JP3576397B2 - Energization control method of magnetic bearing used for high-speed rotating body and its control circuit - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is characterized in that the pair of magnetic bearings disposed at symmetric positions with respect to a rotating shaft connected to a load or a magnetic member (hereinafter, referred to as a rotating shaft portion) that rotates integrally with the rotating shaft are controlled by energizing the pair. The present invention relates to an energization control method and a control circuit for a magnetic bearing of a high-speed rotating body such as a turbo molecular pump that rotates the rotating shaft at a high speed while maintaining the rotating shaft in the air. The present invention relates to a method for controlling energization of a magnetic bearing used in a turbo-molecular pump provided with a moving and stationary blade stage composed of a stationary blade provided in a rotating shaft and a moving blade provided on a rotating shaft, and a control circuit therefor.
[0002]
[Prior art]
Conventionally, instead of a mechanical bearing that mechanically supports a rotating body or a linear moving body such as a ball bearing or a rolling bearing, a magnetic bearing that supports the rotating body or the linear moving body by magnetic force is known. .
Such a magnetic bearing has a smaller loss than a conventional fluid lubricated bearing, and can achieve a dry bearing and a clean atmosphere. Especially, since it is a useful bearing in a vacuum state, it can be operated at high speed by a direct-coupled motor such as a turbo molecular pump. The driven high-speed rotating body is frequently used as a bearing for a rotating unit.
FIG. 4 shows the configuration of a turbo-molecular pump having such a magnetic bearing.
[0003]
FIG. 4 shows an example of a turbo-molecular pump applied to the present invention. In FIG. 4 (A), reference numerals 1 and 16 denote an upper casing and an upper casing which are integrally assembled via bolts 21 via an O-ring 15. The lower casing.
The upper opening of the upper casing 1 serves as a gas inlet port 2, and a plurality of spacers 13 are provided in the inside thereof in the axial direction through a ring-shaped gap.
The upper end of the spacer 13 is abutted against the inner end surface of the upper casing 1, and the lower end is spigot-fitted to the upper end of the lower casing 16. It is sandwiched and fixed and provided in a multi-stage shape.
[0004]
Reference numeral 6 denotes a rotor, and the rotor 6 is provided with a plurality of moving blades 5 in a multi-stage manner, and each of the moving blades 5 and the stationary blades 4 are provided so as to alternately mesh with each other to form a blade stage. At the lower part of the rotor 6, a thread groove pump stage 8 is provided.
Reference numeral 14 denotes a tapered seal ring fixed to the upper surface of the lower casing 16 by a plurality of bolts 18, and is disposed to face the outer periphery of the thread groove pump stage 8 via a small gap, thereby increasing the compression effect.
[0005]
An exhaust port 3 is opened at a lower side portion of the lower casing 16, and the fluid that has passed through the screw groove pump stage 8 is sent out from the exhaust port 3 to the outside.
Reference numeral 17 denotes a cylindrical support cylinder projecting upward in the center region of the lower casing 16, and an upper protection bearing 19 composed of a radial ball bearing and a radial bearing on the inner periphery of the support cylinder 17 in order from the top. An upper magnetic bearing 9, a stator portion 12a of a motor 12, a lower magnetic bearing 10 as a radial bearing, a lower protection bearing 20 made of a radial ball bearing, and a thrust provided with a thrust disk 7a at a lower end of the rotating shaft 7 described later interposed therebetween. A magnetic bearing 11 is provided.
[0006]
Reference numeral 7 denotes a rotating shaft fixed to the center of the upper portion of the rotor 6. The rotating shaft 7 hangs in an axial direction from a fixed portion to the rotor 6, and sequentially from an upper portion to an upper magnetic bearing 9 and a lower magnetic bearing 10. A radial load is supported, and a thrust disk 7a formed of a disk-shaped magnetic plate provided at the lower end is sandwiched between the thrust magnetic bearings 11 to perform airborne maintenance control in the thrust direction (axial direction).
[0007]
A rotor 12 b is fixed to the rotating shaft 7 so as to face a stator 12 a of the motor 12 provided between the upper magnetic bearing 9 and the lower magnetic bearing 10.
