JP2849916B2 - Radial magnetic bearing rotor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a radial bearing device for a turbomachine or a machine tool, and more particularly, to a rotor yoke fixed to a rotating shaft and provided with a minute gap from the rotor yoke. An electromagnet stator having an excitation coil for generating a magnetic force is fixed to a casing, a displacement sensor for measuring a relative displacement between a rotating shaft and the casing is provided, and the rotor and the electromagnet are used based on an output signal from the displacement sensor. The present invention relates to a radial magnetic bearing rotor in which a magnetic attraction force acts between stators to support a rotating shaft near the center of the stator.

(Prior art)

FIG. 4 is a sectional view showing the structure of a spindle supported by a conventional 5-axis control type bearing, and FIG.
FIG. 6 is a sectional view taken along line II-II of FIG. 4.

In FIG. 4, the rotating shaft 41 is driven by a motor having a motor stator 48 and a motor rotor 49 provided at the center of a casing 47, and the rotating shaft 41 is provided on both sides of the motor. It is supported by two radial magnetic bearings and a thrust magnetic bearing adjacent to one of the radial magnetic bearings.

The radial magnetic bearing includes a radial bearing stator 43 having a stator coil 45, a radial bearing yoke 44 mounted on a rotating shaft 41, and a radial displacement sensor 46, and the thrust magnetic bearing is fixed. And a thrust bearing 50 having a child coil 52. Reference numeral 42 denotes an emergency rolling bearing.

[Problems to be solved by the invention]

In the above-described radial magnetic bearing, when supporting a high-speed rotating body, the diameter of the rotating shaft 41 is limited due to the limitation on the material strength or the spatial control of the centrifugal force of the silicon steel plate and other rotating members used for the radial bearing yoke 44. I can't make it fat. For this reason, the bending natural frequency of the rotating shaft 41 decreases, and the rotating shaft 41
When controlling up to a high frequency range including the bending natural frequency of the rotating shaft 41 in the radial magnetic bearing supporting
Since the induction resistance of the coil increases, it becomes necessary to provide a high-voltage power supply. However, at a frequency higher than the natural frequency (break frequency) of the rigid body mode of the rotating shaft 41 supported by the magnetic bearing, the gain of the open-loop transfer function becomes
Due to the inertia effect of the rotating shaft 41, it is reduced at 40 dB / decade. Reduce losses.

FIG. 7 is a diagram showing gain characteristics of an open-loop transfer function of control when the natural frequency of bending of the rotating shaft exists. In FIG. 7, the solid line shows the case where the diameter of the rotating shaft is large and the natural frequencies of the rigid mode and the bending mode are sufficiently separated from each other, and the broken line shows that the diameter of the rotating shaft is thin and the natural frequency of the rigid mode and the bending mode is small. This is the case when approaching.

In the case of the solid line, the gain at the bending natural frequency is smaller than 0 dB, and this natural frequency does not oscillate,
In the case of the broken line, the gain of the bending natural frequency becomes a value close to 0 dB, and there is a problem that the natural frequency may oscillate.

The present invention has been made in view of the above points, and provides a rotor of a radial magnetic bearing capable of eliminating the oscillation of the rotor bending natural frequency without increasing the power supply voltage of the magnetic bearing. It is in.

[Means for solving the problem]

In order to solve the above problems, the present invention provides a rotor yoke fixed to a rotating shaft, and an electromagnet fixed with a coil which is fixed to a casing with a small gap from the rotor yoke and generates a magnetomotive force. A radial magnet for controlling a magnetic attraction force acting between a rotor yoke and an electromagnet stator based on an output signal from the displacement sensor for measuring a relative displacement between a rotor and a rotating shaft and a casing. In the rotor of the bearing, a circular hole concentric with the center line is provided in the rotating shaft, and a cylindrical material having an outer diameter equal to the diameter of the circular hole is fitted and fixed in the circular hole, and the material of the cylindrical material is vibrated. The material is characterized by using a material whose vibration damping capacity for damping the vibration is greater than that of the material of the rotating shaft.

