A method for machining and forming ribs or grooves for air or gas bearings in a workpiece equipped with a compressor's rotating shaft, and a method for assembling the components of the workpiece.

Abstract

To provide a method for machining ribs or grooves on a shaft in an air or gas radial bearing and on an air or gas axial bearing.SOLUTION: A workpiece rotates about a longitudinal axis of a centrifugal compressor. According to the invention, all of ribs or grooves (24a, 32) on a workpiece portion rotationally driven are obtained at one time with a machining tool by moving the workpiece or a tool holder in a longitudinal machining direction. The machining tool reciprocates from a start point to an end point of the workpiece portion so as to be in a machining position where the machining tool contacts with the workpiece and a position where the machining tool is not in contact with the workpiece. Reciprocating motion of the machining tool is synchronised with a sinusoidal program set in a machining unit, and a desired, programmed arrangement of the ribs or grooves to be formed on the workpiece portion.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for machining and forming ribs or grooves for an air or gas bearing of a workpiece provided with a rotating shaft of a high-speed centrifugal fluid compressor, and a method for assembling components of the workpiece. The compressor is a two-stage compressor, and includes a casing having an inlet for fluid and an outlet for compressed fluid, and surrounds a shaft rotatably mounted around a vertical axis (main shaft). A first compressor wheel and a second compressor wheel are attached back-to-back to the shaft, the first compressor wheel constitutes a first compression stage, and the second compressor wheel constitutes a second compression stage. The centrifugal compressor further includes a motor, preferably a synchronous electric motor, disposed between the first compressor wheel and the second compressor wheel and configured to rotate the shaft. At least one air or gas axial bearing is attached to one end of the shaft, a front radial air or gas bearing is attached to the first end of the shaft, and a rear radial air or gas bearing is attached to the second end of the shaft.

[0002] The present invention further relates to a workpiece obtained by a method for machining and / or assembling components of a workpiece.

Background Art

[0003] Fluid compressors are usually called turbo compressors or centrifugal compressors. These are composed of a stator and a rotor that form a permanent magnet synchronous motor (brushless motor). They may reach very high speeds such as 100,000 to 500,000 rpm. The motor drives the compressor wheel at high speed, and the compressor wheel compresses the fluid. The fluid can be air, gas, refrigerant, or other suitable fluids. By using two compressor wheels, the fluid is compressed twice.

[0004] These compressors can be used in mobile HVAC (heating, ventilation, and air conditioning) systems that use refrigerant gases, such as electric vehicles, hybrid vehicles, and hydrogen vehicles. They can also be used in stationary systems that use refrigerant gases, such as heat pumps.

[0005] These compressors typically include a first circuit for circulating the fluid to be compressed, and a second circuit for circulating a coolant used to cool the compressor, particularly the motor and the air or gas bearings supporting the motor shaft, and the electronic components. Cooling of the compressor components is necessary to prevent damage, especially since the motor heats up considerably when rotating at high speeds. These circuits are usually located inside the compressor itself, at least in terms of the cooling circuits. There are no regulations to facilitate the flow of cooling gas or air, particularly at high speeds, while the compressor is running, which presents a challenge. Furthermore, the air or gas bearings supporting the rotor shaft are not designed to support the rotor shaft without friction, resulting in significant heat generation when the rotor rotates at high speeds, which presents another challenge.

[0006] Furthermore, it is known that grooves or ribs are created in air or gas bearings due to the flow of air or gas, resulting in pressure and cooling. However, these grooves are created by laser processing without a specific arrangement, which presents the challenge of long processing times and high costs. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] One of the objectives of the present invention is to solve the various problems described above by providing a method for rapidly forming grooves or ribs on the rotor shaft of a workpiece in each air or gas radial bearing, and on air or gas axial bearings that are attached to the shaft and form part of the shaft. The grooves on the shaft are configured to overcome gravity when the compressor shaft rotates at high speed within each bearing, and to allow the rotating rotor shaft to be held in the radial bearing without mechanical contact with the air or gas flow, thereby preventing friction from occurring. [Means for solving the problem]

[0008] In view of the above circumstances, the present invention relates to a method for machining and forming ribs or grooves for air or gas bearings in a workpiece comprising a rotating shaft of a high-speed fluid compressor, having the features of independent claim 1.

[0009] Dependent claims 2 to 8 specify some particular steps of the method.

[0010] In view of the above circumstances, the present invention further relates to a method for machining and forming ribs or grooves on a workpiece having a rotating shaft, and a method for assembling components of a workpiece, as described in independent claims 9 and 10.

[0011] In view of the above circumstances, the present invention further relates to a workpiece intended to rotate around the longitudinal axis of a centrifugal compressor as described in independent claim 11, and intended to have ribs or grooves formed by being machined according to the machining method.

[0012] Dependent claims 12 to 15 describe some specific embodiments of the workpiece.

[0013] One advantage of the method of machining and forming ribs or grooves on a workpiece equipped with a compressor rotating shaft in a machining unit is that all ribs or grooves can be obtained in a single pass on the workpiece portion, which is rotationally driven by a reciprocating machining tool from the start to the end of the workpiece portion equipped with the rotating shaft. To achieve this, the reciprocating motion of the machining tool is synchronized with a sinusoidal program set in the machining unit and with the desired configuration of the ribs or grooves to be formed on the workpiece portion.

