity
of the engine 1) according to the instruction signal and the
measurement value of the revolution sensor 18 (current engine
revolution speed).
[0062] The contents of the calculation process for the positive
control and the pump torque limiting control of the hydraulic pump
2 executed by the controller 20 will be explained below referring
to FIG. 2. FIG. 2 is a flow chart showing the contents of the
calculation process for the positive control and the pump torque
limiting control executed by the controller 20.
[0063] First, the controller 20 calculates a demanded flow rate Qr
for the positive control by detecting the operation amount of the
control lever device 8 with the pressure sensor 16 (step S10). This
calculation is executed by multiplying the measurement value of the
pressure sensor 16 by a prescribed demanded flow rate conversion
factor, for example. Subsequently, the controller 20 calculates the
target tilting angle qr of the hydraulic pump 2 necessary for
making the hydraulic pump 2 discharge the demanded flow rate Qr
(step S15). This calculation is executed by dividing the demanded
flow rate Qr by the revolution speed of the hydraulic pump 2 and
multiplying the quotient by a prescribed conversion factor. The
revolution speed of the hydraulic pump 2 is determined from the
measurement value of the revolution sensor 18. Subsequently, the
controller 20 calculates a maximum tilting angle qmax of the
hydraulic pump 2 for the pump torque limiting control according to
the discharge pressure Pp of the hydraulic pump 2 inputted from the
pressure sensor 17 (step S20). This calculation is executed by
previously setting a constant maximum absorption torque property of
the hydraulic pump 2, checking the discharge pressure Pp of the
hydraulic pump 2 with the property, and thereby determining a
corresponding tilting angle (maximum tilting angle). Subsequently,
the controller 20 compares the target tilting angle qr with the
maximum tilting angle qmax (step S25). When the target tilting
angle qr is less than the maximum tilting angle qmax, the
controller 20 calculates a control signal for achieving the target
tilting angle qr and outputs the control signal to the regulator 14
(step S30). In contrast, when the target tilting angle qr is the
maximum tilting angle qmax or greater, the controller 20 calculates
a control signal for achieving the maximum tilting angle qmax and
outputs the control signal to the regulator 14 (step S35). With the
control signal, when the target tilting angle qr of the hydraulic
pump 2 is less than the maximum tilting angle qmax, the regulator
14 changes the tilting angle of the hydraulic pump 2 so as to
achieve the target tilting angle qr (positive control). When the
target tilting angle qr of the hydraulic pump 2 is the maximum
tilting angle qmax or greater, the regulator 14 changes the tilting
angle of the hydraulic pump 2 so as to limit the tilting angle to
the maximum tilting angle qmax (pump torque limiting control or
pump horsepower control).
[0064] FIG. 3 is a graph showing an absorption torque property of
the hydraulic pump 2 acquired as a result of the pump torque
limiting control, wherein the horizontal axis represents the
discharge pressure Pp of the hydraulic pump 2 and the vertical axis
represents the tilting angle (displacement) q of the hydraulic pump
2.
[0065] In FIG. 3, the absorption torque property of the hydraulic
pump 2 is made up of a constant maximum tilting angle property line
Tp0 and a constant maximum absorption torque property line Tp1.
[0066] When the discharge pressure Pp of the hydraulic pump 2 is
not higher than a first value P0 defined as the pressure at the
turning point (transition point) from the constant maximum tilting
angle property line Tp0 to the constant maximum absorption torque
property line Tp1, the maximum tilting angle (maximum displacement)
qmax of the hydraulic pump 2 remains at a constant value q0 (which
is determined by the mechanism of the hydraulic pump 2) even with
the increase in the discharge pressure Pp of the hydraulic pump 2.
In this case, the maximum absorption torque of the hydraulic pump 2
(product of the pump discharge pressure and the pump tilting angle)
increases with the increase in the discharge pressure Pp of the
hydraulic pump 2. As the discharge pressure Pp of the hydraulic
pump 2 increases over the first value P0, the maximum tilting angle
qmax of the hydraulic pump 2 decreases along the constant maximum
absorption torque property line Tp1 and the absorption torque of
the hydraulic pump 2 is kept at maximum torque Tmax which is
determined by the property line Tp1. This is a control part
corresponding to the aforementioned steps S25 and S35. Here, the
property line Tp1 is a part of a hyperbolic curve and the maximum
torque Tmax determined by the property line Tp1 has been set
slightly lower than limit torque TEL of the engine 1. With this
setting, when the discharge pressure Pp of the hydraulic pump 2
increases over the first value P0, the absorption torque (input
torque) of the hydraulic pump 2 is controlled so as not to exceed
the preset maximum torque Tmax (so as not to exceed the limit
torque TEL of the engine 1) by decreasing the maximum tilting angle
qmax of the hydraulic pump 2.
[0067] The exhaust gas purification system in accordance with this
embodiment is installed in such a hydraulic driving system. The
exhaust gas purification system comprises an exhaust gas
purification device 32 placed in an exhaust line 31 constituting
the exhaust system of the engine 1, an exhaust temperature sensor
33 placed at the inlet of the exhaust gas purification device 32
for detecting the temperature of the exhaust gas inside the exhaust
gas purification device, an exhaust resistance sensor 34 for
detecting exhaust resistance of a filter inside the exhaust gas
purification device 32, a manual recovery switch 36 used for
instructing the exhaust gas purification system (controller 20) to
start manual recovery control, and an alarm lamp 37 for informing
the operator that the a manual recovery process is necessary.
Output values of the sensors/switch are inputted to the controller
20. The exhaust gas purification system further comprises a
solenoid proportional valve 38 (pump discharge pressure increasing
device) provided in the discharging hydraulic line 2a of the
hydraulic pump 2. The solenoid proportional valve 38 is a variable
throttle valve which changes its opening area according to
instruction current supplied to its solenoid. The solenoid
proportional valve 38 stays at the full open position shown in the
figure when the instruction current is minimum (OFF), decreases the
opening area with the increase in the instruction current, and
minimizes the opening area (totally closed state) when the
instruction current is maximum.
[0068] The exhaust gas purification device 32 includes the filter,
with which particulate matter (PM) contained in the exhaust gas is
collected. The exhaust gas purification device 32 is also equipped
with an oxidation catalyst. When the exhaust gas temperature
exceeds a prescribed temperature, the oxidation catalyst is
activated and causes combustion of unburned fuel added to the
exhaust gas, an increase in the exhaust gas temperature, and
combustion of the collected PM accumulated on the filter.