[0008]
The upper protection bearing 19 is provided above the upper magnetic bearing 9 of the rotating shaft 7, and a radial distance between the rotating shaft 7 and the upper protection bearing 19 is set to a required value.
Further, the lower protective bearing 20 is provided below the lower magnetic bearing 10 of the rotary shaft 7, and the radial and thrust intervals between the rotary shaft 7 and the lower protective bearing 20 are set to required values. ing.
[0009]
Next, as shown in FIG. 4B, the magnetic poles of the upper magnetic bearing 9 and the lower magnetic bearing 10 are moved right and left (X-axis) and front-back ( Each pair is arranged in the (Y-axis) direction so that the rotary shaft 7 can be maintained in the air on the center axis line without falling down.
Therefore, the rotating shaft 7 is moved in the left-right (X-axis) and front-rear (Y-axis) directions by the upper magnetic bearing 9 and the lower magnetic bearing 10, and is moved in the axial center (Z-axis) direction by the thrust magnetic bearing 11, that is, 5. The axial direction is supported in the air, and the rotation is controlled.
[0010]
During the operation of the turbo molecular pump A configured as described above,
The motor 12 is driven in a state in which the magnetic bearings 9, 10, and 11 are energized and a pump rotating unit such as the rotor 6 having the rotating shaft 7 and the moving blade 5 is maintained in the air, and the pump rotating unit is moved to, for example, 10,000. ~ 100,000 r. p. Rotate at high speed at m. The rotor 5 rotates between the stationary blades 4 due to the high-speed rotation of the pump rotating unit, and the thread groove pump stage 8 rotates while facing the inner peripheral surface of the tapered seal ring 14, thereby evacuating. After the first stage of compression is performed between the moving blades 5 and the stationary blades 4 from the upper gas inlet 2 through the upper gas inlet 2, a second stage of compression is performed in the spiral groove passage of the thread groove pump stage 8, By flowing in the direction of the exhaust port 3 through the internal gas passage, the gas intake port 2 side is maintained at a high vacuum.
[0011]
When the magnetic control of the upper / lower magnetic bearings 9 and 10 and the thrust magnetic bearing 11 becomes abnormal and the rotary shaft 7 is eccentric to one side, the upper protective bearing 19 and the lower protective bearing 20 When the outer periphery of the shaft 7 abuts (touch-down), the rotation of the rotating shaft 7 and the rotor 6 is guaranteed.
[0012]
The power supply unit attached to such a turbo molecular pump has a configuration as shown in FIG.
FIG. 3 shows a main block configuration of a turbo molecular pump unit A and a power supply unit B to which the present invention is applied. On the pump unit A side, as described above, the rotor 6 and the rotary shaft 7 directly connected to the rotor 6 (hereinafter referred to as these). ), And magnetic sensors 9, 10, 11 for controlling the levitation of the rotating bodies, and position sensors 24, 25, 26 for detecting the gaps between the magnetic bearings 9, 10, 11 and the rotating bodies.
[0013]
On the other hand, a motor drive circuit 34 (for example, a power supply circuit including an inverter circuit) for driving the motor 12 directly connected to the rotary shaft 7 of the pump unit A at a high speed is incorporated in the power supply unit B, and controls the rotation of the motor 12. Do.
On the other hand, the control on the magnetic bearing side is such that the upper magnetic bearing 9 receives a signal from the position sensor 24 near the upper magnetic bearing 9 and the lower magnetic bearing 10 receives a signal from the position sensor 25 near the lower magnetic bearing 10. Accordingly, the thrust magnetic bearing 11 is further controlled by independent control means in response to a signal from the position sensor 26 near the thrust magnetic bearing 11.
[0014]
An example of this will be described with the control of the upper magnetic bearing 9 as a representative. The control means receives a signal from the position sensor 24 and holds the center of the floating position of the rotary shaft 7 in the radial direction based on the deviation amount. A magnetic bearing control circuit 32 for sending a control signal to be controlled, and a magnetic bearing drive for controlling the drive of the upper magnetic bearing 9 while controlling the switching element to be ON / OFF based on a pulse signal pulse width modulated based on the control signal. A circuit 33 and a magnetic bearing drive power supply 31 are incorporated.
