Centrifugal compressor

Abstract

The invention provides a compressor, belongs to the technical field of compressors, and particularly relates to a centrifugal compressor which comprises a motor shell, a motor stator, an air bearing and a rotor assembly. Wherein the rotor assembly comprises a main shaft, a pull rod, an impeller, a locking nut and a thrust disc, the main shaft is a hollow pull rod main shaft, the hollow pull rod main shaft comprises a middle section provided with magnetic steel, a bearing position matched with the air bearing and end parts at the two ends, and the thrust disc is fixedly arranged on the periphery of the hollow pull rod main shaft in a sleeving manner. According to the centrifugal compressor, the main shaft is arranged to be the hollow pull rod main shaft, the weight is light, the weight of the whole rotor assembly is reduced, the surface pressure of the air bearing is reduced, and therefore the service life of the air bearing is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of compressors, and in particular to a centrifugal compressor. Background Art

[0002] The air bearing has limited load capacity, and excessive bearing load will shorten its service life: the one-piece spindle is a solid shaft directly processed from a round bar forging, and the overall weight of the spindle is large, so the air bearing is subject to high surface pressure. However, due to its own characteristics, the air bearing has a low load capacity, so the high surface pressure of the solid spindle affects the service life of the air bearing. In order to solve the problem of excessive surface pressure of the air bearing, the bearing surface pressure is reduced by increasing the bearing length to increase the inner area of ​​the bearing. However, the length of the spindle bearing position is also increased accordingly, and the weight of the spindle is therefore increased. Therefore, it is necessary to iterate repeatedly until the bearing length is large enough to meet the surface pressure requirements. In this case, the overall length and weight of the spindle are increased.

[0003] The spindle processing is difficult, the cycle is long, and the cost is high: the one-piece spindle is limited by the diameter of the impeller inlet head, and the diameter of the spindle end is small. In addition, the end of the spindle needs to pass through the impeller and the locking impeller, so the length is long. This results in the spindle end being a slender rod section with a small diameter and a long length, while the middle magnetic steel section has a larger diameter. When the spindle is processed, the end is easily deformed, so the spindle processing is difficult and the cycle is long. At the same time, the one-piece spindle is directly processed and formed from round bar forgings. Due to the uneven heat treatment of the round bar forgings, the strength of the round bar core is lower than that of the outer surface, resulting in poor strength at the spindle end. The end needs to meet the torque transmission requirements of the impeller, and the strength requirements are relatively high. Therefore, high strength requirements are required in material selection. Generally, the higher the material strength, the higher the hardness, so the difficulty of spindle processing is increased again, and the cost is also increased.

[0004] The rotor group has a large imbalance: The end of the integrated main shaft is a slender rod, and the impeller is installed on the slender rod. During operation, the end has a large deflection, which increases the imbalance of the rotor group in operation and affects the stability and reliability of the compressor. Summary of the invention

[0005] In view of this, the present application provides a centrifugal compressor, which, by configuring the main shaft as a hollow tie rod main shaft, is light in weight and reduces the weight of the entire rotor assembly, thereby reducing the surface pressure on the air bearing and extending the service life of the air bearing.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] A centrifugal compressor, comprising:

[0008] Motor housing, motor stator, air bearing and rotor assembly;

[0009] Among them, the rotor assembly includes a main shaft, a tie rod, an impeller, a locking nut and a thrust plate. The main shaft is a hollow tie rod main shaft, and the hollow tie rod main shaft includes a middle section provided with a magnetic steel, a bearing position matched with the air bearing, and end portions at both ends. A cavity is provided inside the hollow tie rod main shaft, and the cavity passes through the middle section and extends from the bearing position at one end to the bearing position at the other end. The thrust plate is sleeved and fixed on the outer periphery of the hollow tie rod main shaft.

[0010] Optionally, the hollow pull rod main shaft includes a core shaft, which axially covers the middle section and the bearing position of the hollow pull rod main shaft; the core shaft is a hollow structure, and a circular ring-shaped magnet is built into the outer periphery of the middle section of the core shaft, the inner hole of the magnet is radially matched with the outer periphery of the core shaft, and a sheath is also provided on the outer periphery of the magnet.

[0011] Optionally, the hollow pull rod main shaft further includes end covers, and both ends of the core shaft are open structures. The end covers are respectively arranged at the open ends of the core shaft to form the end parts, and the pull rod is threadedly connected to the end covers.