In addition, a metal cylinder having an outer diameter smaller than the diameter of the circular hole is inserted into the circular hole, and both the elastic action and the vibration damping action are applied to the entire or a part of the gap between the circular hole and the metal cylinder. The metal column is movably supported by inserting a material having the metal column.

The rotary shaft is provided with a circular hole concentric with the center line thereof, and the circular hole is filled with a viscous liquid.

[Action]

By configuring the rotor of the radial magnetic bearing as described above, in any of the rotors, it is possible to increase the damping of the rotating shaft and reduce the response magnification at the natural frequency of bending, and as a result, the gain of the open-loop transfer function of the control system is increased. The peak gain at the characteristic natural frequency in the characteristic curve can be reduced, and oscillation at this frequency can be prevented.

That is, when a cylinder made of a material having a larger vibration damping capacity than the rotary shaft material is inserted and fixed in the circular hole, the vibration damping action by the deformation of the cylinder in the circular hole increases the vibration damping capacity of the rotary shaft. be able to.

Further, when a metal cylinder having an outer diameter smaller than the diameter of the hole is movably supported in the circular hole by a material having an elastic action and a vibration damping action, the metal caused by the relative vibration between the metal cylinder and the rotating shaft is formed. Damping due to deformation of the material supporting the cylinder can increase the vibration damping ability of the rotating shaft.

Also, when filling the viscous liquid in the circular hole,
Due to the viscous damping due to the flow of the liquid in the rotating shaft due to the bending vibration of the rotor, the damping ability of the rotating shaft can be increased.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of the rotor of the radial magnetic bearing according to the present invention. As shown in the figure, a circular hole 2 is formed in the rotary shaft 1 concentric with the center line thereof, and a vibration damping capacity greater than that of the material of the rotary shaft 1 such as lead or Mg-Zr alloy is formed in the circular hole 2. And a column 3 having the same outer diameter as the diameter of the circular hole 2 is inserted and fixed. In the figure,
4 is a radial bearing yoke and 9 is a displacement sensor target.

In the rotor having the above-described structure, when the rotating shaft 1 is bent and deformed, the cylinder 3 is also subjected to bending deformation and induces a vibration damping action of the material forming the cylinder 3, thereby reducing the vibration damping ability of the rotating shaft. Can be enhanced.

FIG. 2 is a sectional view showing a structure of a rotor of another radial magnetic bearing according to the present invention. As shown in FIG. 1, a circular hole 2 is formed concentrically with the center line of the rotating shaft 1, and a metal cylinder 5 having an outer diameter smaller than the diameter of the circular hole is inserted into the circular hole 2. A rubber O-ring 6 is interposed in a gap between the circular hole 2 and the metal cylinder 5 to make the metal cylinder 5
And the rotary shaft 1 is movably supported so as to generate relative vibration at the natural frequency of bending of the rotary shaft 1.

When the rotor has the above structure, the damping action of the O-ring 6 is induced, and the damping ability of the rotating shaft 1 can be increased. In the above example, the metal cylinder 5 is movably supported by the O-ring 6. However, the supporting means is not limited to the O-ring 6, and is essentially a material having an elastic action and a vibration damping action, for example, Any shape may be used as long as the material is made of a rubber material, a gel material based on silicone, or a gel material based on a polymer material, and a portion supporting the metal column 5 is also partially limited. Instead, it may be interposed in the entire gap between the circular hole 2 and the metal column 5.

FIG. 3 is a sectional view showing the structure of a rotor of another radial magnetic bearing according to the present invention. As shown in FIG. 1, a circular hole 2 is formed on a rotating shaft 1 concentric with its center line.
Is filled with a liquid 7 having a high viscosity, and a plug 8 for preventing leakage of the liquid 7 is fitted into the circular hole 2 at the end of the rotating shaft 1.

