Liquid-cooled oil-free air compressor

Abstract

The invention discloses a liquid-cooled oil-free air compressor, which relates to the technical field of vehicle-mounted new energy vehicles or medical industry, and comprises a motor, a crankshaft box body, a piston assembly, a cylinder cover, a valve plate assembly, an independent closed-loop liquid cooling system and a mechanical self-unloading valve, the liquid cooling system comprises an oil tank, an oil pump assembly directly connected and driven by a power shaft of the air compressor, a cooling flow channel arranged around a piston cylinder and a connecting pipeline, and a cooling liquid circulation loop independent of the external environment is formed. The mechanical self-unloading valve is arranged between the air inlet channel and the air outlet channel and used for automatically conducting the air inlet channel and the air outlet channel when the air compressor is shut down so as to achieve pressure relief and no-load starting. The technical problems that internal condensate water is generated due to temperature difference changes, abrasion, dust pollution and system compatibility risks are aggravated due to high-temperature creep deformation of self-lubricating materials such as a piston ring, and on-load starting is difficult due to the fact that high pressure exists in a cavity after shutdown are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle-mounted new energy vehicles or medical industry, and particularly relates to a liquid-cooled oil-free air compressor. BACKGROUND

[0002] The oil-free piston air compressor has been widely used in many fields due to its high air cleanliness. However, there are still some problems to be solved in the prior art: condensate water problem: in the intermittent working and large load rate changing scene such as vehicle-mounted, the temperature difference in the air compressor is large, which is easy to produce condensate water. The accumulation of condensate water will cause internal component corrosion, lubrication failure, and even backflow and air path pollution. High temperature and wear problem: in the scene such as medical treatment which needs long time continuous work, the high temperature generated by the friction between the piston ring and the cylinder wall will cause the creep of the composite piston ring, aggravate the wear, reduce the service life, and at the same time, increase the exhaust temperature, reduce the volumetric efficiency and increase the energy consumption. Dust pollution problem: the vehicle-mounted environment is harsh, once the external air filter fails, the dust entering the machine body will sharply accelerate the wear of the piston ring and other moving parts. System dependency and risk: the existing liquid cooling scheme mostly depends on the external cooling system (such as vehicle-mounted cooling circulation), which cannot independently and accurately control the temperature according to the needs of the air compressor, and there are risks such as poor compatibility of cooling liquid, pipeline corrosion, uncontrolled lack of liquid, etc. Unloading and pollution problem: there is high pressure in the cavity after the traditional air compressor stops, which makes it difficult to start with load. The crankcase is usually closed or directly discharged, the former causes the internal pressure to be too high to increase the running resistance, and the latter is easy to make the external pollutants enter the machine body. Therefore, there is an urgent need for an oil-free air compressor which can realize constant temperature operation, effectively manage condensate water and dust, and has an independent and reliable cooling system. SUMMARY

[0003] The present application provides a liquid-cooled oil-free air compressor to solve the technical problems of internal condensate water caused by temperature difference change, aggravation of wear of self-lubricating materials such as piston ring due to high temperature creep, dust pollution, system compatibility risk and high pressure in the cavity after stopping, which makes it difficult to start with load.

[0004] To solve the above problems, the technical scheme provided by the present application is as follows:

[0005] A liquid-cooled oil-free air compressor, comprising a motor, a crankcase, a piston assembly, a cylinder head, a valve plate assembly, and further comprising an independent closed-loop liquid cooling system and a mechanical self-unloading valve;

[0006] The liquid cooling system comprises an oil tank, an oil pump assembly driven by the air compressor power shaft, a cooling flow channel arranged around the piston cylinder, and a connecting pipeline, which constitutes a cooling liquid circulation loop independent of the external environment;

[0007] The mechanical self-unloading valve is arranged between the air inlet channel and the air outlet channel, and is used for automatically connecting the air inlet channel and the air outlet channel to realize pressure relief and no-load starting when the air compressor stops.