[0012] Optionally, a pull rod mounting hole is provided at one end of the end cover away from the core shaft, and the pull rod mounting hole includes an internal threaded hole, and the external thread at the end of the pull rod can cooperate with the internal threaded hole.

[0013] Optionally, the pull rod mounting hole also includes an axial cylindrical countersunk hole connected to the internal threaded hole, and the axial cylindrical countersunk hole is arranged at the end of the internal threaded hole away from the core shaft, and the inner diameter of the axial cylindrical countersunk hole is larger than the major thread diameter of the internal threaded hole; the axial cylindrical countersunk hole includes an axial first section and a second section, wherein the inner diameter of the first section farther from the internal threaded hole is larger than the inner diameter of the second section closer to the internal threaded hole, and the first section and the second section form a step hole.

[0014] Optionally, the pull rod includes a rear threaded section, a rear cylindrical section, a stretching section, a front cylindrical section and a front threaded section connected in sequence; the diameter of the rear cylindrical section is larger than that of the rear threaded section, the diameter of the front cylindrical section is larger than that of the front threaded section, the rear cylindrical section radially cooperates with the second section of the axial cylindrical countersunk hole, and the front cylindrical section radially cooperates with the inner hole of the impeller.

[0015] Optionally, the axial lengths of the rear cylindrical section and the front cylindrical section are both smaller than the axial length of the stretching section.

[0016] Optionally, the pull rod also includes a transition section respectively arranged between the rear threaded section and the rear cylindrical section, and between the front cylindrical section and the front threaded section; the transition section includes a straight section, and the straight section of the transition section between the rear threaded section and the rear cylindrical section is respectively connected to the rear threaded section and the rear cylindrical section through an arc section; the straight section of the transition section between the front cylindrical section and the front threaded section is respectively connected to the front cylindrical section and the front threaded section through an arc section.

[0017] Optionally, the outer diameter of the stretching section is smaller than the outer diameters of the rear thread section, the front thread section and the transition section, and / or the roughness Ra of the stretching section is less than or equal to 0.4 μm.

[0018] Optionally, a bushing is sleeved on the outer periphery of the end cover, and the impeller is sleeved on the outer periphery of the end cover and abuts against the axial end of the bushing.

[0019] The centrifugal compressor provided in the present application has a main shaft in its rotor assembly which is a hollow tie rod main shaft. The hollow tie rod main shaft is light in weight and reduces the weight of the entire rotor assembly, thereby reducing the surface pressure on the air bearing and extending the service life of the air bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0021] Figure 1 This is a schematic structural diagram of the centrifugal compressor of the present application;

[0022] Figure 2 It is a schematic diagram of the hollow tie rod main shaft structure;

[0023] Figure 3 It is a schematic diagram of the end cover structure of the hollow tie rod main shaft;

[0024] Figure 4 Schematic diagram of the pull rod structure;

[0025] Figure 5 is a partial schematic diagram of a rotor assembly;

[0026] Figure 6 Schematic diagram of the rotor assembly.

[0027] exist Figure 1-Figure 6 middle:

[0028] 1. Motor housing; 11. Cavity; 2. Motor stator; 3. Air bearing;

[0029] 4. Hollow tie rod main shaft; 41. Middle section; 411. Magnetic steel; 412. Sheath; 42. Bearing seat; 421. Mandrel; 43. End; 431. End cover; 4311. Axial cylindrical countersunk hole; 4312. Internal threaded hole;

[0030] 5. Pull rod; 51. Rear threaded section; 52. Rear cylindrical section; 53. Stretching section; 54. Front cylindrical section; 55. Front threaded section; 56. Transition section; 57. Arc section;

[0031] 6. Impeller; 7. Locking nut; 8. Volute; 81. Gas containing chamber; 9. Bushing; 10. Thrust plate. DETAILED DESCRIPTION

[0032] The present application provides a centrifugal compressor, which is lightweight and reduces the weight of the entire rotor assembly by setting the main shaft as a hollow tie rod main shaft, thereby reducing the surface pressure on the air bearing and extending the service life of the air bearing.

