TECHNICAL FIELD
The invention relates to a device for controlling an
operational reaction force to be imparted to an operating
lever for actuating a working machine, e.g., a boom, of
machinery such as a crane.
BACKGROUND ART
In connection with the hoisting work by a crane, it is
known to use an operational reaction force control device for
imparting an operational reaction force to an operating lever
for actuating a winch of crane in order to improve operability
of the operating lever.
For example, Japanese Utility Model Publication No. 62-14077
discloses a control device for varying an operational
reaction force to a level proportional to the weight of a
lifted load.
And, Japanese Patent Publication No. 5-5755 improves
operability of a winch operating lever by generating an
operational reaction force in accordance with a manipulated
variable (a lifting speed) of the lever as well as the weight
of a lifted load and imparting the generated operational
reaction force to the lever.
Such existing related technologies are effective in the
hoisting work but if they are applied to turning work of the
crane or luffing work of the working machine (boom), they are
not necessarily effective.
Specifically, when a boom 21 of a crane 20 is luffed in
directions indicated by arrows A, B as shown in Fig. 5, the
operator cannot know an acceleration of the boom 21 to grasp a
possible motion of the boom 21. Therefore, it is hard to make
delicate control of the boom 21 through the operating lever,
and a lifted load 22 suffers from a vibrating relative motion
to swing in directions indicated by arrows C, D.
And, when an upper rotary body 23 is turned, the lifted
load 22 is also swung in the turning direction.
In view of above, it is necessary to impart an
operational reaction force to the operating lever to prevent
effectively the lifted load from being swung. But, the above-described
related art could not achieve it by imparting the
operational reaction force based on information such as the
weight of the lifted load or the manipulated variable of the
lever.
Besides, if prior art which imparts the operational
reaction force proportional to the weight of a lifted load is
applied to operate a working machine to handle a heavy load
for a long time or to operate a working machine at a high and
constant speed for a long time, a large operational reaction
force acts on the operating lever for a long time. As a
result, the operator is exhausted.
The invention was achieved in view of the above
circumstances and aims to provide an operational reaction
force control device which can be operated easily to prevent
effectively the swing of load and can relieve the operator
from getting fatigue.
DISCLOSURE OF THE INVENTION
The invention relates to an operational reaction force
control device for an operating lever of a working machine, in
which an operational reaction force is imparted to the
operating lever for actuating the working machine in a
direction opposite to an operating direction, characterized
by comprising acceleration detecting means for detecting an
acceleration of the working machine; and operational reaction
force imparting means for imparting the operational reaction
force, which increases as the acceleration detected by the
acceleration detecting means increases, to the operating
lever.
By configuring as described above, the operational
reaction force which increases as the acceleration detected by
the acceleration detecting means increases is imparted to the
operating lever.
Specifically, if the operating machine suffers from the
swing of load, namely the load 22 which is hung by the working
machine 21 is swung in the direction that the working machine
is moving (in the rotating direction of the working machine 23
when the working machine is turned, and direction C or D when
it is luffing) as shown in Fig. 5, the working machine 21 or
23 is required to be accelerated or decelerated to suppress
the swing of load.
Therefore, by varying the operational reaction force so
to increase as the acceleration of the working machine
increases, the accelerating or decelerating condition of the
working machine can be known based on the operational reaction
force. As a result, an operation of preventing the swing of
load by accelerating or decelerating the working machine
(controlling the relative motion of the load with respect to
the working machine) can be made with ease by referring to the
operational reaction force, and the swing of load can be
prevented effectively.
And, since a large operational reaction force does not
act on the operating lever at a constant speed excepting the
accelerating and decelerating states, a large operational
reaction force is not imparted to the operating lever for a
long time even when the working machine is operated against a
heavy load for a long time or the working machine is operated
at a high and constant speed for a long time, and the operator
can be relieved of fatigue remarkably.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram showing the structure of an
embodiment of the operational reaction force control device
for an operating lever of a working machine according to the
invention.
Fig. 2 is a control characteristic diagram showing the
relationship between an acceleration of the working machine
and an operational reaction force.
Fig. 3 is a diagram showing another embodiment of the
invention.
