Workpiece

Abstract

The utility model relates to a workpiece which comprises a shaft (7) and an air or gas axial bearing (24), and the air or gas axial bearing is attached to the shaft or forms a part of the shaft. The workpiece rotates about a longitudinal axis of the centrifugal compressor. According to the method, all the ribs or grooves (24a) are obtained at a time by moving the workpiece or the tool holder in the longitudinal machining direction on a part of the workpiece driven to rotate by means of a machining tool which is moved back and forth in a machining position in contact with the workpiece and in a position in which the workpiece is not in contact from the beginning to the end of the part of the workpiece. The reciprocating movement of the machining tool is synchronized with a sinusoidal program set in the machining unit and with a desired programmed arrangement of the ribs or grooves to be manufactured on the workpiece part.

Description

Technical Field

[0001] The utility model relates to a method for machining the ribs or grooves of the air or gas bearing of a workpiece including a rotating shaft of a high-speed centrifugal fluid compressor, and a method for assembling parts of the workpiece. The compressor is a two-stage compressor, and includes a housing having a fluid inlet and a compressed fluid outlet, and the housing surrounds a shaft rotatably mounted around a longitudinal axis. A first compressor impeller and a second compressor impeller are mounted back to back on the shaft, the first compressor impeller constitutes a first compression stage, and the second compressor impeller constitutes a second compression stage. The centrifugal compressor also includes a motor, preferably a synchronous electric motor, which 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 is mounted at one end of the shaft, a front radial air or gas bearing is mounted at the first end of the shaft, and a rear radial air or gas bearing is mounted at the second end of the shaft.

[0002] The utility model also relates to a workpiece obtained by a method for machining and / or assembling components of a workpiece. Background Art

[0003] Fluid compressors are often referred to as turbo compressors or centrifugal compressors. They include a stator and a rotor to form a permanent magnet synchronous motor (brushless motor). They can reach 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 this high speed. The fluid can be air, gas, refrigerant or any other suitable fluid. By using two compressor impellers, the fluid is compressed twice as much.

[0004] These compressors can be used, for example, in mobile HVAC (heating, ventilation and air conditioning) systems with refrigeration gas, such as electric, hybrid or hydrogen powered vehicles. These compressors can also be used in stationary systems with refrigerant gas, such as heat pumps.

[0005] These compressors generally include a first circuit for circulating the fluid to be compressed and a second circuit for circulating a cooling liquid, which is used to cool the compressor and, more specifically, the air or gas bearings supporting the motor shaft on the one hand and the electronic components on the other hand. More specifically, rotating the electric motor at high speeds causes it to heat up significantly, so much so that the compressor components need to be cooled to prevent damage to them. These circuits are generally arranged inside the compressor itself, at least with respect to the cooling circuit. During the operation of the compressor, particularly at high speeds, no provision is made to facilitate 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 without friction, which results in a large amount of heat being generated when the rotor rotates at high speeds, which constitutes another disadvantage.

[0006] Furthermore, it is known to make grooves or ribs on air or gas bearings for air or gas flow and to generate pressure and cooling. However, making the grooves by laser machining without any specific arrangement constitutes a disadvantage, since the machining time is too long and therefore its cost is too high. Utility Model Content

[0007] An object of the present invention is to overcome the various disadvantages mentioned above by means of a method for rapidly manufacturing grooves or ribs on the rotor shaft of a workpiece at each air or gas radial bearing and on an air or gas axial bearing attached to or forming part of the shaft. The grooves in the shaft are arranged in such a way that when the shaft of the compressor rotates at high speed in each bearing, the gravity is overcome and the rotating rotor shaft is allowed to be held on the air or gas flow in the radial bearing without mechanical contact and is therefore practically frictionless.

[0008] To this end, the utility model also relates to a workpiece, which is used to rotate around the longitudinal axis of the centrifugal compressor and is used to have ribs or grooves processed according to the processing method.

[0009] One advantage of the method for machining ribs or grooves on a workpiece comprising a rotating axis of a compressor in a machining unit is that all ribs or grooves are obtained at once on the workpiece portion driven in rotation by a machining tool that reciprocates from the beginning to the end of the workpiece portion comprising the rotating axis. To this end, the reciprocating movement of the machining tool is synchronized with a sinusoidal program provided in the machining unit and with the desired arrangement of the ribs or grooves to be produced on the workpiece portion.