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] like Figure 1 As shown, the centrifugal compressor provided by the present application includes a motor housing 1, a motor stator 2, an air bearing 3 and a rotor assembly;

[0035] Among them, the rotor assembly is a collection of rotating parts in the centrifugal compressor, including a main shaft, a tie rod 5, an impeller 6, a locking nut 7 and a thrust plate 10. The main shaft is a hollow tie rod main shaft 4. The hollow tie rod main shaft 4 includes a middle section 41 provided with a magnetic steel 411, a bearing position 42 matched with the air bearing 3, and end portions 43 at both ends. A cavity is provided inside the hollow tie rod main shaft 4. The cavity passes through the middle section 41 and extends from the bearing position 42 at one end to the bearing position 42 at the other end, and is a whole; the thrust plate 10 is sleeved and fixed on the outer periphery of the hollow tie rod main shaft 4, and the thrust plate 10 can be processed or welded with the hollow tie rod main shaft 4 as a whole;

[0036] The motor stator 2 is installed in the cavity 11 of the motor housing 1, and the middle section 41 of the hollow tie rod main shaft 4 passes through the motor stator 2 to form a gap, which is about 1 to 3 mm on one side. In addition, the two side ends 43 of the hollow tie rod main shaft 4 extend out of the motor housing 1, and the impeller 6 is radially installed on the outer circle of the end 43 to reduce the deflection of the end 43 during the operation of the rotor assembly and improve the stability and reliability of the operation of the rotor assembly. The tie rod 5 passes through the inner hole of the impeller 6, and one end is installed on the end 43 of the hollow tie rod main shaft 4; the other end exceeds the end face of the impeller 6 and is threadedly matched with the locking nut 7. The bearing position 42 on the hollow tie rod main shaft 4 is located between the middle section 41 and the end 43. The bearing positions 42 on both sides pass through the air bearing 3 and are radially matched, and there is a gap between them. The single-side gap is less than 1 mm. The gas in the gap forms an air film to support the main shaft. The volute 8 is installed at the end of the motor housing 1 . The volute 8 has a gas containing cavity 81 . The end 43 of the hollow tie rod main shaft 4 , the tie rod 5 , the impeller 6 , and the locking nut 7 are all located inside the gas containing cavity 81 .

[0037] The hollow pull rod main shaft 4 of the present application is light in weight, so that the weight of the entire rotor assembly is reduced, the surface pressure on the air bearing 3 is reduced, and the service life of the bearing is extended.

[0038] In a preferred embodiment, Figure 2 As shown, the hollow pull rod main shaft 4 includes a cylindrical core shaft 421, which axially covers the middle section 41 and the bearing position 42 of the hollow pull rod main shaft 4; the core shaft 421 is a hollow structure, and a circular ring-shaped magnet 411 is built into the outer periphery of the middle section 41 of the core shaft 421, and the inner hole of the magnet 411 is radially matched with the outer periphery of the core shaft 421, and a sheath 412 is also arranged on the outer periphery of the magnet 411.

[0039] The hollow pull rod main shaft 4 is hollow to reduce the weight of the entire rotor assembly. In order to match the hollow structure of the hollow pull rod main shaft 4, a magnetic steel 411 with a circular ring cross-section is used to replace the original solid magnetic steel. The sleeve 412 can protect the outer surface of the magnetic steel 411. The outer circle of the magnetic steel 411 is radially matched with the inner hole of the sleeve 412, which also ensures the stability of the structure and the integrity of the magnetic field.

[0040] In a preferred embodiment, Figure 2 and Figure 3 As shown, in order to facilitate the processing and manufacturing of the hollow pull rod main shaft 4 and also to facilitate installation and disassembly, the hollow pull rod main shaft 4 is configured as a structure of a core shaft 421 with open structures at both ends plus end covers 431 on both sides, and the end covers 431 are respectively arranged at the open ends of the core shaft 421 to form end parts 43, and the pull rod 5 is threadedly connected to the end covers 431.

[0041] In a preferred embodiment, Figure 2 and Figure 3As shown, a pull rod mounting hole is provided at one end of the end cover 431 away from the core shaft 421 , and the pull rod mounting hole includes an internal threaded hole 4312 , and the external thread at the end of the pull rod 5 can match the internal threaded hole 4312 .

[0042] In this way, the pull rod 5 and the end cover 431 are detachable through threaded cooperation, which is convenient for installation and disassembly.

[0043] In a preferred embodiment, Figure 2 and Figure 3 As shown, the pull rod mounting hole also includes an axial cylindrical countersunk hole 4311 connected to the internal threaded hole 4312, and the axial cylindrical countersunk hole 4311 is arranged at the end of the internal threaded hole 4312 away from the core shaft 421. The inner diameter of the axial cylindrical countersunk hole 4311 is larger than the major diameter of the thread of the internal threaded hole 4312, forming a transition area and reducing stress concentration; the axial cylindrical countersunk hole 4311 includes an axial first section and a second section, wherein the inner diameter of the first section farther from the internal threaded hole 4312 is larger than the inner diameter of the second section close to the internal threaded hole 4312, and the first section and the second section form a stepped hole, which is convenient for the precise positioning and installation of the pull rod 5.

