High-pressure Generation Device

Abstract

The high-pressure generation device (110) comprises three pressure chambers which pressurize liquid drawn from the outside through the pumping operation of a plurality of pistons (1) having different outer diameters, pressurizes the liquid drawn from the outside, and discharges the liquid pressurized to a constant pressure to the outside in each reciprocating operation of the plurality of pistons (1). The three pressure chambers comprising a first pressure chamber (31) which draws liquid from the outside, a second pressure chamber (32) of which the pressurizing area for pressurizing the liquid is smaller than that of the first pressure chamber (31), and a third pressure chamber (33) of which the pressurizing area is smaller than that of the second pressure chamber (32) and which discharges liquid to the outside. The pressurizing areas of the second pressure chamber (32) and the third pressure chamber (33) are set so that the ratio of the difference between the pressurizing areas of the second pressure chamber (32) and the third pressure chamber (33) to the thrust when the plurality of pistons move in the one direction is equal to the ratio of the pressurizing area of the third pressure chamber (33) to the thrust when the plurality of pistons move in the other direction.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a high-pressure generation device which draws in fluid and discharges it at high pressure.

BACKGROUND OF THE INVENTION

[0002] A piston pump (also referred to as a "plunger pump") has been used to discharge pressurized liquid at high pressure. The piston pump reciprocates a liquid drawing/compressing piston using an external power source, compresses the liquid drawn in from the outside, and discharges the pressurized liquid at high pressure. Various types of drive units for reciprocating the drawing/compressing piston are available, such as one which converts the rotary motion of a motor or engine as the power source into a reciprocal motion and one which reciprocates a control piston by feeding pressurized fluid as the power source into a fluid pressure cylinder (See Japanese Patent No. 3297143).

[0003] In order to discharge liquid at high pressure, a piston pump is required to discharge fluid which has been subject to draw/compression strokes in order to be pressurized to a predetermined pressure. Piston pumps which bring about less pulsatory motion in liquid to be discharged employ, in most cases, a method that uses a plurality of pistons and a method that uses an accumulator, both of which lead to complicated structures, issues with upsizing, and high costs in most cases.

[0004] A pressure conversion device which uses a single compressor is, however, disclosed which is provided with two pressure chambers for performing compression/discharge processes outside of a piston which reciprocates by using a fluid pressure cylinder, draws hydraulic oil from the outside into the first chamber when the piston moves in one direction, pressurizes the hydraulic oil up to a predetermined pressure when the piston moves in the other direction, sends the pressurized hydraulic oil from the first chamber having a larger compressed volume into the second chamber having a smaller expanded volume, and at the same time, also discharges the hydraulic oil to the outside (See Japanese Examined Patent Application Publication No. 62-21994).

[0005] In this pressure conversion device, however, when the hydraulic oil is pressurized by the first pressure chamber, mixed air is also required to be compressed and the need to reduce compression time to the greatest extent possible remains unsatisfied. In addition, a flow passage for the hydraulic fluid for reciprocating the control piston of a drive unit is switched by two directional control valves in a two-stage manner, resulting in a problem in that it takes time to actually perform switching.

[0006] A compressor has been proposed which performs threefold compression in order to obtain high pressure gas efficiently using a single compressor (See Japanese Unexamined Patent Application Publication No 3-9088).

[0007] This technique obtains high pressure gas by compressing the gas in a three-stage manner, but there are difficulties in applying it directly to liquid because of its structure. In addition, since it discharges only gas once for each reciprocating operation of a piston, even if it is applied to liquid, the pressure fluctuation of the liquid being discharged is large, and the demand to eliminate pulsation cannot be satisfied.

[0008] The inventors of the present application have proposed a high-pressure generation device including three pressurizing chambers within a piston, in which, when the piston actuated by a drive unit moves in one direction, liquid is drawn from the outside into first chamber through an inlet port, high-pressure fluid is fed from the reducing second chamber into the expanding third chamber, and residual high-pressure fluid is discharged to the outside, and when the piston moves in the other direction, the fluid is pressurized by the reducing first chamber and the expanding second chamber, and the high-pressure fluid is discharged to the outside from the reducing third chamber (See Japanese Unexamined Patent Application Publication No. 2003-3966). They have obtained a US patent for the above-detailed invention (See U.S. Pat. No. 7,165,951 B2).

[0009] In this high-pressure generation device, however, as shown in FIG. 9, the three chambers are inside the H-shaped piston, making its structure complicated and the number of components large. In addition, since high-precision concentricity and perpendicularity are required for the components, component processing is extremely difficult, and it is difficult to avoid processing errors caused by chucking. Furthermore, since the flow passage communicating the first chamber and the second chamber is provided within the piston, and a backflow prevention valve is required to be provided at this position, it is difficult to downsize the piston, thereby providing an obstacle to the downsizing of the high-pressure generation device.

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0010] The present invention has been achieved in view of the above-described problems. It is an object of the present invention to provide a high-pressure generation device which is relatively simple in structure, is easy to process components for, can discharge high-pressure liquid continuously from the beginning of operation, can discharge high-pressure liquid with small pressure fluctuations continuously, and can be downsized.

Means for Solving the Problems

[0011] The high-pressure generation device of the present invention is a high pressure generation device which includes a plurality of reciprocating pistons which are coaxially connected to a reciprocating drive shaft of a drive unit and have different outer diameters and three pressure chambers which pressurize liquid drawn from the outside through the pumping operation of the plurality of pistons, pressurizes liquid drawn from the outside, and discharges liquid pressurized to a predetermined pressure to the outside in each reciprocating operation of the plurality of pistons, wherein the three pressure chambers comprising a first pressure chamber for drawing liquid from the outside, a second pressure chamber wherein the pressurizing area for pressurizing liquid is smaller than that of the first pressure chamber, and a third pressure chamber wherein the pressurizing area is smaller than that of the second pressure chamber and which discharges liquid to the outside, and the pressurizing areas of the second pressure chamber and the third pressure chamber are set so that the ratio of the difference between the pressurizing areas of the second pressure chamber and the third pressure chamber to the thrust when the plurality of pistons move in one direction is equal to the ratio of the pressurizing area of the third pressure chamber to the thrust when the plurality of pistons move in the other direction, or the direction opposite to the one direction.

[0012] The three pressure chambers are thus formed through the pumping operation of a plurality of reciprocating pistons which are coaxially connected to the drive shaft, and all three pressure chambers are outside the pistons, providing a simple structure with fewer components in comparison to the inventions disclosed in Japanese Unexamined Patent Application Publication No. 2003-3966 and U.S. Pat. No. 7,165,951 B2. By having fewer parts into which the pistons are fitted to slide, the high-pressure generation device can be installed in a processing machine in a one-chuck state and can be processed relatively easily. Since the pressurizing areas of the second pressure chamber and the third pressure chamber are set so that the ratio of the difference between the pressurizing areas of the second pressure chamber and the third pressure chamber to the thrust when the plurality of pistons move in one direction is equal to the ratio of the pressurizing area of the third pressure chamber to the thrust when the plurality of pistons move in the other direction, or the direction opposite to the one direction, liquid drawn from the outside is pressurized to a predetermined pressure by any of the reciprocating operations of the pistons while it is sent from the first pressure chamber to the second pressure chamber, and from the second pressure chamber to the third pressure chamber. When the third pressure chamber expands, the liquid pressurized to a predetermined pressure by the second pressure chamber fills the third pressure chamber, and at the same time, the residual liquid with the predetermined pressure is directly discharged from the third pressure chamber to the outside. When the third pressure chamber reduces, the liquid in the third pressure chamber is pressurized in order to be discharged to the outside. Liquid with a predetermined pressure can thereby be discharged to the outside at all times.

