BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to an ultra-high pressure generator obtaining ultra-high
pressure output by plungers which are reciprocatively driven by hydraulic pressure
or the like.
Description of the Related Arts
[0003] An ultra-high pressure pump that discharges a jet of high pressure fluid has been
known to have the following configuration (see FIG. 1 in Japanese Patent Application
Publication number
S63-39799). An open-circuit hydraulic pump (working medium pump) 1 is connected, at a discharging
side, to low pressure cylinder chambers C1 and C2 in an intensifier 2 via a two-way
control valve (directional control valve) 3. When the directional control valve 3
is at the position V1, hydraulic oil (working medium) boosted by the hydraulic pump
1 is supplied to the cylinder chamber C1 and the working medium in the cylinder chamber
C2 is returned to a tank 25. At this time, the piston P in the intensifier 2 is moved
toward the right direction in FIG. 1. When the piston P in the intensifier 2 reaches
the right end, the directional control valve 3 is switched to the position V2. The
pressurized working medium is supplied to the cylinder chamber C2 and the working
medium in the cylinder chamber C1 is returned to the tank 25. At this time, the piston
P in the intensifier 2 is moved toward the left direction in FIG. 1. When the piston
P in the intensifier 2 reaches the left end, the directional control valve 3 is switched
to the position V1. The pressure of the pressurized fluid is pressurized by a factor
of an intensify ratio in the pressure of the working medium. The pressure of the pressurized
fluid is controlled by the relief valve 27 controlling the pressure of the working
medium.
SUMMARY OF THE INVENTION
[0004] The aforementioned high pressure generator with the open-circuit hydraulic pump and
the directional control valve has the following problem.
[0005] In a cutting application by water jet, the high pressure generator discharges the
pressurized fluid continuously. At the time of discharging the jet from the high pressure
generator, the hydraulic pressure generator is driven to have high pressure loss in
the directional control valve. When the discharge of the fluid under high pressure
is stopped, a double-acting drive cylinder is stopped, which makes the pressure loss
of the hydraulic oil as the fluid under low pressure become zero. The amount of the
pressure loss in the directional control valve appears as a temporary abnormal rise
of hydraulic pressure of the hydraulic oil. The temporary abnormal rise of hydraulic
pressure of the hydraulic oil affects the discharge pressure of the fluid under high
pressure according to the intensify ratio of the intensifier. Here, the intensify
ratio is a pressure ratio between the pressure of the pressurized fluid under high
pressure and the pressure of the hydraulic oil under low pressure, and is normally
set as several tens of times. That is, when the continuous discharge of the fluid
under high pressure is stopped, the pressure rises temporarily by the pressure amount
of several tens of times of the pressure loss in the directional control valve. Therefore,
when the continuous discharge is stopped, the pressure rises excessively.
[0006] In the cutting application by water jet, pulsation in a high pressure circuit occurs
when the double-acting intensifier switches directions. If the directional control
valve is increased in size with the aim of reducing the pressure loss thereof, responsiveness
of the directional control valve deteriorates. At the stroke ends of the intensifier,
the pressurized fluid is not supplied from a pressure process in the cylinder to a
downstream side of a check valve. Then, the pressurized fluid is not supplied till
a travel direction in the intensifier is switched, causing the pressure to drop. This
pressure drop is determined by the switching time of the travel direction in the intensifier,
the volume of an accumulator and the discharge amount. If the responsiveness of the
working fluid deteriorates, a pressure waveform of the pressurized fluid is disturbed.
The jet of the pressurized fluid, that is, the flow rate of the water jet depends
on the pressure. Therefore, the deterioration of responsiveness in the working fluid
circuit causes quality of the jet water to degrade.
[0007] In the high pressure generator including a double-acting intensifier driven by the
open-circuit hydraulic pump, the directional control valve for the hydraulic pressure
generator is mandatory. However, the pressure loss in the directional control valve
causes mechanical efficiency to drop.
[0008] The present invention is intended to provide an ultra-high pressure generator that
reduces fluctuations in a pressure waveform of pressurized fluid and enhances mechanical
efficiency.
[0009] US 4606709A discloses an ultra-high pressure generator according to the preamble of claim 1.
[0010] US 2013/167951 A1 discloses a working medium pump that is driven by a servo motor as a drive source.
[0011] JP 3395122 B2 discloses a high pressure fluid discharge device having a driving pressure source
that includes a hydraulic oil tank and first and second working medium passages connected
to a control valve.