[0044] In a preferred embodiment, Figure 4 As shown, the pull rod 5 includes a rear threaded section 51, a rear cylindrical section 52, a stretching section 53, a front cylindrical section 54 and a front threaded section 55 which are connected in sequence; the diameter of the rear cylindrical section 52 is larger than that of the rear threaded section 51, the diameter of the front cylindrical section 54 is larger than that of the front threaded section 55, the rear cylindrical section 52 radially cooperates with the second section of the axial cylindrical countersunk hole 4311, and the front cylindrical section 54 radially cooperates with the inner hole of the impeller 6.

[0045] The rear threaded section 51 cooperates with the internal threaded hole 4312 of the end cover 431; the front threaded section 55 cooperates with the locking nut 7;

[0046] The rear cylindrical section 52 and the front cylindrical section 54 both play a role of limiting. Specifically, the rear cylindrical section 52 is clamped in the second section of the axial cylindrical counterbore 4311, and the front cylindrical section 54 is clamped in the inner hole of the impeller 6, thereby limiting the radial displacement of the pull rod 5.

[0047] The stretching section 53 generates axial deformation to prevent other sections of the pull rod 5 , such as the threaded section and the transition section, from causing adverse effects.

[0048] In a preferred embodiment, Figure 4 As shown, the axial lengths of the rear cylindrical section 52 and the front cylindrical section 54 are both smaller than the axial length of the stretching section 53. Preferably, the axial lengths of the rear cylindrical section 52 and the front cylindrical section 54 are both much smaller than the axial length of the stretching section 53 to reduce unnecessary weight and material consumption.

[0049] In a preferred embodiment, Figure 4As shown, the pull rod 5 also includes a transition section 56 respectively arranged between the rear threaded section 51 and the rear cylindrical section 52, and between the front cylindrical section 54 and the front threaded section 55; the transition section 56 includes a straight section, and the straight section of the transition section 56 between the rear threaded section 51 and the rear cylindrical section 52 is respectively connected to the rear threaded section 51 and the rear cylindrical section 52 through an arc section 57; the straight section of the transition section 56 between the front cylindrical section 54 and the front threaded section 55 is respectively connected to the front cylindrical section 54 and the front threaded section 55 through an arc section 57.

[0050] In order to ensure smooth connection between the sections, a number of transition sections 56 and arc sections 57 are respectively set between the sections; the arc radius is recommended to be greater than R5 to effectively disperse stress and avoid stress concentration; the threads of the front thread section 55 and the rear thread section 51 have the same rotation direction, which is opposite to the rotation direction of the centrifugal compressor.

[0051] In a preferred embodiment, Figure 4 As shown, the stretching section 53 is designed as a slender rod, and its outer diameter is smaller than the outer diameters of the rear threaded section 51, the front threaded section 55 and the transition section 56, so as to ensure that the stretching deformation of the pull rod 5 occurs in the straight and stable stretching section 53, avoiding adverse effects on the threaded section and the transition section;

[0052] And / or, the roughness Ra of the stretching section 53 is less than or equal to 0.4 μm. The roughness requirement of the stretching section 53 is to reduce the influence on the fatigue strength of the pull rod 5 and improve the durability of the pull rod 5 .

[0053] In a preferred embodiment, Figure 5 and Figure 6 As shown, the outer periphery of the end cover 431 is sleeved with a bushing 9, and the impeller 6 is sleeved on the outer periphery of the end cover 431 and abuts against the axial end of the bushing 9. The bushing 9 can facilitate the positioning of the impeller 6 and the installation of the impeller 6 wheel back seal.

[0054] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0055] The block diagrams of the devices, apparatuses, equipment, and systems involved in this application are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The words "such as" used here refer to the phrase "such as but not limited to", and can be used interchangeably with them.

[0056] It should also be noted that in the apparatus, device and method of the present application, each component or each step can be decomposed or recombined, and these decompositions or recombinations should be regarded as equivalent solutions of the present application.

[0057] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0058] It should be understood that the qualifiers "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present application are only used to more clearly explain the technical solutions and cannot be used to limit the scope of protection of the present application.

