Note: Descriptions are shown in the official language in which they were submitted.
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1 -- .
1 SPECIFICATION
CONTROL APPARATUS FOR CONSTRUCTION MACHINE
FIELD OF THE INVENTION
This invention relates to a control apparatus
for a construction machine suitable for use with a
hYdraulic excavation machine, a hYdraulic shovel or a
like machine.
BACKGROUND OF THE INVENTION
Conventionally, in a fluid pressure driving
sYstem for a construction machine such as a hYdraulic
shovel, the opening of a main control valve is remotely
controlled using a hYdraulic or electromagnetic
hYdraulic pilot valve to adjust the flow rate of working
fluid to actuators (for example, in a hYdraulic shovel,
to a boom cYlinder, a stick cylinder and so forth).
However, in order to allow an operator to drive
a pluralitY of actuators, to which different loads are
applied, simultaneously as in a simultaneous operation
in accordance with an intention of the operator, both of
a manual operation of a control lever and adiustment of
a dellverY pressure and a delivery flow rate of an
engine driven variable delivery fluid pressure pump
serving as a fluid pressure energy supply source must be
performed, and verY high skill is required.
~ 220 1 6~6
1 Thus, a load sensing type 1-pump system wherein
a simultaneous operation can be performed comparatively
readilY, that is, a liquid pressure driven system which
adopts main control valves (the difference in pressure
across each of the valves is constant and the flow rate
increases in proportio~ to the opening of the valve) of
the closed center type connected in parallel to each
other, has been proposed recently.
Here, a representative example of such a load
sensing tYpe 1-pump sYstem as mentioned above will be
described with reference to FIG. 7. FIG. 7 is a
schematic view showing a construction of a hydraulic
driving apparatus disclosed in International Publication
No. WO93-16285 (Japanese Patent Application No. Heisei
5-510414).
Operation amount detectors 450A and 450B set
electric signals in response to operation amounts of
manually operable levers 405A and 405B and output the
electric signals to valve flow rate control apparatus
411A and 411B, respectivel.y.
Meanwhile, flow rates of working fluid supplied
from a variable deliverY hYdraulic pump 401 to a
plurality of hYdraulic actuators 403A and 403B via
pressure compensated flow control valves 440A and 440B
are detected by flow rate detectors 410A and 410B, and
this detection information is fed back to the valve flow
rate control apparatus 411A and 411B, respectively.
~1- 220 ~ 626
-- 3
1 Then, control signals outputted from the valve
flow rate control apparatus 411A and 411B to a pump
tilting control apparatus 412 are used to control a pump
regulator 420 for operating a volume variation mechanism
401a of the variable deliverY hYdraulic pump 401 and
effect direction control and flow rate control of the
pressure compensated flow control valves 440A and 440B
by means of the control apparatus 411A and 411B,
respectively.
In particular, the prior art apparatus is
constructed as a system of a flow rate servo tYpe and as
a hYdraulic source sYstem of the energY saving type
(which delivers a pump flow rate lower than a requested
flow rate) wherein the opening of the flow rate control
valve of the highest load pressure is made maximum to
minimize the pressure loss of the flow rate control
valve.
Meanwhile, FIG. 8 is a schematic view showing a
construction of a hydraulically driven apparatus
disclosed in International Publication No. WO93-18308
(Japanese Patent Laid-Open Application No. Heisei 5-
514375). The hydraulically driven apparatus effects
direction control and flow rate control of working oil
supplied from a variable delivery hYdraulic pumP 501 to
a pluralitY of actuators 502a and 502b using flow rate
control valves 503a and 503b, respectivelY.
It is to be noted that the flow rate control
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1 valves 503a and 503b include spools which are displaced
in response to values of currents transmitted thereto
from a controller 510 via solenoid wiring lines 511,
512, 513 and 514.
Meanwhile, an unload valve 507 is connected to
the hYdraulic pump 501, and when a pressure difference
between the delivery pressure of the variable delivery
hydraulic pump 501 and a maximum load pressure extracted
via a shuttle valve 506 exceeds a predetermined value,
the unload valve 507 is opened so that working oil
delivered from the hYdraulic pump 501 is returned to a
tank. It is to be noted that a difference pressure
setting screw 507a is provided on the load pressure
acting side of the unload valve 507.
A fixed orifice 508 for generating a control
pressure in response to a flow rate of the working fluid
flowing out from the unload valve 507 is connected to
the downstream of the unload valve 507, and the control
pressure generated bY the fixed orifice 508 is detected
bY a pressure sensor 515.
Further, a control apparatus for the variable
delivery hydraulic pump 501 is composed of a pump
regulator 509, the controller 510, the pressure sensor
515, a displacement sensor 516 and so forth and is
constructed such that, when the control pressure
generated bY the fixed orifice 508 becomes high, the
deliverY flow rate of the hydraulic pump 501 is
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1 decreased. but when the control pressure becomes low,
the deliverY flow rate is increased.
Furthermore, a directional control valve 530 is
connected in parallel to the unload valve 507 at a
position on the upstream with respect to the fixed
orifice 508. A solenoid operated proportional pressure
reducing valve 531 is controlled by a signal outputted
from the controller 510 in response to an operation
signal from a manual 1Y operable lever apparatus 505 to
control the pilot hydraulic pressure from a pilot
hydraulic pressure source 521 to the directional control
valve 530.
ConsequentlY, the directional control valve 530
is controlled such that, when the operation amount of a
manuallY operable lever 504 i~ small, the opening area
of the directional control valve 530 is large, and as
the operation amount of the manually operable lever 504
increases, the opening area decreases.
AccordinglY, the load sensing control by the
unload valve 507 and the bleed-off control by the
dlrect.or.âl ~ortrol valve o30 are seieciiveiy performed
in response to the operation amount of the manual 1Y
operable lever apparatus 505, and the plurality of
actuators 502a and 502b are driven bY the flow rate
control which makes most of characteristics of the two
controls.
Further, a hYdraulical 1Y driven control
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6 --
1 apparatus which includes a load sensing system which in
turn includes meter-in and meter-out separation valves
and a pressure compensation valve for setting pressure
differences across the valves.
However, the sYstem concepts of such
conventional liquid pressure driven systems as described
above are all directed to saving of energY~ and
components of a conventional hYdraulic apparatus body
and a conventional hydraulic apparatus adjustment system
are individuallY collected to construct a system. In
particular, in the control of actuators, stress is
placed on pump control of a high transmission
efficiencY~ and for control valves (for example, the
pressure compensated flow control valves 440A and 440B
or the flow rate control valves 503a and 503b described
hereinabove), stress is placed on the directional
changing over function because they exhibit a
comparativelY low pressure loss.
Accordingly, mutual interference between the
liquid pressure source and the valve flow rate
adjustment sYstem (mutual interference signifies that,
in a simultaneous operation, the flow rate of an
actuator is varied because the pressure is varied by a
variation of the load to another actuator) has not been
augmented as yet, and the operability (particularly the
fine operability) is insufficient.
Further, a main control valve for a flow rate
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1 adjustment system is used onlY for flow rate adjustment,
and it has not been considered to effect pressure
control by feedback using only a control valve.
However, in such a fluid pressure driven system,
a high inertial load acts frequently, and in such an
instance, the fluid pressure driven system has a
resonance frequency based on a piping characteristic and
the inertial load (which varies in response to the load
or the posture of the machine) and has a problem in that
the system is much likely to be vibrated.
Further, by such a sudden load variation as
occurs when a working apparatus (bucket or the like)
violentlY collides with a hard substance such as a rock
or a sudden manual operation when an emergent situation
occurs, lower to higher harmonics are sometimes produced
on a machine bodY. Consequently, the driving feeling is
not good and improvement in workability cannot be
anticipated.
