Boots – shoes – and leggings
Patent
1997-04-29
1999-07-13
Grant, William
Boots, shoes, and leggings
36447415, 36447416, G06F 1900, G06G 76466
Patent
active
059235594
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic bearing apparatus which may be applied to a main shaft of a turbo molecular pump or a machine tool.
BACKGROUND OF THE INVENTION
FIG. 7 is a schematic view showing an overall concept of a magnetic bearing apparatus which is of a conventional five axis control type.
In the conventional magnetic bearing apparatus, a pair of right and left radial bearings 2 and 3 for a rotor 1 are disposed and a thrust bearing 4 is disposed on the right side. The radial bearing 2 is structured so that stationary electromagnets 2A and 2B radially attract a cylindrical rotor ferric core 1A mounted on the rotor 1 and magnetically bear the rotor 1 in the radial direction at its center. Also, the radial bearing 3 is structured so that stationary electromagnets 3A and 3B radially attract a cylindrical rotor ferric core 1B mounted on the rotor 1 and magnetically bear the rotor 1 in the radial direction at its center. Furthermore, the thrust bearing 4 is structured so as to magnetically receive the rotor 1 in the axial direction under the condition that a circular rotary ferric core 5 is attracted by electromagnets 6 on the right and left sides.
A radial shift sensor 7 for detecting a shift of the rotor 1 in a direction of an X-axis (X1) at a portion of the radial bearing 2 and a radial shift sensor 8 for detecting a shift of the rotor 1 in a direction of a Y-axis (Y1) at the portion of the radial bearing 2 are disposed in the portion of the radial bearing 2. Also, a radial shift sensor 9 for detecting a shift of the rotor 1 in a direction of an X-axis (X2) at a portion of the radial bearing 3 and a radial shift sensor 10 for detecting a shift of the rotor 1 in a direction of a Y-axis (Y2) at the portion of the radial bearing 3 are disposed in the portion of the radial bearing 3. Furthermore, an axial direction shift sensor 11 for detecting a shift of the rotor 1 in a Z-axis direction is disposed at a position facing an end face of the rotor 1.
FIG. 8 shows a control system for the conventional magnetic bearing apparatus shown in FIG. 7.
The control system for the magnetic bearing apparatus is provided with a microprocessor 13 for performing a calculation process, to be described later, for controlling the magnetically floated position of the rotor 1 to the centers or the like of the magnetic bearings 2 and 3. A/D (analog/digital) convertors 14 to 18 are connected on an input side of the microprocessor 13. The axial direction shift sensor 11 and radial direction shift sensors 7, 9, 8 and 10 are connected to the A/D convertors 14 to 18, respectively. Also, D/A (digital/analog) convertors 19 to 23 are connected on an output side of the microprocessor 13. The electromagnets 6, 2A, 3A, 2B and 3B are connected to the D/A convertors 19 to 23, respectively.
The operation of the conventional magnetic bearing apparatus having such an arrangement will now be described with reference to FIGS. 10 and 11.
In this case, after the rotor 1 has been magnetically lifted by the radial bearings 2 and 3 and the thrust bearing 4, when an electric power is supplied to a coil of a motor stator (not shown), the rotor 1 is brought into a rotative condition. Then, in accordance with the commands of the microprocessor 13, the A/D conversions of the detected shift signal pz of the axial direction shift sensor 11 concerning the Z-axis direction of the rotor 1 and the detected shift signals px1, px2, py1 and py2 of the radial direction shift sensors 7, 9, 8 and 10 concerning the Y-axis and X-axis of the rotor 1 are started by the A/D convertors 14 to 18 simultaneously all in the five axes (step 1). When this A/D conversion has been completed, the converted signals corresponding to the five axes are orderly entered into the microprocessor 13 (step 2), and the microprocessor 13 seeks the current command value iz of the electromagnet 6 concerning the control in the Z-axis, and the respective current command values px1, px2, py1 and py2 of the electromagnets 2A, 3A, 2B and 3B concerning th
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Grant William
Patel Ramesh
Seiko Seiki Kabushiki Kaisha
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