Density-based pure water hydraulic system cavitation detection apparatus and method

Abstract

The present invention relates to the technical field of pure water hydraulic systems and provides a density-based cavitation detection device for pure water hydraulic systems, including a pipe for transporting a fluid medium, a detection mechanism disposed on the pipe and arranged so that a detection end intermittently contacts the fluid medium to acquire a cavitation signal of the fluid medium, and a blocking mechanism slidably fitted within the pipe and arranged so that the pipe and the detection mechanism can be intermittently switched between a blocked state and a communicating state. By detecting cavitation at intervals, the present invention reduces the impact of long-term hydraulic shock on the detection device and improves the accuracy of cavitation detection.

Description

[Technical Field]

[0001] The present invention relates to the technical field of pure water hydraulic systems, and more particularly to a device and method for detecting cavitation in pure water hydraulic systems based on density. [Background technology]

[0002] Hydraulic transmission is a method of transmitting, exchanging, and controlling energy using a liquid as the working medium. Hydraulic transmission and pneumatic transmission are both called fluid transmissions. These are new technologies developed based on the principle of hydrostatic transmission proposed by Pascal in the 17th century, and are widely used in engineering machinery, construction machinery, agricultural machinery, metallurgical machinery, mining machinery, space launches, and more. Currently, the level of fluid transmission technology has become an important symbol of the level of industrial development.

[0003] Pure water hydraulic transmission has attracted more and more attention because it has many advantages, such as easy material availability, low cost, no pollution, no combustion, small compression coefficient, and can replace mineral oil in various fields.

[0004] However, pure water hydraulic systems are more susceptible to cavitation than conventional hydraulic oil systems because the air separation pressure of pure water is higher than that of conventional mineral oil and it contains more air than conventional mineral oil under the same conditions.

[0005] Cavitation, also known as erosion or cavitation, is a phenomenon that occurs when an object is impacted by cavitation during liquid movement, resulting in surface deformation and material erosion. During cavitation, cavitation bubbles rapidly form, expand, and collapse, forming surges or high-speed microjets in the liquid. After impact, the crystal structure of the surface of a metal material becomes distorted, creating chemical instability, which causes different electrical potentials between adjacent crystal grains and accelerates the electrochemical corrosion process. The mechanical performance of the material in the eroded area deteriorates significantly, dramatically increasing the amount of cavitation. When designing pure water hydraulic systems, model tests must be conducted in advance to take measures to prevent cavitation as much as possible. To prevent cavitation, it is necessary to first detect whether or not cavitation is occurring and its severity. Currently, cavitation detection methods typically employ long-term continuous detection methods. When cavitation occurs, detection devices are prone to reduced cavitation signal detection accuracy due to prolonged hydraulic impact, and the detection signal fluctuations are small. Therefore, a density-based cavitation detection device and method for pure water hydraulic systems are urgently needed to address these issues. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to solve the above problems and provide a density-based cavitation detection device and method for pure water hydraulic systems that performs cavitation detection at intervals, thereby reducing the impact of long-term hydraulic shock on the detection device and improving cavitation detection accuracy. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides the following solution: a cavitation detection device for pure water hydraulic system based on density, a tube for transporting a fluid medium; a detection mechanism disposed on the tubular body, the detection end of which is disposed in intermittent contact with the fluid medium to acquire a cavitation signal of the fluid medium; The device further includes a blocking mechanism that is slidably fitted into the tubular body and is arranged so that the blocking / communication state between the tubular body and the detection mechanism can be intermittently switched by hydraulic action generated by the fluid medium.

[0008] Preferably, a control mechanism is further included, wherein a control section is formed in the control mechanism and communicates with the tube; wherein when the pipe transports a fluid medium and the hydraulic pressure is generated in the control section, the hydraulic pressure is arranged to move the blocking mechanism in a first direction to block the pipe, and the hydraulic pressure cooperates with a control end of the control mechanism to contact the detection end; When the blocking mechanism blocks the pipe and breaks down the hydraulic pressure in the control section, the blocking mechanism can move in a second direction opposite to the first direction to connect the pipe to the control section.