[0069] Specifically, the exhaust gas purification device 32 is
equipped with a filter with an oxidation catalyst and another
oxidation catalyst placed upstream of the filter, for example. In
this case, the prescribed temperature (recovery start temperature)
for the activation of the oxidation catalyst is approximately
250.degree. C., for example. When the exhaust gas temperature
exceeds approximately 250.degree. C., the oxidation catalyst is
activated and the collected PM accumulated on the filter is
combusted. The exhaust gas purification device 32 may also be
implemented by the filter with the oxidation catalyst only. In this
case, the prescribed temperature (recovery start temperature) for
the activation of the oxidation catalyst is approximately
350.degree. C., for example.
[0070] The exhaust resistance sensor 34 is a differential pressure
detecting device for detecting the differential pressure between
the upstream side and the downstream side of the filter of the
exhaust gas purification device 32 (pressure loss of the filter),
for example.
[0071] FIG. 4 is a schematic diagram showing the external
appearance of a hydraulic shovel as an example of the hydraulic
operating machine equipped with the hydraulic driving system and
the exhaust gas purification system shown in FIG. 1.
[0072] The hydraulic shovel comprises a lower travel structure 100,
an upper swing structure 101 and a front work implement 102. The
lower travel structure 100 is equipped with right and left crawler
travel devices 103a and 103b, which are driven by right and left
travel motors 104a and 104b, respectively. The upper swing
structure 101 is mounted on the lower travel structure 100 so that
it can be swiveled by a swing motor 105. The front work implement
102 is attached to the front part of the upper swing structure 101
so that it can be elevated and lowered. The upper swing structure
101 includes an engine room 106 and a cab 107. The engine 1 is
installed in the engine room 106. The safety lever (gate lock
lever) 12 is placed in the cab 107 at a position close to the
entrance to the operator's seat. The control lever devices are
arranged to the right and left of the operator's seat.
[0073] The front work implement 102 is an articulated structure
including a boom 111, an arm 112 and a bucket 113. The boom 111 is
rotated and moved in the vertical direction by the expansion and
contraction of a boom cylinder 114. The arm 112 is rotated and
moved in the vertical direction and the front-to-back direction by
the expansion and contraction of an arm cylinder 115. The bucket
113 is rotated and moved in the vertical direction and the
front-to-back direction by the expansion and contraction of a
bucket cylinder 116.
[0074] In FIG. 1, the hydraulic actuator 25 corresponds to the
swing motor 105, for example, and the control lever device 8
corresponds to one of the control lever devices arranged to the
right and left of the operator's seat. Other hydraulic actuators
and control valves (the travel motors 104a and 104b, the boom
cylinder 114, the arm cylinder 115, the bucket cylinder 116, etc.)
are not shown in FIG. 1.
[0075] Next, the operation of the exhaust gas purification system
of this embodiment will be described below while explaining a
process executed by the controller 20 with reference to FIGS.
5-8.
[0076] FIGS. 5-8 are flow charts showing the contents of a filter
recovery calculation process executed by the controller 20. FIG. 5
shows the overall process flow of automatic recovery control when
the hydraulic operating machine (hereinafter referred to simply as
a "machine") is in an operation permission state. FIG. 6 shows the
contents of the automatic recovery control when the machine is in
the operation permission state and in an operating state (i.e.,
when the operator is operating the machine). FIG. 7 shows the
contents of the automatic recovery control when the machine is in
the operation permission state and in a non-operating state (i.e.,
when the operator is not operating the machine). FIG. 8 shows the
contents of the manual recovery control when the machine is in an
operation prohibition state. Each of the processes of FIGS. 5-8 is
executed repeatedly at preset periods (control cycles).
[0077] First, the overall process flow of the automatic recovery
control when the machine is in the operation permission state will
be explained referring to FIG. 5.
[0078] The controller 20 first judges whether the safety lever 12
is at the operation permission position or not by detecting whether
the switch 13 operating in conjunction with the safety lever 12 is
in the ON state or not (step S100). When the switch 13 is in the
OFF state, that is, when the safety lever 12 is not at the
operation permission position (i.e., at the operation prohibition
position), the machine is in the operation prohibition state. In
this case, the process in the current control cycle is ended
without any further processing. When the switch 13 is in the ON
state, that is, when the safety lever 12 is at the operation
permission position, the machine is in the operation permission
state. In this case, the process advances to the next step.
[0079] In the next step, the controller 20 judges whether any one
of the control lever devices is being operated by the operator or
not by detecting the output pressures of all the control lever
devices (including the control lever device 8) based on the output
values of the pressure sensor 16 and checking whether each of the
output pressures is at a level indicating the operator's operation
to a corresponding control lever device or not (step S200). When
any one of the control lever devices is being operated by the
operator, the machine is being operated (operating state). In this
case, the controller 20 executes automatic recovery control in the
operating state (step S300). When none of the control lever devices
is being operated by the operator, the machine is not being
operated (non-operating state). In this case, the controller 20
executes automatic recovery control in the non-operating state
(step S400).
[0080] The details of the automatic recovery control in the
operating state will be explained referring to FIG. 6.
[0081] First, the controller 20 calculates an exhaust resistance
threshold value .DELTA.Pa for judging whether the automatic
recovery control is necessary or not and sets the calculated
exhaust resistance threshold value .DELTA.Pa as a first set value
(step S305).
[0082] Here, the exhaust resistance threshold value .DELTA.Pa for
judging whether the automatic recovery control is necessary or not
will be explained referring to FIGS. 9 and 10.
[0083] FIG. 9 is a graph showing the relationship between the
amount of PM accumulated on the filter in the exhaust gas
purification device 32 and the exhaust resistance of the filter
(differential pressure across the filter) at the rated engine
revolution speed and the maximum engine load. FIG. 10 is a graph
showing changes in the relationship between the PM accumulation
amount and the exhaust resistance depending on the engine
revolution speed and the engine load.
[0084] Referring to FIG. 9, the differential pressure across the
filter increases with the increase in the PM accumulation amount of
the filter. In FIG. 9, ".DELTA.PLIMIT" represents the exhaust
resistance at a limit accumulation amount WLIMIT of the PM (limit
exhaust resistance). The limit accumulation amount WLIMIT means an
accumulation amount at which further PM accumulation on the filter
can cause abnormal combustion. ".DELTA.Pb" represents an exhaust
resistance threshold value (second set value) at a PM accumulation
amount Wb for judging whether the manual recovery control is
necessary or not. This threshold value is set as close to the PM
exhaust resistance .DELTA.PLIMIT as possible. ".DELTA.Pc"
represents an exhaust resistance threshold value at a PM
accumulation amount We for judging whether the recovery control
should be ended or not. An exhaust resistance threshold value
.DELTA.Pa at a PM accumulation amount Wa, for judging whether the
automatic recovery control is necessary or not, has been set at a
value lower than the threshold value (second set value) .DELTA.Pb
for the manual recovery control. For example, the threshold value
.DELTA.Pa has been set at approximately 40%-60% of the threshold
value .DELTA.Pb (.DELTA.Pa<.DELTA.Pb).