[0008] The core function of the independent closed-loop liquid cooling system is to actively and accurately control the working temperature of the piston cylinder. It solves the core problems of high temperature creep, efficiency decline, and condensate growth caused by friction in the oil-free air compressor, ensuring that the machine operates in an optimal constant temperature state, thereby improving reliability, service life, and energy efficiency.

[0009] Mechanical self-unloading valve: Its core function is to realize automatic pressure relief when the machine stops. This ensures that the air compressor can start every time in a no-load state, greatly reducing the starting current and the impact on the motor and transmission components, while prolonging the service life of the equipment. Excess gas backflushing cools the powder metallurgy metal strip and reduces the risk of pore clogging. After unloading, the inlet and outlet are connected to the atmosphere, which can avoid the problem of liquid accumulation.

[0010] As an option, the self-unloading valve includes a valve cavity and a free piston arranged in the valve cavity; a hole is formed in the wall of the valve cavity to connect the air inlet channel and the air outlet channel;

[0011] When the air compressor is running, the free piston moves under pressure and blocks the hole;

[0012] When the air compressor stops running, the free piston moves under gravity and connects the hole.

[0013] The design of the free piston and the hole provides a reliable and externally controlled pressure relief function, with simple structure, rapid response, and reliable operation.

[0014] As an option, the bottom of the crankcase is provided with a one-way diaphragm breathing hole, and the one-way diaphragm is fastened to one side of the breathing hole by a fixing bolt. The breathing hole opens to exhaust when the pressure in the crankcase rises, and closes to seal when the pressure decreases or stops.

[0015] The function of the one-way diaphragm breathing hole is intelligent pollution control and air permeation under bidirectional isolation. It allows the internal water vapor containing wear dust to be discharged when the pressure is positive, but effectively prevents external dust, moisture, and other pollutants from entering the internal body when the pressure is negative or when the machine stops. It solves the problems of dust management and water accumulation.

[0016] As an option, the self-unloading valve has a slantingly arranged connecting hole. When the hole is connected, the gas flows from the air outlet channel to the air inlet channel in reverse, forming a backflushing cleaning effect on the air inlet channel.

[0017] The design of the oblique venting channel enables the vented gas to flow in a specific direction. Its function is beyond simple pressure relief, adding the value of "back-blowing cleaning", which can effectively blow off the dust accumulated on the air inlet channel and filter material, keeping the air inlet smooth.

[0018] As an option, a gas-liquid pressure relief mechanism is arranged on the pipeline between the outlet of the oil pump assembly and the low-position oil inlet of the cooling flow channel, for removing the gas in the cooling liquid circulation loop.

[0019] The function of the gas-liquid pressure relief mechanism is to remove the air (bubbles) in the closed liquid cooling circulation system. The presence of air can cause "air blockage", hindering the flow of cooling liquid and seriously affecting the cooling efficiency, even causing local overheating. This mechanism is a key auxiliary device to ensure the efficient and stable operation of the liquid cooling system.

[0020] As an option, a groove or channel for backflow is arranged on the free piston of the self-unloading valve or the bottom of the valve cavity.

[0021] The function of the groove or channel for backflow is to guide the backflow of the cooling liquid. When the air compressor is stopped for a long time, the cooling liquid in the cylinder cooling flow channel and pipeline at the high position needs to flow back to the oil tank slowly through the unloading valve cavity under the action of gravity, preventing the cooling liquid from stagnating and causing starting difficulties, corrosion or liquid impact phenomenon.

[0022] As an option, the oil pump assembly is a gear pump, the inlet of which is connected to the oil tank through an oil suction pipe, and the outlet is connected to the low-position oil inlet of the cooling flow channel, and the high-position oil outlet of the cooling flow channel is connected to the oil tank through an oil return pipe.

[0023] The gear pump has the advantages of compact structure, good self-priming, low cost, and direct connection with the shaft. The design of low-position oil inlet and high-position oil outlet is beneficial to utilizing the principle of thermal convection, enhancing the cooling efficiency and helping the system to exhaust.