[0059] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A centrifugal compressor, characterized in that: include: A motor housing (1), a motor stator (2), an air bearing (3) and a rotor assembly; The rotor assembly comprises a hollow tie rod main shaft (4), a tie rod (5), an impeller (6), a locking nut (7) and a thrust plate (10); the hollow tie rod main shaft (4) comprises a middle section (41) provided with a magnetic steel, a bearing position (42) matched with the air bearing (3), and end portions (43) at both ends; a cavity is provided inside the hollow tie rod main shaft (4), the cavity passes through the middle section (41) and extends from the bearing position (42) at one end to the bearing position (42) at the other end; and the thrust plate (10) is sleeved and fixed on the outer periphery of the hollow tie rod main shaft (4).

2. The centrifugal compressor according to claim 1, characterized in that: The hollow pull rod main shaft (4) includes a core shaft (421), and the core shaft (421) axially covers the middle section (41) and the bearing position (42) of the hollow pull rod main shaft (4); the core shaft (421) is a hollow structure, and a circular ring-shaped magnetic steel (411) is built into the outer periphery of the middle section (41) of the core shaft (421), and the inner hole of the magnetic steel (411) is radially matched with the outer periphery of the core shaft (421), and a sheath (412) is also arranged on the outer periphery of the magnetic steel (411).

3. The centrifugal compressor according to claim 2, characterized in that: The hollow pull rod main shaft (4) also includes an end cover (431). The two ends of the core shaft (421) are open structures. The end covers (431) are respectively arranged at the open ends of the core shaft (421) to form the end parts (43). The pull rod (5) is threadedly connected to the end covers (431).

4. The centrifugal compressor according to claim 3, characterized in that: A pull rod mounting hole is provided at one end of the end cover (431) away from the core shaft (421), and the pull rod mounting hole includes an internal threaded hole (4312). The external thread at the end of the pull rod (5) can cooperate with the internal threaded hole (4312).

5. The centrifugal compressor according to claim 4, characterized in that: The pull rod mounting hole also includes an axial cylindrical countersunk hole (4311) connected to the internal threaded hole (4312), and the axial cylindrical countersunk hole (4311) is arranged at the end of the internal threaded hole (4312) away from the core shaft (421), and the inner diameter of the axial cylindrical countersunk hole (4311) is larger than the major diameter of the thread of the internal threaded hole (4312); the axial cylindrical countersunk hole (4311) includes an axial first section and a second section, wherein the inner diameter of the first section farther from the internal threaded hole (4312) is larger than the inner diameter of the second section closer to the internal threaded hole (4312), and the first section and the second section form a stepped hole.

6. The centrifugal compressor according to claim 5, characterized in that: The pull rod (5) includes a rear threaded section (51), a rear cylindrical section (52), a stretching section (53), a front cylindrical section (54) and a front threaded section (55) which are connected in sequence; the diameter of the rear cylindrical section (52) is larger than that of the rear threaded section (51), the diameter of the front cylindrical section (54) is larger than that of the front threaded section (55), the rear cylindrical section (52) is radially matched with the second section of the axial cylindrical counterbore (4311), and the front cylindrical section (54) is radially matched with the inner hole of the impeller (6).

7. The centrifugal compressor according to claim 6, characterized in that: The axial lengths of the rear cylindrical section (52) and the front cylindrical section (54) are both smaller than the axial length of the stretching section.

8. The centrifugal compressor according to claim 6, characterized in that: The pull rod (5) further includes a transition section (56) respectively arranged between the rear threaded section (51) and the rear cylindrical section (52), and between the front cylindrical section (54) and the front threaded section (55); the transition section (56) includes a straight section, and the straight section of the transition section (56) between the rear threaded section (51) and the rear cylindrical section (52) is respectively connected to the rear threaded section (51) and the rear cylindrical section (52) via a circular arc section (57); the straight section of the transition section (56) between the front cylindrical section (54) and the front threaded section (55) is respectively connected to the front cylindrical section (54) and the front threaded section (55) via a circular arc section (57).

9. The centrifugal compressor according to claim 8, characterized in that: The outer diameter of the stretching section (53) is smaller than the outer diameters of the rear thread section (51), the front thread section (55) and the transition section (56), and / or the roughness Ra of the stretching section (53) is less than or equal to 0.4 μm.

10. The centrifugal compressor according to claim 3, characterized in that: The outer periphery of the end cover (431) is sleeved with a bushing (9), and the impeller (6) is sleeved on the outer periphery of the end cover (431) and abuts against the axial end of the bushing (9).

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