Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Construction or agricultural-type vehicle
Reexamination Certificate
2000-11-07
2003-04-08
Nguyen, Tan Q. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Construction or agricultural-type vehicle
C060S468000, C091S361000
Reexamination Certificate
active
06546325
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a device for controlling a working arm of a working machine. More specifically, the invention relates to a device for controlling a working arm, which is capable of suitably controlling a pressure that generates and is confined in a hydraulic cylinder provided in a working arm device of a working machine such as a front shovel device of a hydraulic shovel, a lift arm device of a wheel loader, and the like.
BACKGROUND ART
With reference to
FIG. 8
, a hydraulic shovel as generally designated at
2
, which is a typical working machine equipped with a working arm device, includes a lower running body
4
and an upper turning body
6
mounted on the lower running body
4
to freely turn on a pivot
5
. The upper turning body
6
is provided with a front shovel device
8
that is a working arm device. The front shovel device
8
includes a boom
10
mounted on the upper turning body
6
to freely turn in the up and down directions, a boom actuation cylinder
12
interposed between the upper turning body
6
and the boom
10
, an arm
14
mounted on an end of the boom
10
to freely turn, an arm actuation cylinder
16
interposed between the arm
14
and the boom
10
, an attachment
18
attached to an end of the arm
14
to freely turn, such as a breaker, and an attachment actuation cylinder
20
interposed between the attachment
18
and the boom
10
.
With reference to
FIG. 8
together with
FIG. 9
, the hydraulic shovel
2
is equipped with the above-mentioned hydraulic actuators and a hydraulic pressure control unit for controlling the actuation of the hydraulic actuators such as the attachment
18
, a turning motor
22
and a pair of running motors
24
a,
24
b.
The hydraulic pressure control unit includes hydraulic pumps
28
a,
28
b
driven by a motor
26
, and a control valve
30
that controls a blow-out fluid to supply it to the hydraulic actuators. The control valve
30
includes plural direction control valves corresponding to each of the hydraulic actuators. A direction control valve
32
is connected to the arm actuation cylinder
16
, a direction control valve
34
is connected to the attachment actuation cylinder
20
, and a direction control valve
36
is connected to the boom actuation cylinder
12
. The direction control valve
32
is operated by a pilot fluid output from an arm operation remote control valve
38
a
of a pilot operation means
38
, and the direction control valve
34
is operated by a pilot fluid output from an attachment operation remote control valve
38
b
of the operation means
38
. To a fluid passage
40
a
on the rod side, which is a pressurized fluid feed/drain circuit connecting the attachment actuation cylinder
20
to the direction control valve
34
, there are connected a cylinder relief valve
42
a
for limiting the hydraulic pressure in the fluid passage
40
a
and a check valve
44
a
that permits flow of the actuation fluid from a tank
46
into the fluid passage
40
a.
Similarly, a cylinder relief valve
42
b
and a check valve
44
b
are connected to a fluid passage
40
b
of the head side.
With further reference to
FIGS. 10 and 11
, when the attachment actuation cylinder
20
is extended and contracted by the operation of the attachment operation remote control valve
38
b,
the attachment
18
pivots on an end of the arm
14
between a position where the attachment
18
is pulled toward the side of the upper turning body
6
shown in
FIG. 10 and a
position where the attachment
18
is separated far away from the upper turning body
6
shown in FIG.
11
. The arm
14
is provided with stoppers
14
a
and
14
b
for limiting the turning ends of the attachment
18
. When the arm actuation cylinder
16
is extended and contracted by the operation of the arm operation remote control valve
38
a,
the arm
14
pivots on an end of the boom
10
as a center between a position (solid lines) where the attachment
18
is pulled toward the upper turning body
6
shown in
FIGS. 10 and 11
and a position (two-dot chain lines) where the attachment
18
is separated far away from the upper turning body
6
shown in
FIGS. 10 and 11
. Thus, the attachment
18
can be brought to any desired position to meet the work.
Referring to
FIGS. 10 and 11
illustrating the working states of the working arm device
8
,
FIG. 10
shows a state where the attachment actuation cylinder
20
is contracted to fully turn the attachment
18
until it comes into contact with the stopper
14
a
to maintain the attachment actuation cylinder
20
in a state of being not in operation and the arm actuation cylinder
16
is extended to turn the arm
14
in a direction of an arrow U to lift it up.
FIG. 11
shows a state where the attachment actuation cylinder
20
is extended to bring the attachment
18
into contact with the other stopper
14
b
to maintain the attachment actuation cylinder
20
in a state of being extended and the arm actuation cylinder
16
is contracted to turn the arm
14
in a direction of an arrow D to lower it down.
In the state of
FIG. 10
, as the arm actuation cylinder
16
is extended, the overall length of the attachment actuation cylinder
20
in its state of being maintained extends from X
1
to X
2
due to a difference in the positions of mounting the arm
14
and of mounting the attachment actuation cylinder
20
on the boom
10
. The extension of the attachment actuation cylinder
20
in this state of being maintained is accomplished by releasing the actuation fluid in a fluid chamber
20
a
on the rod side, that is compressed with the progress of extension, into a tank
46
under a set pressure of the cylinder relief valve
42
a,
and filling up a fluid chamber
20
b
on the head side with the actuation fluid from the tank
46
via a check valve
44
a.
In the state shown in
FIG. 11
, as the arm actuation cylinder
16
is contracted, the overall length of the attachment actuation cylinder
20
in its state of being maintained contracts from X
3
to X
4
. The actuation fluid in the fluid chamber
20
b
on the head side, that is compressed with the progress of contraction, is released into the tank
46
under a set pressure of the cylinder relief valve
42
b
and the fluid chamber
20
a
on the rod side is filled up with the actuation fluid from the tank
46
via a check valve
44
b.
DISCLOSURE OF THE INVENTION
The above-mentioned conventional working arm device involves problems that must be solved as described below.
That is, as the attachment
18
comes into contact with the stopper
14
a
or
14
b
thereby to bring the attachment actuation cylinder
20
into a state of being not in operation and the arm actuation cylinder
16
is extended or contracted, the cylinder relieve valve
42
a
or
42
b
works to release the actuation fluid confined in the attachment actuation cylinder
20
. Therefore, the hydraulic force for extending or contracting the arm actuation cylinder
16
is raised by an amount of energy for releasing the actuation fluid from the relief valve
42
a
or
42
b.
Hence, this amount becomes a loss of energy.
In addition, the above energy released with a high pressure turns into heat and causes the actuation fluid to be overheated. Further, the actuation speed of the arm actuation cylinder
16
decreases due to an increase in the load resistance at the time of extension or contraction. Depending upon the weight of the attachment
18
and positions of turning of the attachment
18
and the arm
14
, further, the arm actuation cylinder
16
comes into a halt due to the load resistance. Consequently, the workability of the working arm device
8
is deteriorated.
Though this problem can be improved if the set pressure of the cylinder relief valves
42
a
and
42
b
is lowered, the lowering of the set pressure results in a decrease in a maximum output of the attachment actuation cylinder
20
limited by the set pressure and in a decrease in the force for holding the attachment
18
to the arm
14
thereby to weaken the operation force of the attachment
18
, with t
Kubota Yorimichi
Kurokawa Yoshikazu
Matoba Nobuaki
Nozaki Shinya
Nguyen Tan Q.
Shin Caterpillar Mitsubishi Ltd.
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