JPS6134004B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic shaft device for a flywheel that levitates, guides and supports a rotating body without contact.

Conventionally, when a rotating body is floated and supported by three DC electromagnets arranged concentrically at equal intervals, the DC electromagnets 1a, 1b, and 1c are arranged as shown in FIG. FIG. 2 shows a cross section of the electromagnet. In addition, FIG. 3 shows the DC electromagnets 1a, 1b, 1c as described above.
The distribution of magnetic fluxes φa, φb, and φc of each DC electromagnet with respect to the rotation direction when arranging them is shown. In this case, the outer pole side (N pole in the figure) is shown, and its size is φa=φb=φc.

With such a magnetic flux distribution, the rotating body is suspended and supported, and when it rotates, the magnetic flux φ of the DC electromagnets 1a, 1b, 1c
a, φb, φc represent the change in magnetic flux △φ as shown in Fig. 3, and the induced starting force e=- in the secondary core provided on the rotating body facing the DC electromagnets 1a, 1b, 1c dφ/dt occurs, eddy current flows, and eddy current loss occurs.

This eddy current loss acts on the rotating body as a loss of the rotating body, that is, a braking force. For this reason, the capacity of the device (electric motor) that drives the rotating body increases by a capacity corresponding to the braking force. Also, from the above equation, it can be seen that the eddy current loss is proportional to the change in magnetic flux and the rotation speed. Therefore, it is not preferred as a magnetic bearing for a flywheel that rotates at high speed.

The present invention has been made to alleviate the above-mentioned drawbacks, and consists of three levitation DC electromagnets arranged concentrically at equal intervals and with the same poles, and between the inner and outer poles of the iron core ends of the three DC electromagnets. The present invention provides a rational magnetic bearing device for a flywheel that can reduce eddy current loss by short-circuiting with a magnetic ring plate.

FIG. 4 shows the basic configuration of the levitation DC electromagnet according to the present invention. FIG. 5 is a sectional view thereof.

In FIG. 4, DC electromagnets 1a, 1b, and 1c are arranged on concentric circles with the same poles at equal intervals, and the N-pole side and the S-pole side of the iron core end are short-circuited by magnetic ring plates 3a, 3b.

Figure 6 shows the DC electromagnets 1a, 1b, 1c in Figure 4.
This shows the magnetic flux distribution with respect to the rotation direction.
This magnetic velocity distribution indicates the outer pole side (N pole), and the magnitude of the magnetic flux φ is assumed to be φa=φb=φc.

In this case, the magnetic flux distribution is between each DC electromagnet (1a-1b, 1b-1c, 1c-1
The magnetic flux distribution is such that the _minimum magnetic flux is at the midpoint between
become smaller.

Therefore, by short-circuiting the core ends of the DC electromagnets 1a, 1b, 1c with the ring plates 3a, 3b, the sixth
As shown in the figure, the change in magnetic flux distribution with respect to the rotation direction △
By reducing _φ2 , it is possible to reduce eddy current loss occurring in the secondary core of the rotating body, which causes loss of rotational force.

FIG. 7 shows a schematic configuration of a flywheel device to which the present invention is applied. In FIG. 7, reference numeral 13 denotes a pedestal, and on the top of this pedestal 13, three DC electromagnets 1a, 1b, and 1c are arranged concentrically at equal intervals and with the same polarity. These DC electromagnets are each independently connected to the rotating body 6.
Generates electromagnetic attraction force against. In this case, the DC electromagnets 1a, 1b, 1c have ring plates 3a, 3b short-circuiting between the inner and outer poles of the magnetic pole faces facing the rotating body 6.

Furthermore, displacement meters 7a, 7b, and 7c are provided corresponding to the DC electromagnets 1a, 1b, and 1c to detect the gap lengths between the rotating body 6 and the DC electromagnets 1a, 1b, and 1c.
The rotating body 6 has a thick outer circumferential portion, and a secondary iron core is provided on the surface facing the DC electromagnets 1a, 1b, and 1c, and serves as a flywheel. A secondary core 14 for guiding is provided at the lower part of the rotating body 6, and DC electromagnets 8a, 8b, 8c, and 8d for guiding are arranged around this secondary core 14 at equal intervals.

FIG. 8 shows an example of the arrangement of the displacement meter 9 for detecting the gap length between the guiding DC electromagnets 8a, 8b, 8c and the secondary core 14 and the guiding DC electromagnet 8.

