Centrifugal compressor

Abstract

The utility model relates to a centrifugal compressor, which is provided with ribs or grooves processed on a workpiece shaft which aims to rotate around a longitudinal axis and / or on an air or gas axial bearing which forms a part of the workpiece shaft. The utility model relates to a centrifugal compressor comprising a shaft, a rotor structure with at least one permanent magnet of an electric motor intended to be mounted on or in the shaft in order to rotatably drive the shaft, the centrifugal compressor further comprising: a housing having a fluid inlet and a compressed fluid outlet; a first compressor wheel and a second compressor wheel, the first compressor wheel and the second compressor wheel being intended to be mounted at both ends of the shaft in the housing; a front air or gas radial bearing intended to be mounted on a first end of the shaft; and / or a rear air or gas radial bearing intended to be mounted on a second end of the shaft, in which all ribs or grooves are obtained on the rotatably driven shaft and / or on a workpiece portion of a disk of the axial bearing of the shaft.

Description

Technical Field

[0001] The utility model relates to a method for machining ribs or grooves on a shaft for an air or gas bearing of a high-speed centrifugal fluid compressor. The compressor is a two-stage compressor and includes a housing that has a fluid inlet and a compressed fluid outlet and encloses a shaft rotatably mounted about a longitudinal axis. A first compressor impeller and a second compressor impeller are mounted back-to-back on the shaft, with the first compressor impeller constituting a first compression stage and the second compressor impeller constituting a second compression stage. The centrifugal compressor further includes a motor (preferably, a synchronous electric motor) that is positioned between the first compressor impeller and the second compressor impeller and is arranged to rotate the shaft. At least one air or gas axial bearing forms part of the shaft and is provided at one end of the shaft. In addition, a front air or gas radial bearing can be mounted on the first end of the shaft, and a rear air or gas radial bearing can be mounted on the second end of the shaft. Background Art

[0002] Fluid compressors are commonly referred to as turbo compressors or centrifugal compressors. They include a stator and a rotor that form a permanent magnet synchronous motor (brushless motor). They are capable of reaching very high speeds, such as 100,000 to 500,000 rpm. The motor drives the compressor impeller at high speed, and the compressor impeller compresses the fluid at that high speed. The fluid can be air, gas, refrigerant, or any other suitable fluid. By using two compressor impellers, the fluid is compressed twice.

[0003] These compressors can be used, for example, in mobile HVAC (heating, ventilation, and air conditioning) systems with refrigerant gas, such as in electric, hybrid, or hydrogen-powered vehicles. These compressors can also be used in fixed systems (such as heat pumps) with refrigerant gas.

[0004] These compressors typically include a first circuit for circulating the fluid to be compressed and a second circuit for circulating a cooling liquid for cooling the compressor (and more particularly, on the one hand, the motor and the air or gas bearings supporting the motor shaft, and on the other hand, the electronic components). More specifically, causing the motor to rotate at high speed causes it to heat up significantly, such that the compressor components need to be cooled to prevent damage to them. These circuits are typically provided inside the compressor itself, at least in the case of the cooling circuit. During the operation of the compressor, especially during high-speed operation, there are no measures to promote the flow of cooling gas or air, which constitutes a disadvantage. In addition, the air or gas bearings supporting the rotor shaft are not designed to support the rotor shaft frictionlessly, which results in significant heat generation when the rotor rotates at high speed, which constitutes another disadvantage.

[0005] In addition, grooves or ribs are known to be made on air or gas bearings to facilitate air or gas flow and to generate pressure and cooling. However, the grooves are produced by laser machining without any specific arrangement, which constitutes a drawback as the machining time is too long and thus its cost is too high. SUMMARY OF THE UTILITY MODEL

[0006] An object of the present utility model is to overcome the various drawbacks mentioned above by means of a method for rapidly producing grooves or ribs on a rotor shaft for air or gas bearings, which air or gas bearings include air or gas axial bearings forming part of the shaft. The grooves or ribs on the shaft are arranged in such a way that when the shaft of the compressor rotates at high speed in each bearing, gravity is overcome and the rotating rotor shaft is allowed to be held without mechanical contact on the air or gas flow in the radial bearing and thus with almost no friction.

[0007] For this purpose, the present utility model relates to a method for machining ribs or grooves on a shaft intended to rotate about a longitudinal axis of a centrifugal compressor and / or on an air or gas axial bearing forming part of the shaft, the method comprising the features of the present invention.

[0008] Specific steps of the method are defined in a preferred embodiment.

[0009] An advantage of the method for machining ribs or grooves on the shaft and / or axial bearing of the workpiece shaft of the compressor in the machining unit is that all the ribs or grooves are obtained together (en une fois) by the machining tool on the workpiece part of the shaft being driven to rotate, the machining tool moving back and forth from the starting point to the end point of the workpiece part of the shaft. To accomplish this, the reciprocating movement of the machining tool is synchronized by means of a sine program (programmation ) provided in the machining unit and by means of the desired arrangement of the ribs or grooves to be produced on the part of the shaft.

