Information
-
Patent Grant
-
6230090
-
Patent Number
6,230,090
-
Date Filed
Thursday, September 3, 199826 years ago
-
Date Issued
Tuesday, May 8, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Cuchlinski, Jr.; William A.
- Pipala; Edward
Agents
- Mattingly, Stanger & Malur
-
CPC
-
US Classifications
Field of Search
US
- 701 1
- 701 50
- 701 300
- 037 414
- 037 348
- 091 361
- 091 392
- 091 418
- 091 419
- 091 448
- 091 458
- 091 459
- 700 178
- 212 276
- 212 280
-
International Classifications
-
Abstract
When an arm end exceeds a boundary line K2 and enters a slowdown area R1, a proportional solenoid pressure reducing valve 13 is operated to reduce a pilot pressure for slowing down a first boom cylinder 1A, thereby slowing down an arm end speed. When the arm end exceeds a boundary line K1 and enters a restoration area R2, a restoration gain is calculated in control gain block 200 depending on an intrusion amount by which the arm end enters the restoration area, while a feedback gain is calculated depending on an arm end speed at that time on the basis of functions 204, 205, 206, 207, 208 and 209. In accordance with these gains, a second boom 2 is automatically dumped depending on the intrusion amount of the arm end into the restoration area and the arm end speed at that time so that the arm end is moved for return to the slowdown area. As a result, such work as requiring a work front to be moved toward the operator is continuously smoothly performed and working efficiency is improved.
Description
TECHNICAL FIELD
The present invention relates to an interference prevention system for a 2-piece boom type hydraulic excavator, and more particularly to an interference prevention system for a 2-piece boom type hydraulic excavator, which operates to restrict movement of a work front when a predetermined position of the work front comes close to an excavator body.
1. Background Art
A work front of a hydraulic excavator is made up of front members such as a boom and an arm, which are vertically movable, with a working appliance, e.g., a bucket, attached to a fore end of the arm. The boom of the work front is bent at a certain angle and is usually constituted by a single mono-boom. In some hydraulic excavators, a boom is divided into two parts, i.e., a first boom and a second boom. These hydraulic excavators are called 2-piece boom type hydraulic excavators.
In a 2-piece boom type hydraulic excavator, when manipulating the front members, such as the first boom, the second boom and the arm, through respective control levers, the operator can freely change an angle formed between the first boom and the second boom; hence there is a risk that the bucket may interfere with the excavator body, in particular an operating room (cab), depending on the angle formed between the first boom and the second boom. For that reason, an interference prevention system for preventing such interference is proposed in JP, A, 2-308018.
In the interference prevention system proposed in JP, A, 2-308018, potentiometers are provided at pivotally articulated portions of the first boom, the second boom and the arm to detect relative angles of the respective articulations, and an arm end position is calculated based on outputs from the potentiometers. When the calculated arm end position enters a preset danger area, a signal is output to actuate an alarm device. Also, when the calculated arm end position enters the preset danger area, an interference prevention controller outputs a signal to shift a switching valve, which is installed between an actuator for operating each front member and a control valve, to an off-position, thereby automatically stopping movement of the front member under operation.
2. Disclosure of the Invention
In the related art disclosed in JP, A, 2-308018, as described above, when the arm end enters the danger area, the movement of the front members is restricted so as to stop. Such control of stopping the front members is however disadvantageous in that when the operator performs work near the cab, it is difficult to continuously smoothly carry out the work that requires the work front to be moved in a direction toward the operator (cab), e.g., excavating and earth-releasing, thus resulting in a remarkable reduction in working efficiency.
An object of the present invention is to provide an interference prevention system for a 2-piece boom type hydraulic excavator with which such work as requiring a work front to be moved in a direction toward the operator is continuously smoothly performed and working efficiency is improved.
(1) To achieve the above object, the present invention provides an interference prevention system for a 2-piece boom type hydraulic excavator, the interference prevention system being installed in a 2-piece boom type hydraulic excavator comprising an excavator body, a work front mounted on the excavator body and having a plurality of front members including first and second booms and an arm which are vertically rotatable, a first boom cylinder for driving the first boom, a second boom cylinder for driving the second boom, an arm cylinder for driving the arm, a first-boom flow control valve for controlling a flow rate of a hydraulic fluid supplied to the first boom cylinder in accordance with an operation signal from first-boom operating means, a second-boom flow control valve for controlling a flow rate of a hydraulic fluid supplied to the second boom cylinder in accordance with an operation signal from second-boom operating means, and an arm flow control valve for controlling a flow rate of a hydraulic fluid supplied to the arm cylinder in accordance with an operation signal from arm operating means, the interference prevention system serving to restrict movement of the work front when a predetermined position of the work front comes close to the excavator body, wherein the interference prevention system comprises attitude detecting means for detecting an attitude of the work front, and control means for receiving detection signals from the attitude detecting means and, when the predetermined position of the work front comes close to the excavator body, outputting a command signal to the second-boom flow control valve so that the second boom is moved in a dumping direction.
With the present invention thus constructed, since the second boom is moved in the dumping direction when the predetermined position of the work front comes close to the excavator body, the work front is prevented from interfering with the excavator body or a cab without being stopped, and such work as requiring the work front to be moved toward the operator (cab) can be continuously, smoothly performed.
Also, since the above-mentioned control is made by moving the second boom in the dumping direction, which is less frequently employed in actual work, rather than the arm, the interference avoidance control can be achieved allowing the operator to feel less awkward during the operation.
(2) In the above (1), preferably, when the first boom is operated in a rising direction by the operating means for the first boom, the control means makes control to move the second boom in the dumping direction while continuing to raise the first boom.
With this feature, when the predetermined position of the work front comes close to the excavator body, the predetermined position of the work front is controlled to move while going around the excavator body (cab) with a combination of the first-boom raising operation and the second-boom dumping operation. As a result, such work as requiring the work front to be moved toward the operator (cab) can be continuously smoothly performed while avoiding interference between the work front and the excavator body.
(3) In the above (2), preferably, the control means receives an operation signal in the first-boom raising direction output from the operating means for the first boom, and modifies the operation signal in the first-boom raising direction such that first-boom raising operation is slowed down as the predetermined position of the work front comes closer to the excavator body, and thereafter the first-boom raising operation is continued at a slowed-down speed.
With this feature, since the first-boom raising operation is slowed down when the predetermined position of the work front comes close to the excavator body, the second boom cylinder can be supplied with the hydraulic fluid at a sufficient flow rate even when there is a limit in maximum capacity of a hydraulic pump. Accordingly, the second boom can be quickly dumped and the work front is surely prevented from interfering with the excavator body.
Also, since the first-boom raising operation is slowed down, a distance left between the predetermined position of the work front and the excavator body when the former comes close to the latter is suppressed, and therefore interference between the work front and the excavator body is surely prevented with the dumping of the second boom.
(4) In the above (2), preferably, the control means receives an operation signal in a second-boom crowding direction output from the operating means for the second boom and an operation signal in an arm crowding direction output from the operating means for the arm, and modifies the operation signal in the second-boom crowding direction and the operation signal in the arm crowding direction such that when the first boom is not moved in the rising direction, the work front is slowed down as the predetermined position of the work front comes closer to the excavator body and thereafter the work front is stopped.
With this feature, in work carried out by not operating the first boom in the rising direction, but operating the second boom and/or the arm in the crowding direction, the work front is controlled to just slow down and stop when the predetermined position of the work front comes close to the excavator body. Hence the work front is avoided from moving in a direction away from the excavator body due to the dumping of the second boom.