[0013] In particular, the above-described high-pressure generation device, wherein the drive shaft is reciprocated by a drive unit having a rotating shaft, and the pressurizing area of the second pressure chamber is set to be twice as large as the pressurizing area of the third pressure chamber, can also discharge liquid with a predetermined pressure to the outside at all times.

[0014] In addition, when the above-described high-pressure generation device includes an auxiliary chamber which communicates with the first pressure chamber or the second pressure chamber, wherein the volume of the auxiliary chamber is capable of being adjusted, the liquid pressurizing area can be finely adjusted, even when gas is mixed into the liquid to be pressurized by a plurality of pistons.

[0015] The above-described high-pressure generation device preferably includes: an intake port for drawing liquid from the outside; a first flow passage allowing the liquid drawn from the intake port to flow into the first pressure chamber; a second flow passage allowing the liquid pressurized by the first pressure chamber to flow into the second pressure chamber; a third flow passage allowing the liquid pressurized to a predetermined pressure by the second pressure chamber to flow into the third pressure chamber; and an outlet port for discharging the liquid pressurized to a constant pressure from the third pressure chamber to the outside, wherein each of the first flow passage, the second flow passage, and the third flow passage is provided with a backflow prevention device thereby allowing liquid to flow only in a predetermined direction.

[0016] By providing such backflow prevention devices, liquid can be successively sent from the first pressure chamber to the second pressure chamber, from the second pressure chamber to the third pressure chamber, and from the third pressure chamber to the outlet port, allowing the liquid pressurized to a constant pressure to be discharged from the outlet port.

[0017] Any of the first flow passage, the second flow passage, and the third flow passage is preferably formed outside the plurality of pistons. In another preferred embodiment, the third pressure chamber is formed at the tip of a piston of which the outer diameter is the smallest out of the plurality of pistons, the third flow passage may be formed either within or outside of the plurality of pistons, and both the first flow passage and second flow passage are formed outside of the plurality of pistons.

[0018] Providing the flow passages outside the pistons in this way allows the pistons to be downsized and allows the high-pressure generation device to be easily downsized.

[0019] Furthermore, in another preferred embodiment, the drive unit is provided with a switching device which reciprocates the drive shaft by reversing the direction of the liquid which flows into/out of each of both side chambers of the reciprocating control piston, wherein the switching device is provided with a rod which moves by using the control piston approaching each side end of both side chambers and reverses the direction of the liquid by the movement of the rod.

[0020] Providing the switching device means that high-speed switching can be performed stably, thereby allowing liquid to be discharged from the outlet port with a specific pressure at all times.

[0021] In yet another preferred embodiment, the plurality of pistons are connected to both sides of the drive shaft, while the first pressure chamber and the second pressure chamber are formed at the tip of the pistons.

[0022] Arranging the first pressure chamber and the second pressure chamber in this way simplifies the manufacturing of the high-pressure generation device.

Effect of the Invention

[0023] According to the high-pressure generation device of the present invention, since all three pressure chambers are outside the pistons, a simple structure with few components is provided, and it can be mounted on a processing machine with one chuck and processed relatively easily. In addition, since the flow passage connecting the two pressure chambers is provided within the housing located outside the pistons, it is possible to downsize the device. Successive pressurization by the three pressure chambers can discharge liquid with a predetermined pressure from the beginning of operation. Furthermore, the thrust and speed of the reciprocating motion by the drive unit are made constant, thereby allowing liquid with a constant pressure to be discharged continuously at all times and this also allows liquid with a constant quantity to be discharged continuously at all times.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a cross-sectional view showing one example of the high pressure generation device in accordance with one embodiment of the present invention.

[0025] FIG. 2 is a cross-sectional view showing one example of the high pressure generation device in accordance with one embodiment of the present invention.

[0026] FIG. 3 is a schematic cross-sectional view for illustrating the operation of the high pressure generation device in accordance with one embodiment of the present invention.

[0027] FIG. 4 is a schematic cross-sectional view for illustrating the operation of the high pressure generation device in accordance with one embodiment of the present invention.

[0028] FIG. 5 is a schematic cross-sectional view for illustrating the operation of the high pressure generation device in accordance with one embodiment of the present invention.

[0029] FIG. 6 is a schematic cross-sectional view for illustrating the operation of the high pressure generation device in accordance with one embodiment of the present invention.

[0030] FIG. 7 is a schematic cross-sectional view for illustrating the operation of the high pressure generation device in accordance with one embodiment of the present invention.

[0031] FIG. 8 is a schematic cross-sectional view for illustrating the operation of the high pressure generation device in accordance with one embodiment of the present invention.

[0032] FIG. 9 is a cross-sectional view showing an embodiment of a high pressure generation device in accordance with a previously-filed patent application.

[0033] FIG. 10 is a cross-sectional view partially enlarging the high pressure generation device in accordance with one embodiment of the present invention.

[0034] FIG. 11 is a diagram showing an example of an actuator in which an eccentric heart-shaped cam is integral with a rotating drive shaft.

[0035] FIG. 12 is a diagram showing an example of a crank mechanism as an actuator in which an eccentric shaft 55 is rotated by a rotating drive shaft.

[0036] FIG. 13 is an example of a configuration using a double-rod fluid pressure cylinder as an actuator.

[0037] FIG. 14 is an example using an automatic switching device for switching a directional control valve of a fluid pressure cylinder at high speed as an actuator.

[0038] FIG. 15 is an example of the high-pressure generation device of the present invention in which a piston and a plunger are arranged to the left and right with an actuator sandwiched therebetween.

[0039] FIG. 16 is another example of the high-pressure generation device of the present invention in which a piston and a plunger are arranged to the left and right with an actuator sandwiched therebetween.

[0040] FIG. 17 is an example of one configuration of the high-pressure generation device of the present invention which reciprocates a piston and a plunger with a drive unit in which an eccentric cam or bearing is integral with a rotating drive shaft arranged midway therebetween.

[0041] FIG. 18 is another example of the high-pressure generation device of the present invention in which a piston and a plunger are arranged to the left and right with an actuator sandwiched therebetween.

[0042] FIG. 19 is another example of the high-pressure generation device of the present invention in which a piston and a plunger are arranged to the left and right with an actuator sandwiched therebetween.

[0043] FIG. 20 is an example of a configuration in which the drive unit shown in FIG. 17 is arranged midway therebetween unlike that of the actuator shown in the configuration examples of the high-pressure generation device of the present invention shown in FIG. 18 and FIG. 19.

[0044] FIG. 21 is an example of the high-pressure generation device of the present invention in which the second pressure chamber and the third pressure chamber are provided in both side chambers of the piston part 8.

[0045] FIG. 22 is a graph showing a waveform (theoretical values) of the discharge pressure Pd of the high-pressure generation device in accordance with a preferred embodiment of the present invention.

[0046] FIG. 23 is a graph showing a waveform (theoretical values) of the discharge pressure P of the pressure conversion device including two pressurizing chambers disclosed in Japanese Examined Patent Application Publication No. 62-21994 as a comparative example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] Hereinafter, the high-pressure generation device of the embodiments provided in accordance with the present invention will be described with reference to the drawings.

