POSITIONING DEVICE OF MAGNETIC SUSPENSION TYPE

Abstract: A positioning device of magnetic suspension type is disclosed, which comprises a cylindrical stationary member (12) and a cylindrical floating member (14) arranged coaxial­ ly with the stationary member. The floating member (14) is supported in non-contact state with respect to the stationary member (12) by the magnetic forces produced by a plurality of magnetic circuits. The device further includes at least one control coil (42, 44) disposed such that it crosses the flux passing through the magnetic circuit. When the control coil is energized, it receives an electromagnetic force for displac­ ing the floating member in co-operation with the flux from the magnetic circuit.

Description: This invention relates to a positioning device for supporting an object by magnetic forces without contacting the object, and positioning the object by controlling the magnetic forces. A mechanical positioning device is known which can accurately position an object, using a ball screw. The ball screw is rotated, thus moving the base on which the object is mounted. The object is therefore positioned in accordance with the rotational angle of the ball screw. To accurately position the object the ball screw must be machined with high precision. However, because of this limitation in the precision of the screw, it is difficult to obtain highly accurate positioning of the object. Maintenance and inspection must be periodically made on the mechanical positioning device to maintain the positioning accuracy for years. It is improper to incorporate such a mechanical positioning device into an apparatus which cannot be inspected for a long time. A positioning device utilizing an electromagnet has been proposed to replace the mechanical positioning device. This new device has a base on which an object is mounted. The base is supported and moved in non-contact state by magnetic force generated by the electromagnet thus positioning the object. The magnetic force is controlled to position the object. The magnetic force is necessary for supporting the base at a predetermined position in inversely proportional to the square of the distance between the electromagnet and base. Therefore, in order to move the base, and, thus, the object, to a predetermined positon, the non-linear magnetic forces generated by the electromagnet must be linearized. In other words, it is necessary to convert a current supplied to the electromagnet into a non-linear current. Therefore, an electric circuit including not only the electromagnet, thus but also a device for such current conversion must be utilized. the use of such a complicated circuit inevitably reduces the reliability of the positioning device. US Patents Nos. 3 937 533 and 4 156 548 both disclose positioning devices utlilizing magnetic suspension. However, in both of these devices, the current is not proportional to the magnetic attractive/repulsive force so to is difficult to accurately adjust the position of the object. An object device of magnetic suspension type, which has a simple structure and can accurately position an object. To attain the above object of the invention, there is provided a positioning device of magnetic suspension, type comprising; a stationary member and a movable member facing said stationary member; characterized by means for generating a Lorentz's force which is directed from one of said members to the other member, including means, for generating a magnetic flux which is directed from one of said members to the other member; first conductive members, arranged perpendicular to the magnetic flux thereby causing said movable member to float vertically from said stationary member, in a state wherein said movable member is not in contact with said stationary member; and means for adjusting the magnitude of the Lorentz's force by adjusting the magnitude of the current in the said conductive members thereby adjusting the position of said movable member with respect to said stationary member, thus positioning said movable member relative to said stationary member. The movable member is supported with respect to the stationary member in non-contact state. The electromagnetic force for displacing the movable member can be produced by the interaction between the current supplied to the conductive member and flux of the magnetic circuit independently of the magnetic forces of magnetic support means. Further, since the magnitude of the electromagnetic force is proportional to the magnitude of the current supplied to the conductive member, the movable member can readily be positioned with respect to the stationary member by controlling the magnitude of the current. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is an exploded perspective view showing a first embodiment of the positioning device according to the invention; Fig. 2 is a sectional view taken along line II-II in Fig. 3; Fig. 3 is a sectional view taken along line III-III in Fig. 2; Fig. 4 is a view taken in the direction of arrow IV in Fig. 3; Figs. 5 to 7 illustrate the operation of the positioning device shown in Fig. 1; Fig. 8 is a sectional view taken along line VIII-VIII shown in Fig. 9 showing a second embodiment of the positioning device according to the invention; Fig. 9 is a sectional view taken along line IX-IX in Fig. 8; Fig. 10 is a sectional view showing a third embodiment of the positioning device according to the invention; and Fig. 11 is an exploded perspective view showing a fourth embodiment of the positioning device according to the invention. Referring to Figs. 1 to 3, there are shown a first embodiment of the positioning device according to the invention. The illustrated positioning device comprises a stationary member 12, a floating member 14 and position control means 16 for positioning a floating member 14. The stationary member 12 made from of a non-magnetic material has a hollow outer cylinder 18, an inner hollow cylinder 20 coaxial with the outer cylinder 18, an annular end wall 22 coupling together the lower ends of the inner and outer cylinders 20 and 18 and an end wall 24 closing the upper end of the inner cylinder 20. The floating member 14 is made from a silicon steel having a high magnetic permeability and serving as an electromagnetic shield. The floating member 14 has a hollow outer cylinder 26, a hollow inner cylinder 28 coaxial with the outer cylinder 26 and an end wall 30 closing the upper ends of the inner and outer cylinders 28 and 30. The outer cylinder 26 of the floating member 14 has an inner diameter greater than the outer diameter of the outer cylinder 18 of the stationary member 12. The inner cylinder 28 of the floating member 14 has outer and inner diameters such that it can be inserted in an annular space defined between the outer and inner cylinders 18 and 20 of the stationary member 12. The floating member 14 can be fitted on the stationary member 12 in non-contact state thereto, as shown in Figs. 2 and 3. A mounting flange 32 is secured by means of a shaft to the end wall 30 of the floating member 14. An object (not shown) to be positioned is mounted on the mounting flange 32. The mounting flange 32 is shown only in Figs. 1 and 2. The position control means 16 comprises of magnetic force generating means 16a and driving means 16b. The generating means 16a includes a plurality of permanent magnets as flux generation elements. More particularly, the generating means 16a includes four, arcular permanent magnets 34a to 34d provided at a uniform circumferential spacing on an upper portion of the outer periphery of the inner cylinder 28 of the floating member 14. The means 16a further includes other four arcular permanent magnets 36a to 36d provided at a uniform circumferential spacing on a lower portion of the outer periphery of the inner cylinder 28 such that they correspond to the respective permanent magnets 34a to 34d with respect to circumferential positions. The permanent magnets 34a to 34d are magnetized in the opposite direction to the permanent magnets 36a to 36d. The driving means 16b will now be described. The inner periphery of the outer cylinder 18 of the stationary member 12 has upper and lower annular grooves 38 and 40 formed in the circumferential direction. The center-to-center distance between the grooves 38 and 40 is equal to the center-to-center distance between the permanent magnets 34a to 34d and permanent magnets 36a to 36d. Axial direction control coils 42 and 44 which are wound in the circumferential direction are accommodated in the grooves 38 and 40. The outer periphery of the outer cylinder 18 of the stationary member 12 has eight upper projections 46a to 46h and eight lower projections 48a to 48h, these projections being spaced apart in the circumferential direction. These projections 46a to 46h and 48a to 48h are disposed at positions such that they correspond to circumferential ends of the permanent magnets 34a to 34d and 36a to 36d when the stationary member 12 is fitted on the floating member 14. In the Figures, the projections 48b and 48h are shown only partly. Among the projections 46a to 46h and 48a to 48h, the projections 46a, 46c, 46e, 46g, 48a, 48c, 48e and 48g are provided with radial direction control coils 50a to 50h. The remaining projections 46b, 46d, 46f, 46h, 48b, 48d, 48f and 48h are provided with circumferential direction control coils 52a to 52h. The positional relationship among the axial direction control coils 42 and 44, radial direction control coils 50a to 50h, circumferential direction control coils 52a to 52h and permanent magnets 34a to 34d and 36a to 36h when the floating member 14 is fitted on the stationary member 12 is as shown in Fig. 4. Fig. 4 represents the positional relationship among the axial direction controls 42, radial direction control coil 50a, circumferential direction control coil 52a and permanent magnet 34a. As is obvious from Fig. 4, the magnetic flux generated from the permanent magnet 34a penetrates the axial direction control coils 42 and penetrates portions of the radial direction control coil 50a and circumferential direction control coil 52a which are adjacent to each other and extend