CH710120A1 - Spindle aerostatic and aerodynamic bearings. - Google Patents

Abstract

Ultra-high speed spindle with aerostatic and aerodynamic hybrid bearings (1), comprising at least two bearings (2, 3) and a rotary shaft (4) mounted in said bearings, the first bearing (2) being biconical, consisting of two half pads of adjacent frustoconical surfaces (10, 10 ') and a biconical shaft portion formed of two frustoconical portions (40, 50) and adjacent.

Description

Technical area

The present invention relates to aerodynamic and aerostatic bearing spindles without contact, ultra high rotation speed.

State of the art

[0002] There are mechanical drilling requirements of smaller and smaller diameters. This is particularly the case in the field of printed circuits, because of the miniaturization of substrates, or for the mass drilling of holes smaller than 100 micrometers in diameter. In theory, for optimal drilling, the rotational speed of the spindle should be about 800 ktpm (800,000 revolutions per minute). The advantages of a high speed of rotation are multiple, namely in particular: the increase of the productivity by the increase of the life of the tools and thus the reduction of the consumption of the number of tools per year, or also the reduction of costs.

To achieve these ultra-high speeds of rotation, the use of other bearing technologies than the usual ones is necessary.

The solution provided by the non-contact gas bearings makes it possible to have very little dissipation. However, the problem of instability remains under certain conditions and from certain speeds.

The solution provided by aerodynamic bearings with herringbone grooves used for several decades is one of the most successful and promising solutions for ultra-high speed spindles. Indeed, in recent years, applications in the field of energy, micro-energy (mini and micro-compressors of heat pumps, fuel cells, mini-gas turbines), and medical demonstrate interest of these bearings for small rotors designed to rotate at ultra-high speeds (up to 1.2 Mtpm). However complications related to geometry have been encountered.

A solution combining a cylindrical bearing and a conical bearing to take radial loads and axial loads, allows a compact configuration. However, the positioning and the kinematics of the rotor in the conical bearing depend strongly on the machining tolerances of the bearing. Machining is therefore more complex and more expensive.

For example, the documents FR 1 347 907 and FR 1 280 154 have bearings associating a radial bearing and a conical bearing. However, ball bearings seem incompatible with ultra high speeds. With these systems the problems of tree stability and dynamic stress are often encountered.

Brief summary of the invention

An object of the present invention is to provide a non-contact bearing pin associating at least two bearings having a hybrid aerodynamic and aerostatic operation free of known limitations.

According to the invention, these objects are achieved in particular by means of an aerostatic and aerodynamic hybrid ultra-high speed bearing pin, comprising at least two bearings and a rotary shaft mounted in said bearings, in which the first bearing is biconical, consisting of two half-pads of adjacent frustoconical surfaces and a biconical shaft portion formed of two frustoconical and adjacent portions.

This aerostatic and aerodynamic hybrid solution has the advantage of allowing the contactless starting of the spindle from a zero rotation speed, also giving the possibility of controlling the operating conditions by means of aerostatic pressurization.

Said adjacent half-pads reduce the effects of dissipation and adjust axially and radially the biconical bearing.

Said half-bearings of the biconical bearing delimit between them preferably at least one radial passage for the circulation of a gas. Advantageously this or these radial passages allow the evacuation of the gas flowing between the shaft and the two-half bearings of the biconical bearing.

The radial passage has an adjustable axial dimension by changing the distance between the two half-pads.

Preferably, each half-pad has at least one radial duct for the circulation of a gas. Advantageously this or these radial ducts allow the arrival of the pressurized gas from a source towards the space between the shaft and the two-half bearings of the biconical bearing.

The passage or said duct has a diameter of less than 200 micrometers, preferably less than 100 micrometers.

Preferably, each radial duct opens or opens on a smooth portion of the corresponding frustoconical portion. This arrangement ensures the proper operation of the aerostatic mode.

Each frustoconical portion of the biconical shaft portion is advantageously constituted by a smooth portion and a grooved portion. This solution has the advantage over the prior art to participate in the thermal stability and / or dynamic system.