Fig. 4 is a diagram showing another embodiment of the
invention.
Fig. 5 is a side view of a truck crane applied to the
embodiments.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the operational reaction force control
device for an operating lever of a working machine according
to the invention will be described with reference to the
accompanying drawings.
As shown in Fig. 3, an embodiment will be described on
the assumption that an operational reaction force, which is
imparted to an operating lever for operating a boom 21 as
working machine of a crane 20, is controlled to raise or lower
the boom 21.
Fig. 1 is a diagram showing a structure of the device for
controlling an operational reaction force of an operating
lever 1 which is disposed in the operator cab of the crane 20
shown in Fig. 3.
Specifically, when the operating lever 1 is operated in
the direction indicated by an arrow (in the direction to raise
the boom 21), one of a piston 3 for lifting and a piston 4 for
lowering the working machine which are in a remote control
valve 2, namely the piston 3 corresponding to the direction
that the operating lever 1 is operated, is pushed down through
an operating plate 1a. When the operating lever 1 is operated
in the opposite direction (in the direction that the boom 21
is lowered), the piston 4 is pushed down in the same way.
Beneath these pistons 3, 4 are disposed a spool 5 for
raising the working machine and a spool 6 for lowering the
working machine. And, the spool 5 or 6 which corresponds to
the lowered piston is pushed down by a metering spring 7 or 8.
Since the piston 3 is pushed down in this case, the spool 5 is
moved downward.
As a result, a pump pressure chamber Pp which is
communicated with a discharge port of a hydraulic pump 15 is
repeatedly connected with or cut off from a drain chamber D
through a fine control hole f. And, a port pressure P1 or P2
of a pipeline 16 or 17 on the side of the pushed-down piston
is raised to a level corresponding to a force (proportional to
a stroke of the lever 1) for shrinking the metering spring 7
or 8, and they are balanced between the drain hole D and the
pump pressure chamber Pp.
Specifically, the port pressure P1 or P2 increases to a
level proportional to the stroke of the operating lever 1 and
acts with its magnitude on a pilot port 9a or 9b of a control
valve 9. More specifically, since the operating lever 1 is
operated in the direction to raise the boom, the port pressure
P1 proportional to the stroke of the lever 1 acts on the pilot
port 9a of the control valve 9. As a result, the control
valve 9 is actuated to drive a hydraulic cylinder for driving
the boom 21 at a speed corresponding to its valve opening,
thereby raising the boom 21. When the port pressure P2 is
exerted on the pilot port 9b of the control valve 9, the
control valve 9 is moved in the opposite direction, and the
boom 21 is lowered through the hydraulic cylinder.
To the root of a shaft 1b of the operating lever 1 is
connected a rotating shaft 10a of a motor 10, so that the
operating lever 1 is tilted to its operated direction or the
direction opposite to its operated direction according as the
motor 10 rotates.
The motor 10 has its rotation direction and rotation
torque varied according to an electrical command signal
(voltage) from a controller 11.
Pressure sensors 12, 13 are respectively disposed on the
pipelines 16, 17 in order to detect the pipeline inner
pressures P1, P2 as manipulated variable P1 of the lever to
raise the boom and as manipulated variable P2 of the lever to
lower the boom. And, detected pressures P1, P2 of the
pressure sensors 12, 13 as lever manipulated variable
detecting means are outputted to the controller 11.
An acceleration detector 14 is a detector for detecting
an acceleration of the boom 21 which is rising or lowering.
For example, it is comprised of a speed sensor (e.g., a rotary
encoder or a laser speed sensor is used) and a differentiation
circuit which differentiates output from the speed sensor and
outputs an acceleration α. A servo-type acceleration sensor
may be used as the acceleration detector 14. The acceleration
α detected by the acceleration detector 14 is outputted to the
controller 11.
The functions of the differentiation circuit may be
incorporated into the controller 11.
And, a potentiometer or the like which detects a
manipulated variable of the operating lever 1 as rotated
quantity may be used instead of the pressure sensors 12, 13 as
the lever manipulated variable detecting means.
