FR2766027A1 - Synchronous magnetic coupling with cylindrical airgap - Google Patents

Abstract

A magnetic coupling consists of poles (3) which are arranged around the periphery of coaxial driving and driven rotors (1,2). The poles on both rotors are such that poles of different polarities are of different thicknesses and this produces an asymmetric torque over a displacement angle corresponding to a pole pair. The same asymmetrical variation in torque may also be obtained by numerous variations in geometrical configuration such as using poles which individually vary in thickness or which have tangential or axial lines of polarity or vary in the angle of the rotor periphery which they occupy.

Description

 The invention relates to a device for synchronous magnetic couplings with cylindrical air gap and permanent magnets.

 The basic principle is based on the fact that two magnetic poles of opposite nature attract each other and two poles of similar nature repel each other. Let us consider the case of a leading tree carrying a north pole which faces, through an air gap to a south pole located on a led tree. When the north pole moves in rotation, "the south pole wants to follow it", there is creation of a couple, and the driven shaft is driven. The number of poles is defined as the number of north and south poles present on one of the rotors.

This number is necessarily even, since the North Pole and the South Pole are paired. This number is the same on the driving rotor and on the driven rotor. All the art in the matter will relate to the way in which the poles are created, their number and the geometry of the device, and to the optimization of the value and the shape of the couple thus created.

 The magnetic couplings ensure the contactless connection between a driving shaft and a driven shaft. This contactless connection has many advantages and allows, among other things, the presence of a sealed wall between the two shafts, physically isolating them from one another.

 Such devices have applications in all industries, in particular nuclear, pharmaceutical, food, for pumping.

 These devices also make it possible to transmit movement while having a misalignment of the axes of the shafts, and also play a role of cardan. Depending on the form of the angular variations in the torque, they also make it possible to limit the transmitted torque (dropout phenomenon beyond a certain value).

 There are a number of configurations, which can be grouped into four types: cylindrical gap systems with cylinder head, flat gap systems with cylinder head, systems without cylinder head, systems without magnets on one of the parts.

 In cylindrical air gap systems with cylinder head, the rotors are cylindrical and concentric, separated by an air gap which is also cylindrical. The rotors are made up of magnets glued to a yoke of ferromagnetic material. The magnets are radially magnetized for the device and have alternating poles along the air gap. The cylinder head is a ferromagnetic cylinder outside the magnets for the outside rotor, and inside the magnets for the inside rotor. It is a classic arrangement which one meets with some variants. In the document "Application of rare earth magnets to coaxial couplings" by D. Weimann, H. J.

Wiesmann, K. Bachmann (paper No VI-l, Third International Workshop on Rare
Earth-Cobalt Permanent Magnets and their Applications, University of California, San
Diego, June 27-30, 1978), the magnets are radially magnetized rings with a number of poles depending on the application. A structure which is easier to carry out in practical terms replaces the magnet rings with non-joined magnetic tiles.

This is presented by the same authors in the cited reference and also by Y.

Tawara, M. Honshima, K. Shinbo, IT Oiwa in "Applications of precipitationhardened rare earth-cobalt magnets to torque coupling devices", paper No 11-4, Second
International Workshop on Rare Earth-Cobalt Permanent Magnets and their applications, June 8-11, 1976. We also find this structure with cylinder head and more or less parallelepiped magnets magnetized so that their magnetization is radial in the device in "Optimal design of synchronous torque couplers "from
RM Hornreich, S. Shtrikman, IEEE Trans. Mag., Vol. 14, No. 5, pp. 800-802, Sept.

1978, as well as in "Torque of a cylindrical magnetic coupling" by V. V. Fufaev, A.

Ya. Krasil'nikov, Elektrotekhnika, Vol. 65, No. 8, pp. 85-89, 1994, and also in "Synchronous couplings with SmCo5 magnets", W. Baran, M. Knorr, Paper No II-7,
Second International Workshop on Rare Earth-Cobalt Permanent Magnets and their
Applications, June 8-11, 1976.

 Depending on the application to which they are dedicated or the shape of the partition wall, the above devices have their equivalents for flat air gaps. The magnets always have alternating north and south poles in the air gap and their magnetization is axial with respect to the device. They are found presented by D. Weimann et.al., by W. Baran et al. The magnets are either annular with axial poles, or in the form of tiles or parallelepipeds. The yokes are discs of ferromagnetic material, on which are fixed the magnets which face each other through the plane air gap.

 In the communication "A new type of permanent magnet coupling" by J.P.

