Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
1998-11-10
2001-01-09
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C060S429000, C060S430000
Reexamination Certificate
active
06170261
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pressurized hydraulic fluid supply apparatus for delivering hydraulic fluids under pressure from a plurality of hydraulic pumps to a plurality of hydraulic actuators equipped in a power shovel (hydraulically actuated excavator and loader) or the like.
BACKGROUND ART
An example of such an apparatus is proposed in Japanese Patent Publication No. Hei 7-92090. In this pressurized hydraulic fluid supply apparatus, a hydraulic fluid delivered under pressure from a first hydraulic pump is supplied through a plurality of operation valves to a plurality of hydraulic actuators on one side and a hydraulic fluid delivered under pressure from a second hydraulic pump is supplied through a plurality of operation valves to a plurality of hydraulic actuators on the other side. The pressurized hydraulic fluid supply apparatus has a flow merge/separation valve to merge or separate the hydraulic fluid from the first hydraulic pump and the hydraulic fluid from the second hydraulic pump.
In the flow separation state, the pressurized hydraulic fluid supply apparatus delivers the pressurized fluid from the first hydraulic pump and the pressurized fluid from the second hydraulic pump individually to the actuators on one side and to the actuators on the other side. Bringing the pressurized hydraulic fluid supply apparatus into the flow separation state can reduce the energy loss of the pumps.
The apparatus of the above-mentioned Japanese Patent Publication No. Hei 7-92090, however, has the following drawbacks. In the apparatus of this kind, the pilot pressure for switching the flow merge/separation valve is often common to a pilot pressure for driving a directional control valve connected to the actuators. That is, the flow merging/separation is switched according to the lever operation by an operator. Here, let us consider a case where one wishes to perform, for example, a fine operation. The pilot pressure for driving the directional control valve during the fine operation is small. There is a large difference in load pressure between the first and second hydraulic circuits, and the flow merge/separation valve remains in the flow merging state because the pilot pressure for switching the valve is low. In this condition, the apparatus with the conventional configuration causes pump energy losses.
In the flow merging/separation control on the two hydraulic circuits, when a load pressure difference occurs, the hydraulic circuits may be merged, contrary to the above case, to equalize the loads and the delivery rates between the two pumps. At this time, if the switching is to be made by the pilot pressure, the following situation arises because of the low pilot pressure. Where the first pump is connected with a left-side travel motor and the second pump is connected with a right-side travel motor and actuators, if the actuators are driven with the hydraulic lines separated, the flow separation state fails to be switched to the flow merging state, resulting in an insufficient flow into the right-side travel motor causing the power shovel to advance in a curved path.
It is an object of this invention to provide a pressurized hydraulic fluid supply apparatus which can switch between the flow merging state and the flow separation state according to the driving state of a plurality of actuators and can keep the flow balance among a plurality of hydraulic pump lines in good condition.
DISCLOSURE OF THE INVENTION
The first invention is characterized by the pressurized hydraulic fluid supply apparatus which comprises: a first circuit having a first hydraulic pump
1
, a first hydraulic actuator
6
connected to a delivery passage
2
of the first hydraulic pump
1
, a first directional control valve
5
for controlling the first hydraulic actuator
6
, and a first pressure compensation valve
4
for making constant a pressure difference between upstream and downstream pressures of the first directional control valve
5
; a second circuit having a second hydraulic pump
11
, a second hydraulic actuator
16
connected to a delivery passage
12
of the second hydraulic pump
11
, a second directional control valve
15
for controlling the second hydraulic actuator
16
, and a second pressure compensation valve
14
for making constant a pressure difference between upstream and downstream pressures of the second directional control valve
15
; a third circuit having a third hydraulic actuator
21
connected to the delivery passage
12
of the second hydraulic pump
11
, a third directional control valve
20
for controlling the third hydraulic actuator
21
, and a third pressure compensation valve
19
for making constant a pressure difference between upstream and downstream pressures of the third directional control valve
20
; and a merge/separation valve
40
for merging and separating the delivery passage
2
of the first hydraulic pump
1
and the delivery passage
12
of the second hydraulic pump
11
; wherein the merge/separation valve
40
is preferentially set to a flow merging state by the driving of the third hydraulic actuator
21
.
With the first invention, the driving of the hydraulic actuator
21
results in the merge/separation valve
40
shifting to the flow merging state. Because the merge/separation valve
40
is automatically shifted to the flow merging state according to the operation of the operation valve, an unintended flow difference between the first actuator and the second actuator, which would otherwise occur, can be prevented.
The second invention is characterized in that the merge/separation valve
40
in the first invention has a pilot pressure receiving portion
42
and is switched to a flow separation position H by a pressurized hydraulic fluid acting on the pressure receiving portion
42
and that a selector valve
43
is provided which supplies or cuts off a load pressure of the first hydraulic actuator or the second hydraulic actuator to the pressure receiving portion
42
and which is switched according to the driving of the third hydraulic actuator
21
.
With the second invention, when the third operation valve
20
is operated to supply the pressurized hydraulic fluid to the third hydraulic actuator
21
, the load pressure of the actuator
21
shifts the selector valve
43
to a position that stops the supply of the hydraulic fluid to the merge/separation valve
40
, which in turn is allowed to be shifted to the flow merging position G. When on the other hand the third operation valve
20
is not operated, the hydraulic fluid is not supplied to the third hydraulic actuator
21
and therefore the load pressure is not produced in the actuator
21
. At this time, the selector valve
43
is brought to a normal state assuming the position that can supply the hydraulic fluid to the merge/separation valve
40
. In this state, when the second operation valve
15
is operated to supply the hydraulic fluid to the second hydraulic actuator
16
, the load pressure is produced in the actuator and supplied through the selector valve
43
which is shifted to the position S, and the pressure is supplied to the pressure receiving portion
42
of the merge/separation valve
40
, which is then shifted to the flow separation position H.
The load pressure of the first hydraulic actuator
6
may be used instead of the load pressure of the second hydraulic actuator
16
. Alternatively, the load pressure of the first or second hydraulic actuator, whichever is higher, may be used after they are merged.
In this configuration, when the third hydraulic actuator
21
is driven, the merge/separation valve
40
is shifted to the flow merging position G, so that the hydraulic fluids delivered under pressure from the first and second hydraulic pumps
1
,
11
are merged and supplied to the third hydraulic actuator
21
. When only the first and second hydraulic actuators
6
,
16
are driven, the merge/separation valve
40
assumes the flow separation position H, with the result that the delivery fluid of the first hydraulic pump
1
is supplied to the first hy
Ishizaki Naoki
Kataoka Toyomi
Yoshida Nobumi
Komatsu Ltd.
Lopez F. Daniel
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Hydraulic fluid supply system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic fluid supply system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic fluid supply system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2461345