Centrifugal air compressor

Abstract

The present application relates to a centrifugal air compressor comprising: a volute having a fluid inlet for sucking air and a fluid outlet for discharging air; the centrifugal impeller is accommodated in the volute; an impeller shaft centrally mounted to the impeller and rotating together with the impeller; the motor is used for driving the impeller shaft and the impeller to rotate so as to convey air from the fluid inlet to the fluid outlet under the action of centrifugal force; the motor is provided with a stator and a motor shaft which can rotate relative to the stator and serves as a rotor, one end face of the motor shaft is exposed to cooling air from a cooling air flow channel at a cooling loop outlet of the air compressor, and the motor shaft is provided with an air flow guiding structure used for limiting the flowing path of the cooling air on the section close to the end face. According to the thrust bearing, the airflow guiding structure is additionally arranged on the motor shaft, air flowing to the end face of the shaft is reduced, pressure acting on the end face of the shaft is reduced, and therefore axial force acting on the motor shaft is reduced, and robustness of the thrust bearing is improved.

Description

Technical Field

[0001] The present application relates to air compressor technology, and more particularly to a centrifugal air compressor. Background Art

[0002] Air compressors are widely used in many places where air needs to be pressurized or transported. In particular, centrifugal air compressors have a centrifugal impeller located within a volute. Through the centrifugal force generated by the rotation of the impeller, low-pressure air is inhaled from one end in the axial direction, and the air is output laterally by means of the centrifugal force. The impeller shaft is driven by an electric motor. For a single-stage compressor, the impeller shaft and the motor shaft are made integrally. Such a compressor often uses the method of high-pressure air cooling to cool each moving part of the motor. Thus, high-pressure cooling air is also introduced to the shaft end of the motor shaft opposite to the impeller, applying a relatively high pressure to the end of the motor shaft opposite to the impeller. At the shaft end of the impeller shaft integrally formed with the motor shaft, a relatively low pressure is exerted by the gas at the gas inlet.

[0003] For such a single-stage air compressor, in the existing structure, the axial force applied to the thrust bearing of the motor shaft is always very high. This is caused by the large difference between the relatively low pressure from the inlet side of the air compressor (one side of the impeller shaft) and the relatively high internal cavity pressure from the end face of the motor shaft (the side of the motor shaft away from the impeller). The large axial pressure acting on the thrust bearing has an adverse effect on the performance of the thrust bearing and even the entire compressor.

[0004] Therefore, there is a need to provide an improved centrifugal air compressor having a structure that can reduce the increase in axial force caused by the pressure difference at both ends of the rotating shaft. Summary of the Utility Model

[0005] The present application aims to provide a centrifugal air compressor having a structure that can effectively reduce the axial force acting on the rotating shaft.

[0006] To achieve the above object, the present application provides a centrifugal air compressor, comprising: a volute having a fluid inlet for inhaling air and a fluid outlet for discharging air; a centrifugal impeller accommodated within the volute; an impeller shaft centrally mounted to the impeller and rotating together with the impeller; an electric motor for driving the impeller shaft and the impeller to rotate to transport air from the fluid inlet to the fluid outlet by the action of centrifugal force; the electric motor having a stator and a motor shaft as a rotor rotatable relative to the stator, one end face of the motor shaft being exposed to the cooling air in the cooling gas flow path at the outlet of the cooling circuit of the air compressor, and an air flow guiding structure for restricting the flow path of the cooling gas being provided on the section of the motor shaft near the end face.

[0007] Optionally, the motor shaft and the impeller shaft are coupled to each other through a coupling.

[0008] Alternatively, the motor shaft and the impeller shaft are of an integral structure.

[0009] Optionally, the section of the motor shaft is axially outside the radial bearing that mounts the motor shaft to the motor end cover, and the air flow guiding structure is provided on the circumferential surface of the section of the motor shaft.

[0010] Optionally, the air flow guiding structure includes a bushing that is mounted on the motor shaft by an interference fit and is located between the motor shaft and the motor end cover to rotate together with the motor shaft.

[0011] Optionally, the bushing has a groove extending in the circumferential direction on its circumferential surface, and the air flow guiding structure includes a piston ring installed in the groove and spaced apart from the bushing by a certain gap.

[0012] Optionally, the piston ring is in an annular shape with a notch, and the piston ring has elasticity by means of the notch.

