Water hammer generating device and pile driver hydraulic system

Abstract

The invention relates to the technical field of pile drivers, in particular to a water hammer generating device and a pile driver hydraulic system. In order to solve the problems that an existing hydraulic pile driver is low in power density and large in hydraulic system size, a multistage displacement amplification unit is driven through a magnetostrictive rod, a valve element is rapidly controlled to be closed so as to generate the water hammer effect, a hydraulic cylinder piston is pushed through high pressure of a water hammer to lift a hammer head, and the hammer head is accelerated to fall to impact a pile body in combination with gravity. The magnetic drive mechanism comprises an electromagnet outer wall, a coil and a magnetostriction rod, the multi-stage displacement amplification unit comprises an input push rod, a lever and an output push rod which are connected in series, and the hydraulic system integrates a high-pressure small-flow pump and a low-pressure large-flow pump. The power density of the hydraulic system is remarkably improved through the water hammer effect, the response speed of the magnetostriction rod reaches the nanosecond level, rapid opening and closing of the valve element are achieved in combination with the multi-stage displacement amplification unit, and the power density of the hydraulic system can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pile drivers, and in particular to a water hammer generating device and a pile driver hydraulic system. Background Art

[0002] The hydraulic pile driver pushes the piston upward through the hydraulic system, thereby driving the weight to rise. When the weight reaches the highest point, the reversing valve controls the hydraulic oil to reverse, and the hydraulic pressure then pushes the piston downward, causing the weight to fall quickly, generating an impact force to sink the pile into the soil. When it is necessary to improve work efficiency and shorten construction period, it is necessary to speed up the pile drop speed and increase the impact force, which requires a heavier weight for the weight and a greater pressure for the hydraulic system, thereby increasing the volume of the hydraulic system and reducing the power density of the hydraulic pile driver. Therefore, how to improve the power density of the hydraulic pile driver while meeting the demand is a technical problem to be solved. Summary of the invention

[0003] The problem to be solved by the present invention is to improve the power density of a hydraulic pile driver.

[0004] In view of the shortcomings of the prior art, the present invention solves the technical problems by adopting a technical solution: a water hammer generating device, comprising a magnetic drive mechanism, a multi-stage displacement amplification unit and a valve body;

[0005] Magnetic drive mechanism: arranged at the upper part of the device, including the outer wall of the electromagnet, a coil arranged in the inner chamber of the outer wall of the electromagnet, and a magnetostrictive rod passing through the coil;

[0006] Multi-stage displacement amplification unit: connected to the magnetostrictive rod, including at least one set of displacement amplification units connected in series, each stage of the displacement amplification unit including an input push rod, a lever and an output push rod;

[0007] Valve body: It is arranged at the lower part of the device, and a valve core is slidably arranged in its inner cavity; the final output push rod of the multi-stage displacement amplification unit passes through the lower end cover of the valve body and is connected to the top of the valve core;

[0008] Both ends of the valve core are provided with valve core springs for resetting the valve core;

[0009] The valve body is provided with an oil inlet and an oil return port, and the sliding of the valve core controls the conduction or sealing of the oil inlet and the oil return port.

[0010] Preferably, adjacent displacement amplification units in the multi-stage displacement amplification unit are connected via a positioning sleeve, and the positioning sleeve comprises an outer wall, an inner hole and a crossbeam, and is used to fix and guide the displacement of the output push rod.

[0011] Preferably, an electromagnetic interface is provided on the outer side of the outer wall of the electromagnet, and the electromagnetic interface drives the magnetostrictive rod to move axially through the coil when energized.

[0012] Preferably, an end cover is provided on the top of the magnetic drive mechanism, and an adjusting screw passes through the end cover. The bottom end of the adjusting screw is connected to the magnetostrictive rod and is used to adjust the initial position of the magnetostrictive rod.

[0013] Preferably, the oil inlet and the oil return port are arranged opposite to each other and have a height difference Δh, and the range of Δh is 5cm-10cm.

[0014] A pile driver hydraulic system comprises a hydraulic cylinder and a hammer head, wherein the upper chamber and the lower chamber of the hydraulic cylinder are both connected to a main hydraulic circuit, the main hydraulic circuit is connected to a control circuit, the control circuit comprises the water hammer generating device according to any one of claims 1 to 5, the main hydraulic circuit comprises a low-pressure high-flow pump and a high-pressure low-flow pump, and the piston movement of the hydraulic cylinder is controlled by the water hammer generating device.