Yonnet, IEEE Trans., Mag., Vol. 17, No 6, pp. 2991-2993, Nov. 1981, are presented coupling structures without an iron cylinder head. The devices consist only of annular permanent magnets, with a driving ring and a driven ring, each carrying an alternation of north and south poles. We find the coaxial structures with a cylindrical air gap, and the facial structures with a flat air gap. In each case, the magnetizations can be radial or axial. Some structures combine several driving or driven rings.

 In the publication "A magnetic coupling without parasitic force for measuring devices" by J.P. Yonnet, J. Delamare, J. Appl. Phys. 76 (10), pp. 68656867, Nov. 1994, the authors present structures in which the magnet rings no longer carry an alternation of north and south poles, but have a magnetization whose direction changes gradually as one moves along the ring.

 All the devices presented above have magnets on the driving part and on the led part. The device presented by M. de Bennetot in an INIST publication, "Determination of the characteristics of a synchronous magnetic coupling with permanent magnets", consists of an external rotor carrying magnets fixed to a cylinder head and having a pole piece on their face on the side of the air gap, the inner rotor being only made up of an iron toothed wheel. The device uses the principle of variable reluctance machines.

In the articles "Magnetic couplings come of age", GM Giannini,
Mechanical engineering, pp. 54-56, Nov. 1982, and "Permanent magnet couplings", CJ

Fellows, CME, pp. 79-84, June 1979, the configurations cited above appear there, as well as a variant of the breech face device with plane air gap, in which the magnets, instead of being "cubes", are cylinders. The magnetization of these cylinders is axial with respect to the cylinder itself as well as to the coupling.

 In the case of couplings with a cylindrical air gap, the magnets have in known manner the shape of parallelepipedic blocks or tiles. These shapes require the machining of parts for two four of their faces.

 All modern magnets (ferrites, cobalt rare earths, neodymium boron iron) are sintered materials which are difficult to machine. These are very hard, abrasive and brittle materials, moreover their residual magnetization means that the chips remain stuck on the magnets and the machining tools. In addition, some of these magnets are highly oxidizable and can only be machined under inert gas.

 Magnetic couplings according to the state of the art transmit a torque which varies sinusoidally with the angle (3 of offset between the two shafts. The periodicity is equal to one revolution (2z radians) divided by the number p of pairs of poles (2z / p).

When the law of variation is not perfectly sinusoidal, the extreme values of torque are equal and of opposite signs and obtained for angles distant from a / p that is half a period, and the law of variation is symmetrical with respect to these extrema . The torque is always zero at equal distance from the two extrema.

 For the rest of the presentation, we note (3max the angle corresponding to the maximum positive torque, 0-max the angle corresponding to the maximum negative torque and O-o the angle corresponding to the zero torque.

According to the state of the art (fi) max- (H) -max) = z / p and (0-max- 0o) = nG / 2p
When the magnetic coupling is used as a torque limiter, for example in the case of screwing, exceeding the maximum torque induces a stall. The driven tree no longer follows the leading tree. The offset of the two shafts reaches and exceeds 0 but the transmitted torque decreases, cancels for E) o then becomes negative. I1 remains negative for half a period, z / p. If the training continues after the stall, there will be unscrewing on an angle 3C / p, until the torque becomes positive again. This is inconvenient, since the part which was to be screwed with a certain torque was unscrewed when said torque was reached. Normally the drive is stopped when the stall takes place, the angle of unscrewing depends on when the drive is stopped. In addition, due to the presence of dry friction, the unscrewing angle is not equal to that of screwing but it is less.

 The object of the invention is to propose a device for synchronous magnetic couplings with permanent magnets, which overcomes the drawbacks of the devices of the state of the art, which allows flawless screwing when the magnetic coupling is used as a torque limiter. , and which is more than easy to machine.

 The subject of the invention is a device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft, characterized in that the law of variation of the magnetic torque is asymmetrical, either because the value mean of the couple C over a period - is not zero either because the relation C (6) C (0 + NG / P) is not verified, whatever the angle 8.

 In a first embodiment of the invention, the magnets are in the form of tiles of constant thickness, two opposite faces of which are sections of cylinders coaxial with the shafts.

 In another embodiment of the invention the magnets are in the form of tiles of variable thickness, one face of which is a section of a cylinder coaxial with the shafts, opposite a flat inclined face, or in the form of truncated tiles.

 Tiles with variable thickness can be alternated with tiles with constant thickness.

 In another embodiment of the invention the magnets are cylindrical with axial magnetization.

 Each pole can consist of at least one magnet, driving and driven shaft having the same number of magnets, for a different number of magnets per pole.