[0013] Optionally, after the air flow guiding structure is installed on the motor end cover together with the motor shaft, the piston ring elastically abuts against the motor end cover, is held by the motor end cover and is movable relative to the bushing.

[0014] Optionally, after the bushing and the piston ring are installed on the motor end cover, the gap formed between the piston ring and the groove of the bushing is less than 0.1 mm.

[0015] Optionally, the bushing and the piston ring are made of the same or different metal materials.

[0016] According to the present application, by adding a piston ring and a bushing to the right end of the rotating shaft of the air compressor, the air flowing to the shaft end surface is reduced, so that the pressure acting on the shaft end can be lower than the limit value, thereby reducing the axial force acting on the rotating shaft, improving the robustness of the air bearing, and prolonging the service life of the air compressor. Description of the Drawings

[0017] The above and other aspects of the present application will be understood more clearly with reference to the following drawings. It should be noted that the drawings are only schematic and not drawn to scale. In the drawings:

[0018] Figure 1 A cross-sectional view of a centrifugal air compressor according to the present application is schematically shown;

[0019] Figure 2 An enlarged detailed structural schematic diagram of the motor end of a centrifugal air compressor according to the present application is schematically shown;

[0020] Figure 3 Schematically shows a cross-sectional schematic view of an air flow guiding structure including a bushing and a piston ring installed at the motor end in a centrifugal air compressor according to the present application;

[0021] Figure 4 Schematically shows Figure 3 A perspective schematic view of the shown air flow guiding structure including a bushing and a piston ring. Detailed Description of the Preferred Embodiments

[0022] The preferred embodiments of the present application will be described in detail below in conjunction with examples. Those skilled in the art should understand that these embodiments do not impose any limitation on the present application, and the features in each embodiment can be combined with each other. In different drawings, the same components are denoted by the same reference numerals, and for the sake of brevity, some components are omitted, but this does not mean excluding other components. It should be understood that the dimensions, proportional relationships, and the number of components in the drawings do not limit the present application.

[0023] Figure 1 Shows a cross-sectional schematic view of a centrifugal air compressor according to the present application. Although a centrifugal air compressor is used as an example in the present application for detailed description, it is not limited thereto, and it can also be an air compressor based on other working principles, such as a piston air compressor, etc., which can also use the air flow guiding structure in the present application to adjust the pressure difference acting on the two end faces of the rotating shaft.

[0024] The centrifugal air compressor according to the present application includes a compressor section 10 and a motor 20. The motor 20 is associated with the compressor section 10 to drive the impeller 12 in the compressor section 10 to rotate through the rotation of the rotor in the motor 20, so as to suck a fluid such as air from the fluid inlet, and then be transported to the fluid outlet under the action of centrifugal force, thereby completing the transportation of the fluid.

[0025] Specifically, as Figure 1 shown, the compressor section 10 has a volute 11 and a centrifugal impeller 12 accommodated in the volute 11. The volute 11 has a fluid inlet 13 extending along the axial direction and a fluid outlet 14 extending tangentially. The impeller 12 is centered and fixed to the impeller shaft 15 and rotates together with the impeller shaft 15. When the impeller shaft 15 and the impeller 12 rotate, a fluid such as air is sucked from the fluid inlet 13, and then is thrown out from the fluid outlet 14 under the action of the centrifugal force generated by the rotation of the centrifugal impeller 15 and transported to a downstream position that requires high-pressure air.

[0026] The motor 20 has a generally cylindrical motor housing 21 and a stator 22 accommodated in the motor housing 21. The stator 22 has a stator core 24. The motor 20 further includes a motor shaft 25 having permanent magnets and can rotate relative to the stator 22 as a rotor.

[0027] The motor shaft 25 can be coupled to the impeller shaft 15 through a coupling, for example, so as to transmit the rotational torque of the motor shaft 25 to the impeller shaft 15 to drive the impeller shaft 15 to rotate together.

[0028] Optionally, the motor shaft 25 can also be integrally formed with the impeller shaft 15 to form a single unit. In this way, the impeller shaft 15 can be directly driven by the motor shaft 25 of the motor 20 to rotate.

[0029] In this application, the whole formed by the impeller shaft 15 and the motor shaft 25 can be collectively referred to as the rotating shaft, especially when the impeller shaft 15 and the motor shaft 25 are in an integral structure.

