U.S. patent application number 14/235182 was filed with the patent office on 2014-06-12 for hydraulic control system for construction machinery.
This patent application is currently assigned to VOLVO CONSTRUCTION EQUIPMENT AB. The applicant listed for this patent is Chun-Han Lee, Ok-Jin Suk. Invention is credited to Chun-Han Lee, Ok-Jin Suk.
Application Number | 20140158235 14/235182 |
Document ID | / |
Family ID | 47668625 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140158235 |
Kind Code |
A1 |
Suk; Ok-Jin ; et
al. |
June 12, 2014 |
HYDRAULIC CONTROL SYSTEM FOR CONSTRUCTION MACHINERY
Abstract
A hydraulic control system for a construction machine is
disclosed, which can operate an arm cylinder and a bucket cylinder
by supplying hydraulic fluid from respective hydraulic pumps to the
arm cylinder and the bucket cylinder during a combined operation,
such as an excavating work, in which an arm joystick and a bucket
joystick are simultaneously operated. The hydraulic control system
includes a first arm control valve installed in a flow path between
the first hydraulic pump and the arm cylinder and shifted to
control a start, stop, and direction change of the arm cylinder in
response to an operation of the arm joystick, a second arm control
valve installed in a flow path between the second hydraulic pump
and the arm cylinder and shifted to make discharged hydraulic fluid
of the second hydraulic pump join hydraulic fluid of the arm
cylinder to be supplied if a control signal according to the
operation of the arm joystick exceeds a set value, a bucket control
valve installed in a path between the second hydraulic pump and the
bucket cylinder and shifted to control a start, stop, and direction
change of the bucket cylinder in response to the operation of the
bucket joystick, and a confluence cutoff proportional valve
installed in a path between the second hydraulic pump and the
second arm control valve.
Inventors: |
Suk; Ok-Jin; (Changwon-si,
KR) ; Lee; Chun-Han; (Gimhae-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Suk; Ok-Jin
Lee; Chun-Han |
Changwon-si
Gimhae-si |
|
KR
KR |
|
|
Assignee: |
VOLVO CONSTRUCTION EQUIPMENT
AB
Eskilstuna
SE
|
Family ID: |
47668625 |
Appl. No.: |
14/235182 |
Filed: |
August 9, 2011 |
PCT Filed: |
August 9, 2011 |
PCT NO: |
PCT/KR2011/005790 |
371 Date: |
January 27, 2014 |
Current U.S.
Class: |
137/565.11 |
Current CPC
Class: |
E02F 9/2282 20130101;
E02F 9/2235 20130101; F15B 2211/20576 20130101; Y10T 137/85986
20150401; E02F 9/2004 20130101; F15B 2211/20546 20130101; E02F
9/2296 20130101; E02F 9/2242 20130101; E02F 9/2285 20130101; F15B
2211/7053 20130101; E02F 9/2267 20130101; E02F 9/2292 20130101;
F15B 11/17 20130101; F15B 2211/3116 20130101 |
Class at
Publication: |
137/565.11 |
International
Class: |
E02F 9/22 20060101
E02F009/22; E02F 9/20 20060101 E02F009/20 |
Claims
1. A hydraulic control system for a construction machine,
comprising: first and second variable displacement hydraulic pumps;
an arm cylinder connected to the first hydraulic pump; a bucket
cylinder connected to the second hydraulic pump; an arm joystick
and a bucket joystick configured to output control signals
according to operation amounts thereof; a first arm control valve
installed in a flow path between the first hydraulic pump and the
arm cylinder and shifted to control a start, stop, and direction
change of the arm cylinder in response to an operation of the arm
joystick; a second arm control valve installed in a flow path
between the second hydraulic pump and the arm cylinder and shifted
to make discharged hydraulic fluid of the second hydraulic pump
join hydraulic fluid of the arm cylinder to be supplied if the
control signal according to the operation of the arm joystick
exceeds a set value; a bucket control valve installed in a path
between the second hydraulic pump and the bucket cylinder and
shifted to control a start, stop, and direction change of the
bucket cylinder in response to the operation of the bucket
joystick; and a confluence cutoff proportional valve installed in a
path between the second hydraulic pump and the second arm control
valve and shifted to cut off confluence of the hydraulic fluid
discharged from the second hydraulic pump with the discharged
hydraulic fluid of the first hydraulic pump if discharge pressures
of the first and second hydraulic pumps exceed a set value.