[0009] Preferably, the control mechanism comprises: a first cylinder having an internal cavity whose one end communicates with the pipe; a control element that is slidably fitted within the first cylinder, and whose control end extends from the first cylinder along the other end away from the tubular body by the hydraulic pressure and contacts the detection end; Each includes a communicating pipe communicating with the first cylinder and the closing mechanism, and an acting force in the same direction as the first direction is generated in the internal cavity of the communicating pipe by the hydraulic pressure, which acts on the closing mechanism.

[0010] Preferably, the control element comprises: a first slider that is in sliding contact with the inside of the first cylinder, has a seal ring fitted thereon, the seal ring being in sliding contact with the inner wall of the first cylinder, and has a column protrusion integrally formed at an upper portion thereof, the column protrusion extending from the first cylinder and contacting the detection end; The column includes a first spring wound around the convex portion, and both ends of the first spring are fixed to the first slider and the inner wall surface of the first cylinder, respectively.

[0011] Preferably, the closure mechanism comprises: a second cylinder provided at a tip of the first cylinder and communicating with the pipe body and the communicating pipe; a second slider that is slidably fitted into the second cylinder, has a piston structure integrally formed on the side closer to the communicating pipe, and that moves in the first direction in cooperation with the communicating pipe and the piston structure when an acting force in the same direction as the first direction is generated in the communicating pipe, thereby closing the pipe body; A second spring is disposed between the piston structure and the communicating pipe, and both ends of the second spring are fixed to the piston mechanism and the inner wall of the second cylinder, respectively.

[0012] Preferably, the detection mechanism comprises: a third cylinder provided near the control element and having a resistance strain gauge provided therein; a third slider provided on the third cylinder and in contact with the resistance strain gauge, one end of the third slider extending from the third cylinder and in contact with the control end;

[0013] Preferably, The device further includes an outer cylinder, an outer cylinder upper cover, and an outer cylinder lower cover detachably connected to the outer cylinder, and the third cylinder is fixed to the outer cylinder by the outer cylinder upper cover / outer cylinder lower cover, and the pipe is drilled into the outer cylinder and fixed to the outer cylinder.

[0014] Preferably, the first cylinder, the second cylinder, and the third cylinder all have a detachable connection structure.

[0015] The density-based cavitation detection method for pure water hydraulic systems is based on the above density-based cavitation detection device for pure water hydraulic systems, and includes: connecting the tubing to transfer the fluid medium and passing the fluid medium through the control section; Using the hydraulic pressure generated in the control section to act on the first slider and the second slider, respectively; bringing the first slider into contact with the third slider and acquiring a hydraulic pressure signal by a detection mechanism; Driving the second slider to close the pipe and break the hydraulic pressure in the control section; repeating the steps of resetting the second slider after hydraulic pressure is removed, placing the tube in communication with the control section, and passing fluid medium through the control section; The method includes a step of taking the average value m of the signal peak values ​​within a unit time of several acquired hydraulic signals, taking the minimum value of the signal peak value as n, and determining that cavitation is occurring when n<0.98m, and assuming that cavitation is not occurring in other cases. [Effects of the Invention]

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] In this invention, an external hydraulic system is used to pass the fluid medium through the pipe, so that the fluid medium is passed through the detection mechanism at a constant pressure. Intermittent contact between the detection end of the detection mechanism and the fluid medium is utilized to obtain hydraulic information about the fluid medium. A blocking mechanism is provided that slides into and fits onto the pipe, and the blocking mechanism 4 intermittently controls communication or blocking between the pipe and the detection mechanism 3. This achieves intermittent contact between the detection end of the detection mechanism and the fluid medium, reducing fatigue damage to the detection mechanism due to prolonged hydraulic shock and improving detection accuracy for cavitation. [Brief explanation of the drawings]