[0024] As an option, a heat dissipation structure is arranged outside the crankcase, the air compressor further comprises a fan assembly directly driven by the power shaft, and a wind deflector is arranged outside the fan, the wind deflector guides the airflow to the oil tank and the pump head area.

[0025] The heat dissipation structure, fan assembly and wind deflector together constitute an auxiliary heat dissipation system. Its function is to forcibly air-cool the backflowing hot cooling liquid, accelerate its cooling, and ensure that the cooling liquid entering the next cycle has sufficient cooling capacity, thereby maintaining the efficiency of the entire liquid cooling system.

[0026] As an option, a powder metallurgy filter is arranged in the air inlet channel.

[0027] The function of the powder metallurgy filter is secondary precision filtration and auxiliary cooling. After the air filter, the final stage of purification of the intake air is carried out, and it is ensured that extremely clean air enters the compression chamber. Its porous characteristics and metal material also enable it to absorb part of the intake air heat, thereby playing a preliminary cooling role.

[0028] As an option, all cooling liquid channels of the liquid cooling system are provided with isolation structures between the air path channels of the air compressor, and there is no fluid exchange.

[0029] The function of the isolation structure is to absolutely ensure the separation of the air path and the liquid path. This is the fundamental guarantee for realizing "oil-free air" output, preventing the cooling liquid from entering the compression chamber due to seal failure and other reasons, and polluting the output air, which is crucial for medical, food and other application scenarios.

[0030] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0031] Constant temperature and high efficiency: independent liquid cooling system for precise temperature control, completely solves the condensate problem, significantly reduces wear and tear, and improves volumetric efficiency and service life.

[0032] Clean and reliable: mechanical unloading valve realizes no-load start and back flushing cleaning; bottom breathing hole effectively discharges dust and prevents water accumulation, ensuring internal cleanliness and dryness.

[0033] Energy saving and safety: unloading no-load start reduces energy consumption; liquid path and air path are completely isolated, absolutely ensuring the purity of the output air without oil, meeting the high requirements of medical, food and other scenes.

[0034] Integrated intelligence: all functions are directly driven by the host without external control, compact structure, reliable operation, especially suitable for vehicle-mounted, medical and other fields with high space and reliability requirements. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A structure diagram of a liquid-cooled oil-free air compressor is provided for an embodiment of the present application;

[0036] Figure 2 A side view cross-sectional view of a liquid-cooled oil-free air compressor is provided for an embodiment of the present application;

[0037] Figure 3 An oblique view cross-sectional view of a liquid-cooled oil-free air compressor is provided for an embodiment of the present application;

[0038] Figure 4 A cross-sectional view of a self-unloading valve of a liquid-cooled oil-free air compressor is provided for an embodiment of the present application;

[0039] Figure 5A structure diagram of a free piston of a liquid-cooled oil-free air compressor according to an embodiment of the present application;

[0040] Figure 6 An internal structure diagram of an oil pump assembly of a liquid-cooled oil-free air compressor according to an embodiment of the present application;

[0041] Figure 7 A structure diagram of a breathing hole of a liquid-cooled oil-free air compressor according to an embodiment of the present application;

[0042] Figure 8 A multi-stage compression gas flow diagram of a liquid-cooled oil-free air compressor according to an embodiment of the present application;

[0043] Figure 9 A one-stage compression gas flow diagram of a liquid-cooled oil-free air compressor according to an embodiment of the present application;

[0044] 1, cylinder head; 2, valve plate assembly; 3, piston assembly; 4, wind deflector; 5, crankcase; 6, connecting rod assembly; 7, fan assembly; 8, first sealing oil seal; 9, oil pump assembly; 10, second sealing oil seal; 11, bearing; 12, oil suction pipe; 13, oil return pipe; 14, motor; 15, damping column; 16, air inlet; 17, air passage; 18, oil level gauge; 19, liquid level mirror; 20, oil tank; 21, breathing hole; 22, one-way diaphragm; 23, fixing bolt; 24, limit pin; 25, eccentric wheel; 26, rotor; 27, stator; 28, oil outlet; 29, oil inlet; 30, powder metallurgy filter material; 31, free piston; 32, guide ring; 33, sealing ring; 34, air inlet passage; 35, air outlet passage. DETAILED DESCRIPTION

[0045] For further understanding of the present application, the present application is described in detail with reference to the accompanying drawings and embodiments.