[0015]
Then, as disclosed in, for example, Utility Model Registration No. 2522168, the magnetic bearing control circuit 32 detects the detection signal from the position sensor 24 with its reference position via a position feedback gain (not shown) such as a deviation amplifier. After being converted into a deviation signal, the signal is taken into a low-pass notch filter, and the low-pass notch filter blocks an unstable portion such as noise in a middle and high frequency band over a wide range.
The feedback signal after passing through the low-pass notch filter passes through a PID control circuit, which is a proportional element, an integral element, and a differential element, and then a phase compensation circuit for stabilizing a natural frequency of several orders due to the structure of the rotating shaft 7. To obtain the control current.
[0016]
The position sensors 24 #, 24Y and the magnetic bearing control circuits 32 #, 32Y are provided for each coordinate axis (Χ, Y) as shown in FIG. 4, while the magnetic poles of the magnetic bearing 9 are also provided for each coordinate axis (Χ, Y). Each pair is provided at a position facing each other with the rotating shaft 7 interposed therebetween.
That is, since one magnetic pole for each coordinate axis (Χ, Y) and the opposite magnetic pole located on the opposite side with respect to the rotation axis 7 have a deviation amount from the reference position in forward and reverse symmetry, each of the coordinate axes (Χ, Y) The control signals of the magnetic bearing control circuits 32 # and 32Y for each Y) may be transmitted to the magnetic bearing drive control circuit 33 as it is for one magnetic pole or inverted for the opposite magnetic pole.
[0017]
[Problems to be solved by the invention]
Since the turbo molecular pump rotates at a high speed, the magnetic bearing drive control circuit 33 is required to have a high-speed response in order to stably rotate the pump.
For this reason, a variable resistance type transistor is used as the switching element of the magnetic bearing drive control circuit 33. However, since such a switching element generates a large amount of heat due to resistance loss, a heat radiating means such as a heat sink must be provided. And the circuit configuration becomes large.
Therefore, an FET transistor is used as the switching element, and a pulse width modulation signal modulated in accordance with a control signal or an inversion control signal of the magnetic bearing control circuits 32 # and 32Y is applied to the base side of the transistor to perform the switching. The energization control is performed by ON / OFF controlling the elements.
[0018]
The magnetic bearing drive control circuit 33 will be described with reference to FIG. 2 for the upper magnetic bearing 9. Position sensors 24 Χ, 24 Y and magnetic bearing control circuits 32 Χ, 32 Y are provided for each coordinate axis (Χ, Y). The control signals of the bearing control circuits 32 # and 32Y are inverted as they are or by an inversion circuit 41, respectively, and the control signal or the inversion control signal is further supplied with the bias superimposition control signal generated in the bias circuit 49 by the pulse width modulation circuit 42 of each magnetic pole. , And a modulation pulse corresponding to the control signal or the inversion control signal is connected to each of the coordinate axes (極, Y). The FET transistors of the switching elements 43YL, 43YR,. 44, and is connected to the DC power supply 31 through the switching elements 43YL, 43YR,. ON / OFF energization control of the magnetic pole coils 9YL, 9YR,... In the figure, reference numeral 46 denotes a backflow prevention diode. The downstream side of the switching elements 43YL, 43YR... Comprises an FET transistor 44 and a diode 45, and the downstream side is grounded.
[0019]
Since the FET transistors 44 are used for the switching elements 43YL, 43YR,..., The heat resistance loss is small, and there is no need to provide a heat radiating means such as a heat sink. As described in detail later, there is a disadvantage in that the response is reduced, and particularly high-speed response in a high-speed rotating body such as a turbo pump cannot be ensured.
For this reason, in the magnetic bearing drive control circuit 33 shown in FIG. 2, a method of increasing the applied voltage of the DC power supply 31 (magnetic bearing drive power supply 31) or adding a commutation resistance is used.
[0020]
However, in the former method, the power supply capacity is increased, which leads to an increase in size and cost. Also, in the latter method, the resistance loss increases, and a large capacity of the resistor and a cooling measure such as a heat sink are required, resulting in an increase in size.