[0018] In the following, in order to more clearly explain the embodiments of the present invention or the technical solutions in the prior art, the drawings necessary for the embodiments will be briefly described. However, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative efforts. [Figure 1] FIG. 10 is a diagram showing the relative positions of the outer cylinder and the entire device. [Figure 2] FIG. 10 is a diagram showing the positional relationship between the blocking mechanism and the tube body. [Figure 3] FIG. 2 is a cross-sectional view of the structure of a first slider and a first cylinder. [Figure 4] FIG. 4 is a cross-sectional view of the structure of a second slider and a second cylinder. [Figure 5] FIG. 4 is a cross-sectional view of the structure of a third slider and a third cylinder. DETAILED DESCRIPTION OF THE INVENTION

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with accompanying drawings, but it is clear that the described embodiments are only a part of the embodiments of the present invention, and are not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative work fall within the scope of protection of the present invention.

[0020] In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be described in more detail below in conjunction with the drawings and specific embodiments.

[0021] 1 to 5, the cavitation detection device for pure water hydraulic system based on density is as follows: a pipe 1 for transporting a fluid medium; a detection mechanism 3 disposed on the tubular body 1, the detection end of which is intermittently brought into contact with the fluid medium to acquire a cavitation signal of the fluid medium; The device includes a blocking mechanism 4 that is slidably fitted into the tubular body 1 and is arranged so that it can intermittently switch between a blocked / connected state between the tubular body 1 and the detection mechanism 3 by hydraulic action generated by a fluid medium.

[0022] In the present invention, an external hydraulic system is used to pass the fluid medium through the tubular body 1, so that the fluid medium is passed through the detection mechanism 3 at a constant pressure. Oil pressure information about the fluid medium is obtained by utilizing intermittent contact between the detection end of the detection mechanism 3 and the fluid medium. A blocking mechanism 4 is provided that slides and fits into the tubular body 1, and the blocking mechanism 4 intermittently controls the communication or blocking state between the tubular body 1 and the detection mechanism 3, thereby achieving intermittent contact between the detection end of the detection mechanism 3 and the fluid medium, reducing fatigue damage to the detection mechanism 3 due to long-term hydraulic shock and improving detection accuracy for the occurrence of cavitation.

[0023] In this technical solution, the blocking mechanism 4 uses a common device such as an electric valve, and by controlling the intermittent opening and closing of the electric valve using a timing control device such as a timer, an intermittent communication state between the pipe body 1 and the detection mechanism 3 can be achieved. In addition, the detection mechanism 3 preferably acquires a hydraulic pressure signal using, for example, a pressure detection method, a displacement detection method, etc., but is not limited to these. When the fluid medium passes through the detection mechanism 3 and comes into contact with the detection end, the detection end detects the pressure change, displaces, and generates a signal, and either of these can acquire a hydraulic pressure signal to determine the occurrence of cavitation.

[0024] moreover, A control section communicating with the pipe body 1 is formed within the control mechanism 2. Here, when the pipe 1 transports the fluid medium and hydraulic pressure is generated in the control section, the hydraulic pressure is arranged to move the blocking mechanism 4 in the first direction to block the pipe 1, and the hydraulic pressure cooperates with the control end of the control mechanism 2 to contact the detection end; When the blocking mechanism 4 blocks the pipe body 1 and breaks down the hydraulic pressure in the control section, the blocking mechanism 4 moves in a second direction opposite to the first direction, thereby enabling communication between the pipe body 1 and the control section.

[0025] A control mechanism 2 is provided between the pipe 1 and the detection mechanism 3. A control section is formed within the control mechanism 2, and the control section accommodates the fluid medium. As the pipe 1 and the control section communicate, hydraulic pressure is generated within the control section. When the hydraulic pressure generates a force sufficient to move the blocking mechanism 4 in a first direction, the blocking mechanism 4 moves in the first direction to block the pipe 1. After blocking the pipe 1, the control section loses the pressure that continues to allow the fluid medium to pass through the pipe 1, and the hydraulic pressure is released. The blocking mechanism 4 moves in a second direction, restoring communication between the pipe 1 and the control section. After the fluid medium continues to pass through the pipe 1, the control section repeatedly and intermittently accommodates the fluid medium, generating hydraulic pressure. Under the control of the hydraulic pressure and the control mechanism 2, the fluid medium contacts the detection end, detecting the fluid medium.