[0014] Therefore, thanks to the sinusoidal function, it becomes possible to achieve synchronization between the rotation of the spindle or shaft and the longitudinal motion of the workpiece or spindle. The frequency and amplitude of the sinusoidal function are selected according to the groove shape, the number of grooves, the rotational speed of the shaft, and the velocity of the longitudinal displacement.

[0015] Furthermore, during machining of a workpiece equipped with a rotating shaft, the workpiece or the tool holder supporting the machining tool is also displaced in the vertical machining direction as the machining tool reciprocates.

[0016] The reciprocating motion of this machining tool is compared to a piezoelectric oscillator that can increase or decrease the speed of the reciprocating motion of the machining tool by changing the vibration frequency according to how the machining unit is programmed, thereby obtaining the desired rib or groove. During this reciprocating motion, the machining tool may be in a machining position that is in contact with the workpiece, or at other times in a position that is not in contact with the workpiece.

[0017] The workpiece mainly comprises a shaft, which is mounted to a rotor structure of an electric motor that rotationally drives the shaft between a compressor vehicle and an air or gas radial bearing, or to at least one air or gas axial bearing attached to a first end of the shaft or forming part of the shaft. Ribs or grooves can be formed on one surface, or preferably both surfaces, of the disc of the air or gas axial bearing. Alternatively, ribs or grooves can be formed on one surface of a static axial bearing opposite the axial disc.

[0018] One advantage of this machining unit for forming ribs or grooves is that ribs or grooves can be formed very quickly and accurately on each workpiece portion of a shaft for an air or gas radial bearing in less than a minute. The same applies to grooves or ribs formed on one or both sides of a disc for a rotationally driven air or gas axial bearing. The machining tool is harder than the shaft or the material of the air or gas bearing.

[0019] As explained above, by programming the machining unit to rotate synchronously with the machining tool according to a sinusoidal program, ribs or grooves can be obtained on the shafts of each air or gas radial bearing and on each workpiece portion of the air or gas axial bearing.

[0020] Such ribs or grooves are preferably machined in a V-shape, where the orientation of each rib or groove changes at the center of each machined portion on the shaft. Thanks to this machining, a high-speed rotating shaft can be held within the air or gas radial bearings in the compressor without mechanical contact. Thus, the shaft is held within each radial bearing substantially frictionlessly by the pressure of the air or gas passing through the grooves or ribs as a result of the shaft's high-speed rotation. From a low rotational speed of 6000 rpm, the air or gas pressure in each aerodynamic radial bearing is configured such that the shaft does not mechanically contact the static radial bearing, thus avoiding any mechanical friction. Naturally, as the rotational speed of the shaft increases, the air pressure within the radial bearings increases, and the air or gas friction automatically increases.

[0021] The grooves or ribs are machined and formed by a machining unit and machining tools such that, according to a sinusoidal program or function and a desired configuration of the grooves or ribs, the orientation of the grooves or ribs on the shaft is reversed in the inner half of each static radial bearing substantially located on the ribs. This generates an air or gas pressure that can be made increasingly large as the rotation speed of the shaft increases.

[0022] Such high-speed centrifugal fluid compressors can rotate at very high speeds without excessive heating, thanks to the formation of ribs or grooves on the air or gas radial bearings.

[0023] Furthermore, an axial bearing is provided between the first compressor wheel and the first radial bearing. Helical grooves or ribs are formed on the circumferential surface of the front and rear surfaces of the disc of the axial bearing. As the shaft rotates, the grooves create a thin layer of air to hold the shaft in a well-centered position in the longitudinal direction.

[0024] By reading the following detailed description of an embodiment of the present invention while referring to the accompanying drawings, the objects, advantages, and features of the present invention can be more clearly understood. This description is given by way of example.

Brief Description of the Drawings

[0025] [Figure 1] The figure shows a longitudinal sectional view along the longitudinal axis A-A of a high-speed centrifugal compressor according to the present invention. [Figure 2] Figure 2a shows a longitudinal sectional view along the longitudinal axis A-A of a rotor structure according to the present invention, including a shaft with a compressor wheel, aerodynamic axial and radial bearings, and one or more permanent magnets. Figure 2b shows an orthographic projection view from the side of the first compressor wheel and axial bearing according to the present invention. [Figure 3] The figure shows a graph representing 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. [Figure 4] The figure is a three-dimensional view of the assembly of Figures 2a and 2b showing the grooves or ribs in each static radial bearing shown on the shaft according to the present invention. [Figure 5] The figure shows a first alternative embodiment of a longitudinal sectional view along the longitudinal axis A-A of a rotor structure according to the present invention, including a shaft with a compressor wheel, at least an axial bearing integral with the shaft, and one or more permanent magnets arranged inside the shaft. [Figure 6] The figure shows a second alternative embodiment of a longitudinal sectional view along the longitudinal axis A-A of a rotor structure according to the present invention, including a shaft with a compressor wheel, at least an axial bearing integral with the shaft, and one or more permanent magnets arranged inside the shaft. [Figure 7] An orthographic projection view of an air or gas axial bearing. [Figure 8]This is a longitudinal cross-sectional view of a rib or groove located at one end of a shaft on which a static radial bearing is arranged, according to the present invention. [Figure 9] This is a diagram of a shaft according to the present invention, in which grooves or ribs are arranged at two ends of the shaft, and static air or gas radial bearings are arranged on each end. [Figure 10] This diagram shows an outline of a processing unit for machining and forming grooves or ribs on the shaft of a centrifugal compressor according to the present invention. [Figure 11] This is a graph of precision ribs formed on a shaft for an air or gas radial bearing according to the present invention. [Figure 12] The diagram shows a three-dimensional overview of a processing unit for machining and forming grooves or ribs on the air or gas bearing of a centrifugal compressor, in accordance with the present invention. [Modes for carrying out the invention]

