JPH0681965B2 - Thrust magnetic bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] A turbo molecular pump used in an LSI manufacturing process that avoids the use of lubricating oil, or a turbocharger that does not require a lubricating oil refueling device by being used in combination with a dry gas seal. The present invention relates to a thrust magnetic bearing used to support a rotating shaft in a compressor or the like.

[Prior Art] Such a conventional thrust magnetic bearing is shown in FIGS. 5 and 6.

5 and 6, a thrust magnetic bearing generally designated by reference numeral 10 comprises a rotary shaft 1, a disk-shaped thrust disk 2 made of a magnetic material fixed to the rotary shaft 1, and the thrust disk 2
And a cylindrical stationary yoke 3 facing each other with a minute gap therebetween.

The cylindrical stationary yoke 3 is fixed to a casing (not shown) and has a U-shaped cross section. A cylindrical exciting coil 5 is inserted in the U-shaped cross section.

In this thrust magnetic bearing 10, the displacement of the shaft in the thrust direction is measured by the displacement sensor 11. The output of the displacement sensor 11 is sent to the compensation circuit 12, and the output of the compensation circuit 12 excites the coil 5 via the power amplifier 14 to generate a magnetic attraction force. This controls the axial position of the rotary shaft 1 to a predetermined position.

[Problems to be Solved by the Invention] However, in the conventional thrust magnetic bearing 10, since the cylindrical stationary yoke 3 is integrally formed, it is fixed to the rotary shaft 1 when the rotary shaft 1 is assembled or disassembled. The disk-shaped thrust disk 2 made of magnetic material must be removed from the rotary shaft 1. Therefore, the thrust disc 2 and the rotary shaft 1 must be fitted in a clearance fit, and as a result, vibration may occur when the rotary shaft 1 is rotated at a high speed.

Such vibration not only causes noise, but also causes fatigue damage and malfunction of the machine, and the occurrence of such vibration must be avoided as much as possible. However, in the prior art, vibration has occurred due to the above-mentioned reasons, and no effective means for preventing it has been proposed.

The present invention has been proposed in view of the above-mentioned problems of the conventional art, and an object thereof is to provide a thrust magnetic bearing capable of effectively preventing the above-described vibration.

[Means for Solving the Problem] A thrust magnetic bearing of the present invention is fixed to a rotor (thrust disk) made of a magnetic material in a disk shape fixed to a rotating shaft and a casing facing the rotor with a minute gap provided therebetween. And a stationary yoke having a cylindrical shape as a whole, and the stationary yoke has a structure in which it is divided into two in a circumferential direction, and has a plurality of cores for inserting an exciting coil and has a II-shaped shape as a whole. II-shaped yokes, an even number of exciting coils inserted in the core of the II-shaped yokes, and the II-shaped yokes and the exciting coils are divided into two in the circumferential direction so as to surround them in a U-shape. It includes a U-shaped yoke with a structure that

Further, in addition to such a constitution, the thrust magnetic bearing of the present invention has four cores and exciting coils as a whole, and includes a first displacement sensor for detecting axial displacement of the rotating shaft, and A first control circuit for exciting the exciting coil so that the rotary shaft is held at a predetermined axial position in response to the output of the first displacement sensor; and a second displacement sensor for detecting axial vibration of the rotary shaft. And a second control circuit for controlling the shaft vibration to be zero based on the output of the second displacement sensor.

[Operation] According to the thrust magnetic bearing of the present invention having the above-described structure, the cylindrical stationary yoke having a U-shaped cross section, which is arranged facing each other with a minute gap provided in the thrust disk, is arranged in the circumferential direction. The split yoke is divided into two, so that the stationary yoke is divided into two in the circumferential direction. As a result, when assembling and disassembling the rotary shaft, the rotary shaft can be removed while the thrust disk is fixed by dividing the stationary yoke into two parts.

Accordingly, it is not necessary to remove the disk-shaped thrust disk made of a magnetic material from the rotary shaft, so that it is not necessary to fit the thrust disk to the rotary shaft with a clearance. Therefore, it was possible to solve the problem in the prior art that vibration occurs at high speed because the thrust disk is fitted into the rotary shaft with a clearance.