2. A hydraulic control system including first and second variable
displacement hydraulic pumps, an arm cylinder connected to the
first hydraulic pump, a bucket cylinder connected to the second
hydraulic pump, an arm joystick and a bucket joystick outputting
control signals according to operation amounts thereof, a first arm
control valve controlling hydraulic fluid supplied to the arm
cylinder according to an operation of the arm joystick, a second
arm control valve controlling the hydraulic fluid that is supplied
from the second hydraulic pump to the arm cylinder if a control
signal according to the operation of the arm joystick exceeds a set
value, a bucket control valve controlling driving of the bucket
cylinder according to an operation of the bucket joystick, and a
confluence cutoff proportional valve making the hydraulic fluid of
the second hydraulic pump join the hydraulic fluid of the first
hydraulic pump if the arm cylinder is singly operated and cutting
off a confluence function if the arm cylinder and the bucket
cylinder are simultaneously operated, the hydraulic control system
comprising: a first step of reading an arm-in control signal
according to an operation amount of the arm joystick, a bucket-in
control signal according to an operation amount of the bucket
joystick, and discharge pressures of the first and second hydraulic
pumps; a second step of determining whether the arm-in control
signal exceeds one set value and whether the bucket-in control
signal exceeds the one set value; a third step of determining
whether the discharge pressure of the first hydraulic pump exceeds
another set value and whether the discharge pressure of the second
hydraulic pump exceeds the other set value; and a fourth step of
releasing the confluence function by applying control signals that
are in proportion to the arm-in control signal and the bucket-in
control signal to the confluence cutoff proportional valve if the
arm-in control signal and the bucket-in control signal exceed the
one set value and the discharge pressures of the first and second
hydraulic pumps exceed the other set value.
3. The hydraulic control system according to claim 1, wherein the
confluence cutoff proportional valve operates in a first state of
cutting off a flow path when the arm joystick and the bucket
joystick are simultaneously operated, and in a second state of
connecting the flow path when the arm joystick is singly
operated.
4. The hydraulic control system according to claim 2, wherein the
confluence cutoff proportional valve operates in a first section
where movement amounts are controlled to be gradually increased in
proportion to the operation amounts of the arm joystick and the
bucket joystick to release the confluence function, in a second
section where the confluence cutoff state is maintained according
to the increase of the operation amounts of the arm joystick and
the bucket joystick, and in a third section where movement amounts
are controlled to be gradually decreased in reverse proportion to
the operation amounts of the arm joystick and the bucket joystick
to be shifted to the confluence function.
5. The hydraulic control system according to claim 1, wherein the
confluence cutoff proportional valve comprises a solenoid valve
that is shifted to open/close the flow path in response to an input
of an electric signal.
6. The hydraulic control system according to claim 1, wherein the
confluence cutoff proportional valve comprises an electro
proportional control valve that is shifted to open/close the flow
path according to an input of an electric signal.
Description
TECHNICAL FIELD
[0001] The present invention relates to a hydraulic control system
for a construction machine. More particularly, the present
invention relates to a hydraulic control system for a construction
machine, which can operate an arm cylinder and a bucket cylinder by
supplying hydraulic fluid from respective hydraulic pumps to the
arm cylinder and the bucket cylinder during a combined operation
such as an excavating work in which an arm joystick and a bucket
joystick are simultaneously operated.
BACKGROUND ART
[0002] A hydraulic control system for a construction machine in the
related art, as illustrated in FIG. 1, includes a pair of first and
second variable displacement hydraulic pumps (hereinafter referred
to as "hydraulic pumps") 1 and 2; an arm cylinder 3 connected to
the first hydraulic pump 1; a bucket cylinder (not illustrated)
connected to the second hydraulic pump 2; an arm joystick 4 and a
bucket joystick (not illustrated) outputting control signals
according to operation amounts; a first arm control valve 5
installed in a flow path between the first hydraulic pump 1 and the
arm cylinder 3 and shifted to control a start, stop, and direction
change of the arm cylinder 3 in response to an operation of the arm
joystick 4; a second arm control valve 6 installed in a flow path
between the second hydraulic pump 2 and the arm cylinder 3 and
shifted to make discharged hydraulic fluid of the second hydraulic
pump 2 join the hydraulic fluid of the arm cylinder 3 to be
supplied if the control signal according to the operation of the
arm joystick 4 exceeds a set value; and a bucket control valve (not
illustrated) installed in a path between the second hydraulic pump
2 and the bucket cylinder (not illustrated) and shifted to control
a start, stop, and direction change of the bucket cylinder in
response to the operation of the bucket joystick.