[0012] In view of the problem above, the invention provides an ultra-high pressure generator
for generating pressure over 600 MPa, including: an intensifier that discharges pressurized
fluid and includes a double-acting drive cylinder formed to have a first chamber and
a second chamber which are delimited by a piston that is driven by a working medium,
a high pressure cylinder that discharges the pressurized fluid, and a plunger that
reciprocates with the piston in the high pressure cylinder; a closed-circuit working
medium pump that has a first port and a second port as suction/discharge ports for
the working medium, and sucks/discharges the working medium from/to the first chamber
and the second chamber respectively via the first port and the second port to drive
the intensifier; a drive source that drives the closed-circuit working medium pump;
a first working medium channel that communicates the first chamber with the first
port; and a second working medium channel that communicates the second chamber with
the second port; characterized in that the ultra-high pressure generator further comprises:
a working medium tank that stores the working medium, said working medium tank being
applied with an internal pressure and being adapted to regulate the total amount of
the working medium; a supply circuit that is provided between the first working medium
channel and the second working medium channel, and that communicates with the working
medium tank; a selection circuit that is provided between the first working medium
channel and the second working medium channel; and a recovery circuit that communicates
the selection circuit with the working medium tank.
[0013] According to the configuration of the ultra-high pressure generator, the closed-circuit
working medium pump is used to suck the working medium from a pressurized side in
the intensifier, pressurize it, and to return it to a pressing side in the intensifier,
which does not require a directional control valve that controls flow directions of
the working medium to be supplied to the first or second chamber. Therefore, the problem
can be addressed that pressure of the high pressure fluid or the pressurized fluid
increases abnormally at the time of stopping discharge due to the pressure loss in
the directional control valve.
[0014] That is, according to at least preferred embodiments of the present invention, in
a case where the pressurized fluid is discharged continuously, when the flow direction
of the closed-circuit working medium pump is reversed, the pressure in either one
of the first and second chambers becomes approximately 0 MPa, and the other one is
pressurized immediately. Further, since the pressure of the working medium becomes
zero temporarily when the travel direction of the piston in the double-acting drive
cylinder is switched, the pressure does not increase abnormally at the time of switching
the travel direction. With these effects, a stable pressure waveform can be obtained
which has little pressure fluctuations of the high pressure fluid.
[0015] Still further, according to the ultra-high pressure generator having the configuration
above, since the working medium filled in the double-acting drive cylinder of the
intensifier is directly driven by the closed-circuit working medium pump, high response
speed of the intensifier can be achieved. Thus, the pressure waveform of the pressurized
fluid can be stable.
[0016] Therefore, a stable jet can be obtained when a water jet is discharged by an ultra-high
pressure generator in accordance with embodiments of the present invention.
[0017] The working medium is filled in the first or second chamber of the double-acting
drive cylinder. When the direction of the intensifier is switched, either one of the
first and second chambers which has been pressurized is changed to a supply side,
and the other one that has been a supply side is pressurized. In at least preferred
embodiments, at the time of switching the directions of the intensifier, a bidirectionally
rotatable drive source is reversely rotated against inertial force of the closed-circuit
pressurizing device to suck the working fluid from a supplying chamber. At this time,
since the pressurized fluid that has been pressurized in the high pressure cylinder
is expanded based on compression rate of the pressurized fluid to push back the piston,
a load on the drive system can be reduced.
[0018] In embodiments of the present invention, the closed-circuit working medium pump is
preferably a fixed-displacement swash plate axial pump and the drive source is preferably
a bidirectionally rotatable drive source.
[0019] According to the ultra-high pressure generator having the configuration above, reliability
of the closed-circuit working medium pump is improved.
[0020] In certain embodiments in accordance with the present invention, the closed-circuit
working medium pump may be a variable-displacement swash plate axial pump that can
reverse a tilt angle between positive and negative directions . With such a configuration,
a unidirectionally rotatable drive source can be applied as a drive source.
[0021] In embodiments of the present invention, the drive source can preferably be a servo
motor, and the ultra-high pressure generator can comprise a pressure detector that
detects pressure of the pressurized fluid discharged from the intensifier and a controller
that controls the number of rotations of the servo motor in response to the pressure
detected by the pressure detector.
[0022] According to the ultra-high pressure generator having the configuration above, the
flow rate and the pressure of the closed-circuit working medium pump is controlled
in response to the pressure of the pressurized fluid detected by the pressure detector.
Since proper pressure of the working medium can be generated by the closed-circuit
working medium pump when the ultra-high pressure generator is driven, the pressure
waveform of the pressurized fluid is stabilized.
[0023] According to the configuration above, since the ultra-high pressure generator in
accordance with such embodiments of the present invention does not need to include
a relief circuit for regulating the pressure of the working medium, the thermal loss
of the relief circuit does not exist, thereby increasing the mechanical efficiency.
Further, since the thermal loss of the relief circuit does not need to be recovered,
the amount of cooling water can be significantly reduced.