[0010] The sine function thus makes it possible to synchronize the rotation of the spindle or shaft with the movement of the machining tool or spindle in the longitudinal direction. The frequency and amplitude of the sine function are selected as a function of the geometry of the grooves, the number of grooves, the rotation speed of the shaft and the speed of the longitudinal displacement.

[0011] During machining of a workpiece including a rotating axis, the workpiece or a tool holder carrying a machining tool also moves in the longitudinal machining direction while the machining tool performs a reciprocating motion.

[0012] The reciprocating motion of the tool is compared to a piezoelectric oscillator, where the oscillation frequency can be changed to speed up or slow down the reciprocating motion of the tool to obtain the desired rib or groove, depending on how the machining unit is programmed. During the reciprocating motion, the tool is in the machining position and is in contact with the workpiece at one time and not in contact with the workpiece at another time.

[0013] The workpiece mainly comprises a shaft or at least one air or gas axial bearing, the shaft being attached to the rotor structure of an electric motor driving the shaft in rotation, the air or gas axial bearing being mounted at a first end of the shaft or forming part of the shaft, between the compressor impeller and the air or gas radial bearing. Ribs or grooves may be made on one surface or preferably on both surfaces of the disc of the air or gas axial bearing. Alternatively, the ribs or grooves may be made on one surface of the static axial bearing facing the axial disc.

[0014] One advantage of the method for machining a rib or groove in a machining unit is that the rib or groove can be produced very quickly and with high precision in less than 1 minute per workpiece section of the shaft of an air or gas radial bearing. The same applies to grooves or ribs produced on one or both surfaces of a disk of a rotationally driven air or gas axial bearing. The machining tool is harder than the material of the shaft or the material of the air or gas axial bearing.

[0015] As described above, the machining unit can be programmed to rotate synchronously with the machining tool according to a sinusoidal program to obtain a rib or groove arrangement on each workpiece portion of the shaft for each air or gas radial bearing and a rib or groove arrangement for an air or gas axial bearing.

[0016] By such machining of ribs or grooves, preferably V-shaped, where the orientation of each rib or groove changes at the center of each machined portion on the shaft, a shaft rotating at high speed can be held in an air or gas radial bearing in a compressor without mechanical contact. Thus, the shaft is held in each radial bearing with virtually no friction by the pressure of the air or gas conveyed within the grooves or ribs due to the high speed rotation of the shaft. From as low as 6000rpm, the air pressure or gas pressure in each aerodynamic radial bearing is such that the shaft is no longer in mechanical contact with the static radial bearing, thereby avoiding any mechanical friction. It goes without saying that the faster the shaft rotates, the greater the air pressure in the radial bearing, which automatically creates more air or gas friction.

[0017] The grooves or ribs are machined by a machining unit and a machining tool according to a sinusoidal program or function and the desired arrangement of the grooves or ribs so as to reverse the orientation of the grooves or ribs on the shaft, which is essentially oriented toward the inner half of each static radial bearing arranged above the ribs. This generates an air or gas pressure that becomes increasingly greater the faster the shaft rotates.

[0018] This high speed centrifugal fluid compressor can rotate at very high speeds without overheating due to the ribs or grooves made in the air or gas radial bearing.

[0019] An axial bearing is also provided between the first compressor impeller and the first radial bearing. Grooves or ribs are made in the form of a spiral at the periphery on the front and rear surfaces of the disk of the axial bearing. An air film is generated through the grooves when the shaft rotates to keep the shaft in a well-centered position longitudinally. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The objects, advantages and features of the present invention will be better understood by reading the following detailed description of one embodiment of the present invention, one embodiment of which is given as a non-limiting example and is shown in the accompanying drawings, in which:

[0021] Figure 1 A longitudinal cross-sectional view along the axis AA of a high-speed centrifugal compressor according to the present invention is shown;

[0022] Figure 2a and 2b A longitudinal cross-sectional view along the axis AA of a shaft with a compressor impeller, aerodynamic axial and radial bearings and a rotor structure with one or more permanent magnets according to the invention, and a plan view from the side of a first compressor impeller and an axial bearing according to the invention are shown;

[0023] Figure 3 A graph showing the difference between the radial displacement of the outer surface of the shaft and the radial displacement of the inner surface of one or more permanent magnets according to the present invention;

[0024] Figure 4 According to the utility model Figure 2a and 2b a three-dimensional view of the assembly in FIG. 1 showing the grooves or ribs in each static radial bearing elevated above the shaft;

[0025] Figure 5 A first alternative embodiment of a longitudinal section of a shaft along the axis AA is shown, wherein the shaft has a compressor impeller, at least an axial bearing integral with the shaft and a rotor structure having one or more permanent magnets according to the invention, which are arranged inside the shaft;