[0030] The motor 20 also has a motor end cover 26 detachably connected to the motor housing 21 to jointly enclose the stator 22 and the motor shaft 25 therein with the motor housing 21. Both ends of the motor shaft 25 are respectively installed on the motor housing 21 and the motor end cover 26 through bearings. For example, Figure 1 on the left side, the motor shaft 25 can be installed on the motor housing 21 through a thrust bearing 36, while Figure 1 on the right side, the motor shaft 25 can be installed on the motor end cover 26 through a radial bearing 27, and the radial bearing 27 can be a foil air bearing, for example. At a position corresponding to the right end of the motor shaft 25, outside the motor end cover 26, there is also a cover plate 28. The cover plate 28 and the motor end cover 26 can be detachably connected through fasteners such as screws to close the motor shaft hole on the motor end cover 26.

[0031] Figure 2 A detailed structural diagram of the connection between the right end portion of the motor shaft 25 and the motor end cover 26 is shown in detail in

[0032] During the operation of the centrifugal air compressor, the rotation of the motor 20 will generate a large amount of heat. Therefore, it is necessary to cool each component. Usually, the centrifugal air compressor adopts an air cooling method. For example, cooling circuits are provided in both the motor housing 21 and the motor end cover 26. Figure 2 The cooling air flow path 31 shown in

[0033] Therefore, on the end face of the rotating shaft composed of the motor shaft 25 and the impeller shaft 15 close to the impeller 15, that is, on the end face on the fluid inlet 13 side, the lower pressure exerted by the inlet fluid of the air compressor acts, while on the end face of the rotating shaft composed of the motor shaft 25 and the impeller shaft 15 far from the impeller, that is, on the end face 29 on the right side of the motor shaft 25, the higher back pressure from the cooling air passage 31 acts. In this way, axial forces generated due to the pressure difference will appear at both ends of the rotating shaft, and this axial force will act on the thrust bearing 36. Therefore, for a single-stage centrifugal air compressor, such a design will always result in a very high axial force exerted on the thrust bearing 36 of the motor shaft 25, which is disadvantageous for the operating stability of the thrust bearing 36 in the motor and the operation of the entire compressor.

[0034] For this reason, in this application, on the right end of the motor shaft 25, on the section 32 outside the radial bearing 27, an air flow guiding structure 30 is provided, and the air flow guiding structure 30 is arranged between the motor shaft 25 and the motor end cover 26.

[0035] As Figure 2 shown, the motor end cover 26 has a hole for the motor shaft 25 to be inserted, and the hole is divided into two stepped sections, namely a large-diameter hole 261 and a small-diameter hole 262. The large-diameter hole 261 is for the radial bearing 27 on the motor shaft 25 to be inserted. The radial bearing 27 has a bearing body 271 and a stop portion 272 radially protruding from the bearing body 271. When installing the motor shaft 25, the bearing body 271 of the radial bearing 27 is installed between the large-diameter hole 261 and the motor shaft 25 to rotatably hold the motor shaft 25, enabling the motor shaft 25 to rotate relative to the motor end cover 26. At the same time, the stop portion 272 abuts against the wall of the motor end cover 26, thereby restricting the axial movement of the radial bearing 27 and the motor shaft 25.

[0036] As described above, at one end of the motor shaft 25 close to the impeller 12, a thrust bearing 36 is provided, and the thrust bearing 36 axially bears the axial force exerted by the motor shaft 25.

[0037] The air flow guiding structure 30 of this application is arranged between the motor shaft 25 and the small-diameter hole 262 of the motor end cover 26, and thus is arranged on the air flow path from the cooling gas passage 31 to the end face 29 of the motor shaft 25 to restrict and adjust the gas flow rate in the air flow path.

[0038] On the outer side of the motor end cover 26, at the small-diameter hole 262, the motor 20 is also provided with a cover plate 28 for closing the small-diameter hole 262 on the motor end cover 26. The cover plate 28 can be fastened to the motor end cover 26 by, for example, screws and is sealingly connected relative to the motor end cover 26. For example, on the surface of the cover plate 28 facing the motor end cover 26, a circumferentially extending groove 35 is provided, and a sealing ring can be arranged in the groove 35 to seal the entire motor shaft hole when the cover plate 28 is installed onto the motor end cover 26. The sealing ring can be, for example, an O-ring or other similar sealing rings such as a lip seal.