[0046] Embodiment 1

[0047] With reference to the accompanying drawings Figures 1-3A liquid-cooled oil-free air compressor, comprising a motor 14, a crankcase 5, a piston assembly 3, a cylinder head 1, a valve plate assembly 2, and further comprising an independent closed-loop liquid cooling system and a mechanical unloading valve. The piston assembly 3 is connected to the output shaft of the motor 14 through a connecting rod assembly 6, which includes an eccentric wheel structure that can convert the rotation of the output shaft into vertical jumping and drive the piston assembly 3 to move up and down. The output shaft of the motor 14 is rotatably connected to the crankcase 5 through a bearing 11, and the outer side of the bearing 11 is provided with a second sealing oil seal 10. The bottom of the crankcase 5 is provided with a circumferentially arranged damping column 15 made of soft material. The crankcase 5 is a symmetrical double compression chamber structure, and an air passage 17 is arranged between the compression chambers for communication. It can be used for one-stage compression air or multi-stage compression air, such as the attached Figure 8 、 9 。

[0048] The liquid cooling system comprises an oil tank 20, an oil pump assembly 9 driven by the air compressor power shaft, a cooling flow channel arranged around the piston cylinder, and a connecting pipeline, forming a cooling liquid circulation loop independent of the external environment. The oil tank 20 is provided with an oil gauge 18 and a liquid level mirror 19.

[0049] Combined with the attached Figure 4 、 5 , 6, the mechanical unloading valve is arranged between the air inlet passage 34 and the air outlet passage 35, and is used for automatically conducting the air inlet passage and the air outlet passage 35 to realize pressure relief and no-load start when the air compressor stops.

[0050] Liquid cooling system: when the system is running, the oil pump assembly 9 (such as a gear pump) driven by the air compressor power shaft directly from the oil tank 20 absorbs the cooling liquid, which is pumped into the cooling flow channel (such as a spiral water jacket or a surrounding cavity) arranged around the piston cylinder in the crankcase 5 through the pipeline. After the cooling liquid absorbs the heat of the cylinder wall, it returns to the oil tank 20 through the return pipeline. The oil tank 20 can be externally attached to a heat sink and cooled by air cooling to form an independent circulation that does not depend on external water sources.

[0051] Unloading valve: the valve is a pure mechanical structure, usually installed on the cylinder head 1 or the valve plate assembly 2, and connects the air inlet passage 34 and the air outlet passage 35. There is a movable free piston 31 or valve in the valve. When the system stops, the pressure disappears, and the valve core falls under the action of gravity or spring force, opening a passage to allow the remaining high-pressure gas in the compression chamber to be discharged to the air inlet 16 or the atmosphere, thereby achieving pressure relief.

[0052] The unloading valve comprises a valve cavity and a free piston 31 arranged in the valve cavity; a hole is formed in the wall surface of the valve cavity to connect the air inlet passage 34 and the air outlet passage 35;

[0053] When the air compressor is running, the free piston 31 moves under the action of pressure and blocks the hole;

[0054] When the air compressor stops running, the free piston 31 moves under the action of gravity and opens the channel.

[0055] Running state: When the air compressor is running, the pressure generated by the compressed gas or the cooling liquid acts on the lower side (or a specific pressure-bearing surface) of the free piston 31, overcoming its gravity or spring force, and pushing it upward, thereby tightly blocking the hole on the valve cavity wall, and isolating the intake and exhaust passages 35.

[0056] Shutdown state: When the machine is shut down, the pressure drops rapidly, and the free piston 31 loses the upward support force and falls downward under the action of its own gravity (or the spring force in the design), thereby exposing the hole, connecting the high-pressure end of the exhaust passage 35 with the low-pressure end of the intake passage 34 through the hole, and achieving pressure relief.