The grooves of each grooved portion have a helical shape, or consist of lines, in particular of rectilinear, sinusoidal, corrugated lines. Preferably, each groove extends on a line forming a helical section on the surface of the grooved portion. Alternatively the grooves are on the surface of a portion of each half-pad.

The grooves occupy 20 to 80 percent of the length (the measurement along the x-axis of the shaft) of a frustoconical portion. This solution also has the advantage over the prior art of increasing rigidity and load capacity by optimizing the ratios of smooth and grooved surfaces.

In one embodiment, each frustoconical portion of the biconical shaft portion is advantageously constituted by a smooth portion, a grooved portion and a cylindrical smooth portion. The smooth cylindrical portion is disposed on the side of the large base.

The cylindrical smooth portion is very short in length and is between 0.1 and 1 mm, preferably 0.25 mm.

The grooved portions can be placed on either side of the cylindrical smooth parts.

Alternatively the smooth parts are placed on either side of the cylindrical smooth parts.

The shaft is made of a material from: titanium, aluminum or one of their alloys, steel, a ceramic, a composite material.

The invention also relates to a hybrid bearing pin further comprising a second bearing comprising: a pad, a radial shaft portion.

For this purpose, the radial shaft portion preferably comprises at least one smooth portion and / or at least one grooved portion.

In a preferred arrangement, the grooved portion of a radial shaft portion occupies 20 to 80 percent of the length of the radial portion of the shaft.

The second radial bearing preferably comprises at least one radial duct for the passage of a gas.

Advantageously, the radial duct of the radial bearing is on a smooth portion of the radial portion of the shaft.

According to a preferred arrangement, the flight height h is between 1 and 20 microns, preferably between 3 and 15 microns.

The hybrid bearings pin further comprises a pressurized air supply connected to the radial duct and whose pressure is adjustable during the aerostatic mode.

The air supply is able to feed the radial duct during the aerodynamic mode.

The invention also relates to a high-speed drilling machine comprising an aerostatic and aerodynamic hybrid bearing pin such as that described above in which the biconical bearing is disposed on the tool side or the opposite side.

Brief description of the figures

Examples of implementation of the invention are indicated in the description illustrated by the appended figures in which: <tb> Fig. 1 <SEP> illustrates a hybrid bearing pin associating a radial bearing and a biconical bearing. <tb> Fig. 2 <SEP> illustrates a close-up view of a frustoconical portion of the shaft of the landing spindle of FIG. 1 according to a variant. <tb> Fig. 3 <SEP> illustrates a close-up view of the radial portion of the shaft of the landing spindle of FIG. 1 according to a variant. <tb> Fig. 4 <SEP> illustrates an overview of a drilling system equipped with the spindle of FIG. 1.

Example (s) of embodiment of the invention

In this document, the term "axial" means any element considered in the direction of the length of the spindle shaft, namely along the X-X axis of FIG. 1, and by "radial" any element considered in a direction orthogonal to the shaft of the spindle bearing. In addition, the gap formed between the shaft and the bearing 20 or the half-bearings 11 and 11 determines the flight height h which corresponds to the difference (when the bearing spindle is in operation and at equilibrium). without load) between the inner radius of the bushing 20 or the half-bearings 11 and 11 and the corresponding outer radius of the shaft 4. Furthermore, by frustoconical portion is meant a truncated cone with its large base which extends axially possibly by a cylindrical part over a short distance less than or equal to 1 mm.

FIG. 1 illustrates a high-speed aerostatic and aerodynamic hybrid bearing pin 1 according to an embodiment associating a biconical bearing and a radial bearing 3.

In this fig. 1 is shown a rotary shaft 4 of axis X-X. The shaft 4 consists of five sections extending successively in an adjacent manner, namely: three portions with a smooth surface 30, 60 and 90 (the portions 30 and 90 represent the two end portions of the shaft 4 while the portion 60 represents the central portion of the shaft), a biconical portion P1 and a radial portion P2. For example, the central portion 60 is about 20 mm, while the shaft 4 is between 40 mm and 80 mm.