When the rotor has the above structure, when the rotating shaft 1 is bent and deformed, the liquid 7 filled in the circular hole 2 flows,
The flow of the liquid 7 induces a vibration damping action due to the viscosity of the liquid 7. Thereby, the vibration damping ability of the rotating shaft 1 can be increased.

When the vibration damping ability of the rotating shaft 1 increases as described above, the resonance magnification at the bending natural frequency decreases. Therefore, the gain characteristic of the open loop transfer function of the magnetic bearing control system is improved, and oscillation of the bending natural frequency can be prevented.

〔The invention's effect〕

As described above, according to the present invention, oscillation of the rotor bending natural frequency can be prevented without requiring a high-voltage magnetic bearing control power supply, that is, without increasing power loss, and An excellent effect that a rotor of a radial magnetic bearing can be provided is obtained.

[Brief description of the drawings]

FIGS. 1, 2, and 3 are cross-sectional views showing the structure of a rotor of a radial magnetic bearing according to the present invention, and FIG. 4 shows the structure of a spindle supported by a conventional 5-axis control type bearing. FIG. 5 is a sectional view taken along line II of FIG. 4, FIG. 6 is a sectional view taken along line II-II of FIG. 4, and FIG. FIG. 10 is a diagram illustrating gain characteristics of an open loop transfer function of control when the control exists. In the figure, 1 ... rotating shaft, 2 ... circular hole, 3 ... cylinder, 4 ...
... radial bearing yoke, 5 ... metal cylinder, 6 ... O-ring, 7 ... liquid, 8 ... plug for leakage prevention, 9 ... displacement sensor target.

Claims (3)

(57) [Claims] A rotor yoke fixed to a rotating shaft, an electromagnet stator including a coil fixed to a casing with a minute gap from the rotor yoke and generating a magnetomotive force; A radial magnetic bearing comprising a displacement sensor for measuring a relative displacement between a shaft and a casing, and controlling a magnetic attraction force acting between the rotor yoke and the electromagnet stator based on an output signal from the displacement sensor. In the rotor, a circular hole concentric with the center line is provided on the rotating shaft, and a cylindrical material having an outer diameter equal to the circular hole diameter is fitted and fixed in the circular hole, and vibration is applied to the material of the cylindrical material. A rotor for a radial magnetic bearing, wherein a material having a vibration damping capacity to be attenuated is larger than a vibration damping capacity of the material of the rotating shaft. 2. A rotor yoke fixed to a rotating shaft, made of a magnetic material, an electromagnet stator having a coil provided with a minute gap from the rotor yoke and fixed to a casing to generate a magnetomotive force, and A radial magnetic bearing comprising a displacement sensor for measuring a relative displacement between a shaft and a casing, and controlling a magnetic attraction force acting between the rotor yoke and the electromagnet stator based on an output signal from the displacement sensor. In the rotor, a circular hole concentric with the center line is provided on the rotation shaft, and a metal cylinder having an outer diameter smaller than the diameter of the circular hole is inserted into the circular hole, and the circular hole and the metal cylinder are connected to each other. A rotor for a radial magnetic bearing, wherein a material having an elastic action and a vibration damping action is inserted into the whole or a part of the gap between the metal columns to movably support the metal column. 3. A rotor yoke fixed to a rotating shaft, made of a magnetic material, an electromagnet stator provided with a coil which is fixed to a casing with a minute gap from the rotor yoke and generates a magnetomotive force, and A radial magnetic bearing comprising a displacement sensor for measuring a relative displacement between a shaft and a casing, and controlling a magnetic attraction force acting between the rotor yoke and the electromagnet stator based on an output signal from the displacement sensor. A rotor for a radial magnetic bearing, wherein a circular hole concentric with a center line of the rotary shaft is provided in the rotor, and the circular hole is filled with a viscous liquid.