Liquid-driven piston diaphragm compressor

Abstract

The present invention belongs to the field of compressors, and in particular relates to a liquid-driven piston diaphragm compressor, comprising a main oil cylinder (28), a drive system and an oil replenishment system; the main oil cylinder (28) comprises a drive oil cylinder (5), a left transmission oil cylinder (4) and a right transmission oil cylinder (9); the oil circuit input / output port of the drive system is connected to the oil circuit output / input port of the drive oil cylinder (5); the oil replenishment system comprises an oil unloading passage, an oil change passage and an oil replenishment passage; the oil unloading passage comprises a left oil unloading passage (13) and a right oil unloading passage (16); the two ends of the oil change passage are respectively connected to the transmission cylinder tails of the left transmission oil cylinder (4) and the right transmission oil cylinder (9); the oil replenishment passage comprises a left oil replenishment passage (18) and a right oil replenishment passage (17). The present invention has a small size and a simple structure, and can meet the frequent start-stop working conditions of a hydrogen refueling station.

Description

Technical Field

[0001] The present invention belongs to the field of compressors, and in particular relates to a liquid-driven piston diaphragm compressor. Background Art

[0002] The diaphragm compressor is a special type of positive displacement compressor, which is suitable for compressing high-purity, rare and precious, flammable and explosive, toxic and harmful, corrosive and high-pressure gases.

[0003] While diaphragm compressors are widely used to compress hydrogen in hydrogen refueling stations due to their unique structure, which provides a good seal when compressing gas, they are criticized for their large size, complex structure, and inability to effectively meet the frequent start-up and shutdown conditions of hydrogen refueling stations. To address these issues, this project proposes a new structure that uses hydraulic oil to directly drive the piston to reciprocate to compress the gas. This structure is small and simple, and its oil replenishment system has been redesigned to only require two oil circuits for replenishment. Through the design of the hydraulic system, the compressor can be controlled in two operating modes to solve the problem of frequent starts and stops without shutting down. Summary of the Invention

[0004] The purpose of the present invention is to provide a liquid-driven piston diaphragm compressor to solve the problems raised in the above background technology that traditional diaphragm compressors are large in size, complex in structure and cannot well meet the frequent start-stop conditions of hydrogen refueling stations.

[0005] To solve the above-mentioned technical problems, the present invention is achieved as follows:

[0006] A liquid-driven piston diaphragm compressor comprises a main oil cylinder, a drive system and an oil replenishment system;

[0007] The master cylinder includes a driving cylinder, a left transmission cylinder and a right transmission cylinder; a driving piston is provided in the driving cylinder; a left transmission piston is provided in the left transmission cylinder; a right transmission piston is provided in the right transmission cylinder; the left transmission piston and the driving piston, as well as the right transmission piston and the driving piston, are fixedly connected by piston rods; membrane cavities are fixedly provided at both ends of the master cylinder; the transmission cylinder tails of the left transmission cylinder and the right transmission cylinder are respectively communicated with one side of the membrane cavity;

[0008] The oil circuit input / output port of the driving system is connected to the oil circuit output / input port of the driving oil cylinder; the hydraulic oil drives the driving piston to drive the piston rod to reciprocate and drives the diaphragm in the diaphragm cavity to reciprocate through the left driving piston and the right driving piston respectively;

[0009] The oil replenishment system includes an oil unloading passage, an oil changing passage, and an oil replenishment passage;

[0010] The oil unloading passage includes a left oil unloading passage and a right oil unloading passage; the ports of the left oil unloading passage are respectively connected to the transmission cylinder head and the transmission cylinder tail of the left transmission cylinder; the ports of the right oil unloading passage are respectively connected to the transmission cylinder head and the transmission cylinder tail of the right transmission cylinder; check valves are respectively provided on the left oil unloading passage and the right oil unloading passage;

[0011] The two ends of the oil change passage are respectively connected to the tail ends of the left transmission oil cylinder and the right transmission oil cylinder to realize the oil change function;

[0012] The oil replenishment passage includes a left oil replenishment passage and a right oil replenishment passage; the left oil replenishment passage is connected to the transmission cylinder head and the transmission cylinder tail of the left transmission cylinder respectively; the right oil replenishment passage is connected to the transmission cylinder head and the transmission cylinder tail of the right transmission cylinder respectively; check valves are respectively provided on the left oil replenishment passage and the right oil replenishment passage.