The present invention has been made in view of
such circumstances as described above, and it is an
obiect of the invention to achieve improvement in manual
operabilitY, augmentation in driving feeling and
improvement in workabilitY of a construction machine.
DISCLOSURE OF THE INVENTION
In order to attain the obiect, a control
apparatus for a construction machine of the present
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1 invention is characterized in that it comprises manuallY
operable means manual 1Y operable by an operator, working
fluid supply means including a hYdraulic pump driven by
a prime mover, driving means including a plurality of
actuators driven by working fluid from the working fluid
supplY means, valve means including a pluralitY of
control valves interposed between the driving means and
the working.fluid supply means for controlling the
driving means, detection means including working fluid
supplY flow rate detection means for detecting a supply
flow rate of the working fluid from the working fluid
supplY means, and valve control means for receiving an
operation command from the manuallY operable means and a
result of detection from the detection means and
controlling the valve means bY a distributor function of
comparing requested flow rate information to the
actuators set by the manually operable means with the
working fluid supply flow rate information from the
working fluid supply means and determining optimal
supplY flow rates to the actuators in response to a
result of the comparison.
With the construction, operation signals from
the valve control means having the distributor function
are outputted as supply flow rate setting commands to
the plurality of control valves, and the actuators
operate with a hYdraulic pressure from the hYdraulic
pump. The valve control means compares, by the
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1 distributor means thereof, requested flow rate
information to the actuators set by the manually
operable means with working fluid supply flow rate
information from the working fluid supply means and
determines optimal supply flow rates to the actuators in
response to a result of the comparison. Consequently,
distribution of the requested flow rates to the
actuators can be realized accuratelY.
The valve control means may include a
distributor which outputs the requested flow rate
signals to the actuators by the manually operable means
as actuator flow rate setting signals when a sum total
of the requested flow rates is lower than the working
fluid supply flow rate, but outputs values obtained by
multiplYing the requested flow rates to the actuators by
a coefficient smaller than 1 as actuator flow rate
setting signals when a sum total of the requested flow
rates is higher than the working fluid supply flow rate.
Thus, by the distributor, based on operation
signals outputted from the operation sYstem to the main
control valves, an actuator flow rate distribution
required by an operator can bè realized with a delivery
flow rate of the pump irrespective of loads to the
actuators. Consequently, improvement in operability,
improvement particularlY in simultaneous operability and
fine operability, can be anticipated, and improvement in
workabilitY can be anticipated and the skill of the
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1 operator can be exhibited sufficiently.
The coefficient smaller than 1 may have
information obtained by normalization of the working
fluid supply flow rate with the sum total of the
requested flow rate information.
The actuator flow rate setting signals set by
the distributor may be set for each work mode of the
construction machine.
In this instance, optimal supply flow rates to
the actuators are determined in response to a work mode,
and distribution of the requested flow rates to the
actuators can be realized accurately. Consequently, the
pluralitY of actuators can be driven at the same time in
accordance with a will of the operator without requiring
a high skill, and the efficiencY in working is improved.
The control apparatus for a construction machine
may be constructed such that the detection means
includes manipulation detection means for detecting
operation conditions of the valve means, and the valve
control means includes correction means for receiving
results of the detection from the manipulation detection
means and correcting the distributor function.
Further, the manipulation detection means maY
include spool position sensors for measuring and feeding
back spool positions of the control valves, load sensing
load pressure sensors for measuring and feeding back
load pressures, and flow rate sensors for measuring and
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1 feeding back flow rates supplied to the actuators. By
such construction, the spool positions of the control
valves can be controlled with a high degree of accuracy.
Each of the load sensing load Pressure sensors
may include a band-pass filter at an output portion
thereof, and this can prevent an overshoot in the spool
position control.
The working fluid supply means may include an
accumulator for accumulating the working fluid on a
deliverY side of the hYdraulic pump. Further, the
working fluid supply means maY Include an unload valve
for bypassing a delivery flow rate of the hydraulic pump
in a no-load condition when a capacitY of the
accumulator exceeds a predetermined amount.
BY the construction described above, a supply
pressure variation can be suppressed low against a
variation in manual operation, a large variation in flow
rate or a sudden variation in flow rate, and mutual
interference in pressure variation between the actuators
is eliminated and lower harmonics or fluctuations of a
construction machine structure can be suppressed and
besides improvement in operability and augmentation in
driving feeling of an operator in a cab can be
anticipated. Further, an unnecessary pump flow rate is
allowed to bypass bY the unload valve, and saving of the
fuel cost can be achleved. Furthermore, a flow rate
higher than the pump delivery flow rate can be supplied
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1 temporarilY by the fluid pressure accumulated in the
accumulator, and this allows improvement in
productivity.
The control apparatus for a construction machine
may be constructed such that the unload valve is
provided in parallel to a working fluid supply path on
the deliverY side of the hydraulic pump while the
accumulator is provided in parallel at a portion of the
working fluid supply path on a downstream side with
respect to a connection point of the unload valve to the
working fluid supply path, and a check valve for
preventing a back flow from the accumulator is
interposed in a portion of the working fluid supply path
between the connection portion of the unload valve and a
connection portion of the accumulator to the working
fluid supply path.
The manually operable means maY include a supplY
pressure setting unit for keeping a pump deliverY
pressure of the hydraulic pump fixed. This allows so-
called fixed supply pressure operation wherein a pump
deliverY pressure command signal programmed in advance
is provided in response to contents of a work, and can
improve the workability and allows an operation which
can esteem the skill of the operabilitY.
The control apparatus for a construction machine
may be constructed such that the working fluid supply
means includes an accumulator for accumulating the
~1 220 1 626
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1 working fluid on a deliverY side of the hYdraulic pump,
and the valve control means includes a distributor which
outputs the requested flow rate signals to the actuators
by the manuallY operable means as actuator flow rate
setting signals when a sum total of the requested flow
rates is lower than the working fluid supply flow rate,
but outputs values obtained by multiplying the requested
flow rates to the actuators by a first coefficient
smaller than 1 as actuator flow rate setting signals
when the sum total of the requested flow rates is higher
than the working fluid supply flow rate, and calculates
a total of an accumulation supply flow rate of the
accumulator and the working fluid supply flow rate as an
allowable supply flow rate and outputs values obtained
by multiplYing the requested flow rates to the actuators
by a second coefficient having information obtained by
normalization of the allowable supplY flow rate with the
sum total of the requested flow rates as actuator flow
rate setting signals.
The control apparatus for a construction machine
may be constructed such that the first coefficient has
information obtained by normalization of the working
fluid supplY flow rate with the sum total of the
requested flow rates, and such that at least one of the
first coefficient and the second coefficient is set for
each work mode of the construction machine.
The control apparatus for a construction machine
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1 may be constructed such that the detection means
includes power supplY side detection means for detecting
an operation condition of the working fluid supply
means, and the control means includes power supply side
control means for receiving a result of the detection
from the power supplY side detection means and
controlling the working fluid supply means.
Further, power supply side detection means may
include a rotation condition sensor for detecting a
rotation condition of the prime mover, an output power
sensor for detecting an output power condition of the
prime mover, and a working fluid pressure sensor for
detecting a pressure of the working fluid from the
working fluid supply means.