[0010] An advantage of the method for machining ribs or grooves on the axial bearing of the workpiece shaft of the compressor in the machining unit is that all the ribs or grooves are obtained on one or both surfaces of the disk of the axially bearing of the shaft being rotatably driven.

[0011] During the machining of the shaft and / or the axial bearing of the shaft, while the machining tool performs a reciprocating movement, the shaft or the tool holder carrying the machining tool also shifts along the longitudinal machining direction.

[0012] Compare the reciprocating motion of the tool with a piezoelectric oscillator, where the oscillation frequency can be varied according to the programming of the machining unit to speed up or slow down the reciprocating motion of the tool, thereby obtaining the desired ribs or grooves. During the reciprocating motion, the tool is in the machining position and contacts the shaft or the axial bearing of the shaft at one time and does not contact the shaft or the axial bearing of the shaft at another time.

[0013] The workpiece shaft is attached to the rotor structure of an electric motor that drives its rotation, and at least one air or gas axial bearing forms part of the shaft and is provided at the first end of the shaft between the compressor impeller and the air or gas radial bearing. By a specific tool for machining ribs or grooves in the axial bearing, ribs or grooves can be produced on one surface or preferably on both surfaces of the disk of the air or gas axial bearing. However, the same machining tool can be used to machine ribs or grooves on a part of the shaft for the radial bearing and on one or both surfaces of the disk of the air or gas axial bearing.

[0014] One advantage of the method for machining ribs or grooves in the machining unit is that the ribs or grooves are very quickly produced in less than 1 minute on each workpiece part of the shaft for the air or gas radial bearing and with very high precision. This also applies to the grooves or ribs produced on one or both surfaces of the disk of the rotatably driven air or gas axial bearing. The machining tool is harder than the material of the shaft or the air or gas axial bearing.

[0015] Therefore, the sine function makes it possible to achieve synchronization between the rotation of the shaft and the movement of the machining tool or the shaft in the longitudinal direction. The frequency and amplitude of the sine function are selected as a function of the geometry of the groove, the number of grooves, the rotational speed of the shaft, and the speed of the longitudinal displacement.

[0016] As explained above, the machining unit can be programmed to rotate simultaneously and synchronously with the machining tool according to a sine program or function to obtain a rib or groove arrangement on each workpiece part of the shaft for each air or gas radial bearing and for the air or gas axial bearing.

[0017] Due to such machining of ribs or grooves (which are preferably V-shaped with an orientation change of each rib or groove in the center of each machined part on the shaft), the shaft rotating at high speed can be held in the compressor, in an air or gas radial bearing without mechanical contact. Thus, due to the pressure of the air or gas passing through the grooves or ribs caused by the high-speed rotation of the shaft, the shaft is held in each radial bearing with little friction. Starting from as low as 6,000 rpm, the air or gas pressure in each aerodynamic radial bearing causes the shaft to no longer make mechanical contact with the static radial bearing, thus avoiding any mechanical friction. It goes without saying that the faster the shaft rotates, the greater the gas pressure in the radial bearing, which automatically generates more air or gas friction.

[0018] The grooves or ribs are machined by a machining unit and a machining tool according to a sine program and the desired arrangement of the grooves or ribs, so as to reverse the orientation of the grooves or ribs on the shaft that is substantially towards the inner half of each static radial bearing placed above the ribs. This generates an air or gas pressure, and the faster the shaft rotates, the greater this air or gas pressure becomes.

[0019] Due to the generation of ribs or grooves on the air or gas radial bearing, such a high-speed centrifugal fluid compressor can rotate at a very high speed without overheating.

[0020] An axial bearing is also provided between the first compressor impeller and the first radial bearing. Grooves or ribs are made in a spiral form at the outer periphery on the front and rear surfaces of the disk of the axial bearing. As the shaft rotates, an air film is generated by the grooves to hold the axis in a longitudinally well-centered position.

[0021] The utility model at least includes the following solutions:

[0022] Solution 1. A centrifugal compressor, the centrifugal compressor having ribs or grooves machined on a workpiece shaft intended to rotate about a longitudinal axis and / or on an air or gas axial bearing forming part of the workpiece shaft, and a rotor structure with at least one permanent magnet of an electric motor is intended to be mounted on or in the shaft so as to rotatably drive the shaft, the centrifugal compressor further comprising: a housing having a fluid inlet and a compressed fluid outlet; a first compressor impeller and a second compressor impeller, the first compressor impeller and the second compressor impeller being intended to be mounted at two ends of the shaft in the housing; a front air or gas radial bearing intended to be mounted on the first end of the shaft; and / or a rear air or gas radial bearing intended to be mounted on the second end of the shaft,

[0023] Characterized in that all of the ribs or grooves are obtained on the rotatably driven shaft and / or on the workpiece part of the disk of the axial bearing of the shaft.

[0024] Solution 2. The centrifugal compressor according to Solution 1, wherein the air or gas axial bearing is intended to be generated on the workpiece shaft before machining the ribs or grooves on the shaft.