in the axial direction. Now, position detection means 53 for detecting the position of the floating member 14 relative to the stationary member 12 will be described. Two pairs radial position detectors 54a, 54b and 56a, 56b are respectively provided on upper and lower portions of the outer periphery of the inner cylinder 20 of the stationary member 12 such that the pair position detectors circumferentially spaced apart by 90°. Each radial position detectors 54a, 54b, 56a, 56b consists an eddy current type distance sensor and can measure the distance of the floating member 14 up to the inner periphery of the inner cylinder 28. Circumferential position detectors 58a and 58b are mounted on the outer periphery of the inner cylinder 20 of the stationary member 12 at the center position of a region defined by the radial position detectors 54a, 54b, 56a, 56b and at a diametrically opposite position to this position, respectively. The inner cylinder 28 of the floating member 14 has axially extending windows 60a and 60b which are located at positions corresponding to the circumferential position detectors 58a and 58b when the floating member 14 is fitted on the stationary member 12. Each circumferential position detector 58a and 58b consists an eddy current type sensor like the radial position detectors 54a, 54a, 56a and 56b. These circumferential position detectors 58a and 58b detect the circumferential position of the floating member 14 by detecting the variation of the area of the windows 60a and 60b facing them when the floating member 14 is fitted on the stationary member 12. An axial position detector 62 similar to the radial position detectors is mounted on the end wall 24 of the inner cylinder 20 of the stationary member 12. The axial position detector 62 can measure the distance to the inner surface of the end wall 30 of the floating member 14 when the floating member 14 is fitted on the stationary member 12. The detectors and control coils noted above are electrically connected to a drive unit 66 through an electric code as shown in Fig. 2. The drive unit 66 controls the energization of the control coils according to signals from the detectors. The operation of the first embodiment of the positioning device will now be described. When the floating member 14 is fitted on the stationary member 12, as shown in Fig. 2, four magnetic circuits Ma to Md are defined between the stationary member 12 and floating member 14. The fluxes from the pair permanent magnets 34a and 36a among the permanent magnets 34a to 34d and 36a to 36d pass through the magnetic circuit Ma, which extends from the permanent magnet 34a, axial direction control coil 42, outer cylinder 18 of the stationary member 12, axially adjacent portions of the radial direction control coil 50a and circumferential direction control coil 52a, outer cylinder 26 of the floating member 14, axially adjacent portions of the radial direction control coil 50e and circumferential direction control coil 52e, outer cylinder 18 of the stationary member 12, axial direction control coil 44, permanent magnet 36a, inner cylinder 28 of the floating member 14 and back to the permanent magnet 34a. The remaining pairs of permanent magnets 34b and 36b, 34c and 36c and 34d and 36d define the respective magnetic circuits Mb to Md like the pair of permanent magnets 34a and 36a. The floating member 14 is held with respect to the stationary member 12 in non-contact state thereto by the magnetic forces of the magnetic circuits Ma to Md acting between the stationary member and floating member 14. When current flows in each coil with the floating member 14 supported with respect to the stationary member 12 in non-contact state thereto, each coil receives an electromagnetic force which is proportional to the length of its portion crossing the magnetic flux of the magnetic circuit M and the current flowing in it. The direction of this electromagnetic force is determined by the Fleming's rule. When the electromagnetic force acts on each coil, however, the coil is not moved because the coil is secured to the stationary member 12. Therefore, the reaction force to the electromagnetic force acting on the control coil acts on the floating member 14. As a result, the floating member 14 is moved by the reaction force of the electromagnetic force. While the operational principles of the positioning device according to the invention is as described above, the operation of positioning of the floating member 14 will now be described with reference to Figs. 5 to 7. In Figs. 5 to 7, members which are irrelevant to the explanation are omitted. The process of positioning the floating member 14 in the radial direction will be explaining with reference to Fig. 5. When displacing the floating member 14 in the radial direction as shown by arrow Fx in Fig. 5, axially upward current flows in axial portions of the radial position control coils 50a and50e crossing the flux of the magnetic circuit Ma, and axially downward current flows in axial portions of the radial position control coils 50c and 50g crossing the flux of the