[0026] Figure 6 A second alternative embodiment of a longitudinal section of a shaft along the axis AA is shown, wherein the shaft has a compressor impeller, at least an axial bearing integral with the shaft and a rotor structure having one or more permanent magnets according to the invention, which are arranged inside the shaft;

[0027] Figure 7 is a plan view of an air or gas axial bearing;

[0028] Figure 8is a view of a rib or groove provided at one end of a shaft on which a static radial bearing is provided according to the present invention, shown via a longitudinal section;

[0029] Fig. 9 is a view of a shaft according to the present invention, wherein grooves or ribs are provided at both ends of the shaft, and static air or gas radial bearings are respectively provided on the shaft;

[0030] Fig.10 is a schematic diagram of a machining unit for machining grooves or ribs on a shaft of a centrifugal compressor according to the utility model;

[0031] Fig.11 is a graph of precision ribs manufactured on a shaft for an air or gas radial bearing according to the present invention; and

[0032] Fig.12 The utility model is a three-dimensional schematic diagram of a machining unit for machining grooves or ribs on an air or gas axial bearing of a centrifugal compressor. DETAILED DESCRIPTION

[0033] In the present description, all components forming part of a centrifugal compressor which are known in the prior art are described only briefly herein, since the present invention is primarily concerned with the manner in which ribs or grooves are made on two parts of a shaft so as to be covered by two static air or gas radial bearings respectively, or with the manner in which ribs or grooves are made on an air or gas axial bearing.

[0034] Figure 1 A cross-sectional view of a high-speed centrifugal compressor 1 along the longitudinal axis AA is shown. The centrifugal compressor comprises a shaft 7 made of tungsten carbide or ceramic in a housing 2, the shaft being mounted so that it rotates around the longitudinal axis AA passing through the front surface 2b and the rear surface 2c, and a first centrifugal compressor impeller 8 and a second centrifugal compressor impeller 10 being 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 surrounds a threaded rod 11, and one of the compressor impellers 8, 10 is screwed to each end of the threaded rod, so that the compressor impeller can be easily installed and removed. Therefore, the two compressor impellers 8 and 10 are driven on the same shaft 7, which improves energy efficiency and avoids the need for a gearbox. The rear of the compressor impellers 8 and 10 includes a labyrinth seal to control the pressure in the compressor and balance the axial forces.

[0035] The housing 2 also encloses an electric motor, preferably a synchronous electric motor, which is positioned between the first compressor impeller 8 and the second compressor impeller 10 and is arranged to rotate the shaft 7. The motor comprises 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 specifically, the stator 14 is formed by a coil 14a and two ferrite elements 14b, which are mounted so that they are fixed relative to the housing 2. The rotor structure 16 comprises one or more permanent magnets 16a, which are made integrally with the shaft 7, for example by bonding, and are covered by a liner 16b. A flange 16c is attached (for example by bonding) to the lateral end of the liner and ensures that the magnets resist centrifugal forces at high speeds.

[0036] It should be noted that the workpiece intended to rotate about the longitudinal axis AA of the centrifugal compressor comprises at least one shaft 7 on or in which a rotor structure 16 having at least one permanent magnet 16a of an electric motor is mounted or attached so as to drive the shaft so that it rotates about the longitudinal axis AA, and an air or gas axial bearing 24, which is attached to one end of the shaft 7 or forms part of the shaft 7. The workpiece may also comprise a first compressor impeller 8 and a second compressor impeller 10 mounted at both ends of the shaft 7, a front air or gas radial bearing 18 mounted on the first end of the shaft 7, and a rear air or gas radial bearing 22 mounted on the second end of the shaft 7, as Figure 2a shown.

[0037] As referenced below Fig.10 and 12 As described, the machining method is performed in a machining unit 100 which is suitable for receiving a workpiece, in particular a shaft 7 with an axial bearing 24, and comprises a tool holder 110 with a tool for machining a rib or a groove on at least a portion of the shaft 7 of the workpiece.

[0038] The shaft 7 is mounted so that it can rotate about its longitudinal axis AA in the housing 2 by means of at least one front radial bearing 18, one rear radial bearing 22 and one axial bearing 24. The centrifugal compressor 1 comprises 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, which are arranged to be positioned around the shaft 7 at the front and rear of the motor, respectively. At the rear, a volute 29 is also provided between the rear radial bearing support 28 and the rear cover 3c. The volute 29 comprises a hole leading to the tangential fluid outlet 6 after compression. An axial bearing support 30 is also provided to carry the axial bearing 24, which is arranged to be positioned around the shaft 7 between the first compressor impeller 8 and the front radial bearing support 26. It is clear that the axial bearing can be provided at the rear of the motor.