[0003] Accordingly, in the case where an excavating work is
performed by simultaneously operating an arm and a bucket, the
first arm control valve 5 is shifted in the rightward direction in
the drawing in accordance with a control signal that is generated
through the operation of the arm joystick 4 to perform arm-in
driving, and thus hydraulic fluid that is discharged from the first
hydraulic pump 1 is supplied to a large chamber 3a of the arm
cylinder 3 via the shifted first arm control valve 5. At this time,
the hydraulic fluid that returns from a small chamber 3b of the arm
cylinder 3 is fed back to a hydraulic tank T via the first arm
control valve 5.
[0004] If an operation amount of the arm joystick 4 exceeds a
predetermined value, the second arm control valve 6 is shifted in
the leftward direction in the drawing, and thus the hydraulic fluid
from the second hydraulic pump 2 joins hydraulic fluid of a large
chamber 2a of the arm cylinder 2 via the shifted second arm control
valve 6 to be supplied.
[0005] On the other hand, although not illustrated in the drawing,
the bucket cylinder may be driven by the hydraulic fluid that is
supplied from the second hydraulic pump 2 due to the operation of
the bucket joystick.
[0006] Accordingly, during the combined operation in which the arm
and the bucket are simultaneously operated, the arm cylinder 3 may
be driven by the hydraulic fluids discharged from the first and
second hydraulic pumps 1 and 2 to join each other.
[0007] As described above, in the case where the excavating work is
performed by simultaneously operating the arm and the bucket (in
general, a load that is generated on the side of the arm cylinder 3
is relatively higher than a load that is generated on the side of
the bucket cylinder), the hydraulic fluids discharged from the
first and second hydraulic pumps 1 and 2 join each other and are
supplied to the arm cylinder 3 to drive the arm cylinder, and the
hydraulic fluid discharged from the second hydraulic pump 2 is
supplied only to the bucket cylinder to drive the bucket cylinder.
At this time, even in the case where the load is generated on
either side of the arm cylinder 3 and the bucket cylinder due to an
external load that acts on the arm cylinder 3 or the bucket
cylinder, the discharge pressures of the first and second hydraulic
pumps 1 and 2 are generally increased. Due to this, a pressure loss
occurs, and this exerts a bad influence on the fuel efficiency.
DISCLOSURE
Technical Problem
[0008] Therefore, the present invention has been made to solve the
above-mentioned problems occurring in the related art, and one
embodiment of the present invention is related to a hydraulic
control system for a construction machine, which can prevent a
pressure loss of hydraulic pumps by releasing a confluence function
and making hydraulic fluids from the respective hydraulic pumps be
supplied to an arm cylinder and a bucket cylinder, respectively,
during an excavating work in which an arm and a bucket are
simultaneously operated.
Technical Solution
[0009] In accordance with an aspect of the present invention, there
is provided a hydraulic control system for a construction machine,
which includes first and second variable displacement hydraulic
pumps; an arm cylinder connected to the first hydraulic pump; a
bucket cylinder connected to the second hydraulic pump; an arm
joystick and a bucket joystick configured to output control signals
according to operation amounts thereof; a first arm control valve
installed in a flow path between the first hydraulic pump and the
arm cylinder and shifted to control a start, stop, and direction
change of the arm cylinder in response to an operation of the arm
joystick; a second arm control valve installed in a flow path
between the second hydraulic pump and the arm cylinder and shifted
to make discharged hydraulic fluid of the second hydraulic pump
join hydraulic fluid of the arm cylinder to be supplied if the
control signal according to the operation of the arm joystick
exceeds a set value; a bucket control valve installed in a path
between the second hydraulic pump and the bucket cylinder and
shifted to control a start, stop, and direction change of the
bucket cylinder in response to the operation of the bucket
joystick; and a confluence cutoff proportional valve installed in a
path between the second hydraulic pump and the second arm control
valve and shifted to cut off confluence of the hydraulic fluid
discharged from the second hydraulic pump with the discharged
hydraulic fluid of the first hydraulic pump if discharge pressures
of the first and second hydraulic pumps exceed a set value.