Here, in work carried out by operating the second boom and/or the arm in the crowding direction without raising the first boom, the operator intends to carry out the operation only requiring the work front to be moved toward the operator (cab) in many cases. In such work, if the work front is moved in a direction away from the excavator body by dumping the second boom, the movement of the work front would be unexpected one for the operator, and if there is an object such as a wall in the dumping direction, the work front may hit against the object. By slowing down and stopping the work front as mentioned above, the movement unexpected for the operator is avoided and good operability is ensured.
(5) In the above (2), preferably, the control means receives an operation signal in an arm crowding direction output from the operating means for the arm, and modifies the operation signal in the arm crowding direction such that when the first boom is moved in the rising direction, an arm crowding operation is slowed down as the predetermined position of the work front comes closer to the excavator body, and thereafter the arm crowding operation is continued at a slowed-down speed.
With this feature, when the predetermined position of the work front comes close to the excavator body under the first-boom raising operation and the arm crowding operation, the arm crowding operation is allowed to continue at a certain speed after being slowed down. As a result, the arm crowding operation is avoided from repeating the stop and slowdown in the restoration control with the dumping of the second boom, and smooth interference avoidance control can be achieved.
(6) In the above (1) or (2), preferably, the control means calculates a target speed of the second boom in the dumping direction corresponding to a moving speed of the predetermined position of the work front, and makes the control so that the second boom is moved at the calculated target speed.
With this feature, when the second boom is controlled so as to dump, a dumping speed of the second boom in match with the moving speed of the predetermined position of the work front is obtained and smooth interference avoidance control is achieved.
(7) In the above (6), preferably, the control means calculates the target speed of the second boom in the dumping direction to provide a higher target speed value as a moving speed of the predetermined position of the work front increases.
(8) In the above (1) or (2), preferably, the control means calculates a target speed of the second boom in the dumping direction that increases as the predetermined position of the work front comes closer to the excavator body, and makes the control so that the second boom is moved at the calculated target speed.
With these features, the dumping speed of the second boom is increased as the predetermined position of the work front comes closer to the excavator body, and interference between the work front and the excavator body can be surely prevented.
(9) In the above (1) or (2), preferably, the attitude detecting means includes means for calculating a distance from the predetermined position of the work front to an area previously set around the excavator body, and the control means modifies the operation signals from the operating means such that when the calculated distance is not larger than a preset first control start distance, the work front is gradually slowed down as the calculated distance becomes smaller, modifies the operation signals from the operating means such that when the calculated distance reaches a preset second control start distance smaller than the first control start distance, the front members are stopped except at least operation of raising the first boom, and makes control such that when the calculated distance is not larger than the second control start distance, the second boom is moved in the dumping direction.
With this feature, when the predetermined position of the work front comes close to the excavator body, the work front is first controlled at the calculated distance being not larger than the first control start distance such that the front members are slowed down and then stopped except at least operation of raising the first boom. After that, at the calculated distance being not larger than the second control start distance, the second boom is controlled to move in the dumping direction. The second boom cylinder can be therefore supplied with the hydraulic fluid at a sufficient flow rate even when there is a limit in maximum capacity of a hydraulic pump. Accordingly, the second boom can be quickly dumped and the work front is surely prevented from interfering with the excavator body.
Also, since the front members are slowed down before starting to control the second boom to dump, an intrusion amount by which the predetermined position of the work front enters beyond the second control start distance is suppressed, and interference between the work front and the excavator body can be surely prevented.
(10) In the above (9), preferably, the control means modifies the operation signals from the operating means such that when the calculated distance reaches the preset second control start distance smaller than the first control start distance, the front members are stopped except operations of raising the first boom and crowding the arm.
With this feature, when the predetermined position of the work front comes close to the excavator body under the first-boom raising operation and the arm crowding operation to such an extent that the calculated distance is not larger than the second control start distance, the arm crowding operation is allowed to continue at a certain speed. As a result, the arm crowding operation is avoided from repeating the stop and slowdown in the restoration control with the dumping of the second boom, and smooth interference avoidance control can be achieved.
(11) In the above (9), preferably, the control means receives the operation signals from the operating means and modifies the operation signals from the operating means such that a degree of slowdown is reduced with an increase in stroke amounts by which the operating means are operated.
With this feature, the slowdown control can be always started upon reaching near the first control start distance regardless of the stroke amounts of the operating means, and smooth interference avoidance control can be achieved.
(12) In the above (1) or (2), preferably, when the predetermined position of the work front comes close to the excavator body, the control means outputs command signals to the second-boom flow control valve and the arm flow control valve so that the second boom and the arm are both moved in the dumping direction.
With this feature, quick interference avoidance control can be achieved with good response.
(13) In the above (1) or (2), preferably, when the predetermined position of the work front comes close to the excavator body, the control means may output a command signal to the arm flow control valve so that the arm is moved in the dumping direction instead of the second boom.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic view showing an interference prevention system for a 2-piece boom type hydraulic excavator according to a first embodiment of the present invention.
FIG. 2
is a flowchart for explaining an interference prevention control process according to the first embodiment of the present invention.
FIG. 3
is a view showing dimensions, angles and a coordinate system of a work front.
FIG. 4
is a functional block diagram showing a control algorithm of a controller.
FIG. 5
is a view for explaining a manner of calculating a distance deviation ΔZ from the position of an arm end to the boundary line of a restoration area.
FIG. 6
is a functional block diagram showing details of slowdown control.
FIGS. 7
a
,
7
b
and
7
c
show a set of graphs each showing the relationship between the deviation ΔZ and a slowdown gain set in a control gain block in enlarged scale.
FIGS. 8
a
,
8
b
and
8
c
show a set of graphs each showing how the setting relationship between the deviation ΔZ and the slowdown gain changes depending on a pilot pressure.
FIG. 9
is a functional block diagram showing details of restoration control.
FIGS. 10
a
and
10
b
show a set of graphs showing, in enlarged scale, the relationship between the deviation ΔZ and a restoration gain set in the control gain block and the relationship between a second boom cylinder target speed and a feedback gain set in a feedback gain block.
FIG. 11
is a view for explaining how to determine an arm end target speed.
FIG. 12
is a schematic view showing an interference prevention system for a 2-piece boom type hydraulic excavator according to a second embodiment of the present invention.
FIG. 13
is a functional block diagram showing details of restoration control.
FIG. 14
is a schematic view showing an interference prevention system for a 2-piece boom type hydraulic excavator according to a third embodiment of the present invention.
FIG. 15
is a functional block diagram showing a control algorithm of a controller.
FIG. 16
is a schematic view showing an interference prevention system for a 2-piece boom type hydraulic excavator according to a fourth embodiment of the present invention.
FIG. 17
is a functional block diagram showing details of slowdown control.
FIG. 18
is a functional block diagram showing details of restoration control.
BEST MODE FOR CARRYING OUT THE INVENTION
Several embodiments of the present invention will be described hereunder with reference to the drawings.
To begin with, a first embodiment of the present invention will be described with reference to
FIGS. 1-11
.
In
FIG. 1
, a 2-piece boom type hydraulic excavator
40
, to which the present invention is applied, has an excavator body
41
and a multi-articulated work front
42
. The excavator body
41
comprises a lower track structure
41
A, an upper revolving structure
41
B rotatably mounted on the lower track structure
41
A, and a cab
41
C provided on the upper revolving structure
41
B. The work front
42
comprises a first boom
1
vertically rotatable attached to a front portion of the upper revolving structure
41
B, a second boom
2
vertically rotatably attached to the first boom
1
, an arm
3
vertically rotatably attached to the second boom
2
, and a working appliance, e.g., a bucket
4
, vertically rotatably attached to the arm
3
.