[0026] In this specification, all components that form part of a centrifugal compressor, which are well known in the prior art, are described only briefly. This is because the present invention essentially relates to a method of forming ribs or grooves on two parts of a shaft so as to be covered by two static air or gas radial bearings or air or gas axial bearings, respectively.

[0027] Figure 1 shows a cross-section of a high-speed centrifugal compressor 1 along the longitudinal axis AA. The centrifugal compressor 1 comprises a shaft 7 made of tungsten carbide or ceramics, mounted within a casing 2 so as to rotate around the longitudinal axis AA passing through the front 2b and rear 2c, and a first centrifugal compressor wheel 8 and a second centrifugal compressor wheel 10 mounted back-to-back at each end of the shaft 7, the first compressor wheel 8 constituting the first compression stage, and the second compressor wheel 10 constituting the second compression stage. In particular, in this embodiment, the shaft 7 is hollow and surrounds a threaded rod 11, with one of the compressor wheels 8 or 10 screwed into each end of the shaft 7, allowing for easy attachment and removal of the compressor wheels. Thus, the two compressor wheels 8 and 10 are driven on the same shaft 7, thereby improving energy efficiency and eliminating the need for a gearbox. At the rear of compressor vehicles 8 and 10 are labyrinth seals for controlling the pressure inside the compressor and balancing the axial force.

[0028] The casing 2 further encloses an electric motor, which is preferably a synchronous motor, positioned between the first compressor wheel 8 and the second compressor wheel 10, and configured 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. In particular, the stator 14 is formed by a coil 14a and two ferrite elements 14b, which are mounted to be fixed to the casing 2. The rotor structure 16 comprises one or more permanent magnets 16a integrated with the shaft 7, for example by joining, and is covered by a lining 16b. A flange 16c is attached to the side end of the lining (for example by joining) to ensure that the magnet can withstand centrifugal force at high speed.

[0029] Furthermore, a workpiece intended to rotate around the vertical axis AA of a centrifugal compressor comprises at least one shaft 7 and an air or gas axial bearing 24, and a rotor structure 16 comprising at least one permanent magnet 16a of an electric motor is mounted on or inside the shaft 7 to drive the shaft so that it rotates around the vertical axis AA, and the air or gas axial bearing 24 is attached to one end of the shaft 7 or forms part of the shaft 7. As shown in Figure 2a, the workpiece further comprises a first compressor wheel 8 and a second compressor wheel 10 attached to the two ends of the shaft 7, a front air or gas radial bearing 18 attached to the first end of the shaft 7, and a rear air or gas radial bearing 22 attached to the second end of the shaft 7.

[0030] As will be described below with reference to Figures 10 and 12, this machining method is performed in a machining unit 100 configured to receive a workpiece, in particular a shaft 7 having a bearing 24, the machining unit 100 comprising a tool holder 110 along with a tool for machining and forming a rib or groove in at least one portion of the shaft 7 of the workpiece.

[0031] The shaft 7 is mounted within the casing 2 so as to be able to rotate around its longitudinal axis AA using at least one front radial bearing 18, one rear radial bearing 22, and one axial bearing 24. The centrifugal compressor 1 includes a front radial bearing support 26 for supporting the front radial bearing 18 and a rear radial bearing support 28 for supporting the rear radial bearing 22, which are configured to be positioned around the shaft 7 at the front and rear of the motor, respectively. A volute 29 is provided at the rear between the rear radial bearing support 28 and the rear cover 3c. The volute 29 has an orifice that leads to a tangential fluid outlet 6 after compression. An axial bearing support 30 is provided between the first compressor wheel 8 and the front radial bearing support 26 to support the axial bearing 24, which is configured to be positioned around the shaft 7. It is clear that the axial bearing can be provided at the rear of the motor.

[0032] These bearings are non-contact, aerodynamic bearings designed to minimize friction. Such bearings require no lubrication and minimal maintenance. Referring particularly to Figures 2a, 2b, and 4, the axial bearing 24 is an aerodynamic bearing comprising a disc having a first groove 24a on at least one of its surfaces, which is preferably spiral-shaped over an annular region in the circumferential region and configured to generate a thin layer of air. Preferably, the axial bearing 24 has grooves or ribs 24a, preferably spiral-shaped, on the circumferential regions of the front and rear surfaces of the disc of the axial bearing 24, obtained by the machining process described below. The orientation of the grooves or ribs 24a can be different or the same on the front and rear surfaces. The axial bearing 24 with grooves or ribs 24a continues to center the rotating shaft 7 longitudinally by generating thin layers of air from the front and rear surfaces. The front radial bearing 18 and the rear radial bearing 22 are aerodynamic bearings, and the shaft 7 is configured to generate a thin layer of air or gas when the shaft 7 rotates within the air or gas radial bearings, and has a second groove or rib 32 facing the front radial bearing 18 and the rear radial bearing 22.