magnetic circuit Mc. As a result, electromagnetic forces far and fcr in the direction of arrows in Fig. 5 act on the axial portions of the radial direction control coils 50a and 50e and the axial portions of the radial position coils 50c and 50g. The floating member 14 thus receives a reaction force Fx opposite to the direction of the electromagnetic forces far and fcr, so that the floating member 14 is displaced in the radial direction as shown by the reaction force Fx. As a result, the positioning of the floating member 14 in the radial direction as shown by the reaction force Fx can be done by control of the magnitude of the electromagnetic forces far and fcr. When the direction of current flowing in the radial direction control coils 50a, 50e, 50c and 50g is reversed, electromagnetic forces opposite to the electromagnetic forces far and fcr act on the radial direction control coils 50a and 50c and radial direction control coils 50e and 50g. Thus, positioning of the floating member 14 can be done in the radial direction opposite to the radial direction shown by the reaction force Fx. When displacing the floating member 14 in the radial direction shown by arrow Fy in Fig. 5, axially upward current flows in the axial portions of the radial position control coils 50b and 50f crossing the flux of the magnetic circuit Mb, and axially downward current flows in the axial portions of the radial direction control coils 50d and 50h crossing the flux of the magnetic circuit Md. Thus, the electromagnetic forces fbr and fdr in the direction of the arrows in Fig. 5 act on the axial portions of the radial direction control coils 50b and 50f and axial portions of the radial direction control coils 50d and 50h. The floating member 14 thus receives a reaction force Fy in the opposite direction to the electromagnetic forces fbr and fdr. Thus, the positioning of the floating member 14 in the radial direction as shown by the reaction force Fy can be done by control of the magnitude of the electromagnetic forces fbr and fdr. Also, by reversing the sense of current flowed in the radial direction control coils 50b, 50f, 50d and 50h the floating member 14 can be displaced in the opposite sense to the radial direction shown by the reaction force Fy. The magnitude of current supplied to the radial direction control coils 50a to 50h can be controlled by the drive unit 66 according to signals from the radial position detectors 54a, 54b, 56a and 56b. Now, the process of positioning the floating member 14 in the circumferential direction will be described. When rotationally displacing the floating member 14 in the circumferential direction shown by arrow Fr in Fig. 6, axially upward current flows in the axial portions of the circumferential position control coils 52a to 52h crossing the fluxes of the magnetic circuits Ma to Md. Thus, counterclockwise electromagnetic forces fac, fbc, fcc and fdc act on the axial portions of the circumferential position control coils 52a to 52h. The floating member 14 thus is rotationally displaced in the clockwise direction by a clockwise reaction force Fr of the opposite sense to the electromagnetic forces fac, fbc, fcc and fdc. The circumferential position of the floating member 14 in the clockwise direction thus can be controlled through control of the magnitude of the electromagnetic forces fac, fbc, fcc and fdc. Thus, by reversing the sense of the current flowing in the circumferential position control coils 52a to 52h a reaction force in the counterclockwise direction may be acted on, whereby the floating member 14 can be positioned circumferentially in the counterclockwise direction. In such circumferential positioning of the floating member 14, the magnitude of current supplied to the circumferential direction control coils 52a to 52h is controlled by the drive unit 66 in accordance with the signals from the circumferential position detectors 58a and 58b. Lastly, the process of axially positioning the floating member 14 will be described. As is seen from Fig. 7, the axial position control coils 42 and 44 cross the opposite sense fluxes of the magnetic circuits Ma to Md. In Fig. 7, only the magnetic circuits Ma and Mc are shown. When opposite sense currents flow in the axial position control coils 42 and 44, electromagnetic forces of the same sense act on the axial direction control coils 42 and 44 in the axial direction of the floating member 14. For example, when a counterclockwise current when viewed from above Fig. 7 flows in the axial position control coil 42 while flowing a clockwise current in the other axial position control coil 44, downward electromagnetic forces faz and fbz as shown by arrows in Fig. 7 act on the axial position control coils 42 and 44. The floating member 14 thus receives an axially upward reaction force Fz in Fig. 7 of the opposite sense to the electromagnetic forces faz and fbz and is thus displaced axially upwardly. The axial positioning of the floating member 14 thus can be done by control of the magnitude of current supplied to the axial position control coils 42 and 44. Further, by reversing