[0048] FIG. 1 and FIG. 2 are cross-sectional views showing examples of the high pressure generation device in accordance with one embodiment of the present invention.

[0049] As shown in FIG. 1 and FIG. 2, the high pressure generation device 110 in accordance with one embodiment of the present invention is provided with three pressure chambers, that is, a first pressure chamber 31, a second pressure chamber 32, and a third pressure chamber 33 for performing a pumping operation to pressurize and discharge liquid in a space in which a piston 1 fitted into a housing 2 reciprocates, an intake port 257 for drawing the liquid from the outside into the first pressure chamber 31, a first flow passage 254 for communicating the intake port 257 and the first pressure chamber 31, a second flow passage 311 for communicating the first pressure chamber 31 and the second pressure chamber 32, a third flow passage 271 for connecting the second pressure chamber 32 and the third pressure chamber 33, and an outlet port 267 for discharging the liquid pressurized to a predetermined pressure from the third pressure chamber 33 to the outside. The first flow passage 254 is provided with a check valve 81 (which is equivalent to the backflow prevention device in accordance with the present invention) for allowing the liquid to flow from the intake port 257 into the first pressure chamber 31 and to prevent it from flowing backwards. The second flow passage 311 is provided with a check valve 82 for allowing the pressurized liquid to flow from the first pressure chamber 31 into the second pressure chamber 32 and prevent it from flowing backwards. The third flow passage 271 is provided with a check valve 83 for allowing the pressurized liquid to flow from the second pressure chamber 32 into the third pressure chamber 33 and prevent it from flowing backwards. Each of the check valves 81, 82, and 83 in accordance with the present embodiment comprising a ball 812 and a spring 813. When a predetermined pressure difference between both sides of the flow passage occurs, the spring 813 is pressed by the ball 812 and contracts, thereby opening the valve, and when a pressure difference between both sides of the flow passage occurs, the valve closes to prevent the liquid from flowing backwards. However, it should be appreciated that the check valves are not necessarily limited to this particular structure.

[0050] The first flow passage 254 and the second flow passage 311 in accordance with the present embodiment are provided within the housing 2, while the third flow passage 271 is provided within the piston 1, but the third flow passage 271 is not necessarily provided within the piston 1 and may be provided within the housing 2 in the same manner as the first flow passage 254 and the second flow passage 311. The first flow passage 254 and the second flow passage 311 are thus provided outside the piston 1, thereby allowing the piston 1 to be downsized. In addition, the piston 1 can be downsized further by providing the third flow passage 271 outside the piston 1, thereby allowing the high-pressure generation device 110 to be downsized.

[0051] The high-pressure generation device 110 in accordance with the present invention is provided with a large-diameter piston part 8, a piston rod 7 of which the outer diameter is smaller than that of the piston 8, and a piston part 9 of which the outer diameter is smaller than that of the piston rod 7, which are coaxially connected to both sides of the large-diameter piston part 8. Within the housing, a large-diameter cylinder 8a into which the large-diameter piston part 8 is fitted is provided. A small-diameter cylinder 9b into which the small-diameter piston part 9 is fitted is provided at the center of one end face of the large-diameter cylinder 8a, while a through hole 7a into which the piston rod 7 is fitted is provided at the center of the other end face of the large-diameter cylinder 8a.

[0052] Outside of the piston 1, the large-diameter piston part 8 is fitted into the large-diameter cylinder 8a, while the small-diameter piston part 9 is fitted into the small-diameter cylinder 9b. In the space in which the large-diameter piston part 8 and the small-diameter piston part 9 reciprocate, the first pressure chamber 31 having the largest liquid pressurizing area, the second pressure chamber 32 of which the liquid pressurizing area is smaller than that of the first pressure chamber, and the third pressure chamber 33 of which the liquid pressurizing area is smaller than that of the second pressure chamber are formed.

[0053] As shown in FIG. 1, when the piston 1 moves in the one direction (the left direction shown by the arrow in the figure), the first pressure chamber 31 increases in volume, the pressure within the first pressure chamber 31 then becomes lower than the pressure of the outside liquid F, opening the check valve 81. The liquid F is then drawn from the intake port 257 into the first pressure chamber 31. The second pressure chamber 32, meanwhile, decreases in volume, and the pressure within the second pressure chamber 32 then becomes higher, closing the check valve 82 and opening the check valve 83. The high-pressure liquid pressurized by the second pressure chamber 32 is then fed into the third pressure chamber 33, and out of the fed high-pressure liquid, the remaining liquid, after filling the third pressure chamber 33, is discharged from the outlet port 267.

[0054] As shown in FIG. 2, when the piston 1 moves in the other direction (the right direction shown by the arrow in the figure), the first pressure chamber 31 decreases in volume, and the pressure within the first pressure chamber 31 then becomes higher, closing the check valve 81. The second pressure chamber 32, meanwhile, increases in volume, and the pressure within the second pressure chamber 32 then becomes lower, opening the check valve 82. The third pressure chamber 33 decreases in volume and the pressure within the third pressure chamber 33 then becomes higher, closing the check valve 83. The high-pressure liquid pressurized by the third pressure chamber 33 is then discharged from the outlet port 267.

[0055] Thus, the liquid drawn from the intake port 257 is pressurized by the first pressure chamber 31, the second pressure chamber 32, and the third pressure chamber 33 through the movement of the piston 1 in one direction and then the other direction, allowing the liquid to be discharged at all times at a constant pressure.

[0056] The high-pressure generation device 110 in accordance with the present embodiment is provided with an auxiliary chamber 52 which communicates with the second pressure chamber 32.

[0057] FIG. 10 is a cross-sectional view partially enlarging the high pressure generation device in accordance with the present embodiment. As shown in FIG. 10, a cylindrical hole 53 is formed at the position of the housing 2 which communicates with the second pressure chamber. An adjust screw 54 provided with an outer screw is screwed into the cylindrical hole 53. The space in the cylindrical hole 53 on the tip side of the adjust screw 54 is the auxiliary chamber 52. A jam nut 93 is threadably engaged with the part of the adjust screw 54 which protrudes from the housing 2. Packing 51 is installed in a packing installation groove on the periphery of the adjust screw 54, preventing the liquid from leaking out of the auxiliary chamber. The cylindrical hole 53 can be moved forward or backward by rotating the adjust screw 54, allowing the volume of the auxiliary chamber 52 to increase or decrease.

[0058] Pressure to be generated in the first pressure chamber 31 and the second pressure chamber 32 is determined by the ratio of the total volume obtained by adding the volumes of the first pressure chamber 31, the second pressure chamber 32, the auxiliary chamber 52, part of the first flow passage 254, part of the second flow passage 311, and part of the third flow passage 271 to the volume difference between the reduced volume and the expanded volume in the first pressure chamber 31 and the second pressure chamber 32. By increasing the volume of the auxiliary chamber 52 by rotating the adjust screw 54, the pressure to be generated decreases, while, by decreasing the volume thereof, the pressure to be generated increases. For liquid, since pressure also depends on the amount of air incorporated therein and any temperature difference, by increasing/decreasing the volume of the auxiliary chamber 52, pressure to be generated can be set at a predetermined value.