The lever manipulated variable may also be detected as
speed of the boom 21, and where the acceleration detector 14
is comprised of the speed sensor and the differentiation
circuit as described above, a value detected by the speed
sensor can be used as it is as lever manipulated variable
detected value. And, it is not necessary to separately
dispose a lever manipulated variable detecting means, and the
cost as a whole can be reduced.
And, to detect the acceleration α of the boom 21, the
pressures P1, P2 may be determined as speed of the boom 21 and
differentiated.
Based on the boom acceleration α detected by the
acceleration detector 14 and the lever manipulated variables
P1, P2 detected by the pressure sensors 12, 13, the controller
11 determines an operational reaction force F (see Fig. 1) to
be imparted in the direction opposite to the operated
direction of the operating lever 1 as described afterward,
generates an electrical command signal corresponding to the
operational reaction force F, and outputs it to the motor 10.
Fig. 2 is a graph showing the control characteristics in
controlling a reaction force. The relationship among the boom
acceleration α, the lever manipulated values P1, P2 and the
lever operational reaction force F is indicated as control
characteristic L (L1-LM-L2). And, this relationship is stored
in a memory of the controller 11.
It is apparent from Fig. 2 that the control
characteristic L is determined so that the operational
reaction force F increases gradually as the acceleration α of
the boom 21 increases.
And, the control characteristics L1-LM-L2 are determined
so to increase gradually the operational reaction force F with
the control characteristics varied in the order of L1, LM and
L2 as the lever manipulated variables P1, P2 are increased.
More specifically, it is determined as follows:
- When the boom acceleration α is negative, the operational
reaction force F is set to a low value close to zero in order
to prevent the operational reaction force from being inverted
while the boom is decelerated (the speed direction of the boom
21 by operating the lever is opposite to the direction of
accelerating).
- In a range that the lever manipulated variable is small and
the lever 1 is often required to be operated delicately than
the swing of load is prevented, it is necessary to reduce the
operational reaction force F to make it easy to control the
boom 21 delicately. Accordingly, it is designed that the
control characteristics are varied in the order of L2, LM and
L1 sequentially so that the operational reaction force F
becomes smaller as the lever manipulated variable becomes
small.
- And, when the acceleration α of the boom 21 is extremely
high, it is necessary to make the operational reaction force F
high to prevent the boom 21 from moving suddenly due to an
error in operation. Therefore, the operational reaction force
F is varied nonlinearly so that the control characteristic L
has a higher inclination in a range in that the boom acceleration
α is high than in a range in which the boom acceleration is low.
When the present lever manipulated variables P1, P2
become equal to or below a predetermined first threshold, the
controller 11 selects the control characteristic L1. And,
when the lever manipulated variables P1, P2 become equal to or
higher than a second threshold which is determined to be
higher than the first threshold, the control characteristic L2
is selected. When the lever manipulated variables P1, P2
become higher than the first threshold but smaller than the
second threshold, the control characteristic LM is selected so
that the operational reaction force F increases as the
manipulated variable increases in the range L1-L2 as indicated
by the arrow.
Furthermore, the operational reaction force F
corresponding to the present boom acceleration α is determined
on the basis of the selected control characteristic L, and an
electrical command signal corresponding to the operational
reaction force F is generated and outputted to the motor 10.
Accordingly, the motor M is actuated, and the operational
reaction force F is imparted to the operating lever 1.
As a result, based on the operational reaction force F
imparted to the operating lever 1, the operator can know the
state of acceleration or deceleration of the boom 21 as the
working machine and can operate with ease to prevent the swing
of load by accelerating or decelerating the boom 21 with
reference to the operational reaction force F. Thus, the
swing of load can be prevented effectively.
And, at a constant speed excepting the accelerating and
decelerating states, a high operational reaction force F does
not act on the operating lever 1. Therefore, even when the
boom 21 is operated to move a heavy load for a long time or
operated at a high and constant speed for a long time, a high
operational reaction force F is not imparted to the operating
lever 1 for a long time, and the operator is relieved of
fatigue remarkably.
The control characteristic L shown in Fig. 2 is just an
example and can be set to various patterns according to the
working conditions.
For example, the control characteristic L is varied
according to the lever manipulated variable in the embodiment,
but the control characteristic L can be determined constant
(e.g., L1) regardless of the lever manipulated variable.