[0039] The bearings are non-contact, aerodynamic type bearings so as to produce very little friction. They require no lubrication and require very little maintenance. More specifically, refer to Figure 2a , 2b and 4, the axial bearing 24 is an aerodynamic bearing and is constituted by a disk which includes a first groove 24a on at least one surface thereof, the first groove preferably being spirally shaped on an annular area at the periphery, arranged to generate an air film. Preferably, the axial bearing 24 preferably includes spiral grooves or ribs 24a at the periphery of the disk of the axial bearing 24 on the front and rear surfaces, the grooves or ribs being obtained by a machining process explained below. The orientation of the grooves or ribs 24a on the front surface may be different from that on the rear surface, or may be the same. The axial bearing 24 and its grooves or ribs 24a keep the rotating shaft 7 longitudinally centered by generating an air film from the front and rear surfaces. The front radial bearing 18 and the rear radial bearing 22 are aerodynamic bearings, and the shaft 7 has a second groove or rib 32 facing the front radial bearing 18 and the rear radial bearing 22, which is arranged to generate a film of air or gas when the shaft rotates in the air or gas radial bearing.

[0040] exist Figure 2a , 2b In Figures 4 and 5, it can still be seen that the first centrifugal compressor impeller 8 and the second centrifugal compressor impeller 10 are mounted back to back at each end of the shaft 7. At both ends of the shaft 7, there is a first portion of machined ribs or grooves 32, and at the other end there is a second portion of machined ribs or grooves 32. A rotor structure 16 with at least one permanent magnet 16a is fixed to the shaft in a central position for the electric motor.

[0041] It is also possible to have a rotor structure 16 comprising one or more diametrically magnetized permanent magnets 16a bonded, shrunk inside the shaft 7 or arranged in a liner 16b. The one or more permanent magnets 16a can be shrunk into the liner 16b with the greatest possible rigidity and interference to compress each magnet, thereby compensating for the radial orthogonal pull generated by the centrifugal force.

[0042] It should also be noted that the clearance between the shaft 7 and the one or more magnets 16a mounted on the outside of the shaft 7 must be sufficient to prevent any clamping of the magnets 16a against the shaft 7 at high speeds and temperatures, which would put the inside of the magnets 16a in a state of high biaxial tension and thus increase the risk of their breaking. More specifically, due to the negative thermal expansion coefficient of the magnets in the radial direction, the radial displacement of the inner surface of each magnet 16a can be smaller than the radial displacement of the outer surface of the shaft 7. This is due to Figure 3 The shaded area in is shown where the inner surface of the magnet 16a approaches the outer surface of the shaft 7 at the end of the rapid deceleration of the still hot rotor structure 16 .

[0043] Figure 3A graph is given showing the difference between the radial displacement of the outer surface of the shaft 7 and the radial displacement of the inner surface of one or more permanent magnets 16a according to the invention. x corresponds to the diametrical magnetization direction of the magnets and y corresponds to the orthogonal direction in which the magnets contract radially during heating. In the case of mounting by bonding, the difference corresponds to the radial deformation to be elastically accommodated by the adhesive between the shaft 7 and the permanent magnets 16a.

[0044] If the adhesive can withstand radial deformation under tensile stress at high temperature and high speed (in Figure 3 As seen in Figure 1, up to 10 μm), a bond can be formed between the shaft 7 and the magnet 16a. In this case, if the adhesive warps at operating temperatures (e.g. 150°C) or if its elastic modulus decreases by several orders of magnitude, the adhesive no longer fulfils its load-bearing role and thus becomes useless.

[0045] exist Figure 2a and 4 In the embodiment, flanges 16c are attached to the lateral ends of gaskets 16b in order to ensure the mechanical integrity of magnet 16a or magnets 16a arranged parallel side by side on shaft 7 and subjected to centrifugal forces. Flanges 16c may be bonded or shrunk between shaft 7 and gaskets 16b.

[0046] The adhesive-free assembly is achieved by optimizing the shrink fit (choice of materials and interference fit) of the flange 16c on the shaft 7, the flange 16c in the gasket 16b and the gasket 16b on the magnet 16a. The torque is thus transmitted from the or each magnet 16a via the flange 16c to the shaft 7. The adhesive-free assembly guarantees better rigidity than adhesive bonding, especially at high speeds and temperatures, where an assembly made by adhesive bonding would see the frequency of its first bending mode dangerously reduced towards the rotational frequency.