[0059] The operation of the high-pressure generation device 110 in accordance with the present embodiment will now be described in more detail.

[0060] FIGS. 3 to 8 are schematic cross-sectional views for illustrating the operation of the high pressure generation device in accordance with one embodiment of the present invention.

[0061] FIG. 3 shows a state in which the piston 1 of the high-pressure generation device in accordance with one embodiment of the present invention has started moving in the other direction (the right direction shown by the arrow in the figure), FIG. 4 shows the moment the piston 1 has stopped, and FIG. 5 shows the state in which the piston 1 has started moving in the one direction (the left direction shown by the arrow in the figure).

[0062] As shown in FIG. 3, when the piston 1 moves in the right direction shown by the arrow, the first pressure chamber 31 is pressurized, and the check valve 81 closes, but the second pressure chamber 32 expands, and its pressure becomes lower than that of the first pressure chamber 31, thereby opening the check valve 82. Letting the reduced volume (the compressed volume) of the pressurized first pressure chamber 31 be .DELTA.V.sub.1, and letting the expanded volume of the second pressure chamber 32 be .DELTA.V.sub.2, when the piston moves in the right direction, the total volume (.DELTA.V.sub.1+.DELTA.V.sub.2) changes and is pressurized. In accordance with a change in the total volume (.DELTA.V.sub.1+.DELTA.V.sub.2), the pressure in the first pressure chamber 31 and the second pressure chamber 32 is increased.

[0063] The third pressure chamber 33, meanwhile, is reduced through the movement of the piston 1 in the right direction, and high-pressure liquid pressurized to a predetermined pressure Pd is discharged from the outlet port 267.

[0064] Since a reduction in the volume of the first pressure chamber 31 .DELTA.V.sub.1 is set to be larger than an expansion in the volume of the second pressure chamber 32 .DELTA.V.sub.2, when the piston moves in the other direction (the right direction shown by the arrow in the figure), the pressure in the second pressure chamber 32 approaches the predetermined pressure Pd, and immediately before the piston 1 reverses to the backward direction, the pressure in the second pressure chamber 32 becomes equal to Pd, or is pressurized to substantially the same value through the fine movement of the small-diameter piston part 9.

[0065] The difference between an outer diameter D3 of the small-diameter piston part 9 forming the first pressure chamber 31 and an outer diameter D2 of the piston rod 7 forming the second pressure chamber 32 is determined in accordance with the discharge pressure Pd of the high-pressure liquid discharged from the third pressure chamber 33, and in order to increase the discharge pressure Pd, D2 is required to be increased.

[0066] Now, when the liquid to be pressurized (compressed) is water at 20.degree. C., the compressibility ratio .beta. is 0.428.times.10.sup.-9 m.sup.2/N in the pressure range from 1.01325.times.10.sup.5 Pa to 500.times.1.01325.times.10.sup.5 Pa. Since liquid has, in general, a low compressibility ratio .beta., by compressing it only slightly, its pressure increases. In fact, since air mixes thereinto in many cases, care should be taken in that the compressibility ratio decreases in accordance with the air mixing ratio.

[0067] In the position shown in FIG. 3 through to nearly that shown in FIG. 4, a constant pressure acts on a first control chamber 36 by a working fluid L, and when thrust is added to the piston 1, the third pressure chamber 33 thereby discharges liquid at the constant discharge pressure Pd. In this case, when the thrust of an actuator 6 is consumed through a gradual increase in the pressure in both the first pressure chamber 31 and the second pressure chamber 32 by the volume difference between a reduction in the volume of the first pressure chamber 31 and an expansion in the volume of the second pressure chamber 32, the pressure Pd of the liquid discharged from the third pressure chamber 33 will decrease, albeit slightly. However, when the. actuator 6 holds the remaining thrust power, the pressure Pd of the liquid discharged from the third pressure chamber 33 will not decrease and as such, balance is achieved by an increase in the thrust of the actuator 6.

[0068] FIG. 4 shows the moment when a directional control valve 60 (not shown) of the actuator 6 is switched to move the piston 1 in the backward direction (the left direction) when the piston 1 reaches the end of the working space. The piston 1 stops instantaneously and the pressure of the liquid in the second pressure chamber 32 is increased up to a pressure corresponding to the predetermined discharge pressure Pd.

[0069] FIG. 5 shows a state in which the piston 1 which has reversed and is moving in one direction (the left direction). The second pressure chamber 32 is pressurized, closing the check valve 82 and opening the check valve 83. The liquid which has been pressurized to the pressure Pd by the second pressure chamber 32 and has been discharged fills the third pressure chamber 33, and the residual liquid is discharged from the outlet port 267. The first pressure chamber 31 is expanded and its pressure decreases, allowing the check valve 81 to open and liquid F to flow into the intake port 257 from the outside. This state continues while the piston 1 is moving in the one direction (the left direction).

[0070] FIG. 6 shows a state in which the piston 1 has started moving in the one direction (the left direction shown by the arrow in the figure), FIG. 7 shows the moment the piston 1 has stopped, and FIG. 8 shows the state in which the piston 1 has started moving in the other direction (the right direction shown by the arrow in the figure).

[0071] FIG. 6 shows a state in which the piston 1 has moved in the left direction slightly, and the check valves 81, 82, and 83 maintain the same states as those shown in FIG. 5.

[0072] FIG. 7 shows the moment when the directional control valve 60 (not shown) of the actuator 6 is switched to move the piston 1 in the backward direction (the right direction), when the piston 1 reaches the end of the working space, and the piston 1 stops instantaneously. The third pressure chamber 33 is filled with liquid pressurized to the discharge pressure Pd or some pressure close thereto.

[0073] FIG. 8 shows the same state as FIG. 3. While the piston 1 moves, the liquid in the third pressure chamber 33 is pressurized, allowing the high-pressure liquid to be discharged from the outlet port 267.

[0074] As described above, the piston 1 moves from FIG. 3 to FIG. 8 to form one cycle, during which the liquid pressurized to Pd continues to be discharged from the outlet port 267.

[0075] In the high-pressure generation device 110 in accordance with the present embodiment, a single-rod fluid pressure cylinder is used as the actuator 6, and a control piston rod 46 of the actuator 6 is connected to the piston rod 7 on one side of the piston 1, allowing the piston 1 to reciprocate at a constant speed.

[0076] The actuator 6 for use in the high pressure generation device 110 in accordance with the present embodiment has a structure for preventing working fluid L from leaking to the outside by allowing a head cover 44 and a rod cover 45 to be fitted into a cylinder tube 47 in order to close the cylinder tube 47 and provides packing 48 at the fitting part of the rod cover 45 and the head cover 44. Packing 49 is provided on a control piston 43 which is fitted into the cylinder tube 47 where it will reciprocate, while sealing packing 50 is provided at a part which is fitted into the rod cover 45 on the outer periphery of the piston rod 46, which is integrally coupled to the control piston 43. The rod cover 45 is fixed to the housing 2 by screwing a bolt 4 into the housing 2 from outside the head cover 44. The working space in which the control piston 43 moves is formed with a first control chamber 35 and a second control chamber 36. The head cover 44 and the rod cover 45 are provided with a first control port 221 and a second control port 222 for feeding the working fluid L to the first control chamber 35 or the second control chamber 36 and discharging the working fluid L from the first control chamber 35 or the second control chamber 36, and are provided with a directional control valve 60 for switching between feeding the working fluid L to either one of the first control port 221 or the second control port 222 and discharging the working fluid L from either one of them, flow passages 62 and 61 between the directional control valve 60 and the control ports 221 and 222, a flow passage 63 for sending the working fluid L from a pressure source P to the directional control valve 60, and a flow passage 64 for sending the working fluid L from the directional control valve 60 to a drain tank D.