Fig. 3 and Fig. 4 show another embodiment of the
invention.
In this embodiment, the detector for detecting an
acceleration of the boom which is luffing is disposed at the
boom top end so that the operator can know the luffing motion
of the boom top end accurately. Since the acceleration sensor
is expensive, a sensor for detecting a boom angle or a boom
position is adopted as the detector for detecting the
acceleration of the boom in the luffing motion. And, the
value detected by such a sensor is second order differentiated
to calculate a boom acceleration.
Specifically, the crane operator can presume the position
of the boom top end in the lengthwise direction from a luffing
angle of the boom (see Fig. 3) and a length L of the boom.
However, the boom top end suffers from complicated motions
because the boom is warped, vibrated or moved by wind.
Therefore, when it is configured that the accelerometer
described above is mounted on a luffing cylinder 30 for
luffing the boom to measure a luffing acceleration of the boom
and a torque corresponding to the measured value is imparted
as the operational reaction force, the crane operator is hard
to know the motion of the crane top end accurately. And,
since the luffing cylinder 30 and the boom 21 are linked
mutually, the relationship between an extension speed of the
luffing cylinder 30 and a boom luffing angle speed does not
become linear. Therefore, the configuration that the
accelerometer is mounted on the luffing cylinder 30 is not
helpful for the crane operator in knowing the motion of the
boom top end.
In this embodiment, a boom angle detector 25 for
detecting a boom angle is mounted on the leading end of the
boom 21 as shown in Fig. 3.
As shown in Fig. 4, output from the angle detector 25 is
inputted in the controller 11.
The controller 11 calculates component cos in the
lengthwise direction (properly speaking, the lengthwise
direction of the boom 21 and not in the lengthwise direction
of the crane body) of the boom angle entered from the angle
detector 25. The calculated value cos is second order
differentiated to determine component -cos in the lengthwise
direction of the acceleration of the boom top end. And, based
on the component -cos thus obtained in the lengthwise
direction of the acceleration of the boom top end and the
lever manipulated variables P1, P2 detected by the pressure
sensors 12, 13, the controller 11 determines in the same way
as in the former embodiment the operational reaction force F
to be imparted in the direction opposite to the operated
direction of the operating lever 1 in view of the relationship
shown in Fig. 2, generates an electrical command signal
corresponding to the operational reaction force F, and outputs
it to the motor 10. Thus, the motor is actuated, and the
operational reaction force F proportional to the component -
cos in the lengthwise direction of the acceleration of the
boom top end is imparted to the operating lever 1.
Thus, in this embodiment, a torque proportional to the
acceleration in the lengthwise direction of the boom top end
is imparted as a reaction force to the luffing operating
lever. Therefore, the crane operator can feel the motion
(acceleration) in the lengthwise direction of the boom top end
while operating the luffing operating lever and can also
presume the motion (position and speed) of the boom top end.
And, when a hung load is moved, the boom can be operated so
that the hung load is hardly swung. At the time of luffing
the boom, the boom top end is desirably positioned just above
the hung load to stop a swing motion of the hung load, and
this embodiment is also effective to do so. Besides, this
embodiment has an inexpensive boom angle sensor as the sensor
for detecting the acceleration of the boom top end, and output
from the sensor is second order differentiated to calculate
the acceleration of the boom top end, so that the device cost
can also be reduced.
The acceleration in the lengthwise direction of the boom
top end was determined in the above embodiment, but the
acceleration in the vertical direction of the boom top end may
be determined to impart as the operational reaction force a
force proportional to the obtained acceleration to the luffing
lever.
And, the boom angle sensor for detecting the boom angle
of the boom top end was used in the above embodiment, but a
position sensor may be disposed to determine the position of
the boom top end, and the output from the position sensor
second order differentiated to determine the acceleration of
the boom top end.
The boom of a crane was assumed as the working machine in
the above embodiments, but any working machines which are
actuated to prevent the swing of load can be applied to a
desired working machine.
INDUSTRIAL APPLICABILITY
As described above, the invention can easily make an
operation to effectively prevent the swing of load. And, the
operator operating the lever can be relieved of fatigue
remarkably.