[0047] The liner 16b or housing may be ideally made of carbon fiber, and alternatively made of titanium or molybdenum alloy. The flange 16c is ideally made of a titanium alloy, and alternatively made of non-magnetic steel. The diametrical interference of the flange 16c in the liner 16b is ideally the same or slightly smaller than the diametrical interference of the liner 16b on the one or more magnets 16a.

[0048] It should also be noted that, if the liner 16b and the flange 16c are made of the same material, the liner 16b can be combined with at least one of the two flanges 16c to form a single component, in particular for mounting the permanent magnet arrangement 16a on the outside of the shaft 7. The flange 16c can also be replaced by a shoulder formed on the shaft 7 (shrink-fit banking of the flange, and axial positioning of the magnet).

[0049] As explained below, especially in Fig.10Although the grooves or ribs obtained by turning the shaft can be made on the shaft in the naked state, it is preferred to make the grooves or ribs after the assembly consisting of the liner 16b, the permanent magnet 16a and the flange 16c has been mounted on the shaft 7, in order to ensure Figure 2a The cross-sectional view shows the optimum geometric tolerances of the two aerodynamic bearings 18 and 22 .

[0050] Although the grooves or ribs obtained by laser ablation on the shaft can be made before or after the assembly consisting of liner 16b, permanent magnet 16a and flange 16c has been mounted on shaft 7, it is preferred that, if magnet 16a is inside shaft 7, these grooves or ribs are made after axial disc 24 has been shrunk onto shaft 7. In any case, it is essential that the final geometry of the bearing (and optionally of the assembly with the axial disc if assembled before finishing) is obtained before laser ablation.

[0051] Although the magnets 16a may be magnetized before they are mounted on the shaft 7, it is preferred to magnetize the magnets after the rotor structure 16 has been mounted, measured and balanced to facilitate these steps.

[0052] Figure 5 A first alternative embodiment is shown in a longitudinal section through a shaft 7 along the axis AA, the shaft having compressor wheels 8 and 10, at least an axial bearing 24 integral with the shaft 7 and a rotor structure 16 having one or more permanent magnets 16a arranged inside the shaft 7 according to the invention, the rotor structure being of tubular form. In this case, the one or more permanent magnets 16a are shrunk inside the shaft 7 or mounted with a small radial clearance. It should also be noted that the clearance between the rod 11 and the one or more magnets 16a mounted inside the shaft 7 must be sufficient to prevent the magnets 16a from being clamped against the rod 11 at high speeds and temperatures, which would put the interior of the magnets 16a in a state of high biaxial tension and thus increase the risk of their breaking. The rod has threads at its two ends 11b and 11d, so that the rod can first be screwed into the internal thread 8b of the first compressor impeller 8 and then into the internal thread 10b of the second compressor impeller 10. Shoulder 11c is provided in case there is radial play between shaft 7 and magnet 16a in order to axially fix magnet 16a and threaded rod 11 after compressor wheel 8 has been screwed on. By screwing on compressor wheel 10, threaded rod 11 and shaft 7 are axially fixed to each other.

[0053] When the magnet 16a is inside the shaft 7 and the material of the shaft 7 is too brittle to allow a shrink fit, the magnet 16a is fixed to the shaft 7 by bonding or by axial clamping via a rod placed under tensile stress. The axial clamping can also be produced on a solid magnet by machining a thread directly in the shaft in order to screw into the impeller holding the magnet in the hollow shaft 7.

[0054] The hollow magnet is thus slightly compressed axially between the shoulder of the rod 11b and the tubular end 8b of the impeller 8. Tightening the impeller 8 compensates for the thermal expansion mismatch between the rod 11 and the magnet 16a. Tightening the impeller 10 compensates for the thermal expansion mismatch between the rod 11 and the shaft 7 and maintains sufficient adhesion to transmit torque.

[0055] Figure 6 A second alternative embodiment is shown in a longitudinal section along the axis AA of a shaft 7 with compressor wheels 8 and 10, at least an axial bearing 24 integral with the shaft 7 and a rotor structure 16 with one or more permanent magnets 16a arranged inside the hollow shaft 7. This alternative embodiment combines bonding and axial clamping in order to assemble the almost solid magnet 16a inside the shaft 7. To this end, rods 11b and 11d, which have a thread only at one end and a shoulder at the other end, are bonded on their smooth part into the almost solid magnet 16a and screwed into the impeller on the other side. As a result, the magnets are subjected to axial traction to ensure that the impeller is preloaded on the shaft 7, allowing the torque to be transmitted by adhesion.