The radial portion P2 comprises a smooth portion 80 placed between two grooved portions 70 and 70 with grooves arranged in chevrons as illustrated in FIGS. 1 and 3. The two grooved parts 70 and 70 occupy 20 to 80% of the total length of the radial portion P2 of the shaft 4.

In an alternative embodiment, not shown, the position along the radial portion P2 of the smooth portion 80 and the grooved portions 70 and 70 may be reversed, namely with a radial portion P2 having a grooved portion located between two smooth parts.

The biconical shaft portion P1 comprises two adjacent frustoconical portions 40 and 50, the largest diameter of which is turned towards the other of the two frustoconical parts 40 and 50. The largest diameter of the portion of biconical tree P1 being in its central part.

Each frustoconical portion 40 (50) is provided with a grooved portion 42 (52), a smooth portion 41 (51) and another cylindrical smooth portion 43 (53) as illustrated in FIG. 1. On each frustoconical portion 40 (50), the grooves occupy from 20 to 80% of the length. In the case of FIG. 2, the cylindrical smooth portion 43 is reduced to zero axial dimension at the location of the large base of the frustoconical portion 40. The arrangement of the grooves on the two grooved portions 42 and 52 is such that a shape of rafters.

In FIG. 1, the two grooved portions 42 and 52 are placed on either side of the two cylindrical smooth parts 43 and 53. In an alternative embodiment partially shown in FIG. 2, the two grooved portions 42 and 52 are adjacent so that the tip of the rafters is disposed at the boundary between the two frustoconical portions 40 and 50.

In a particular embodiment, not shown, the position along each frustoconical portion 40 (50), the smooth portion 41 (51) and the grooved portion 42 (52) can be reversed. In this case for each frustoconical portion 40 (50), the smooth portion 41 (51) is located at the end of the frustoconical portion 50 (40) facing the other frustoconical portion. In this variant it is therefore the two smooth portions 41 and 51 which are adjacent or only separated by two cylindrical smooth parts 43 and 53 previously described.

In another embodiment, not shown, the grooves are only located on the inner surfaces s1, s1, s2 and s2 of the bearings 20 and / or half bearings 10 and 10 in an axial distribution and arrangement. similar to that described above for the grooved surfaces of the biconic portions P1 and radial P2 of the shaft 4.

In high-speed mode the grooves generate lift and rigidity, depending on the configurations, they also provide dynamic stability and / or promote the evacuation of heat produced in the gas film, while the smooth part increases the rigidity and load capacity of the system.

In one embodiment, the grooves may be oblique as shown in FIGS. 1, 2 and 3.

The biconical bearing 2 consists of two conical half-bushings 10 and 10 and the biconical shaft portion consists of two adjacent frustoconical portions 40 and 50.

The maximum diameter of the biconical shaft portion P1 is less than 40 mm, and is preferably between 7 and 12 mm, while the minimum diameter of the biconical shaft portion P1 is equivalent to the nominal diameter of the tree given further.

Each half-pad 10 and 10 is provided with at least one radial duct 11, 11 of about 100 micrometers in diameter, which allows the circulation of a gas such as air for example. This or these radial ducts open on the smooth part of the frustoconical portion 41, 41. Preferably these radial ducts 11, 11 are disposed on the same radial plane of each half-bearing pad 10 and 10, at least 4 in number, or at least 8 in number, and preferably at least 14 in number. , and advantageously to the number 15. Indeed, with a number of radial ducts 11, 11 greater than four, the circumferential distribution of the air pressure is improved, which is a significant advantage in aerostatic mode. As a variant (not shown), these radial ducts 11, 11 are pocket ducts in that they have a large widening of their diameter in their end portion facing the shaft 4. As an alternative to these radial ducts 11, 11, one can use a porous material to make each half-pad.