[0015] Preferably, the control loop further includes:

[0016] A one-way valve connected to the oil inlet of the water hammer generating device;

[0017] The hydraulically controlled one-way valve controls the conduction of the main hydraulic circuit through the linkage of the switch valve.

[0018] Preferably, a two-position three-way electromagnetic reversing valve is provided in the main hydraulic circuit, and the two-position three-way electromagnetic reversing valve controls the oil circuit switching of the upper and lower chambers of the hydraulic cylinder through an electromagnet, and the lower chamber of the hydraulic cylinder is also connected to the oil tank through a one-way valve.

[0019] Preferably, the switch valve comprises a valve body, an oil inlet and an oil return port are arranged on the valve body, a valve core is arranged in the valve body, and the valve core slides in the valve body to realize the conduction or sealing of the oil inlet and the oil return port.

[0020] Preferably, the water hammer generating device triggers the water hammer effect by quickly closing the valve core, so that an instantaneous high pressure is formed in the low-pressure and high-flow pump circuit, which drives the hammer head to accelerate its movement.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) Use a high-pressure, low-flow pump 1 in conjunction with a water hammer generating device 1 to generate a water hammer effect. The high pressure generated by the water hammer effect is used to control the switch valve 1 to close quickly, thereby generating a water hammer effect in the low-pressure, high-flow pump 1 circuit. By controlling the high-pressure fluid of the water hammer effect to enter the hydraulic cylinder, the piston is pushed up. When the pressure is reduced to the point where the piston cannot be pushed up, the high-pressure, low-flow pump 2 on the other side is used in conjunction with the water hammer generating device 2 to generate a water hammer effect. Similarly, the high pressure generated by the water hammer effect is used to control the switch valve 2 to close quickly, generating a water hammer effect in the corresponding circuit of the low-pressure, high-flow pump 2. By controlling the high-pressure fluid of the water hammer effect to enter the upper chamber of the hydraulic cylinder, the piston moves downward quickly under the combined action of the high-pressure oil and the gravity of the hammer head to hit the pile body. The high pressure generated by the hydraulic water hammer effect is used to achieve the effect of lifting the hammer head and accelerating the falling of the hammer head, and the hydraulic system cost is low.

[0023] (2) The magnetostrictive rod and multi-stage displacement amplification unit realize the amplification of small displacements. According to actual needs, the displacement amplification unit can be connected in series in multiple stages to obtain a more significant displacement amplification effect.

[0024] (3) The water hammer generating device uses a magnetostrictive rod to realize valve core closing control. The response time of the magnetostrictive rod is in the nanosecond level. The fast response time means that the valve core closes quickly, the water hammer effect is more obvious, the pressure generated is higher, and the speed of controlling the closing of the switch valve is also fast, thereby ensuring that the pressure generated by the water hammer effect in the circuit of the low-pressure and high-flow pump is higher, and the pushing effect of the heavy hammer is better.

[0025] (4) Check valves are installed at the outlets of both the low-pressure, high-flow pump and the high-pressure, low-flow pump to prevent the high pressure generated by the water hammer effect from being transmitted to the hydraulic pump, thus avoiding potential damage to the hydraulic pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the hydraulic system of the water hammer pile driver of the present invention;

[0027] Figure 2 It is an enlarged schematic diagram of the water hammer generating device 1 and the water hammer generating device 2 of the present invention;

[0028] Figure 3 It is an enlarged schematic diagram of the switch valve 1 and the switch valve 2 of the present invention;

[0029] Figure 4 is an enlarged schematic diagram of a positioning sleeve involved in the present invention;

[0030] Figure 5 It is a cross-sectional schematic diagram of a displacement amplification unit involved in the present invention;