[0033] In Figures 2a, 2b, and 4, it can be seen that the first centrifugal compressor wheel 8 and the second centrifugal compressor wheel 10 are still mounted back-to-back at each end of the shaft 7. At the two ends of the shaft 7, one end has a first portion of the machined rib or groove 32, and the other end has a second portion of the machined rib or groove 32. A rotor structure 16, which includes at least one permanent magnet 16a, is fixed to the shaft at the center of the electric motor.

[0034] The rotor structure 16 may also have one or more diametrically magnetized permanent magnets 16a that are joined, contracted inside the shaft 7, or arranged in the lining 16b. The one or more permanent magnets 16a can be contracted within the lining 16b to have as much rigidity and interferometry as possible in order to compress each magnet and compensate for orthoracic pull caused by centrifugal force.

[0035] Furthermore, the rear lance between the shaft 7 and one or more magnets 16a mounted on the outside of the shaft 7 must be sufficient to prevent the magnets 16a from being clamped to the shaft 7 at high speeds and high temperatures. Such a condition would create a state of large biaxial tension inside the magnets 16a, and therefore increase the risk of the magnets 16a being damaged. In particular, the radial displacement of the inner surface of each magnet 16a can be made smaller than the radial displacement of the outer surface of the shaft 7 due to the negative thermal expansion coefficient of the magnets in the radial direction. This is shown by the shaded area in Figure 3, where, at the end of the rapid deceleration of the rotor structure 16 and while it is still hot, the inner surface of the magnets 16a approaches the outer surface of the shaft 7.

[0036] Figure 3 is a graph 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 present invention. x corresponds to the direction of the diameter magnetization of the magnet, and y corresponds to the orthogonal direction in which the magnet contracts radially during heating. When mounted by bonding, this difference corresponds to the radial deformation elastically accommodated by the adhesive between the shaft 7 and the permanent magnets 16a.

[0037] If the adhesive can withstand radial deformation under high temperature and high-speed tensile stress (up to 10 μm as shown in Figure 3), a bond can be formed between the shaft 7 and the magnet 16a. In this case, the adhesive will no longer be able to perform its load-bearing role and will become useless if it warps or its modulus of elasticity drops by several orders of magnitude at the operating temperature (e.g., 150°C).

[0038] In Figures 2a and 24, the flange 16c is attached to the side end of the lining 16b to ensure the mechanical integrity of the magnet 16a, or multiple magnets 16a arranged parallel to each other on the shaft 7, which are subjected to centrifugal force. The flange 16c can be joined or contracted between the shaft 7 and the lining 16b.

[0039] An adhesive-free assembly is achieved by optimizing the contraction fit (selection of materials and interference) of the flange 16c on the shaft 7, the flange 16c on the lining 16b, and the lining 16b on the magnet 16a. Thus, torque is transmitted from the magnet 16a or each magnet 16a to the shaft 7 via the flange 16c. The adhesive-free assembly ensures superior rigidity compared to adhesive-bonded assemblies, particularly at high speeds and high temperatures where the frequency of the first bending mode decreases dangerously toward the rotational frequency in assemblies made by adhesive bonding.

[0040] The lining 16b or casing can ideally be made of carbon fiber, or alternatively, of a titanium alloy or molybdenum alloy. The flange 16c can ideally be made of a titanium alloy, or alternatively, of non-magnetic steel. The diametrical interference of the flange 16c on the lining 16b is ideally the same as, or slightly less than, the diametrical interference of the lining 16b on one or more magnets 16a.

[0041] Furthermore, if the lining 16b and flange 16c are made of the same material, the lining 16b can be combined with at least one of the two flanges 16c to form a single part, especially for mounting the permanent magnet structure 16a to the outside of the shaft 7. Alternatively, the flange 16c can be replaced by a shoulder formed on the shaft 7 (a contraction fitting contact for the flange, for axial positioning of the magnet).

[0042] As will be explained below, particularly in Figure 10, grooves or ribs obtained by rotating the shaft can be formed on the shaft in a bare state; however, it is preferable to form these grooves or ribs after the assembly consisting of the lining 16b, permanent magnet 16a, and flange 16c is attached to the shaft 7. This ensures that there are optimal geometric tolerances for the two aerodynamic bearings 18 and 22 shown in the cross-section of Figure 2a.

[0043] Grooves or ribs obtained by laser ablation on the shaft can be formed before or after the assembly consisting of the lining 16b, permanent magnet 16a, and flange 16c is attached to the shaft 7, but it is preferable to form the grooves or ribs after the axial disk 24 has been placed on the shaft 7 and contracted when the magnet 16a is inside the shaft 7. In any case, it is necessary to obtain the final shape of the bearing (and optionally the assembly including the axial disk if assembled before finishing) before laser ablation.

