A high-efficiency permanent magnet variable frequency motor driven reciprocating compressor

Abstract

This utility model relates to the field of compressor technology, specifically a high-efficiency permanent magnet variable frequency motor driven piston compressor, including a casing, crankshaft, connecting rod, crosshead, cylinder, and piston. The crankshaft horizontally runs through the casing, with four cranks in the middle, each 90° out of phase. The connecting rods radially connect the cranks to the crosshead. The crosshead is connected to the piston rod via a hydraulic tension rod, driving the piston to reciprocate within a two-stage cylinder. The permanent magnet variable frequency motor directly drives the crankshaft via a rigid coupling, which uses a heat-shrink transition and a double tangential key connection. An automatic turning device is installed on the non-drive end of the motor, and precise crankshaft positioning is achieved through a planetary gearbox and an electromagnetic clutch. This solution solves the torque pulsation problem of piston compressors, improves energy efficiency under varying operating conditions, and extends equipment life.

Description

Technical Field

[0001] This utility model relates to the field of compressor technology, specifically a reciprocating compressor driven by a high-efficiency permanent magnet variable frequency motor. Background Technology

[0002] Piston compressors are widely used in industrial gas compression, such as air compression, refrigeration, and chemical processes. Traditional drive methods primarily employ high-voltage synchronous motors or large asynchronous motors. The efficiency of traditional asynchronous motors (especially large wound-rotor or squirrel-cage motors) typically does not exceed IE3 or IE4 (IEC60034), with a significant decrease in efficiency, particularly under partial load and at non-rated speeds. Synchronous motors have relatively higher efficiency, but are usually optimal at their rated point. Under the global trend of energy conservation and emission reduction, this energy consumption level is insufficient. In recent years, their application in driving small and medium-sized compressors (especially screw compressors) has gradually become more widespread, as their high efficiency (IE5), high power density, and excellent speed regulation performance have been proven.

[0003] However, applying permanent magnet variable frequency direct drive technology to large reciprocating compressors faces unique challenges. The periodic and impact loads of reciprocating compressors will generate strong torque pulsations in the motor, requiring the motor to have extremely strong instantaneous overload capacity and the ability to suppress torque fluctuations.

[0004] To address the issue of low energy efficiency in existing reciprocating compressors at variable speeds, further improve compressor efficiency, reduce user operating energy consumption, and enhance compressor safety and lifespan, this technical solution designs a reciprocating compressor driven by a high-efficiency permanent magnet variable frequency motor. Utility Model Content

[0005] The purpose of this invention is to provide a high-efficiency permanent magnet variable frequency motor driven piston compressor to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] A high-efficiency permanent magnet variable frequency motor driven piston compressor includes: a body, a crankshaft horizontally penetrating the body, four sets of connecting rods, a crosshead, a cylinder, and a piston; the permanent magnet variable frequency motor directly drives the crankshaft through a rigid coupling, wherein the rigid coupling and the motor shaft are heat-fitted with an interference fit and are provided with double tangential keys;

[0008] The crankshaft has four cranks with a 90° phase difference in the middle, and four sets of connecting rods connect the cranks and the crosshead in a radial pattern;

[0009] The crosshead is connected to the piston rod via a hydraulic tension rod, and the piston rod is threaded to lock the piston.

[0010] The cylinders are divided into two rows of large-diameter low-pressure stage cylinders at the bottom and two rows of small-diameter high-pressure stage cylinders at the top.

[0011] As a further embodiment of this utility model: the non-drive end shaft extension of the permanent magnet variable frequency motor is connected to an automatic turning device, which includes an electromagnetic clutch, a planetary gearbox and an external drive motor connected in sequence.

[0012] As a further embodiment of this invention: the double tangential keys of the rigid coupling are symmetrically distributed.

[0013] As a further embodiment of this utility model: an oil scraper is provided at the piston rod protruding below the crosshead, with built-in double oil scraper rings and an oil return hole.

[0014] As a further embodiment of this utility model: the housing of the permanent magnet variable frequency motor is covered with a cooling water jacket, and is provided with a water inlet and a water outlet.

[0015] As a further embodiment of this invention, a seal is provided between the cylinder and the machine body.

[0016] Compared with the prior art, the beneficial effects of this utility model are: by eliminating transmission loss through direct drive of permanent magnet motor, the efficiency under all working conditions reaches IE5 level, saving more than 25% energy compared with asynchronous motor;

[0017] The double tangential key + heat-shrink connection can withstand instantaneous overload torque of 3 times, solving the coupling failure caused by piston machine pulsation;

[0018] The risk of bolt loosening is eliminated by using a crosshead hydraulic tension rod, and vibration is reduced by using a 90° phase crankshaft to balance inertial forces.