[0057] The head of the free piston 31 abuts against the intake passage 34 and the exhaust passage 35, and the tail of the free piston 31 is connected to the oil pump assembly 9, and the free piston 31 is controlled by the pressure of the cooling liquid. The chamber where the free piston 31 is located is provided with a guide ring 32 and a sealing ring 33, which cooperate with the peripheral side of the free piston 31 to guide and seal.

[0058] In combination with the attached Figure 7 The bottom of the crankcase 5 is provided with a one-way diaphragm 22 type breathing hole 21, and the one-way diaphragm 22 is fastened to one side of the breathing hole 21 by a fixing bolt 23. The breathing hole 21 opens to exhaust when the pressure in the crankcase rises, and is closed and sealed by the external air pressure when the pressure decreases or stops.

[0059] A hole is processed at the bottom of the crankcase 5, and a one-way diaphragm 22 made of rubber or silicone material is covered on the hole, and a fixing bolt 23 (or a pressing plate) with a central hole is used to fasten the periphery of the diaphragm, and the central part can be blown open by airflow.

[0060] When the piston moves and the pressure in the crankcase rises, the gas pushes the central part of the diaphragm to discharge. When the pressure decreases or remains unchanged, the external atmospheric pressure tightly presses the flexible diaphragm on the mounting surface, forming a reliable seal.

[0061] The open channel of the self-unloading valve is arranged obliquely, and when the channel is open, the gas flows reversely from the exhaust passage 35 to the intake passage 34, forming a reverse blowing cleaning for the intake passage 34.

[0062] On the valve cavity wall of the self-unloading valve, instead of simply drilling a straight hole, a slanted hole with a certain angle is processed, and the opening direction of the hole points to the flow direction of the intake port 16.

[0063] When the unloading valve is open, high pressure gas from the outlet side is jetted to the inlet side through the inclined hole at high speed, forming a reverse jet flow. This jet flow can flush the powder metallurgy filter 30 or the inner wall of the inlet pipe, playing a self-cleaning role.

[0064] A gas-liquid pressure relief mechanism is arranged on the pipeline between the outlet of the oil pump assembly 9 and the low-position oil inlet 29 of the cooling flow channel, for discharging gas in the cooling liquid circulation loop. The mechanism can be an automatic air vent valve, which is usually installed at the highest point of the circulation pipeline or near the outlet of the oil pump. Inside the valve, there is a floating ball valve. When the cavity is filled with liquid, the floating ball floats up to close the air vent. When gas accumulates, the floating ball falls to open the air vent to discharge the gas.

[0065] At the initial stage of system operation or when air is mixed in, gas accumulates at the top of the pressure relief mechanism, and the valve automatically opens the air vent. After the liquid fills up, the valve automatically closes to ensure that the circulation loop is always filled with cooling liquid.

[0066] A groove or channel for backflow is arranged on the free piston 31 of the unloading valve or at the bottom of the valve cavity.

[0067] This feature can be realized in two positions: a few fine vertical grooves are machined on the side wall of the free piston 31; or a few fine channels are machined at the bottom of the valve cavity.

[0068] When the free piston 31 falls to the closed state at the bottom, the grooves or channels are not completely sealed, forming a very small and limited flow cross section. This cross section is sufficient to allow cooling liquid to slowly flow back to the oil tank 20 under the action of gravity, but it is small enough that the leakage of high-pressure gas or liquid during normal operation of the air compressor can be ignored.

[0069] The oil pump assembly 9 is a gear pump, the inlet of which is connected to the oil tank 20 through the oil suction pipe 12, and the outlet is connected to the low-position oil inlet 29 of the cooling flow channel. The high-position oil outlet 28 of the cooling flow channel is connected to the oil tank 20 through the oil return pipe 13. The oil pump assembly 9 is provided with a limit pin 24, and the inner part of the eccentric wheel 25 is provided with a rotor 26. The inner ring of the rotor 26 is provided with a tooth groove and is eccentrically engaged with a stator 27. The oil pump assembly 9 is provided with an oil outlet 28 at the top and an oil inlet 29 at the bottom.