[0021]
In view of the above technical problems, the present invention provides an energization control method and a control method for a magnetic bearing of a high-speed rotating body such as a turbo-molecular pump, which can ensure high-speed response effectively without requiring cooling measures such as a heat sink. It is intended to provide a circuit.
Another object of the present invention is to provide an energization control method capable of ensuring a high-speed response while simplifying a circuit configuration, and a control circuit therefor.
[0022]
[Means for Solving the Problems]
In order to solve such a problem, the invention according to claim 1 is arranged such that a rotating shaft connected to a load or a magnetic member that rotates integrally with the rotating shaft (hereinafter, referred to as a rotating shaft portion) is symmetrically positioned. In the energization control method of the magnetic bearing used for the high-speed rotating body that rotates the rotation shaft portion at high speed while maintaining the rotation shaft portion in the air by energization control of the magnetic bearing for each pair arranged,
Controlling the current flowing through the electromagnet pole coils 9YL, 9YR,... Constituting the magnetic bearing according to the air gap fluctuation between the rotating shaft portion and the magnetic bearing is controlled by ON / OFF pulses applied to the switching elements 43YL, 43YR,. .., And transfers the current energy of the respective magnetic pole coils 9YL, 9YR,... To the other magnetic pole coil (hereinafter referred to as the opposite magnetic pole) at the position opposite to the rotating shaft every time the pulse to the one magnetic pole coil is turned off. It is characterized by flowing.
[0023]
The ON / OFF pulses applied to the switching elements 43YL, 43YR... May be not only pulse width modulation pulses (PMW) but also frequency modulation pulses.
[0024]
According to this invention, of the pair of magnetic pole coils 9YL, 9YR,... Arranged symmetrically with respect to the rotating shaft portion, one of the magnetic pole coils 9 # R, 9YR allows a direct current to flow from the DC power supply 31 when the pulse is ON. On the other hand, when the pulse to the one magnetic pole coil 9 # R, 9YR is turned off, the diode 46 is connected to the one magnetic pole coil 9 # R, 9YR to the opposite magnetic pole coil 9 # L, 9YL, so that the energy of the one magnetic pole coil 9 # R, 9YR is reduced. The current can flow to the opposed magnetic pole coils 9 # L and 9YL.
As a result, the energy when the pulse of one magnetic pole coil 9 # R, 9YL is turned off can be supplied to the opposed magnetic pole coils 9 # L, 9YL side, and can be quickly consumed. Next, the energy when the pulse of the opposite magnetic pole coils 9 # L, 9YL is turned off is also reduced. It can be supplied to one magnetic pole coil 9 # R, 9YR side and consumed quickly.
[0025]
Therefore, the pair of magnetic pole coils 9YL, 9YR,... Arranged symmetrically with respect to the rotary shaft portion can supply energy to the other magnetic pole coil side every time the pulse is turned off and quickly consume the energy. High-speed responsiveness can be effectively secured without any occurrence and without requiring a cooling measure such as a heat sink.
[0026]
According to a third aspect of the present invention, there is provided an invention relating to a circuit configuration for effectively implementing the first aspect of the present invention.
A first control circuit 33A for controlling a current supplied to the electromagnet pole coils 9YL, 9YR,... Constituting the magnetic bearing in accordance with a gap variation between the rotating shaft portion and the magnetic bearing; The circuit 33A controls ON / OFF of the switching elements 43YL, 43YR,... Connected to the respective magnetic pole coils 9YL, 9YR,... By applying a pulse controlled according to the air gap variation, and at the same time, the switching elements 43YL, 43YR,. A pair of magnetic pole coils 9YL, 9YR,... Located at a position opposing the rotating shaft portion on the upstream side of the motor are connected to each other, and the current energy of the magnetic pole coils 9YL, 9YR,. Each time, it is commutated to the other-side magnetic pole coils 9 # L and 9YL located at opposing positions.
[0027]
In this case, an energizing system of a bias current flowing through each of the magnetic pole coils 9YL, 9YR... In order to increase the static rigidity of each of the magnetic bearings is provided separately from the energizing system of the first aspect. Good to do.