[0010] In accordance with another aspect of the present invention,
there is provided a hydraulic control system including first and
second variable displacement hydraulic pumps, an arm cylinder
connected to the first hydraulic pump, a bucket cylinder connected
to the second hydraulic pump, an arm joystick and a bucket joystick
outputting control signals according to operation amounts thereof,
a first arm control valve controlling hydraulic fluid supplied to
the arm cylinder according to an operation of the arm joystick, a
second arm control valve controlling the hydraulic fluid that is
supplied from the second hydraulic pump to the arm cylinder if a
control signal according to the operation of the arm joystick
exceeds a set value, a bucket control valve controlling driving of
the bucket cylinder according to an operation of the bucket
joystick, and a confluence cutoff proportional valve making the
hydraulic fluid of the second hydraulic pump join the hydraulic
fluid of the first hydraulic pump if the arm cylinder is singly
operated and cutting off a confluence function if the arm cylinder
and the bucket cylinder are simultaneously operated, the hydraulic
control system includes a first step of reading an arm-in control
signal according to an operation amount of the arm joystick, a
bucket-in control signal according to an operation amount of the
bucket joystick, and discharge pressures of the first and second
hydraulic pumps; a second step of determining whether the arm-in
control signal exceeds one set value and whether the bucket-in
control signal exceeds the one set value; a third step of
determining whether the discharge pressure of the first hydraulic
pump exceeds another set value and whether the discharge pressure
of the second hydraulic pump exceeds the other set value; and a
fourth step of releasing the confluence function by applying
control signals that are in proportion to the arm-in control signal
and the bucket-in control signal to the confluence cutoff
proportional valve if the arm-in control signal and the bucket-in
control signal exceed the one set value and the discharge pressures
of the first and second hydraulic pumps exceed the other set
value.
[0011] The confluence cutoff proportional valve may operate in a
first state of cutting off a flow path when the arm joystick and
the bucket joystick are simultaneously operated, and in a second
state of connecting the flow path when the arm joystick is singly
operated.
[0012] The confluence cutoff proportional valve may operate in a
first section where movement amounts are controlled to be gradually
increased in proportion to the operation amounts of the arm
joystick and the bucket joystick to release the confluence
function, in a second section where the confluence cutoff state is
maintained according to the increase of the operation amounts of
the arm joystick and the bucket joystick, and in a third section
where movement amounts are controlled to be gradually decreased in
reverse proportion to the operation amounts of the arm joystick and
the bucket joystick to be shifted to the confluence function.
[0013] The confluence cutoff proportional valve may include a
solenoid valve that is shifted to open/close the flow path in
response to an input of an electric signal.
[0014] The confluence cutoff proportional valve may include an
electro proportional control valve that is shifted to open/close
the flow path according to an input of an electric signal.
Advantageous Effect
[0015] The hydraulic control system for a construction machine
according to the aspects of the present invention as configured
above has the following advantages.
[0016] When the excavating work is done by simultaneously operating
the arm and the bucket, the hydraulic fluids are made to be
supplied from the respective hydraulic pumps to the arm cylinder
and the bucket cylinder, and thus pressure loss of the hydraulic
pumps can be prevented to heighten the fuel efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above objects, other features and advantages of the
present invention will become more apparent by describing the
preferred embodiments thereof with reference to the accompanying
drawings, in which:
[0018] FIG. 1 is a hydraulic circuit diagram of a hydraulic control
system for a construction machine in the related art;
[0019] FIG. 2 is a hydraulic circuit diagram of a hydraulic control
system for a construction machine according to an embodiment of the
present invention;
[0020] FIG. 3 is a flowchart illustrating a method for controlling
a hydraulic control system for a construction machine according to
an embodiment of the present invention; and
[0021] FIG. 4 is a graph explaining the operation of a confluence
cutoff proportional valve in a hydraulic control system for a
construction machine according to an embodiment of the present
invention.
