Power plants – Pressure fluid source and motor – Having condition responsive control in a system of...
Reexamination Certificate
2001-03-29
2003-07-22
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of...
C060S486000, C137S625170
Reexamination Certificate
active
06594992
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a rotary servo valve that carries out flow rate control and pressure control in the hydraulic circuit of each industrial machinery and punch press liquid operated servo system using the same valve.
BACKGROUND ART
To the liquid operated servo system in conventional technological field of hydraulic control type machine tools and industrial machinery, directly driven type servo valves or electromagnetic proportional control servo valves, and other control valves are popularly used.
For example, in hydraulically driven punch presses, the elevating stroke of hydraulic cylinder ram is controlled in four patterns of quick approach stroke, low-speed punching stroke, high-speed descending stroke at the time of chip shaking off, and quick return stroke in order to achieve low noise and low vibration.
In order to control the strokes of the above-mentioned four patterns, as depicted in the hydraulic circuit shown in
FIG. 1
, a high pressure hydraulic pump
207
and low pressure hydraulic pump
209
are installed via the suction filter
205
from the oil tank
203
in order to operate the hydraulic cylinder
201
. The high pressure pipe conduit
211
and the low pressure pipe conduit
213
on the discharge ends of the high pressure hydraulic pump
207
and the low pressure hydraulic pump
209
are connected to high-low pressure selector valve
215
, and the discharge end of this high-low pressure selector valve
215
is connected to the upper oil chamber
219
and the lower oil chamber
221
of the hydraulic cylinder
201
via the upper-lower selector valve
217
.
In the midway of the high-pressure pipe conduit
211
and the low-pressure pipe conduit
213
, high-pressure accumulator
223
, low-pressure accumulator
225
, and other control valves are installed.
In the above-mentioned hydraulic circuit, low-pressure high-flow rate hydraulic fluid is controlled to be supplied to the hydraulic cylinder
201
in the quick approach, quick return, and chip shake-off strokes, and the high-pressure small-flow rate hydraulic fluid to be supplied in the punching stroke.
Now, in the above-mentioned conventional control system, a high-low pressure selector valve
215
is required for changing over high and low hydraulic pressures to operate the hydraulic cylinder
201
, and the upper-lower selector valve
217
is required for changing over the top and the bottom of the hydraulic cylinder
201
. In this way, one or more control valves are required for one circuit, and the circuit increases the complexity. Consequently, there is a problem in that the particularly subtle control is difficult.
In addition, a space for installing a plurality of valves
215
,
217
is required, causing a problem of preventing size reduction of the system, and an increase of valves
215
,
217
tends to increase the risk of oil leak, and causes a problem of energy loss.
Furthermore, hydraulic piping and electrical wiring for operating valves
215
,
217
are required, respectively, causing a problem of increased complexity of the system.
The hydraulic manifold to which the two servo valves (
215
,
217
) are installed requires a hydraulic circuit of two systems of high pressure and low pressure and a two-way circuit of rise and descend, making the hydraulic manifold circuit extremely complicated and resulting in a large profile, interfering the system from reducing the size.
In the directly operated servo valve or electromagnetic proportional servo valve, a method for detecting displacement of the built-in spool with a differential transformer and feeding back of the detected result to the spool displacement instruction signals is used. However, because the differential transformer adopts a detection principle using coils, the detection displacement is shifted (temperature is drifted) by the ambient air temperature, and detection errors are generated, making it difficult to achieve high-accuracy spool position control.
Because in the valve manufacturing process, there is an individual difference between processing sizes of the valve main body and the spool of the servo valve, a difference is generated in the opening initiation position of the hydraulic fluid supply port as well as the relation between the spool displacement rate and the supply flow rate, and in the conventional liquid operated servo system with two servo valves combined, there is a problem of different flow rate characteristics for each servo system. In addition, when two servo valves are combined, the oil passage connecting the two servo valves becomes long and the response speed of the valve to the control instructions becomes slow.
DISCLOSURE OF THE INVENTION
Accordingly, the present invention has been made to solve the problems as described above, and it is an object of the present invention to provide a compact and high-accuracy rotary servo valve equipped with both supply fluid selector capabilities and the flow rate control capabilities as well as the punch press liquid operated servo system using the said valve.
To achieve the above object, a rotary servo valve according to the first aspect comprises a valve main body provided with a plurality of intake ports for taking in a plurality of pressure fluids which have pressures different to one another and a plurality of supply ports for supplying a plurality of pressure fluids taken in to the desired drives; a spool which is installed free to reciprocate along a sliding groove formed in the valve main body while being free to rotate around the longitudinal direction of the sliding groove and which allows one of the plurality of intake ports to selectively communicate with one of the plurality of supply ports; reciprocatedly moving mechanisms for reciprocating the spool along the sliding groove without rotating; and rotating mechanisms for rotating the spool along the sliding groove without reciprocating.
The rotary servo valve according to the second aspect is a rotary servo valve according to the first aspect, wherein the plurality of intake ports includes a high-pressure opening for taking in high-pressure fluid and a low-pressure opening for taking in low-pressure fluid, and the plurality of supply ports includes a descent port for supplying pressure fluid to the upper chamber of the cylinder operated by the pressure fluid and a rise port for supplying pressure fluid to the lower chamber of the cylinder.
The rotary servo valve according to the third aspect is a rotary servo valve according to the first aspect, wherein one of the plurality of intake ports is selected by the reciprocating motion of the spool and one of the plurality of supply ports is selected by the rotating motion of the spool.
The rotary servo valve according to the fourth aspect is a rotary servo valve according to the first aspect, wherein one of the plurality of supply ports is selected by the reciprocating motion of the spool and one of the plurality of intake ports is selected by the rotating motion of the spool.
The rotary servo valve according to the fifth aspect is a rotary servo valve according to the first aspect, further comprising a means for detecting a rotation angle of the spool.
The rotary servo valve according to the sixth aspect is a rotary servo valve according to the fifth aspect, wherein the means for detecting the rotation angle is a rotary encoder.
To achieve the above object, a punch press hydraulic servo system according to the seventh aspect comprises a plurality of pressure sources for supplying a plurality of pressure fluids with pressures different from one another; a punch press hydraulic cylinder; a valve main body provided with a plurality of intake ports for taking in a plurality of pressure fluids and a plurality of supply ports for supplying the plurality of pressure fluids taken in to an upper chamber or a lower chamber of a hydraulic cylinder; a spool which is installed free to reciprocate along a sliding groove equipped to the valve main body while being free to rotate around the longitudinal direction of the sliding groove and which allows one o
Hara Hideo
Naito Kinshiro
Shimizu Masayuki
Takahashi Osamu
Amada Engineering Center Company, Limited
Blank Rome LLP
Lazo Thomas E.
Look Edward K.
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