[0085] The relationship between the PM accumulation amount and the
exhaust resistance shown in FIG. 9 is that at the rated engine
revolution speed and the maximum engine load. The relationship
changes depending on the engine revolution speed and the engine
load as shown in FIG. 10. Specifically, even if the PM accumulation
amount of the filter remains constant, an increase in the engine
revolution speed or the engine load causes an increase in the
exhaust resistance of the filter since the fuel injection quantity
of the electronic governor 1a increases correspondingly and the
flow rate of the exhaust gas increases. Inversely, a decrease in
the engine revolution speed or the engine load causes a decrease in
the exhaust resistance of the filter since the fuel injection
quantity of the electronic governor 1a decreases correspondingly
and the flow rate of the exhaust gas decreases. Consequently, the
relationship between the PM accumulation amount and the exhaust
resistance changes as shown in FIG. 10 in response to the
increase/decrease in the engine revolution speed or the engine
load.
[0086] The controller 20 previously stores the exhaust resistance
threshold value .DELTA.Pa (for judging whether the automatic
recovery control is necessary or not) as a function of the engine
revolution speed and the engine load based on the relationships
between the PM accumulation amount and the exhaust resistance like
those shown in FIG. 10. In the step S305, the controller 20
determines the exhaust resistance threshold value .DELTA.Pa by
referring to the current engine revolution speed and the current
engine load and inputting them to the function. The measurement
value of the revolution sensor can be used as the current engine
revolution speed, and a target fuel injection quantity (as an
internal value of the electronic governor 1a) can be used as the
current engine load. It is also possible to calculate the
absorption torque of the hydraulic pump 2 from the tilting angle
and the discharge pressure of the hydraulic pump 2 and use the
calculated absorption torque as the engine load.
[0087] By determining the exhaust resistance threshold value
.DELTA.Pa (for judging whether the automatic recovery control is
necessary or not) by calculation and setting the threshold value
.DELTA.Pa as the first set value as explained above, an appropriate
threshold value .DELTA.Pa incorporating the operating status of the
engine can be set and the recovery control can be started
properly.
[0088] In the next step, the controller 20 detects the exhaust
resistance .DELTA.P of the filter in the exhaust gas purification
device 32 based on the output value of the exhaust resistance
sensor 34 and then judges whether or not the exhaust resistance
.DELTA.P is the first set value .DELTA.Pa or higher (step S310).
When the exhaust resistance .DELTA.P is less than the first set
value .DELTA.Pa, the controller 20 ends the process in the current
control cycle without any further processing since the PM
accumulation has not proceeded to the point at which the filter of
the exhaust gas purification device 32 needs the recovery by the
automatic recovery control. When the exhaust resistance .DELTA.P is
the first set value .DELTA.Pa or higher, the process advances to
the next step.
[0089] In the next step, the controller 20 starts the automatic
recovery control.
[0090] At the start of the automatic recovery control, exhaust gas
temperature increasing control is executed (step S312). In the
exhaust gas temperature increasing control, hydraulic absorption
torque increasing control is carried out. Specifically, the
discharge pressure of the hydraulic pump 2 is increased by
operating the solenoid proportional valve 38 and reducing its
opening area. Further, the discharge flow rate of the hydraulic
pump 2 is raised by increasing the tilting angle (displacement) of
the hydraulic pump 2. By increasing the discharge pressure and the
tilting angle (displacement) of the hydraulic pump 2, the
absorption torque of the hydraulic pump 2 (hydraulic absorption
torque) is increased and the engine load is increased. The
increment of the absorption torque of the hydraulic pump 2 in this
case is 20%-30% (preferably, about 30%) of the maximum torque of
the engine 1. With this setting, the engine 1 injects a
correspondingly larger amount of fuel, by which the exhaust gas
temperature can be increased.
[0091] The details of the hydraulic absorption torque increasing
control (step S312) will be explained referring to FIG. 11. FIG. 11
is a flow chart showing the contents of the hydraulic absorption
torque increasing control.
[0092] First, the controller 20 acquires the target tilting angle
qr of the hydraulic pump 2 calculated in the step S15 in FIG. 2
(step S50). A target tilting angle qco and a target pressure Pco
for the hydraulic absorption torque increasing control have
previously been set to the controller 20. The controller 20
compares the target tilting angle qr for the positive control with
the target tilting angle qco for the hydraulic absorption torque
increasing control (step S55). When the target tilting angle qr for
the positive control is less than or equal to the target tilting
angle qco for the hydraulic absorption torque increasing control,
the controller 20 invalidates the calculation process for the
positive control and the pump torque limiting control in the flow
chart of FIG. 2 (step S60). Subsequently, the controller 20
calculates a control signal for achieving the target tilting angle
qco for the hydraulic absorption torque increasing control and a
control signal for achieving the target pressure Pco for the
hydraulic absorption torque increasing control, outputs the former
control signal to the regulator 14, and outputs the latter control
signal to the solenoid proportional valve 38 (step S65). In
contrast, when the target tilting angle qr for the positive control
is greater than the target tilting angle qco for the hydraulic
absorption torque increasing control, the controller 20 validates
the calculation process for the positive control and the pump
torque limiting control in the flow chart of FIG. 2 (step S70).
Subsequently, the controller 20 calculates a control signal for
achieving the target pressure Pco for the hydraulic absorption
torque increasing control and outputs the control signal to the
solenoid proportional valve 38 (step S75).
[0093] In FIG. 3, the point A is the operating point of the
hydraulic pump 2 when the hydraulic absorption torque increasing
control is not executed in the non-operating state. In the
non-operating state in which no control lever device is being
operated, the demanded flow rate for the positive control equals 0
and the hydraulic pump 2 is held at a minimum tilting angle qmin
(point A). Further, in the non-operating state in which no control
lever device is being operated, every flow/directional control
valve 4, 5 is at the center valve position shown in the figure and
the hydraulic pump 2 remains at a minimum discharge pressure Ppmin
(point A). In FIG. 3, the point B is the operating point of the
hydraulic pump 2 when the hydraulic absorption torque increasing
control is executed in the non-operating state (explained later).