[0019] The compressor start-stop dead point is accurately located by an automatic turning device, avoiding damage during load start-up. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a reciprocating compressor driven by a high-efficiency permanent magnet variable frequency motor.

[0021] Figure 2 This is a schematic diagram of a partial connection structure between a permanent magnet variable frequency motor and a crankshaft in a reciprocating compressor driven by a high-efficiency permanent magnet variable frequency motor.

[0022] The components include: 1. machine body; 2. crankshaft; 3. connecting rod; 4. crosshead; 5. oil scraper; 6. cylinder; 7. piston; 8. sealer; 9. rigid coupling; 10. permanent magnet variable frequency motor; 11. automatic turning device; 12. water inlet; 13. water outlet; and 14. bolts. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0024] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model 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 this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] Please see Figures 1-2 A high-efficiency permanent magnet variable frequency motor driven piston compressor includes a body 1, a crankshaft 2, a connecting rod 3, a crosshead 4, a cylinder 6, a piston 7, a rigid coupling 9, a permanent magnet variable frequency motor 10, and an automatic turning device 11.

[0028] The drive end of the permanent magnet variable frequency motor 10 is connected to a rigid coupling 9, and the end of the rigid coupling 9 is connected to a crankshaft 2 via a flange and bolts 14.

[0029] Among them, the rigid coupling 9 is connected to the drive end of the permanent magnet variable frequency motor 10 shaft through a heat-fitted transition and a double tangential key;

[0030] The crankshaft 2 runs horizontally through the center of the body 1, and is supported at both ends by bearing seats of the body 1. There are 4 cranks (90° phase difference) in the middle. There are four sets of connecting rods 3 arranged radially. The two ends of the connecting rods 3 are respectively provided with a large end and a small end. The large end is connected to the crank of the crankshaft 2, and the small end is connected to the crosshead 4. The connecting rods 3 are used to convert the rotation of the crankshaft 2 into the linear motion of the crosshead 4.

[0031] The crosshead 4 is embedded in the vertical slide of the body 1, and its bottom end is connected to the cross rod 4 by a pin to transmit thrust and accommodate the swing of the crosshead 4. Its upper end is connected to the piston 7 by a piston rod. The piston 7 is located at the output end of the cylinder 6, and the two form a two-stage compression layout:

[0032] Low-pressure stage: bottom two rows of cylinders 6 (larger diameter);

[0033] High-pressure stage: Top two rows of cylinders, 6 in total (smaller diameter);

[0034] Each cylinder 6 has a built-in piston 7, and the piston rod passes through a seal 8 and connects to a crosshead 4.

[0035] Among them, the crosshead 4 is connected to the piston rod through a hydraulic tension rod to ensure fatigue resistance and reduce the problem of loosening of traditional bolts; the piston rod is connected to the piston 7 through threaded locking, and the cylinder 6 is connected by flange bolts and positioning pins to enable it to withstand the gas and ensure the perpendicularity of the cylinder 6 axis.

[0036] When the crankshaft 2 rotates, it drives the connecting rod 3, which controls the crosshead 4 to make reciprocating linear motion in the slide. The top of the crosshead 4 is connected to the piston 7 by hydraulic tension.

[0037] That is: the gas compression cycle process:

[0038] First stage compression low-pressure stage:

[0039] Piston 7 moves downward → Cylinder 6 volume increases → Intake valve opens, drawing in gas pressure P1;

[0040] Piston 7 moves upward → volume decreases → gas is compressed to intermediate pressure P2 and discharged into the intercooler.

[0041] Second-stage compression high-pressure stage:

[0042] The cooled gas enters the top cylinder 6;

[0043] Piston 7 compresses the pressure twice to the final pressure P3, which is then output through the exhaust valve.

[0044] In this embodiment of the invention, an oil scraper 5 is provided at the piston rod protrusion point below the crosshead 4. The oil scraper 5 has a built-in double oil scraping ring and an oil return hole. The oil scraper 5 scrapes off the lubricating oil carried by the piston rod to prevent it from entering the cylinder 6 and recovers the oil to the oil sump of the machine body 1.

[0045] A seal 8 is provided at the interface between cylinder 6 and body 1 to wrap the piston rod, dynamically seal the piston rod, and prevent gas leakage from cylinder 6.

[0046] In one embodiment of the present invention, a cooling water jacket is tightly wrapped around the outer periphery of the permanent magnet variable frequency motor 10, and the cooling water jacket is provided with a water inlet 12 and a water outlet 13.