The first boom
1
, the second boom
2
, the arm
3
and the bucket
4
are driven respectively by a first boom cylinder
1
A, a second boom cylinder
2
A, an arm cylinder
3
A and a bucket cylinder
4
A.
A hydraulic drive circuit of the hydraulic excavator
40
is shown in a lower half of FIG.
1
. The hydraulic drive circuit includes the first boom cylinder
1
A, the second boom cylinder
2
A and the arm cylinder
3
A mentioned above; hydraulic pumps
29
and
30
provided with respective displacement varying mechanisms
29
A and
30
A; a first boom flow control valve
10
and a second boom flow control valve
11
for controlling respective flow rates of a hydraulic fluid supplied from the hydraulic pump
29
to the first boom cylinder
1
A and the second boom cylinder
2
A; an arm flow control valve
12
for controlling a flow rate of a hydraulic fluid supplied from the hydraulic pump
30
to the arm cylinder
3
A; pilot valves
19
,
20
for outputting pilot pressures as operation signals to the first boom flow control valve
10
; pilot valves
21
,
22
for outputting pilot pressures as operation signals to the second boom flow control valve
11
; and pilot valves
23
,
24
for outputting pilot pressures as operation signals to the arm flow control valve
12
. The pilot valves
19
,
20
are selectively operated depending on the direction in which a common control lever is operated, and output, as command signals, pilot pressures depending on an input amount by which the control lever is operated. Also, each pair of pilot valves
21
,
22
and pilot valves
23
,
24
are selectively operated depending on the direction in which a common control lever is operated, and output, as command signals, pilot pressures depending on a stroke amount by which the control lever is operated. The flow control valves
10
,
11
,
12
are each controlled by the pilot pressure output from the pilot valve so as to have an opening area that corresponds to the stroke amount of the control lever (pilot pressure). The flow rate and supply direction of the hydraulic fluid are thus controlled.
In
FIG. 1
, the hydraulic drive circuit shows only sections related to the first boom cylinder
1
A, the second boom cylinder
2
A and the arm cylinder
3
A, while other sections related to the bucket cylinder
4
A and actuators for swing and traveling are omitted.
An interference prevention system of the present invention is installed in the 2-piece boom type hydraulic excavator described above. The interference prevention system comprises a first boom angle sensor
5
provided in a joint portion between the upper revolving structure
41
B and the first boom
1
for detecting a relative angle formed between the upper revolving structure
41
B and the first boom
1
, a second boom angle sensor
6
provided in a joint portion between the first boom
1
and the second boom
2
for detecting a relative angle formed between the first boom
1
and the second boom
2
, an arm angle sensor
7
provided in a joint portion between the second boom
2
and the arm
3
for detecting a relative angle formed between the second boom
2
and the arm
3
, pressure sensors
25
,
26
for detecting the respective pilot pressures output from the pilot valves
19
,
20
, a pressure sensor
27
for detecting the pilot pressure output from the pilot valve
21
, a pressure sensor
28
for detecting the pilot pressure output from the pilot valve
23
, proportional solenoid pressure reducing valves
13
,
14
for reducing the respective pilot pressures output from the pilot valves
19
,
20
, a proportional solenoid pressure reducing valve
16
for reducing the pilot pressure output from the pilot valve
21
, a proportional solenoid pressure reducing valve
17
for reducing a pilot pressure supplied from a pilot hydraulic source
32
, a proportional solenoid pressure reducing valve
18
for reducing the pilot pressure output from the pilot valve
23
, a shuttle valve
33
for selecting higher one of the pilot pressure output from the pilot valve
22
and the pilot pressure output from the proportional solenoid pressure reducing valve
17
and applying the selected pilot pressure to the flow control valve
11
, and a controller
50
made up of an input/output unit
50
a,
a CPU
50
b
and a memory
50
c.
The controller
50
receives signals from the angle sensors
5
,
6
,
7
and the pressure sensors
25
,
26
,
27
,
28
, and outputs control signals for controlling the work front
42
to the proportional solenoid pressure reducing valves
13
,
14
,
16
,
17
,
18
based on the received angle signals and pressure signals.
Denoted by
31
is a reservoir.
An interference prevention control process of this embodiment will be described below.
In this embodiment, as shown in
FIG. 1
, a slowdown area R
1
and a restoration area R
2
are set. Slowdown control is performed in the slowdown area R
1
and restoration control is performed in the restoration area R
2
.
Here, K
1
indicates a boundary line representing the boundary between the slowdown area R
1
and the restoration area R
2
, and K
2
indicates a boundary line representing the boundary between the slowdown area R
1
and an area where control is not performed, i.e., slowdown start line. The boundary line K
2
is set a predetermined distance rO spaced from the boundary line K
1
.
FIG. 2
is a flowchart showing an outline of the interference prevention control process.
First, an arm end position is calculated based on the signals from the angle sensors
5
,
6
,
7
(step
11
). The arm end position is calculated as values on an XY-coordinate system with a base end of the first boom
1
defined as the origin, as shown in
FIG. 3. A
calculation formula is given by the following formula (
1
):
X=L
1
cos θ
1
+
L
2
cos(θ
1
+θ
2
)+
L
3
cos(θ
1
+θ
2
+θ
3
)
Y=L
1
sin θ
1
+
L
2
sin(θ
1
+θ
2
)+
L
3
sin(θ
1
+θ
2
+θ
3
) (1)
L
1
: length of the first boom
1
L
2
: length of the second boom
2
L
3
: length of the arm
3
θ
1
: angle detected by the first boom angle sensor
5
θ
2
: angle detected by the second boom angle sensor
6
θ
3
: angle detected by the arm angle sensor
7
Then, it is determined whether or not the first boom is under raising operation (step
12
). If YES, it is determined whether or not the arm end position has exceeded the boundary line K
2
and entered the slowdown area R
1
(step
13
). If NO, it is also determined whether or not the arm end position has exceeded the boundary line K
2
and entered the slowdown area R
1
(step
17
). If the arm end position has not yet exceeded the boundary line K
2
and entered the slowdown area R
1
, the process flow returns to the start without carrying out any control (step
19
).
If the arm end position has exceeded the boundary line K
2
and entered the slowdown area R
1
on condition that the first boom is under raising operation, slowdown control is performed such that the proportional solenoid pressure reducing valves
13
,
14
,
16
,
18
are operated to reduce the respective pilot pressures to slow down and then stop the actuators for slowing down the cylinders
1
A,
2
A,
3
A of the first boom
1
, the second boom
2
and the arm
3
, thus causing the arm end to stop at the boundary line K
1
(steps
12
,
17
and
18
). Details of the slowdown control will be described later.
If the arm end position has exceeded the boundary line K
2
and entered the slowdown area R
1
on condition that the first boom is not under raising operation, slowdown control is performed such that the proportional solenoid pressure reducing valves
13
,
14
,
16
,
18
are operated to reduce the respective pilot pressures for slowing down the cylinders
1
A,
2
A,
3
A of the first boom
1
, the second boom
2
and the arm
3
, whereby the arm end position is slowed down in the slowdown area R
1
and the arm end speed is reduced to a predetermined speed (steps
12
,
13
and
14
).
Next, it is determined whether or not the arm end position has exceeded the boundary line K
1
and entered the restoration area R
2
(step
15
). If the arm end has not exceeded the boundary line K
1
and entered the restoration area R
2
, the process flow returns to the start (step
19
).