BEST MODE
[0022] Hereinafter, preferred embodiments of the present invention
will be described in detail with reference to the accompanying
drawings. The matters defined in the description, such as the
detailed construction and elements, are nothing but specific
details provided to assist those of ordinary skill in the art in a
comprehensive understanding of the invention, and the present
invention is not limited to the embodiments disclosed
hereinafter.
[0023] According to an embodiment of the present invention as
illustrated in FIG. 2, a hydraulic control system for a
construction machine includes first and second variable
displacement hydraulic pumps (hereinafter referred to as "hydraulic
pumps") 1 and 2; an arm cylinder 3 connected to the first hydraulic
pump 1; a bucket cylinder (not illustrated) connected to the second
hydraulic pump 2; an arm joystick 4 and a bucket joystick (not
illustrated) outputting control signals according to operation
amounts; a first arm control valve 5 installed in a flow path
between the first hydraulic pump 1 and the arm cylinder 3 and
shifted to control a start, stop, and direction change of the arm
cylinder 3 in response to an operation of the arm joystick 4; a
second arm control valve 6 installed in a flow path between the
second hydraulic pump 2 and the arm cylinder 3 and shifted to make
discharged hydraulic fluid of the second hydraulic pump 2 join the
hydraulic fluid of the arm cylinder 3 to be supplied if the control
signal according to the operation of the arm joystick 4 exceeds a
set value; a bucket control valve (not illustrated) installed in a
path between the second hydraulic pump 2 and the bucket cylinder
and shifted to control a start, stop, and direction change of the
bucket cylinder in response to the operation of the bucket
joystick; and a confluence cutoff proportional valve 8 installed in
a path 7 between the second hydraulic pump 2 and the second arm
control valve 6 and shifted to cut off confluence of the hydraulic
fluid discharged from the second hydraulic pump 2 with the
discharged hydraulic fluid of the first hydraulic pump 1 if
discharge pressures of the first and second hydraulic pumps 1 and 2
exceed a set value.
[0024] According to another embodiment of the present invention,
there is provided a hydraulic control system including first and
second variable displacement hydraulic pumps 1 and 2, an arm
cylinder 3 connected to the first hydraulic pump 1, a bucket
cylinder (not illustrated) connected to the second hydraulic pump
2, an arm joystick 4 and a bucket joystick (not illustrated)
outputting control signals according to operation amounts thereof,
a first arm control valve 5 controlling hydraulic fluid supplied to
the arm cylinder 3 according to an operation of the arm joystick 4,
a second arm control valve 6 controlling the hydraulic fluid that
is supplied from the second hydraulic pump 2 to the arm cylinder 3
if a control signal according to the operation of the arm joystick
4 exceeds a set value, a bucket control valve (not illustrated)
controlling driving of the bucket cylinder according to an
operation of the bucket joystick, and a confluence cutoff
proportional valve 8 making the hydraulic fluid of the second
hydraulic pump 2 join the hydraulic fluid of the first hydraulic
pump 1 if the arm cylinder 3 is singly operated and cutting off a
confluence function if the arm cylinder 3 and the bucket cylinder
are simultaneously operated, the hydraulic control system includes
a first step S100 of reading an arm-in control signal according to
an operation amount of the arm joystick 4, a bucket-in control
signal according to an operation amount of the bucket joystick, and
discharge pressures of the first and second hydraulic pumps 1 and
2; a second step S200 of determining whether the arm-in control
signal exceeds one set value Ap and whether the bucket-in control
signal exceeds the set value Ap; a third step S300 of determining
whether the discharge pressure of the first hydraulic pump 1
exceeds another set value Bp and whether the discharge pressure of
the second hydraulic pump 2 exceeds the set value Bp; and a fourth
step S400 of releasing the confluence function by applying control
signals that are in proportion to the arm-in control signal and the
bucket-in control signal to the confluence cutoff proportional
valve 8 if the arm-in control signal and the bucket-in control
signal exceed the one set value Ap and the discharge pressures of
the first and second hydraulic pumps 1 and 2 exceed the other set
value Bp.