[0031] Description of the accompanying drawings: 1. Low-pressure, high-flow pump 1; 17. Low-pressure, high-flow pump 2; 2. High-pressure, low-flow pump 1; 18. High-pressure, low-flow pump 2; 3. One-way valve 1; 19. One-way valve 2; 20. One-way valve 3; 25. One-way valve 4; 4. Safety valve 1; 6. Safety valve 2; 21. Safety valve 3; 22. Safety valve 4; 5. Water hammer generating device 1; 23. Water hammer generating device 2; 7. Hydraulic control one-way valve; 26 , hydraulic control check valve 2; 27, hydraulic control check valve 3; 28, hydraulic control check valve 4; 8, electromagnet 1; 10, electromagnet 2; 11, electromagnet 3; 13, electromagnet 4; 9, two-position three-way electromagnetic reversing valve 1; 12, two-position three-way electromagnetic reversing valve 2; 14, hydraulic cylinder; 15, hammer; 16, switch valve 1; 24, switch valve 2; 29, high-level oil tank; 30, check valve 5; 501, adjusting screw; 50 2. End cover; 503. Sealing ring; 504. Electromagnet outer wall; 505. Coil; 506. Magnetostrictive rod; 507. Sealing ring; 508. Input push rod 1; 519. Input push rod 2; 509. Lever 1; 511. Lever 2; 510. Output push rod 1; 518. Output push rod 2; 512. Valve core; 513. Oil return port; 514. Valve body; 515. Valve core plug; 516. Valve core spring Spring; 517, oil inlet; 520, positioning sleeve; 521, push rod fulcrum; 522, electromagnetic interface; 523, sealing ring; 524, lower end cover; 601, valve core plug; 602, valve body; 603, oil inlet; 604, sealing ring; 605, spring retaining ring; 606, centering spring; 607, valve core; 608, oil return port; 5202, outer wall; 5201, inner hole; 5203, crossbeam. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0033] In order to improve the power density of the hydraulic pile driver, the present invention designs a water hammer pile driver hydraulic system and a corresponding water hammer generating device, which utilizes the high pressure generated by the water hammer effect of the hydraulic system to push the heavy hammer up and down in sequence, thereby improving the power density of the system.

[0034] like Figure 1As shown, the upper chamber and the lower chamber of the hydraulic cylinder 14 are both connected to a main liquid circuit, and the main liquid circuit is connected to a control circuit. The hydraulic cylinder 14 drives the hammer head 15 to rise or fall through the reciprocating motion of its piston rod. The main liquid circuit connected to the lower chamber of the hydraulic cylinder 14 includes a low-pressure, high-flow pump 1, a one-way valve 25, a hydraulically controlled one-way valve 7 and a two-position, three-way electromagnetic reversing valve 9. When the main liquid circuit is turned on, the hydraulically controlled one-way valve 7 is triggered by the switch valve 16; the triggering of the switch valve 16 is realized by the corresponding control circuit. The control circuit connected to the switch valve 16 includes a high-pressure, low-flow pump 2, a one-way valve 3, a water hammer generating device 5 and a hydraulically controlled one-way valve 27. The water hammer generating device 5 triggers the water hammer effect by quickly closing the valve core 512. The water hammer effect triggers the switch valve 16. After the switch valve 16 is triggered, an instantaneous high pressure is formed in the circuit of the low-pressure, high-flow pump 1, pushing the hammer head 15 to rise faster. As shown Figure 1 As shown in the figure, the lower chamber of the hydraulic cylinder 14 is connected to the oil tank through a one-way valve 530. When the piston moves upward quickly, negative pressure is generated in the lower chamber of the hydraulic cylinder 14, the one-way valve 530 opens, and the hydraulic oil in the oil tank enters the hydraulic cylinder 14 under the action of atmospheric pressure. When the piston of the hydraulic cylinder 14 moves downward, the one-way valve 530 closes and the oil flows from the lower chamber of the hydraulic cylinder 14 back to the oil tank through the two-position three-way electromagnetic reversing valve 19 to the right position.