If the arm end has exceeded the boundary line K
1
and entered the restoration area R
2
, restoration control is performed such that the proportional solenoid pressure reducing valve
17
is operated to reduce the pilot pressure to make control for automatically dumping the second boom
2
, thus causing the arm end position to move back into the slowdown area R
1
outside the boundary line K
1
. As a result of this operation, the predetermined position of the work front
42
, e.g., the bucket
4
, is avoided from interfering with the cab
41
C. Details of the restoration control will be described later.
The above processing is executed in the controller
50
. A control algorithm of the controller
50
will be described below with reference to
FIGS. 4-11
.
First, the overall control algorithm of the controller
50
will be described with reference to FIG.
4
.
In
FIG. 4
, the controller receives the signals from the angle sensors
5
,
6
,
7
and calculates the arm end position based on the detected angles θ
1
, θ
2
, θ
3
in a block B
9
. Then, it calculates a deviation ΔZ given by the shortest distance from the arm end position, i.e., (X, Y), to the boundary line K
1
in a block B
10
. Details of this calculation is shown in FIG.
5
. The deviation ΔZ is calculated as a positive value when the arm end is in the slowdown area R
1
or in the area where the control is not performed, and as a negative value when it is in the restoration area R
2
.
Next, the deviation ΔZ calculated in the block B
10
is input to blocks B
11
, B
12
and B
13
.
In the block B
11
, the signals from the pressure sensors
25
,
26
,
27
,
28
are further received, and command voltages for the proportional solenoid valves
13
,
14
,
16
,
18
are calculated from pilot pressures P
fbu
, P
fbd
, P
sbc
, P
ac
and the deviation ΔZ in accordance with the control algorithm for the slowdown control.
In the block B
12
, a command voltage for the proportional solenoid valve
17
is calculated from the arm end position (X, Y), calculated in the block B
9
, and the deviation ΔZ in accordance with the control algorithm for the restoration control.
In the block B
13
, the controller outputs a 0-level signal when the deviation ΔZ is positive, and a 1-level signal when it is negative. Further, in a block B
14
, the controller receives the signal from the pressure sensor
25
, and outputs a 1-level signal when the first-boom raising pilot pressure P
fbu
is input, and a 0-level signal when it is not input.
In a block B
15
, minimum one of both output signals from the blocks B
13
, B
14
is selected (MIN-selection), and the selected signal is multiplied in a block B
16
by the command voltage for the proportional solenoid valve
17
output from the block B
12
for the restoration control so that the restoration control of the block B
12
is performed only when the output signals from the blocks B
13
, B
14
are both 1-level signals.
Details of the slowdown control of the block B
11
is shown in a functional block diagram of FIG.
6
.
First, control of the proportional solenoid pressure reducing valve
13
for raising the first boom will be described. A control gain block
101
calculates a slowdown gain K
fbu
from the deviation ΔZ. A first-boom raising metering characteristic block
100
calculates a cylinder target speed M
fbu
from the first-boom raising pilot pressure P
fbu
. A block
117
multiplies the slowdown gain K
fbu
by the cylinder target speed M
fbu
. A target pilot pressure P
fbun
is calculated from a resulting value by referring to a metering table
102
, and the calculated pilot pressure is converted, by referring to a voltage table
103
, into an output voltage for the proportional solenoid pressure reducing valve
13
for raising the first boom, followed by being output to the valve
13
.
The relationship between the deviation ΔZ and the slowdown gain K
fbu
set in the control gain block
101
is shown in FIG.
7
(
a
) in enlarged scale. The relationship between the deviation ΔZ and the slowdown gain K
fbu
is set as follows. When the deviation ΔZ is larger than the slowdown start distance r
0
, the slowdown gain K
fbu
is 1. When the deviation ΔZ is not larger than the slowdown start distance r
0
, the slowdown gain K
fbu
is gradually reduced as the deviation ΔZ reduces. When the deviation ΔZ becomes 0, the slowdown gain K
fbu
has a certain value larger than 0. When the deviation ΔZ is given by a negative value, the slowdown gain K
fbu
is kept at the value taken when the deviation ΔZ is 0. With the above setting relationship, the slowdown gain K
fbu
in the restoration area R
2
is given by a value larger than 0, enabling the first boom
1
to be moved in the restoration area R
2
.
The relationship between the first-boom raising pilot pressure P
fbu
and the cylinder target speed M
fbu
set in the first-boom raising metering characteristic block
100
is determined depending on an opening area characteristic of the flow control valve
10
in the direction to raise the first boom. The slowdown gain K
fbu
multiplied by the cylinder target speed M
fbu
in the block
117
is modified, as shown in FIG.
8
(
a
), into a slowdown gain K
fbu*
which increases as the first-boom raising pilot pressure P
fbu
becomes higher. As a result, the slowdown control can be performed depending on an operating speed at which the first boom is raised.
In other words, when the deviation ΔZ becomes not larger than the slowdown start distance r
0
, the slowdown control is started in accordance with the characteristic of FIG.
7
(
a
) regardless of the level of the first-boom raising pilot pressure P
fbu
, and smooth slowdown control is always ensured.
A characteristic of the metering table
102
is a reversal of the first-boom raising metering characteristic of the block
100
.
The proportional solenoid pressure reducing valve
14
for lowering the first boom and the proportional solenoid pressure reducing valve
16
for crowding the second boom are also controlled, similarly to the proportional solenoid pressure reducing valve
13
for raising the first boom, with a set of a control gain block
105
, a first-boom lowering metering characteristic block
104
, a multiplying block
118
, a metering table
106
and a voltage table
107
, and a set of a control gain block
109
, a second-boom crowding metering characteristic block
108
, a multiplying block
119
, a metering table
110
and a voltage table
111
, respectively.
In the control gain blocks
105
,
109
, however, the relationship between the deviation ΔZ and the slowdown gain is set such that the slowdown gains K
fbd
, K
sbc
are both reduced to zero when the deviation ΔZ becomes not larger than 0, as shown in FIG.
7
(
b
) in enlarged scale. The operations of lowering the first boom and crowding the second boom are thereby stopped at the boundary line K
1
.
Further, the slowdown gain K
fbd
multiplied by the cylinder target speed M
fbd
in the block
118
, for example, is modified, as shown in FIG.
8
(
b
), into a slowdown gain K
fbd*
which increases as the first-boom lowering pilot pressure P
fbd
becomes higher. Accordingly, as with the case of FIG.
8
(
a
), the slowdown control can be performed depending on an operating speed at which the first boom is lowered.
Next, control of the proportional solenoid pressure reducing valve
18
for crowding the arm will be described. A control gain block
113
calculates a slowdown gain K
ac
from the deviation ΔZ. A first-boom raising pilot pressure gain block
116
calculates a gain K
fbu
from the first-boom raising pilot pressure P
fbu
. Also, an arm crowding metering characteristic block
112
calculates a cylinder target speed M
ac
from the arm crowding pilot pressure P
ac
.
The relationship set in the control gain block
113
is substantially the same as set in the control gain block
105
.
The relationship between the first-boom raising pilot pressure P
fbu
and the gain K
fbu
set in the first-boom raising pilot pressure control gain block
116
is shown in FIG.
7
(
c
) in enlarged scale. The relationship between the first-boom raising pilot pressure P
fbu
and the gain K
fbu
is set as follows. When the pilot pressure P
fbu
is at maximum, the gain K
fbu
is 0. As the pilot pressure P
fbu
lowers, the gain K
fbu
is gradually increased. Then, when the pilot pressure P
fbu
lowers down to near 0, the gain K
fbu
becomes 1.
The three gains obtained in the blocks
112
,
113
,
116
are processed by being multiplied in blocks
120
-
123
to determine a modified slowdown gain K
ac*
in accordance with the following formula:
K
ac*
=(1
−K
fbu
+K
ac
×K
fbu
)×
M
ac
(2)
With such processing, as shown in FIG.
8
(
c
), the modified slowdown gain K
ac*
is set to increase as the first-boom raising pilot pressure P
fbu
becomes higher, thereby suppressing a slowdown amount so that the arm end enters the restoration area R
2
while maintaining a certain arm crowding speed corresponding to the first-boom raising speed at the time when the arm end exceeds the boundary line K
1
. Also, similarly to the operation of raising the first boom, for example, the modified slowdown gain K
ac*
is increased as the arm crowding pilot pressure P
ac
becomes higher, thus enabling the slowdown control to be performed depending on an operating speed of the arm
3
.
Then, a target pilot pressure P
acn
is calculated from the modified slowdown gain K
ac*
by referring to a metering table
114
, and the calculated pilot pressure is converted, by referring to a voltage table
115
, into an output voltage for the proportional solenoid pressure reducing valve
18
for crowding the arm, followed by being output to the valve
18
.
Details of the restoration control of the block B
12
is shown in a functional block diagram of FIG.
9
.
A control gain block
200
calculates a restoration gain K
sbdd
from the deviation ΔZ. Also, a block
204
calculates respective front angular speeds (θ′
1
, θ′
2
, θ′
3
) (where′ represents differentiation) of the first boom
1
, the second boom
2
and the arm
3
from the coordinate values (X, Y) of the arm end position calculated in the block B
9
of FIG.
4
. Then, a block
205
determines an arm end speed (X′, Y′) from the front angular speeds (θ′
1
, θ′
2
, θ′
3
), and a block
206
calculates an arm end target speed (X′
n
, Y′
n
) from the arm end speed (X′, Y′). Subsequently, a block
207
calculates a second-boom target angular speed θ′
2n
from the arm end target speed (X′
n
, Y′
n
), and a block
208
determines a second-boom cylinder target speed S
2n
from the second-boom target angular speed θ′
2n
. Further, a feedback gain block
209
determines a feedback gain K
sbf
from the second-boom cylinder target speed S
2n
.
The restoration gain K
sbdd
and the feedback gain K
sbf
thus obtained are added to each other in an adder
203
. A target pilot pressure P
sbdn
is calculated from a resulting gain K
sbd
by referring to a metering table
201
, and the calculated pilot pressure is converted, by referring to a voltage table
202
, into an output voltage for the proportional solenoid pressure reducing valve
17
for dumping the second boom, followed by being output to the valve
17
through a multiplier (see
FIG. 4
) shown at the block B
16
.
One example of the relationship between the deviation ΔZ and the restoration gain K
sbdd
set in the control gain block
200
is shown in FIG.
10
(
a
) in enlarged scale. The relationship between the deviation ΔZ and the restoration gain K
sbdd
is set as follows. When the deviation ΔZ is a positive value, the restoration gain K
sbdd
is 0. When the deviation ΔZ becomes a negative value (i.e., when the arm end enters the restoration area), the restoration gain K
sbdd
is gradually increased as the deviation ΔZ reduces. When the deviation ΔZ is not larger than a certain negative value, the restoration gain K
sbdd
is kept at 1.
In the block
205
, the arm end speed is calculated from the following formula:
(“′”) represents differentiation similarly to “′” in the description).
In the block
206
, the arm end target speed (X′
n
, Y′
n
) is determined by the following formulae:
X′
n
=−X′
Y′
n
=Y′ (4)
when the arm end enters R
2
from the slowdown area R
1
indicated by hatching A in
FIG. 11
, and
X′
n
=X′
Y′
n
=−Y′ (5)
when the arm end enters R
2
from the slowdown area R
1
indicated by hatching B in FIG.
11
.
In the block
207
, the second-boom target angular speed θ′
2n
is determined by the following formulae:
when the arm end target speed determined in the block
206
is given by the formula (4), and
when the arm end target speed determined in the block
206
is given by the formula (5).
One example of the relationship between the second-boom cylinder target speed S
2n
and the feedback gain K
sbf
set in the feedback gain block
209
is shown in FIG.
10
(
b
) in enlarged scale. The relationship between the second-boom cylinder target speed S
2n
and the feedback gain K
sbf
is set such that the gain K
sbf
is 1, for example, when the second-boom cylinder target speed S
2n
is at maximum, and is reduced as the second-boom cylinder target speed S
2n
lowers.
A characteristic of the metering table
201
is a reversal of the characteristic relationship between the second-boom dumping pilot pressure P
sbd
and a cylinder target speed M
sbd
that is determined depending on an opening area characteristic of the flow control valve
11
in the direction to dump the second boom. Note that, for the horizontal axis of the metering table
201
, the cylinder target speed M
sbd
is converted into a gain.
With the above functional arrangement, when the arm end enters the restoration area R
2
, the control gain block
200
calculates the restoration gain K
sbdd
corresponding to an intrusion amount by which the arm end enters the restoration area R
2
, while the feedback gain block
209
calculates the feedback gain corresponding to an arm end speed at that time. The second boom
2
is dumped at a speed depending on the intrusion amount of the arm end into the restoration area R
2
and the arm end speed so that the arm end is moved for return to the slowdown area R
1
.
The operation of this embodiment thus constructed will now be described. The following description will be made on, as work examples, (a) the case of not raising the first boom, (b) the case of raising the first boom, but not crowding the arm, and (c) the case of raising the first boom and crowding the arm.
(a) Case of not Raising First Boom
In the case that the pilot valve
19
associated with the first-boom flow control valve
10
for raising the first boom is not operated, but any of the other pilot valves, e.g., the pilot valve
21
associated with the second-boom flow control valve
11
for crowding the second boom or the pilot valve
23
associated with the arm flow control valve
12
for crowding the arm, is operated, when the arm end position exceeds the boundary line K
2
and enters the slowdown area R
1
, the proportional solenoid pressure reducing valve
16
or
18
is operated to reduce the pilot pressure for slowing down and stopping the cylinder
2
A or
3
A of the second boom
2
or the arm
3
so that the arm end is stopped at the boundary line K
1
, on the basis of the functions shown at
108
,
109
,
119
,
110
and
111
or
112
,
113
,
123
,
114
and
115
in FIG.
6
.
At this time, the slowdown gain in the block
105
or
113
is modified to increase as the pilot pressure becomes higher, as described above in connection with FIG.
8
(
b
). Therefore, when the arm end position exceeds the boundary line K
2
, the slowdown control is started regardless of the level of the pilot pressure and smooth slowdown control is always ensured.
The above description is also equally applied to when the pilot valve
20
associated with the first-boom flow control valve
10
for lowering the first boom is operated.
On the other hand, at that time, the first-boom raising pilot pressure P
fbu
is not input to the block B
14
shown in FIG.
4
and the block B
14
outputs a 0-level signal. Accordingly, the restoration control of the block B
12
is not effected even though the arm end enters the restoration area R
2
to some extent due to inertia of the work front
42
.
Additionally, in work carried out by operating the second boom and/or the arm in the crowding direction without raising the first boom, the operator intends to carry out the operation only requiring the work front to be moved toward the operator (cab) in many cases. In such work, if the work front is moved in a direction away from the excavator body by dumping the second boom, the movement of the work front would be unexpected one for the operator, and if there is an object such as a wall in the dumping direction, the work front may hit against the object. By slowing down and stopping the work front as described above, the movement unexpected for the operator is avoided and good operability is ensured.