[0056] Figure 7 An embodiment of an air or gas axial bearing 24 is shown. Figure 7 As can be seen in the plan view of the disk, ribs or grooves 24a of a certain depth are made on an annular area starting from the periphery of the disk and leading to the center of the disk. The ribs or grooves 24a and their arrangement are programmed, in particular in a machining unit, to activate the machining tool so as to make all the ribs or grooves at once, i.e., by moving the tool holder or rotating disk in a single machining direction, for example from the periphery of the disk to the bottom of the annular area of ​​the ribs or grooves. For example, starting from the periphery on one surface of the disk, the groove portions are gradually formed by the reciprocating movement of the machining tool combined with synchronization with the machining unit, which rotates the disk at a given speed according to a sinusoidal program or function.

[0057] By means of this procedure and in combination with the controlled reciprocating motion of the machining tool, each start of all the grooves 24a is achieved by the rotation of the disc and the reciprocating motion of the machining tool. This is repeated continuously for the subsequent groove or rib portion, continuously from the first groove portion to the end or bottom of the annular area. By making different ribs or grooves 24a on the disc 24 in this way, the machining time for each grooved surface of the disc is less than one minute, which is significantly different from the previous machining technology using a laser beam.

[0058] Figure 8 A first portion of a rib or groove 32 produced on a first end of a shaft 7 is shown, wherein a first air or gas radial bearing 18 is shown via a longitudinal section on the first portion of the rib or groove 32 produced by the machining method.

[0059] During the machining of these grooves or ribs 32, the shaft 7 is rotated about its longitudinal axis by the machining unit and moved in the machining direction along its longitudinal axis, as described above for the production of grooves or ribs on the axial disk. The machining tool arranged in its tool holder reciprocates relative to the first part of the shaft to be machined at a frequency that depends on how the machining unit is programmed. It should be noted that instead of moving the shaft 7 in the longitudinal direction, the tool holder can be moved in the longitudinal machining direction. All ribs or grooves 32 are obtained at once by the machining tool on the first workpiece part of the first end of the shaft driven in rotation, which performs a reciprocating motion from the beginning to the end of the first workpiece part of the shaft 7.

[0060] The machining unit is programmed to rotate the shaft 7 synchronously with the machining tool simultaneously according to a sinusoidal program to obtain a determined arrangement of ribs or grooves 32 on a first workpiece portion of the shaft 7 for the front air or gas radial bearing 18. For example, starting from the first workpiece portion of the shaft 7 on the same side as its first end and in only one machining direction, and up to the end of the first portion of the first end of the shaft 7, all ribs or grooves 32 are machined at once, which significantly reduces the machining time.

[0061] It can therefore be determined that the sine function does achieve synchronization between the rotation of the shaft 7 and the displacement of the machining tool or the longitudinal direction of the shaft 7. The frequency and amplitude of the sine function are selected as a function of the geometry of the grooves 32, the number of grooves 32, the rotation speed of the shaft and the speed of the longitudinal displacement.

[0062] The specific arrangement of the ribs or grooves 32 made on the first part of the first end of the shaft 7 is programmed in the machining unit. In an ideal embodiment, the ribs or grooves 32 are each V-shaped, i.e. they include a change of orientation from the middle of the first workpiece portion of the shaft 7 in principle. This ensures that the shaft rotating at high speed in the compressor is held in the air or gas journal bearing without mechanical contact. From as low as 6000rpm, the air pressure or gas pressure in each aerodynamic radial bearing is such that the shaft is no longer in mechanical contact with the static journal bearing, thereby avoiding any mechanical friction.

[0063] Fig. 9 A shaft 7 is shown having a first portion including machined ribs or grooves 32 on a first end of the shaft, and a second portion on a second end of the shaft 7. The first and second portions are similar to those described above with reference to Figure 6 The same manner as described is processed. At both ends of the shaft 7, V-shaped ribs or grooves 32 of the same arrangement may be provided.

[0064] As Figure 1The compressor 1 includes a housing 2 made of aluminum, whose top surface 2a is closed by a top cover 3a, and whose front surface 2b and rear surface 2c are closed by a front cover 3b and a rear cover 3c, respectively. The side surfaces 2d of the housing are connected at their bases to form a bottom 2e having a U-shaped cross section.