[0044] The magnet 16a can be magnetized before being attached to the shaft 7, but it is preferable to magnetize the magnet 16a after the rotor structure 16 has been attached, measured, and balanced, in order to facilitate these processes.

[0045] Figure 5 shows a first alternative embodiment by a longitudinal cross-sectional view along longitudinal axis AA of a rotor structure 16 which is tubular and has one or more permanent magnets 16a disposed within the shaft 7, a shaft 7 having compressor wheels 8 and 10 according to the present invention, at least an axial bearing 24 integrated with the shaft 7, and one or more permanent magnets 16a disposed within the shaft 7. In this case, the one or more permanent magnets 16a are either contracted inside the shaft 7 or mounted with a small radial rear lance. The rear lance between the rod 11 and the one or more magnets 16a mounted inside the shaft 7 must be large enough to prevent the magnets 16a from being clamped to the rod 11 at high speed and high temperature. At high speed and high temperature, the inside of the magnets 16a will be under high biaxial tension, thus increasing the risk of breakage. The two ends 11b and 11d of the rod have threads so that the female thread 8b of the first compressor wheel 8 can be screwed onto the rod first, and then the female thread 10b of the second compressor wheel 10 can be screwed onto the rod. When there is radial play between the shaft 7 and the magnet 16a, the shoulder portion 11c is formed, fixing the magnet 16a and the threaded rod 11 in the axial direction after the compressor wheel 8 is screwed in. By tightening the compressor wheel 10, the threaded rod 11 and the shaft 7 are fixed to each other in the axial direction.

[0046] If the magnet 16a is located inside the shaft 7 and the material of the shaft 7 is too weak to allow for a contraction fit, the magnet 16a is fixed to the shaft 7 by a joint or by an axial clamp via a rod placed under tensile stress. Alternatively, an axial clamping force is generated in the solid magnet by directly machining and forming threads on the shaft, thereby screwing a wheel that holds the magnet onto the hollow shaft 7.

[0047] Therefore, the hollow magnet is slightly compressed axially between the shoulder of the rod 11b and the tubular end 8b of the wrench 8. Tightening the wrench 8 compensates for the difference in thermal expansion between the rod 11 and the magnet 16a. Tightening the wrench 10 compensates for the difference in thermal expansion between the rod 11 and the shaft 7, maintaining sufficient adhesion to transmit torque.

[0048] Figure 6 shows a second alternative longitudinal embodiment along the longitudinal axis AA for a rotor structure 16 comprising a shaft 7 on which compressor wheels 8 and 10 are located, at least an axial bearing 24 integrated with the shaft 7, and one or more permanent magnets 16a disposed within the hollow shaft 7. This alternative embodiment combines a joint and an axial clamp for assembling the substantially solid magnets 16a inside the shaft 7. To do this, rods 11b and 11d, threaded at one end and shouldered at the other, are joined at their smooth portions within the substantially solid magnets 16a and screwed into the wheels on the opposite side. As a result, the magnets receive an axial tensile force, allowing the wheels to preload the shaft 7 and transmit torque by adhesion.

[0049] Figure 7 shows one embodiment of an air or gas axial bearing 24. As shown in the orthographic projection in Figure 7, ribs or grooves 24a of a specific depth are formed in an annular region that starts from the periphery of the disk and extends toward the center of the disk. The ribs or grooves 24a and their configuration are programmed, in particular, in a machining unit, to operate the machining tool to form all the ribs or grooves in a single pass. That is, this is done, for example, by moving the tool holder or rotating disk in a single machining direction from the periphery of the disk to the bottom of the annular region of the ribs or grooves. For example, the groove portion is gradually formed by the reciprocating motion of the machining tool, synchronized with a machining unit that rotates the disk at a given speed according to a sinusoidal program or function, starting from the periphery of the disk on one side.

[0050] Combined with the controlled reciprocating motion of the cutting tool, the initiation of each groove 24a is achieved by the rotation of the disk and the reciprocating motion of the cutting tool. This is continuously repeated for the next groove or rib section, from the first groove section to the end or bottom of the annular region. In this method of forming different ribs or grooves 24a on the disk 24, the machining time per grooved surface of the disk is less than one minute, which is significantly shorter than previous machining techniques using laser beams.

[0051] Figure 8 shows a longitudinal cross-sectional view of the first portion of the rib or groove 32 formed at the first end of the shaft 7, illustrating how the first air or gas radial bearing 18 is in contact with the first portion of the rib or groove 32 formed by this machining method.

[0052] Similar to the formation of grooves or ribs on the axial disk described above, during the machining of these grooves or ribs 32, the shaft 7 is rotated around its longitudinal axis by the machining unit and moves along its longitudinal axis in the machining direction. The machining tool, positioned in the tool holder, reciprocates at a frequency corresponding to how the machining unit is programmed, on the opposite side of the first portion of the shaft being machined. Alternatively, instead of moving the shaft 7 longitudinally, the tool holder can be moved in the longitudinal machining direction. All ribs or grooves 32 are obtained in one pass each by the machining tool at the first workpiece portion at the first end of the rotationally driven shaft, and this machining tool reciprocates from the start to the end of the first workpiece portion of the shaft 7.