In aerostatic air enters the ducts 11, 11 of the biconical bearing 2 and 21 of the radial bearing 3 and flow to the lateral ends of said bearings. In aerodynamic air enters the conduit 12 of the biconical bearing 2 and flows to the lateral ends of said bearing. In aerodynamic air enters the lateral ends of the radial bearing 3 and leaves through the conduit 21 of said bearing.

The biconical bearing 2 is preferably placed on the demanding side more stability. For example in a drilling machine the biconical bearing 2 will be placed on the tool side but it can also be placed on the opposite side to the tool.

The radial bearing 3 consists of a radial bearing 20 and the radial shaft portion P1.

The pad 20 of the radial bearing is also provided with at least one duct 21 of about 100 micrometers in diameter which allows the circulation of a gas such as air for example. This radial duct opens on the smooth part of the radial portion 80. Preferably, this radial duct 21 is disposed on the same radial plane as the bearing 20. Preferably, these radial ducts 21 are at least 4 in number, or at least The number of radial ducts greater than four, in particular, has a circumferential distribution of the air pressure, which is a significant advantage in aerostatic mode. As a variant (not shown), this radial duct 21 is a pocket duct in that it has a large widening of its diameter in its end portion facing the shaft 4. As an alternative to this radial duct 21 a porous material can be used to make the pad.

Each conduit has a diameter of less than 200 micrometers, preferably 100 micrometers. These ducts serve to create pressure drop.

The shaft 4 is preferably hollowed by section over its entire length, which allows to lighten the bearing pin 1. Also preferably, the shaft 4 has a nominal diameter (portions 30, 60 and 90) less than 20 mm, preferably between 4 and 7 mm.

FIG. 4 illustrates a drilling system 100 integrating the bearing pin previously described in relation to FIGS. 1 to 3. The shaft 4 is represented with the air inlets 11, 11 and the air outlets (radial passage 12) communicating with the elements of the drilling system 100. The shaft 4 is equipped with a magnet rotor permanent 101 placed inside the shaft 4 as shown. This rotor 101 induces an electric field in the windings of the stator 108.

Two balancing zones are at the two end portions 30 and 90 of the shaft 4. The balancing is therefore left of FIG. 4, at the portion 30 of the shaft, by axial screws 103 with unbalance and right of FIG. 4, at the portion 90 of the shaft, by clamping screws 102. In this way, the dynamic balancing on the X-X axis of the shaft 4 is provided by adjusting the two ends of the shaft. tree 4.

The shaft 4 can be produced in different materials from: titanium, aluminum, one of their alloys, steel, a ceramic, or a composite material.

With reference to the drilling system of FIG. 4, the piezoelectric element 104, mounted on a disk structure which bears on the half-bearing pad 10, makes it possible to adjust the axial positioning of one of the half-pads 10 relative to the other half-pad 10 with a very high radial rigidity. This positioning can be fixed during operation of the spindle 1, by setting during startup, in aerostatic mode, or controlled by slaving according to the position deduced from the measurement of a position sensor, a sensor temperature, a speed sensor. Such a sensor may be capacitive, inductive or a laser sensor.

With this arrangement, or by any other arrangement, the radial passage 12 has an axial dimension d adjustable by changing the distance between the two half-pads 10, 10, which allows to change the flight height h of the biconical bearing.

Preferably, there is provided in the radial bearing 3 and / or the biconical bearing 2, a supply of pressurized air connected to said radial ducts 11, 11, 21. Optionally the pressure of this air supply is adjustable, in particular when the aerostatic mode dominates. Optionally this air supply is able to supply the radial ducts 11, 11, 21 of the radial bearing 3 and / or the double-sided bearing 2 during the aerodynamic mode because good results have been obtained with this configuration.

The air cooling system 107 is used for the stator. A water cooling system is optionally used for the exterior of the stator 108.

In an embodiment not shown, the bearings 20 or half-bearings 10 and 10 radial bearings 3 and 2 biconical can be mounted on flexible supports, elastic and dissipative typically elastomer O-rings (located between the bearing 20 of the radial bearing 3, the half-bushings 10 and 10 of the biconical bearing 2 and the elements connected to the body of the spindle) in order to allow the damping, dissipate the energy of the critical vibratory modes and increase the revolutions ranges operating the spindle.