[0028]
For example, the upper magnetic bearing requires a total of four magnetic poles 9YL, 9YR..., One pair for each of the Χ-Y coordinate axes, and conventionally, a bias current must be applied to each of the magnetic poles 9YL, 9YR. Therefore, like the rotary shaft 7 of the turbopump, the upper magnetic bearing 9 and the lower magnetic bearing 10 respectively make a pair in the left-right (X-axis) and front-rear (Y-axis) directions. In a device having a pair of magnetic poles in the (Z-axis) direction and performing aerial support with so-called five axes, ten bias circuits are provided by the number of magnetic poles, or as shown in FIG. When the control signal or the inversion control signal from the circuit 32 is supplied to the pulse width modulation circuit 42, the bias signal generated by the bias circuit 49 is superimposed on the control signal, and the bias is superimposed. When the control signal or the inversion control signal is applied to the pulse width modulation circuit 42 for controlling the magnetic poles, current flows simultaneously in two opposing magnetic poles (for example, 9XR and 9XL), and the air support by the control signal or the inversion control signal is performed. High-precision magnetic bearing control cannot be performed for current control.
In addition, when current flows at the same time, current cannot be commutated to the other electrode, and responsiveness cannot be improved.
[0029]
On the other hand, according to the present invention, since the inductance and resistance of the magnetic pole coils 9YL, 9YR... In each of the upper magnetic bearing 9 and the lower magnetic bearing 10 and the thrust magnetic bearing 11 are the same, a bias power supply is provided for each magnetic bearing. And the bias current supply system is made different from the current supply system of claim 1, so that one circuit is provided for each magnetic bearing of the upper magnetic bearing 9 and the lower magnetic bearing 10 and the thrust magnetic bearing 11 for a total of three circuits. A bias circuit is sufficient.
In addition, the bias current supply system is different from the current supply system of the first aspect, so that the application of the bias current and the control of the supply current according to the air gap variation between the rotating shaft and the magnetic bearing are independently performed with high precision. , And high-precision magnetic bearing control becomes possible.
[0030]
According to a fourth aspect of the present invention, there is provided the first control circuit 33A according to the third aspect ,
A second control circuit 33B for supplying a bias current to each of the magnetic pole coils 9YL, 9YR,... In order to increase the static rigidity of each of the magnetic bearings.
The two control circuits are configured to be capable of applying current to the magnetic pole coils 9YL, 9YR,.
[0031]
A fifth aspect of the present invention is an embodiment of the fourth aspect of the present invention. In order to control the position of the rotating shaft in two radial axes (Χ axis, Y axis), the rotating shaft is opposed to the rotating shaft. One or more radial magnetic bearings comprising at least two pairs of magnetic pole coils 9YL, 9YR ...
In order to control the position of the coordinate axis (Z axis) in the thrust direction of the rotating shaft, a thrust magnetic bearing having at least one pair of magnetic pole coils 9YL, 9YR... In the energization control circuit,
A plurality of magnetic pole coils 9YL, 9YR... In the radial magnetic bearing or the thrust magnetic bearing can be applied with a bias current by a single bias current supply circuit (second control circuit 33B) common to each corresponding magnetic bearing. It is characterized by comprising.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely examples. Only.
[0033]
FIG. 1 is a block diagram showing a magnetic bearing control circuit 33 of the upper magnetic bearing 9 according to the embodiment of the present invention, which corresponds to FIG.
That is, also in this embodiment, similarly to FIG. 2, the position sensors 24 #, 24Y and the magnetic bearing control circuits 32 #, 32Y are provided for each coordinate axis (#, Y), and the control signals of the respective magnetic bearing control circuits 32 #, 32Y are provided. Is supplied to the pulse width modulation circuit 42 of each magnetic pole, and a modulation pulse corresponding to the control signal or the inversion control signal is provided as it is or inverted by the inversion circuit 41 to provide one pair for each coordinate axis (Χ, Y). Are applied to the bases of the FET transistors 44 of the switching elements 43YL, 43YR,... Of the magnetic poles, and the respective magnetic pole coils 9YL, 9YL, which are directly or indirectly connected to the DC power supply 31 through the switching elements 43YL, 43YR,. 9YR... ON / OFF energization control is performed.