[0025] Solution 3. The centrifugal compressor according to Solution 2, characterized in that the air or gas axial bearing is intended to be generated by obtaining a blank of a shaft having a diameter substantially equal to the desired diameter of the axial bearing, and to a first position of the shaft, the first position corresponding to the position of the surface of the disc of the axial bearing to be generated.

[0026] Solution 4. The centrifugal compressor according to Solution 3, characterized in that the second surface of the axial bearing is intended to be generated from the opposite end of the shaft in a second position of the axial bearing.

[0027] Solution 5. The centrifugal compressor according to Solution 1, wherein the shaft is made of tungsten carbide or ceramic so as to be machined by the head of a machining tool made of diamond to generate all the ribs or grooves.

[0028] Solution 6. The centrifugal compressor according to Solution 5, characterized in that there is a change in the orientation of the ribs or grooves between a first workpiece portion at a first end of the shaft and a second workpiece portion at a second end of the shaft, and the ribs or grooves are generated as V-shaped grooves along the lengths of a first machining portion and a second machining portion.

[0029] Solution 7. The centrifugal compressor according to Solution 1, wherein the workpiece is the air or gas axial bearing in the form of a disc, the disc integrally forming part of the shaft, characterized in that the ribs or grooves and their arrangement are intended to be generated together on a first surface of the disc.

[0030] Solution 8. The centrifugal compressor according to Solution 7, characterized in that all the ribs or grooves are intended to be generated together on a second surface of the disc.

[0031] Solution 9. The centrifugal compressor according to Solution 8, characterized in that all the ribs or grooves are generated in a spiral form having the same orientation or two different orientations on the two surfaces so as to generate an air film via the grooves when the shaft is rotated to keep the axis in a longitudinally well-centered position during the operation of the centrifugal compressor. Description of the Drawings

[0032] The objects, advantages and features of the present invention will be better understood when reading the following detailed description of embodiments of the present invention, which is given as a non-limiting example and illustrated in the accompanying drawings, wherein:

[0033] Figure 1 shows a longitudinal sectional view along axis A-A of a high-speed centrifugal compressor according to the present utility model,

[0034] Figure 2a and Figure 2b shows a longitudinal sectional view along axis A-A of a shaft with a compressor impeller, aerodynamic axial and radial bearings, and a permanent magnet rotor structure according to the present utility model, and a plan view as seen from the side of the first compressor impeller and the axial bearing forming part of the shaft,

[0035] Figure 3 is Figure 2a and Figure 2b a three-dimensional view of the components in and , which shows grooves or ribs in each static radial bearing (shown raised above the shaft) according to the present utility model and on the axial bearing forming part of the shaft,

[0036] Figure 4 is a longitudinal sectional view of a machining unit according to the present utility model for machining grooves or ribs on an air or gas axial bearing forming part of a compressor shaft using a first machining component, and for machining grooves or ribs on two parts of the shaft for the radial bearings using a second machining component, and

[0037] Figure 5 is a longitudinal sectional view of an alternative embodiment of a machining unit according to the present utility model for machining grooves or ribs on an air or gas axial bearing forming part of a compressor shaft using a single machining component, and for machining grooves or ribs on two parts of the shaft for the radial bearings. Detailed Description of the Invention

[0038] In this specification, all components forming part of a centrifugal compressor that are well known in the prior art are only briefly described herein, since the present utility model essentially relates to the manner of generating ribs or grooves on two parts of a shaft to be covered respectively by two static air or gas radial bearings, or to the manner of generating ribs or grooves on an air or gas axial bearing forming part of the shaft.

[0039] Figure 1Shows a cross-section of the high-speed centrifugal compressor 1 along the longitudinal axis A-A. In the housing 2, the centrifugal compressor includes: a shaft 7 made of tungsten carbide or ceramic, which is mounted so as to rotate about the longitudinal axis A-A passing through the front surface 2b and the rear surface 2c; a first centrifugal compressor impeller 8 and a second centrifugal compressor impeller 10 mounted back-to-back at each end of the shaft 7, the first compressor impeller 8 constituting the first compression stage, and the second compressor impeller 10 constituting the second compression stage. In particular, in this embodiment, the shaft 7 is hollow and encloses a threaded rod 11, one of the compressor impellers 8, 10 being threadedly connected to each end thereof, thereby enabling easy installation and removal of these compressor impellers. Thus, the two compressor impellers 8 and 10 are driven on the same shaft 7, which improves the energy efficiency and eliminates the need for a gearbox. The rear portions of the compressor impellers 8 and 10 include labyrinth seals to control the pressure in the compressor and balance the axial force.

[0040] The housing 2 further encloses an electric motor, which is preferably synchronous, positioned between the first compressor impeller 8 and the second compressor impeller 10 and arranged to rotate the shaft 7. The motor includes a stator 14 and a rotor structure 16, which interact with each other to form a synchronous electric motor (brushless motor) with at least one permanent magnet 16a. More particularly, the stator 14 is formed by a coil 14a and two ferrite elements 14b, which are mounted so as to be fixed relative to the housing 2. The rotor structure 16 includes one or more permanent magnets 16a, which are made integral with the shaft 7 (e.g., by bonding) and covered by a titanium lining 16b. A titanium flange 16c is attached (e.g., by bonding) to the lateral ends of the lining and ensures that the rotor resists centrifugal forces at high speeds.