[0070] A typical gear pump is directly installed on the power shaft inside the crankcase. The oil suction pipe 12 sucks oil from the bottom of the oil tank 20. The low-position oil inlet 29 of the cooling flow channel is usually arranged at the lower part of the piston cylinder, and the high-position oil outlet 28 is arranged at the upper part.

[0071] The rotation of the oil pump generates negative pressure, sucking oil from the oil tank 20 and pumping it into the bottom of the cooling flow channel. After absorbing heat in the flow channel, the cooling liquid becomes lighter and naturally rises, flowing out from the top oil outlet 28, completing the circulation with the help of the pumping force and thermal siphon effect.

[0072] The crankcase 5 is externally provided with a heat dissipation structure, and the air compressor further comprises a fan assembly 7 directly driven by the power shaft and a wind deflector 4 covering the fan. The wind deflector 4 guides the airflow to the oil tank 20 and the pump head area. The root of the fan assembly 7 is provided with a first sealing oil seal 8.

[0073] The heat dissipation structure is usually a fin cast on the outer wall of the oil tank 20. The fan assembly 7 is a centrifugal or axial fan installed on the motor 14 or the other end (non-pump end) of the crankshaft. The wind deflector 4 is a plastic or metal shell that precisely guides the airflow generated by the fan to the surface of the oil tank 20 covered with heat dissipation fins.

[0074] The power shaft directly drives the fan to rotate, generating high-speed airflow. The wind deflector 4 restricts the airflow to concentrate on blowing through the surface of the heat dissipation fins of the oil tank 20, greatly enhancing the heat exchange efficiency between the heat dissipation fins and the air, thereby quickly removing the heat from the cooling liquid.

[0075] The powder metallurgy filter material 30 is arranged in the air inlet channel 34.

[0076] The filter material is usually a sintered metal cylinder or block installed at the air inlet 16 of the air inlet manifold or valve plate assembly 2.

[0077] When air passes through its micron-sized tiny pores, particles such as dust are effectively intercepted. At the same time, the intake air exchanges heat with the metal filter material, which has a large surface area and good thermal conductivity, and the heat is partially transferred and dissipated through the filter material shell.

[0078] All cooling liquid channels of the liquid cooling system are provided with isolation structures from the air path channels of the air compressor, without fluid exchange.

[0079] This "isolation" is not a separate part, but the final result of the entire system design. It is achieved through a series of designs: high-efficiency shaft seals (such as mechanical seals) are used for dynamic sealing at the location where the power shaft passes through the cylinder; all related cavities, pipelines and connections have inherent structural integrity and do not have holes or defects that connect the air path and the liquid path.

[0080] Through precise mechanical design and manufacturing process, two completely independent closed-loop systems (air path compression cycle and liquid path cooling cycle) are physically formed, completely eliminating the possibility of mixing of the two media.

[0081] Cooling system working process: motor 14 drives oil pump assembly 9 (a double gear pump) and fan assembly 7 through power shaft. Oil pump sucks cooling liquid from oil tank 20 (integrated in bottom cover or independent component) through suction pipe 12, pumps it into cooling flow channel processed in the inside of crankcase 5, around the piston cylinder. Cooling liquid enters from low inlet 29, flows through the cylinder wall to take away heat, and then flows out from high outlet 28, returns to oil tank 20 through return pipe 13. The heat of the returned cooling liquid is assisted by the heat dissipation fins outside the oil tank 20 and the airflow generated by the fan, completing an independent closed-loop cooling cycle.

[0082] Self-unloading valve working process: there is a small inclined hole on the valve body of the unloading valve, which connects the inlet channel 34 and the outlet channel 35. A free piston 31 is arranged in the valve cavity. During operation, the system pressure (or cooling liquid pressure) pushes the free piston 31 upward to block the communication hole. When the machine stops, the pressure disappears, and the free piston 31 falls under the action of gravity and the residual gas pressure at the outlet, the communication hole is opened, realizing: a) high-pressure gas pressure relief to the inlet 16, realizing no-load start; b) the reverse blowing cleaning of the inlet pipeline and the powder metallurgy filter material 30 by the pressure relief gas; c) providing an evaporation channel for the condensed water.