[0039] Figure 3 and Figure 4 Specifically shown are a cross-sectional view and a perspective view of the air flow guiding structure 30.

[0040] The air flow guiding structure 30 includes a bushing 311 and a piston ring 312 that cooperates with the bushing 311. The bushing 311 is annular and has an inner hole 314. The diameter of the inner hole 314 is smaller than the diameter of the section 32 of the motor shaft 25, so that the bushing 311 can be installed onto the motor shaft 25 by interference fit and thus is non-rotatable relative to the motor shaft 25, that is, the bushing 311 rotates together with the motor shaft 25.

[0041] On the outer peripheral surface of the bushing 311, a groove 315 extending along the circumferential direction is provided. Preferably, the groove 315 is centrally positioned in the axial direction, that is, the length direction of the bushing 311, but is not limited thereto and can also be provided at other positions in the length direction.

[0042] As Figure 4 shown, the piston ring 312 is an incomplete ring and has an opening 313, such that the piston ring 312 can be elastically deformed in the radial direction. This elastic deformation enables the piston ring 312 to be installed into the groove 315 of the bushing 311 when the opening 313 is made larger and to rebound to its initial position after installation. When the piston ring 312 is in the installed position, the outer diameter of the piston ring 312 is larger than the outer diameter of the bushing 311, that is, the piston ring 312 protrudes from the outer peripheral surface of the bushing 311, and the outer diameter of the piston ring 312 when installed is larger than the inner diameter of the small-diameter hole 262 in the motor end cover 26.

[0043] The inner diameter of the piston ring 312 is larger than the diameter of the bottom of the groove 315, such that there is a gap 317 between the inner surface of the piston ring 312 and the bottom of the groove 315.

[0044] As Figure 3As shown, the axial width w1 of the piston ring 312 is smaller than the axial width w2 of the groove 315, so that when the piston ring 312 is installed in the groove 315 of the bushing 311, a clearance 316 and a clearance 318 are respectively formed between the two end faces of the piston ring 312 and the two side walls of the groove 315. That is to say, when the piston ring 312 is installed in the bushing 311, there is no contact between the piston ring 312 and the bushing 311, and there are clearances 316, 317, and 318.

[0045] The size of each of the clearances 316, 317, and 318 is not greater than 0.1 mm to effectively limit the fluid flow rate.

[0046] The bushing 311 and the piston ring 312 in this application can be made of the same material or different materials. For example, the bushing 311 and the piston ring 312 can be made of wear-resistant metal materials.

[0047] During installation, the piston ring 312 can be first expanded along the opening 313 and installed in the groove 315 of the bushing 311. The piston ring 312 is restored to form the assembled air flow guiding structure 30, and then the air flow guiding structure 30 is installed on the section 32 of the motor shaft 25, so that an interference fit is formed between the motor shaft 25 and the bushing 311. Then the right end of the motor shaft 25 is installed in the motor end cover 26, so that the radial bearing 27 is located between the motor shaft 25 and the large-diameter hole 261, and the air flow guiding structure 30 is located between the motor shaft 25 and the small-diameter hole 262. Since the piston ring 312 protrudes from the circumferential surface of the bushing 311 after being installed in the groove 315, after the motor shaft 25 is installed in the motor end cover 26, the outer surface of the piston ring 312 will be abutted against the wall of the small-diameter hole 262 due to the elasticity of the piston ring 312, so as to be fixed relative to the motor end cover 26 by the abutting force. In this way, because clearances 317, 316, and 318 are formed between the piston ring 312 and the bottom and side walls of the groove 315, during the rotation of the motor shaft 25, the bushing 311 and the piston ring 312 can rotate by being guided by the piston ring 312 in the groove 315.

[0048] With such an air flow guiding structure 30, during the operation of the centrifugal air compressor of the present application, the gas from the cooling gas flow passage 31 near the outlet of the cooling circuit needs to pass through the gaps 316, 317, 318 between the bushing 311 and the piston ring 312 to reach the end face 29 of the motor shaft 25. During this process, limited by the sizes of the gaps 316, 317, 318, the amount of gas reaching the end face 29 through each gap between the bushing 311 and the piston ring 312 is reduced, so that the gas pressure acting on the end face 29 is greatly reduced, and the pressure is reduced to below the limit value. Therefore, the axial force acting on the end face 29 of the motor shaft 25 is also reduced, thereby reducing the difference in the axial forces acting on the rotating shaft composed of the motor shaft 25 and the impeller shaft 15.