[0041] The shaft 7 is rotatably mounted in the housing 2 about its longitudinal axis A-A by means of: at least one front radial bearing 18, a rear radial bearing 22, and an axial bearing 24, which forms an integral part of the shaft 7. The centrifugal compressor 1 includes a front radial bearing support 26 for carrying the front radial bearing 18 and a rear radial bearing support 28 for carrying the rear radial bearing 22, the front radial bearing support and the rear radial bearing support being arranged to be positioned around the shaft 7, respectively at the front and rear of the motor. At the rear, a scroll member 29 is also provided between the rear radial bearing support 28 and the rear cover 3c. The scroll member 29 includes an orifice that leads to a tangential fluid outlet 6 after compression. An axial bearing support 30 is also provided between the first compressor impeller 8 and the front radial bearing support 26 to carry the axial bearing 24, the axial bearing support being arranged to be positioned around the shaft 7. It is clear that the axial bearing can be provided at the rear of the motor.

[0042] The bearings are non-contact aerodynamic bearings in order to generate little friction. They do not require lubrication and only need little maintenance. More particularly, reference is made to Figure 2a , Figure 2b , Figure 3 , Figure 4 and Figure 5 . The axial bearing 24 is an aerodynamic bearing. According to the present utility model, the axial bearing itself forms part of the shaft 7, that is to say, it is formed simultaneously with the shaft 7 and from the same base material so as to be formed integrally with the shaft 7 in the form of a one-piece unit at the end of production.

[0043] The axial bearing is constituted by a disc which includes, on at least one of its surfaces, first grooves 24a arranged to generate an air film, which first grooves are preferably helical over an annular region at the outer periphery. Preferably, the axial bearing 24 includes preferably helical grooves or ribs 24a at the outer periphery of the disc of the axial bearing 24 on the front surface and the rear surface, and these grooves or ribs are obtained by the machining process explained below with reference to Figure 4 and Figure 5 . The orientation of the grooves or ribs 24a on the front surface can be different from the orientation of the grooves or ribs 24a on the rear surface, or can be the same. The axial bearing 24 with its grooves or ribs 24a keeps the rotating shaft 7 longitudinally centered by generating an air film from the front surface and the rear surface. The front radial bearing 18 and the rear radial bearing 22 are aerodynamic bearings, and the shaft 7 has second grooves or ribs 32 facing the front radial bearing 18 and the rear radial bearing 22, and these second grooves or ribs are arranged to generate an air or gas film when the shaft rotates in the air or gas radial bearings.

[0044] In Figure 2a and Figure 2b , it is still possible to see the first centrifugal compressor impeller 8 and the second centrifugal compressor impeller 10 mounted back-to-back at each end of the shaft 7. The rotor structure 16 of the electric motor with at least one permanent magnet 16a is mounted or fastened, for example, above or in the central part of the shaft 7 so as to rotatably drive the shaft and the air or gas axial bearing 24 which forms part of the shaft 7 about the longitudinal axis A-A. The front air or gas radial bearing 18 is mounted on the first end of the shaft 7, and the rear air or gas radial bearing 22 is mounted on the second end of the shaft 7, as shown in Figure 2a .

[0045] As shown in Figure 3 , at both ends of the shaft 7, there is a first part of the machined ribs or grooves 32, and at the other end, there is a second part of the machined ribs or grooves 32. The rotor structure 16 with at least one permanent magnet 16a is attached to the shaft 7 in a central position for the electric motor.

[0046] Figure 3 A three-dimensional view of the shaft 7 is shown, where the axial bearing 24 is located at the first end of the shaft 7. At both ends of the shaft 7, a first part of the rib or groove 32 can be seen, where the first radial bearing 18 is shown at a height above the rib or groove 32, and a second part of the rib or groove 32 can be seen, where the second radial bearing 22 is shown at a height above these rib or grooves 32. Ribs or grooves 24a are also shown on the surface of the disk of the air or gas axial bearing 24 that forms part of the shaft 7. The ribs or grooves 24a having a certain depth are produced in an annular area starting from the outer circumference of the disk and leading towards the center of the disk. The ribs or grooves 24a and their arrangement are programmed (especially in a machining unit) to activate the machining tool to produce all the ribs or grooves together, that is, by moving the tool holder or the rotating disk along a single machining direction (e.g., from the outer circumference of the disk to the bottom of the annular area of the rib or groove). For example, starting from the outer circumference of the disk on one surface, the groove part is gradually formed by the reciprocating movement of the machining tool, and the reciprocating movement of the machining tool is synchronized with the machining unit rotating the disk at a given speed according to a sine program.