[0035] The main liquid circuit connected to the upper chamber of the hydraulic cylinder 14 includes a low-pressure, high-flow pump 17, a one-way valve 19, a hydraulically controlled one-way valve 26, and a two-position, three-way electromagnetic reversing valve 12. When the main liquid circuit is turned on, it is achieved by opening the switch valve 24 to trigger the hydraulically controlled one-way valve 26; the triggering of the switch valve 24 is achieved by the corresponding control circuit. The control circuit connected to the switch valve 24 includes a high-pressure, low-flow pump 18, a one-way valve 3 20, a water hammer generating device 23 and a hydraulically controlled one-way valve 4 28. The water hammer generating device 23 triggers the water hammer effect by quickly closing its own valve core 512. The water hammer effect triggers the switch valve 24. After the switch valve 24 is triggered, an instantaneous high pressure is formed in the circuit of the low-pressure, high-flow pump 17, pushing the hammer head 15 to accelerate its descent.

[0036] When the hydraulic system is running without load, the hydraulic oil in the oil tank is extracted by the low-pressure and high-flow pump 1 and then returned to the oil tank through the one-way valve 425 and the switch valve 16. The outlet of the switch valve 16 and the inlet of the low-pressure and high-flow pump 1 are connected to the oil tank. The system has no load and the system pressure is approximately equal to the atmospheric pressure.

[0037] The hydraulic oil output by the low-pressure, high-flow pump 17 passes through the one-way valve 19 and the switch valve 24 and returns to the oil tank. The inlet of the low-pressure, high-flow pump 17 and the outlet of the switch valve 24 are both connected to the oil tank. The system has no load and the system pressure is approximately equal to atmospheric pressure.

[0038] The hydraulic oil output by the high-pressure small-flow pump-2 flows into the oil inlet 517 of the water hammer generating device-5 through the one-way valve-3, and flows back to the oil tank from the oil return port 513. The inlet of the high-pressure small-flow pump-2 and the oil return port 513 of the water hammer generating device-5 are both connected to the oil tank.

[0039] The hydraulic oil output by the high-pressure small-flow pump 18 flows into the oil inlet 517 of the water hammer generating device 23 through the one-way valve 20, and flows back to the oil tank from the oil return port 513. The inlet of the high-pressure small-flow pump 18 and the oil return port 513 of the water hammer generating device 23 are both connected to the oil tank.

[0040] like Figure 2 As shown, the valve core 512 of the water hammer generating device 5 is in the middle position under the action of the valve core springs 516 on both sides, and the oil inlet 517 is connected with the oil return port 513.

[0041] like Figure 3 As shown, the valve core 607 of the switch valve 16 is in the middle position under the action of the centering springs 606 on both sides, and the oil inlet 603 is connected to the oil return port 608.

[0042] The water hammer generating device 1 5 has the same structure as the water hammer generating device 2 23. The water hammer generating device 1 5 includes a magnetic drive mechanism, a multi-stage displacement amplification unit and a valve body 514. The magnetic drive mechanism includes an end cover 502 and an electromagnet outer wall 504. A sealing ring 503 is provided between the end cover 502 and the electromagnet outer wall 504. The end cover 502 and the electromagnet outer wall 504 are detachably connected. A coil 505 is installed in the electromagnet outer wall 504. A magnetostrictive rod 506 is inserted in the coil 505. The magnetostrictive rod 506 can slide in the coil 505. A threaded hole is processed at the center of the end cover 502. An adjusting screw 501 is installed in the threaded hole. The adjusting screw 501 can adjust the position of the magnetostrictive rod 506. The multi-stage displacement amplification unit includes at least one group of displacement amplification units connected in series. The displacement amplification unit includes an input push rod, a lever and an output push rod, such as Figure 2 As shown, it includes a two-stage displacement amplification unit connected in series, an input push rod 508 is connected below the magnetostrictive rod 506, a sealing ring 507 is installed between the coil 505 and the input push rod 508, the input push rod 508 is cylindrical, and push rod fulcrums 521 with spherical ends and a cylindrical body are arranged at four quadrant points, the input push rod 508 can slide in the inner cylindrical cavity of the electromagnet outer wall 504, and a lever 509 is below the input push rod 508. The lever 509 is a cantilever structure with one end fixed. When the push rod fulcrum 521 pushes the lever 509, the free end of the lever 509 can amplify the displacement of the push rod fulcrum 521, and a positioning sleeve 520 is fixedly installed below the lever 509, as shown in FIG. Figure 4The positioning sleeve 520 shown includes an outer wall 5202, an inner hole 5201, and a crossbeam 5203, wherein the outer wall 5202 is fixedly mounted on the outer wall 504 of the electromagnet, and the output push rod 1 510 passes through the inner hole 5201, and the output push rod 1 510 can slide in the inner hole 5201, and the first-stage displacement amplification unit includes an input push rod 1 508, a lever 1 509, and an output push rod 1 510, and a second-stage displacement amplification unit is installed below the output push rod 1 510, and the second-stage displacement amplification unit includes an input push rod 2 519, a lever 2 511, and an output push rod 2 518, and the structure is the same as the above structure, and can be superimposed according to actual conditions. The output push rod 2 518 passes through the lower end cover 524, and a sealing groove is processed on the lower end cover 524, and a sealing ring is installed to prevent hydraulic oil from entering. The output push rod 2 518 contacts the top of the valve core 512, and the output push rod 2 518 can push the valve core 512 to move. The lower end cover 524 is detachably connected to the valve body 514. The working principle of the magnetostrictive rod 506 is that the ferromagnetic material is stretched (or shortened) under the action of an external magnetic field, and it recovers its original length after the external magnetic field is removed. This phenomenon is called magnetostrictive phenomenon (or effect). Magnetostriction is a unique property of ferromagnetic materials. In the present invention, the magnetostrictive rod 506 produces axial expansion and contraction deformation after the coil 505 is energized, and its displacement is proportional to the magnetic field strength. The response time is less than 1 microsecond, ensuring that the valve core 512 is quickly opened and closed.