[0026] Furthermore, when the oil pressure is contained to a certain extent, i.e., when the generated force is constant, the blocking mechanism 4 moves in the first direction due to the influence of the acting force and blocks the pipe body 1, thereby effectively ensuring the relative stability of the amount of fluid medium contained in the control section and the results obtained from oil pressure detection, and it can be understood that this effectively improves the accuracy of detecting cavitation occurrence in the fluid medium.

[0027] Furthermore, the control mechanism 2 a first cylinder 21 having an internal cavity at one end thereof communicating with the pipe body 1; a control element that is slidably fitted in the first cylinder 21, and whose control end extends from the first cylinder 21 along the other end away from the pipe body 1 by hydraulic pressure and contacts the detection end; Each includes a communication pipe 23 that communicates with the first cylinder 21 and the closing mechanism 4, and an acting force in the same direction as the first direction is generated in the internal cavity of the communication pipe 23 by hydraulic pressure, which acts on the closing mechanism 4.

[0028] Using a control element slidably fitted into the first cylinder 21, the pipe 1 communicates with the control element via the first cylinder 21, and when the pipe 1 transfers the fluid medium, the fluid medium passes through the first cylinder 21, and using the generated hydraulic pressure, the control ends of the control elements cooperate to extend from the first cylinder 21 and contact the detection ends, thereby obtaining a hydraulic signal. When hydraulic pressure is applied, the fluid medium passes through the communicating pipe 23, and under the influence of the weight of the liquid medium in the communicating pipe 23 and the hydraulic pressure, a force is generated in the same direction as the first direction and acts on the blocking mechanism 4, causing the blocking mechanism 4 to move in the first direction and block the pipe 1.

[0029] Furthermore, the control element is a first slider 22 that is in sliding contact with the inside of the first cylinder 21, has a seal ring 26 fitted thereon, the seal ring 26 being in sliding contact with the inner wall of the first cylinder 21, and has a column protrusion 25 integrally formed at the top, the column protrusion 25 extending from the first cylinder 21 and coming into contact with the detection end; The column protrusion 25 includes a first spring 24 wound therearound, and both ends of the first spring 24 are fixed to the first slider 22 and the inner wall surface of the first cylinder 21, respectively.

[0030] The first slider 22 slides within the first cylinder 21, and a seal ring 26 that contacts the inner wall of the first cylinder 21 is fitted to the first slider 22, thereby sealing the communication end between the first cylinder 21 and the tubular body 1. The hydraulic pressure generated by the fluid medium is used to push the first slider 22, causing the column protrusion 25 to slide along the first cylinder 21 and extend, bringing it into contact with the detection end to acquire a hydraulic pressure signal. After the hydraulic action is resolved, the first spring 24 resets the first slider 22, keeping the volume of the seal chamber formed in the first cylinder 21 constant and making the generation of hydraulic pressure relatively stable.

[0031] Furthermore, the closing mechanism 4 is a second cylinder 41 provided at the tip of the first cylinder 21 and communicating with the pipe body 1 and the communicating pipe 23; a second slider (42) that is slidably fitted into the second cylinder (41) and has a piston structure (44) integrally formed on the side closer to the communicating pipe (23), and that moves in the first direction in cooperation with the communicating pipe (23) and the piston structure (44) when an acting force in the same direction as the first direction is generated in the communicating pipe (23), thereby closing the pipe body (1); The second spring 43 is filled between the piston structure 44 and the communicating pipe 23, and both ends of the second spring 43 are fixed to the piston mechanism and the inner wall of the second cylinder 41, respectively.