[0024] In a case where the ultra-high pressure generator is used as a continuous discharge
high pressure generator, when the discharge of the pressurized fluid is stopped, the
servo motor continues to rotate so that the closed-circuit working medium pump keeps
the pressure.
[0025] The ultra-high pressure generator in accordance with embodiments of the present invention
preferably includes a storage tank in which the pressurized fluid is stored, a supply
port through which the pressurized fluid is supplied to the storage tank, and a heat
exchanger that cools the working medium, wherein the pressurized fluid supplied through
the supply port is supplied to the storage tank via the heat exchanger.
[0026] According to the configuration as described above, since a cooling medium that cools
the working medium is reused as the pressurized fluid, the amount of the pressurized
fluid needed for the ultra-high pressure generator can be reduced.
[0027] Thus, the ultra-high pressure generator according to at least preferred embodiments
of the present invention can reduce the fluctuations in the pressure waveform of the
pressurized fluid and can improve the mechanical efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Embodiments of the invention will now be described, by way of example only, with
reference to the accompanying drawings, in which:
FIG. 1 is a diagram showing a hydraulic pressure circuit of an ultra-high pressure
generator according to an embodiment of the present invention; and
FIG. 2 is a chart showing a pressure waveform of fluid under high pressure in the
ultra-high pressure generator according to the illustrated embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Referring to FIG. 1, an ultra-high pressure generator 70 in an embodiment of the
present invention will be described. A working medium F1 is hydraulic oil and pressurized
fluid F2 is water, in the ultra-high pressure generator 70. The ultra-high pressure
generator 70 is preferably used for water jet cutting in which ultra-high pressure
water is discharged continuously.
[0030] The ultra-high pressure generator 70 of the present embodiment is a device that continuously
discharges the pressurized fluid F2 under ultra-high pressure. The ultra-high pressure
generator 70 includes: an intensifier 40 having a double-acting drive cylinder 44
formed to have a first chamber 41 and a second chamber 42 which are delimited by a
piston 43 driven by the working medium F1, and plungers 461, 462 which reciprocate
with the piston 43 in high pressure cylinders 451, 452 respectively; a closed-circuit
working medium pump 11 having a first port 111 and a second port 112 as suction/discharge
ports; a bidirectionally rotatable drive source 12 that drives the closed-circuit
working medium pump 11; a first working medium channel 32 that communicates the first
chamber 41 with the first port 111; and a second working medium channel 33 that communicates
the second chamber 42 with the second port 112.
[0031] The closed-circuit working medium pump 11 is a fixed-displacement swash plate axial
pump and a drive source thereof is constituted with a servo motor as a bidirectionally
rotatable drive source 12.
[0032] The ultra-high pressure generator 70 further includes a pressure detector 53 that
measures the pressure of the pressurized fluid F2 discharged from the intensifier
40 and a controller 15 that controls the number of rotations of the bidirectionally
rotatable drive source 12 in response to the pressure detected by the pressure detector
53.
[0033] The ultra-high pressure generator 70 includes a supply port 68 through which the
pressurized fluid F2 is supplied, a heat exchanger 30 that cools the working medium
F1 and a storage tank 69 in which the pressurized fluid F2 is stored. The pressurized
fluid F2 supplied from the supply port 68 flows through the heat exchanger 30 into
the storage tank 69.
[0034] The intensify ratio is determined to be ratio of the cross-sectional area of the
piston 43 to cross-sectional areas of the high pressure cylinders 451, 452. The pressure
of the pressurized fluid F2 is pressurized by a factor of the intensify ratio based
on the pressure of the working medium F1. The boost pressure is set to be several
tens of times. The plungers 461, 462 in the intensifier 40 are caused to reciprocate
from side to side by the double-acting drive cylinder 44 in the high pressure cylinders
451, 452. A pair of suction valve 48 and discharge valve 47 is arranged at the ends
of the high pressure cylinders 451, 452, respectively. When the working medium F1
flows into the first chamber 41, the piston 43 in the double-acting drive cylinder
44 moves toward the right direction in FIG. 1. At this time, the pressurized fluid
F2 flows into the high pressure cylinder 451 through the suction valve 48. Besides,
the pressurized fluid F2 is discharged from the high pressure cylinder 452 through
the discharge valve 47. When the piston 43 moves toward the right direction (right
side) in FIG. 1 to reach around the right end, a right end detector 492 detects the
piston 43 to switch a travel direction of the piston 43 toward the left direction
in FIG. 1. When the piston 43 is moved toward the left direction (left side) in FIG.
1, the double-acting drive cylinder 44 acts reversely as described above. Likewise,
a left end detector 491 detects that the piston 43 has reached around the left end.