In FIG. 8, reference numeral 12 denotes a shaft, and surrounding the shaft is a secondary core 14. Guide DC magnets 8a, 8b, 8c, and 8d are arranged around this secondary core 14 at equal intervals. In this case, the displacement meter 9 includes DC electromagnets 8a, 8b,
It corresponds to two of 8c and 8d and is placed at a position with a phase difference of 90 degrees. In FIG. 8, they are arranged corresponding to DC electromagnets 8a and 8b.

In addition, in FIG. 7, the upper part of the rotating body 6 has a shaft 1
A rotor 10 is provided through the rotor 2, and an armature winding 11 is provided around the rotor 10, thereby forming a contactless electric motor that provides rotational drive to the rotating body 6. This electric motor has a rotating body 6
It is used as a generator when converting the rotational energy of the rotating body 6, which acts as a flywheel, into electrical energy.

Next, FIG. 9 shows an example of a gap length control circuit for the levitation DC electromagnets 1a, 1b, and 1c. For convenience of explanation, FIG. 9 shows only the gap length control circuit corresponding to the DC electromagnet 1a.

In FIG. 9, the displacement meter 7a and the gap length setting device 1
Each output of 6 is connected to a comparator 30. This comparator 30 compares the outputs of both, generates a deviation ε ₁ , and connects this to the comparator 31 together with the output of the parallel compensation circuit 17. In this case, parallel compensation circuit 1
7 is the first derivative (velocity) of the displacement of the displacement meter 7a and 2
It consists of a second derivative (acceleration) circuit and works to stabilize the control system.

The comparator 31 connects the above deviation ε ₁ to the parallel compensation circuit 17.
A deviation ε ₂ is generated by adding the output of , and is connected to the comparator 32 via the series compensation circuit 18 . This series compensation circuit 18 functions to increase the control loop gain and reduce the steady state deviation. (In some cases, integral control is performed to make the steady-state deviation zero.) The comparator 32 is a sawtooth wave oscillator that generates a negative waveform output with the deviation ε ₂ passed through the series compensation circuit 18 as a maximum value of zero. When the additional deviation _ε of the output of 19 is added, the waveform portion lifted in the positive direction is output ε
₃ , which is inputted via the Schmitt circuit 20 to a power converter array, such as a chopper circuit 22a.

A DC electromagnet 1a is connected in series to this chopper circuit, and a wheeling diode 23a is connected in parallel to the DC electromagnet 1a. The output ε ₃ turns on the chopper circuit 22a for a period increased by the deviation ε ₂ , and a current corresponding to the on period is supplied to the DC electromagnet 1a. By this, electromagnet 1
A generates an attractive force proportional to the current as a levitation force of the rotating body 6.

By controlling the current of the DC electromagnet 1a with the above configuration, the gap length between the DC electromagnet 1a and the rotating body 6 can be controlled to be constant. The same applies to the other DC electromagnets 1b and 1c.

Next, an example of a gap length control circuit for the guide DC electromagnet 8 is shown in FIG. For convenience of explanation, FIG. 10 shows only the guide and support gap length control circuit corresponding to the DC electromagnets 8a and 8c. In FIG. 10, the control circuit for the DC electromagnet 8a is completely the same as the floating support gap length control circuit explained in FIG. 9, so its explanation will be omitted. I will explain about it.

In FIG. 10, reference numeral 24 denotes an inverting circuit that inverts the deviation ε ₂ passed through the series compensation circuit 18, and its output is added to the output of the sawtooth wave oscillator 19 in a comparator 30. This comparator 36 outputs the waveform portion of the output of the sawtooth wave oscillator 19 lifted in the positive direction as ε ₄ , and inputs it via the Schmitt circuit 25 to a power converter, for example, a chopper circuit 26c. A DC electromagnet 8c is connected in series to this chopper circuit 26a, and a wheeling diode 28c is connected in parallel to the DC electromagnet 8c.

Next, the control operation when guiding and supporting control is performed with the above configuration will be explained with reference to FIGS. 8 and 10.

(1) When the gap length xa = xc and the rotating body 6 is at the center position.

Since the output x ₀ of the displacement meter 9a and the output xr of the gap length setting device 16 are equal, the deviation ε ₁ =0. Therefore, the chopper circuits 26a, 26c are in an off state, and no current flows through the DC electromagnets 8a, 8c.

(2) When the void length xa>xc.