[0013] Furthermore, the drive system includes an oil tank, a first oil filter, a hydraulic pump, a relief valve, a cooler, a shut-off valve, a speed regulating valve, a one-way valve and an electro-hydraulic reversing valve; the hydraulic oil enters the first oil filter from the oil tank, is driven by the hydraulic pump to the parallel oil circuit of the shut-off valve and the speed regulating valve, then enters the electro-hydraulic reversing valve through the one-way valve and finally enters the main oil cylinder of the compressor, and the oil is continuously reversed by the electro-hydraulic reversing valve to realize the reciprocating motion of the driving piston in the main oil cylinder of the compressor.

[0014] Furthermore, the drive system is also provided with an overflow valve, a cooler, and a second oil filter; excess oil returns to the oil tank through the overflow valve, the cooler, and the second oil filter.

[0015] Furthermore, the inner diameters of the left transmission cylinder and the right transmission cylinder meet the following conditions:

[0016] Where: D c The inner diameter of the oil cylinder; L is the piston stroke; V c The stroke volume of the transmission cylinder.

[0017] Furthermore, the piston rod diameter and the driving piston diameter satisfy the following condition: d=γD; wherein: d is the piston rod diameter, mm; D is the driving piston diameter, mm; γ is the relationship coefficient between the piston diameter and the piston rod diameter, 0.5≤γ≤0.75.

[0018] The liquid-driven piston diaphragm compressor of the present invention includes a main oil cylinder, an oil replenishment system, a drive system and a multi-host working mode. The oil replenishment system is composed of a membrane cavity, an oil unloading passage, a check valve, an oil change passage and an oil replenishment passage, which can realize automatic oil replenishment. The drive system is composed of an oil tank, an oil filter, a hydraulic pump, an overflow valve, a cooler, a stop valve, a speed regulating valve, a one-way valve, an electro-hydraulic reversing valve and a drive oil cylinder, which can realize the reciprocating motion of the piston. The present invention can increase the number of hosts to increase the exhaust volume through the multi-host working mode. The present invention no longer uses the traditional complex mechanical transmission mode, but uses a hydraulic system to directly drive the reciprocating motion of the piston to realize the compressed gas function. Compared with the traditional diaphragm compressor, the liquid-driven diaphragm compressor of the present invention has a simpler structure and a smaller size, which can meet the frequent start and stop working conditions of the hydrogen filling station. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a working principle diagram of the drive system of the present invention;

[0020] Figure 2 This is the oil replenishment principle diagram of the present invention;

[0021] Figure 3 This is a schematic diagram of the hydraulic principle of a single machine of the present invention;

[0022] Figure 4 This is a schematic diagram of the multi-machine working hydraulic principle of the present invention.

[0023] In the figure: 1. end cover; 2. diaphragm; 3. diaphragm cavity; 4. left transmission cylinder; 5. driving cylinder; 6. driving piston; 7. piston rod; 8. right transmission piston; 9. right transmission cylinder; 10. right oil port; 11. left oil port; 12. left transmission piston; 13. left oil unloading passage; 14. check valve; 15. oil change passage; 16. right oil unloading passage; 17. right oil replenishing passage; 18. left oil replenishing passage; 19 oil tank; 20a. first oil filter; 20b. second oil filter; 21. hydraulic pump; 22. overflow valve; 23. cooler; 24. stop valve; 25. speed control valve; 26. one-way valve; 27. electro-hydraulic reversing valve; 28. master cylinder. DETAILED DESCRIPTION

[0024] In order to make those skilled in the art better understand the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the embodiments described are only a part of the embodiments of the present invention, rather than all embodiments. These embodiments should be understood to be merely illustrative of the present invention and not intended to limit the scope of protection of the present invention. After reading the contents of the present invention, all other embodiments obtained after various modifications or amendments made to the present invention based on the technical solution and embodiments of the present invention also fall within the scope of protection of the claims of the present invention. The experimental methods in the following examples, unless otherwise specified, are conventional methods.

[0025] A liquid-driven piston diaphragm compressor includes a main oil cylinder 28, a drive system and an oil replenishment system; the main oil cylinder 28 includes a drive oil cylinder 5, a left transmission oil cylinder 4 and a right transmission oil cylinder 9; a drive piston 6 is provided in the drive oil cylinder 5; a left transmission piston 12 is provided in the left transmission oil cylinder 4; a right transmission piston 8 is provided in the right transmission oil cylinder 9; the left transmission piston 12 and the drive piston 6, as well as the right transmission piston 8 and the drive piston 6, are fixedly connected by piston rods 7 respectively; a diaphragm cavity 3 is fixedly provided at both ends of the main oil cylinder; the transmission cylinder tails of the left transmission oil cylinder 4 and the right transmission oil cylinder 9 are respectively communicated with one side of the diaphragm cavity 3;

[0026] The oil circuit input / output port of the drive system is connected to the oil circuit output / input port of the drive cylinder 5; the hydraulic oil drives the drive piston 6 to drive the piston rod 7 to reciprocate and drives the diaphragm 2 in the diaphragm cavity 3 to reciprocate through the left drive piston 12 and the right drive piston 8 respectively;

[0027] The oil replenishment system includes an oil unloading passage, an oil changing passage, and an oil replenishment passage;

[0028] The oil unloading passage includes a left oil unloading passage 13 and a right oil unloading passage 16; the ports of the left oil unloading passage 13 are respectively connected to the transmission cylinder head and the transmission cylinder tail of the left transmission cylinder 4; the ports of the right oil unloading passage 16 are respectively connected to the transmission cylinder head and the transmission cylinder tail of the right transmission cylinder 9; check valves 14 are respectively provided on the left oil unloading passage 13 and the right oil unloading passage 16;

[0029] The two ends of the oil change passage are respectively connected to the tail of the transmission cylinder of the left transmission cylinder 4 and the right transmission cylinder 9 to realize the oil change function;

[0030] The oil replenishment passage includes a left oil replenishment passage 18 and a right oil replenishment passage 17; the left oil replenishment passage 18 is connected to the transmission cylinder head and the transmission cylinder tail of the left transmission cylinder 4 respectively; the right oil replenishment passage 17 is connected to the transmission cylinder head and the transmission cylinder tail of the right transmission cylinder 9 respectively; and check valves 14 are respectively provided on the left oil replenishment passage 18 and the right oil replenishment passage 17.

[0031] The drive system of the hydraulic-driven piston diaphragm compressor of the present invention includes an oil tank 19, a first oil filter 20a, a hydraulic pump 21, a relief valve 22, a cooler 23, a shutoff valve 24, a speed regulating valve 25, a check valve 26, and an electro-hydraulic reversing valve 27. Hydraulic oil enters the first oil filter 20a from the oil tank 19, is driven by the hydraulic pump 21 to the parallel oil circuit of the shutoff valve 24 and the speed regulating valve 25, then enters the electro-hydraulic reversing valve 27 through the check valve 26 and finally enters the compressor's main oil cylinder 28. The electro-hydraulic reversing valve 27 continuously reverses the oil flow to achieve reciprocating motion of the driving piston 6 in the compressor's main oil cylinder 28. The drive system of the present invention is also equipped with a relief valve 22, a cooler 23, and a second oil filter 20b. Excess oil returns to the oil tank 19 through the relief valve 22, cooler 23, and second oil filter 20b.

[0032] The inner diameters of the left transmission cylinder 4 and the right transmission cylinder 9 of the present invention meet the following conditions:

[0033] Where: D c The inner diameter of the oil cylinder; L is the piston stroke; V c The stroke volume of the transmission cylinder. The diameter of the piston rod 7 and the diameter of the driving piston 6 in the present invention meet the following conditions: d = γD; where: d is the piston rod diameter, mm; D is the driving piston diameter, mm; γ is the coefficient of the relationship between the piston diameter and the piston rod diameter, 0.5≤γ≤0.75.

[0034] The present invention is mainly applied to 35MPa-class hydrogenation stations. According to the technical specifications of hydrogenation station compressors, the design parameter requirements of the liquid-driven diaphragm compressor are obtained.

[0035] Parameter requirements for liquid-driven diaphragm compressors

[0036]

[0037] series

[0038] When designing a compressor, the first step is to determine the number of compression stages. Choosing the appropriate number of stages has the advantages of lowering the compressor's exhaust temperature, improving volumetric efficiency, reducing and evenly distributing gas forces, and saving energy. The number of stages is determined by the compression ratio. Based on the design requirements, assuming an intake pressure of 12.5 MPa and an exhaust pressure of 35 MPa, calculations show that the compression ratio of a liquid-driven diaphragm compressor is 2.6. Because compression relies on the reciprocating motion of the diaphragm and its structure is simple, a single-unit pressure ratio can reach 8. However, calculations show that the overall compression ratio of the compressor is only 2.6, so the number of stages is determined to be 1.