[0053] The machining unit rotates the shaft 7 synchronously with the machining tool according to a sinusoidal program to obtain a predetermined configuration of ribs or grooves 32 on the first workpiece portion of the shaft 7 for the front gas radial bearing 18. For example, all ribs or grooves 32 are machined and formed in a single pass from the start of the first workpiece portion of the shaft 7 to the end of the first portion of the first end of the shaft 7 in only one machining direction on the same side as the first end, significantly reducing machining time.

[0054] Therefore, it can be determined that the sinusoidal function actually achieves synchronization between the rotation of the shaft 7 and the longitudinal displacement of the workpiece or the shaft 7. The frequency and amplitude of the sinusoidal function are selected according to the shape of the groove 32, the number of grooves 32, the rotational speed of the shaft, and the velocity of the longitudinal displacement.

[0055] In the machining unit, a specific configuration of ribs or grooves 32 formed on a first portion of the first end of the shaft 7 is programmed. In one preferred embodiment, each rib or groove 32 is V-shaped, that is, its orientation changes essentially from the center of the first workpiece portion of the shaft 7. This ensures that the shaft, rotating at high speed in the compressor, is held without mechanical contact within the air or gas journal bearings. From a low rotational speed of 6000 rpm, the air or gas pressure in each aerodynamic radial bearing is such that the shaft does not mechanically contact the static journal bearings, thereby avoiding any mechanical friction.

[0056] Figure 9 shows a shaft 7 with machined ribs or grooves 32 in a first portion at the first end of the shaft 7 and a second portion at the second end of the shaft 7. These first and second portions are machined and formed in the same manner as described above with reference to Figure 6. V-shaped ribs or grooves 32 of the same configuration can be formed at both ends of the shaft 7.

[0057] To further illustrate Figure 1, the compressor 1 comprises an aluminum casing 2, the top surface 2a of the casing 2 being closed by an upper cover 3a, and the front surface 2b and rear surface 2c being closed by a front cover 3b and a rear cover 3c, respectively. The sides 2d of the casing are joined at their bases to form a bottom 2e with a U-shaped cross-section.

[0058] The upper cover 3a is located on the same side as the compressor's electronic components. Therefore, access to the electronic components mounted on the compressor is easy and is provided through the upper cover 3a. The front cover 3b and rear cover 3c are used to access the inside of the compressor (motor, rotor, bearings, etc.). A gasket is positioned between the top surface of the casing 2 and the upper cover 3a. This gasket protects the electronic components from dust and moisture.

[0059] The casing 2 has an inlet 5 for the fluid to be compressed, located on the front cover 3b, and a tangential outlet 6 for the fluid to be compressed, located on one of the sides of the casing 2.

[0060] In Figure 1, the casing 2 has an inner housing formed coaxially with respect to the longitudinal axis AA from end to end between the front surface 2b and the rear surface 2c of the casing 2. This inner housing receives the front radial bearing support 26 and the front radial bearing 18, and the motor and rotor structure 16 is attached to the shaft 7, the rear radial bearing support 28 and the rear radial bearing 22, the second compressor wheel 10, and the volute 29. On the front surface 2b side, the inner housing is closed by the front cover 3b, thereby integrating the first compressor wheel 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.

[0061] Advantageously, at least one orifice, for example, indicated by reference numeral 57a, is formed, configured to allow the fluid to be compressed to circulate within the channel and into the motor and between the stator 14 and the rotor structure 16; and at least one orifice, for example, indicated by reference numeral 57b, is formed, configured to allow the fluid to be compressed to cool the motor, exit the motor, and rejoin the channel.

[0062] Similarly, advantageously, at least one orifice, for example, indicated by reference numeral 59a in Figure 1, is formed, configured to allow the fluid to be compressed to circulate within the channel 54 and circulate near the axial bearing 24, the front radial bearing 18, and the rear radial bearing 22, and at least one orifice, for example, indicated by reference numeral 57b, is formed, configured to allow the fluid to be compressed to rejoin the channel 54 after the axial bearing 24, the front radial bearing 18, and the rear radial bearing 22 have been cooled.

[0063] Therefore, after the compressible fluid enters the first compression stage through the inlet 5, it passes through the compressor section located along the longitudinal axis between the first and second compression stages within the channel 54 and rejoins the second compression stage. As a result, the compressible fluid cools the motor and recovers heat lost by the motor before entering the second compression stage as it passes between the inner wall 52 and the motor's ferrite element 14b, thereby increasing efficiency. In addition, the orifices 57a, 57b, and 59a allow for slight deviations in the flow, so that the compressible fluid also circulates between the stator 14 and rotor structure 16 and within the bearings, cooling these elements and recovering heat loss from the motor and heat loss due to bearing friction.