(b) Case of Raising First Boom, but not Crowding Arm
In the case that the pilot valve
19
associated with the first-boom flow control valve
10
for raising the first boom is operated, but the pilot valve
23
associated with the arm flow control valve
12
for crowding the arm is not operated, when the arm end position exceeds the boundary line K
2
and enters the slowdown area R
1
, the proportional solenoid pressure reducing valve
13
is operated to reduce the pilot pressure for slowing down the first boom cylinder
1
A to effect the slowdown control so that the first-boom raising speed is reduced to a value determined by the slowdown gain in the block
101
and the arm end speed is lowered correspondingly, on the basis of the functions shown at
100
,
101
,
117
,
102
and
103
in FIG.
6
.
On the other hand, at this time, the first-boom raising pilot pressure P
fbu
is input to the block B
14
shown in FIG.
4
and the block B
14
outputs a 1-level signal. Accordingly, when the arm end position exceeds the boundary line K
1
and enters the restoration area R
2
, the block
13
also outputs a 1-level signal, whereupon the restoration control of the block
12
is started for moving the arm end position back to the slowdown area R
1
outside the boundary line K
1
.
More specifically, the restoration gain is calculated depending on the intrusion amount of the arm end into the restoration area R
2
in the control gain block
200
of
FIG. 9
, and the feedback gain is calculated depending on the arm end speed at that time on the basis of the functions shown at
204
,
205
,
206
,
208
and
209
. In accordance with those calculated gains, the second boom
2
is automatically dumped depending on the intrusion amount of the arm end into the restoration area R
2
and the arm end speed at that time, causing the arm end position to be moved for return to the slowdown area R
1
.
Thus, when the arm end position exceeds the boundary line K
2
and enters the slowdown area R
1
, the first-boom raising operation is slowed down to a predetermined speed, and when the arm end position exceeds the boundary line K
1
and enters the restoration area R
2
, the arm end is controlled to move while going around the excavator body, particularly the cab, with a combination of the slowed-down first-boom raising operation and the second-boom dumping operation based on the restoration control. As a result, the work front can be continuously smoothly moved without being stopped while avoiding interference with the excavator body, particularly the cab, and working efficiency can be improved.
(c) Case of Raising First Boom and Crowding Arm
In the case that the pilot valve
19
associated with the first-boom flow control valve
10
for raising the first boom is operated and the pilot valve
23
associated with the arm flow control valve
12
for crowding the arm is also operated, the slowdown control and the restoration control described in the above (b) are both effected. In addition, as described in connection with FIG.
8
(
c
), the modified slowdown gain Kac* is set to increase as the first-boom raising pilot pressure P
fbu
becomes higher, thereby suppressing a slowdown amount so that the arm end enters the restoration area R
2
while maintaining a certain arm crowding speed corresponding to the first-boom raising speed, on the basis of the functions shown at
116
,
120
,
121
and
122
in FIG.
6
.
If the arm crowding operation is also subject to the slowdown control so that the arm is stopped at the boundary line K
1
, the slowdown control of the arm crowding operation would be resumed upon the arm end being returned to the slowdown area R
1
with the dumping of the second boom after entering the restoration area R
2
; hence the arm crowding operation would repeat the stop and slowdown, resulting in jerky movement of the work front.
With this embodiment, since the arm end enters the restoration area R
2
while maintaining a certain arm crowding speed corresponding to the first-boom raising speed, the arm crowding operation is continuously subject to the slowdown control and the interference avoidance control can be smoothly performed.
According to this embodiment, as described above, when the arm end position exceeds the boundary line K
1
and enters the restoration area R
2
, the arm end is moved for return to the slowdown area R
1
with the dumping of the second boom. Therefore, the work front is prevented from interfering with the cab without being stopped, and such work as requiring the work front to be moved toward the operator (cab) can be continuously smoothly performed.
Also, since the restoration control is performed with the dumping of the second boom, as described above, under the operation of raising the first boom, the arm end is controlled to move while going around the cab with a combination of the first-boom raising operation and the second-boom dumping operation based on the restoration control. As a result, the interference avoidance control can be smoothly achieved.
Further, in work carried out by not operating the first boom in the rising direction, but operating the second boom and/or the arm in the crowding direction, the work front is controlled to just slow down and stop when the predetermined position of the work front comes close to the excavator body. Hence the movement unexpected for the operator is avoided and good operability is ensured.
Moreover, since the slowdown control is first effected when the arm end position exceeds the boundary line K
2
and the restoration control is then performed with the dumping of the second boom, the flow rate supplied to the first boom cylinder
1
A is reduced and the second boom cylinder
2
A can be supplied with the hydraulic fluid at a sufficient flow rate, enabling the second boom
2
to be quickly dumped, even when there is a limit in maximum capacity of the hydraulic pump
29
. Also, since the front members are slowed down before starting to control the second boom to dump, the intrusion amount of the arm end into the restoration area R
2
is suppressed. It is thus possible to surely prevent interference between the work front and the excavator body.
In addition, since the second boom
2
is dumped in accordance with the feedback gain which is calculated depending on the arm end speed, a dumping speed of the second boom in match with the arm end speed is obtained and smooth interference avoidance control is achieved. Also, since the restoration gain is calculated depending on the intrusion amount of the arm end into the restoration area R
2
, the second boom dumping speed is increased as the arm end comes closer to the cab, and interference between the work front and the excavator body can be surely prevented.
Under the combined operation of raising the first boom and crowding the arm, when the arm end enters the restoration area R
2
, it is controlled to maintain a certain arm crowding speed at the time of entering the restoration area R
2
. Accordingly, the arm crowding operation is avoided from repeating the stop and slowdown in the restoration control with the dumping of the second boom and smooth interference avoidance control can be achieved.
Since the slowdown gain is modified by being multiplied by the cylinder target speed obtained in the metering characteristic block, when the deviation ΔZ becomes not larger than the slowdown start distance r
0
, the slowdown control is started in accordance with the predetermined characteristic regardless of the level of the operation pilot pressure, and smooth slowdown control can be always ensured.
Additionally, in this embodiment, when the arm end position enters the restoration area R
2
, the arm end is moved for return to the slowdown area R
1
with the dumping of the second boom, as described above, whereby the work front is prevented from interfering with the cab without being stopped. In this respect, the movement of the arm end for return to the slowdown area R
1
(i.e., the movement of the arm end away from the cab) can also be obtained by moving the arm in the dumping direction, as described later. However, the arm is a front member which is employed to carry out work itself during ordinary work (e.g., excavating). If the arm is dumped in the crowding direction under action of the above-described control during work that is carried out by the operator manipulating the control lever to move the arm in the crowding direction, this means that the arm is moved contrary to the intent of the operator, thus making the operator feel awkward. On the other hand, the second boom of the 2-piece boom type hydraulic excavator is employed in many cases as the so-called positioning boom to select a region of work in the longitudinal direction before starting the work, and is less frequently employed in actual work. This means that even when the second boom is moved in the dumping direction under the above-described control, a degree of awkward feeling perceived by the operator is small. As a result, in this embodiment, the interference avoidance control can be smoothly performed without impairing an operation feeling of the operator.
Thus, with this embodiment, such work as requiring the work front to be moved toward the operator can be continuously smoothly performed and working efficiency can be greatly improved.
A second embodiment of the present invention will be described with reference to
FIGS. 12 and 13
. While only the second boom is dumped under the restoration control in the first embodiment, the second boom and the arm are both dumped in this second embodiment. In those drawings, equivalent members or functions to those shown in
FIGS. 1 and 9
are denoted by the same reference numerals.