[0077] By switching the flow passages 61 and 62 for the working fluid L fed from the pressure source P using the directional control valve 60, working surfaces 112 and 122 of the control piston 43 are switched to move in either direction, allowing the piston rod 46 to reciprocate.

[0078] In FIG. 1, since the directional control valve 60 is switched to a flow passage state 601, the working fluid L enters the first control port 221 from the flow passage 61 and acts on the working surface 112 of the first control chamber 35, allowing a drive mode for moving the piston 1 in the one direction (the left direction shown by the arrow in the figure) to be established. The flow passage 62, meanwhile, communicates with the drain tank D through the flow passage 64, collecting the working fluid L in the second control chamber 36.

[0079] In FIG. 2, since the directional control valve 60 is switched to a flow passage state 602, the working fluid L enters the second control port 222 from the flow passage 62 and acts on the working surface 122 of the second control chamber 36, allowing a drive mode for moving the piston 1 in the other direction (the right direction shown by the arrow in the figure) to be established. The working fluid L in the first control chamber 35, conversely, is collected into the drain tank D.

[0080] In the single-rod cylinder having one control piston 43, since the pressure-receiving surface areas of the working surfaces 112 and 122 of the control piston 43 which receive the working fluid L are different from each other, the outer diameter of the control piston 43 and the outer diameter of the piston rod 46 are, as will be described later, defined by the relationship with the pressure-receiving surface areas when the liquid F acts on the second pressure chamber and the third pressure chamber formed on both sides of the large-diameter piston part 8 of the piston 1.

[0081] An example of the high-pressure generation device using the single-rod fluid pressure cylinder as the actuator 6 will be described here, but the actuator 6 is not necessarily a single-rod fluid pressure cylinder, and may instead be a double-rod fluid pressure cylinder and a motor or an engine having a rotating shaft as the power source. An embodiment with an actuator having a rotating shaft will be described later.

[0082] In the high-pressure generation device 110 in accordance with the present embodiment, pressure corresponding to the areas of the pressurizing surfaces on which the large-diameter piston part 8 and the small-diameter piston part 9 is generated in the first pressure chamber 31, the second pressure chamber 32, and the third pressure chamber 33, in accordance with the thrust of the actuator 6. The force being in balance with the thrust of the actuator 6 is represented by the product of the area of a pressurizing surface acting on a pressure chamber and the generated pressure.

[0083] In order for the discharge pressure of the liquid when moving in the one direction (the left direction) and the discharge pressure when moving in the other direction (the right direction) to be equal, the area B of the pressurizing surface acting on the second pressure chamber 32 and the area C of the pressurizing surface acting on the third pressure chamber 33 in accordance with the thrust of the drive unit are selected.

[0084] FIG. 10 is a cross-sectional view partially enlarging the high-pressure generation device in accordance with the present embodiment.

[0085] As shown in FIG. 10, the area A of the pressurizing surface of the first pressure chamber 31, the area B of the pressurizing surface of the second pressure chamber 32, and the area C of the pressurizing surface of the third pressure chamber 33 are expressed, using the inner diameter of the cylinder 8a, that is, the outer diameter D1 of the large-diameter piston part, the outer diameter D2 of the piston rod 7, and the outer diameter D3 of the small-diameter piston part 9, as

A=.pi.(D.sub.1.sub.2-D.sub.3.sub.2)/4 B=.pi.(D.sub.1.sub.2-D.sub.2.sub.2)/4 C=.pi.D.sub.3.sub.2/4

[0086] In FIG. 2, the thrust f.sub.1 when the piston 1 is moved in the other direction (the right direction) by the actuator 6 is expressed by the product of the pressure-receiving surface area A.sub.l of the working surface 122 of the control piston 43 of the actuator 6 within the control chamber 36 and the pressure P.sub.36 of the working fluid L acting on the pressure-receiving surface area A.sub.1. At the beginning, the force caused by the pressure P.sub.3 generated in the liquid F within the third pressure chamber 33 balances with the thrust f.sub.1. The force is the product of the area C of the pressurizing surface of the third pressure chamber 33 and the generated pressure P.sub.3, and the generated pressure P.sub.3 is the discharge pressure P.sub.d.

(f.sub.1=)A.sub.1.times.P.sub.36=C.times.P.sub.3

therefore A.sub.1/C=P.sub.3/P.sub.36 Equation (1)

[0087] In fact, however, when the piston 1 moves in the other direction (the right direction), the first pressure chamber 31 reduces to open the check valve 82, and the liquid F flows into the expanded second pressure chamber 32. Since a reduction in the volume of the first pressure chamber 31 is set to be larger than an expansion in the volume of the second pressure chamber 32, the pressure within the first pressure chamber 31 and the second pressure chamber 32 gradually increases with the movement of the piston 1. The thrust f.sub.1 of the actuator 6 is thereby consumed, albeit slightly.

[0088] The discharge pressure P.sub.d of the liquid discharged from the outlet port 267 should therefore gradually decrease, albeit slightly, but in fact, by increasing the pressure P.sub.36 of the control chamber 36 of the actuator 6, the discharge pressure P.sub.d of the liquid does not change.

[0089] The product of the difference between the area A of the pressurizing surface of the first pressure chamber 31 and the area B of the pressurizing surface of the second pressure chamber 32, that is, (A-B), and the generated pressure P.sub.2 is a consumed force when the thrust f.sub.1 of the actuator 6 reaches its maximum.

therefore A.sub.1.times.P.sub.36=(C.times.P.sub.3)-((A-B).times.P.sub.2) Equation (2)

where (A-B).times.P.sub.2 on the right side of Equation (2) gradually increases from zero as the piston 1 moves in the other direction (the right direction), while the discharge pressure P.sub.d decreases, albeit slightly.

[0090] In this regard, fluctuations of the above-described discharge pressure P.sub.d are caused by the load at the place of discharge also. In the case of, for example, discharging with the maximum discharge pressure, the discharge pressure P.sub.d fluctuates.

[0091] In FIG. 1, the thrust f.sub.2 when the piston 1 is moved in the one direction (the left direction) by the actuator 6 is expressed by the product of the pressure-receiving surface area A.sub.2 of the working surface 112 of the control piston 43 of the actuator 6 within the control chamber 35 and the pressure P.sub.35 of the working fluid L acting on the pressure-receiving surface. With respect to the thrust f.sub.2, pressure P.sub.2 is generated in the liquid F within the second pressure chamber 32, the check valve 83 opens due to the pressure P.sub.2, and the pressure P.sub.2 acts on the third pressure chamber 33 in which the force acts in the opposite direction to the second pressure chamber 32, balancing with the thrust f.sub.2. The pressure P.sub.2 is therefore equal to the discharge pressure P.sub.d.