Either in the non-operating state or in the operating state, the
target tilting angle for the hydraulic absorption torque increasing
control is set at qco and the target pressure is set at Pco. Thus,
in the steps S65 and S75 in FIG. 11, the hydraulic absorption
torque increasing control is carried out using the target tilting
angle qco and the target pressure Pco at the point B.
[0094] In this case, the controller 20 controls the operation
amounts of the regulator 14 and the solenoid proportional valve 38
by setting the target tilting angle qco and the target pressure Pco
so that the increment of the absorption torque of the hydraulic
pump 2 by the hydraulic absorption torque increasing control
amounts to 20%-30% (preferably, about 30%) of the maximum torque of
the engine 1. In an examination conducted by the present inventors,
it has been confirmed that even in low-load operation, the exhaust
gas temperature can be raised to approximately 250.degree. C. when
the hydraulic absorption torque is increased by approximately 20%
of the maximum engine torque, and to approximately 350.degree. C.
when the hydraulic absorption torque is increased by approximately
30% of the maximum engine torque. We have also confirmed that no
problem in terms of operation occurs even if the machine is
operated in the state in which the hydraulic absorption torque has
been created by the solenoid proportional valve 38 as long as the
increment is approximately 30% of the maximum engine torque.
[0095] Subsequently, the controller 20 judges whether or not the
temperature T of the exhaust gas inside the exhaust gas
purification device 32 is a preset threshold value Ta or higher
based on the output value of the exhaust temperature sensor 33
(step S315). The judgment is repeated unless the exhaust gas
temperature T is judged to be the threshold value Ta or higher.
When the exhaust gas temperature T is judged to be the threshold
value Ta or higher, the controller 20 starts the recovery control
(step S320). The threshold value Ta may be set at, for example,
approximately 250.degree. C. (activation temperature of the
oxidation catalyst) in the case where the oxidation catalyst is
placed upstream of the filter in the exhaust gas purification
device 32. In the case where only the filter with an oxidation
catalyst is arranged in the exhaust gas purification device 32, the
threshold value Ta may be set at approximately 350.degree. C.
(activation temperature of the oxidation catalyst), for
example.
[0096] In the recovery control in the step S320, post-injection
(additional injection) in the expansion stroke after the main
injection of the engine is carried out by controlling the
electronic governor 1a of the engine 1. By the post-injection,
unburned fuel is introduced into the exhaust gas. The unburned fuel
is combusted by the activated oxidation catalyst, by which the
exhaust gas temperature is raised and the PM accumulated on the
filter is combusted and removed by the high-temperature exhaust
gas.
[0097] Subsequently, the controller 20 calculates and sets the
exhaust resistance threshold value .DELTA.Pc for judging whether
the recovery control should be ended or not (step S340). The idea
for the calculation of the threshold value .DELTA.Pc is similar to
that for the calculation of the threshold value .DELTA.Pa.
Specifically, the controller 20 previously stores the exhaust
resistance threshold value .DELTA.Pc (for judging whether the
automatic recovery control should be ended or not) as a function of
the engine revolution speed and the engine load based on the
relationships between the PM accumulation amount and the exhaust
resistance like those shown in FIG. 10. In the step S340, the
controller 20 determines the exhaust resistance threshold value
.DELTA.Pc by referring to the current engine revolution speed and
the current engine load and inputting them to the function. By the
above calculation and setting, an appropriate threshold value
.DELTA.Pc incorporating the operating status of the engine can be
set and the recovery control can be ended properly.
[0098] The exhaust gas temperature increasing control (hydraulic
absorption torque increasing control) and the recovery control
(additional fuel injection) are executed until the exhaust
resistance .DELTA.P of the exhaust gas purification device 32 falls
below the threshold value .DELTA.Pc. When the exhaust resistance
.DELTA.P of the exhaust gas purification device 32 is judged to be
below the threshold value .DELTA.Pc, the controller 20 ends the
automatic recovery control, puts the solenoid proportional valve 38
in the full open state by stopping activating the valve, and
thereby ends the exhaust gas temperature increasing control
(hydraulic absorption torque increasing control) and the recovery
control (additional fuel injection) (steps S320, S340, S345 and
S350).
[0099] Next, the details of the automatic recovery control in the
non-operating state will be explained referring to FIG. 7.
[0100] A hydraulic operating machine (hydraulic shovel) is
generally equipped with an automatic idling function. The automatic
idling function is a technique for reducing the engine revolution
speed to an idling revolution speed a prescribed time period (e.g.,
5 seconds) after the control lever 8c of the control lever device 8
is returned from its operating position to its neutral position.
Thus, in the non-operating state, the engine 1 is mostly in the
idling revolution state. Therefore, in the automatic recovery
control in the non-operating state, the hydraulic absorption torque
increasing control and an engine revolution speed increasing
control are executed in the exhaust gas temperature increasing
control (step S412). The increment of the absorption torque of the
hydraulic pump 2 in the hydraulic absorption torque increasing
control is 20%-30% (preferably, about 30%) of the maximum torque of
the engine 1 similarly to the case in the operating state. In the
engine revolution speed increasing control, the engine revolution
speed is increased to approximately 1700 rpm, for example.
[0101] FIG. 12 is a flow chart showing the contents of a process
including the hydraulic absorption torque increasing control and
the engine revolution speed increasing control executed in the step
S412 in FIG. 7.
[0102] The controller 20 calculates the aforementioned control
signal for achieving the target tilting angle qco for the hydraulic
absorption torque increasing control and the aforementioned control
signal for achieving the target pressure Pco for the hydraulic
absorption torque increasing control, outputs the former control
signal to the regulator 14, and outputs the latter control signal
to the solenoid proportional valve 38 (step S80). According to the
control signals, the hydraulic pump 2 operates at the operating
point B shown in FIG. 3. The controller 20 also executes the engine
revolution speed increasing control so as to increase the engine
revolution speed to approximately 1700 rpm (step S85).
[0103] Returning to FIG. 7, steps S405, S410, S415, S420, S440,
S445 and S450 are executed in the same way as the steps S305, S310,
S315, S320, S340, S345 and S350 in FIG. 6.
[0104] Incidentally, the exhaust resistance threshold value (first
set value) used for starting the automatic recovery control in the
non-operating state may be set lower than the threshold value
.DELTA.Pa which is used for starting the automatic recovery control
in the operating state. In the steps S405 and S410 in FIG. 7, the
threshold value set lower than .DELTA.Pa is expressed as
".DELTA.Pd" in parentheses (.DELTA.Pd<.DELTA.Pa). The threshold
value .DELTA.Pd is indicated in FIG. 9 as the exhaust resistance at
a PM accumulation amount Wd. By use of the threshold value
.DELTA.Pd, in the non-operating state in which the exhaust gas
temperature is relatively low and the PM tends to accumulate
relatively more, the PM accumulated on the filter can be combusted
more frequently than in the operating state and the filter can be
recovered efficiently.