[0064] The centrifugal compressor 1 is capable of reaching very high rotational speeds in the range of 100,000 rpm to 500,000 rpm. The centrifugal compressor 1 allows the fluid compressed in the first compression stage to substantially pass through the entire system, recovering waste heat, particularly from the motor, bearings, and electronic components, thereby increasing efficiency before entering the second compression stage (as the pressure of the fluid being compressed increases as its temperature rises). Furthermore, the compressor becomes very compact due to the use of only the fluid being compressed to cool the compressor without the use of additional cooling circuits, and the configuration of the electronic components in the compressor for electronic devices mounted in the casing. Thus, the compressor according to the present invention has a large rotational speed and a high compression ratio despite occupying only a small volume. For example, the compressor according to the present invention has a compression ratio greater than 3 and an output of the order of 4 kW, with dimensions on the order of 14 × 8 × 11 L × W × H (cm) and a weight of only 1.6 kg.

[0065] For example, the compressor according to the present invention can be used in conjunction with a fuel cell that obtains power from air or gas, or any other system that uses compressed air (such as an industrial compressor, a medical compressor, or a ship).

[0066] The compressor according to the present invention can be used together with a refrigerant gas in HVAC (heating, ventilation, and air conditioning) systems for mobile vehicles, such as those in electric, hybrid, or hydrogen-powered vehicles.

[0067] Furthermore, centrifugal compressors can also be used in stationary systems with refrigerant gases, such as heat pumps.

[0068] Centrifugal compressors can also be used with natural gas.

[0069] Figure 10 shows an overview of a machining unit 100 for forming ribs or grooves on the first and second ends of the shaft 7.

[0070] The machining unit 100 includes a lathe 130 having a spindle 140 for holding and rotating the shaft 7 when machining and forming a rib or groove. In one alternative embodiment, the spindle that rotates and holds the shaft can move in the longitudinal machining direction, as indicated by arrow Sm, to form the rib or groove.

[0071] The machining unit 100 further includes a tool holder 110 connected to the structure of the lathe 130. The tool holder 110 carries a machining tool 120, the machining head of which contacts the shaft to machine and form grooves or ribs and can reciprocate depending on how the machining unit is programmed. The machining head of the machining tool 120 can be made of diamond to machine and form ribs or grooves on a shaft 7 made of tungsten carbide or ceramics. This is done by synchronously rotating the shaft 7 with the machining tool according to a sinusoidal program to obtain a predetermined configuration of ribs or grooves on the workpiece portion of the shaft 7 for each front or rear air or gas journal bearing.

[0072] In one alternative embodiment, the tool holder 110 can be moved in the longitudinal machining direction, rather than the shaft 7, in order to machine and form ribs or grooves on the shaft.

[0073] Depending on how the machining unit 100 is programmed, the frequency of the tool's reciprocating motion can also be changed.

[0074] Figure 11 shows precision ribs or grooves for air or gas bearings, obtained by the reciprocating motion of a machining tool. This is determined by the material being machined, the rotational speed of the shaft for the machining operation, the shaft diameter, and many other parameters.

[0075] Finally, Figure 12 shows a machining unit 100 for forming ribs or grooves on one or two surfaces of the disc of the air or gas axial bearing 24. This machining unit 100 has the same elements as those described with reference to Figure 10 and will not be described again with reference to Figure 12. Only the configuration in which the tool holder 110 is connected to the structure of the lathe 130 needs to be noted.

[0076] Naturally, the present invention is not limited to the examples described, and various alternative forms and modifications are possible and can be made, which will be obvious to those skilled in the art. Naturally, other combinations known to be used with centrifugal compressors are also possible. For other workpieces not described above, ribs or grooves can be machined quickly and accurately using uniform machining elements. [Explanation of Symbols]

[0077] 1. Centrifugal compressor 2 Casing 5. Fluid inlet 6. Outlet of compressed fluid 7 shafts 8. First compressor vehicle 10. Second compressor vehicle 11 rods 11b, 11d End rods 16 Rotor Structure 16a Permanent Magnet 16b lining 16c flange 18, 22 Radial bearings 24 Axial bearings 24a, 32 Ribs or grooves 100 processing units 110 Tool Holder 120 Processing tools

Claims

1. A method for forming ribs or grooves on a workpiece intended to rotate around the vertical axis (A-A) of a centrifugal compressor (1), The aforementioned workpiece has a shaft (7), A rotor structure (16) of an electric motor, comprising at least one permanent magnet (16a), is mounted around or inside the shaft (7), and / or an air or gas axial bearing (24) is mounted at one end of the shaft (7) or forms part of the shaft (7), thereby driving the shaft (7) to rotate. The centrifugal compressor (1) further comprises a casing (2) having a fluid inlet (5) and a compressed fluid outlet (6), a first compressor wheel (8) and a second compressor wheel (10) of the workpiece attached to the two ends of the shaft (7) in the casing (2), a front air or gas radial bearing (18) attached to the first end of the shaft (7), and a rear air or gas radial bearing (22) attached to the second end of the shaft (7), The method is performed in a machining unit (100) which is configured to receive the workpiece and includes a tool holder (110) having a machining tool for machining and forming ribs or grooves on at least one portion of the workpiece. All of the ribs or grooves (24a, 32) on the machined portion of the rotatably driven shaft (7) are obtained by the machining tool and by a single displacement of the shaft (7) or the tool holder (110) of the workpiece in the longitudinal machining direction which is the longitudinal direction of the shaft (7). The machining tool reciprocates between a machining position that contacts the workpiece and a position that does not contact the workpiece, from the start to the end of the machining portion. The position of the machining tool in the reciprocating motion is controlled by the machining unit according to a sinusoidal function, and the frequency and amplitude of the sinusoidal function are selected according to the shape of the ribs or grooves (24a, 32), the number of the ribs or grooves (24a, 32), the rotational speed of the shaft (7), and the speed of the longitudinal displacement of the tool holder (110) or the shaft (7). All ribs or grooves (32) on the first machined portion at the first end of the shaft (7) are obtained from the start to the end of the first machined portion by the reciprocating motion of the machining tool during a single displacement of the rotating shaft (7) in the longitudinal machining direction. All ribs or grooves (32) on the second machined portion at the second end of the shaft (7) are obtained from the start to the end of the second machined portion by the reciprocating motion of the machining tool during a single displacement of the rotating shaft (7) or the tool holder (110) in the machining direction of the shaft (7) in the longitudinal direction, and the machined portion includes the first machined portion and the second machined portion. A method characterized by the following:

2. The workpiece comprises a shaft (7) made of tungsten carbide or ceramics. The head of the machining tool (120) is made of diamond in order to machine and form ribs or grooves on the first and second machining portions of the rotating shaft (7). The method according to feature 1.

3. During the machining of the rib or groove (32), at an intermediate point along the first machined portion of the first end of the shaft (7), the orientation of the rib or groove (32) changes, thereby obtaining a V-shaped groove over the length of the first machined portion. If the shaft (7) rotates beyond its limit speed during the operation of the centrifugal compressor, air or gas pressure is generated in the front air or gas radial bearing (18) located in the first machining portion to prevent the shaft (7) from mechanically contacting the front air or gas radial bearing (18). The method according to feature 2.

4. During the machining of the rib or groove (32), at an intermediate point along the second machined portion at the second end of the shaft (7), the orientation of the rib or groove (32) changes, thereby obtaining a V-shaped groove over the length of the second machined portion. If the shaft (7) rotates beyond its limit speed during the operation of the centrifugal compressor, air or gas pressure is generated in the rear air or gas radial bearing (22) located in the second machining portion to prevent the shaft (7) from mechanically contacting the rear air or gas radial bearing (22). The method according to feature 2.

5. The workpiece is equipped with an air or gas axial bearing (24) in the form of a disc. The formation of all ribs or grooves on the first surface of the disk is performed by controlling the machining unit (100) to move the machining tool or the rotating disk in a single machining direction, from the periphery of the disk to the end of an annular region extending toward the center of the disk, or vice versa, and by the reciprocating motion of the machining tool (120), wherein the first surface is a disc-shaped surface. The method according to feature 1.

6. By moving the machining tool or the rotating disk in a single machining direction from the periphery of the disk to the end of the annular region or vice versa, and by the reciprocating motion of the machining tool (120), all the ribs or grooves (24a) on the second surface of the disk are formed, wherein the second surface is the surface opposite to the first surface. The method according to specification 5.

7. All of the ribs or grooves (24a) on the first surface and all of the ribs or grooves (24a) on the second surface are formed to have the same orientation as a helical shape, or all of the ribs or grooves (24a) on the first surface and all of the ribs or grooves (24a) on the second surface are formed to have different orientations as helical shapes. When the shaft is rotated, a thin layer of air is generated through the groove, and the shaft is held in a vertically centered position during the operation of the centrifugal compressor (1). The method according to feature 6.

8. Before or after forming the ribs or grooves on the first and / or second processed portions of the shaft (7), all ribs or grooves (24a) on one or two surfaces of the disc are machined and formed. The method according to feature 7.

9. A method for forming ribs or grooves on a workpiece (7, 24) by the method described in claim 1, and assembling the components of the workpiece, The component comprises a shaft (7) to which the air or gas axial bearing (24), which is in the form of a disc attached to one end of the shaft (7), is attached. A rotor structure (16) comprising at least one permanent magnet (16a) of an electric motor is positioned or mounted on or within the shaft (7) between the first processed portion and the second processed portion of the shaft (7). All ribs or grooves (24a) on one or two surfaces of the disk are formed after the formation of the ribs or grooves on the first and / or second machined portion of the shaft (7), and before the arrangement or mounting of the rotor structure (16) which includes at least one permanent magnet (16a) around the shaft or within the shaft between the first and second machined portions formed from the shaft (7). A method characterized by the following:

10. A method for forming ribs or grooves on a workpiece (7, 24) by the method described in claim 1, and assembling the components of the workpiece, The component is a shaft (7) to which the air or gas axial bearing (24), which is in the form of a disc attached to one end of the shaft (7), is attached. A rotor structure (16) comprising at least one permanent magnet (16a) of an electric motor is positioned or mounted on or within the shaft (7) between the first processed portion and the second processed portion of the shaft (7). The rotor structure (16) of the electric motor, which comprises at least one permanent magnet (16a), is positioned or mounted between the first and second machined portions of the shaft (7) before the ribs or grooves are formed on the first and second machined portions of the shaft (7). After forming the ribs or grooves on the first and / or second processed portion of the shaft (7), all the ribs or grooves (24a) on one or two surfaces of the disc are machined and formed. A method characterized by the following:

Images