[0043] The valve body 514 is processed with an oil inlet 517 and an oil return port 513. The oil inlet 517 and the oil return port 513 are arranged opposite to each other and have a height difference Δh, and the range of Δh is 5cm-10cm. The valve body 514 is hollow and contains a valve core 512. The valve body 514 is installed with a valve core plug 515, and the valve core plug 515 is detachably connected to the valve body 514. Valve core springs 516 are installed at both ends of the valve core 512. The valve core springs 516 have the same specifications. When the valve core 512 is not subjected to external force, the two valve core springs 516 can make the valve core 512 in the middle open position, and the oil inlet 517 is connected to the oil return port 513. The valve core 512 is also processed with a sealing groove, which contains a sealing ring 523.

[0044] When the system is working, the electromagnetic interface 522 of the water hammer generating device 5 is energized, the coil 505 is energized to generate a magnetic field, the magnetostrictive rod 506 is extended due to the induction of the magnetic field, and pushes the input push rod 1 508 to move. The push rod fulcrum 521 on the input push rod 1 508 pushes the lever 1 509 to move, and the small displacement of the magnetostrictive rod 506 is amplified. After the output push rod 1 510 moves, it pushes the input push rod 2 519 to move. The input push rod 2 519 is similar to the output push rod 1 510 in structure, but has a slightly larger outer diameter. The push rod fulcrum on the input push rod 2 519 pushes the lever 2 511 to move, and then pushes the output push rod 2 518 to move downward.

[0045] like Figure 5The figure shows a single cross-sectional schematic diagram of displacement amplification, where an input push rod 508, a push lever 509, and an output push rod 510 together constitute a displacement amplification unit. In this example, two sets of displacement amplification units connected in series are used to amplify the small displacement of the magnetostrictive rod 506. According to actual needs, multiple sets of displacement amplification units can also be connected in parallel to enable the output push rod 518 to obtain a larger displacement. Figure 5 The horizontal distance between points A and B is m, the horizontal distance between points B and C is n, the lever ratio AB:BC=m:n=1:3, and the single-stage displacement amplification unit can achieve a displacement amplification of 3 times. The input push rod 508 pushes the free end of the lever 509 through the push rod fulcrum 521. Figure 2 As shown, when the lever ratio is 1:3, the output displacement of the first-stage displacement amplification unit is amplified by 3 times; the second-stage displacement amplification unit further amplifies the displacement, and the total amplification factor can reach 9 times.