[0025] The confluence cutoff proportional valve 8 operates in a
first state I of cutting off a flow path 7 when the arm joystick 4
and the bucket joystick are simultaneously operated, and in a
second state II of connecting the flow path 7 when the arm joystick
is singly operated.
[0026] The confluence cutoff proportional valve 8 operates in a
first section (a) where movement amounts are controlled to be
gradually increased in proportion to the operation amounts of the
arm joystick 4 and the bucket joystick to release the confluence
function (the second state II of the confluence cutoff proportional
valve 8), in a second section (b) where the confluence cutoff state
(the first state I of the confluence cutoff proportional valve 8)
is maintained according to the increase of the operation amounts of
the arm joystick 4 and the bucket joystick, and in a third section
(c) where movement amounts are controlled to be gradually decreased
in reverse proportion to the operation amounts of the arm joystick
4 and the bucket joystick to be shifted to the confluence function
(the second state II of the confluence cutoff proportional valve
8).
[0027] The confluence cutoff proportional valve 8 may include a
solenoid valve that is shifted to open/close the flow path 7 in
response to an input of an electric signal.
[0028] The confluence cutoff proportional valve 8 may include an
electro proportional control valve that is shifted to open/close
the flow path 7 according to an input of an electric signal.
[0029] Hereinafter, a use example of a hydraulic control system for
a construction machine according to an embodiment of the present
invention will be described.
[0030] As shown in FIG. 2, in the case where an arm is singly
operated, the first arm control valve 5 is shifted in the rightward
direction in the drawing in accordance with the control signal that
is generated through the arm-in operation of the arm joystick 4,
and thus hydraulic fluid Q1 that is discharged from the first
hydraulic pump 1 in accordance with the operation amount of the arm
joystick 4 is supplied to a large chamber 3a of the arm cylinder 3
via the shifted first arm control valve 5. At this time, the
hydraulic fluid that returns from a small chamber 3b of the arm
cylinder 3 is fed back to a hydraulic tank T via the first arm
control valve 5.
[0031] If the operation amount of the arm joystick 4 exceeds a
predetermined value, the second arm control valve 6 is shifted in
the leftward direction in the drawing, and thus hydraulic fluid Q2
that is discharged from the second hydraulic pump 2 joins hydraulic
fluid of a large chamber 2a of the arm cylinder 2 via the
confluence cutoff proportional valve 8 and the second arm control
valve 6 in order (in this case, the amount of hydraulic fluid that
is supplied to the large chamber 3a of the arm cylinder 3 becomes
(Q1+Q2)).
[0032] Accordingly, when the arm is singly operated, the hydraulic
fluid Q2 that is supplied from the second hydraulic pump 2 joins
the hydraulic fluid Q1 that is supplied from the first hydraulic
pump 1 to the arm cylinder 3 (Q1+Q2), the operation speed of the
arm cylinder 3 can be increased.
[0033] Although not illustrated in the drawing, the bucket cylinder
may be driven by the hydraulic fluid that is supplied from the
second hydraulic pump 2 due to the operation of the bucket
joystick.
[0034] On the other hand, if the control signal according to the
operation of the arm joystick 4 and the bucket joystick (not
illustrated) is input and the discharge pressure values of the
first and second hydraulic pumps 1 and 2 exceed the set value, it
is considered that the actual excavating work is done, and a
controller (not illustrated) outputs an electric control signal (a
control signal for cutting off the confluence of the hydraulic
fluids of the first and second hydraulic pumps 1 and 2) to the
confluence cutoff proportional valve 8.
[0035] Through this, the confluence cutoff proportional valve 8 is
shifted in the downward direction in the drawing to cut off the
flow path (supply side flow path provided between the second
hydraulic pump 2 and the second arm control valve 6, and thus the
hydraulic fluid from the second hydraulic pump 2 becomes unable to
join the hydraulic fluid of the first hydraulic pump 1. That is,
the hydraulic fluid from the first hydraulic pump 1 is supplied to
the arm cylinder 3 via the first arm control valve 5, and at the
same time, the hydraulic fluid from the second hydraulic pump 2 is
supplied to the bucket cylinder via a bucket control valve (not
illustrated) (at this time, the hydraulic fluid that is supplied to
the bucket cylinder is supplied without being interfered with the
operation of the arm cylinder 3).