[0105] Further, the increment of the absorption torque of the
hydraulic pump 2 (hydraulic absorption torque) in the hydraulic
absorption torque increasing control in the step S412 may be set
greater than 30% of the maximum engine torque (the increment in the
operating state) since no problem occurs even if the absorption
torque of the hydraulic pump 2 is increased greatly in the
non-operating state. With such a setting, the speed of the exhaust
gas temperature increasing control in the non-operating state can
be increased and the filter recovery process can be performed
quickly.
[0106] Next, the manual recovery control which is executed when the
machine is in the operation prohibition state will be explained
referring to FIG. 8.
[0107] First, the controller 20 detects the exhaust resistance
.DELTA.P of the exhaust gas purification device 32 based on the
output value of the exhaust resistance sensor 34 and then judges
whether or not the exhaust resistance .DELTA.P is the second set
value .DELTA.Pb (previously set as the exhaust resistance threshold
value for judging whether the manual recovery control is necessary
or not) or higher (step S500). Since the engine revolution speed
and the engine load are controlled at substantially constant levels
in the manual recovery control (as will be explained later), the
exhaust resistance threshold value for judging whether the manual
recovery control is necessary or not may be previously determined
and set as a fixed value as an exhaust resistance value
corresponding to the constant engine revolution speed and the
constant engine load. The same goes for the exhaust resistance
threshold value .DELTA.Pc (for judging whether the recovery control
should be ended or not) which will be explained later.
[0108] As explained referring to FIG. 9, the second set value
.DELTA.Pb has been set to satisfy the relationship
.DELTA.Pa<.DELTA.Pb with the first set value .DELTA.Pa and to be
as close to the exhaust resistance .DELTA.PLIMIT at the limit PM
accumulation amount WLIMIT as possible.
[0109] When the exhaust resistance .DELTA.P is less than the second
set value .DELTA.Pb, the controller 20 ends the process in the
current control cycle without any further processing since the PM
accumulation has not proceeded to the point at which the filter of
the exhaust gas purification device 32 needs the recovery by the
manual recovery control. When the exhaust resistance .DELTA.P is
the second set value .DELTA.Pb or higher, the process advances to
the next step.
[0110] In the next step, the controller 20 lights up the alarm lamp
37 and thereby informs the operator that the manual recovery
process is necessary (step S510).
[0111] Subsequently, the controller 20 judges whether the safety
lever 12 is at the operation prohibition position or not by
detecting whether the switch 13 operating in conjunction with the
safety lever 12 is in the OFF state or not (step S520). When the
switch 13 is in the ON state, that is, when the safety lever 12 is
not at the operation prohibition position (i.e., at the operation
permission position), the machine is in the operation permission
state. In this case, the machine is in a state unsuitable for the
manual recovery control, and thus the controller 20 ends the
process in the current control cycle without any further
processing. When the switch 13 is in the OFF state, that is, when
the safety lever 12 is at the operation prohibition position, the
machine is in the operation prohibition state. In this case, the
process advances to the next step.
[0112] In the next step, the controller 20 judges whether the
manual recovery switch 36 has been turned ON or not (step S530).
When the manual recovery switch 36 has not been turned ON, the
controller 20 ends the process in the current control cycle without
any further processing. When the manual recovery switch 36 has been
turned ON, the process advances to the next step.
[0113] In the next step, the controller 20 extinguishes the alarm
lamp 37 (step S540) and executes the exhaust gas temperature
increasing control by performing the hydraulic absorption torque
increasing control and the engine revolution speed increasing
control (step S545) similarly to the automatic recovery control
shown in FIG. 7.
[0114] Specifically, in the case of the manual recovery control,
the engine 1 is necessarily in the idling revolution state since
the safety lever is at the operation prohibition position, the
pilot cut valve 11 has been closed and the machine is in an
inoperable state (in which operation to the machine is impossible).
Therefore, in the step S545, the increase in the exhaust gas
temperature is promoted by executing the hydraulic absorption
torque increasing control (20%-30% (preferably, about 30%) of the
maximum torque of the engine 1) and the engine revolution speed
increasing control (approximately 1700 rpm, for example) similarly
to the step S412 in the automatic recovery control in the
non-operating state shown in FIG. 7.
[0115] Also when the machine is in the inoperable state (in which
operation to the machine is impossible), no problem occurs even if
the absorption torque of the hydraulic pump 2 is increased greatly.
Therefore, similarly to the step S412 in the automatic recovery
control in the non-operating state shown in FIG. 7, the increment
of the absorption torque of the hydraulic pump 2 (hydraulic
absorption torque) in the hydraulic absorption torque increasing
control in the step S545 may be set greater than 30% of the maximum
engine torque (the increment in the operating state). With such a
setting, the speed of the exhaust gas temperature increasing
control in cases where the machine is in the inoperable state can
be increased and efficient recovery control of the filter becomes
possible.
[0116] In the above explanation, the solenoid proportional valve 38
forms a pump discharge pressure increasing device which is provided
in the hydraulic line 2a (through which the hydraulic fluid
discharged from the hydraulic pump 2 flows) and increases the
discharge pressure of the hydraulic pump 2. The processing function
of the controller 20 in the steps S305-S350 in FIG. 6, the steps
S405-S450 in FIG. 7 and the steps S500-S610 in FIG. 8 forms a
recovery control device which executes the recovery of the exhaust
gas purification device 32 by combusting and removing the
particulate matter accumulated in the exhaust gas purification
device 32 when the exhaust resistance detected by the exhaust
resistance sensor 34 has reached or exceeded the set value
.DELTA.Pa or .DELTA.Pb.
[0117] The processing function of the controller 20 in the steps
S312 and S315 in FIG. 6, the steps S412 and S415 in FIG. 7 and the
steps S545 and S550 in FIG. 8 forms an exhaust temperature
increasing control device which increases the exhaust gas
temperature so as to make the exhaust gas temperature detected by
the exhaust temperature sensor 33 reach a preset value by
increasing the absorption torque of the hydraulic pump 2 by
operating at least the latter one (solenoid proportional valve 38)
of the regulator 14 (pump displacement adjusting device) and the
solenoid proportional valve 38 (pump discharge pressure increasing
device) when the exhaust resistance detected by the exhaust
resistance sensor 34 has reached or exceeded the set value
.DELTA.Pa or .DELTA.Pb. The exhaust temperature increasing control
device controls at least the operation amount of the solenoid
proportional valve 38 so that the increment of the absorption
torque of the hydraulic pump 2 amounts to 20%-30% of the maximum
torque of the engine 1.