[0047] Using this program and combined with the controlled reciprocating movement of the machining tool, each starting part of all the grooves 24a is achieved by the rotation of the disk and the reciprocating movement of the machining tool. This operation is continuously repeated for the subsequent groove or rib parts, which are continuous from the first groove part to the end point or bottom of the annular area. By generating different ribs or grooves 24a on the disk 24 in this way, the machining time for each grooved surface of the disk is less than one minute, which is significantly different from the previous machining techniques using laser beams.

[0048] The machining unit is programmed to simultaneously and synchronously rotate the shaft 7 and the machining tool according to a sine program to obtain a determined arrangement of the ribs or grooves 32 on the first workpiece part of the shaft 7 for the front air or gas radial bearing 18. For example, on the same side as the first end of the shaft 7, starting from the starting part of the first workpiece part of the shaft and only along one machining direction, and up to the end point of the first part of the first end of the shaft 7, all the ribs or grooves 32 are machined together, which significantly reduces the machining time.

[0049] Therefore, it can be determined that the sine function does indeed achieve the synchronization between the rotation of the shaft 7 and the displacement of the machining tool or the shaft 7 in the longitudinal direction. The frequency and amplitude of the sine function are selected as a function of the geometry of the groove 32, the number of grooves 32, the rotational speed of the shaft, and the speed of the longitudinal displacement.

[0050] The specific arrangement of the ribs or grooves 32 produced on the first part of the first end of the shaft 7 is programmed in the machining unit. In a desired embodiment, the ribs or grooves 32 are each V-shaped, i.e., they include an orientation change starting substantially from the middle of the first workpiece part of the shaft 7. This ensures that the shaft, which will rotate at high speed in the compressor, is held in the air or gas radial bearings without mechanical contact. Starting from as low as 6,000 rpm, the air or gas pressure in each aerodynamic radial bearing causes the shaft to no longer make mechanical contact with the static radial bearings, thus avoiding any mechanical friction.

[0051] As a complement to Figure 1 , the compressor 1 includes a housing 2 made of aluminum, the top surface 2a of which is closed by a top cover 3a, and the front surface 2b and the rear surface 2c of which are closed by a front cover 3b and a rear cover 3c, respectively. The side surfaces 2d of the housing are joined at their bases to form a rear part 2e having a U-shaped cross-section.

[0052] The top cover 3a is located on the same side as the electronic components of the compressor. Thus, easy access to the electronic components integrated in the compressor is provided through the top cover 3a. The front cover 3b and the rear cover 3c are used to access the interior of the compressor (motor, rotor, bearings, etc.). A gasket is interposed between the top surface of the housing 2 and the top cover 3a. This gasket protects the electronic components from dust and moisture.

[0053] The housing 2 has an inlet 5 for the fluid to be compressed provided on the front cover 3b and a tangential outlet 6 for the compressed fluid provided on one of the side surfaces of the housing 2.

[0054] In Figure 1 , the housing 2 includes an inner housing that extends coaxially with the longitudinal axis A-A from end to end between the front surface 2b and the rear surface 2c of the housing 2 and receives the front radial bearing support 26 and the front radial bearing 18, the motor and its rotor structure 16 attached to the shaft 7, the rear radial bearing support 28 and the rear radial bearing 22, the second compressor impeller 10, and the scroll member 29. On the front surface 2b side, the inner housing is closed by the front cover 3b, which integrates the first compressor impeller 8, the axial bearing support 30, and the axial bearing 24. On the rear surface 2c side, the inner housing is closed by the rear cover 3c.

[0055] Furthermore, the following are advantageously provided: at least one orifice (e.g., the point given by reference numeral 57a), which is arranged to allow the fluid to be compressed circulating in the passage to enter the motor and circulate between the stator 14 and the rotor structure 16; and at least one orifice (e.g., the point given by reference numeral 57b), which is arranged to allow the fluid to be compressed to leave the motor after cooling the motor and rejoin the said passage.

[0056] Similarly, advantageously provided are the following: at least one orifice (e.g., Figure 1 the point given by reference numeral 59a in the figure), which is arranged to allow the fluid to be compressed circulating in the passage 54 to circulate near the axial bearing 24, the front radial bearing 18, and the rear radial bearing 22; and at least one orifice (e.g., corresponding to the same point given by reference numeral 57b), which is arranged to allow the fluid to be compressed to rejoin the passage 54 after cooling the axial bearing 24, the front radial bearing 18, and the rear radial bearing 22.

[0057] Thus, after entering the first compression stage through the inlet 5, the fluid to be compressed passes through the compressor section located between the first compression stage and the second compression stage along the longitudinal axis in the passage 54 to rejoin the second compression stage. As a result, before entering the second compression stage, the fluid to be compressed cools the inner wall 52 of the motor and the ferrite element 14b when passing between them and recovers the heat lost from the motor to improve the motor efficiency. In addition, the orifices 57a, 57b, 59a allow a slight deviation of the flow, so that the fluid to be compressed also circulates between the stator 14 and the rotor structure 16 and in the bearings to cool these components and recover the heat loss from the motor and the heat loss due to friction in the bearings.