[0046] The output push rod 2 518 pushes the valve core 512 downward, and the oil inlet 517 is disconnected from the oil return port 513. Since the response speed of the magnetostrictive rod 506 is in the nanosecond level, the closing of the valve core 512 in the high-pressure small flow pump 12 circuit generates a water hammer effect, and the closer to the oil inlet 517 of the water hammer generating device 15, the higher the fluid pressure. Therefore, under the action of the pressure difference, the hydraulic control check valve 3 27 opens, and the pressurized fluid pushes the valve core 607 of the switch valve 16 to close quickly. In the low-pressure large flow pump 1 circuit, a water hammer effect is also formed, and the closer to the oil inlet 603 of the switch valve 16, the higher the fluid pressure. Under the action of the pressure difference, the hydraulic control check valve 17 opens. At this time, the electromagnet 18 of the two-position three-way electromagnetic reversing valve 19 is energized, and the pressurized fluid enters the lower chamber of the hydraulic cylinder 14, pushing the piston upward. The electromagnet 3 11 of the two-position three-way electromagnetic reversing valve 2 12 is energized, and the return oil from the upper chamber of the hydraulic cylinder 14 flows into the oil tank.

[0047] When the circuit produces a water hammer effect, the hydraulic oil output by the high-pressure, low-flow pump-2 flows back to the oil tank through a safety valve-4, and the hydraulic oil output by the low-pressure, high-flow pump-1 flows back to the oil tank through a safety valve-6.

[0048] When the circuit pressure of the low-pressure, high-flow pump 1 is unable to push the piston upward, the coil 505 of the water hammer generating device 5 loses power, and the valve core 512 reopens under the action of the valve core spring 516. The liquid pressure acting on the valve core 607 of the switch valve 16 disappears, and the valve core 607 also reopens under the action of the centering springs 606 on both sides. At the same time, the valve core 512 of the water hammer generating device 23 in the circuit of the high-pressure small flow pump 218 is closed, generating a water hammer effect, and the pressure oil opens the hydraulic control check valve 428 in turn, pushing the valve core of the switch valve 24 to close, generating a water hammer effect in the circuit of the low-pressure large flow pump 217, and the high-pressure oil opens the hydraulic control check valve 226 in turn, and the electromagnet 413 of the two-position three-way electromagnetic reversing valve 212 is energized, and the high-pressure oil enters the upper chamber of the hydraulic cylinder 14, and the electromagnet 210 of the two-position three-way electromagnetic reversing valve 19 is energized, and the oil in the lower chamber of the hydraulic cylinder 14 flows back to the oil tank, and the hammer head 15 moves downward quickly under the combined action of the pressure oil and gravity to impact the precast pile. The upper chamber of the hydraulic cylinder 14 is replenished with oil from the high-position oil tank 29.

[0049] When the water hammer generating device 23 generates a water hammer effect, the hydraulic oil output by the high-pressure small-flow pump 218 flows back to the oil tank through the safety valve 3 21, and the hydraulic oil output by the low-pressure large-flow pump 217 flows back to the oil tank through the safety valve 4 22. After the impact is completed, the coil 505 of the water hammer generating device 23 loses power, and the valve core 512 reopens under the action of the valve core spring 516. The hydraulic pressure acting on the valve core 607 of the switch valve 24 disappears, and the valve core 607 also reopens under the action of the centering springs 606 on both sides. After completing a working cycle, the hydraulic system of the water hammer pile driver reciprocates the above process until the pile body is hit in place.

[0050] The switch valve 16 and the switch valve 2 24 have the same structure, the valve body 602 is hollow, one end of the valve body 602 is detachably connected with a valve core plug 601, the other end is installed with a spring retainer 605, and the spring retainer is connected to the control oil port, the valve core 607 is installed inside the valve body 602, and both ends of the valve core 607 are provided with centering springs 606, the centering springs 606 have the same specifications, so that the valve core 607 is in the middle position, and the oil inlet 603 is connected with the oil return port 608. The valve core 607 is processed with a sealing groove on its circumference, and a sealing ring 604 is installed in the sealing groove.

[0051] Through theoretical deduction, the structure of the present invention can better realize the action of pushing the hammer head 15 up and down, and the specific process is as follows:

[0052] The calculation formula for the hydraulic oil impact peak pressure is as follows:

[0053] ΔΡ=ρ·c·Δv;

[0054] Where: ΔP: pressure change (Pa); ρ: fluid density (kg / m 3); c: pressure wave propagation velocity (m / s); Δv: instantaneous change in hydraulic oil flow rate (m / s);

[0055] The formula for calculating the pressure wave propagation velocity is as follows:

[0056]

[0057] Where K is the bulk modulus of the liquid (unit: Pa, the bulk modulus of water is about 2.1×10 9 Pa);

[0058] ρ is the liquid density (unit: kg / m 3 ); E is the elastic modulus of the pipeline material (unit: Pa, the elastic modulus of steel is about 2×10 11 Pa); D is the inner diameter of the pipe (unit: m); δ is the pipe wall thickness (unit: m).