[0118] The processing function of the controller 20 in the steps
S305-S350 in FIG. 6 and the steps S405-S450 in FIG. 7 forms an
automatic recovery control device which automatically starts
operation when the exhaust resistance detected by the exhaust
resistance sensor 34 has reached or exceeded the set value
.DELTA.Pa.
[0119] The switch 13 forms operation permission state detecting
means which detects whether the hydraulic operating machine is in
the operation permission state or not. The manual recovery switch
36 forms manual recovery instruction means. The manual recovery
instruction means and the processing function of the controller 20
in the steps S500-S610 in FIG. 8 form a manual recovery control
device which issues an alarm when the exhaust resistance detected
by the exhaust resistance sensor 34 has reached or exceeded the set
value .DELTA.Pb and starts operation when the switch 13 (operation
permission state detecting means) detects that the hydraulic
operating machine is not in the operation permission state and
there is an instruction by (received through) the manual recovery
switch 36 (manual recovery instruction means).
[0120] In this embodiment configured as above, even when the
atmospheric temperature as operating environment of the hydraulic
operating machine changes in a wide range (e.g., -30.degree.
C.-40.degree. C.) and the exhaust gas temperature changes
correspondingly, the exhaust gas temperature is increased by
operating the solenoid proportional valve 38 so that the exhaust
gas temperature as the output value of the exhaust temperature
sensor 33 reaches the preset value Ta. Therefore, the recovery
process of the exhaust gas purification device can be executed with
reliability by increasing the exhaust gas temperature irrespective
of the operating environment and economic efficiency can be
improved by keeping the fuel consumption at a minimum necessary
level.
[0121] Further, the present inventors have confirmed that the
exhaust gas temperature can be increased to approximately
250.degree. C.-350.degree. C. without causing any problem to the
operation of the hydraulic operating machine driving hydraulic
actuators if the hydraulic absorption torque generated by a
hydraulic absorption torque increasing device is approximately
20%-30% of the aforementioned maximum engine torque. By controlling
the operation amount of the solenoid proportional valve 38 so that
the increment of the absorption torque of the hydraulic pump 2
amounts to 20%-30% of the maximum torque of the engine 1,
unnecessary and excessive increase in the exhaust gas temperature
can be avoided, the fuel consumption can be kept at a minimum
necessary level, and the economic efficiency can be improved.
Furthermore, even in the operating state, the filter recovery
process can be performed by increasing the exhaust gas temperature
without causing any problem to the operation of the machine.
Consequently, working efficiency can be increased through the
improvement of workability during the execution of the recovery
control and the reduction of the operation interruption frequency
of the machine.
[0122] In any type of recovery control (the automatic recovery
control in the operating state, the automatic recovery control in
the non-operating state, the manual recovery control), the filter
recovery process can be performed reliably by increasing the
exhaust gas temperature and the fuel consumption can be kept at a
minimum necessary level irrespective of the operating
environment.
[0123] In the case where the exhaust resistance set value in the
automatic recovery control for cases where the hydraulic actuator
25 is not being driven is set at the value .DELTA.Pd lower than the
exhaust resistance set value .DELTA.Pa for cases where the
hydraulic actuator 25 is being driven, the following effect is
achieved: In the non-operating state (i.e., when no hydraulic
actuator is being driven) in which the exhaust gas temperature is
relatively low and the particulate matter (PM) tends to accumulate
relatively more, the PM accumulated on the filter of the exhaust
gas purification device 32 can be combusted more frequently than in
the operating state (i.e., when a hydraulic actuator is being
driven) and the filter of the exhaust gas purification device 32
can be recovered efficiently.
[0124] Moreover, since the set value .DELTA.Pa for the automatic
recovery control is set lower than the set value .DELTA.Pb for the
manual recovery control, the frequency of the automatic recovery
control increases and the frequency of the manual recovery control
decreases due to the output value of the exhaust resistance sensor
34 increasing to the set value .DELTA.Pb less frequently. This also
contributes to the reduction of the operation interruption
frequency of the hydraulic operating machine.
[0125] In addition, in the automatic recovery control in the
operating state, the exhaust resistance threshold value .DELTA.Pa
for judging whether the automatic recovery control is necessary or
not and the exhaust resistance threshold value .DELTA.Pc for
judging whether the recovery control should be ended or not are
determined and set through the aforementioned calculation.
Therefore, appropriate threshold values .DELTA.Pa and .DELTA.Pc
incorporating the operating status of the engine can be set and the
recovery control can be executed properly.
[0126] A second embodiment in accordance with the present invention
will be described below with reference to FIGS. 13-16. In this
embodiment, the pump torque control is executed directly by the
regulator without using the controller.
[0127] FIG. 13 is a schematic diagram showing a hydraulic driving
system of a hydraulic operating machine equipped with an exhaust
gas purification system in accordance with the second embodiment,
wherein elements equivalent to those shown in FIG. 1 are assigned
the same reference characters. In FIG. 13, the hydraulic driving
system of this embodiment is equipped with a controller 20A, a
regulator 14A to which the discharge pressure of the hydraulic pump
2 is lead via a hydraulic line 41, and a solenoid proportional
valve 42 which operates according to a control signal from the
controller 20A and outputs control pressure specifying the target
tilting angle qr of the hydraulic pump 2 to the regulator 14A.
[0128] When the hydraulic actuator 25 is operated, the controller
20A detects the operation amount of the control lever device 8 and
the engine revolution speed at that time with the pressure sensor
16 and the revolution sensor 18, respectively, calculates the
target tilting angle of the hydraulic pump 2 through a calculation
process for the positive control, and outputs a control signal to
the solenoid proportional valve 42 so that the target tilting angle
is achieved. The solenoid proportional valve 42 outputs control
pressure corresponding to the control signal. The regulator 14A
changes the tilting angle of the hydraulic pump 2 according to the
control pressure.
[0129] FIG. 14 is a flow chart showing the contents of a
calculation process for the positive control of the hydraulic pump
2 executed by the controller 20A, wherein steps identical with
those in FIG. 2 are assigned the same reference characters. As is
clear from the comparison between FIGS. 2 and 14, the controller
20A in this embodiment is configured to execute only the steps S10,
S15 and S30 related to the positive control. In the step S30, the
controller 20A outputs the control signal for achieving the target
tilting angle qr to the solenoid proportional valve 42.