Meanwhile, another control apparatus for a
construction machine of the present invention is
characterized in that it comprises manually operable
means manual 1Y operable by an operator, at least one
variable delivery liquid pressure pump driven by an
engine, a plurality of liquid pressure actuators driven
bY pressure fluid delivered from the variable deliverY
liquid pressure pump, a plurality of main control valves
interposed between the liquid pressure actuators and the
variable deliverY liquid pressure pump for controlling
flow rates and directions to the liquid pressure
actuators, an accumulator provided in a liquid path
between the variable delivery liquid pressure pump and
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1 the main control valves for accumulating the pressure
fluid, an unload valve provided in the liquid path
between the variable deliverY liquid pressure pump and
the main control valves for allowing bYpassing of a
deliverY flow rate of the variable delivery liquid
pressure pump in a no-load condition when a capacity of
the accumulator approaches a maximum value of the
capacity, a distributor including first calculation
means for outputting requested flow rate signals to the
actuators by the manually operable means as they are as
actuator flow rate setting signals when a sum total of
the requested flow rates to the actuators by the
manuallY operable means is lower.than a delivery flow
rate of the variable delivery liquid pressure pump, but
outputting, when the sum total of the requested flow
rates is higher than the pump delivery flow rate, values
obtained by multiplying the requested flow rates to the
liquid pressure actuators by a value obtained by
dividing the pump delivery flow rate by the sum total of
the requested flow rates as actuator flow rate setting
signals and second calculation means for multiplying the
requested flow rates to the actuators by a value
obtained by dividing an allowable supplY flow rate
calculated as a total of an accumulation supply flow
rate of the accumulator and the pump deliverY flow rate
by the sum total of the requested flow rates and
outputting results of the multiplication as actuator
~ 220~626
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l flow rate setting signals, a supplY pressure setting
unit provided for the manually operable means for
keeping the pump delivery output fixed, a valve
controller for receiving the actuator flow rate setting
signals from the distributor and supplYing operation
signals to the main control valves, a manipulation side
sensor group provided for the valve controller and
including spool position sensors for measuring and
feeding back spool positions of the main control valves,
load sensing load pressure sensors with a band-pass
filter for measuring and feeding back load pressures,
and flow rate sensors for measuring and feeding back
flow rates supplied to the liquid pressure actuators, a
power supply side sensor group including a rotation
speed sensor for measuring an engine speed, a rack
opening sensor for measuring a rack opening of an engine
fuel pump, a tilting angle sensor for measuring a pump
tilting angle, a delivery pressure sensor for measuring
a pump deliverY pressure, a supplY pressure sensor for
measuring a system supply pressure and an accumulator
capacity sensor for measuring a capacitY of the
accumulator, first command means for generating a
tilting angle command signal for the variable delivery
liquid pressure pump based on a sum of a difference
between a pressure set by the supply pressure setting
unit and the feedback signal from the supply pressure
sensor and an integrated value of the difference, second
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1 command means for selecting a maximum signal from among
the suPplY pressure setting unit and the load sensing
load pressure sensors, determining a value obtained by
addition of a fixed value to a value of the maximum
signal as a command signal when the value of the maximum
signal continues for more than a fixed period of time
and generating a tilting angle command signal for the
variable delivery liquid pressure pump based on a sum of
a difference between the command signal and the feedback
signal from the supplY pressure sensor and an integrated
value of the difference, third command means for
generating a signal to oPen the unload valve to allow
bypassing of the deliverY flow rate of the variable
deliverY liquid pressure pump in a no-load condition
when a supplY pressure rises higher bY a certain value
than a preset value and the capacity of the accumulator
is in the proximitY of a maximum value thereof, but to
close the unload valve when the supply pressure drops
lower by a certain value than the preset value or the
capacitY of the accumulator drops to a value in the
proximitY of a minimum value thereof, fourth command
means for generating an allowable tilting angle command
signal for the variable delivery liquid pressure pump
within a range of an output power of the engine as a
function of the output deliverY power of the engine and
an efficiencY characteristic of the engine-pump, fifth
command means for generating a tilting angle command
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1 signal for the variable deliverY liquid pressure pump
for securing a pump flow rate which increases in
proportion to a flow rate request of an operator, and a
. pump controller for selecting a lowest one of the
generated command signals as a tilting angle command
signal for the variable delivery liquid pressure pump
and positioning a pump tilting angle based on a
difference between the selected tilting angle command
signal and the feedback signal from the tilting angle
sensor.
With the construction described above,
improvement in response, safety and flow rate control
accuracy of the system can be anticipated. By such
addition of the high speed pressure controlling function
of the main control valves, higher harmonics of a front
working machine or a machine bodY can be suppressed, and
the simultaneous operability, the fine operabilitY and
the driving feeling of an operator in a cab can be
augmented.
Further, by liquid pressure electronic control
systematization wherein function allotments between
liquid pressure apparatus and electronicallY controlled
apparatus are made definite compositelY improving
conventional liquid pressure driven systems from the
systematic point of view, improvement in operability,
augmentation in driving feeling and improvement in
workabilitY can be achieved.
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1 A further control apparatus for a construction
machine of the present invention is characterized in
that it comprises manuallY operable means manually
operable by an operator, a hydraulic pump driven by a
prime mover, a pluralitY of actuators driven by working
fluid from the hydraulic pump, a plurality of control
valves for controlling the actuators, and valve control
means for comparing requested flow rate information to
the actuators set by the manually operable means with
working fluid supply flow rate information from the
hydraulic pump, determining optimal supplY flow rates to
the actuators based on results of the comparison and
controlling the valve means with the optimal supply flow
rates.
By the construction, the pluralitY of actuators
can be driven at the same time in accordance with a will
of an operator without requiring a high skill, and the
efficiency in working is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic hYdraulic circuit diagram
showing essential part of a control apparatus for a
construction machine as a first embodiment of the
present invention;
FIG. 2 is a schematic block diagram showing a
general construction of the control apparatus for a
construction machine as the first embodiment of the
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1 present invention;
FIG. 3 is a block diagram showing a control
system for a manipulation system in the control
apparatus for a construction machine as the first
embodiment of the present invention;
FIG. 4 is a view showing a modification to the
control aPParatUS for a construction as the first
embodiment of the present invention and is a view
showing a data table of coefficients set for each work
mode;
FIC. 5 is a view showing another example of a
hYdraulic circuit applicable to the control apparatus
for a construction machine as the first embodiment of
the present invention;
FIG. 6 is a schematic hYdraulic circuit diagram
of a control apparatus for a construction machine as a
second embodiment of the present invention;
FIG. 7 is a hydraulic circuit diagram showing an
example of a conventional liquid pressure driven circuit
for a construction machine; and
FIG. 8 is a hYdraulic circuit diagram showing
another example of a conventional liquid pressure driven
circuit for a construction machine.
BEST FORMS IN EM~ODYING THE INVENTION
In the following, the Present invention will be
described in connection with embodiments thereof with
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- 21 -
reference to FIGS. 1 to 6.
(1) Description of the First Embodiment
Referring to FIG. 1, an apparatus shown includes
a diesel engine (hereinafter referred to simply as
engine) 1 as a prime mover, a variable delivery
hydraulic pump (hereinafter referred to simply as
hydraulic pump) 2 serving as a fluid pressure pump
driven bY the engine 1, and a plurality of hydraulic
actuators 7A and 7B driven by high pressure working
fluid delivered from the hydraulic pump 2.
A pluralitY of main control valves (closed
center valves) 6A and 6B are interposed between the
hydraulic pump 2 and the hYdraulic actuators 7A and 7B
so that the directions and the flow rates of working oil
to be supplied to the hydraulic actuators 7A and 7B may
be controlled in response to an operation command signal
from a manual operation system operated by an operator.
In particular, the actuators 7A and 7B operate
in response to manually operated conditions of manually
operable levers 30A and 30B which serve as manually
operable means.
Flow rate sensors 106A and 106Bwi th a check
valve are provided on the upstream sides of the main
control valves 6A and 6B, respectivelY.