The reciprocation of the double-acting drive cylinder 44 allows the pressurized fluid
F2 to be discharged continuously.
[0035] It is noted that detectors such as proximity switches, limit switches may be used
as the left end detector 491 and right end detector 492. When the proximity switches
are used, respective detectors 491, 492 can be installed in the intensifier 40, resulting
in a simple structure.
[0036] It is also noted that the suction valves 48 and discharge valves 47 are check valves,
but a directional flow regulation valve may be used in place of the pair of check
valves. In addition, if a one-shot ultra-high pressure generator is used which is
not the continuous discharge type, the discharge valves 47 is unnecessary.
[0037] The closed-circuit working medium pump 11 is a fixed-displacement swash plate axial
pump. The first port 111 is directly connected to the first chamber 41 via the first
working medium channel 32, and the second port 112 is directly connected to the second
chamber 42 via the second working medium channel 33. That is, when the piston 43 in
the intensifier 40 moves toward the right side, the closed-circuit working medium
pump 11 pressurizes the working medium F1 in the second chamber 42 to predetermined
pressure to feed to the first chamber 41. When the piston 43 in the intensifier 40
moves toward the left side, the closed-circuit working medium pump 11 feeds the working
medium F1 in the first chamber 41 to the second chamber 42 reversely. The closed-circuit
working medium pump 11 controls the pressure and the flow rate of the working medium
F1 by controlling the number of rotations thereof. The bidirectionally rotatable drive
source 12 as a servo motor can control the number of rotations as desired to maintain
a rotation angle such that the output shaft thereof does not rotate. Further, the
closed-circuit working medium pump 11 can control the pressure and the flow rate of
the working medium F1 by the use of combination of the fixed-displacement swash plate
axial pump and the bidirectionally rotatable servo motor, and can set the flowing
rate of the working medium F1 to zero while maintaining the pressure of the working
medium F1. Still further, reliability of the ultra-high pressure generator is enhanced
by the use of the fixed-displacement swash plate axial pump.
[0038] It is noted that a variable-displacement axial plunger pump that can reverse a tilt
angle from positive to negative or vice versa and a unidirectionally rotatable drive
source can be used in place of the combination of the closed-circuit working medium
pump 11 and the bidirectionally rotatable drive source 12. The variable-displacement
axial plunger pump capable of reversing a tilt angle can switch a suction side and
a discharge side of two ports by reversing the tilt angle, and can be used as the
closed-circuit working medium pump.
[0039] A circuit for the working medium F1 is arranged in a valve block 20 as shown below.
The valve block 20 is connected to the intensifier 40 and is connected to the closed-circuit
working medium pump 11 with rubber hoses 321, 321, 331, 331 as pipes, respectively.
Connecting respective components with the rubber hoses 321, 321, 331, 331 allows for
absorbing vibrations that may occur at respective components to improve assemblability
and maintainability as well as durability of the ultra-high pressure generator 70.
[0040] The valve block 20 includes a temperature detector 28 that detects temperature of
the working medium. When the temperature of the working medium F1 increases abnormally,
the temperature detector 28 gives a warning. The temperature detector 28 is attached
to the valve block 20 not to contact the working medium F1 directly, and then it is
hard for the temperature detector 28 to suffer damage due to the pressure fluctuations
of the working medium F1 or the like.
[0041] It is noted that the temperature detector 28 can be connected to a supply circuit
21 or a selection circuit 26 when a problem such as breakdown does not need to be
considered.
[0042] The first working medium channel 32 is connected to the second working medium channel
33 with the selection circuit 26 inclusive of a pair of check valves 26a, 26b. The
check valves 26a, 26b are installed to have the working medium channels 32, 33 as
upstream sides. A pressure detector 27 that detects the pressure of the working medium
F1 is arranged in the selection circuit 26. The selection circuit 26 allows the pressure
detector 27 to detect the pressure of either one of the first working medium channel
32 and the second working medium channel 33 which has higher pressure. Thus, the structure
for detecting the pressure can be formed simply. The pressure detector 27 can inform
abnormality when the pressure of the working medium F1 is out of a normal range.
[0043] The first working medium channel 32 is connected to the second working medium channel
33 with the supply circuit 21 that includes a pair of check valves 21a, 21b having
the working medium channels 32, 33 as downstream sides. The supply circuit 21 communicates
the check valves 21a, 21b with a working medium tank 31. The working medium tank 31
is applied with internal pressure . The working medium F1 as hydraulic oil is incompressible
fluid, but is slightly compressed by pressurization. One of the first chamber 41 and
second chamber 42 in the intensifier 40, which is at a supply side, is set to have
pressure around zero MPa normally, and the other is set to have setting pressure.