[0049] Since the difference in the axial forces on the rotating shaft is reduced, therefore, the force that is not conducive to the operating stability of the thrust bearing 36 acting on the thrust bearing 36 of the motor shaft 25 is also reduced, the service life of the thrust bearing 36 is improved, and the entire centrifugal air compressor can work reliably and stably.

[0050] As described above, although a centrifugal air compressor is described in the present application, it is not limited thereto. The air flow guiding structure 30 described in the present application can also be provided in other compressors that need to control the axial force acting on the rotating shaft by restricting the gas flow. Moreover, it can also be installed in any place where the pressure needs to be reduced, not necessarily limited to the motor shaft.

[0051] The above describes the case where the gaps 316, 317, 318 between the piston ring 312 and the groove 315 are equal, but it is not limited thereto. It can also be set so that the three gaps 316, 317, 318 have different sizes. The sizes of the gaps only need to be set so that the flow of the fluid is restricted, but the flow of the fluid cannot be blocked.

[0052] The present application has been described in detail in combination with specific embodiments. Obviously, the above description and the embodiments shown in the drawings should be understood as exemplary and do not constitute a limitation to the present application. For those skilled in the art, various variations or modifications can be made without departing from the spirit of the present application, and these variations or modifications do not depart from the scope of the present application.

Claims

1. A centrifugal air compressor, characterized in that, Comprising: A volute casing (11) having a fluid inlet (13) for inhaling air and a fluid outlet (14) for discharging air; A centrifugal impeller (12) accommodated in the volute casing (11); An impeller shaft (15) centrally mounted to the impeller (12) and rotating together with the impeller (12); A motor (20) for driving the impeller shaft (15) and the impeller (12) to rotate so as to convey air from the fluid inlet (13) to the fluid outlet (14) by the action of centrifugal force; The motor (20) has a stator (22) and a motor shaft (25) as a rotor rotatable relative to the stator. One end face (29) of the motor shaft (25) is exposed to the cooling air in the cooling gas flow path (31) at the outlet of the cooling circuit of the air compressor. An air flow guiding structure (30) for restricting the flow path of the cooling gas is provided on a section (32) of the motor shaft (25) near the end face (29).

2. The centrifugal air compressor according to claim 1, wherein, The motor shaft (25) and the impeller shaft (15) are coupled to each other by a coupling.

3. The centrifugal air compressor according to claim 1, wherein, The motor shaft (25) and the impeller shaft (15) are of an integral structure.

4. The centrifugal air compressor according to claim 1, characterized in that, The section (32) of the motor shaft (25) is axially outside the radial bearing (27) that mounts the motor shaft (25) to the motor end cover (26). The air flow guiding structure (30) is provided on the circumferential surface of the section (32) of the motor shaft (25).

5. The centrifugal air compressor according to claim 1, characterized in that, The air flow guiding structure (30) includes a bushing (311) that is installed on the motor shaft (25) by interference fit and is located between the motor shaft (25) and the motor end cover (26) to rotate together with the motor shaft (25).

6. The centrifugal air compressor according to claim 5, wherein, The bushing (311) has a groove (315) extending in the circumferential direction on the circumferential surface. The air flow guiding structure (30) includes a piston ring (312) installed in the groove (315) and spaced apart from the bushing (311) by a certain gap.

7. The centrifugal air compressor according to claim 6, characterized in that, The piston ring (312) is in an annular shape with a notch (313), and the piston ring (312) has elasticity by means of the notch (313).

8. The centrifugal air compressor according to claim 7, wherein The piston ring (312) elastically abuts against the motor end cover (26) after the air flow guiding structure (30) is installed to the motor end cover (26) together with the motor shaft (25), is held by the motor end cover (26) and is movable relative to the bushing (311).

9. The centrifugal air compressor according to claim 7, characterized in that, After the bushing (311) and the piston ring (312) are installed to the motor end cover (26), the gap formed between the piston ring (312) and the groove (315) of the bushing (311) is less than 0.1 mm.

10. The centrifugal air compressor according to claim 6, characterized in that, The bushing (311) and the piston ring (312) are made of the same or different metal materials.

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