[0039] Where: ε compression ratio; p d Exhaust pressure, MPa; p s Inspiratory pressure, MPa.

[0040] Air intake

[0041] Based on the exhaust volume of 80Nm under standard conditions (101325Pa, 0℃) 3 / h is converted to the volume flow rate at the compressor inlet state (12.5MPa, 25℃).

[0042] Where: P0 is the pressure under standard conditions; P i Inlet pressure; V0 volume under standard conditions; V i Intake volume; Temperature under T0 standard conditions; T i Intake air temperature.

[0043] Exhaust temperature

[0044] The exhaust temperature is determined by the following formula based on the designed compression ratio

[0045] Where: T d Exhaust temperature; T s Suction temperature; n1 compression process index.

[0046] According to the design requirements, the suction temperature is taken as 298.15K, and the compression process index n1 is taken to be equal to the temperature adiabatic coefficient k of hydrogen. T The temperature adiabatic coefficient of hydrogen is related to the temperature and pressure of the gas. The gas temperature is taken as the suction temperature and the pressure is taken as the inlet pressure. The temperature adiabatic coefficient of hydrogen at 20°C is selected according to the table:

[0047] Hydrogen temperature adiabatic coefficient selection table

[0048]

[0049] Select k T is 1.407, and T is obtained by substituting the value into the formula. d =401.6K, which means that the exhaust temperature without cooling is 128.45°C. However, according to the technical specifications of hydrogen refueling stations, the exhaust temperature shall not exceed 40°C. Therefore, a cooling system must be installed on the compressor.

[0050] Membrane cavity curve

[0051] Before determining the membrane cavity curve, the stroke volume of the diaphragm must be determined first.

[0052] Where: n is the number of reciprocating cycles per minute of the compressor. Take n = 60 and substitute it into the formula to get V h =0.000098m 3The diaphragm cavity is mainly composed of an upper cover plate and a lower support plate. The profile of the cover plate and the support plate is a curve, which ensures that the diaphragm can stick tightly to the profile during the compression process. The design of the profile requires that the diaphragm can have a large volume while ensuring a certain deflection, and that the diaphragm can work under uniform force distribution. During the compression deformation process, the center of the diaphragm deforms more than the peripheral parts. In order to ensure that the stresses on these two parts of the diaphragm are close, the design profile curve should be consistent with the deformation curve of the diaphragm. Therefore, the following formula is the formula of the profile curve in polar coordinates:

[0053]

[0054] The volume enclosed by the profile curve is

[0055]

[0056] Where: W is the deflection of the diaphragm, m; W0 is the maximum deflection of the diaphragm, m. When selecting its value, it is necessary to consider the specific working conditions of the liquid-driven diaphragm compressor, and the final value is 2.6mm; ρ is the ratio of the membrane cavity radius to the diaphragm radius, ρ=rR, r is the membrane cavity radius, R is the diaphragm radius, and the unit is m; z is the deflection index, whose size affects the volume and stress enclosed by the surface and its value is 3. After calculation, the equation of the membrane cavity curve is: Inner diameter of transmission cylinder

[0057] In a liquid-driven diaphragm compressor, in order to ensure that the piston can drive the hydraulic oil to squeeze the diaphragm tightly against the diaphragm cavity cover each time the compressor compresses gas, the piston stroke volume is generally equal to the diaphragm stroke volume during design. The inner diameter of the transmission cylinder is calculated based on the piston stroke volume:

[0058] Where: D c The inner diameter of the oil cylinder; L is the piston stroke; V c The stroke volume of the transmission cylinder is the stroke volume V of the diaphragm. h The inner diameter of the transmission cylinder is 37.2 mm, which is rounded to 38 mm. The diameter of the transmission piston is equal to that of the transmission cylinder.

[0059] piston rod

[0060] The piston rod diameter and piston diameter have a certain relationship. d = γD; where: d is the piston rod diameter, mm; D is the piston diameter, mm. γ is the coefficient of relationship between piston diameter and piston rod diameter, generally ranging from 0.5 to 0.75. Taking γ as 0.5, the piston rod diameter is 19 mm.