The comparator 30 outputs a positive deviation with the deviation ε ₁ =xr−(−x ₀ ). This output deviation ε ₁ is added to the output from the parallel compensation circuit 17, resulting in a deviation ₂ , which is input to the series compensation circuit 18. In this case, the series compensation circuit 18 is simply an amplifier, and its amplification factor is K.
Then, the deviation ε ₂ becomes ε ₂ ×K, which is added to the sawtooth waveform of the oscillator 19 by the comparator 32 . Therefore, the sawtooth waveform is lifted in the positive direction by ε ₃ =ε ₂ ×K, and the Schmitt circuit 2
0 is the lifted period and the chopper circuit 26
Turn on a. As a result, the DC electromagnet 8a
A current flows through the secondary core 14, and an attractive force acts on the secondary core 14.
It is attracted in the direction of the DC electromagnet 8a. On the other hand, in controlling the DC electromagnet 8c, the output ε ₂ ×K of the series compensation circuit 18 passes through an inverting circuit, so ε ₂ ×K becomes negative. Therefore, the comparator 36 reduces the sawtooth waveform of the oscillator 19 by -(ε ₂ ×K).
₄ =0, and the chopper 26c is turned off.

(3) When the void length xa<xc.

The comparator 30 outputs a negative deviation of the deviation ε=xr− _x0 , and operates in the opposite manner to the case where xa>xc. In this case, the input ε ₂ ×K of the comparator 32 is negative,
The input ε ₂ ×K of the comparator 36 becomes positive, and the chopper circuit 26a is turned off and the chopper circuit 26c
turns on. Therefore, a current flows to the DC electromagnet 8c, and an attractive force acts on the secondary iron core 14, causing it to be attracted in the direction of the current electromagnet 8c.

The DC electromagnets 8a, 8 symmetrically arranged in this way
By controlling the gap lengths xa and xc of c as described above, the rotating body 6 can always be held at the center position.
In addition, in the description of the control circuit above, the sawtooth wave oscillator 19
The maximum waveform level was set to zero, but in this method, the damping characteristics are poor because the air gap length xa≠xc and the current flows only through the DC electromagnet with the larger air gap length. In this case, the damping characteristic can be improved by making the maximum waveform level of the oscillator 19 greater than zero and supplying equal current to the DC electromagnets 8a and 8c even when xa=xc.

Further, FIG. 11 shows another embodiment of the present invention.
In FIG. 11, 1a, 1b, and 1c indicate three levitation DC electromagnets arranged at equal intervals and with the same polarity.
The cores of the DC electromagnets 1a, 1b, and 1c are integrally processed to form a U-shaped core in which only the outer pole (N pole) is divided into three parts. Therefore, the windings of the electromagnets are wound around the outer iron core, and each DC electromagnet 1a, 1b, 1c
Only one 3A ring plate is required for the short-circuiting of the iron core end. By adopting the above structure, the same effect as shown in FIG. 4 can be obtained, and the structure of the levitation DC electromagnet can be made simple and robust.

As explained above, according to the present invention, by short-circuiting each core end of the levitation DC electromagnet with a ring plate, it is possible to reduce the eddy current loss generated in the secondary core as it rotates. You can get a flyhotol magnetic bearing device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the arrangement of a conventional DC electromagnet, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a diagram showing its magnetic flux distribution, FIG. 4 is a diagram showing the arrangement of a DC electromagnet in the present invention, and FIG. Figure 6 is a cross-sectional view of the same, Figure 6 is a diagram showing its magnetic flux distribution, Figure 7 is a cross-sectional view of an example of a flywheel device to which the present invention is applied, and Figure 8 is a guiding DC electromagnet and a displacement meter in the present invention. 9 and 10 are diagrams showing the gap length control circuit for floating support and guide support, respectively.
This figure shows the arrangement of levitation DC electromagnets in another embodiment of the present invention, and FIG. 12 is a sectional view thereof. 1, 1a, 1b, 1c... levitation DC electromagnet,
3a, 3b...Ring plate, 6...Rotating body, 7, 9
...Displacement meter, 8...Direct current electromagnet for guidance, 10...
Rotor, 11...armature winding, 12...rotating shaft.

Claims (1)

[Claims] 1. In a flywheel magnetic bearing device in which a flywheel is suspended and supported around a rotating shaft by a plurality of levitation electromagnets and guide electromagnets, the N and S poles of the levitation electromagnets are located on concentric circles, respectively. 1. A magnetic bearing device for a flywheel, characterized in that at least one of the north pole and the south pole is connected by a ring plate of a polar body.