the current flowing in the axial position control coils 42 and 44, the floating member 14 receives an axially downward reaction force and is displaced axially downwardly. The magnitude of current flowing in the axial position control coils 42 and 44 is controlled by the drive unit 66 in accordance with the signals from the axial position detector 62. As has been shown, with the first embodiment of the positioning device the floating member 14 can be supported with respect to the stationary member 12 in a non-contact state thereto by electromagnetic forces produced by the magnetic circuits Ma to Md. The radial position, circumferential position and axial position of the floating member 14 can be controlled independently through control of the magnitude of current flowing in the corresponding control coils. According to the invention, the drive force utilized for the individual position controls of the floating member 14, i.e., the electromagnetic force produced by the co-operation of the constant magnetic field produced by the magnetic circuits Ma to Md and current through the respective control coils, is not utilized for the supporting of the floating member 14. Thus the individual position controls of the floating member 14 can be obtained by control of the magnitude of the electromagnetic force independently of the magnitude of the magnetic gap between the stationary member 12 and floating member 14. Further, the magnitude of the electromagnetic force is linearly proportional to the magnitude of the current flowing in each control coil. Thus, it is possible to simplify the construction of the drive unit 66 for controlling the current through the control coils and also obtain highly accurate control of the current flowing in the control coils. In other words, it is possible to effect the individual position controls of the floating member 14 highly accurately. Further, in the first embodiment of the invention the detectors and control coils are mounted on the stationary member 12, so that the transmission of signal from each detector to the drive unit 66 and supply of current from the drive unit 66 to each control coil can be readily done to simplify the construction of the entire positioning device according to the invention. Further, in the first embodiment the floating member 14 is made of an electromagnetic shield material and is disposed to cover the stationary member 12, i.e., the entire position control means 16. Therefore, the electromagnetic waves generated from the position control means 16 are shielded by the floating member 12 to eliminate leakage of electromagnetic waves from the positioning device according to the invention to the outside. Thus, the first embodiment of the positioning device may be disposed near an apparatus which is readily susceptible to the influence of the electromagnetic waves. The first embodiment of the positioning device described above is by no means limitative, and other embodiments will now be described, in which parts like those in the first embodiment are shown by like reference symbols and numerals. Referring to Figs. 8 and 9, a second embodiment of the positioning device according to the invention, is shown. In this case, the outer periphery of the inner cylinder 20 of the stationary member 14 are provided with three rows of permanent magnets 80a to 80d, 82a to 82d and 84a to 84d, these rows being arranged in the axial direction. In this embodiment, a pair of magnetic circuits Ma1 and Ma2, a pair of magnetic circuits Mb1 and Mb2, a pair of magnetic circuits Mc1 and Mc2 and a pair of magnetic circuits Md1 and Md2, correspond to the respective magnetic circuits Ma to Md in the first embodiment. In correspondence to the three rows of permanent magnets 80a to 80d, 82a to 82d and 84a to 84d, the outer periphery of the outer cylinder 18 of the stationary member 12 is provided with twelve radial position control coils 50a to 50ℓ and twelve circumferen tial position control coils 52a to 52ℓ, these coils being arranged in three rows in the axial direction. In Figs. 8 and 9, the radial and circumferential direction control coils are shown only partly. In the case of the second embodiment, only a single axial position control coil 86 is provided. As is seen from Fig. 8, the axial position control coil 86 is secured to the inner periphery of the outer cylinder 18 of the stationary member 12 such that it faces the permanent magnets 82a to 82d, through which fluxes of the highest flux density pass. With the second embodiment of the positioning device described above, in which the permanent magnets are provided on the stationary member 12 in three rows in the axial direction and also the radial and circumferential control coils are also provided in three rows, it is possible to obtain large magnetic forces for supporting the floating member 14 and also large drive forces, i.e., electromagnetic forces, for the individual positioning controls. Thus, even if a large load is applied to the floating member 14, the floating member 14 can be reliably supported with respect to the stationary member 12 