[0061] The drive piston and the transmission pistons on either side are connected by a piston rod. Therefore, the diameter of the piston rod can be used to initially determine the drive piston diameter. Based on experience, a preliminary determination of 60mm is made for the drive piston diameter. The inner diameter of the drive cylinder is the same as the drive piston diameter, i.e., 60mm.

[0062] like Figure 1 As shown, the drive system operates as follows: when oil enters the left oil port 11 and exits the right oil port 10, the drive piston 6 moves rightward. The right transmission piston 8 pushes the hydraulic oil to the right, squeezing the diaphragm 2 toward the top of the air chamber, compressing the gas in the air chamber. When the gas reaches exhaust pressure, the exhaust valve opens, completing the exhaust process. The right diaphragm head compresses the gas, while the left diaphragm head inhales air. At this point, the left transmission piston 12 moves rightward, and the oil in the left diaphragm head's oil chamber enters the left transmission cylinder 4. Gas enters the air chamber through the intake valve, squeezing the diaphragm against the bottom of the left diaphragm head's oil chamber, completing the compressor's intake action. When oil enters the right oil port 10 and exits the left oil port 11, the drive piston 6 moves leftward. The left transmission piston 12, right transmission piston 8, and diaphragm 2 interchange their directions of motion, compressing and exhausting the gas in the left diaphragm chamber while inhaling air in the right. The continuous flow of oil from the left and right oil ports 11 and 10 causes the reciprocating motion of the drive piston 6 to achieve the compressor's gas compression operation.

[0063] like Figure 2 As shown, the working principle of the oil replenishment system is that when the right membrane chamber begins to compress the gas and the left membrane chamber begins to take in air, the piston moves to the right. At this time, the left transmission piston 12 pushes the oil through the left oil replenishment passage 18 into the left membrane chamber to complete the oil replenishment, and the remaining oil enters the right transmission cylinder 9 through the oil exchange passage 15. At the same time, the right piston pushes the oil through the right oil unloading passage 16 into the left working chamber of the right transmission cylinder 9 to complete the oil unloading. When the piston moves to the left, the oil is replenished and unloaded in the same way as above. The function of the oil exchange passage 15 is to transfer the oil to another cylinder due to insufficient space when the piston moves to the dead point, to prevent the piston from not working properly due to excessive pressure.

[0064] like Figure 3 As shown, the hydraulic principle of a single machine is that the hydraulic oil enters the first oil filter 20a from the oil tank 19, and is driven to the parallel oil circuit of the shut-off valve 24 and the speed regulating valve 25 by the hydraulic pump 21. The excess oil returns to the oil tank 19 through the overflow valve 22, the cooler 23, and the second oil filter 20b. The oil going to the parallel oil circuit of the shut-off valve 24 and the speed regulating valve 25 will pass through the one-way valve 26 and enter the electro-hydraulic reversing valve 27 and finally enter the compressor 28. The reciprocating motion of the piston in the compressor 28 is realized by the continuous reversal of the oil by the electro-hydraulic reversing valve 27.

[0065] like Figure 3As shown in the figure, the switching principle between the normal and idle working modes is as follows: when the compressor is in the normal working mode, the shut-off valve 24 is normally open, and the oil can enter the electro-hydraulic reversing valve 27 through the parallel oil circuit of the shut-off valve 24 and the speed regulating valve 25, and then drive the piston 6 to perform reciprocating linear motion inside the driving cylinder 5. When the compressor is in the idle working mode, the shut-off valve 24 is closed, and the oil can only pass through the speed regulating valve 25. The speed regulating valve 25 reduces the oil flow rate. At this time, the oil flowing into the electro-hydraulic reversing valve 27 will be reduced, and a signal is applied to the electro-hydraulic reversing valve 27 to reduce its reversing speed. Since the oil flow rate, flow rate, and reversing speed entering the driving cylinder 5 are reduced, the piston reversing frequency is also reduced, thereby reducing the compressor exhaust volume.

[0066] like Figure 4 As shown in the figure, the hydraulic principle of multi-machine operation, since the liquid-driven diaphragm compressor is driven by a hydraulic system, the compressor body does not have an overly complex structure, so its volume is smaller than that of traditional diaphragm compressors, only 650mm×320mm×320mm, which is about a quarter of the volume of traditional diaphragm compressors. Therefore, the liquid-driven diaphragm compressor can increase the number of main units to increase the exhaust volume, for example, the exhaust volume of a single unit is 80Nm 3 / h, when the number of compressors increases to three, the exhaust volume is 240Nm 3 / h, Figure 4 The schematic diagram of the hydraulic system for three main machines.