[0059] Example calculation:

[0060] Assume a steel pipe (E = 2 × 1011 Pa); inner diameter D = 0.5m, wall thickness δ = 0.01m, hydraulic oil density ρ = 1000kg / m 3 , bulk modulus K = 2.1 × 109 Pa, flow velocity change Δv = 2 m / s:

[0061]

[0062] Calculate step by step, 1. Calculate the pipeline flexibility correction item:

[0063]

[0064] 2. Denominator synthesis: 1+0.13=1.13;

[0065] 3. Molecular computing:

[0066] 4. Wave speed results: Peak pressure calculation: ΔΡ=ρ·c·Δv;

[0067] Substitute the value ΔP = 950·1100·2 = 2090000Pa = 2.09MPa;

[0068] Assuming that the weight of the pile driver hammer 15 is 4 tons, calculate the minimum piston area: According to the principle of hydraulic mechanics, the relationship between the hydraulic pressure F, the pressure p, and the piston area A is:

[0069] Hammer mass m = 4 tons = 4000 kg; gravity acceleration g = 9.81 m / s 2 ; Hydraulic pressure p = 2.09MPa = 2.09×106Pa.

[0070]

[0071] Theoretical piston area should be ≥187.8cm 2 (corresponding to diameter D≈15.5 cm);

[0072] Assume that the lifting needs to be accelerated (acceleration a = 2m / s 2 ), the total force increases to:

[0073] F dynamic = m × (g + a) = 4000 × 11.81 = 47, Dynamic ≈ 226cm 2 ;

[0074] Considering the influence of friction loss and sealing efficiency (about 90%), the safety factor k is taken as 1.5;

[0075] Actual piston area: A = 226 × 1.5 ≈ 339 cm 2 (corresponding diameter D≈21cm).

[0076] It can be seen from this that the force of the hydraulic oil impact can push the hammer head 15 up, so it is obvious that the force of the hydraulic oil impact can also push the hammer head 15 down.

[0077] In summary, the water hammer generating device and pile driver hydraulic system provided by the present invention realize the rapid cycle of lifting and accelerating the falling of the hammer head through the synergistic effect of the magnetostrictive rod and the multi-stage displacement amplification unit, combined with the high-pressure fluid generated by the water hammer effect. The process of realizing the water hammer effect is that when there is a sudden power outage or the valve is closed too quickly, the inertia of the pressure water flow generates a water flow shock wave, just like a hammer hitting, so it is called water hammer. The present invention uses the rapid closure of the valve and the inertia of the water flow to generate the water hammer effect. For example, when the valve core 512 is closed quickly, the kinetic energy of the fluid in the high-pressure small-flow pump-2 circuit suddenly changes into pressure energy, forming an instantaneous high pressure that can reach 2-3 times the rated pressure of the system, pushing the hydraulic control check valve 7 to open, triggering the water hammer effect of the low-pressure large-flow pump-1 circuit. Under the action of the water hammer effect, the pipeline will generate a lot of pressure. When the circuit produces a water hammer effect, because the circuit pressure is greater than the pump outlet pressure, because the hydraulic oil output by the pump flows back to the oil tank from the safety valve (4, 6, 21, 22), the check valve (3, 19, 20, 25) plays a role in isolating the circuit pressure, avoiding the high pressure generated by the water hammer effect from being transmitted to the hydraulic pump and damaging the hydraulic pump. Compared with the traditional hydraulic pile driver, this solution has the following advantages: (1) The water hammer effect is used to significantly improve the power density and reduce the volume of the hydraulic system; (2) The magnetostrictive rod has a nanosecond response speed to ensure that the valve core moves accurately and efficiently; (3) The multi-stage displacement amplification unit can be flexibly expanded to adapt to different load requirements; (4) The design of the check valve and the safety valve prevents high-pressure backflow from damaging the pump body and improves the system power density.