[0058] The centrifugal compressor 1 allows for a very high rotational speed, which is in the range of 100,000 rpm to 500,000 rpm. It allows the fluid compressed in the first compression stage to substantially pass through the entire system to recover any waste heat, and in particular the waste heat from the motor, bearings, and electronic components, in order to improve its efficiency before entering the second compression stage (as the temperature of the fluid to be compressed increases, its pressure also increases). In addition, using only the fluid to be compressed to cool the compressor without the assistance of an additional cooling circuit and the arrangement of the electronic components for integrating the electronic devices into the housing in the compressor results in a very compact compressor. Therefore, the compressor according to the present utility model has a high rotational speed and a high compression ratio while occupying a small volume. For example, the compression ratio of the compressor according to the present utility model is greater than 3, and for dimensions L×W×H in cm of approximately 14×8×11 and a weight of only 1.6 kg, the power is approximately 4 kW.

[0059] For example, the compressor according to the present utility model can be used with air or gas to power a fuel cell or any other system using compressed air (industrial compressors, medical compressors, ships, etc.).

[0060] Using a refrigerant gas, the compressor according to the present utility model can be used in a mobile HVAC (heating, ventilation, and air conditioning) system, such as in an electric, hybrid, or hydrogen-powered vehicle.

[0061] The centrifugal compressor can also be used in a stationary system with a refrigerant gas, such as a heat pump.

[0062] The centrifugal compressor can also be used with natural gas.

[0063] Figure 4 A machining unit 100 is shown, which is used to produce ribs or grooves on parts of the first and second ends of the shaft 7, and to produce ribs or grooves on the first surface of the disk of the axial bearing 24 forming part of the shaft 7 or also on the second surface of the disk of the axial bearing 24 forming part of the shaft 7.

[0064] The machining unit 100 includes a lathe 130 having two main spindles 140, which are used to hold the shaft 7 at two ends of the shaft 7 and to rotate it at a determined rotational speed ω when machining ribs or grooves. The first main spindle 140 is located on the first vertical column or wall 102 of the machining unit 100, while the second main spindle 140 is located on the second vertical column or wall 103 opposite the first vertical column or wall 102. The two vertical walls 102, 103 of the machining unit 100 are connected by a base 101, in which means for guiding at least one tool holder 160 are arranged, and the at least one tool holder can carry at least one machining tool 120 or two machining tools 120, 121 or a plurality of other different machining tools. The means for guiding the tool holder 160 in the base 101 of the machining unit 100 can move in the longitudinal direction A-A, for example, on one or two guides (not shown) in the base 101.

[0065] In order to machine ribs or grooves on the first front part or the second rear part of the shaft 7 placed between the two main spindles 140 and rotatably driven about the longitudinal axis A-A, the tool holder 160 can be moved parallel to the shaft 7 and preferably horizontally therewith, so as to place the first machining tool 120 in the machining position, as already explained above. The first machining tool 120 is oriented perpendicular to the part of the shaft 7, so as to be able to machine ribs or grooves on one of the workpiece parts of the shaft 7. Subsequently, the tool holder 160 is again moved parallel to the shaft 7 towards the second workpiece part of the shaft.

[0066] In this first alternative embodiment of the machining unit 100, a second machining tool 121 can be provided, which is attached to the same tool holder 160 as the first machining tool 120, or to another tool holder (not shown), but is oriented in a direction perpendicular to the direction of the first machining tool. The second machining tool 121 can be used to machine ribs or grooves on at least one surface of the disk of the axial bearing 24 that forms part of the shaft 7. To accomplish this, the tool holder 160 is moved parallel to the shaft 7 as far as the disk of the axial bearing 24. Once positioned close to the disk, the second machining tool 121 is driven to machine ribs or grooves on at least one of the surfaces of the disk of the axial bearing 24.

[0067] It should be noted that for this first alternative embodiment of the machining unit, it is preferable to use the same tool holder for the two machining tools in order to avoid having a cantilevered portion that could lead to poor machining accuracy. With the same tool holder 160, there is no cumulative machining error from two tool holders with non-uniform settings.

[0068] In an alternative embodiment, the spindle 140 that rotatably holds the shaft 7 can be moved along the longitudinal machining direction to produce ribs or grooves. As already indicated, the shaft 7 is tubular, such that it can be attached and moved along the longitudinal direction. In the case where the shaft 7 is in tubular form, the two spindles 140 can have their ends partially inserted into the inner tube of the shaft at the two ends of the shaft to hold the shaft locked and rotate the shaft at a set rotational speed ω for machining. It goes without saying that during the machining operation, the two spindles 140 with the shaft 7 to be machined can be moved along the longitudinal direction.