When assembling the thrust magnetic bearing of the present invention, the II-shaped yoke having a plurality of cores into which the exciting coil is inserted may be inserted and fixed from the opening of the U-shaped yoke. As a result, a closed magnetic path can be formed between the thrust disk, the II-shaped yoke, and the U-shaped yoke, and the stationary yoke section is a split type, so disassembly and assembly are extremely easy. Be seen.

Further, according to the thrust magnetic bearing of the present invention, from the second displacement sensor that detects the conical mode motion of the rotating shaft,
In response to the output signal of the displacement sensor, the four exciting coils inserted in the II-shaped yoke divided into two each having two exciting coil cores generate a couple in the exciting coils facing each other. To generate two control signals of opposite phase amplitude. On the other hand, in response to the output signal of the first displacement sensor, a thrust control signal created so as to hold the rotary shaft at an appropriate axial position is created. Then, the two control signals of the antiphase amplitude and the thrust control signal are added and output to the four exciting coils.

As a result, in addition to the force in the thrust direction that controls the axial position of the rotary shaft, a couple force that controls the vibration of the rotary shaft in the conical mode is generated, and the vibration of the rotary shaft in the conical mode can be reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

In FIG. 1 and FIG. 2, a thrust magnetic bearing, generally designated by reference numeral 100, is the first embodiment of the present invention, and the rotary shaft 101
And a disk-shaped thrust disk 102 made of a magnetic material fixed to the rotating shaft, and a stationary yoke arranged to face the thrust disk with a minute gap therebetween. This stationary yoke is fixed to a casing (not shown), is divided into two in the circumferential direction (upper and lower in FIG. 2), and has a U-shaped cross section.

The stationary yokes here are U-shaped yokes 103 and II-shaped yokes 104.
And an exciting coil 105. II-shaped yoke 1
04 has a plurality of cores into which the exciting coil 105 is inserted. The U-shaped yoke 103 has a structure in which it is divided into two in the circumferential direction (upper and lower in FIG. 2).

When assembling the thrust magnetic bearing 100, a plurality of (two in FIG. 2) exciting coils 105 (105a, 105b) are provided for each of the II-shaped yokes 104 (104a, 104b in FIG. 2). insert.
Then, the II-shaped yoke 104 into which the exciting coil 105 is inserted is inserted into each of the U-shaped yokes 103 (103) through the openings 106 (106a, 106b).
a, 103b) and fixed integrally with the U-shaped yoke by a fixing means (nut 107 in FIG. 1).

As a result, the excitation coil 105 causes the thrust disk 10 to
2. A closed magnetic path is generated in the II-shaped yoke 104 and the U-shaped yoke 103.

During operation, vibration or displacement in the thrust direction of the rotary shaft 101 is detected by a displacement sensor (first displacement sensor) 111, an output signal is sent to a compensation circuit 112, and the output from the compensation circuit 112 is passed through a power amplifier 114. Sent to the coil 105. Compensation circuit 11 sent to exciting coil 105 via power amplifier 114
The output from 2 is the thrust disk 1 when the coil is excited.
A magnetic attraction force is generated between the rotating shaft 101 and the shaft 02 to hold the axial position of the rotating shaft 101 at a predetermined position. This controls the thrust direction.

Next, a second embodiment of the present invention will be described with reference to FIGS.

The thrust magnetic bearing, which is entirely denoted by reference numeral 200, has the same structure as the thrust magnetic bearing 100 shown in FIGS. 1 and 2, but in addition to that, a second type that detects axial vibration of the rotating shaft 201 is used. Displacement sensors 221a and 221b, a calculation circuit 222 that calculates the rotation angle of vibration from the output signal, and a phase compensation circuit 2
23, and an adder 213 that adds the output thereof and the output signal from the first displacement sensor 211.

In the second embodiment, even in the case of a so-called "conical mode" in which vibration occurs in the rotating shaft 201 and swirls in a conical shape,
It can function to cancel the vibration and eliminate the conical mode.

When the conical mode vibration control action of the rotating shaft is added to the split type thrust magnetic bearing, the rotation angle φ around the center of gravity of the conical mode (vibration rotation angle) is determined by the two radial displacement sensors 221a and 221b (first 2 displacement sensor).