The total amount of the working medium F1 accumulated in the system is changed depending
on the volume of the working medium F1 presented in either one of the first chamber
41 and second chamber 42, which is at a compression cycle side, and the pipes. The
supply circuit 21 functions to regulate the total amount of the working medium F1.
The working medium tank 31 only needs to have the function to regulate the total amount
of the working medium F1, and therefore can be reduced in size. The working medium
tank 31 is equivalent to a thin-walled gas accumulator to have a radiation function
for the working medium F1.
[0044] A pressure equalization circuit 22 including an electromagnetic valve 22a and a throttle
valve 22b for driving the intensifier 40 connects the first working medium channel
32 with the second working medium channel 33. The electromagnetic valve 22a shuts
off the pressure equalization circuit 22 before the closed-circuit working medium
pump 11 starts operation, and opens the pressure equalization circuit 22 when the
closed-circuit working medium pump 11 stops operation. When the pressure equalization
circuit 22 is open, the pressure of the first working medium channel 32 and the pressure
of the second working medium channel 33 become identical and the intensifier stops
operation. Since the electromagnetic valve 22a is normally open, the electromagnetic
valve 22a opens the pressure equalization circuit 22 to function as a safety circuit
when the power supply is stopped at emergency. The throttle valve 22b prevents the
hydraulic device from receiving impact pressure to be damaged due to abrupt pressure
change when the pressure equalization circuit 22 opens. Further, if the total amount
of the working medium F1 in the system is large, the pressure of the working medium
F1 may fluctuate due to switching of the electromagnetic valve 22a. However, since
the total amount of the working medium F1 in the present embodiment is small, large
pressure fluctuations do not occur, and then the throttle valve 22b is not necessarily
required.
[0045] It is noted that, if some other device is arranged to secure safety, the pressure
equalization circuit 22 is not necessarily required.
[0046] A recovery circuit 34 communicates the selection circuit 26 with the working medium
tank 31. In the recovery circuit 34, a safety valve 25 is connected in parallel with
a flow regulation valve 24, and a filter 29 and a heat exchanger 30 are connected
with these elements in series. If control in the servo system of the closed-circuit
working medium pump 11 runs away, the safety valve 25 functions to maintain the pressure
of the working medium F1 less than or equal to a setting value. This function of the
safety valve 25 prevents the pressure of the ultra-high pressure generator 70 from
increasing abruptly. The flow regulation valve 24 controls the amount of the highly
pressurized working medium F1 that is recovered from the selection circuit 26 to the
working medium tank 31 via the recovery circuit 34. As mentioned above, the working
medium tank 31 regulates the amount of the working medium F1 in the system according
to the reciprocation of the piston 43 in the intensifier 40. The recovery circuit
34 functions to supply the necessary working medium F1 to the working medium tank
31. When recovered into the working medium tank 31, the working medium F1 is filtered
by the filter 29 and cooled by the heat exchanger 30. As mentioned above, according
to the switching of the travel directions of the piston 43 in the intensifier 40,
the working medium F1 is supplied from the working medium tank 31 via the supply circuit
21 and is returned from the selection circuit 26 to the working medium tank 31. Thus,
a constant amount of the working medium F1 flows in the circuits via the working medium
tank 31 according to the operation of the intensifier 40. Therefore, the working medium
F1 is always cooled by the heat exchanger 30 and the temperature thereof is kept constant.
[0047] The working medium F1 recovered via the recovery circuit 34 is a leak of the working
medium F1 boosted by the closed-circuit working medium pump 11. Since the flow regulation
valve 24 is arranged in the recovery circuit 34 for the leak that deteriorates the
mechanical efficiency, the leak amount can be regulated properly to prevent the mechanical
efficiency from being deteriorated excessively.
[0048] In addition, the flow regulation valve 24 is arranged in the recovery circuit 34,
allowing for setting the flow rate of the working medium F1 flowing into the heat
exchanger 30 to a predetermined amount. In the ultra-high pressure generator 70, a
cooling medium of the heat exchanger 30 is the pressurized fluid F2. Since all the
pressurized fluid F2 is flown through the heat exchanger 30, heat quantity recovered
by the heat exchanger 30 may become too large. However, by throttling the flow rate
of the working medium F1 having higher temperature which is flowed through the heat
exchanger 30, the recovered heat quantity can be controlled.
[0049] It is noted, in a case where some other safety measure is taken against the abnormal
pressure increase, the safety valve 25 may be eliminated. In a case where the heat
quantity generated in the system is small and the working medium F1 can be cooled
sufficiently by outside air, the heat exchanger 30 is unnecessary.