[0065] The top cover 3a is located on the same side as the electronic components of the compressor. Therefore, easy access to the electronic components integrated in the compressor is provided by the top cover 3a. The front cover 3b and the rear cover 3c are used to reach the inside of the compressor (motor, rotor, bearings, etc.). A gasket is sandwiched between the top surface of the housing 2 and the top cover 3a. The gasket protects the electronic components from dust and moisture.

[0066] The housing 2 has an inlet 5 for the fluid to be compressed, provided on the front cover 3 b , and a tangential outlet 6 for the compressed fluid, provided on one side surface of the housing 2 .

[0067] exist Figure 1 In the embodiment, the housing 2 comprises an inner housing extending coaxially with the longitudinal axis AA from one end to the other between the front surface 2b and the rear surface 2c of the housing 2 and receiving 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 volute 29. On the front surface 2b side, the inner housing is closed by a 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 a rear cover 3c.

[0068] Furthermore, it is advantageous to provide at least one hole, for example the point indicated by reference numeral 57a, arranged to allow the fluid to be compressed to circulate within the channel to enter the motor and circulate between the stator 14 and the rotor structure 16; and to provide at least one hole, for example the point indicated by reference numeral 57b, arranged to allow the fluid to be compressed to leave the motor and rejoin the channel after cooling the motor.

[0069] Similarly, it is advantageous to provide at least one hole, e.g. Figure 1 The point given by the figure mark 59a is arranged to allow the fluid to be compressed to circulate in the channel 54 to circulate near the axial bearing 24, the front radial bearing 18 and the rear radial bearing 22; and at least one hole is provided, which corresponds to the same point given by the figure mark 57b, for example, and is arranged to allow the fluid to be compressed to rejoin the channel 54 after cooling the axial bearing 24, the front radial bearing 18 and the rear radial bearing 22.

[0070] Thus, after entering the first compression stage through the inlet 5, the fluid to be compressed passes in the channel 54 through the portion of the compressor situated along the longitudinal axis between the first and second compression stages, in order to rejoin the second compression stage. As a result, the fluid to be compressed, when it passes between the inner wall 52 and the ferrite element 14b of the motor, cools the ferrite element before entering the second compression stage and recovers the lost heat from the motor to increase its efficiency. Furthermore, the holes 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, in order to cool these elements and recover the heat losses from the motor and the heat losses due to friction in the bearings.

[0071] The centrifugal compressor 1 allows to reach very high rotational speeds, which are in the range of 100000 rpm to 500000 rpm. It allows the fluid compressed in the first compression stage to be passed substantially through the entire system to recover any waste heat, in particular 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, only the fluid to be compressed is used to cool the compressor, without resorting to an additional cooling circuit, and the arrangement of the electronic components in the compressor so that the electronics are integrated into the housing, which results in a very compact compressor. Therefore, the compressor according to the utility model has a high rotational speed and a high compression ratio, while occupying a small volume. For example, the compressor according to the utility model has a compression ratio greater than 3, and for a weight of only 1.6 kg, for dimensions in cm L×W×H (around 14×8×11), it has a power of around 4 kW.

[0072] For example, a compressor according to the present invention may be used with air or gas to power a fuel cell or any other system that uses compressed air (industrial compressors, medical compressors, ships, etc.).

[0073] With refrigerant gas, the compressor according to the invention can be used in mobile HVAC (heating, ventilation and air conditioning) systems, for example for electric, hybrid or hydrogen powered vehicles.

[0074] Centrifugal compressors can also be used in stationary systems with a refrigerant gas, such as heat pumps.

[0075] Centrifugal compressors can also be used with natural gas.

[0076] Fig.10 A schematic diagram of a machining unit 100 for producing ribs or grooves on parts of a first end and a second end of a shaft 7 is shown.

[0077] The machining unit 100 comprises a lathe 130 with a spindle 140 for holding the shaft 7 and rotating it when machining the ribs or grooves. According to an alternative embodiment, the spindle holding the shaft in rotation can be moved in the longitudinal machining direction to make the ribs or grooves as indicated by the arrow Sm.

[0078] The machining unit 100 also comprises a tool holder 110 connected to the structure of the lathe 130. The tool holder 110 carries a machining tool 120, whose machining head is in contact with the shaft to machine the grooves or ribs, said machining head being reciprocable according to how the machining unit is programmed. The head of the machining tool 120 may be made of diamond for machining ribs or grooves on the shaft 7 made of tungsten carbide or ceramic. This is performed so as to rotate the shaft 7 synchronously with the machining tool simultaneously according to a sinusoidal program to obtain a determined arrangement of ribs or grooves on the workpiece portion of the shaft 7 for each front or rear air or gas journal bearing.