[0130] The regulator 14A is configured to execute the positive
control based on the output pressure (control pressure) of the
solenoid proportional valve 42 while also executing the pump torque
control by itself based on the discharge pressure of the hydraulic
pump 2 supplied via the hydraulic line 41. Specifically, when the
control pressure outputted by the solenoid proportional valve 42
changes, the regulator 14A controls the tilting angle of the
hydraulic pump 2 so that the target tilting angle qr specified by
the control pressure is achieved (positive control). Further, when
the discharge pressure of the hydraulic pump 2 increases and the
target tilting angle qr specified by the control pressure reaches
or exceeds the maximum tilting angle qmax for the pump torque
limiting control, the regulator 14A controls the tilting angle of
the hydraulic pump 2 so as to limit the tilting angle to the
maximum tilting angle qmax (pump torque limiting control or pump
horsepower control). Such a regulator 14A is publicly known.
[0131] FIG. 15 is a graph like FIG. 3 showing the absorption torque
property of the hydraulic pump 2 acquired as a result of the pump
torque limiting control, wherein the horizontal axis represents the
discharge pressure Pp of the hydraulic pump 2 and the vertical axis
represents the tilting angle (displacement) q of the hydraulic pump
2.
[0132] In FIG. 15, the absorption torque property of the hydraulic
pump 2 is made up of a constant maximum tilting angle property line
Tp0 and constant maximum absorption torque property lines Tp2 and
Tp3. The control of the tilting angle of the hydraulic pump 2 when
the discharge pressure P of the hydraulic pump 2 is under the first
value P0 (on the constant maximum tilting angle property line Tp0)
is identical with that in FIG. 3. As the discharge pressure P of
the hydraulic pump 2 increases over the first value P0, the maximum
tilting angle qmax of the hydraulic pump 2 decreases along the
constant maximum absorption torque property lines Tp2 and Tp3 and
the absorption torque of the hydraulic pump 2 is kept at maximum
torque Tmax which is determined by the property lines Tp2 and Tp3.
The constant maximum absorption torque property lines Tp2 and Tp3
have been set based on two springs installed in the regulator 14A.
Each property line Tp2, Tp3 is in a shape imitating a hyperbolic
curve. The maximum torque Tmax determined by the property lines Tp2
and Tp3 has been set slightly lower than limit torque TEL of the
engine 1. With this setting, when the discharge pressure P of the
hydraulic pump 2 increases over the first value P0, the absorption
torque (input torque) of the hydraulic pump 2 is controlled so as
not to exceed the preset maximum torque Tmax (so as not to exceed
the limit torque TEL of the engine 1) by decreasing the maximum
tilting angle qmax of the hydraulic pump 2.
[0133] FIG. 16 is a flow chart showing the details of the hydraulic
absorption torque increasing control in the step S312 in FIG. 6
regarding the automatic recovery control in the operating state,
wherein steps identical with those in FIG. 11 are assigned the same
reference characters. As is clear from the comparison between FIGS.
11 and 16, the calculation process for the positive control
executed by the controller 20A is invalidated in step S60A and
validated in step S70A since the controller 20A in this embodiment
executes the calculation process for the positive control only. The
details of the hydraulic absorption torque increasing control in
the step S412 in FIG. 7 regarding the automatic recovery control in
the non-operating state and the details of the hydraulic absorption
torque increasing control in the step S545 in FIG. 8 regarding the
manual recovery control executed when the machine is in the
operation prohibition state are no different from those in FIG. 12
in the first embodiment.
[0134] According to this embodiment, effects similar to those of
the first embodiment can be achieved in hydraulic operating
machines in which the pump torque control is executed directly by a
regulator 14A.
[0135] A third embodiment in accordance with the present invention
will be described below with reference to FIGS. 17-19. This
embodiment illustrates another example of the exhaust gas
temperature increasing control. FIG. 17 is a flow chart showing the
contents of the automatic recovery control in the operating state.
FIG. 18 is a flow chart showing the contents of the automatic
recovery control in the non-operating state. FIG. 19 is a flow
chart showing the contents of the manual recovery control when the
hydraulic operating machine is in the operation prohibition state.
FIGS. 17-19 correspond to FIGS. 6-8 in the first embodiment,
respectively.
[0136] In the first and second embodiments, only the recovery
control (additional fuel injection) is executed and no fine
adjustment of the exhaust gas temperature T is made after the
exhaust gas temperature T has been raised to the threshold value Ta
by the exhaust gas temperature increasing control. In this
embodiment, the exhaust gas temperature T is adjusted to be within
a prescribed temperature range with respect to the threshold value
Ta even after the exhaust gas temperature T has reached/exceeded
the threshold value Ta due to the exhaust gas temperature
increasing control, by meticulously performing the hydraulic
absorption torque increasing control and/or the engine revolution
speed increasing control.
[0137] Specifically, after executing the exhaust gas temperature
increasing control (hydraulic absorption torque increasing control)
in the step S312 in FIG. 17, the controller 20A judges whether the
exhaust gas temperature T in the exhaust gas purification device 32
is within a preset temperature range between reference temperatures
Ta1 and Ta2 or not based on the output value of the exhaust
temperature sensor 33 (step S365). When the exhaust gas temperature
T is within the preset temperature range, the controller 20A starts
the recovery control (additional fuel injection) (step S320). When
the exhaust gas temperature T is not within the preset temperature
range, the controller 20A adjusts the torque increment of the
hydraulic absorption torque increasing control (step S370) and
repeats the torque increment adjustment until the exhaust gas
temperature T comes within the preset temperature range (step
S365.fwdarw.S370).
[0138] Here, the reference temperatures Ta1 and Ta2 specifying the
preset temperature range satisfy a relationship Ta1<Ta2. The
reference temperature Ta1 may be set equal to the threshold value
Ta in the first and second embodiments, for example. The reference
temperature Ta2 is set slightly (e.g., 5.degree. C.-50.degree. C.
(preferably, about 10.degree. C.-30.degree. C.)) higher than
Ta1.