The flight height h is between 1 and 20 microns, preferably between 3 to 15 microns. These preferred values concern the biconical bearing, or the radial bearing or both the biconical bearing and the radial bearing. This flight height h makes it possible to control the dynamics of the rotor 101, to widen the operating range range of the spindle, makes it possible to increase the axial and radial load capacity punctually.

At high speed, because of the centrifugal effect, the surfaces will be deformed. For this, the surfaces of the bearings can be machined so as to have specific shapes to compensate for this deformation. In this case, at rest, the radial bearing is not purely of cylindrical but concave shape and the frustoconical parts which have a concave shape generator.

Reference numbers used in the figures

[0066] <tb> 1 <SEP> Hybrid bearing spindle <tb> 2 <SEP> Biconical Bearing Portion <tb> 10 <SEP> Tapered right half bushing <tb> 10 <SEP> Tapered left half bushing <tb> 11 <SEP> Radial supply duct for the biconical bearing portion on the right side <tb> 11 <SEP> Radial feed pipe of the left-hand biconical bearing portion <tb> 12 <SEP> Pressure distribution duct <tb> S1, S1 <SEP> Internal surfaces of the two half-bearings of the biconical bearing <tb> 3 <SEP> Radial Bearing Portion <tb> 20 <SEP> Radial bearing bush <tb> 21 <SEP> Radial Bearing Bearing Feed Line <tb> S2 and S2 <SEP> Internal surfaces of radial bearing bushing <tb> h <SEP> Flight height <tb> 4 <SEP> Rotating shaft <tb> 80 <SEP> Smooth part of the radial part of the tree between 70 and 70 <tb> 70 <SEP> Part with grooves of the radial part of the right-hand shaft <tb> 70 <SEP> Grooved part of the grooved part of the radial part of the left-hand shaft <tb> X-X <SEP> The longitudinal axis of the tree <tb> P1 <SEP> Frustoconical portion of the tree 4 <tb> P2 <SEP> Radial portion of the tree 4 <tb> 50 <SEP> Frustoconical part of the left-hand shaft <tb> 51 <SEP> Grooves of the frustoconical part of the left-hand shaft <tb> 52 <SEP> Smooth part of the frustoconical part of the left-hand shaft <tb> 53 <SEP> Smooth and cylindrical part of the frustoconical part of the left-hand shaft <tb> 40 <SEP> Frustoconical part of the right-hand shaft <tb> 41 <SEP> Grooves of the frustoconical part of the right-hand shaft <tb> 42 <SEP> Smooth part of the frustoconical part of the right-hand shaft <tb> 43 <SEP> Smooth and cylindrical part of the frustoconical part of the right-hand shaft <tb> 30 <SEP> Smooth shaft portion located before the tapered portion 40 of the shaft <tb> 60 <SEP> Smooth portion between parts 50 and 70 of the tree <tb> 90 <SEP> Smooth portion after part 70 <tb> 100 <SEP> Drilling system. <Tb> 101 <September> Rotor <tb> 102 <SEP> Clamping screws <tb> 103 <SEP> Axial screw <tb> 104 <SEP> Piezoelectric actuator <tb> 107 <SEP> Air cooling system <Tb> 108 <September> Stator <tb> 109 <SEP> Air supply

Claims (23)