Further, connected in parallel in oil paths
between the hydraulic pump 2 and the main control valves
6A and 6B are an unload valve 3 which allows bypassing
~ 2 2 !~ 1 6 2 6
- 2Z -
1 of working fluid delivered from the hydraulic pump 2 to
a hYdraulic tank 9 when no load is applied and an
accumulator 5 for accumulating working fluid delivered
from the hYdraulic pump 2 therein.
Here, a working fluid supplY path (oil path) on
the deliverY side of the hydraulic pump 2 is branched
into two directions on the downstream side, and the
unload valve 3 is provided for one of the two oil paths
while the accumulator 5 is provided for the other oil
path via a check valve 4. It is to be noted that the
check valve 4 is provided to prevent a back flow of
working fluid from the accumulator 5.
Further, the present apparatus inciudes control
means for controlling operation of the actuators 7A and
7B, hydraulic pump 2, main control valves 6A and 6B and
so forth. Operation of the main control valves 6A and
6B from among those elements is controlled bY valve
control means 31 provided in the control means.
The valve control means 31 includes a
distributor 31a which receives operation commands from
the manuallY operable levers 30A and 30B and results of
detection of sensors which will be hereinafter
described, compares requested flow rate information to
the actuators 7A and 7B set by the manuallY operable
levers 30A and 30B with working fluid supply flow rate
information of the hYdraulic pump 2 and determines
optimal supplY flow rates to the actuators 7A and 7B in
220 1 626
- 23 -
1 response to results of the comparison.
Then, the d~stributor 31a outputs, when the sum
total of the requested flow rates for working fluid to
the actuators 7A and 7B by the operation conditions of
the manuallY operable levers 30A and 30B is lower than
the deliverY flow rate of the hYdraulic pump 2, the
requested flow rate signals to the actuators 7A and 7B
by the manuallY operable levers 30A and 30B as they are
as actuator flow rate setting signals. On the other
hand, when the sum total of the requested flow rates is
higher than the pump delivery flow rate, the distributor
31a multiplies the requested flow rates to the actuators
7A and 7B bY a value ~ (~ < 1: first coefficient)
obtained by dividing the pump deliverY flow rate by the
sum total of the requested flow rates, sets values
obtained bY the multiplication as working fluid
requested amounts newlY, and outputs the thus set
requested flow rate signals as actuator flow rate
setting signals.
Further, the distributor 31a calculates a sum of
the accumulation supplY flow rate of the accumulator 5
and the delivery flow rate from the hYdraulic pump 2 as
an allowable supply flow rate, multiplies the requested
flow rates to the actuators 7A and 7B by a value ~
obtained bY dividing the allowable supplY flow rate by
the sum total of the requested flow rates, sets values
obtained by the multiplication newlY as working fluid
~ 220 1 626
-24-
1 requested amounts, and outPuts the requested flow rate
signals as actuator flow rate setting signals.
The present apparatus further includes a supplY
pressure setting unit 20 for keeping the delivery
pressure of the hydraulic pump 2 to a fixed level.
Further, spool position sensors 107A and 107B
for detecting spool positions (that is, valve openings)
are provided for the main control valves 6A and 6B,
respectivelY1 and feedback systems for spool positions
load pressure feedback sYstems with a band-pass filter
and flow rate feedback systems are provided for valve
controllers (correction means) 32A and 32B for
outputting operation signals to the main control valves
6A and 6B, respectivelY.
In particular, manipulation detection means (or
a manipulation side sensor group) including the flow
rate sensors 106A and 106BWi th a check valve (which maY
be replaced bY actuator velocity sensors or position
sensors) for measuring and feeding back flow rates
supplied to the actuators 7A and 7B, respectively, the
spool position sensors 107A and 107B for measuring and
feeding back spool positions (valve openings) of the
main control valves 6A and 6B, respectivelY, and A port
load pressure sensors 108A and 108B and B port load
pressure sensors 109A and 109B for load sensing each
including a band-pass filter 200 (refer to FIG. 3) for
measuring and feeding back a load pressure on the output
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- 25 -
1 side of a main control valve is provided.
Further, power supplY side detection means (or a
power supply side sensor group) including a rack opening
sensor (output sensor) 100 for measuring a rack opening
of a fuel pump of the engine 1, an engine speed sensor
(rotating condition sensor) 101 for measuring the speed
of the engine l, a pump delivery pressure sensor
(working fluid pressure sensor) 102 for measuring the
deliverY output of the hydraulic pump 2, a pump tilting
angle sensor 103 for measuring the tilting angle of the
hYdraulic pump 2, a supply pressure sensor 104 for
measuring the supply pressure from the check valve 4 and
an accumulator capacity sensor 105 for measuring the
accumulator capacity is provided.
Further, the control means of the present
apparatus includes power supply side control means (pump
controller) 26. The pump controller 26 includes first
command means a, second command means b, third command
means c, fourth command means d and fifth command means
e.
The pump controller 26 has a function of
selecting and using a lowest one of signals emitted from
the command means a, b, d and e mentioned above as a
tilting angle command signal for the hydraulic pump 2
and positioning the pump tilting angle based on a
difference between the selected tilting angle command
signal and a feedback signal from the tilting angle
220 1 626
- 26 -
1 sensor 103 of the hydraulic pump 2.
Here, the command means a to e mentioned above
will be described. The first command means a is means
for generating a tilting angle command signal ~p for the
hYdraulic pump 2 based on a sum of a difference between
.a pressure set by the supplY pressure setting unit 20
and a feedback signal from the supply pressure sensor
104 and an integrated value of the difference, and has a
function as a PI controller.
The second command means b is means for
selecting a signal Plmax having highest load information
from within load information detected bY the A port load
pressure sensors 108A and 108B and the B port load
pressure sensors 109A and 109B for load sensing of the
main control valves 6A and 6B in addition to the supply
pressure setting unit 20, determining, when this value
continues for more than a fixed period of time, a value
obtained by adding, to this value, a fixed value P10 as
a command signal and generating a tilting angle command
signal ~pls for the hYdraulic pump 2 based on a sum of a
difference between the command signal and a feedback
signal from the supply pressure sensor 104 and an
integrated value of the difference. AccordinglY, also
this second command means b has a function as a PI
controller.
The third command means c is means for
generating a signal for opening, when the supply
220 1 626
- 27 -
1 pressure rises higher than a certain value higher than a
preset value and the accumulator capacity is in the
proximitY of the maximum value thereof, the unload valve
3 to allow bypassing of the delivery flow of the
hYdraulic pump 2 in a no-load condition, but closing the
~unload valve 3 when the supply pressure drops lower than
a certain value lower than the preset value or the
accumulator capacity drops to a value in the proximity
of the minimum value thereof.
The fourth command means d is means for
generating an allowable tilting angle command signal ~11
for the hydraulic pump 2 within a range of the output
power of the engine 1 as a function of three parameters
including the output power of the engine 1, the deliverY
pressure of the hYdraulic pump 2 and the efficiencY
characteristic of the engine-pump.
The fifth command means e is means for
generating a tilting angle command signal ~f for the
hydraulic pump 2 for securing a pump flow rate which
increases in proportion to a flow rate request of an
operator.
By the way, when notice is taken of functions of
the present apparatus, it can be roughly divided into,
as shown in FIG. 2, an operation system which is
operated by an operator of the construction machine, a
power supply system for supplying a hYdraulic pressure,
and a manipulation system for controlling the hydraulic
220 1 626
- 28 -
1 pressure. Those systems will be hereinafter described
with reference to FIGS. 1 and 2.