[0032] One end of the second cylinder 41 is connected to the pipe 1, and the second cylinder 41 is positioned relative to the first cylinder 21 in a direction that allows the fluid medium to pass through. The other end of the second cylinder 41 is connected to the first cylinder 21 via the connecting pipe 23. As hydraulic pressure builds up within the first cylinder 21, the fluid medium passes through the connecting pipe 23, accumulating gravity and hydraulic pressure within the connecting pipe 23. When the force exceeds the supporting strength of the second spring 43, the force drives the piston mechanism 44 to move the second slider 42, which then extends from the second cylinder 41 and closes the pipe 1. The first cylinder 21 loses hydraulic pressure, allowing the fluid medium to pass continuously, and breaks down the hydraulic pressure within the control section. The reset action of the second spring 43 lifts the second slider 42, restoring communication between the pipe 1 and the first cylinder 21, thereby realizing the intermittent switching state.

[0033] Furthermore, the detection mechanism 3 is a third cylinder 31 provided near the control element and having a resistance strain gauge 33 provided therein; The third slider 32 is provided on the third cylinder 31 and contacts the resistance strain gauge 33, and one end of the third slider 32 extends from the third cylinder 31 and contacts the control end.

[0034] The fluid medium contained in the first cylinder 21 generates hydraulic pressure, which presses the first slider 22, driving the column protrusion 25 to extend from the first cylinder 21 and contact the third slider 32. The third slider 32 slides along the third cylinder 31 and contacts the resistance strain gauge 33, driving the protrusion of the resistance strain gauge 33. After that, the resistance strain gauge 33 is reset after the hydraulic pressure disappears. During this process, the resistance strain gauge 33 converts the pressure signal transmitted by the hydraulic pressure into an electrical signal, enabling intermittent detection of hydraulic cavitation.

[0035] Furthermore, it can be understood that the resistance strain gauge 33 in the third cylinder 31 can be selectively replaced with a general displacement sensor, and by detecting the sliding distance after the third slider 32 comes into contact with the column convex portion 25, it is possible to similarly obtain a signal generated by cavitation of the fluid medium, thereby realizing intermittent detection.

[0036] moreover, The system includes an outer cylinder 5, an outer cylinder upper cover 6 and an outer cylinder lower cover 7 that are detachably connected to the outer cylinder 5, and the third cylinder 31 is fixed to the outer cylinder 5 by the outer cylinder upper cover 6 / outer cylinder lower cover 7, and the tube body 1 is drilled inside the outer cylinder 5 and fixed to the outer cylinder 5.

[0037] Furthermore, the first cylinder 21, the second cylinder 41, and the third cylinder 31 all have a detachable connection structure.

[0038] In this technical solution, the outer cylinder 5 is configured with two internal cavities, one large and one small. The third cylinder 31 is enclosed in the smaller internal cavity and is threadedly connected to the outer cylinder 5 by multiple bolts around the outer cylinder upper cover 6. The third cylinder 31 is fixed to the outer cylinder 5, but the third cylinder 31 is not connected to the first cylinder 21. The tube 1 is drilled into the larger internal cavity, and a stopper card integrally molded with the tube 1 ensures a stable connection between the tube 1 and the outer cylinder 5. The first cylinder 21 and the second cylinder 41 are each connected to the tube 1 by a three-way pipe. Furthermore, the first cylinder 21, the second cylinder 41, and the third cylinder 31 are all divided into upper and lower halves, and the detachable connection is achieved by bolts. This not only ensures structural sealing, but also facilitates removal and maintenance of the detector during actual use, further improving the effectiveness of cavitation detection in fluid media.