[0034]
More specifically, the DC power supply 31 is connected via a diode 47 to the anode (upstream) side of one of the pair of magnetic pole coils 9YL, 9YR,. The switching elements 43 # R and 43YR provided on the downstream side of the magnetic pole coils 9 # R and 9YR are connected, and branching is performed on the upstream side of the switching elements 43 # R and 43YR, and the rotary shaft 7 is sandwiched between the branch lines via the backflow prevention diode 46. Is connected to the anode side of the opposing magnetic pole coils 9 # L and 9YL at the symmetrical positions, and the switching of the corresponding magnetic pole provided on the downstream side is performed every time the switching elements 43 # R and 43YR to the one magnetic pole coil 9 # R and 9YR are turned off. Each time the elements 43 # L and 43YL are turned on, the current energy of one magnetic pole coil 9 # R and 9YR is transferred to the opposite magnetic pole coil 9 # L, It is configured so as to commutated to YL.
[0035]
On the other hand, similarly, the opposite magnetic pole coils 9 # L and 9YL located symmetrically with respect to the rotary shaft 7 similarly have a backflow prevention diode 46 upstream of the switching elements 43 # L and 43YL for controlling ON / OFF energization of the magnetic pole coils 9 # L and 9YL. And connected to the one magnetic pole coil 9 # R, 9YR at the symmetrical position, and the current energy of the opposing magnetic pole coil 9 # L, 9YL is reduced by one for each OFF of the switching element 43 # L, 43YL of the opposite magnetic pole as described above. It is configured to commutate to the magnetic pole coils 9 # R and 9YR.
[0036]
On the other hand, in order to increase the static rigidity of the magnetic bearing 9, a bias drive control circuit 33B for supplying a bias current to each of the magnetic pole coils 9YL, 9YR,... , The current can be applied to the magnetic pole coils 9YL, 9YR,... In a different system from the first drive control circuit 33A that controls the current supplied to the magnetic pole coils 9YL, 9YR,.
[0037]
The bias drive control circuit 33B sets the DC power supply 31 of the first drive control circuit 33A to a bias DC power supply by using a voltage converter (a device capable of insulating the primary side and the secondary side) 52, and then switches the power supply 52. After being sequentially connected to the respective magnetic pole coils 9YL, 9YR,..., They are connected via a diode 48 to a bias switching element 53 composed of an FET transistor 54 and a diode 55.
A bias control signal pulse-width-modulated by a pulse width modulation circuit 51 is applied to the base side of the FET transistor 54, thereby controlling the respective magnetic pole coils 9YL, 9YR,. The bias current is superimposed on the control current of the first drive control circuit 33A, and the current is supplied. Incidentally, 50 is a bias circuit.
[0038]
According to this embodiment, a pair of magnetic pole coils 9YL, 9YR,... Arranged symmetrically with respect to the rotating shaft portion, and a switching element 43YL, 43YR. The pulse width modulation signal is applied to the magnetic pole coils 9YL, 9YR,... Of the pair of magnetic pole coils 9ΧR, 9YR. When the switching elements 43 # R and 43YR are turned on by the modulation signal, a current is supplied from the DC power supply 31 to one of the magnetic pole coils 9 # R and 9YR via the diode 47.
[0039]
On the other hand, the opposing magnetic pole coils 9 # L and 9YL are connected to the one magnetic pole coils 9 # R and 9YR at symmetrical positions via the backflow prevention diode 46 on the upstream side of the corresponding switching elements 43 # L and 43YL. When the corresponding switching elements 43YL, 43YR... Are turned on by the modulation signal in a state where a bias current is applied to the magnetic pole coils 9 # L and 9YL by the bias drive control circuit 33B, in other words, the one magnetic pole coil 9 # R and 9YR When the pulse is turned off, the electric energy of one of the magnetic pole coils 9 # R and 9YL is consumed, and the DC power supply 31 is supplied to the opposing magnetic pole coils 9 # L and 9YL to energize the opposing magnetic pole coils 9 # L and 9YL.
[0040]
Therefore, according to this embodiment, the pair of magnetic pole coils 9YL, 9YR,... Arranged symmetrically with respect to the rotary shaft portion, each time the pulse is turned off, changes the current energy of the one magnetic pole coil 9 # R, 9Y to the opposite magnetic pole coil 9 # L, