Semi-closed reciprocating refrigeration compressor for ammonia

Abstract

The invention discloses a semi-closed reciprocating refrigeration compressor for ammonia, and relates to the technical field of refrigeration. Comprising a semi-closed machine shell, and a compression mechanism and a driving motor which are arranged in the machine shell. A stator winding of the driving motor is made of an aluminum or aluminum alloy material so as to resist corrosion of an ammonia refrigerant; the compression mechanism is of a reciprocating piston type structure; in addition, the driving motor directly drives the reciprocating piston type compression structure to operate, and a traditional shaft seal and a traditional coupler are omitted. The crankshaft also serves as a motor shaft, and direct connection driving is achieved. And integrally-formed radiating fins are arranged at the position, corresponding to the motor, outside the shell so as to enhance the radiating and structural strength. And the air suction port is communicated to the motor cavity, so that low-temperature ammonia gas flows through the motor to cool the motor before being compressed. The invention effectively solves the problems of ammonia corrosion and leakage, has the advantages of high sealing property, high transmission efficiency, low operation noise and the like, is particularly suitable for ammonia refrigeration scenes with medium and small cooling capacity and high pressure ratio, and fills the technical blank in the field.

Description

Technical Field

[0001] This invention relates to the field of refrigeration compressor technology, and specifically to a semi-hermetic reciprocating piston refrigeration compressor. Background Technology

[0002] Ammonia, as a natural refrigerant, boasts advantages such as high refrigeration capacity per unit volume, high coefficient of performance (COP), and low price. Furthermore, its ozone depletion potential and global warming potential are both zero, making it an internationally recognized environmentally friendly refrigerant. However, ammonia is toxic, flammable, and has a strong, pungent odor; leaks can harm human health and the surrounding environment. In addition, ammonia has a severe corrosive effect on copper and copper alloys, making traditional semi-hermetic or hermetic compressors using copper enameled wire as motor windings unsuitable for direct application in ammonia refrigeration systems.

[0003] For a long time, to avoid ammonia corrosion of the motor windings, ammonia refrigeration compressors have mainly adopted an open structure. That is, the compressor and motor are separate, with the motor located outside the refrigeration system and driving the compressor main shaft via a coupling or belt. While this open structure avoids the motor corrosion problem, it has significant drawbacks: High risk of leakage: The open structure requires a shaft seal, i.e. a mechanical seal, to be installed where the main shaft passes through the housing. The shaft seal is a dynamic sealing component, and with wear or aging during operation, ammonia leakage is very likely to occur, causing safety hazards.

[0004] Large size and complex installation: It requires a huge base to install the motor and compressor, and precise alignment and adjustment are required, resulting in a large footprint.

[0005] High operating noise: The combined noise from the coupling drive and the external motor fan results in high overall machine operating noise.

[0006] To address these issues, the industry has begun exploring semi-hermetic ammonia compressor technology. Existing technologies include solutions that utilize ammonia-resistant materials to improve motor windings. For example, Chinese patent document CN203430779U discloses a semi-hermetic variable frequency high-speed screw refrigeration compressor for ammonia. By directly connecting an aluminum coil permanent magnet variable frequency motor to the screw compressor and leveraging the ammonia corrosion resistance of aluminum, a semi-hermetic design is achieved in the ammonia compressor, solving the shaft seal leakage problem.

[0007] However, the aforementioned existing technologies still have the following limitations and shortcomings: Existing technologies have limitations, with almost all using screw compressors. While screw compressors are highly efficient at large displacements, their efficiency drops significantly in small to medium refrigeration capacities due to increased leakage between the screw rotors. Therefore, screw compressors are not the optimal choice for small to medium power commercial refrigeration and auxiliary cooling applications.

[0008] Existing technologies have high processing costs and high maintenance barriers. The rotor profile of screw compressors is complex, with a double-sided asymmetric circular arc envelope, requiring extremely high processing precision, which leads to high manufacturing costs.

[0009] Existing technologies face sealing and energy efficiency issues. Screw compressors primarily rely on oil injection to seal rotor clearances, resulting in a complex oil circuit system. In contrast, reciprocating piston compressors have inherent advantages in terms of technological maturity, manufacturing costs, and sealing performance under high-pressure conditions. Especially in low-temperature applications in small and medium-sized cold storage facilities and cascade refrigeration systems, piston compressors still dominate.

[0010] In summary, existing technologies lack a semi-hermetic ammonia refrigeration compressor that can solve both ammonia corrosion and shaft seal leakage problems while maintaining high energy efficiency and low cost under small to medium cooling capacity conditions. Therefore, developing a semi-hermetic compressor that combines ammonia-resistant motor technology with a reciprocating piston compression structure has significant application value. Summary of the Invention

[0011] The problem this invention aims to solve is that existing open-type ammonia compressors suffer from shaft seal leakage risks, large size, and high noise, while existing semi-hermetic screw compressors for ammonia have low refrigeration efficiency, high processing costs, and complex maintenance under small and medium refrigeration capacity conditions. The invention provides a semi-hermetic reciprocating refrigeration compressor for ammonia that achieves semi-hermetic leak-free operation and resistance to ammonia corrosion, while significantly improving the energy efficiency ratio in small and medium refrigeration capacity applications, reducing manufacturing costs, and having higher structural strength and safety.

[0012] To address the aforementioned problems, this invention provides a semi-hermetic reciprocating refrigeration compressor for ammonia, comprising: a semi-hermetic housing defining an internal cavity with a refrigerant suction side and a refrigerant discharge side; a compression mechanism disposed within the semi-hermetic housing for compressing ammonia refrigerant; and a drive motor disposed within the semi-hermetic housing and connected to the compression mechanism for transmission; wherein the drive motor includes a stator assembly and a rotor assembly, the stator assembly including a stator core and a stator winding wound on the stator core, the stator winding being made of aluminum or aluminum alloy to withstand corrosion from the ammonia refrigerant; the compression mechanism is a reciprocating piston compression structure, and the semi-hermetic housing is filled with ammonia refrigerant, the drive motor is immersed in the ammonia refrigerant atmosphere, and the drive motor directly drives the reciprocating piston compression structure to perform reciprocating motion, thereby compressing the ammonia refrigerant.

[0013] Preferably, the reciprocating piston compression structure includes: a crankshaft driven to rotate by the rotor assembly of the drive motor; at least one cylinder formed on one side of the semi-enclosed housing or separately disposed within the housing; a piston reciprocally disposed within the cylinder; a connecting rod connected between the piston and the crankshaft, converting the rotational motion of the crankshaft into the reciprocating linear motion of the piston; and a bearing disposed within the semi-enclosed housing for rotatably supporting the crankshaft. Under conditions of small to medium cooling capacity and high pressure ratio, the tight fit between the piston and the cylinder fundamentally avoids the inherent gap leakage problem between the screw rotor, thereby achieving higher volumetric efficiency and compression efficiency. Simultaneously, the piston, cylinder, crankshaft, and connecting rod are all standard mechanical components with mature processing technology, low cost, and easy maintenance, making them particularly suitable for replacing high-cost screw compressors in commercial refrigeration, small to medium-sized cold storage, and other applications, achieving a balance between high performance and low cost.

[0014] Preferably, the rotor assembly of the drive motor is directly sleeved and fixed to one end of the crankshaft, with the crankshaft also serving as the motor shaft of the drive motor. The semi-enclosed housing has a stator housing corresponding to the position of the drive motor, and the stator core is interference-fitted and fixed to the inner wall of the stator housing. This integrated direct-drive design offers several significant advantages. First, it completely eliminates the need for a separate motor shaft, coupling, and corresponding alignment and installation steps, resulting in an extremely compact structure and a significant reduction in overall size and weight. Second, the crankshaft also functions as the motor shaft, achieving true zero transmission loss and directly and without loss transmitting the motor's rotational power to the compression mechanism, significantly improving transmission efficiency. Furthermore, the rigid connection between the rotor and crankshaft, along with the interference fit between the stator core and housing, together constitute a highly rigid powertrain, effectively suppressing vibration and noise during operation and improving operational stability and reliability.

[0015] Preferably, the surface of the stator winding is covered with an insulating layer made of an ammonia-resistant insulating material. Using only aluminum wire solves the corrosion problem of the conductor itself, while using a specialized ammonia-resistant insulating layer to cover the winding provides comprehensive protection against trace amounts of moisture, impurities, or other corrosive components that may be present in the ammonia environment. This ensures that the motor's electrical insulation performance remains stable and reliable even under extreme conditions of long-term immersion in an ammonia atmosphere, fundamentally eliminating the risk of short circuits and motor failures due to insulation deterioration, and greatly extending the motor's service life and the overall operational safety.

[0016] Preferably, multiple heat dissipation fins are integrally cast on the outer surface of the semi-enclosed housing, corresponding to the position of the drive motor, to dissipate the heat generated by the drive motor through natural convection or forced air cooling. The heat dissipation fins and the semi-enclosed housing are integrally cast by a mold. The heat dissipation fins are solid protrusions formed on the outer wall of the housing, which do not damage the integrity of the pressure boundary of the housing. While increasing the heat dissipation area, they also act as reinforcing ribs to improve the compressive strength of the housing, greatly improving the rigidity and compressive strength of the housing and preventing the housing from deforming or cracking under high pressure.

[0017] Preferably, the semi-enclosed housing is provided with an air intake port and an exhaust port. The air intake port is connected to the chamber where the drive motor is located, so that the low-temperature ammonia gas flows through the stator winding and rotor assembly of the drive motor before entering the compression mechanism, so as to cool the drive motor.

[0018] Preferably, the semi-enclosed housing also includes a junction box. The stator winding leads pass through the housing wall and connect to terminals inside the junction box. The connection between the leads and terminals is coated with an ammonia-resistant sealant, preferably polytetrafluoroethylene (PTFE). The junction box provides a safe and isolated space for external power supply. The ammonia-resistant sealant coating where the leads pass through the housing ensures complete isolation between the ammonia-filled environment inside the motor cavity and the external atmosphere. This prevents ammonia from leaking out along the wire gaps and also prevents external air and moisture from intruding and affecting the purity of the internal atmosphere or accelerating corrosion.

[0019] Compared with the prior art, the present invention achieves the following beneficial technical effects: This invention offers higher energy efficiency and lower cost under low to medium cooling capacity conditions. Compared to existing semi-hermetic ammonia screw compressors, this invention employs a reciprocating piston compression structure. Under low to medium cooling capacity and high pressure ratio conditions, the piston structure provides better airtightness and eliminates the serious gap leakage problems of screw compressors, resulting in significantly higher cooling efficiency. Furthermore, the machining processes for the piston, cylinder, and crankshaft eliminate the need for complex screw rotor profiles, significantly reducing manufacturing costs and maintenance barriers, filling a market gap for low to medium power semi-hermetic ammonia compressors. Moreover, the reciprocating piston structure offers higher volumetric efficiency and superior sealing performance under low to medium displacement and high compression ratio conditions.

[0020] This invention solves the problems of ammonia leakage and corrosion, significantly improving safety. It employs a semi-enclosed casing structure, eliminating the shaft seals and couplings of traditional open compressors. This completely eliminates the easily leaking shaft seal components necessary for traditional open compressors, fundamentally preventing the risk of ammonia leakage due to shaft seal wear and eliminating the biggest safety hazard in ammonia refrigeration systems. Simultaneously, by using aluminum or aluminum alloy materials for the motor stator windings, the motor can directly withstand the corrosion of ammonia refrigerant. This allows the drive motor to be integrated with the compression mechanism within the semi-enclosed casing, effectively solving the corrosion problem of traditional copper windings caused by ammonia, enabling the motor to operate stably and continuously in an ammonia atmosphere.

[0021] This invention features a compact structure, high transmission efficiency, and low operating noise. The rotor assembly of the drive motor is directly mounted on the crankshaft, which also serves as the motor shaft, achieving integrated direct drive between the motor and the compression mechanism. This integrated direct-drive design eliminates the need for a bulky base, couplings, and intermediate transmission components such as belts. This significantly improves mechanical transmission efficiency, reduces energy loss, greatly simplifies the overall structure, and reduces vibration and wear caused by misalignment. This results in smoother and more reliable operation of the entire machine, while also effectively reducing operating noise.

[0022] This invention achieves efficient utilization of the system's internal cooling capacity and self-cooling of the motor. By connecting the intake port to the chamber where the drive motor is located, the low-temperature ammonia vapor from the return air flows through the motor's stator windings and rotor assembly before entering the cylinder for compression. This internal cooling structure cleverly utilizes the cooling capacity of the refrigeration system itself to directly and efficiently cool the motor, eliminating the need for an additional and complex external cooling system, simplifying the structure, and further ensuring efficient and stable operation of the motor at a suitable temperature, thus improving the overall energy efficiency. It effectively solves the heat dissipation problem of the motor in a semi-enclosed space, eliminating the need for complex external cooling oil circuits or bulky water-cooling jackets. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the semi-hermetic reciprocating piston refrigeration compressor of the present invention.

[0024] Figure 2 This is a schematic diagram of the semi-hermetic reciprocating piston refrigeration compressor of the present invention from another perspective.

[0025] Figure 3 This is a schematic cross-sectional view of the semi-hermetic reciprocating piston refrigeration compressor of the present invention.

[0026] In the diagram: 10-semi-enclosed housing, 11-heat dissipation fins, 20-compression mechanism, 21-cylinder, 22-piston, 23-connecting rod, 30-drive motor, 31-stator assembly, 311-stator winding, 32-rotor assembly, 40-crankshaft, 50-junction box, 60-bearing. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the following description will be provided in conjunction with the appendix. Figure 1-3 The embodiments of the present invention will be described in further detail. Example

[0028] Reference Figures 1 to 3 As shown, the present invention provides a semi-hermetic reciprocating refrigeration compressor for ammonia. The compressor mainly includes a semi-hermetic housing 10, a compression mechanism 20 disposed inside the housing 10, and a drive motor 30 for driving the compression mechanism 20.

[0029] The semi-enclosed housing 10 is typically integrally cast from high-strength cast iron or cast steel, defining a sealed receiving cavity within it. This cavity can be divided into an intake side, which typically communicates with the motor cavity, and an exhaust side, which communicates with the exhaust valve of the compression mechanism 20, based on the airflow path. The housing 10 is provided with intake and exhaust ports connected to the refrigeration system. Specifically, as... Figure 1 and Figure 2 As shown, multiple outwardly protruding heat dissipation fins 11 are integrally cast on the outer surface of the housing 10, corresponding to the stator area of ​​the internal drive motor 30. These heat dissipation fins 11 are integrally cast with the housing 10 body using a mold during casting, forming a solid protruding structure. Functionally, in conjunction with suction cooling, they increase the heat exchange area to assist in dissipating heat from the generator, ensuring the aluminum wire motor operates at a suitable temperature. Structurally, due to the integral casting process, the solid heat dissipation fins act as reinforcing ribs of the housing. Without compromising the integrity of the housing's pressure boundary, this significantly improves the radial rigidity and overall compressive strength of the housing, enabling it to withstand the high-pressure conditions of the ammonia refrigeration system more safely and preventing housing deformation or cracking.

[0030] Reference Figure 3 As shown, the compression mechanism 20 is a typical reciprocating piston structure. It includes at least one cylinder 21, which can be directly machined onto the housing 10 or installed as a separate component within the housing. Each cylinder 21 is equipped with a reciprocating piston 22. A crankshaft 40 is rotatably supported by bearings 60 disposed within the housing 10. Each piston 22 is connected to the crankshaft 40 via a connecting rod 23, thereby converting the rotational motion of the crankshaft 40 into the reciprocating linear motion of the piston 22 within the cylinder 21, thus compressing the ammonia refrigerant gas entering the cylinder 21.

[0031] The drive motor 30 is also housed within the internal cavity of the semi-enclosed housing 10 and located on one side of the compression mechanism 20. The drive motor 30 includes a stator assembly 31 and a rotor assembly 32. The stator assembly 31 includes a stator core and a stator winding 311 wound thereon. The stator winding 311 is made of aluminum wire or aluminum alloy wire, thus resisting corrosion from the ammonia refrigerant filling the semi-enclosed housing 10. To ensure long-term electrical safety of the winding, the surface of the aluminum stator winding 311 is covered with an ammonia-resistant insulating layer, such as polyimide or a specially treated composite insulating material.

[0032] The drive motor 30 and the compression mechanism 20 adopt a highly integrated direct drive method. Specifically, as shown... Figure 3 As shown, the rotor assembly 32 of the drive motor 30, preferably a permanent magnet rotor, is directly fitted and fixed to the extension end of the crankshaft 40 via a key connection, heat fitting, or other fastening method. This means that the crankshaft 40 also serves as the motor shaft of the drive motor 30, achieving zero intermediate links in the power transmission path. Correspondingly, the semi-enclosed housing 10 has a cylindrical stator receiving portion formed at the position of the stator of the drive motor 30. The stator core is firmly press-fitted and fixed to the inner wall of the stator receiving portion by means of interference fit or other methods, maintaining a precise coaxial relationship with the rotor assembly 32.

[0033] To facilitate the extraction of power generated by the motor and ensure a safe connection to an external power source, a junction box 50 is provided outside the semi-enclosed housing 10. The stator winding 311 leads pass through sealed holes in the housing wall and connect to terminals within the junction box 50. Ammonia-resistant sealing coatings or seals, preferably polytetrafluoroethylene (PTFE) seals, are applied or provided at the interfaces where the leads pass through the housing and at the connection points of the terminals to ensure complete isolation between the ammonia-filled environment inside the motor cavity and the external atmosphere, preventing ammonia leakage and the intrusion of external media.

[0034] To facilitate understanding of the above technical solutions of the present invention, the following detailed description of the above technical solutions of the present invention will be provided through specific usage methods.

[0035] The specific working process is as follows: When the compressor starts, the drive motor 30 is energized, and its rotor assembly 32 drives the crankshaft 40 to rotate, which in turn drives the piston 22 to reciprocate within the cylinder 21 via the connecting rod 23. Low-temperature, low-pressure ammonia gas from the evaporator first enters the chamber where the drive motor 30 is located through the suction port. This low-temperature ammonia gas flows through the surface of the higher-temperature stator winding 311 and rotor assembly 32, effectively cooling them and carrying away the heat generated by the motor operation. Subsequently, the ammonia gas, which has been preheated and cooled simultaneously, is drawn into the cylinder 21 of the compression mechanism 20 for compression, becoming a high-temperature, high-pressure gas before being discharged from the exhaust port, completing one working cycle. Example

[0036] Building upon Example 1, to further optimize performance, the compressor in this example can be configured with a variable frequency control system. The inverter is connected to the junction box 50 via a cable, receives commands from an external controller, and achieves stepless adjustment of the motor speed and compressor cooling capacity by changing the power supply frequency input to the drive motor 30. This variable frequency technology, combined with a reciprocating piston structure, can maintain high operating efficiency under partial load, further expanding the energy-saving advantages and application scope of this invention.

[0037] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0038] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0039] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention described herein.

Claims

1. A semi-hermetic reciprocating refrigeration compressor for ammonia, comprising: A semi-enclosed housing (10) defines an internal cavity with a refrigerant suction side and a refrigerant discharge side; A compression mechanism (20) is disposed within the semi-enclosed housing (10) for compressing ammonia refrigerant; and a drive motor (30) is disposed within the semi-enclosed housing (10) and connected to the compression mechanism (20) for transmission. The drive motor (30) comprises a stator assembly (31) and a rotor assembly (32). The stator assembly (31) comprises a stator core and a stator winding (311) wound around the stator core. The stator winding (311) is made of aluminum or an aluminum alloy to withstand the corrosion of the ammonia refrigerant. The compression mechanism (20) is a reciprocating piston compression structure, and the semi-enclosed housing (10) is filled with ammonia refrigerant. The drive motor (30) is immersed in the atmosphere of the ammonia refrigerant, and the drive motor (30) directly drives the reciprocating piston compression structure to perform reciprocating motion, thereby compressing the ammonia refrigerant.

2. The semi-hermetic reciprocating refrigeration compressor for ammonia according to claim 1, characterized in that, The reciprocating piston compression structure includes: a crankshaft (40) driven to rotate by the rotor assembly (32) of the drive motor (30); at least one cylinder (21) formed on one side of the semi-enclosed housing (10) or separately disposed within the housing; a piston (22) reciprocally disposed within the cylinder (21); and a connecting rod (23) connected between the piston (22) and the crankshaft (40) to convert the rotational motion of the crankshaft (40) into the reciprocating linear motion of the piston (22); and a bearing (60) disposed within the semi-enclosed housing (10) for rotatably supporting the crankshaft (40).

3. The semi-hermetic reciprocating refrigeration compressor for ammonia according to claim 2, characterized in that, The rotor assembly (32) of the drive motor (30) is directly sleeved and fixed to one end of the crankshaft (40). The crankshaft (40) also serves as the motor shaft of the drive motor (30). The semi-enclosed housing (10) is provided with a stator receiving part corresponding to the position of the drive motor (30). The stator core is interference-fitted and fixed to the inner wall of the stator receiving part.

4. The semi-hermetic reciprocating refrigeration compressor for ammonia according to claim 1, characterized in that, The surface of the stator winding (311) is covered with an insulating layer made of an ammonia-resistant insulating material.

5. The semi-hermetic reciprocating refrigeration compressor for ammonia according to claim 1, characterized in that, On the outer surface of the semi-enclosed housing (10), a plurality of heat dissipation fins (11) are integrally cast corresponding to the position of the drive motor (30) to dissipate the heat generated by the drive motor (30) through natural convection or forced air cooling. The heat dissipation fins (12) and the semi-enclosed housing (10) are integrally cast by mold. The heat dissipation fins (12) are solid protrusions formed on the outer wall of the housing.

6. The semi-hermetic reciprocating refrigeration compressor for ammonia according to any one of claims 1 to 5, characterized in that, The semi-enclosed housing (10) is provided with an air intake port and an exhaust port. The air intake port is connected to the chamber where the drive motor (30) is located, so that the low-temperature ammonia gas flows through the stator winding (311) and rotor assembly (32) of the drive motor (30) before entering the compression mechanism (20) to cool the drive motor (30).

7. The semi-hermetic reciprocating refrigeration compressor for ammonia according to claim 2, characterized in that, The semi-enclosed housing (10) is also provided with a junction box (50), and the lead wire of the stator winding (311) passes through the housing wall and connects to the terminal block in the junction box (50). The connection between the lead wire and the terminal block is provided with an ammonia-resistant sealing coating.

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