[0078] The above embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A water hammer generating device, characterized in that: It comprises a magnetic drive mechanism, a multi-stage displacement amplification unit and a valve body (514); The magnetic drive mechanism is arranged at the upper part of the device, and comprises an electromagnet outer wall (504), a coil (505) arranged in the inner chamber of the electromagnet outer wall (504), and a magnetostrictive rod (506) passing through the coil (505); A multi-stage displacement amplification unit is connected to the magnetostrictive rod (506), and comprises at least one group of displacement amplification units connected in series, wherein each stage of the displacement amplification unit comprises an input push rod, a lever and an output push rod; The valve body (514) is arranged at the lower part of the device, and a valve core (512) is slidably arranged in its inner cavity; the final output push rod of the multi-stage displacement amplification unit penetrates the lower end cover (524) of the valve body (514) and is connected to the top of the valve core (512); Valve core springs (516) are provided at both ends of the valve core (512) for resetting the valve core (512); The valve body (514) is provided with an oil inlet (517) and an oil return port (513), and the sliding movement of the valve core (512) controls the conduction or sealing of the oil inlet (517) and the oil return port (513).

2. The water hammer generating device according to claim 1, characterized in that: Adjacent displacement amplification units in the multi-stage displacement amplification unit are connected via a positioning sleeve (520), wherein the positioning sleeve (520) comprises an outer wall (5202), an inner hole (5201) and a crossbeam (5203), and is used to fix and guide the displacement of the output push rod.

3. The water hammer generating device according to claim 2, characterized in that: An electromagnetic interface (522) is provided on the outside of the electromagnet outer wall (504). When the electromagnetic interface (522) is energized, it drives the magnetostrictive rod (506) to move axially through the coil (505).

4. The water hammer generating device according to claim 1, characterized in that: An end cover (502) is provided on the top of the magnetic drive mechanism. An adjusting screw (501) passes through the end cover (502). The bottom end of the adjusting screw (501) is connected to the magnetostrictive rod (506) for adjusting the initial position of the magnetostrictive rod (506).

5. The water hammer generating device according to claim 1, characterized in that: The oil inlet (517) and the oil return port (513) are arranged opposite to each other and have a height difference Δh, and the range of Δh is 5 cm-10 cm.

6. A pile driver hydraulic system, comprising a hydraulic cylinder (14) and a hammer (15), wherein the upper chamber and the lower chamber of the hydraulic cylinder (14) are both connected to a main hydraulic circuit, and the main hydraulic circuit is connected to a control circuit, characterized in that: The control circuit comprises the water hammer generating device according to any one of claims 1 to 5, the main liquid circuit comprises a low-pressure high-flow pump and a high-pressure low-flow pump, and the piston movement of the hydraulic cylinder (14) is controlled by the water hammer generating device.

7. The pile driver hydraulic system according to claim 6, characterized in that: The control loop also includes: a one-way valve connected to the oil inlet (517) of the water hammer generating device; The hydraulically controlled one-way valve controls the conduction of the main hydraulic circuit through the linkage of the switch valve.

8. The pile driver hydraulic system according to claim 6, characterized in that: A two-position three-way electromagnetic reversing valve is provided in the main hydraulic circuit. The two-position three-way electromagnetic reversing valve controls the oil circuit switching of the upper and lower chambers of the hydraulic cylinder (14) through an electromagnet. The lower chamber of the hydraulic cylinder (14) is also connected to the oil tank through a one-way valve.

9. The pile driver hydraulic system according to claim 7, characterized in that: The switch valve comprises a valve body (602), the valve body (602) is provided with an oil inlet (603) and an oil return port (608), a valve core (607) is provided inside the valve body (602), and the valve core (607) slides inside the valve body (602) to achieve conduction or sealing of the oil inlet (603) and the oil return port (608).

10. The hydraulic system for a pile driver according to claim 6, characterized in that: The water hammer generating device triggers the water hammer effect by quickly closing the valve core (512), so that an instantaneous high pressure is formed in the low-pressure and high-flow pump circuit, thereby pushing the hammer head (15) to accelerate its movement.

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