in non-contact state thereto, and also the floating member 14 can be readily displaced in each direction. Fig. 10 shows a third embodiment of the positioning device. This embodiment of the positioning device is substantially the same in structure as the first embodiment. In this embodiment, however, the inner periphery of the outer cylinder 26 of the floating member 14 is also provided with permanent magnets 100a to 100d and 102a to 102d corresponding to the respective permanent magnets 34a to 34d and 36a to 36d. In this embodiment, it is not only possible to satisfactorily eliminate leakage of the fluxes generated from the magnetic circuits Ma to Md to the outside of the floating member 14, but also the magnitude of the fluxes can be increased. Thus, like the case of the second embodiment a large load applied to the floating member 14 can be readily withstood, and also a large drive forces can be generated for the individual positioning controls of the floating member 14. Fig. 11 shows a fourth embodiment of the positioning device. This embodiment is different from the first embodiment in that electromagnets 110a to 110d and 112a to 112d are used in stead of the permanent magnets 34a to 34d and permanent magnets 36a to 36d. While in the above embodiments the stationary member 12 is surrounded by the floating member 14, it is possible to have the floating member 14 surrounded by the stationary member 12. Further, the twofold structure of the stationary member 12 and floating member 14 described above is by no means limitative, and it is possible to adopt more than twofold wall structure.

Claims: A positioning device of magnetic suspension type, comprising; a stationary member (12); and a movable member (14) facing said stationary member (12); characterized by means (16a) for generating a Lorentz's force which is directed from one of said members to the other member, including means (34,36) for generating a magnetic flux which is directed from one of said members to the other member and first conductive members (42,44) arranged perpendicular to the magnetic flux thereby causing said movable member to float vertically from said stationary member, in a state wherein said movable member is not in contact with said stationary member; and means (66) for adjusting the magnitude of the Lorentz's force by adjusting the magnitude of the current in said conductive members thereby adjusting the position of said movable member with respect to said stationary member, thus positioning said movable member relative to said stationary member. A positioning device according to claim 1, in which said generating means generates said magnetic flux horizontally; said first conductive members (42,44) are arranged perpendicular to the magnetic flux and extend horizontally; and said device further comprises; means for supplying current to said first conductive members, whereby a Lorentz's force is vertically generated, and said movable member is caused to float by the Lorentz's force thus generated, in a state wherein said movable member is not in contact with said stationary member; and means (62) for detecting the position of said movable member with respect to said stationary member in the vertical direction and producing a detection signal such that said adjusting means adjusts the magnitude of the current in accordance with the detection signal, thereby adjusting the magnitude of the Lorentz's force so as to adjust the position of said movable member with respect to said stationary member in the vertical direction, thus positioning said movable member relative to said stationary member in the vertical direction. A positioning device according to claim 1, in which said generating means (34, 36) generates said magnetic flux horizontally and said device further comprises; second conductive members (50a-50h, 52a-52h), arranged perpendicular to the magnetic flux and extending vertically; means (66) for supplying current to said second conductive members, whereby a Lorentz's force is horizontally generated, and said movable member is caused to move away from said stationary member by the Lorentz's force thus generated; and means (54a, 54b, 56a, 56b) for detecting the position of said movable member with respect to said stationary member in the horizontal direction, and producing a detection signal such that said adjusting means adjusts the magnitude of the current in accordance with the detection signal, thereby adjusting the magnitude of the Lorentz's force so as to adjust the position of said movable member with respect to said stationary member in the horizontal direction, thus positioning said movable member in the horizontal direction. A positioning device according to claim 2 or claim 3 in which said magnetic force generating means (34, 36, 110) includes at least one element being secured to said movable member, the conductive members of said driving means being secured to said stationary member. A positioning device according to claim 4, in which said movable member comprises an outer cylinder (26) and the or each element is disposed on an inner