[0069] In this alternative embodiment, the machining unit 100 further includes at least one tool holder 160, which is connected to the structure of the lathe 130. It goes without saying that the actual dimensions of the machining unit 100 are presented as being smaller than their dimensions in reality. The tool holder 160 carries the first machining tool 120, the machining head of which can come into contact with the shaft 7 to machine grooves or ribs and can move back and forth according to the programmation of the machining unit 100. At least the end of the head of the machining tool 120 can be made of diamond for machining ribs or grooves on the shaft 7 made of tungsten carbide or ceramic. This operation is carried out so that the shaft 7 and the first machining tool 120 rotate simultaneously and synchronously according to a sine program to obtain a defined arrangement of ribs or grooves on the workpiece portion of the shaft 7 for each front or rear air or gas radial bearing.

[0070] In an alternative embodiment, it is also possible to move the tool holder 160 and the first machining tool 120 jointly along the longitudinal machining direction instead of moving the shaft 7 for machining ribs or grooves on the shaft.

[0071] The frequency of the reciprocating movement of the first processing tool 120 can also be changed according to the programming of the processing unit 100. In particular, the reciprocating movement of the processing tool is synchronized by the sine programming implemented in the processing unit and the desired and programmed arrangement of the ribs or grooves to be produced on the part of the disc of the axial bearing 24 of the shaft 7 and / or the shaft 7.

[0072] It should be noted that the axial bearing 24 of the shaft 7 and the shaft 7 are made of the same material and are integrally formed. Therefore, the shaft 7 and the axial bearing 24 of the shaft can be produced simultaneously by a molding operation or preferably by using at least one processing tool of the tool holder of the processing unit 100, and the at least one processing tool is subsequently used to machine the grooves or ribs on the front and rear parts of the shaft 7. In this case, it is possible to use the first processing tool 120 of the tool holder 160. In addition, in order to produce the axial bearing 24 on the initial blank of the shaft 7, the initial blank of the shaft 7, which can already be in tubular form, can initially have a diameter substantially corresponding to the final outer diameter of the axial bearing 24 to be produced. The blank is attached to the two main shafts 140 of the processing unit 100 so that it can rotate about the longitudinal axis. The first processing tool 120 must be a grinding material harder than the material of the blank of the shaft 7. The first processing tool moves from the first end of the rotating shaft to the first position of the shaft 7, which corresponds to the position of the surface of the disc of the axial bearing 24 to be produced. This first processing operation involves the blank of the rotating shaft and the processing tool 120 in order to be able to remove the first thin layer of material from the blank of the shaft. Subsequently, the processing tool 120 removes a plurality of other successive thin layers from the rotating shaft by longitudinally displacing the first end to the first position of the axial bearing 24 until the desired shaft diameter is reached, and thus the axial bearing 24 is produced on the shaft 7. If the continuation of the shaft starts from the second position of the axial bearing at the opposite end of the shaft, the machining by removing thin layers must also be carried out on the other side of the blank of the shaft by the following steps: changing the direction of the tubular blank, attaching the blank of the shaft to the two main shafts 140 in the opposite direction and repeating these operations with the processing tool 120 on its tool holder 160 as before. This makes it easier to change the direction of the shaft blank between the main shafts 140 without having to move the tool holder 160 with the processing tool 120 from another position on the processing unit 100.

[0073] It goes without saying that once the shaft 7 has been produced to the desired diameter and the axial bearing 24 has been produced, ribs or grooves can be machined on the front and rear parts of the shaft by the first processing tool 120 connected to the tool holder 160.

[0074] Typically, the shaft 7 to be machined is made of tungsten carbide or ceramic. Therefore, the machining tool 120 typically includes a diamond machining head. This makes it possible to produce all the ribs or grooves together on the first workpiece portion at the first end of the shaft 7 from the start point of the first portion to the end point of the first portion by the displacement of the shaft 7 programmed according to the machining unit 100 in the longitudinal machining direction and the reciprocating movement of the machining tool 120, or also by the longitudinal displacement of the first tool holder 160 or the first tool 120 in the tool holder 160.

[0075] In this first embodiment of the machining unit 100, a second machining tool 121 must be provided which is mounted on the tool holder 160 in a direction perpendicular to the first machining tool 120 in order to produce ribs or grooves on one surface or on both surfaces of the disc of the axial bearing 24 by changing the direction of the shaft 7 attached to the two main spindles 140.

[0076] It should also be noted that the ribs or grooves can be machined successively on the first front portion and the second rear portion of the shaft by the first machining tool 120. According to the programming of the machining unit, when half of the first workpiece portion and half of the second workpiece portion of the shaft 7 have been passed, the orientation of the ribs or grooves can be changed in order to obtain V-shaped grooves over the length of the first and second machining portions, with the aim of generating air or gas pressure in the front radial bearing arranged on the first portion or in the rear radial bearing arranged on the second portion when the compressor operates with the shaft 7 rotating above the critical speed, so that there is no longer any mechanical contact with the one or more front and rear radial bearings.