 Each pole may also consist of at least one magnet, driving and driven shaft having a different number of magnets, for the same number of magnets per pole, or of at least one magnet, driving and driven shaft having a number different magnets, for a different number of magnets per pole.

 The magnetization directions are identical for all the poles of the two trees or different from one pole to another, and / or for the same pole, on a driven and / or leading shaft. At least one magnet has an axial or radial or tangential magnetization with respect to the air gap.

 The magnets can have different sizes from one pole to another, and / or for the same pole, on driven and / or driving shaft.

Other characteristics and advantages of the present invention will appear on reading the following description of a preferred embodiment, given by way of illustration and not limitation, and the appended figures among which
FIG. 1 represents a magnetic coupling device according to the invention with asymmetrical torque with magnets in the form of tiles of different thicknesses in attraction, the magnetization being radial;
FIG. 2 represents a magnetic coupling device according to the invention with asymmetrical torque with magnets in the form of tiles of different thicknesses in repulsion, the magnetization being radialc;
FIG. 3 represents an embodiment of the invention with magnets in the form of tiles of different widths and radial magnetization;
FIGS. 4 to 7 represent an embodiment of the invention with magnets in the form of tiles of variable thicknesses on shafts leading and driven in repulsion, the magnetization being radial;
FIGS. 8 to 11 bis show an embodiment of the invention with magnets in the form of tiles of variable thicknesses on shafts leading and driven in repulsion, the magnetization being radial;
FIG. 12 represents an embodiment of the invention with magnets in the form of tiles of different heights;
FIG. 13 represents an embodiment of the invention with magnets in the form of tiles of different lengths and tangential magnetization;
FIG. 14 represents an embodiment of the invention with magnets in the form of tiles of different widths and axial magnetization;
FIG. 15 represents an embodiment of the invention with cylindrical magnets with axial magnetization, and a number of north poles different from the number of south poles (2 north poles, 3 south poles);
FIG. 16 represents an embodiment of the invention with cylindrical magnets with axial magnetization, where the north poles have a section different from that of the south poles;
FIG. 17 represents an embodiment of the invention with cylindrical magnets, where the north poles have a height different from that of the south poles;
FIGS. 18 and 19 represent an embodiment of the invention with cylindrical magnets with axial magnetization, where the north poles are located on a circle with a diameter different from that on which the south poles are located;
FIGS. 20 and 21 show an embodiment of the invention with cylindrical magnets with axial magnetization, where the north poles and south poles are located on circles of variable diameter;
In the magnetic coupling device according to the invention, the shafts 1, 2 or driving and driven rotors are coaxial, one being inside, the other outside. The air gap between the two rotors is cylindrical.

 The ripple effect is due to the interaction of the upper and lower faces alternately north and south of the driving and driven shafts. The magnets on the driving rotor and on the driven rotor can be in attraction, a north pole facing a pole south or in repulsion, a north pole opposite a north pole.

 To avoid unscrewing when the maximum torque is reached, the torque variation law is asymmetrical according to the invention, either because the average value of the torque C over a period is not zero or because the relation C (0 ) = - C (6 + t / p) is not verified, whatever the angle O. On the one hand the maximum positive value can be greater than the absolute value of the maximum negative value the unscrewing torque is less than the tightening torque, and may possibly "disappear" in the area of dry friction; on the other hand, the angular zone during which the couple is positive can be greater than that for which the couple is negative; the variation may also present other asymmetries.

 FIG. 1 shows magnets 3 in the form of tiles of constant thickness or of paving stones, two opposite faces of which are sections of cylinders coaxial with the rotors; their thicknesses differ depending on the nature of the pole. The magnets on the driving rotor and on the driven rotor can be in attraction, a north pole facing a south pole, as in figure 1, or in repulsion, a north pole facing a north pole as in figure 2.

 This first embodiment corresponds to magnets, for which the magnetization of the tiles is radial with respect to the air gap, that is to say perpendicular to the axis of rotation.

 Figure 3 shows magnet tiles of different widths depending on the nature of the pole. The magnets on the driving rotor and on the driven rotor can be in attraction, a north pole facing a south pole or in repulsion, a north pole facing a north pole.

 Figure 4 presents magnet tiles of variable thicknesses, the direction of the variation depending on the nature of the pole. They can be described as tiles whose arc on the side of the air gap has been replaced by an inclined plane, so that the thickness varies.

 The magnets can be assembled by adjoining the thick sides of the tiles on the two rotors. The sides are therefore also in contact. When the magnets of the driving rotor have their thick part which faces the thin part of those of the driven rotor, the corresponding poles can be of opposite nature as in FIG. 4 or else of the same nature as in FIG. 5.