periphery of said cylinder facing said conductive members. A positioning device according to claim 4, in which the element (110) is an electromagnet. A positioning device according to any one of the claims 5 to 6, in which said stationary member (12) is made of non-magnetic material and has an outer cylinder (18) and an inner cylinder (20) provided in and coaxially with the outer cylinder (18), said movable member (14) is made of a high magnetic permeability material and has a hollow inner cylinder (28) provided between the inner (20) and the outer (18) cylinders of said stationary member (12) and the outer cylinder (26) positioned coaxially with the inner cylinder (28) and surrounding the outer cylinder (18) of said stationary member, the or each element being secured to the outer periphery of the inner cylinder (20) of said movable member (14) and defines a magnetic circuit in co-operation with the inner (28) and the outer (26) cylinders of said movable member (14); and the conductive members are secured to the outer cylinder (18) of said stationary member (12). A positioning device according to claim 7, in which said movable member is made of a material having a high magnetic permeability thereby serving as an electromagnetic shield material. A positioning device according to claim 8, in which said movable member is made of silicon steel. A positioning device according to any one of claims 7 to 9, in which said magnetic force generating means includes a plurality of permanent magnets (34) arranged at a uniform circumferential spacing on the outer periphery of the inner cylinder of said movable member and a plurality of second permanent magnets (36) provided at a uniform circumferential spacing on the outer periphery of the inner cylinder of said movable member and at a predetermined distance from and with the same circumferential phase as the first permanent magnets, and said first conductive members include a pair of first direction position control coils (42, 44) provided on the inner periphery of the outer cylinder of said stationery member facing the first and second permanent magnets. A positioning device according any one of claims 7 to 10 when dependent on claim 2, in which said detecting means includes at least one distance detector (62) for detecting the axial position of said movable member relative to said stationary member. A positioning device according to claim 11, in which the distance detector is an eddy current type sensor. A positioning device according to any one of claims 7 to 12 when dependent on claim 3, in which said detecting means include at least one pair of distance detectors (54) provided on the outer periphery of the inner cylinder of said stationary member and circumferentially spaced apart by 90 degrees for detecting the radial position of said movable member relative to said stationary member through measurement of the distance between the inner cylinder of said stationery member and the inner cylinder of said movable member. A positioning device according to claim 13, in which said detecting means includes, in addition to one pair of distance detectors, another pair of distance detectors (56) axially spaced apart from said first-mentioned distance detectors. A positioning device according to claim 14, in which the distance detector is an eddy current type sensor. A positioning device according to any one of claims 13 to 15, in which said detecting means (58, 60) includes third direction position detection means for detecting the circumferential direction of said movable member relative to said stationary member. A positioning device according to claim 16, in which the third direction position detection means includes a pair of axial slots (60) formed in said inner cylinder of said movable member at diametrically opposite positions and a pair of eddy current sensors (58) secured to the outer periphery of the inner cylinder of said stationary member such that they face the slots facing them. A positioning device according to any one of claim 7 to 9, in which said magnetic force generating means includes a plurality of third permanent magnets (80, 82, 84) provided at a uniform circumferential spacing on the inner periphery of the outer cylinder (28) of said movable member (24) instead of said first and second permanent magnets. A positioning device according to claim 18, in which said driving means includes as the conductive members first direction position control coils (86) provided on the inner periphery of the outer cylinder (18) of said stationary member (12) and facing said third permanent magnets(80, 82, 84). A positioning device according to any one of claims 7 to 9, in which said magnetic force generating means includes third permanent magnets (100, 102) provided on the inner periphery of the outer cylinder (26) of said movable member (14) facing the first and second permanent magnets.

Inventors: SUDO, HAJIME C/O PATENT DIVISION, TAKAHASHI, HIROSHI C/O PATENT DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1985
Main classification: H02N15
IPC codes: H02N15, H02K33, H02K49, F16C39, H02K7