[0067] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. It should be noted that various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A liquid-driven piston diaphragm compressor, characterized in that: It includes a main oil cylinder (28), a driving system and an oil replenishing system; The master cylinder (28) includes a driving cylinder (5), a left transmission cylinder (4) and a right transmission cylinder (9); a driving piston (6) is provided in the driving cylinder (5); a left transmission piston (12) is provided in the left transmission cylinder (4); a right transmission piston (8) is provided in the right transmission cylinder (9); the left transmission piston (12) and the driving piston (6) as well as the right transmission piston (8) and the driving piston (6) are fixedly connected via piston rods (7); membrane cavities (3) are fixedly provided at both ends of the master cylinder; the tail ends of the transmission cylinders of the left transmission cylinder (4) and the right transmission cylinder (9) are respectively communicated with one side of the membrane cavity (3); The oil circuit input / output port of the driving system is in communication with the oil circuit output / input port of the driving oil cylinder (5); the driving piston (6) is driven by the hydraulic oil to drive the piston rod (7) to reciprocate and the diaphragm (2) in the diaphragm cavity (3) is driven to reciprocate through the left driving piston (12) and the right driving piston (8); The oil replenishment system includes an oil unloading passage, an oil changing passage, and an oil replenishment passage; The oil unloading passage comprises a left oil unloading passage (13) and a right oil unloading passage (16); the ports of the left oil unloading passage (13) are respectively connected to the transmission oil cylinder head and the transmission oil cylinder tail of the left transmission oil cylinder (4); the ports of the right oil unloading passage (16) are respectively connected to the transmission oil cylinder head and the transmission oil cylinder tail of the right transmission oil cylinder (9); check valves (14) are respectively provided on the left oil unloading passage (13) and the right oil unloading passage (16); The two ends of the oil change passage are respectively connected to the tail ends of the left transmission oil cylinder (4) and the right transmission oil cylinder (9) to realize the oil change function; The oil replenishment passage comprises a left oil replenishment passage (18) and a right oil replenishment passage (17); the left oil replenishment passage (18) is connected to the transmission oil cylinder head and the transmission oil cylinder tail of the left transmission oil cylinder (4); the right oil replenishment passage (17) is connected to the transmission oil cylinder head and the transmission oil cylinder tail of the right transmission oil cylinder (9); and check valves (14) are respectively provided on the left oil replenishment passage (18) and the right oil replenishment passage (17).

2. The liquid-driven piston diaphragm compressor according to claim 1, characterized in that: The driving system comprises an oil tank (19), a first oil filter (20a), a hydraulic pump (21), a stop valve (24), a speed regulating valve (25), a one-way valve (26) and an electro-hydraulic reversing valve (27); the hydraulic oil enters the first oil filter (20a) from the oil tank (19), is driven to the parallel oil circuit of the stop valve (24) and the speed regulating valve (25) by the hydraulic pump (21), then enters the electro-hydraulic reversing valve (27) through the one-way valve (26) and finally enters the main oil cylinder (28) of the compressor, and the oil is continuously reversed by the electro-hydraulic reversing valve (27) to realize the reciprocating motion of the driving piston (6) in the main oil cylinder (28) of the compressor.

3. The liquid-driven piston diaphragm compressor according to claim 2, characterized in that: The driving system is further provided with an overflow valve (22), a cooler (23) and a second oil filter (20b); excess oil returns to the oil tank (19) through the overflow valve (22), the cooler (23) and the second oil filter (20b).

4. The liquid-driven piston diaphragm compressor according to claim 3, characterized in that: The inner diameters of the left transmission oil cylinder (4) and the right transmission oil cylinder (9) meet the following conditions: Where: D c The inner diameter of the oil cylinder; L is the piston stroke; V c The stroke volume of the transmission cylinder.

5. The liquid-driven piston diaphragm compressor according to claim 4, characterized in that: The diameter of the piston rod (7) and the diameter of the driving piston (6) satisfy the following condition: d=γD; wherein: d is the piston rod diameter, mm; D is the driving piston diameter, mm; γ is the coefficient of relationship between the piston diameter and the piston rod diameter, 0.5≤γ≤0.75.

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