[0036] Hereinafter, a hydraulic control system for a construction
machine according to another embodiment of the present invention,
in which a confluence function is released through a confluence
cutoff proportional valve, will be described with reference to the
accompanying drawings.
[0037] In S100 of FIG. 3, an arm-in control signal according to an
operation amount of the arm joystick 4, a bucket-in control signal
according to an operation amount of the bucket joystick, and
discharge pressures of the first and second hydraulic pumps 1 and 2
are read.
[0038] In S200, it is determined whether the arm-in control signal
exceeds one set value Ap and whether the bucket-in control signal
exceeds the set value Ap.
[0039] In S300, it is determined whether the discharge pressure of
the first hydraulic pump 1 exceeds another set value Bp and whether
the discharge pressure of the second hydraulic pump exceeds the
other set value Bp.
[0040] In S400, if the arm-in control signal and the bucket-in
control signal exceed the one set value Ap and the discharge
pressures of the first and second hydraulic pumps 1 and 2 exceed
the other set value Bp, it is determined that an actual excavating
work is done through recognition of load occurrence in the arm
cylinder 3 and the bucket cylinder.
[0041] Through this, an electric control signal that is in
proportion to the arm-in control signal and the bucket-in control
signal is applied from the controller to the confluence cutoff
proportional valve 8 to shift the confluence cutoff proportional
valve 8 to a first state I, and thus the flow path 7 between the
second hydraulic pump 2 and the second arm control valve 6 is cut
off.
[0042] At this time, the control signal S that is applied to the
confluence cutoff proportional valve 8 may be expressed by the
following equation.
S=(arm-in operation amount.times.C) and (bucket-in operation
amount.times.D)
[0043] Here, C and D are predetermined constants that are applied
to works selected according to various excavating conditions.
[0044] As shown in FIG. 4, the confluence cutoff proportional valve
8 operates in a first section (a) where movement amounts are
controlled to be gradually increased in proportion to the operation
amounts of the arm joystick 4 and the bucket joystick to release
the confluence function, in a second section (b) where the
confluence cutoff state is maintained according to the increase of
the operation amounts of the arm joystick 4 and the bucket
joystick, and in a third section (c) where movement amounts are
controlled to be gradually decreased in reverse proportion to the
operation amounts of the arm joystick 4 and the bucket joystick to
be shifted to the confluence function.
[0045] Accordingly, in the case of performing the excavating work
through simultaneously operation of the arm cylinder 3 and the
bucket cylinder, the confluence function is released by cutting off
the flow path 7 through the confluence cutoff proportional valve 8,
and thus the hydraulic fluid of the second hydraulic pump 2 becomes
unable to join the hydraulic fluid discharged from the first
hydraulic pump 1 any further.
[0046] That is, in the case of simultaneously operating the arm and
the bucket to perform the excavating work, the hydraulic fluid from
the first hydraulic pump 1 is supplied to the large chamber 3a of
the arm cylinder 3 via the first arm control valve 5, and at the
same time, the hydraulic fluid from the second hydraulic pump 2 is
supplied to the large chamber of the bucket cylinder via the bucket
control valve.
[0047] As described above, according to the hydraulic control
system for a construction machine according to an embodiment of the
present invention, in the case where the excavating work is done by
simultaneously operating the arm and the bucket, the hydraulic
fluids, which correspond to powers that are respectively required
in the arm cylinder and the bucket cylinder, are supplied from the
respective hydraulic pumps to the arm cylinder and the bucket
cylinder, and thus pressure loss of the hydraulic pumps can be
prevented to heighten the fuel efficiency.
INDUSTRIAL APPLICABILITY
[0048] As apparent from the above description, the hydraulic
control system for a construction machine according to embodiments
of the present invention can be used in an excavator or a loader,
and in the case where the excavating work is done by simultaneously
operating the arm and the bucket, the hydraulic fluids are made to
be supplied from the respective hydraulic pumps to the arm cylinder
and the bucket cylinder, and thus the pressure loss of the
hydraulic pumps can be prevented to heighten the fuel
efficiency.
* * * * *