Power plants – Pressure fluid source and motor – Condition responsive control of pump or motor displacement
Reexamination Certificate
1999-04-02
2001-04-03
Ryznic, John E. (Department: 3745)
Power plants
Pressure fluid source and motor
Condition responsive control of pump or motor displacement
C060S486000, C060S484000
Reexamination Certificate
active
06209322
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pressurized fluid supply system for distributing and supplying a discharged pressurized fluid of a hydraulic pump to a plurality of actuators.
BACKGROUND ART
When a discharged pressurized fluid is supplied simultaneously to a plurality of actuators having different magnitudes of loads, the pressurized fluid is supplied only to the actuator having the minimum load and the pressurized fluid is not supplied to other actuators.
Therefore, as shown in
FIG. 1
, there has been known a system, in which a plurality of throttle portions, such as a first operating valve
2
and a second operating valve
3
are provided in a discharge passage
1
a
of a hydraulic pump
1
for simultaneously supplying a pressurized fluid to a plurality of actuators, such as a first actuator
4
and a second actuator
5
by controlling open degrees of the first and second operating valves
2
and
3
depending upon magnitudes of loads.
On the other hand, as shown in
FIG. 2
, there has been known a system, in which pressure compensation valves
6
are provided on the circuits connecting the first and second operating valves
2
and
3
and the first and second actuators
4
and
5
respectively, and a higher pressure between a load pressure of the first actuator
4
and a load pressure of the second actuator
5
is detected by a shuttle valve
7
to supply the detected pressure to pressure receiving portions
6
a
of the pressure compensation valves
6
.
In the system illustrated in
FIG. 2
, the pressure compensation valves
6
are set for the highest load pressure. Therefore, the pressurized fluid can be supplied to the first and second actuators
4
and
5
with a flow rate distribution ratio depending upon opening degrees of the first and second operating valves
2
and
3
.
In case of the foregoing pressurized fluid supply system shown in
FIG. 1
, if the load of the first actuator
4
is high and the load of the second actuator
5
is low when simultaneously supplying the pressurized fluid to the first actuator
4
and the second actuator
5
, in order to set the pump pressure P
0
of the hydraulic pump
1
at a pressure P
1
of the first actuator
4
having aa higher load, the opening degree of the second operating valve
3
is reduced to lower the output pressure of the second operating valve
3
to be lower than the pump pressure P
0
to be set at the pressure P
2
of the second actuator
5
.
Therefore, the discharged pressurized fluid of the hydraulic pump
1
causes a significant pressure loss (P
0
−P
2
) when passing through the second operating valve
3
and thus a substantial energy loss is caused. For example, a horse power loss of an engine
8
for driving the hydraulic pump
1
will be large.
On the other hand, in a system for controlling a displacement of the hydraulic pump
1
(a flow rate of the discharged fluid per one revolution) depending on the pump pressure P
0
to control the horse power, for instance, a system for controlling pump pressure P
0
×displacement to be constant, the pressure P
1
of the first actuator
4
having a high load will be the pump pressure P
0
to make the displacement small and the flow rate of the discharged fluid of the hydraulic pump small. Thus, a speed of the first actuator
4
will be low.
For example, when P
1
=100 kg/cm
2
and P
2
=50 kg/cm
2
, the pump pressure P
0
becomes 100 kg/cm
2
. Then, when a flow rate Q
1
to the first actuator
4
is 1 and a flow rate Q
2
to the second actuator
5
is 2, a displacement Q
1
+Q
2
of the hydraulic pump
1
becomes 3. Therefore, when pump pressure P
0
×displacement is controlled to be constant, 100 kg/cm
2
×3 is constant. Thus, the higher the pump pressure P
0
becomes, the smaller the displacement becomes.
On the other hand, in the pressurized fluid supply system, as shown in
FIG. 2
, set fort above, the discharged pressure fluid of the hydraulic pump
1
causes a pressure loss by passing through the operating valve and the pressure compensation valve to cause a significant energy loss to make it impossible to effectively use the discharged pressurized fluid of the hydraulic pump
1
.
Therefore, the present invention has an object to provide a pressurized fluid supply system which can solve the problem set forth above.
DISCLOSURE OF THE INVENTION
The first invention is a pressurized fluid supply system mechanically connecting a plurality of variable displacement type hydraulic pump/motors to rotate at the same revolution speed and to supply a discharged pressurized fluid of a hydraulic pump
11
to actuators through the respective variable displacement type hydraulic pump/motors.
According to the first invention, a flow rate ratio to be supplied to a plurality of actuators is a displacement ratio between the variable displacement type hydraulic pump/motors irrespective of loads of the actuators.
Therefore, by varying the displacements of a plurality of variable displacement type hydraulic pump/motors, the discharged pressurized fluid of the hydraulic pump can be supplied to a plurality of actuators with an arbitrary flow rate distribution ratio. Furthermore, for a reduction of the pressure loss, the energy loss becomes smaller.
Further, since the discharged pressure (pump pressure) of the hydraulic pump becomes an average value of load pressures of a plurality of actuators, the displacement of the hydraulic pump becomes greater to make the speed of the actuator high, in case of a horse power control system controlling the displacement of the hydraulic pump depending upon the pump pressure.
The second invention is a pressurized fluid supply system providing a variable displacement type hydraulic pump/motor and an operating valve in each circuit connecting a discharge passage
12
of a hydraulic pump
11
and each of a plurality of actuators, and mechanically connecting the variable displacement type hydraulic pump/motors to rotate at the same revolution speed, and
providing displacement control means for adjusting displacements of the variable displacement type hydraulic pump/motors at values inversely proportional to a pressure ratio between the actuators each connected to the corresponding variable displacement type hydraulic pump/motor.
According to the second invention, since the displacements of the variable displacement type hydraulic pump/motors can be controlled automatically depending upon the pressure ratio between the actuators, the operation will be simple.
The third invention is a pressurized fluid supply system providing a variable displacement type hydraulic pump/motor and an operating valve in each circuit connecting a discharge passage
12
of a hydraulic pump
11
and each of a plurality of actuators, and mechanically connecting the variable displacement type hydraulic pump/motors to rotate at the same revolution speed, and
providing means for detecting an open degree of each of the operating valves respectively and displacement control means for adjusting displacements of the variable displacement type hydraulic pump/motors at values each corresponding to the open degree of the operating valve connected to the corresponding variable displacement type hydraulic pump/motor.
According to the third invention, the displacement of each variable displacement type hydraulic pump/motor becomes a value depending upon open the degree of each operating valve. Therefore, the discharged pressurized fluid of the hydraulic pump/motors can be supplied to the plurality of actuators depending upon open degrees of the operating valves irrespective of the load pressures.
On the other hand, since the discharged pressurized fluid of the hydraulic pump causes little pressure loss when passing through the variable displacement type hydraulic pump/motor, energy loss is small to permit an effective use of the discharged pressurized fluid of the hydraulic pump.
REFERENCES:
patent: 3572460 (1971-03-01), Berlich
patent: 3964261 (1976-06-01), Zukauskas
patent: 4123907 (1978-11-01), Bianchetta et al.
patent: 4237688 (1980-12
Endo Hiroshi
Ishizaki Naoki
Maruta Kazuhiro
Yoshida Nobumi
Armstrong, Westerman Hattori, McLeland & Naughton
Komatsu Ltd.
Ryznic John E.
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