(a) Power Supply System
The diesel engine 1 which is a power source of
the power supplY system has an engine speed set
~corresponding to loads 8A and 8B by an engine throttle
10. In particular, an engine speed controller 11
outputs a command signal in response to an opening of
the engine throttle 10, and positions the rack opening
of the fuel pump in response to a feedback signal from
the engine speed sensor 101 and another feedback signal
from the rack opening sensor 100 of the fuel pump to
automatically set the engine speed.
The power supply side control means (pump
controller) 26 is formed from a supply pressure
controller 21, an engine load limiter 22, a pump flow
controller 23, a minimum signal selector 24 and a pump
tilting angle regulator 25.
Then, the hydraulic pump 2 is controlled by the
pump controller 26 so that it supplies a supply pressure
conforming to the loads 8A and 8B similarlY to the
engine 1. A supply pressure signal is set bY the supply
pressure setting unit 20 and outputted to the supply
pressure controller 21 for the hYdraulic pump 2 and the
accumulator 5.
In particular, the supplY pressure controller 21
sets a tilting angle command signal ~p for the hydraulic
~ 220 1 626
- 29 -
1 pump 2 (first command means a) using a sum of a
difference between a pressure set by the supply pressure
setting unit 20 and a feedback signal from the supply
pressure sensor 104 and an integrated value of the
difference (PI control).
~ eanwhile, the supplY pressure controller 21
selects a maximum signal Plmax from among the load
pressure sensors 108A, 108B, 109A and 109B for load
sensing, sets, when this value continues for more than a
fixed period of time, a value obtained by adding to this
value a fixed value P10, and sets a tilting angle
command signal ~pls for the hydraulic pump 2 (second
command means b) using a sum of a difference between the
pressure set bY the supply pressure setting unit 20 and
a feedback signal from the supplY pressure sensor 104
and an integrated value of the difference (PI control).
Further, the supply pressure controller 21 has,
in addition to the tilting angle operation algorithm for
the hYdraulic pump 2 described above, an unload valve
operation algorithm for opening, when the supply
pressure rises higher than a certain value higher than a
preset value and the accumulator capacity is in the
proximitY of the maximum value thereof, the unload valve
3 to allow bypassing of the variable deliverY type pump
flow in a no-load condition, but closing the unload
valve 3 when the supplY pressure drops lower than a
certain value lower than the preset value or the
~ ~ 2201626
- 30 -
1 accumulator capacity drops to a value in the proximity
of the minimum value thereof (third command means c).
It is to be noted that the check valve 4 is
provided to prevent high pressure working oil from
flowing back from the accumulator 5 when the hydraulic
pump 2 is put into an unloaded condition.
The engine load limiter 22 is provided in place
of a conventional power mode selector and sets an
allowable tilting angle command signal ~11 for the
hYdraulic pump 2 within a range of the engine output
power as a function of the pump capacity, an output Ne
of the engine speed sensor 101, an output Pp of the pump
delivery pressure sensor 102 and the efficiencY
characteristic of the engine-pump (fourth command means
d).
The pump flow controller 23 is similar to a
conventional positive flow rate control and outputs a
tilting angle command signal ~f for the hYdraulic pump 2
in order to secure a pump flow rate which increases in
proportion to a flow rate request of an operator. The
pump controller 26 can regard the tilting angle command
signal ~f as one of feedforward signals (feedforward)
(fifth command means e).
Then, the minimum signal selector 24 selects one
of the pump tilting angle command signals ~p, ~pls, ~11
and ~f generated from the means described above which
sets the pump tilting angle to the lowest value.
~. 220 1 626
- 31 -
1 The pump tilting angle regulator 25 receives an
output signal of the minimum signal selector 24 as an
input signal thereto and positions the tilting angle of
the hydraulic pump 2 in response to a feedback signal
from the pump tilting angle sensor 103.
~ As described above, the present power supply
sYstem is constructed as a power supply system which
exhibits a large energY storage for securing a supply
power to the manipulation SYstem which will be
hereinafter described and hence has a so-called low-pass
system characteristic.
(b) Manipulation System
The distributor 31a which functions as valve
control means outputs actuator flow rate setting signals
Qsa, Qsb, ... to the valve controllers 32A, 32B, ... in
response to a situation of the power supply system when
actuator flow rate request signals Qra, Qrb, ... are
inputted from the manually operable levers (manual 1Y
operable means) 30A and 30B (onlY two are shown here).
It is to be noted that the actuator flow rate
request signals Qra, Qrb, ... are signals set
independentlY of each other, and prioritY degrees of
working oil to be supplied to the actuators 7A and 7B
are set depending upon the magnitudes of requested flow
rates rePresented bY the signals.
Then, means for setting such actuator flow rate
setting signals Qsa, Qsb, ... as mentioned above is
- 32 - 220 1 626
1 available for each of the two following cases.
~ When the sum total of the requested flow
rates to the hydraulic actuators 7A, 7B, ... by the
manuallY operable levers 30A, 30B, ... is lower than the
deliverY flow rate of the hYdraulic pump 2, the
requested flow rate signals to the actuators 7A and 7B
by the manuallY operable levers 30A, 30B, ... are used
as theY are as actuator flow rate setting signals. In
other words, Qsa = Qra, Qs~ = Qrb, ...
On the other hand, when the sum total of the
requested flow rates is higher than the pump delivery
flow rate, the requested flow rates set by the manually
operable levers 30A and 30B are multiplied bY [pump
delivery flow rate]/[sum total of requested flow rates]
= a (a < 1: first coefficient), and values obtained by
the calculation are outputted as actuator flow rate
setting signals to the valve controllers 32A, 32B, ...
In other words, Qsa = aQra, Qsb = aQrb,
~ An allowable supply flow rate Qs of the power
supplY system = function F(Xa, Qp, Ps) > Qp is
calculated based on an output signal Xa of the capacity
detection sensor 105 for the accumulator 5, a pump
delivery flow rate signal Qp = function F(Ne, ~, Pp) and
an output signal Ps of the supply pressure sensor 104,
and the requested signals to the actuator 7A, 7B, ...
are multiplied by a value ~ (~ < 1: second coefficient)
obtained bY dividing the allowable supply flow rate Qs
~ 220 1 626
- 33 -
1 bY the sum total of the requested flow rates to make
actuator flow rate setting signals. In other words, Qsa
= ~Qra, Qsb = ~Qrb, ...
ConsequentlY, an actuator flow rate distribution
(including priorities) requested bY an operator can be
realized accurately, and the operability is improved
very much and improvement in workability is anticipated.
The present manipulation sYStem is characterized
in that, different from a conventional hydraulically
driven apparatus for a construction machine, the main
control valves 6A and 6B have a higher response and
multiple functions so that operation of the load driving
hydraulic actuators 7A and 7B is controlled bY
electronically controlling a single main control valve
to control all of the flow rate and pressure variations
arising from manual operation and load variations, and
the manipulation sYStem minimizes hYdraulic control
valves of a single function to the utmost and is
directed to make unitarY member/system functions precise
and improve the accuracy and reliability.
Further, since such a distributor 31a as
described above is provided, flow rate distribution or
control of the hYdraulic pump 2 by complicated manual
operations of the manually operable levers 30A and 30B
upon simultaneous operation which are conventionallY
operated manually and adiusted by an operator relying
upon the experience of the operator itself can be set to
~ 220 1 626
- 34 -
1 desired manners of the operator based on contents of the
works. In other words, different priorities can be
provided to operations o~ the actuators 7A and 7B
depending upon the contents of the works.
ConsequentlY, the manipulation system can
cooperate with the power supply system described above
to automatical 1Y effect accurate flow rate control
irrespective of the loads 8A and 8B onlY bY manual 1Y
operating the manually operable levers 30A and 30B while
the operator places stress on grasping of a load
condition of the working machine.