 The magnets can also be assembled by making a thick side adjoin a thin side, on the two rotors. Two magnets can face each other in two ways: the thick sides face each other (Figures 6 and 7) or a thick side faces a thin side (Figures 8 and 9). In each case a north pole of the driving rotor can face a north pole (figure 5) or a south pole (figure 4) of the driven rotor.

 The magnets can also be assembled by making a thick side adjoin with a thin side, on one of the two rotors (outer rotor in Figure 11) and by making the thick sides of the tiles adjoin on the other rotor (inner rotor on Figure 11). The magnets can also be assembled by bringing a thick side into contact with a thin side on the two rotors (Figure 10). The magnets facing each other by their thick side can then be in attraction (figure 10), a north pole facing a south pole, or else in repulsion (figure 11), a north pole facing a north pole.

 Figure 1 1 bis shows magnet tiles of variable thickness obtained by an inclined plane as before, but not over the entire angular width of the tile which appears truncated.

 All the tiles can be identical on a single rotor or both, but tiles with an inclined plane, truncated or not, can also be alternated with tiles of which two opposite faces are sections of cylinders coaxial with the rotors, on a single rotor or both.

 For all the configurations of tiles having an inclined plane, truncated or not, the widths can be equal or different on the driven and driving rotor, and the rotors can be in attraction or in repulsion.

 Figure 12 shows tiles of different heights depending on the nature of the poles. The high magnets on the driving rotor and on the driven rotor can be in attraction, a north pole facing a south pole, or in repulsion, a north pole facing a north pole.

 The magnetization of the tiles can also be tangential with respect to the air gap, while remaining perpendicular to the axis of rotation.

 Figure 13 shows tiles of different widths depending on the direction of the magnetization they carry. the magnets on the driving rotor and on the driven rotor can carry magnetizations of the same or opposite directions.

 The magnetization of the tiles can also be axial with respect to the air gap, that is to say parallel to the axis of rotation. Figure 14 shows tiles of different widths depending on the direction of the magnetization they carry. The magnets on the driving rotor and on the driven rotor can carry magnetizations of the same direction or of opposite directions.

 The driving and driven rotors can have different configurations, all combinations of magnets being possible.

 In another embodiment, the magnets are axial magnetization cylinders.

 The magnets do not require specific machining, the support parts of these magnets are simple to machine, and these are made of non-magnetic materials; these parts can be made with economical materials (plastics) or with materials with great mechanical qualities (titanium).

 Each pole consists of one or more magnets of the same polarity. Furthermore, the number of magnets constituting a north pole may be different from the number of magnets constituting a south pole. The number of magnets constituting a north pole (or a south pole) is not necessarily the same on the driving rotor and on the driven rotor. Figure 15 shows a pattern with two magnets per north pole and three magnets per south pole on the two rotors.

 The magnets are of different sections depending on the nature of the pole. The magnets on the driving rotor and on the driven rotor can carry magnetizations of the same direction, or of opposite directions, as indicated on figure 16.

 Figure 17 shows cylinders of different heights depending on the nature of the poles. The magnets on the driving rotor and on the driven rotor can carry magnetizations of the same direction, or of opposite directions.

 Magnets of different polarities can be located on circles of different diameters. Each pole may consist of one or more magnets arranged in the same direction. Figure 18 shows a configuration with two magnets per pole. The poles located on the inside diameter of each rotor can be of the same nature (Figure 18) or of a different nature (Figure 19).

 A pole can be made up of several magnets of the same polarity, each located on a circle of different diameter.

 When moving along the air gap in a counterclockwise direction, the south pole magnets can be located on circles of increasing radius, and the north pole magnets on circles of increasing radius.

 When moving along the air gap in a counterclockwise direction, the south pole magnets can be located on circles of increasing radius, and the north pole magnets on circles of decreasing radius.

 When moving along the air gap in a counterclockwise direction, the south pole magnets can be located on circles of decreasing radius, and the north pole magnets on circles of increasing radius.

 When moving along the air gap in a counterclockwise direction, the south pole magnets can be located on circles of decreasing radius, and the north pole magnets on circles of decreasing radius.

 One can have one of these structures on the driving rotor or on the driven rotor, all other combinations being possible.

 FIG. 21 illustrates the case where the south pole magnets are located on circles of decreasing radii, and the north pole magnets on circles of increasing radii, with three magnets per pole, on the two rotors. Figure 20 illustrates another possibility: the south pole magnets are located on circles of increasing radius, and the north pole magnets on circles of decreasing radius, on the outer rotor, with three magnets per pole, and on the inner rotor, the south pole magnets are located on circles of decreasing radius, and the north pole magnets on circles of increasing radius, with three magnets per pole.