An ultra-high speed spindle with aerostatic and aerodynamic hybrid bearings (1), comprising at least two bearings (2, 3) and a rotary shaft (4) mounted in said bearings, the first bearing (2) being biconical consisting of two half-pads of adjacent frustoconical surfaces (10, 10) and a biconical shaft portion formed of two frustoconical portions (40, 50) and adjacent. 2. Spindle aerostatic and aerodynamic hybrid bearings (1), according to the preceding claim wherein said half-pads (10,10) delimit between them at least one radial passage (12) for the circulation of a gas. The hybrid bearing spindle according to claim 2, wherein said radial passage (12) has an adjustable axial dimension by changing the distance between the two half-bearings (10, 10). Aerostatic and aerodynamic hybrid bearing spindle (1), according to the preceding claims, wherein each half-bearing bushing (10, 10) has at least one radial duct (11, 11) allowing the circulation of a gas. 5. Spindle aerostatic and aerodynamic hybrid bearings (1), according to the preceding claim wherein said passage or said duct (11,11) has a diameter less than 200 micrometers, preferably less than 100 micrometers. 6. Spindle aerostatic and aerodynamic hybrid bearings (1), according to the preceding claim wherein each radial duct (11, 11) opens or opens on a smooth portion of the corresponding frustoconical portion (41, 41). An aerostatic and aerodynamic hybrid bearing spindle (1) according to any one of the preceding claims wherein each frustoconical portion (40, 50) of the biconical shaft portion 4 comprises only a smooth portion (41, 51) and a grooved portion (42, 52). Aerostatic and aerodynamic hybrid bearing spindle (1), according to any one of the preceding claims wherein said grooves of each grooved portion have a helical shape, or consist of straight, sinusoidal, corrugated lines. Aerostatic and aerodynamic hybrid bearing spindle (1) according to any one of the preceding claims, wherein the grooves occupy from 20 to 80 percent of the length of a frusto-conical portion. Aerostatic and aerodynamic hybrid bearing spindle (1) according to any one of claims 1 to 6 and 8 to 9, wherein each frustoconical portion (40, 50) of the biconical shaft portion comprises a smooth portion (41). 51), a grooved portion (42, 52) and a cylindrical smooth portion (43, 53), said cylindrical smooth portion being disposed on the side of the large base. 11. Spindle aerostatic and aerodynamic hybrid bearings (1), according to the preceding claim wherein said cylindrical smooth portion (43, 53) is axially between 0 and 1 mm, preferably 0.25 mm. Aerostatic and aerodynamic hybrid bearing spindle (1) according to any one of claims 10 to 11, wherein said grooved portions (42) and (52) are placed on either side of the cylindrical smooth parts (43). and (53). Aerostatic and aerodynamic hybrid bearing spindle (1) according to any one of claims 10 to 11, wherein said smooth portions (41) and (51) are placed on either side of the cylindrical smooth parts (43). and (53). Aerostatic and aerodynamic hybrid bearing spindle (1) according to any one of the preceding claims, in which the shaft is made of one of: titanium, aluminum or one of their alloys, steel, a ceramic, a composite material. Hybrid bearing spindle according to any one of claims 1 to 14, wherein the second bearing (3) consists of: a pad (20), a radial shaft portion. 16. Hybrid bearing pin according to the preceding claim, wherein the radial shaft portion comprises at least one smooth portion (80) and / or at least one grooved portion (70 and / or 70). 17. Spindle aerostatic and aerodynamic hybrid bearings (1), according to the preceding claim wherein the grooved portion of a radial shaft portion occupy 20 to 80% of the length of the radial portion of the shaft. Hybrid-bearing spindle according to any one of claims 15 to 17, wherein the second radial bearing (3) has at least one conduit (21) for the passage of a gas. 19. Spindle hybrid bearings according to the preceding claim, wherein said duct (21) of the radial bearing (3) opens on a smooth portion of the radial portion of the shaft. 20. Hybrid bearing pin according to any one of the preceding claims, wherein the flight height (h) is between 1 and 20 micrometers, preferably between 3 and 15 micrometers. The hybrid bearing spindle according to claim 4 or 14, further comprising an air supply (109) under pressure connected to said radial duct (11, 11, 21) and whose pressure is adjustable during the aerostatic mode. 22. Hybrid bearing pin according to the preceding claim, the air supply (109) is adapted to supply said radial duct (11, 11, 21) during the aerodynamic mode. A high speed drilling machine having an aerostatic and aerodynamic hybrid bearing spindle (1) according to any one of claims 1 to 21, wherein the biconical bearing (2) is disposed on the tool or opposite side.