[0083] Breather hole 21 working process: a hole is opened at the bottom of the crankcase 5, covering a one-way rubber diaphragm 22. During operation, the reciprocating motion of the piston causes the pressure in the crankcase to fluctuate. When the pressure is positive, the diaphragm is pushed away, and the gas containing oil mist and wear dust is discharged; when the pressure is negative or the machine stops, the diaphragm is tightly closed under the action of atmospheric pressure, preventing external pollutants and moisture from entering.

[0084] The above describes the present application and its embodiments in a schematic manner, which is not limited, and the drawings only show one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it, without departing from the purpose of the present application, similar structural modes and embodiments can be designed without creativity, which should belong to the protection scope of the present application.

Claims

1. A liquid-cooled oil-free air compressor, comprising a motor, crankcase, piston assembly, cylinder head, and valve plate assembly, characterized in that, It also includes an independent closed-loop liquid cooling system and a mechanical self-unloading valve; The liquid cooling system includes an oil tank, an oil pump assembly directly driven by the air compressor power shaft, a cooling channel arranged around the piston cylinder, and connecting pipes, forming a coolant circulation loop independent of the external environment. The mechanical self-unloading valve is located between the air inlet channel and the air outlet channel, and is used to automatically open the air inlet and outlet channels when the air compressor stops to achieve pressure relief and no-load start-up.

2. The liquid-cooled oil-free air compressor according to claim 1, characterized in that, The self-unloading valve includes a valve chamber and a free piston disposed within the valve chamber; the wall of the valve chamber is provided with a channel connecting the air inlet channel and the air outlet channel. When the air compressor is running, the free piston moves under pressure and blocks the passage; When the air compressor stops running, the free piston moves under the action of gravity and opens the passage.

3. A liquid-cooled oil-free air compressor according to claim 1 or 2, characterized in that, The bottom of the crankcase is provided with a one-way diaphragm-type vent. The one-way diaphragm is fastened to one side of the vent by fixing bolts. The vent opens to exhaust when the pressure inside the crankcase increases, and closes and seals when the pressure decreases or the machine stops due to external air pressure.

4. A liquid-cooled oil-free air compressor according to claim 2, characterized in that, The self-unloading valve has obliquely arranged guide channels. When the channels are open, the gas flows in the opposite direction from the outlet channel to the inlet channel, forming a backflushing cleaning of the inlet channel.

5. A liquid-cooled oil-free air compressor according to claim 4, characterized in that, A gas-liquid pressure relief mechanism is provided on the pipeline between the outlet of the oil pump assembly and the low-position oil inlet of the cooling channel to remove gas from the coolant circulation loop.

6. A liquid-cooled oil-free air compressor according to claim 2, characterized in that, The self-unloading valve has a groove or channel for backflow on the free piston or at the bottom of the valve chamber.

7. A liquid-cooled oil-free air compressor according to claim 1, characterized in that, The oil pump assembly is a gear pump, with its inlet connected to the oil tank via an oil suction pipe, its outlet connected to the low-level oil inlet of the cooling channel, and the high-level oil outlet of the cooling channel connected to the oil tank via a return oil pipe.

8. A liquid-cooled oil-free air compressor according to claim 1, characterized in that, The crankcase is provided with a heat dissipation structure on the outside, and the air compressor also includes a fan assembly directly driven by the power shaft and an air guide cover covering the fan.

9. A liquid-cooled oil-free air compressor according to claim 1, characterized in that, The air intake channel is equipped with powder metallurgy filter material.

10. A liquid-cooled oil-free air compressor according to claim 1, characterized in that, All coolant passages in the liquid cooling system are isolated from the air compressor's air passages, preventing fluid exchange.

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