[0139] The torque increment adjustment in the hydraulic absorption
torque increasing control is made by increasing/decreasing at least
one of the target tilting angle qco and the target pressure Pco for
the hydraulic absorption torque increasing control by a prescribed
amount when the target tilting angle qr for the positive control is
less than or equal to the target tilting angle qco for the
hydraulic absorption torque increasing control. When the target
tilting angle qr for the positive control is greater than the
target tilting angle qco for the hydraulic absorption torque
increasing control, the torque increment adjustment in the
hydraulic absorption torque increasing control is made by
increasing/decreasing the target pressure Pco for the hydraulic
absorption torque increasing control by a prescribed amount in
order to avoid ill effect on the positive control. By
increasing/decreasing the target tilting angle qco by a prescribed
amount, the operation amount of the regulator 14 is controlled and
the tilting angle (displacement) of the hydraulic pump 2 is
adjusted. By increasing/decreasing the target pressure Pco by a
prescribed amount, the operation amount (opening area) of the
solenoid proportional valve 38 is controlled and the discharge
pressure of the hydraulic pump 2 is adjusted. Therefore, by
increasing/decreasing at least one of the target tilting angle qco
and the target pressure Pco by a prescribed amount, the absorption
torque of the hydraulic pump 2 is controlled and the engine load is
increased/decreased, by which the exhaust gas temperature can be
adjusted.
[0140] Also in the steps S465 and S470 in FIG. 18 and the steps
S665 and S670 in FIG. 19, a process substantially identical with
that of the steps S365 and S370 in FIG. 17 is executed. However, it
is unnecessary to consider the ill effect on the positive control
in FIGS. 18 and 19 (control in the non-operating state). Thus, the
torque increment adjustment in the hydraulic absorption torque
increasing control in the steps S470 and S670 may be made
constantly by increasing/decreasing at least one of the target
tilting angle qco and the target pressure Pco for the hydraulic
absorption torque increasing control by a prescribed amount.
Incidentally, the adjustment of the exhaust gas temperature
described above may be made also by increasing/decreasing the
engine revolution speed in the engine revolution speed increasing
control in combination with or in place of the torque increment
adjustment in the hydraulic absorption torque increasing
control.
[0141] In the above explanation, the processing function of the
controller 20A in the steps S305-S350, S365 and S370 in FIG. 17,
the steps S405-S450, S465 and S470 in FIG. 18, and the steps
S500-S610, S665 and S670 in FIG. 19 forms a recovery control device
which executes the recovery of the exhaust gas purification device
32 by combusting and removing the particulate matter accumulated in
the exhaust gas purification device 32 when the exhaust resistance
detected by the exhaust resistance sensor 34 has reached or
exceeded the set value .DELTA.Pa or .DELTA.Pb.
[0142] The processing function of the controller 20A in the steps
S312, S365 and S370 in FIG. 17, the steps S412, S465 and S470 in
FIG. 18 and the steps S545, S665 and S670 in FIG. 19 forms an
exhaust temperature increasing control device which increases the
exhaust gas temperature so as to make the exhaust gas temperature
detected by the exhaust temperature sensor 33 reach a preset value
by increasing the absorption torque of the hydraulic pump 2 by
operating at least the latter one (solenoid proportional valve 38)
of the regulator 14 (pump displacement adjusting device) and the
solenoid proportional valve 38 (pump discharge pressure increasing
device) when the exhaust resistance detected by the exhaust
resistance sensor 34 has reached or exceeded the set value
.DELTA.Pa or .DELTA.Pb.
[0143] The steps S365 and S370 (FIG. 17), the steps S465 and S470
(FIG. 18) and the steps S665 and S670 (FIG. 19) form an exhaust
temperature adjusting device which adjusts at least one selected
from the operation amount of the regulator 14 or 14A (pump
displacement adjusting device), the operation amount of the
solenoid proportional valve 38 (pump discharge pressure increasing
device) and the increment of the engine revolution speed so that
the exhaust gas temperature remains within a preset range Ta1-Ta2
after the exhaust gas temperature detected by the exhaust
temperature sensor 33 has been increased to the preset value
Ta1.
[0144] In this embodiment configured as above, the torque increment
in the hydraulic absorption torque increasing control and/or the
increment of the engine revolution speed in the engine revolution
speed increasing control is finely adjusted so that the exhaust gas
temperature T remains within the preset temperature range.
Therefore, the exhaust gas temperature T can be reliably controlled
and kept within the preset temperature range. Consequently, ill
effect on the operation can be minimized in the recovery control in
the operating state. In the recovery control in the non-operating
state, unnecessary increase in the engine load can be avoided and
the fuel consumption can be kept at a minimum necessary level
irrespective of the operating environment, by which the economic
efficiency can be improved further.
[0145] Incidentally, while the fuel injection for the recovery
control in the above embodiments is executed by means of the
post-injection (additional injection) in the expansion stroke after
the main injection of the engine, the fuel injection for the
recovery control may also be carried out by providing the exhaust
line with an extra fuel injection device for the recovery control
and operating the fuel injection device.
[0146] While the hydraulic absorption torque increasing control in
the above embodiments is executed by providing the solenoid
proportional valve 38 (for exerting the load for increasing the
exhaust gas temperature on the engine in the recovery control) in
the discharging hydraulic line 2a of the hydraulic pump 2 and
controlling the operation amount (opening area) of the solenoid
proportional valve 38, the solenoid proportional valve 38 may also
be placed at the downstream end of a center bypass hydraulic line
penetrating the flow/directional control valve 4. Further, the
exertion of the load on the engine may also be implemented by use
of different means.
[0147] While the present invention has been applied to a hydraulic
shovel as an example of a hydraulic operating machine in the above
embodiments, the present invention may of course be applied to
hydraulic operating machines other than hydraulic shovels (wheel
shovels, crane trucks, etc.). Also in such cases, effects similar
to those of the above embodiments can be achieved.
DESCRIPTION OF REFERENCE NUMERALS
[0148] 1 engine [0149] 1a electronic governor [0150] 2 main
hydraulic pump [0151] 2a discharging hydraulic line [0152] 3 pilot
pump [0153] 4, 5 flow/directional control valve [0154] 8 control
lever device [0155] 8a, 8b pilot valve [0156] 9 main relief valve
[0157] 10 pilot relief valve [0158] 11 pilot cut valve [0159] 12
safety lever (gate lock lever) [0160] 13 switch [0161] 14, 14A
regulator [0162] 16 pressure sensor [0163] 17 pressure sensor
[0164] 18 revolution sensor [0165] 19 engine control dial [0166]
20, 20A controller [0167] 21a, 21b shuttle valve [0168] 25
hydraulic actuator [0169] 31 exhaust line [0170] 32 exhaust gas
purification device [0171] 33 exhaust temperature sensor [0172] 34
exhaust resistance sensor [0173] 36 manual recovery switch [0174]
37 alarm lamp [0175] 38 solenoid proportional valve (hydraulic
absorption torque increasing device) [0176] 41 hydraulic line
[0177] 42 solenoid proportional valve
* * * * *