(c) Valve Control System
Subsequently, operation of the valve control
system will be described taking notice of the actuator
(hydraulic cylinder) 7A with reference to FIG. 3.
First, the actuator flow rate setting signal Qsa
outputted from the distributor 31a is inputted to the
valve controller 32A. Meanwhile, a flow rate signal
Qsaa to the actuator 7A is fed back by a flow rate
sensor 106A with a check valve. Then, a signal (P
control signal) obtained by multiplYing a difference
signal between the signal Qsa and the signal Qsaa bY a
constant Kp, another signal (I control signal) obtained
by multiplYing an integrated value of the difference
signal between the signal Qsa and the signal Qsaa by a
constant 1/T and a further signal F(Qsa) which is a
feedforward signal of the signal Qsa are added.
220 1 626
- 35 -
1 It is to be noted that the flow rate of the main
control valve 6A maY alternatively be calculated from,
in place of the flow rate sensor 106A with a check
valve, a pressure difference (Ps - Plla or Ps - P12a)
across the main control valve 6A, an output Xca of the
spool position sensor 107A of the main control valve 6A
or the like.
Further, as described hereinabove, the valve
control system has a large number of resonance and
antiresonance points because the mass loads 8A and 8B
which vary over large extents are driven, and
particularly since a rocking phenomenon having a low
frequency deteriorates the driving feeling, a signal
Plla from the A port load pressure sensor 108A of the
main control valve 6A and a signal P12a from the B port
load pressure sensor 109A of the main control valve 6A
are fed back to the valve controller 32A via the band-
pass filters 200. In other words, the present system is
a dynamic pressure feedback system.
Finally, the main control valve (3-stage
amplification type main control valve) 6A can feed back,
since the signal Xca of the spool position (spool
opening) which increases in proportion to an input
current value Xci to the servo valve for the main
control valve is obtained from the spool position sensor
107A, this signal Xca to the valve controller 32A to
position the spool of the main control valve 6A so that
~ 220 1 626
- 36 -
1 the signal Qsaa which is equal to the actuator flow rate
setting signals Qsa can be obtained automatically.
The present system is a servo mechanism of the
automatic flow rate control type replacing conventional
flow rate adiustment to the actuators 7A and 7B
performed by manual operations, and can be improved in
terms of the resFonse, safety and accuracY in flow rate.
Subsequently, a modification to the first
embodiment of the present invention will be described
with reference to FIG. 4. The present modification is
constructed in a substantially similar manner to that of
the first embodiment described above, and principally,
differences thereof from the first embodiment will be
described below. The present modification is
constructed such that the actuator flow rate setting
signals Qsa and Qsb set bY the distributor 31a are set
for each work mode of the construction machine (for
example, an excavation work mode, a house demolition
work mode and so forth).
In particular, in the first embodiment described
above, when the sum total of requested flow rates to the
hydraulic actuators 7A, 7B, ... by the manuallY operable
levers 30A, 30B, ... is higher than the pump deliverY
flow rate, either ~ the first coefficient ~ is
calculated by [pump delivery flow rate]/[sum total of
requested flow rates], and the requested flow rates set
by the manually operable levers 30A, 30B, ... are
~ . 220 1 626
- 37 -
1 multiplied by the first coefficient a to set the
actuator flow rate setting signals as Qsa = aQra, Qsb =
aQrb~ ..., or ~ the second coefficient ~ is calculated
by [allowable supply flow rate]/[sum total of requested
flow rates], and the requested flow rates set by the
manuallY operable levers 30A, 30B, ... are multiplied bY
the second coefficient ~ to set the actuator flow rate
setting signals as Qsa = ~Qra, Qsb = ~Qrb, ...
In this instance, the coefficients (first
coefficient a or second coefficient ~) by which the
requested flow rates Qra, Qrb, ... to the actuators 7A
and 7B are multiplied have a value equal for all of the
actuators 7A and 7B. In particular, in the case of
described above, all of Qra and Qrb are multiplied
uniformlY by the first coefficient a, and in the case of
, all of Qra and Qrb are multiplied uniformlY by the
second coefficient ~.
By the way, since the requested flow rates Qra,
Qrb, ... are all set in response to manually operated
conditions of the manually operable levers 30A and 30B,
. while different priorities are applied already to
operations of the actuators 7A, 7B, ... depending upon
the magnitudes of the set request signals Qra, Qrb, ....
if the first coefficient a or the second coefficient
is set individual 1Y for each actuator, then the
priorities of the individual actuators can be made
definite and the workabilitY is improved. In short, if,
~ 220 1 626
- 38 -
1 depending upon the mode of the work (that is, the work
mode), not the requested flow rates Qra, Qrb, ... set in
response to manual 1Y operated conditions of the manual 1Y
operable levers 30A and 30B are corrected using the
coefficient a (or ~) of the same value, but the actuator
.flow rate setting signals Qsa, Qsb, ... are set using
coefficients obtained by weighting the requested flow
rates Qra, Qrb, ... in accordance with the mode of the
work, then the operability and the workability can be
further improved.
Therefore, in the present modification, the
coefficient a (or ~) bY which the requested flow rates
Qra and Qrb are multiplied is multiplied by correction
coefficients kij which are set for the individual
actuators in response to the actuators or the mode of
the work (that is, the work mode).
Here, the correction coefficients kij will be
described. The correction coefficients kii are set
depending upon the actuator (i) and the work mode (i),
and can be represented as kii = F(i, i).
In particular, the distributor 31a has such a
data table as shown in FIG. 4 set therein, and in the
data table, the correction coefficients kii set
depending upon the actuator number i and the work mode
number i are stored in the form of a table.
Here, the work mode is a work mode set
arbitrarily by an operator, and such modes as, for
' ~~ 220 1 626
- 39 -
1 example, an excavation mode for i = 1 and a house
demolition mode for j = 2 are set. The operator can
perform setting of a work mode or changing of a set work
mode by manual 1Y operating a manually operable member in
an operator cab, and priorities suitable for each work
~mode can be set for the individual actuators (i = 1, 2,
...).
Meanwhile, i is a number indicating an actuator,
and where the construction machine is, for example, a
hydraulic shovel, i = 1 represents a boom cylinder, i =
2 represents a stick cylinder, i = 3 represents a bucket
cylinder, and i = 4 represents a swing motor.
If an operator elects, for example, the
excavation mode ti = 1) as a work mode, then correction
coefficients kll, k2l, ... are set for the boom cylinder
(i = 1), the stick cYlinder (i = 2), ..., respectively.
For example, if an operator selects the
excavation mode (j = 1) as the work mode, then the
correction coefficients kll, k2l, ... are set for the
boom cylinder (i = 1), the stick cylinder (i = 2), ...
Accordingly, when the sum total of the requested
flow rates to the hydraulic actuators 7A, 7B, ... by the
manually operable levers 30A, 30B, ... is higher than
the pump delivery flow rate, ~ the first coefficient a
is calculated by [pump delivery flow rate]/[sum total of
requested flow rates], and the first coefficient a, the
requested flow rates Qra, Qrb, ... set by the manually
.
220 1 626
- 40 -
1 operable levers 30A, 30B, ... and the correction
coefficients k~, k2~, ... set for the individual
actuators are multiplied by each other to set the
actuator flow rate setting signals Qsa, Qsb, ... In
particular, the actuator flow rate setting signals are
set as Qsa = a k~ Qra, Qsb = a k~2 Qrb, ...
On the other hand, also ~ when the second
coefficient ~ is calculated by [allowable supply flow
rate]/[sum total of requested flow rates], the actuator
flow rate setting signals are set as Qsa = ~ k~ Qra,
Qsb = ~ k~2 Qrb, ... in a similar manner as described
above.