[0050] The pressurized fluid F2 is supplied from the supply port 68 for the pressurized
fluid F2, passes through the heat exchanger 30, is filtered by the filter 67, and
then, is stored in the storage tank 69. The pressurized fluid F2 is supplied into
the storage tank 69 by the use of a ball tap 66, and when the liquid surface in the
storage tank 69 reaches an upper limit, the supply of the pressurized fluid F2 is
stopped.
[0051] It is noted that positions of the filter 67 and the heat exchanger 30 are exchangeable.
[0052] A vortex pump 65 sucks the pressurized fluid F2 from the bottom of the storage tank
69 to supply the pressurized fluid F2 to suction valves 48, 48 in the intensifier
40 through a supply channel 60.
[0053] A safety valve 63 is arranged in the supply channel 60. The safety valve 63 has advantageous
effects of deterring the discharge port of the vortex pump 65 from being closed completely
when discharging of the pressurized fluid F2 is stopped to prevent breakdown of the
vortex pump 65. Further, if the suction valve 48 leaks, the pressurized fluid F2 under
ultra-high pressure flows into the supply channel 60. The safety valve 63 has functions
to prevent the breakdown of the device at the time of this kind of emergency.
[0054] In the supply channel 60, an electromagnetic valve 61 is arranged to supply cooling
water for packing. When the electromagnetic valve 61 is opened, the cooling water
for packing flows through the throttle valve 62 to packing members (not shown) that
seal between the high pressure cylinders 451, 452 and the plungers 461, 462 to cool
the packing members. A pressure switch 64 for detecting supply pressure is arranged
in the supply channel 60. The pressure switch 64 monitors whether the supply pressure
of the pressurized fluid F2 exceeds cracking pressure of the suction valves 48, 48
so that the pressurized fluid F2 is supplied to the intensifier 40. It is noted that
the pressure switch 64 can be replaced by a pressure detector.
[0055] The discharge valves 47, 47 are in communication with a discharge port 55 via an
accumulator 51 through a discharge pipe 56. A filter 52 is arranged in the accumulator
51. Since the filter 52 is arranged in the accumulator 51, the filter 52 receives
ultra-high pressure from inside and outside thereof. A filter for a normal pressure
level can be used as the filter 52.
[0056] The pressurized fluid F2 under ultra-high pressure discharged from the discharge
port 55 is ejected from a nozzle 59 via an on-off valve 58. The pressure detector
53 that detects the pressure of the pressurized fluid F2 under ultra-high pressure
is connected to the discharge pipe 56.
[0057] The controller 15 controls the pressure and the flow rate of the closed-circuit working
medium pump 11, and the travel direction in the intensifier 40 according to the position
of the piston 43 in the intensifier 40 and the pressure of the pressurized fluid F2
that is detected by the pressure detector 53. Pressure feedback is calculated based
on the degree of pressure increase. The modern control having high robustness such
as the adaptive control can be properly used for the pressure control.
[0058] FIG. 2 shows a pressure waveform W1 of the pressurized fluid F2 generated by the
ultra-high pressure generator 70 configured as described above. In FIG. 2, the horizontal
axis indicates elapsed time and the vertical axis indicates pressure. The pressure
and the flow rate of the closed-circuit working medium pump 11 is regulated based
on actual discharge pressure to determine the speed of the plungers 461, 462 properly,
which forms the pressure waveform W1 of the pressurized fluid F2 as an approximately
straight line at a setting pressure P. The pressure is temporarily decreased at constant
time intervals in synchronization with switching the travel directions of the piston
43.
[0059] During the continuous discharge being stopped, the closed-circuit working medium
pump 11 stops rotating, and this rotation status is maintained by the bidirectionally
rotatable drive source 12. Thus, the working medium F1 in the closed-circuit working
medium pump 11 does not flow at the pressuring side. Since the working medium F1 does
not flow, the pressure loss in the first and second working medium channels 32, 33
disappears and the pressure of working medium F1 slightly increases. Since the pressure
of the pressurized fluid F2 that is pressurized under ultra-high pressure becomes
larger than the pressure of the working medium F1 by the factor of the intensify ratio,
the pressure of the pressurized fluid F2 increases (ΔP) by the factor of the intensify
ratio relative to pressure increase of the working medium F1. The number of rotations
of the closed-circuit working medium pump 11 is controlled by the pressure feedback,
thereby minimizing the ΔP. When the continuous discharge is resumed, the pressure
of the pressurized fluid F2 turns back to stable pressure again at around the setting
pressure.