In
FIG. 12
, an interference prevention system according to this embodiment comprises, in addition to the components of the first embodiment shown in
FIG. 1
, a proportional solenoid pressure reducing valve
15
for reducing the pilot pressure supplied from the pilot hydraulic source
32
, and a shuttle valve
34
for selecting higher one of the pilot pressure output from the pilot valve
24
and the pilot pressure output from the proportional solenoid pressure reducing valve
15
and applying the selected pilot pressure to the flow control valve
12
.
An overall control algorithm of a controller
50
A is the same as in the first embodiment shown in FIG.
4
. Also, details of the control algorithm is the same as in the first embodiment except the restoration control in the block B
12
.
Details of the restoration control in the block B
12
is shown in a functional block diagram of FIG.
13
.
Referring to
FIG. 13
, the control algorithm in this embodiment comprises, in addition to the blocks
208
,
209
,
200
,
203
,
201
and
202
associated with the operation of dumping the second boom, blocks
208
,
209
,
200
,
203
,
201
and
202
associated with the operation of dumping the arm.
Also, a block
207
A calculates, in addition to the second-boom target angular speed θ′
2n
, an arm target angular speed θ′
2nA
from the arm end target speed (X′
n
, Y′
n
), and a block
208
A determines an arm cylinder target speed S
2nA
from the arm target angular speed θ′
2nA
. Further, a feedback gain block
209
A determines a feedback gain K
af
from the arm cylinder target speed S
2nA
.
A control gain block
210
calculates a restoration gain K
acd
for the arm dumping operation from the deviation ΔZ. As with the restoration gain K
sbdd
for the second-boom dumping operation described in connection with the first embodiment, the feedback gain K
af
obtained on the basis of the functions shown at
204
,
205
,
206
,
207
A,
208
A and
209
A is added, in an adder
213
, to the restoration gain K
acd
calculated in the control gain block
210
. A target pilot pressure P
acn
is calculated from a resulting gain K
ac
by referring to a metering table
211
, and the calculated pilot pressure is converted, by referring to a voltage table
212
, into an output voltage for the proportional solenoid pressure reducing valve
15
for dumping the arm, followed by being output to the valve
15
through the multiplier (see
FIG. 4
) shown at the block B
16
.
The relationship between the deviation ΔZ and the restoration gain K
add
set in the control gain block
210
and the relationship between the arm cylinder target speed S
2nA
and the feedback gain K
af
set in the feedback gain block
209
A are essentially the same as those ones shown in FIGS.
10
(
a
) and
10
(
b
), respectively.
A characteristic of the metering table
211
is a reversal of the characteristic relationship between an arm dumping pilot pressure P
ad
and a cylinder target speed M
ad
that is determined depending on an opening area characteristic of the flow control valve
12
in the direction to dump the arm. Note that, for the horizontal axis of the metering table
211
, the cylinder target speed is also converted into a gain.
With the above functional arrangement, when the arm end enters the restoration area R
2
, the control gain blocks
200
,
210
respectively calculate the restoration gains K
sbdd
, K
add
corresponding to an intrusion amount by which the arm end enters the restoration area R
2
, while the feedback gain blocks
209
,
209
A calculates the feedback gains corresponding to an arm end speed at that time. The second boom
2
and the arm
3
are dumped at respective speeds depending on the intrusion amount of the arm end into the restoration area R
2
and the arm end speed so that the arm end is moved for return to the slowdown area R
1
.
In this embodiment, therefore, since the arm end is moved for return to the slowdown area R
1
with the dumping of both the second boom
2
and the arm
3
, the arm end is controlled to quickly move while going around the excavator body more smoothly, and working efficiency is further improved.
A third embodiment of the present invention will be described with reference to
FIGS. 14 and 15
. While the pilot valves are used as operating means in the above embodiments, this third embodiment uses electric levers as operating means.
In
FIG. 14
, an interference prevention system according to this embodiment has electric lever units
19
A-
24
A instead of the pilot valves
19
-
24
as operating means in the first embodiment shown in FIG.
1
. In respective pilot operating systems of the flow control valves
10
,
11
and
12
, there are provided proportional solenoid pressure reducing valves
13
,
14
,
16
,
55
,
18
and
56
for generating pilot pressures depending on stroke amounts by which the electric lever units
19
A-
24
A are operated, based on the pilot pressure from the pilot hydraulic source
32
. There is also provided a proportional solenoid pressure reducing valve
17
for reducing the pilot pressure from the pilot hydraulic source
32
. Higher one of the pilot pressure output from the pilot valve
55
and the pilot pressure output from the proportional solenoid pressure reducing valve
17
is selected by a shuttle valve
33
and then applied to the flow control valve
11
.
A controller
50
B receives signals from the electric lever units
19
A-
24
A and the angle sensors
5
,
6
,
7
and the pressure sensors
25
,
26
,
27
,
28
, and outputs control signals for controlling the work front
42
to the proportional solenoid pressure reducing valves
13
,
14
,
16
,
55
,
17
,
18
and
56
based on the received operation signals and angle signals.
An overall control algorithm of the controller
50
B is shown in FIG.
15
. The controller
50
B has a section C
2
for calculating and outputting command voltage for the proportional solenoid pressure reducing valves
55
,
56
in addition to a similar section C
1
for calculating and outputting command voltages for the proportional solenoid pressure reducing valves
13
,
14
,
16
,
17
and
18
as shown in FIG.
4
. Note that operation signals input to the section C
1
are given as operation signals (electric signals) D
fbu
, D
gbd
, D
sbc
and D
ac
from the respective electric lever units substituted for the operation pilot pressures. Details of a slowdown control block B
11
and a restoration control block B
12
is the same as shown in
FIGS. 6 and 9
except that metering characteristics are set to be adaptable for the electric signals from the electric lever units.
In the section C
2
, operation signals D
sbd
and D
ad
from the electric lever units
22
A,
24
A are converted into the command voltages based on a metering characteristic block (e.g.,
100
in FIG.
6
), a metering table (e.g.,
102
in
FIG. 6
) and a voltage table (e.g.,
103
in FIG.
6
), followed by being output to the proportional solenoid pressure reducing valves
55
,
56
.
This embodiment thus constructed operates in a similar manner to the first embodiment, and hence can provide similar advantages in a system using the electric lever units as operating means to those obtainable with the first embodiment.
A fourth embodiment of the present invention will be described with reference to
FIGS. 16-18
. In this embodiment, the arm is dumped instead of the second boom. In those drawings, equivalent members or functions to those shown in
FIGS. 1
,
6
,
9
,
12
and
13
are denoted by the same reference numerals.
In
FIG. 16
, an interference prevention system according to this embodiment includes a proportional solenoid pressure reducing valve
15
and a shuttle valve
34
which are associated with the arm flow control valve
12
only in the direction to dump the arm and are similar to those used in the second embodiment shown in
FIG. 12
, instead of the proportional solenoid pressure reducing valve
17
and the shuttle valve
22
which are associated with the second-boom flow control valve
11
in the direction to dump the second boom in the first embodiment shown in FIG.
1
.
An overall control algorithm of a controller
50
C is the same as in the first embodiment shown in FIG.
4
.
Details of restoration control in a block B
11
(see
FIG. 4
) of the controller
50
C is shown in a functional block diagram of FIG.
17
.
In this embodiment, since the arm is dumped instead of the second boom, a control process of the proportional solenoid pressure reducing valve
13
for crowding the second boom and a control process of the proportional solenoid pressure reducing valve
18
for crowding the arm in the functional block diagram for the slowdown control are replaced with each other as compared with those control processes shown in FIG.
6
.