Then, by setting the actuator flow rate setting
signals Qsa and Qsb to be set by the distributor 31a
using the correction coefficients ki~ set individually
for each work mode and each actuator of the construction
machine, a flow rate distribution to the actuators
suitable for the work mode of the construction machine
can be realized. Particularly upon simultaneous
operations of a pluralitY of actuators, operation on
which a will of an operator is reflected can be
realized.
Consequently, operation conforming to the will
of the operator can be performed without requiring anY
skill, and the workability is improved very much.
It is to be noted that, while, in the example
described above, the correction coefficients kii by
~ 220 1 626
- 41 -
1 which the first coefficient ~ and the second coefficient
are multiplied are set to equal values, the correction
coefficients kij may otherwise be set different values
between the first coefficient a and the second
coefficient ~.
~ By the waY, in the first embodiment and the
modification to it described above, one three way
solenoid valve is used for one actuator for each of the
main control valves, and the direction and the flow rate
of working fluid to be supplied to a hydraulic actuator
is controlled by operation control of the three waY
solenoid valve. However, the present invention is not
limited to such apparatus that have the construction
just described, and, for example, as shown in FIG. 5,
separate control tYpe valve means which employs a
plurality of two way solenoid valves 201 to 204 to
control supply of working fluid to an actuator 207 and
~ delivery of working fluid from the actuator 207
independently of each other may be provided.
Here, such separate control type valve means as
shown in FIG. S is provided taking notice of the
operation response of the actuator 207 and can perform
supply or delivery of working fluid rapidlY and
accurately by individual 1Y controlling the solenoid
valves 201 to 204 provided independentlY of each other.
Meanwhile, reference numeral 205 denotes a
velocitY sensor, 207 a hydraulic actuator, 208 and 20
220 ~ 626
- 42 -
1 denote each a hydraulic PreSsure sensor, 210 and 211
denote each a valve position sensor, and 212 and 213
denote each a check valve (directional control check
valve).
In the present hydraulic circuit, control
signals to the solenoid valves 201 to 204 are set by
control means not shown based on detection information
from the sensors 205, 208 to 211 to control the change-
over conditions of the solenoid valves 201 to 204.
It is to be noted that a solenoid valve of the
spool type which is superior in response and stability
is used for the two way solenoid valves 201 to 204.
While a solenoid valve of the poppet valve type having a
high liquid tightness maY possiblY be used for the
solenoid valves 201 to 204, it is considered that a
solenoid valve of the spool type having a stable
response is more suitable.
(2) Description of the Second Embodiment
Subsequently, a second embodiment of the present
invention will be described. The present second
embodiment is constructed in a similar manner to the
first embodiment principally except that the accumulator
5 is omitted as shown in FIG. 6.
Also the unload valve 3, the check valve 4, the
supply pressure sensor 104, the accumulator capacity
sensor 105 and so forth which are provided incidentally
to the accumulator 5 are omitted. Those elements having
220 1 626
- 43 -
1 same reference symbols as those of FIG. 1 applied
thereto in FIG. 6 are same elements or substantially
same elements as those described in the first
embodiment, and detailed description of them is omitted.
Thus, the distributor 31a outputs, when the sum
total of requested flow rates of working fluid to the
actuators 7A and 7B by manually operated conditions of
the manuallY operable levers 30A and 30B is lower than
the delivery flow rate of the hydraulic pump 2, the
requested flow rate signals to the actuators 7A and 7B
by the manual 1Y operable levers 30A and 30B as they are
as actuator flow rate setting signals. However, when
the sum total of the requested flow rates is higher than
the pump delivery flow rate, the requested flow rates to
the actuators 7A and 7B are multiplied by a value a (a <
1: coefficient) obtained by dividing the pump delivery
flow rate by the sum total of the requested flow rates,
and results obtained by the multiplication are newly set
as working fluid requested amounts. Then, the
distributor 31a outputs the requested flow rate signals
as actuator flow rate setting signals.
In other words, the distributor 31a which
functions as the valve control means outputs actuator
flow rate setting signals Qsa, Qsb, ... to the valve
controllers 32A, 32B, ... in response to a situation of
the power supply system when actuator flow rate request
signals Qra, Qrb, ... from the manually operable levers
220 1 626
- 44 -
1 (manual 1Y operable means) 30A and 30B are inputted.
It is to be noted that the actuator flow rate
request signals Qra, Qrb, ... are signals set
independentlY of each other, and the priority degrees of
working oil to be supplied to the actuators 7A and 7B
.are.set..depending upon the magnitudes of the requested
flow rates represented by the signals.
Then, when the sum total of the requested flow
rates to the hydraulic actuators 7A, 7B, ... by the
manually operable levers 30A, 30B, ... is lower than the
delivery flow rate of the hYdraulic pump 2, the
requested flow rate signals to the actuators 7A and 7B
by the manual 1Y operable levers 30A, 30B, ... are used
as theY a.re as actuator flow rate setting signals. In
other words, Qsa = Qra, Qsb = Qrb, ...
On the other hand, if the sum total of the
requested flow rates is higher than the pump delivery
flow rate, the requested flow rates set bY the manually
operable levers 30A and 30B are multiPlied by [pump
delivery flow rate]/[sum total of requested flow rates]
= a, and values obtained by the multiplication are
outputted as actuator flow rate setting signals to the
valve controllers 32A, 32B, ... In other words, Qsa =
aQra, Qsb = aQrb~ .
Thus, since such a distributor 31a as described
above is provided, flow rate distribution or control of
the hydraulic pump 2 by complicated manual operations of
220 1 626
- 45 -
1 the manuallY operable levers 30A and 30B upon
simultaneous operation which are conventionally operated
manuallY and adjusted by an operator relying upon the
experience of the operator itself can be set to desired
manners of the operator based on contents of the works.
In other words, different priorities can be provided to
operations of the actuators 7A and 7B depending upon the
contents of the works.
Consequently, the manipulation system can
cooperate with the power supply system described above,
and an operator can automatical 1Y effect accurate flow
rate control irrespective of the loads 8A and 8B onlY by
manuallY operating the manually operable levers 30A and
30B while placing stress on grasping of a load condition
of the working machine.
Subsequently, the valve control sYstem will be
described. Also the valve control system is similar to
that described hereinabove in connection with the first
embodiment.
In particular, description is given taking
notice of the actuator (hYdraulic cylinder) 7A. First,
the actuator flow rate setting signal Qsa outputted from
the distributor 31a is inputted to the valve controller
32A. Meanwhile, a flow rate signal Qsaa to the actuator
7A is fed back by a flow rate sensor 106A. Then, a
signal (P control signal) obtained by multiplYing a
difference signal between the signal Qsa and the signal
~ 220~626
- 46 -
1 Qsaa by a constant Kp, another signal (I control signal)
obtained by multiplying an integrated value of the
difference signal between the slgnal Qsa and the signal
Qsaa by a constant l/T and a further signal F(Qsa) which
is a feedforward signal of the signal Qsa are added.
It is to be noted that the flow rate of the main
control valve 6A maY alternativelY be calculated from,
in place of the flow rate sensor 106A, a pressure
difference (Ps - Plla or Ps - P12a) across the main
control valve 6A, an output Xca of the spool position
sensor 107A of the main control vaive 6A or the like.
Further, also in the apparatus described in
connection with the present second embodiment, similarly
to that described hereinabove in connection with the
first embodiment, the valve control sYstem has a large
number of resonance and antiresonance points because the
mass loads 8A and 8B which vary over large extents are
driven, and particularly since a rocking phenomenon
having a low frequency deteriorates the driving feeling,
a signal Plla from the A port load pressure sensor 108A
of t~e maln control valve 6A and a signal P12a from the
B port load pressure sensor lO9A of the main control
valve 6A are fed back to the valve controller 32A via
the band-pass filters 200. In other words, the present
system is a dynamic pressure feedback sYstem.