[0039] The density-based cavitation detection method for pure water hydraulic systems is based on the above density-based cavitation detection device for pure water hydraulic systems, and includes: connecting the tubular body 1 to transfer the fluid medium and passing the fluid medium through the control section; contacting the first slider 22 and the second slider 42 respectively using hydraulic pressure generated in the control section; bringing the first slider 22 into contact with the third slider 32 and acquiring a hydraulic pressure signal by the detection mechanism 3; driving the second slider 42 by hydraulic pressure to close the pipe body 1 and release the hydraulic pressure in the control section; after the hydraulic pressure is removed, the second spring 43 resets the second slider 42 to place the tube 1 in communication with the control section, repeating the steps of passing the fluid medium through the control section; The method includes a step of taking the average value m of the signal peak values ​​within a unit time of several acquired hydraulic signals, taking the minimum value of the signal peak value as n, and determining that cavitation is occurring when n<0.98m, and assuming that cavitation is not occurring in other cases.

[0040] After the fluid medium cavitates in the tubular body 1, the density of the fluid medium changes. Therefore, after passing through the first cylinder 21, the flow rate of the fluid medium and the specifications of the first cylinder 21 and the first slider 22 are constant, so the density of the fluid medium changes, and the strength of the hydraulic action generated on the first slider 22 changes. Due to different magnitudes of acting force, the acting force at which the first slider 22 contacts the third slider 32 varies, and the corresponding electrical signal transmitted from the resistance strain gauge 33 also varies. Then, the second slider 42 is pressed by hydraulic pressure to intermittently block the tubular body 1, thereby realizing adaptive adjustment of the hydraulic pressure using the fluid medium. The hydraulic signal is detected intermittently by the resistance strain gauge 33, and the unit time is set to 10 seconds, for example. The peak value of the resistance strain gauge 33 detected within 10 seconds, i.e., the force with which the hydraulic pressure presses the first slider 22, is recorded, and the difference between the average value of the peak value and the minimum value of the peak value is compared, thereby enabling accurate detection of the occurrence of cavitation in the fluid medium.

[0041] In describing the present invention, it should be understood that any orientation or positional relationship indicated by the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc., is based on the orientation or positional relationship shown in the drawings and is intended only to facilitate the description of the present invention, and is not intended to indicate or imply that the referred to device or element must have a particular orientation, be configured, or operate in a particular orientation, and therefore should not be construed as a limitation of the present invention.

[0042] The above-described embodiments merely illustrate preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical problems of the present invention without departing from the spirit of the design of the present invention should be included in the scope of protection defined by the claims of the present invention. [Explanation of symbols]

[0043] 1. Body 2. Control Mechanism 21 No. 1 cylinder 22 First slider 23 Communication pipe 24 First Spring 25 Column convex part 26 Seal ring 3. Detection mechanism 31 Third cylinder 32 Third slider 33 Resistance strain gauge 4 Closure mechanism 41 No. 2 cylinder 42 Second slider 43 Second Spring 44 Piston structure 5 outer cylinder 6 Outer cylinder upper cover 7 Outer cylinder lower cover

Claims

1. 1. A density-based cavitation detection device for a pure water hydraulic system, comprising: a tube (1) for transporting a fluid medium; a detection mechanism (3) disposed on the tubular body (1), the detection end of which is disposed to intermittently contact the fluid medium to acquire a cavitation signal of the fluid medium; and a blocking mechanism (4) that is slidably fitted within the pipe (1) and that is arranged so that the pipe (1) and the detection mechanism (3) can intermittently switch between a blocked state and a communicating state by hydraulic action generated by the fluid medium.

2. The device further includes a control mechanism (2), wherein a control section communicating with the pipe body (1) is formed within the control mechanism (2); wherein, when the pipe (1) transports a fluid medium and the hydraulic pressure is generated in the control section, the hydraulic pressure is arranged to move the blocking mechanism (4) in a first direction to block the pipe (1), and the hydraulic pressure cooperates with the control end of the control mechanism (2) to contact the detection end; 2. The cavitation detection device for a pure water hydraulic system based on density according to claim 1, wherein when the blocking mechanism (4) blocks the pipe (1) and breaks the hydraulic pressure in the control section, the blocking mechanism (4) can move in a second direction opposite to the first direction to communicate the pipe (1) with the control section.