[0047] The permanent magnet variable frequency motor 10 has a shaft extension section at the non-drive end, and the automatic turning device 11 is connected to the shaft at the non-drive end. The turning device is driven by an external motor.

[0048] Specifically, the non-drive end of the permanent magnet motor 10 is machined with a shaft extension and the surface is hardened to HRC55-60;

[0049] A keyway is provided on the end face of the shaft extension to transmit turning torque. Together with the electromagnetic clutch, planetary gearbox and external drive motor, it realizes the automated turning function.

[0050] That is: the permanent magnet motor extends 10 shafts and drives the crankshaft through spline sleeve engagement → the electromagnetic clutch is energized and engages to transmit torque → the planetary gearbox reduces speed and increases torque by 50:1 → the external motor drives the crankshaft to rotate at low speed → the encoder feedback achieves precise positioning of ±0.5° dead point.

[0051] The working principle of this utility model is as follows: In the idle position of this device, all the aforementioned driving components (representing power elements, electrical devices, and compatible power supplies) are connected via wires. The electrical connections are completed in sequence between the working components. The detailed connection methods are well-known in the field. The following mainly describes the working principle and process, without further explanation of the electrical control.

[0052] Start-up phase:

[0053] The automatic crankshaft 11 drives the crankshaft 2 to rotate to the ±0.5° dead center position;

[0054] When the permanent magnet variable frequency motor 10 is powered on, it drives the crankshaft 2 to rotate via the rigid coupling 9.

[0055] Compression loop:

[0056] Crankshaft 2 drives crosshead 4 to move linearly via connecting rod 3 → Piston 7 moves downward to draw in gas (low-pressure stage);

[0057] Piston 7 compresses the gas to an intermediate pressure as it moves upwards, then cools it before it enters the high-pressure stage for secondary compression.

[0058] High-pressure gas is output through the exhaust valve.

[0059] Shutdown and maintenance:

[0060] The cooling water jacket runs continuously for 2 minutes to dissipate residual heat;

[0061] The oil scraper 5 recovers residual lubricating oil from the piston rod to prevent it from entering the cylinder 6.

[0062] It should be understood that in this application, all rotating, sliding, meshing, belt-driven and other moving parts are well lubricated and not prone to slippage or wear, and each part is provided with a corresponding protective shell. However, in the accompanying drawings of this application, the connection state of each moving part is not shown. It should also be understood that all parts in this application are made of metal or plastic materials with suitable strength in the relevant field to ensure that their structural rigidity meets the actual requirements.

[0063] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A high efficiency permanent magnet variable frequency motor driven piston compressor characterized by, include: The engine body (1), the crankshaft (2) that runs horizontally through the engine body, four sets of connecting rods (3), the crosshead (4), the cylinder (6) and the piston (7); The permanent magnet variable frequency motor (10) directly drives the crankshaft (2) through a rigid coupling (9). The rigid coupling (9) and the motor shaft are heat-fitted with an interference fit and are equipped with double tangential keys. The crankshaft (2) has four cranks with a phase difference of 90° in the middle, and four sets of connecting rods (3) are radially connected to the cranks and the crosshead (4). The crosshead (4) is connected to the piston rod via a hydraulic tension rod, and the piston rod is threaded to lock the piston (7). The cylinder (6) is divided into two rows of large-diameter low-pressure stage cylinders at the bottom and two rows of small-diameter high-pressure stage cylinders at the top.

2. The high efficiency permanent magnet variable frequency motor driven piston compressor of claim 1, wherein, The non-drive end shaft of the permanent magnet variable frequency motor (10) is connected to an automatic turning device (11), which includes an electromagnetic clutch, a planetary gearbox and an external drive motor connected in sequence.

3. The high efficiency permanent magnet variable frequency motor driven piston compressor of claim 1, wherein, The rigid coupling (9) has symmetrically distributed double tangential keys.

4. The high efficiency permanent magnet variable frequency motor driven piston compressor of claim 1, wherein, An oil scraper (5) is installed at the piston rod protrusion point below the crosshead (4), with a built-in double oil scraper ring and oil return hole.

5. The high efficiency permanent magnet variable frequency motor driven piston compressor of claim 1, wherein, The permanent magnet variable frequency motor (10) has a cooling water jacket covering its outer shell and is provided with a water inlet (12) and a water outlet (13).

6. The high efficiency permanent magnet variable frequency motor driven piston compressor of claim 1, wherein, A seal (8) is provided between the cylinder (6) and the body (1).

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