 The number of magnets can be different depending on the nature of the pole and on which rotor this pole is located.

Claims (21)

 1.Device of synchronous magnetic couplings with cylindrical air gap in which the poles are with permanent magnets on driven and driving shaft, characterized in that the law of variation of the magnetic couple is asymmetrical., That is to say because the average value of the torque C on a period is not zero either because the relation C (6) = -C (O + t / p) is not verified, whatever the angle 0, p being the number of pairs of poles.  2.Synchronous magnetic coupling device in which the poles are with permanent magnets on a driven and driving shaft according to claim 1, characterized in that the magnets are in the form of tiles of constant thickness, two opposite faces of which are sections coaxial cylinders with the shafts.  3.Synchronous magnetic coupling device with cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 1, characterized in that the magnets are in the form of tiles of variable thickness, one face of which is a section of a cylinder coaxial with the trees, facing an inclined plane face, or in the form of truncated tiles.  4. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 1, characterized in that the magnets are cylindrical with axial magnetization.  5.Device of synchronous magnetic couplings with cylindrical air gap in which the poles are with permanent magnets on driven shaft and driving according to claim 2 or 3, characterized in that the tiles are of different thickness on driving shaft and / or driven shaft .  6. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on the driven and driving shaft according to claim 2 or 3 or 5, characterized in that the tiles are of different widths on the driving shaft and the driven shaft.  7. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 2, 3, 5 or 6, characterized in that the tiles are of variable thickness on the same shaft. leading or led, the thickest sides adjoining each tree.  8. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 2, 3, 5 or 6, characterized in that the tiles are of variable thickness on the same shaft. leading or leading, the thickest side next to the thinnest side on each tree.  9. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 2, 3, 5 or 6, characterized in that the tiles are of variable thickness on the same shaft. leading or leading, the thickest side adjoining the thinnest side on one tree and the thickest sides adjoining the other tree.  10. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 2, 3, 5 or 6, characterized in that tiles with variable thickness are alternated with tiles with constant thickness.  1 l. Device for synchronous couplings with cylindrical air gap in which the poles are with permanent magnets on driven and driving shaft according to one of claims 2, 3, 5 to 10, characterized. in that the tiles have different heights on the driven and / or leading shaft.  12. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to one of claims 2, 3, 5 to 11, characterized in that at least one magnet has a magnetization. axial with respect to the air gap.  13 A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to one of claims 2, 3, 5 to 11, characterized in that at least one magnet has radial magnetization. compared to the air gap.  14. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to one of claims 2, 3, 5 to 11, characterized in that at least one magnet has tangential magnetization. compared to the air gap.  15. Device for synchronous magnetic couplings with cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claims 12 to 14, characterized in that the orientations of the magnetizations are identical for all the poles of the two shafts.  16. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claims 12 to 14, characterized in that the orientations of the magnetizations are different from one pole to another, and / or for the same pole, on a driven and / or leading shaft.  17. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 4, characterized in that each pole consists of a magnet.  18. Device for synchronous magnetic couplings with cylindrical air gap in which the poles are with permanent magnets on driven and driving shaft according to claim 4, characterized in that each pole consists of at least two magnets, driving and driven shaft having the same number of magnets, for the same number of magnets per pole.  19. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 4, characterized in that each pole consists of at least one magnet, driving and driven shaft having the same number of magnets, for a different number of magnets per pole.  20. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 4, characterized in that each pole consists of at least one magnet, driving and driven shaft having a different number of magnets, for the same number of magnets per pole.  21. A device for synchronous magnetic couplings with a cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to claim 4, characterized in that each pole consists of at least one magnet, driving and driven shaft having a different number of magnets, for a different number of magnets per pole.  22.Synchronous magnetic coupling device with cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to one of claims 4, 17 to 21, characterized in that the magnets have sizes different from a pole to the other, and / or for the same pole, on a driven and / or leading shaft.  23.Synchronous magnetic coupling device with cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to one of claims 4, 17 to 22, characterized in that all the magnets of the same polarity are located on the same circle with a diameter different from that on which all the magnets of the opposite polarity are located, on a driven and / or driving shaft.  24.Synchronous magnetic coupling device with cylindrical air gap in which the poles are with permanent magnets on a driven and driving shaft according to one of claims 4, 17 to 22, characterized in that all the magnets of the same pole are located on circles of different diameters, on driven and / or leading shaft.