3. The control mechanism (2) a first cylinder (21) having an internal cavity whose one end communicates with the pipe body (1); a control element that is slidably fitted in the first cylinder (21), and whose control end extends from the first cylinder (21) along the other end away from the pipe body (1) by the hydraulic pressure and contacts the detection end; 3. The cavitation detection device for a pure water hydraulic system based on density according to claim 2, further comprising a communication pipe (23) communicating with the first cylinder (21) and the closing mechanism (4), respectively, and an acting force in the same direction as the first direction is generated in the internal cavity of the communication pipe (23) by the hydraulic pressure, and the acting force acts on the closing mechanism (4).

4. The control element is a first slider (22) that is in sliding contact with the inside of the first cylinder (21), has a seal ring (26) fitted thereon, the seal ring (26) being in sliding contact with the inner wall of the first cylinder (21), and has a column convex portion (25) integrally formed at an upper portion thereof, the column convex portion (25) extending from the first cylinder (21) and contacting the detection end; 4. The cavitation detection device for a pure water hydraulic system based on density according to claim 3, further comprising a first spring (24) wound around the column convex portion (25), and both ends of the first spring (24) being fixed to the first slider (22) and the inner wall surface of the first cylinder (21), respectively.

5. The closing mechanism (4) a second cylinder (41) provided at the tip of the first cylinder (21) and communicating with the pipe body (1) and the communicating pipe (23); a second slider (42) that is slidably fitted into the second cylinder (41), and that has a piston structure (44) integrally formed on the side closer to the communicating pipe (23), and that moves in the first direction in cooperation with the communicating pipe (23) and the piston structure (44) when an acting force in the same direction as the first direction is generated in the communicating pipe (23), thereby closing the pipe body (1); 4. The cavitation detection device for a pure water hydraulic system based on density as claimed in claim 3, further comprising a second spring (43) filled between the piston structure (44) and the communicating pipe (23), both ends of the second spring (43) being fixed to the piston mechanism and the inner wall of the second cylinder (41), respectively.

6. The detection mechanism includes: a third cylinder (31) provided near the control element and having a resistance strain gauge (33) provided therein; and a third slider (32) provided on the third cylinder (31) and in contact with the resistance strain gauge (33), one end of the third slider (32) extending from the third cylinder (31) and in contact with the control end.

7. 7. The cavitation detection device for a pure water hydraulic system based on density according to claim 6, further comprising an outer cylinder (5), an outer cylinder upper cover (6) and an outer cylinder lower cover (7) detachably connected to the outer cylinder (5), the third cylinder (31) being fixed to the outer cylinder (5) by the outer cylinder upper cover (6) / outer cylinder lower cover (7), and the pipe body (1) being drilled inside the outer cylinder (5) and fixed to the outer cylinder (5).

8. 7. The cavitation detection device for a pure water hydraulic system based on density according to claim 6, wherein the first cylinder (21), the second cylinder (41), and the third cylinder (31) all have a detachable connection structure.

9. A method for detecting cavitation in a pure water hydraulic system based on density, based on the cavitation detection device for a pure water hydraulic system based on density according to any one of claims 1 to 6, comprising: connecting the tubular body (1) to transfer the fluid medium and passing the fluid medium through the control section; using hydraulic pressure generated in the control section to act on the first slider (22) and the second slider (42), respectively; bringing the first slider (22) into contact with the third slider (32) and acquiring a hydraulic pressure signal by a detection mechanism (3); driving the second slider (42) to close the pipe body (1) and break the hydraulic pressure in the control section; after the hydraulic pressure is removed, the second spring (43) resets the second slider (42) to place the tube (1) in communication with the control section, and repeats the steps of passing the fluid medium through the control section; a step of determining that cavitation is occurring when n<0.98 m, and otherwise determining that cavitation is not occurring, and taking a value m as the average value of the signal peak values ​​within a unit time of several acquired hydraulic signals, and determining that cavitation is occurring when n<0.98 m, and otherwise determining that cavitation is not occurring.

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