[0060] In an ultra-high pressure generator that generates pressure level of 600 MPa, an
intensify ratio of around 30 times is necessary. The higher the pressure becomes,
the greater the intensify ratio is necessary, and, the greater the intensify ratio
becomes, the greater the rate of the pressure increase becomes when the discharge
is stopped. Further, in a case where the pressure is extremely high, the ultra-high
pressure fluid generates high internal stress in the pressure pipes. The pressure
causes vibration, which greatly limits a material, thickness and inner surface finishing
of the pressure pipes . The pressure increase and pressure vibration of the ultra-high
pressure fluid give excessive stress on the ultra-high pressure generator and the
pressure pipe system.
[0061] The pipe fittings such as pipes, valves, hoses, joints and the like used in the ultra-high
pressure pipes receive excessive internal stress . According to the ultra-high pressure
generator 70 of the present embodiment, the pressure vibration is reduced greatly,
allowing for longer service life of the pipe fittings. Therefore, the ultra-high pressure
generator 70 is suitably adapted to an ultra-high pressure generator that generates
especially high pressure.
[0062] The ultra-high pressure generator 70 of the present embodiment controls the closed-circuit
working medium pump 11 according to the pressure detected by the pressure detector
53, thereby keeping the discharge pressure stably at around the setting pressure P.
The discharge pressure is stable at a constant value, which stabilizes the flow rate
and the flow volume of the jet of the pressurized fluid F2 ejected from the nozzle
59. Further, the pressure waveform is stabilized, allowing the volume of the accumulator
51 to be reduced. The accumulator 51 is a pressure vessel to have high internal stress
generated inside thereof. The internal stress increases in proportion to the square
of the internal diameter of the accumulator. In addition, energy accumulated in the
accumulator is in proportion to the internal volume. Therefore, the ultra-high pressure
generator that generates ultra high pressure over 600 MPa has a very difficult technical
problem in producing an accumulator with large volume. The ultra-high pressure generator
70 has a stable pressure waveform, allowing the accumulator volume to be reduced,
and can suitably be adapted to an ultra-high pressure generator that generates especially
high pressure.
[0063] Since the ultra-high pressure generator 70 includes the plungers 461, 462 and the
high pressure cylinders 451, 452 on both sides of the double-acting drive cylinder
44, the pressure of the pressurized fluid F2 acts upon the piston 43 via the plungers
461, 462 when the travel direction of the piston 43 is switched, where the pressure
of the pressurized fluid F2 is ultra-high pressure in the high pressure cylinders
451, 452 which has been in a compression cycle until right before the switching. At
this time, the pressurized fluid F2 in the high pressure cylinders 451, 452 is expanded
based on the expansion rate thereof . Further, since the working medium F1 is slightly
compressed, the compressed working medium F1 is expanded at the time of switching.
With these actions, when the travel direction of the piston 43 in the intensifier
40 is switched, the working medium F1 that has been pressurized until right before
the switching flows into the closed-circuit working medium pump 11. Although a large
stress is applied to the closed-circuit working medium pump 11 and the bidirectionally
rotatable drive source 12 when the rotational direction is switched, the stress applied
to the closed-circuit working medium pump 11 at this time can be reduced by the actions
described above.
[0064] Since the ultra-high pressure generator 70 does not include the relief valve 27 and
the directional control valve 3 (see FIG. 1 in Japanese Patent Application Publication
number
S63-39799) in the related art, the mechanical efficiency thereof is improved. The improvement
of the mechanical efficiency reduces waste heat generated from the ultra-high pressure
generator 70. Therefore, the amount of cooling water for cooling the working medium
F1 can be reduced greatly. Since the necessary amount of cooling water is small, the
ultra-high pressure generator 70 can match the discharge amount of the pressurized
fluid F2 with the amount of cooling water and can temporarily use the supplied pressurized
fluid F2 as the cooling water. Still further, since the flow rate of the necessary
pressurized fluid F2 is small, the storage tank 69 can be reduced in size.
[0065] The mechanical efficiency of the ultra-high pressure generator 70 is substantially
improved, which allows the mechanical components constituting the device to be reduced
in size as well as the configuration to be simplified. Thus, the machine can be downsized
as a whole.
[0066] The ultra-high pressure generator 70 according to an embodiment of the present invention
is described above, but the configuration of the present invention is not limited
to the one described above. For example, the bidirectionally rotatable drive source
12 is not limited to a servo motor, but may be a source that can control torque and
the number of rotations, and can keep the rotation.
[0067] Further, an electromagnetic pressure relief valve can be arranged in the recovery
circuit 34 in place of the pressure equalization circuit 22, the electromagnetic valve
22a, the throttle valve 22b, the flow regulation valve 24 and the safety valve 25.
In this case, when the intensifier 40 is stopped operation, the electromagnetic pressure
relief valve is opened to reduce the pressure in the working medium channels 32, 33.
When the intensifier 40 resumes operation, the electromagnetic pressure relief valve
is closed.