More specifically, the proportional solenoid pressure reducing valve
18
for crowding the arm is controlled with a control gain block
113
, an arm crowding metering characteristic block
112
, a multiplying block
123
, a metering table
114
, and a voltage table
115
. On the other hand, the proportional solenoid pressure reducing valve
13
for crowding the second boom is controlled with a control gain block
109
, a second-boom crowding metering characteristic block
108
, a multiplying block
119
, a metering table
110
, and a voltage table
111
, as well as a first-boom raising pilot pressure gain block
116
and blocks
120
-
123
in which gains obtained in the blocks
109
,
116
are combined with each other. At the time when the arm end exceeds the boundary line K
1
(see FIG.
11
), it is controlled to enter the restoration area R
2
while maintaining a certain second-boom crowding speed corresponding to the first-boom raising speed, so that the second boom crowding control is prevented from interfering with the arm dumping control.
Details of restoration control in a block B
12
(see
FIG. 4
) of the controller
50
C is shown in a functional block diagram of FIG.
18
. The control algorithm in this embodiment includes blocks
207
B,
208
A,
209
A,
210
,
213
,
211
and
212
associated with the operation of dumping the arm, instead of the blocks
207
,
208
,
209
,
200
,
203
,
201
and
202
associated with the operation of dumping the second boom in the first embodiment shown in FIG.
9
.
The block
207
B calculates an arm target angular speed θ′
2nA
from the arm end target speed (X′
n
, Y′
n
). Functions of the other blocks
208
A,
209
A,
213
,
211
and
212
are similar to those in the second embodiment shown in FIG.
13
.
With such a functional arrangement, when the arm end enters the restoration area R
2
(see FIG.
11
), the control gain block
210
calculates the restoration gain K
add
corresponding to an intrusion amount by which the arm end enters the restoration area R
2
, while the feedback gain block
209
calculates the feedback gain corresponding to an arm end speed at that time. The arm
3
is dumped at a speed depending on the intrusion amount of the arm end into the restoration area R
2
and the arm end speed so that the arm end is moved for return to the slowdown area R
1
.
In this embodiment, therefore, since the arm end is moved for return to the slowdown area R
1
with the dumping of the arm
3
, the arm end is controlled to move while going around the excavator body, and such work as requiring the work front to be moved toward the operator can be continuously smoothly performed.
Industrial Applicability
According to the present invention, when the predetermined position of the work front comes close to the excavator body, the second boom is controlled so as to dump. It is therefore possible to continuously smoothly carry out such work as requiring the work front to be moved toward the operator (cab) while avoiding interference between the work front and the cab, and to greatly improve working efficiency.
Claims
- 1. An interference prevention system for a 2-piece boom type hydraulic excavator, said interference prevention system being installed in a 2-piece boom type hydraulic excavator comprising an excavator body, a work front mounted on said excavator body and having a plurality of front members including first and second booms and an arm which are vertically rotatable, a first boom cylinder for driving said boom, a second boom cylinder for driving said second boom, an arm cylinder for driving said arm, a first-boom flow control valve for controlling a flow rate of a hydraulic fluid supplied to said first boom cylinder in accordance with an operation signal from first-boom operating means, a second-boom flow control valve for controlling a flow rate of a hydraulic fluid supplied to said second boom cylinder in accordance with an operation signal from second-boom operating means, and an arm flow control valve for controlling a flow rate of a hydraulic fluid supplied to said arm cylinder in accordance with an operation signal from arm operating means, said interference prevention system serving to restrict movement of said work front when a predetermined position of said work front comes close to said excavator body, wherein said interference prevention system comprises:attitude detecting means for detecting an attitude of said work front, and control means for receiving detection signals from said attitude detecting means and, when the predetermined position of said work front comes close to said excavator body, outputting a command signal to said second-boom flow control valve so that said second boom is moved in a dumping direction.
- 2. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 1, wherein when said first boom is operated in a rising direction by said operating means for said first boom, said control means makes control to move said second boom in the dumping direction while continuing to raise said first boom.
- 3. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 2, wherein said control means receives an operation signal in the first-boom raising direction output from said operating means for said first boom, and modifies the operation signal in the first-boom raising direction such that first-boom raising operation is slowed down as the predetermined position of said work front comes closer to said excavator body, and thereafter the first-boom raising operation is continued at a slowed-down speed.
- 4. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 2, wherein said control means receives an operation signal in a second-boom crowding direction output from said operating means for said second boom and an operation signal in an arm crowding direction output from said operating means for said arm, and modifies the operation signal in the second-boom crowding direction and the operation signal in the arm crowding direction such that when said first boom is not moved in the rising direction, said work front is slowed down as the predetermined position of said work front comes closer to said excavator body and thereafter the work front is stopped.
- 5. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 2, wherein said control means receives an operation signal in an arm crowding direction output from said operating means for said arm, and modifies the operation signal in the arm crowding direction such that when said first boom is moved in the rising direction, an arm crowding operation is slowed down as the predetermined position of said work front comes closer to said excavator body, and thereafter the arm crowding operation is continued at a slowed-down speed.
- 6. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 1, wherein said control means calculates a target speed of said second boom in the dumping direction corresponding to a moving speed of the predetermined position of said work front, and makes said control so that said second boom is moved at the calculated target speed.
- 7. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 6, wherein said control means calculates the target speed of said second boom in the dumping direction to provide a higher target speed value as a moving speed of the predetermined position of said work front increases.
- 8. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 1, wherein said control means calculates a target speed of said second boom in the dumping direction that increases as the predetermined position of said work front comes closer to said excavator body, and makes said control so that said second boom is moved at the calculated target speed.
- 9. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 1, wherein:said attitude detecting means includes means for calculating a distance (ΔZ) from the predetermined position of said work front to an area previously set around said excavator body, and said control means modifies the operation signals from said operating means such that when said calculated distance is not larger than a preset first control start distance, said work front is gradually slowed down as said calculated distance becomes smaller, modifies the operation signals from said operating means such that when said calculated distance reaches a preset second control start distance smaller than said first control start distance, said front members are stopped except at least operation of raising said first boom, and makes control such that when said calculated distance is not larger than said second control start distance, said second boom is moved in the dumping direction.
- 10. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 9, wherein said control means modifies the operation signals from said operating means such that when said calculated distance (ΔZ) reaches said preset second control start distance smaller than said first control start distance, said front members are stopped except operations of raising said first boom and crowding said arm.
- 11. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 9, wherein said control means receives the operation signals from said operating means and modifies the operation signals from said operating means such that a degree of slowdown is reduced with an increase in stroke amounts by which said operating means are operated.
- 12. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 1, wherein when the predetermined position of said work front comes close to said excavator body, said control means outputs command signals to said second-boom flow control valve and said arm flow control valve so that said second boom and said arm are both moved in the dumping direction.
- 13. An interference prevention system for a 2-piece boom type hydraulic excavator according to claim 1, wherein when the predetermined position of said work front comes close to said excavator body, said control means outputs a command signal to said arm flow control valve so that said arm is moved in the dumping direction instead of said second boom.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9-000584 |
Jan 1997 |
JP |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
102e Date |
371c Date |
PCT/JP98/00014 |
|
WO |
00 |
9/3/1998 |
9/3/1998 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO98/30759 |
7/16/1998 |
WO |
A |
US Referenced Citations (5)
Foreign Referenced Citations (8)
Number |
Date |
Country |
2-308018 |
Dec 1980 |
JP |
3-156037 |
Jul 1991 |
JP |
3-217523 |
Sep 1991 |
JP |
3-228929 |
Oct 1991 |
JP |
6-313323 |
Nov 1994 |
JP |
6-104985 |
Dec 1994 |
JP |
8-4046 |
Jan 1996 |
JP |
8-333767 |
Dec 1996 |
JP |