[0077] In order to machine the axial bearing 24 in the form of a disc, only the second machining tool 121 is used, which can be mounted on a tool holder 160 capable of longitudinal displacement along the axis A-A. The ribs or grooves and their arrangement are programmed in the machining unit 100 to activate the second machining tool 121 in order to produce all the ribs or grooves together on the first surface of the disc by moving the machining tool or the rotating disc in a single machining direction from the outer circumference of the disc to the bottom of the annular region of the ribs or grooves or vice versa, and by the reciprocating movement of the machining tool 121 according to the programming of the machining unit 100. The two surfaces of the disc of the axial bearing 24 can be machined by the second machining tool by reversing the direction of the shaft 7 between the two main spindles 140.

[0078] On one or both surfaces of the disc of the axial bearing 24, ribs or grooves in the form of a helix can be made in the same orientation or in two different orientations on the two surfaces, with the aim of generating an air film via the grooves when the shaft 7 rotates in order to keep the axis in a longitudinally well-centered position during the operation of the centrifugal compressor.

[0079] It should also be noted that both the first processing tool 120 and the second processing tool 121 can move in the tool holder 160 in a first direction or in a second opposite direction to contact or move away from the workpiece portion of the shaft 7 for the first processing tool 120, as symbolically shown by the arrows in the tool holder 160 or in each of the processing tools 120, 121.

[0080] Figure 5 Partially taken from the processing unit 100 Figure 4 . However, in this figure, there is only one tool holder 160 and also only one processing tool 120, which can be oriented or rotatably moved about the axis 150 of the tool holder 160 so as to be in the indicated position (1) for machining ribs or grooves on the front and rear portions of the shaft 7, and in the indicated position (2) for machining ribs or grooves on one surface or preferably both surfaces of the disk of the axial bearing 24.

[0081] With Figure 4 the tool holder 160 shown in, the tool holder 160 can move longitudinally, for example, longitudinally on one or more guides arranged in the base 101 of the processing unit 100.

[0082] This second embodiment of the processing unit 100 seems easier to use than the first embodiment shown above in Figure 4 , but it is not necessarily faster for obtaining ribs or grooves on the portion of the shaft 7 and on the disk of the axial bearing 24. All the Figure 5 elements shown in are the same as the elements described with reference to Figure 4 and are therefore not repeated. The tool holder 160 can be equipped with more than two processing tools, but only one processing tool is in operation for machining ribs or grooves on one or two portions of the shaft 7 or on one surface or two surfaces of the disk of the axial bearing 24.

[0083] It goes without saying that the present utility model is not limited to the examples shown and various alternatives and modifications that would be obvious to those skilled in the art can be made to it. Other combinations with what is known in terms of centrifugal compressors are of course possible. It is possible to implement the rapid and precise machining of ribs or grooves on workpieces other than those described above using equivalent processing elements.

Claims

1. A centrifugal compressor (1), said centrifugal compressor having ribs or grooves machined on a workpiece shaft (7) intended to rotate about a longitudinal axis (A-A) and / or on an air or gas axial bearing (24) forming part of said workpiece shaft (7), a rotor structure (16) of an electric motor with at least one permanent magnet (16a) being intended to be mounted on or in said shaft (7) so as to rotatably drive said shaft, said centrifugal compressor (1) further comprising: A housing (2) having a fluid inlet (5) and a compressed fluid outlet (6); A first compressor impeller (8) and a second compressor impeller (10) intended to be mounted at two ends of the shaft (7) in the housing (2); a front air or gas radial bearing (18) intended to be mounted on the first end of the shaft (7); and / or a rear air or gas radial bearing (22) intended to be mounted on the second end of the shaft (7), Characterized in that all of said ribs or grooves (24a; 32) are obtained on the workpiece part of the disk of the rotatably driven shaft and / or said axial bearing (24) of the shaft (7).

2. The centrifugal compressor (1) according to claim 1, characterized in that, The second surface of the axial bearing (24) is intended to be produced from the opposite end of the shaft (7) in the second position of the axial bearing (24).

3. The centrifugal compressor (1) according to claim 1, wherein, The shaft (7) is made of tungsten carbide or ceramic so as to be machined by the head of a machining tool (120) made of diamond to produce all of the ribs or grooves (32).

4. The centrifugal compressor (1) according to claim 3, characterized in that, There is a change in the orientation of the ribs or grooves (32) between a first workpiece part at the first end of the shaft (7) and a second workpiece part at the second end of the shaft (7), and the ribs or grooves are produced as V-shaped grooves along the lengths of the first machining part and the second machining part.

5. The centrifugal compressor (1) according to claim 1, wherein, The workpiece is the air or gas axial bearing (24) in the form of a disk, the disk integrally forming part of the shaft (7), characterized in that the ribs or grooves (24a) and their arrangement are intended to be produced together on the first surface of the disk.

6. The centrifugal compressor (1) according to claim 5, characterized in that, All of the ribs or grooves (24a) are intended to be produced together on the second surface of the disk.

7. The centrifugal compressor (1) according to claim 6, characterized in that, All of said ribs or grooves (24a) are produced in a helical form having the same orientation or two different orientations on the two surfaces so as to generate an air film via the grooves when the shaft (7) is rotated to keep the axis in a longitudinally well-centered position during operation of the centrifugal compressor (1).

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