Finally, the main control valve (3-stage
amplification type main control valve) 6A can feed back,
-
~ 2201626
- 47 -
1 since the signal Xca of the spool position (spool
opening) which increases in proportion to an input
current value Xci to the servo valve for the main
control valve is obtained from the spool position sensor
107A, this signal Xca to the valve controller 32A to
position the spool of the main control valve 6A so that
the signal Qsaa which is equal to the actuator flow rate
setting signals Qsa can be obtained automatically.
Thus, due to such a construction as described
above, flow rate distribution or control of the
hydraulic pump 2 by complicated manual operations of the
manuallY operable levers 30A and 30B upon simultaneous
operation which are conventionally operated manually and
adjusted by an operator relYing upon the experience of
the operator itself can be set to desired manners of the
operator based on contents of the works. In other
words, different priorities can be provided to
operations of the actuators 7A and 7B depending upon the
contents of the works.
Consequently, an operator can automatical 1Y
effect accurate flow rate control irrespective of the
loads 8A and 8B onlY bY manual 1Y operating the manually
operable levers 30A and 30B while placing stress on
grasping of a load condition of the working machine.
Subsequently, a modification to the second
embodiment of the present invention will be described.
The present modification is constructed in a
~ 2201 626
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1 substantiallY similar manner to that of the modification
to the first embodiment such that, in the second
embodiment described above, the actuator flow rate
setting signals Qsa and Qsb set by the distributor 31a
are set for each work mode of the construction machine
(for example, an excavation work mode, a house
demolition work mode and so forth).
In particular, in the second embodiment
described above, when the sum total of requested flow
rates to the hydraulic actuators 7A, 7B, ... by the
manually operable levers 30A, 30B, ... is higher than
the pump delivery flow rate, the coefficient a is
calculated by [pump delivery flow rate]/[sum total of
requested flow rates], and the requested flow rates set
bY the manual 1Y operable levers 30A, 30B, .. are
multiplied bY the coefficient a to set the actuator flow
rate setting signals as Qsa = aQra, Qsb = aQrb, ....
In this instance, the coefficient a by which the
requested flow rates Qra, Qrb, ... to the actuators 7A
and 7B is multiplied has a value equal for all of the
actuators 7A and 7B. In particular, all of Qra and Qrb
are multiplied uniformly bY the coefficient a.
BY the waY, since the requested flow rates Qra,
Qrb, ... are all set in response to manual 1Y operated
conditions of the manuallY operable levers 30A and 30B,
while different priorities are applied alreadY to
operations of the actuators 7A, 7B, ... depending upon
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1 the magnitudes of the set request signals Qra, Qrb, ....
if the coefficient a mentioned above is set individually
for each actuator, then the priorities of the actuators
can be made definite and the workability is improved.
In short, if, depending upon the mode of the work (that
is, the work mode), not the requested flow rates Qra,
Qrb, ... set in response to manually operated conditions
of the manual 1Y operable levers 30A and 30B are
corrected using the coefficient ~ of the same value, but
the actuator flow rate setting signals Qsa, Qsb, ... are
set using coefficients obtained by weighting the
requested flow rates Qra, Qrb, ... in accordance with
the mode of the work, then the operabilitY and the
workabilitY can be further improved.
Therefore, also in the present modification to
the second embodiment, the coefficient a by which the
requested flow rates Qra and Qrb are multiplied is
multiplied by correction coefficients kij which are set
for the individual actuators in response to the
actuators or the mode of the work (that is, the work
mode).
In particular, the distributor 31a also in this
instance has such a data table as shown in FIG. 4 set
therein, and in the data table, the correctlon
coefficients kii set depending upon the actuator number
i and the work mode number i are stored in the form of a
table.
~ 220 1 626
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1 The work mode is a work mode set arbitrarily by
an operator, and such modes as, for example, an
excavation mode for j = 1 and a house demolition mode
for i = Z are set. The operator can perform setting of
a work mode or changing of a set work mode bY manual 1Y
operating a manually operable member in an operator cab,
and priorities suitable for each work mode can be set
for the individual actuators (i = 1, 2, ...).
Meanwhile, i is a number indicating an actuator,
and where the construction machine is, for example, a
hydraulic shovel, i = 1 represents a boom cylinder, i =
2 rePresents a stick cylinder, i = 3 represents a bucket
cylinder, and i = 4 represents a swing motor.
If an operator selects, for example, the
excavation mode (i = 1) as a work mode, then correction
coefficients kll, k21, ... are set for the boom cylinder
(i = 1), the stick cYlinder (i = 2), ..., respectively.
For example, if an operator selects the
excavation mode (i = 1) as the work mode, then the
correction coefficients kll, k21, ... are set for the
boom cylinder (i = 1), the stick cylinder (i = 2), ...
Accordingly, when the sum total of the requested
flow rates to the hYdraulic actuators 7A, 7B, ... by the
manually operable levers 30A, 30B, ... is higher than
the pump delivery flow rate, the first coefficient a is
calculated bY [pump delivery flow rate]/[sum total of
reques~ted flow rates], and the coefficient a, the
220 1 626
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1 requested flow rates Qra, Qrb, ... set by the manually
operable levers 30A, 30B, ... and the correction
coefficients k~l, k2l, ... set for the individual
actuators are multiplied by each other to set the
actuator flow rate setting signals Qsa, Qsb, ... In
particular, the actuator flow rate setting signals are
set as Qsa = a kll Qra, Qsb = ~-kl 2 ~Qrb, ...
Then, bY setting the actuator flow rate setting
signals Qsa and Qsb to be set by the distributor 31a
using the correction coefficients kij set individuallY
for each work mode and each actuator of the construction
machine, a flow rate distribution to the actuators
suitable for the work mode of the construction machine
can be realized. Particularly upon simultaneous
operations of a plurality of actuators, operation on
which a will of an operator is reflected can be
realized.
Consequently, operation conforming to the will
of the operator can be performed without requiring anY
skill, and the workability is improved very much.
It is to be noted that, also in the second
embodiment and the modification to it, separate control
type valve means including the pluralitY of solenoid
valves 201 to 204 as shown, for example, in FIG. 5 maY
be emploYed in place of the main control valves 6A and
6B. Then, by such construction, supplY of working oil
to the actuator 207 and deliverY of working oil from the
- - ~
220 1 626
- 52 -
1 actuator Z07 can be controlled independentlY of each
other.
(3) Others
It is to be noted that the present invention is
not limited to the embodiments described above, and the
present invention can be embodied modifying it in
various forms without departing from the scope thereof.
INDUSTRIAL APPLICABILITY OF THE INVENTION
10 Where the present invention is applied to a
construction machine such as a hYdraulic excavation
machine or a hydraulic shovel, mutual interference
between different actuators caused by a variation in
pressure can be eliminated and lower harmonics of a
construction machine structure can be suppressed, and
improvement in operability and augmentation in driving
feeling of an operator can be anticipated. Further, by
an action of a distributor, an actuator flow rate
distribution requested by the operator can be realized
accurately irrespective of the loads to the actuators,
and improvement in operability, particularly, in
simultaneous operability and fine operability, can be
anticipated. AccordinglY, the pluralitY of actuators
can be driven at the same time in accordance with a will
of the operator, and the efficiency in working is
improved. Accordingly, the present invention can
contribute to improvement in operabilitY or workabilitY
220 1 626
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1 of the construction macnine, and it is believed that the
utilitY of the invention is very high.