[0079] In an alternative embodiment, instead of the shaft 7 , the tool holder 110 can also be moved in the longitudinal machining direction in order to machine ribs or grooves on the shaft.

[0080] The frequency of the tool's reciprocating motion may also vary depending on how the machining unit 100 is programmed.

[0081] Fig.11 The precision ribs or grooves for an air or gas bearing obtained by the reciprocating motion of the machining tool are shown, which are determined by the material to be machined, the rotational speed of the shaft used for the machining operation, the diameter of the shaft and many other parameters.

[0082] at last, Fig.12 A machining unit 100 is shown for making ribs or grooves on one or both surfaces of a disk of an air or gas axial bearing 24. The machining unit 100 comprises a Fig.10 The same elements as those described and referenced Fig.12 It will not be repeated. Only the manner in which the tool holder 110 is connected to the structure of the lathe 130 should be noted.

[0083] In one aspect of the utility model, a workpiece is disclosed, which is used for rotating around the longitudinal axis AA of a centrifugal compressor 1 and for machining ribs or grooves in a machining unit, the workpiece comprising at least one shaft 7, a rotor structure 16 having at least one permanent magnet 16a of an electric motor mounted or attached on or in the shaft to drive the shaft so as to rotate the shaft, and / or an air or gas axial bearing 24 mounted or attached on or in the shaft, the air or gas axial bearing being attached to one end of the shaft 7 or forming a part of the shaft 7, the centrifugal compressor 1 also comprising a casing 2 having a fluid inlet 5 and a compressed fluid outlet 6, a first compressor impeller 8 of the workpiece mounted at both ends of the shaft 7 in the casing 2 and a second compressor impeller 10 of the workpiece, a front air or gas radial bearing 18 mounted on the first end of the shaft 7, and a rear air or gas radial bearing 22 mounted on the second end of the shaft 7.

[0084] According to one aspect of the invention, the permanent magnet rotor structure 16 is arranged inside the shaft 7 in a tubular form, and the one or more permanent magnets 16a are contracted inside the shaft 7 and arranged on the rod 11 or attached to the two end rods 11b, 11d.

[0085] It goes without saying that the invention is not limited to the examples shown and that various substitutions and modifications that are clearly apparent to a person skilled in the art may be made thereto. Of course, other combinations known with centrifugal compressors are also possible. Rapid and precise machining of ribs or grooves may be performed on other workpieces than those described above using equivalent machining elements.

Claims

1. A workpiece for a rib or a groove which is rotated about the longitudinal axis (AA) of a centrifugal compressor (1) and machined in a machining unit, characterized in that The workpiece comprises at least one shaft (7), on or in which is mounted or attached a rotor structure (16) having at least one permanent magnet (16a) of an electric motor for driving the shaft so that the shaft rotates, and / or on or in which is mounted or attached an air or gas axial bearing (24), the air or gas axial bearing being attached to one end of the shaft (7) or forming part of the shaft (7), the centrifugal compressor (1) further comprising a housing (2) having a fluid inlet (5) and a compressed fluid outlet (6), a first compressor impeller (8) of the workpiece and a second compressor impeller (10) of the workpiece mounted in the housing (2) at both ends of the shaft (7), a front air or gas radial bearing (18) mounted on the first end of the shaft (7) and a rear air or gas radial bearing (22) mounted on the second end of the shaft (7).

2. The workpiece according to claim 1, characterized in that The rotor structure (16) is arranged on the outer surface of the shaft (7) between a first portion and a second portion of the shaft, wherein the first portion and the second portion are processed with ribs or grooves.

3. The workpiece according to claim 2, characterized in that The rotor structure (16) comprises one or more permanent magnets (16a) fixed to the shaft (7) and covered by a liner (16b), and two flanges (16c) or a flange (16c) and a shoulder on the shaft (7) are attached or provided at the lateral ends of the liner (16b) to allow the rotor structure (16) to withstand centrifugal forces at high speeds.

4. The workpiece according to claim 3, characterized in that The flange (16c) is bonded or shrunk between the shaft (7) and the gasket (16b).

5. The workpiece according to claim 1, characterized in that The permanent magnet rotor structure (16) is arranged in tubular form inside the shaft (7), and the one or more permanent magnets (16a) are contracted inside the shaft (7) and arranged on the rod (11) or attached to two end rods (11b, 11d).

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