(f.sub.2=)A.sub.2.times.P.sub.35=(B.times.P.sub.2)-(C.times.P.sub.2)

therefore A.sub.2/(B-C)=P.sub.2/P.sub.35 Equation (3)

[0092] Since the pressure P.sub.35 of the working fluid L flowing into the control chamber 35 of the actuator and the pressure P.sub.36 of the working fluid L flowing into the control chamber 36 are equal, in order for the liquid F discharged from the outlet port 267 to have the predetermined pressure P.sub.d at all times, the discharge pressure P.sub.3 when the piston 1 moves in the other direction (the right direction) and the discharge pressure P.sub.2 when the piston 1 moves in the one direction (the left direction) must be equal. From Equation (1) and Equation (3), therefore,

A.sub.1/C=A.sub.2/(B-C) Equation (4)

[0093] Equation (4) forms the foundation to discharge high-pressure liquid with constant pressure using the high-pressure generation device in accordance with the present invention.

[0094] Now, letting the thrust in the other direction and the thrust in the one direction of the actuator 6 be f.sub.1 and f.sub.2, respectively, the relationship between the area B of the pressurizing surface of the second pressure chamber 32 and the area C of the pressurizing surface of the third pressure chamber 33 is expressed as:

f.sub.1/C=f.sub.2/(B-C)

[0095] Therefore, in order for the discharge pressure P.sub.d for both directions (the left direction and the right direction) to be kept constant, it is important that, with respect to a predetermined pressure-receiving surface area ratio (or a thrust ratio) .alpha., the working fluid L of the control piston 43 of the actuator 6 acts on the working surfaces 122 and 112 of the control chambers 36 and 35, the area B of the pressurizing surface of the second pressure chamber 32, and the area C of the pressurizing surface of the third pressure chamber 33 of the piston 1 are selected so that the above-described Equation (4) holds.

[0096] The value described in Equation (4) is the ratio of the pressure P.sub.35 and P.sub.36 of the working fluid L fed to the actuator 6 to the pressure P.sub.d of the liquid F discharged from the outlet port 267 of the high-pressure generation device, and the inverse of that ratio is a pressure-increase ratio.

[0097] The compressibility n % of the liquid when the first pressure chamber 31 and the second pressure chamber 32 communicate with each other is defined by a total volume V.sub.0 before the piston moves in the other direction (the right direction) and a total volume V.sub.1 after it has moved in the other direction (the right direction).

n=(V.sub.0-V.sub.1)/V.sub.0).times.100%

[0098] In other words, the compressibility is influenced by the area A of the pressurizing surface of the first pressure chamber 31 and the difference (A-B) between the area A of the pressurizing surface of the first pressure chamber 31 and the area B of the pressurizing surface of the second pressure chamber 32. However, in addition to the volumes of the first pressure chamber and the second pressure chamber, when the volume of a flow passage is large and when air is mixed into the liquid, the compressibility decreases accordingly. It is therefore preferable that any extra volume, such as that provided by a flow passage, be reduced to the utmost.

[0099] When a fluid pressure cylinder is used as the actuator 6 like the high-pressure generation device 110 in accordance with the present embodiment, it depends on Equation (4), but since when the working fluid L is fed to move a liquid-pressure cylinder, the thrust on the drive side is generally used with a margin, the discharge pressure of the liquid F discharged from the outlet port 267 does not fluctuate, and the pressure of the working fluid L fluctuates. The flows of the liquid F discharged from the outlet port 267 and the working fluid L basically do not change.

[0100] In FIG. 2, the working fluid L flows into the second control chamber 36 forming a side chamber of the control piston 43 of the actuator 6 with a flowrate Q to be acted on the pressure-receiving surface area A.sub.1 of the control piston 43 of the second control chamber 36, thereby allowing the control piston 43 to move in the other direction (the right direction) at a moving speed of v.sub.1. Through this movement, the third pressure chamber 33 is reduced, and by means of the area C of the pressurizing surface of the third pressure chamber 33, the high-pressure liquid F is discharged from the outlet port 267 with a flowrate of q.sub.1. This relationship is expressed by the following Equation:

Q=A.sub.1.times.v.sub.1 v.sub.1=q.sub.1/C

therefore Q=A.sub.1.times.q.sub.1/C Equation (5)

[0101] In FIG. 1, the working fluid L flows into the first control chamber 35 acting as a side chamber of the control piston 43 of the actuator 6 with a flowrate Q to be acted on the pressure-receiving surface area A.sub.2 of the control piston 43 of the first control chamber 35, thereby allowing the control piston 43 to move in the one direction (the left direction) at a moving speed of v.sub.2. Through this movement, the second pressure chamber 32 is reduced, and by means of the area B of the pressurizing surface of the second pressure chamber 32, the high-pressure liquid F flows into the expanding third pressure chamber 33, and the residual high-pressure liquid F, after filling the third pressure chamber 33, is discharged from the outlet port 267 with a flowrate of q.sub.2. This relationship is expressed by the following Equation:

Q=A.sub.2.times.v.sub.2 v.sub.2=q.sub.2/(B-C)

therefore Q=A.sub.2=q.sub.2/(B-C) Equation (6)

[0102] From the above-described Equations (5) and (6),

(A.sub.1/C).times.q.sub.1=(A.sub.2/(B-C)).times.q.sub.2 Equation (7)

[0103] In order for the flowrate q.sub.1 discharged from the outlet port 267 when the piston is moved in the other direction (the right direction) and the flowrate q.sub.2 discharged when it is moved in the one direction (the left direction) to be equal, from Equation (7),

A.sub.1/C=A.sub.2/(B-C) Equation (4)

[0104] This equation is the same as the above-described Equation (4).

[0105] This means therefore that when the discharge pressure P.sub.d of the liquid discharged from the outlet port 267 when the piston moves in the other direction (the right direction) and when it moves in the one direction (the left direction) are equal, an equal discharge flow is provided at the same time.

[0106] When the thrust in the other direction (the right direction) and the thrust in the one direction (the left direction) imparted by the actuator 6 are equal, or for example, when the pressure-receiving surface area A.sub.1 of the first control chamber 35 and the pressure-receiving surface area A.sub.2 of the second control chamber 36 of the control piston 43 of the actuator 6 are equal, from Equation (4),

C=B-C (since A.sub.1=P.sub.36=A.sub.2.times.P.sub.35)

therefore B=2C Equation (8)

[0107] In other words, when the area B of the pressurizing surface of the second pressure chamber 32 is set to be twice as large as the area C of the pressurizing surface of the third pressure chamber 33, the liquid F with a constant discharge pressure Pd can be discharged from the outlet port 267 continuously with a constant flow.

[0108] When the piston performing the pumping operation is reciprocated by a motor or engine having a rotating shaft, the liquid F with a constant discharge pressure Pd can be discharged from the outlet port 267 continuously, provided that Equation (8) is fulfilled.

[0109] FIG. 11 is a diagram showing an example of an actuator in which an eccentric heart-shaped cam is integral with a rotating drive shaft.

[0110] FIG. 11 shows an example of the high-pressure generation device 610, in which, as an actuator, a heart-shaped cam 76b is integral with a rotating drive shaft 76a, where the heart-shaped cam 76b is sandwiched between recessed extension parts 17a and 17b through ball bearings 17c and 17d, and the extension parts 17a and 17b are connected with the piston rod 7. Using this actuator, the moving speed v.sub.1 and the moving speed v.sub.2 can be equal and constant, thereby allowing the liquid F with a constant pressure Pd to be discharged from the outlet port 267 continuously with a constant flow.

[0111] FIG. 12 is a diagram showing an example of a crank mechanism as an actuator in which an eccentric shaft 55 is rotated by a rotating drive shaft.