The axial vibration at the position of the displacement sensor 221a is xa, and the displacement sensor
When the axial vibration at the position of 221b is xb, the distance between the displacement sensor 221a and the center of gravity G is la, and the distance between the displacement sensor 221b and the center of gravity G is lb, the rotation angle φ around the center of gravity in the conical mode is φ.
Is calculated by the following formula.

φ = (xa−xb) / (la + lb) The above operation is performed by the operation circuit 222, and the output signal is sent to the conical mode phase compensation circuit 223. Then, the output signal of the phase compensation circuit 223, that is, the phase-compensated signal and its inverted signal are output to the adder 213.

On the other hand, the vibration or displacement of the rotary shaft 201 in the thrust direction is detected by the displacement sensor 211 (first displacement sensor) and sent to the compensation circuit 212, and the output thereof is sent to the coil 105 via the power amplifier 214 and It is output to the adder 213. Then, in the adder 213, the phase compensation circuit 223
Output signal, that is, the phase-compensated signal and its inverted signal are added to the output of the compensation circuit 212 in the thrust direction, and are added via the power amplifier 214 to the coil 205 (205a, 20a in FIG. 4).
5c) is excited.

As a result, the coil 205 can generate a couple force that controls conical mode vibration at the same time as the magnetic attraction force that controls the thrust direction.

In addition, symbol S in FIG. 4 indicates a division surface of the U-shaped yoke 203.

[Advantages of the Invention] As described above, according to the thrust magnetic bearing of the present invention, the rotating shaft can be assembled and disassembled without removing the disk-shaped thrust disk made of a magnetic material fixed to the rotating shaft. . Therefore, there is no need to make a clearance fit between the thrust disc and the rotary shaft, and the vibration problem can be avoided at high speed rotation.

Further, the vibration of the rotary shaft in the conical mode can be controlled by using an exciting coil divided in the circumferential direction, a sensor (second displacement sensor) for detecting the vibration of the rotary shaft in the conical mode, or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is an end view showing both end faces of a U-shaped yoke used in the first embodiment, and FIG. 3 a second embodiment of the present invention. FIG. 4 is an end view showing the end face of the U-shaped yoke used in the second embodiment, FIG. 5 is a block diagram showing a conventional thrust magnetic bearing, and FIG. 6 is used in the prior art. It is an end view of the cylindrical stationary yoke. 1, 101, 210 ... Rotating shaft, 2, 102, 202 ... Thrust disk, 3, 103, 103a, 103b, 203 ... Cylindrical stationary yoke with U-shaped cross section, 4, 104, 104a, 104b, 204, 204a, 204
b, 204c, 204d ... II-shaped yoke divided in the circumferential direction, 5, 1
05, 105a, 105b, 205, 205a, 205b, 205c, 205d ... Excitation coil, 11, 111, 211 ... Thrust direction displacement sensor (first displacement sensor), 12, 112, 212 ... Thrust direction compensation circuit , 213 ... Adder circuit, 14, 114, 214 ... Power amplifier, 221a, 221b ... Radial displacement sensor (second displacement sensor), 222 ... Rotation angle calculation circuit, 223 ... Conical mode compensation circuit

Claims (2)

[Claims] 1. A stationary spigot comprising a disc-shaped magnetic material rotor fixed to a rotary shaft, and a stationary yoke fixed to opposing casings with a minute gap in the rotor and having a cylindrical shape as a whole. Iron has a structure in which it is divided into two in the circumferential direction, has a plurality of cores for inserting an exciting coil, and has a II-shaped overall, and a core of the II-shaped yoke. An even number of exciting coils inserted in the coil, the II-shaped yoke and a U-shaped yoke that surrounds the exciting coil in a U shape and is divided into two in the circumferential direction. A thrust magnetic bearing characterized in that the coil is wound around each of the portions corresponding to the II-shaped legs. 2. A first displacement sensor having a total of four cores and an exciting coil for detecting axial displacement of the rotary shaft, and a rotary shaft in response to an output of the first displacement sensor. Based on an output of the second control sensor, a first control circuit for exciting and exciting the exciting coil so that the motor is held at a predetermined axial position, a second displacement sensor for detecting axial vibration of the rotating shaft, and an output of the second displacement sensor. And a second control circuit for controlling the shaft vibration so that the shaft vibration becomes zero.