[0068] The ultra-high pressure generator 70 according to the illustrated embodiment of the
present invention can be applied to a pressure/fatigue breakdown testing device, a
hydroforming device, not limited to a water jet application.
1. Ultrahochdruckgenerator (70) zum Erzeugen von Druck über 600 MPa, umfassend:
einen Druckübersetzer (40), der unter Druck stehendes Fluid (F2) ausstößt und einen
doppeltwirkenden Antriebszylinder (44) einschließt, der so ausgebildet ist, dass er
eine erste Kammer (41) und eine zweite Kammer (42) aufweist, die durch einen von einem
Arbeitsmedium (F1) angetriebenen Kolben (43) begrenzt sind, einen Hochdruckzylinder
(451, 452), der das unter Druck stehende Fluid (F2) ausstößt, und einen Tauchkolben
(461, 462), der sich mit dem Kolben (43) in dem Hochdruckzylinder (451, 452) hin-
und her bewegt;
eine Arbeitsmediumpumpe (11) mit geschlossenem Kreislauf, die einen ersten Anschluss
(111) und einen zweiten Anschluss (112) als Ansaug-/Ausstoßanschlüsse für das Arbeitsmedium
(F1) aufweist und das Arbeitsmedium über den ersten Anschluss (111) und den zweiten
Anschluss (112) aus der ersten Kammer (41) bzw. der zweiten Kammer (42) ansaugt/ausstößt,
um den Druckübersetzer (40) anzutreiben;
eine Antriebsquelle (12), die die Arbeitsmediumpumpe (11) mit geschlossenem Kreislauf
antreibt;
einen ersten Arbeitsmediumkanal (32), der die erste Kammer (41) mit dem ersten Anschluss
(111) verbindet; und
einen zweiten Arbeitsmediumkanal (33), der die zweite Kammer (42) mit dem zweiten
Anschluss (112) verbindet;
dadurch gekennzeichnet, dass der Ultrahochdruckgenerator (70) weiter umfasst:
einen Arbeitsmediumtank (31), der das Arbeitsmedium (F1) speichert, wobei der Arbeitsmediumtank
(31) mit einem Innendruck beaufschlagt wird und geeignet ist, die Gesamtmenge des
Arbeitsmediums (F1) zu regulieren;
einen Versorgungskreislauf (21), der zwischen dem ersten Arbeitsmediumkanal (32) und
dem zweiten Arbeitsmediumkanal (33) bereitgestellt ist und der mit dem Arbeitsmediumtank
(31) verbunden ist;
einen Auswahlkreislauf (26), der zwischen dem ersten Arbeitsmediumkanal (32) und dem
zweiten Arbeitsmediumkanal (33) bereitgestellt ist; und
einen Rückgewinnungskreislauf (34), der den Auswahlkreislauf (26) mit dem Arbeitsmediumtank
(31) verbindet.
2. Ultrahochdruckgenerator (70) nach Anspruch 1, wobei die Arbeitsmediumpumpe (111) mit
geschlossenem Kreislauf eine Axialkolben-Konstantpumpe in Schrägscheibenbauart ist
und die Antriebsquelle (12) eine bidirektional drehbare Antriebsquelle ist.
3. Ultrahochdruckgenerator (70) nach Anspruch 1, wobei die Arbeitsmediumpumpe (11) mit
geschlossenem Kreislauf eine Axialkolben-Verstellpumpe in Schrägscheibenbauart ist,
die einen Neigungswinkel zwischen positiver und negativer Richtung umkehren kann.
4. Ultrahochdruckgenerator (70) nach einem der Ansprüche 1 bis 3, wobei die Antriebsquelle
(12) ein Servomotor ist und der Ultrahochdruckgenerator (70) weiter umfasst: einen
Druckdetektor (53), der den Druck des unter Druck stehenden Fluids (F2) detektiert,
das aus dem Druckübersetzer (40) ausgestoßen wird; und eine Steuerung (15), die die
Anzahl der Umdrehungen des Servomotors als Reaktion auf den von dem Druckdetektor
(53) detektierten Druck steuert.
5. Ultrahochdruckgenerator (70) nach einem der Ansprüche 1 bis 4, wobei der Ultrahochdruckgenerator
(70) weiter umfasst: einen Speichertank (69), in dem das unter Druck stehende Fluid
(F2) gespeichert wird; einen Versorgungsanschluss (68), durch den das unter Druck
stehende Fluid an den Speichertank (69) zugeführt wird; und einen Wärmetauscher (30),
der das Arbeitsmedium (F1) kühlt, und wobei das unter Druck stehende Fluid (F2), das
durch den Versorgungsanschluss (68) zugeführt wird, über den Wärmetauscher (30) an
den Speichertank (69) zugeführt wird.