[0112] The example shows the high-pressure generation device 640, in which, as an actuator, the eccentric shaft 55 is rotated by the rotating drive shaft 76a and is connected to the piston rod 7 through the crank mechanism 30, 56, and 58. Using this actuator, the liquid F with a constant pressure Pd can be discharged from the outlet port 267 continuously.

[0113] FIG. 13 is an example of a configuration using a double-rod fluid pressure cylinder as an actuator.

[0114] As shown in FIG. 13, a double-rod fluid pressure cylinder is used as the actuator 6 for reciprocating the piston 1.

[0115] The piston rod 46 integral with the control piston 43 is connected with the piston rod 7, while a rod 90 integral with the control piston 43 on the other side is fitted into a circular hole at the center of the head cover 44, protrudes, and reciprocates. A ring 91 which is larger than the outer diameter of the rod 90 is fixed to the protruded part of the rod 90.

[0116] When the working fluid L is fed from the power source P to the first control chamber 35 of the control piston 43 through a solenoid-operated valve 60a acting as a directional control valve, and the other second control chamber 36 communicates with the tank through the solenoid-operated valve 60a, the control piston 43 moves. When the control piston 43 reaches near the end of its stroke, the ring 91 of the rod 90 acts on an electric switch 92b, thereby switching the solenoid-operated valve 60a, allowing the control piston 43 to move in reverse by flow passage switching. Then, when it reaches near the end of its stroke, the ring 91 of the rod 90 acts on an electric switch 92a, thereby switching the solenoid-operated valve 60a, switching between the flow passages 61 and 62. The piston 1 also reciprocates, thereby drawing the liquid F from the intake port 257 and discharging the liquid pressurized at a constant pressure continuously.

[0117] FIG. 14 is an example using an automatic switching device for switching a directional control valve of a fluid pressure cylinder at high speed as an actuator.

[0118] The part surrounded by a two-dot chain line shown in FIG. 14 is the "Pressurized fluid automatic switching device" of Japanese Patent No. 3,650,031 invented by the inventors of the present application, in which valve-pushing rods of pilot valves protrude from both side chambers of the reciprocating control piston 43, and when the control piston reaches the end of its movement, the valve-pushing rods of the pilot valves are pushed in, thereby switching a directional control valve controlling the control piston 43, allowing the piston 1 performing the pumping operation to reciprocate. The high-pressure generation device 410 is required to only feed the working fluid L into a feed port 70 and can provide a highly reliable system without using the above-described actuator and electric switching means.

[0119] Hereinafter, an example of the high-pressure generation device in which a drive unit is arranged midway therebetween with three pressure chambers distributed to the left and right will be provided.

[0120] FIG. 15 and FIG. 16 are examples of the high-pressure generation device in which a piston and a plunger are arranged on the left and right with an actuator sandwiched therebetween.

[0121] As shown in FIG. 15 and FIG. 16, the high-pressure generation device 210a arranges the piston 1 and a plunger 18 with the actuator 6 arranged midway therebetween, provides the first pressure chamber 31 and the second pressure chamber 32 outside the piston 1 within the housing 2, provides the third pressure chamber 33 in the space at the tip of the plunger 18 on the other side, and allows the three pressure chambers 31, 32, and 33 to communicate with each other. The piston 1 and the plunger 18 are driven by the actuator 6 to reciprocate. The actuator 6 including the double-rod fluid pressure cylinder is used as a pulsation-free pump, in which the working fluid L is fed to reciprocate the piston 1 and the plunger 18, thereby drawing the liquid F and discharging the pressurized liquid at a constant pressure continuously.

[0122] The high-pressure generation device 210a is different from the above-described high-pressure generation devices 110, 610, 410, 640 and 810 only in the position for providing the second pressure chamber 32, and is the same as the above-described high-pressure generation device 110 in the operation of the first pressure chamber 31, the second pressure chamber 32, and third pressure chamber 33 for performing the pumping operation using the reciprocal movement of the piston 1 and the plunger 18.

[0123] FIG. 17 is an example of one configuration of the high-pressure generation device which reciprocates a piston and a plunger with a drive unit in which an eccentric cam or bearing is integral with a rotating drive shaft arranged midway therebetween.

[0124] The high-pressure generation device 630 integrates an eccentric cam or bearing with the rotating drive shaft 76a of the drive unit, sandwiches the cam or bearing using a recessed extension part 17, and connects the piston 1 and the plunger 18, thereby allowing the piston 1 and the plunger 18 used to perform the pumping operation to reciprocate.

[0125] The force being in balance with the thrust of the drive unit is expressed by the product of the area of the pressure-receiving surface when the liquid acts on the second pressure chamber and the generated pressure.

[0126] When moving in the one direction (the left direction), through the thrust of the drive unit, the second pressure chamber 32 reduces and the liquid flows into the expanding third pressure chamber 33. At the same time, the residual liquid is discharged from the outlet port 267. In order to balance with the thrust of the drive unit, pressure in accordance with the area of the pressure-receiving surface acting on the liquid in the second pressure chamber 32 and the area of the pressure-receiving surface acting on the liquid in the third pressure chamber 33 is generated, and the liquid being pressurized is discharged outside from the outlet port 267.

[0127] When moving in the other direction (the right direction), the third pressure chamber 33 reduces, and the pressurized liquid is discharged. In order to balance with the thrust of the drive unit, pressure in accordance with the area of the pressure-receiving surface acting on the liquid in the third pressure chamber 33 is generated. The liquid being pressurized is discharged outside from the outlet port 267. In addition, pressure is generated due to the difference in the area of the pressurizing surface between the first pressure chamber 31 and the second pressure chamber 32.

[0128] Therefore, in order for the discharge pressure when moving in the one direction (the left direction) and the discharge pressure when moving in the other direction (the right direction) to be equal, in accordance with the thrust of the drive unit, the area of the pressure-receiving surface on which the liquid in the second pressure chamber 32 acts and the area of the pressure-receiving surface on which the liquid in the third pressure chamber 33 acts are selected.

[0129] When moving in the other direction (the right direction), through the difference in the pressure-receiving surface between the first pressure chamber 31 and the second pressure chamber 32 on which the liquid acts, the pressure within the first pressure chamber 31 increases as the movement of the piston 1 and the plunger 18 advances. The discharge pressure from the third pressure chamber 33 thereby decreases as the movement advances, or when there is a margin of thrust on the drive side, the discharge pressure does not change, and the thrust on the drive side increases. The pressure discharged from the outlet 257 depends on the load at the place of discharge. When being discharged with the maximum pressure, or for example, when in the high-pressure generation device 630 in accordance with the present invention the discharge pressure at the outlet port 257 when being emitted from a miniature diameter nozzle is low, the fluctuation is low. The higher the discharge pressure, the larger the fluctuation.

[0130] FIG. 18 and FIG. 19 are more examples of the high-pressure generation device in which a piston and a plunger are arranged on the left and right with an actuator sandwiched therebetween. Unlike FIG. 15 and FIG. 16, the high-pressure generation device 210B is provided with the second pressure chamber 32 at the tip of the small-diameter piston part 9b, but as it shares other configurations and manner of operation, any description thereof will be omitted.

[0131] FIG. 20 is a configuration example in which the drive unit shown in FIG. 17 is arranged midway therebetween instead of the actuator shown in the configuration examples of the high-pressure generation device shown in FIG. 18 and FIG. 19.

[0132] This high-pressure generation device 620 has the same configuration as that shown in those figures, and as such, any description thereof will be omitted.

[0133] FIG. 21 is an example of the high-pressure generation device in which the second pressure chamber and the third pressure chamber are provided in both side chambers of the piston part 8.

[0134] As shown in FIG. 21, this high-pressure generation device 310 arranges the piston 1 and the plunger 18 on the left and right with the actuator 6 arranged midway therebetween, is provided with the second pressure chamber 32 and the third pressure chamber 33 outside the piston 1 within the housing 2, is provided with the first pressure chamber 31 in the space at the tip of the plunger 18 on the other side, and allows the second pressure chamber 32 and the first pressure chamber 31 to communicate with each other through the second flow passage 311 provided within the housing 2. The piston 1 and the plunger 18 reciprocate using the actuator 6. The actuator 6, which is a double-rod fluid pressure cylinder having two control pistons, is used as a pulsation-free pump which feeds the working fluid L to reciprocate the control pistons, thereby drawing the liquid F from the outside and discharging the liquid with a constant pressure from the outlet port 267 continuously.

[0135] The housing 2 which has the outlet port 267 and into which the piston 1 is fitted therewithin and a housing 2a which has the intake port 257 and into which the plunger 18 is fitted therewithin are clamped by a bolt 4 with the actuator 6 sandwiched therebetween. The piston 1 and the large-diameter plunger 18 which are reciprocated by the actuator 6 are arranged on the left and right with the actuator 6 arranged midway therebetween. The first pressure chamber 31 is provided at the tip of the large-diameter plunger 18. The second pressure chamber 32 is provided in the side chamber at the inner part of the piston part 8, which reciprocates in conjunction with the plunger 18 and of which the outer diameter is smaller than that of the plunger 18. The third pressure chamber 33 is provided in the side chamber of the piston part 8 on the piston rod 7 side. The check valve 81 is provided in the first flow passage 254 which communicates via the intake port 257 to the first pressure chamber 31. The check valve 82 is provided in the second flow passage 311 which communicates via the first pressure chamber 31 to the second pressure chamber 32. The check valve 83 is provided in the third flow passage 271 which communicates via the second pressure chamber 32 to the third pressure chamber 33. The outlet port 267 is provided which discharges the liquid from the third pressure chamber 33 to the outside.

[0136] FIG. 22 is a graph showing a waveform (theoretical values) of the discharge pressure Pd of the high-pressure generation device in accordance with the present embodiment. The horizontal axis represents time elapsed, while the vertical axis represents the pressure of the liquid discharged.

[0137] As shown in FIG. 24, in the high-pressure generation device 110 in accordance with the present embodiment, one stroke at the onset of operation is pressurized from a zero-pressure state, but thereafter, except for stop states S, or the moments at which the movement direction of the piston switches, the discharge pressure Pd of the liquid is kept constant at all times. The high-pressure generation device 110 therefore does not require an accumulator and can discharge high-pressure liquid with very small pressure fluctuations.

[0138] FIG. 23 is a graph showing a waveform (theoretical values) of the discharge pressure P of the pressure conversion device including two pressurizing chambers disclosed in Japanese Examined Patent Application Publication No. 62-21994 as a comparative example. The horizontal axis represents time elapsed, while the vertical axis represents the pressure of the liquid discharged.

[0139] As shown in FIG. 23, since the pressure conversion device including two pressurizing chambers switches using a directional control valve, it takes time for switching, and two pressurizing chambers require pressurizing from a zero-pressure state for each cycle, thereby providing the liquid discharged with large pressure fluctuations.

INDUSTRIAL APPLICABILITY

[0140] The high-pressure generation device in accordance with the present invention can be applied to a various kinds of hydraulic machines and devices for water jets, can be provided a pressure intensifier and a volume intensifier, and can be provided as a pump which discharges liquid such as chemicals and slurries, which are different from the working fluid L.

Claims

1. A high-pressure generation device comprising: a plurality of reciprocating pistons which are coaxially connected to a reciprocating drive shaft of a drive unit and have different outer diameters and three pressure chambers which pressurize liquid drawn from the outside through the pumping operation of the plurality of pistons, pressurizes liquid drawn from the outside, and discharges liquid pressurized to a constant pressure to the outside in each reciprocating operation of the plurality of pistons, wherein the three pressure chambers comprising a first pressure chamber for drawing liquid from the outside, a second pressure chamber of which the pressurizing area for pressurizing liquid is smaller than that of the first pressure chamber, and a third pressure chamber of which the pressurizing area is smaller than that of the second pressure chamber and which discharges liquid to the outside, and the pressurizing areas of the second pressure chamber and the third pressure chamber are set so that the ratio of the difference between the pressurizing areas of the second pressure chamber and the third pressure chamber to the thrust when the plurality of pistons move in the one direction is equal to the ratio of the pressurizing area of the third pressure chamber to the thrust when the plurality of pistons move in the other direction, or the direction opposite to the one direction.

2. The high-pressure generation device as claimed in claim 1, wherein the drive shaft is reciprocated by a drive unit having a rotating shaft, and the pressurizing area of the second pressure chamber is set to be twice as large as the pressurizing area of the third pressure chamber.

3. The high-pressure generation device as claimed in claim 1 or 2, comprising an auxiliary chamber which communicates with the first pressure chamber or the second pressure chamber, wherein the volume of the auxiliary chamber is adjustable.

4. The high-pressure generation device as claimed in claim 1 or 2, comprising: an intake port for drawing liquid from the outside; a first flow passage allowing the liquid drawn from the intake port to flow into the first pressure chamber; a second flow passage allowing the liquid pressurized by the first pressure chamber to flow into the second pressure chamber; a third flow passage allowing the liquid pressurized to a predetermined pressure to flow into the third pressure chamber; and an outlet port for discharging the liquid pressurized to a constant pressure from the third pressure chamber to the outside, wherein each of the first flow passage, the second flow passage, and the third flow passage is provided with a backflow prevention device allowing liquid to flow only in a predetermined direction.

5. The high-pressure generation device as claimed in claim 4, wherein when the plurality of pistons move in the one direction, both the first pressure chamber and the third pressure chamber increase in volume, opening the backflow prevention devices of both the first flow passage and the third flow passage, and the second pressure chamber decreases in volume, closing the backflow prevention device of the second flow passage, thereby allowing the liquid pressurized to a constant pressure to be discharged from the outlet port.

6. The high-pressure generation device as claimed in claim 4, wherein when the plurality of pistons move in the other direction, both the first pressure chamber and the third pressure chamber decrease in volume, closing the backflow prevention devices of both the first flow passage and the third flow passage, and the second pressure chamber increases in volume, opening the backflow prevention device of the second flow passage, thereby allowing the liquid pressurized to a constant pressure to be discharged from the outlet port.

7. The high-pressure generation device as claimed in claim 4, wherein any of the first flow passage, the second flow passage, and the third flow passage is formed outside the plurality of pistons.

8. The high-pressure generation device as claimed in claim 4, wherein the third pressure chamber is formed at the tip of a piston of which the outer diameter is smallest out of the plurality of pistons, the third flow passage is formed within the plurality of pistons, and both the first flow passage and the second flow passage are formed outside the plurality of pistons.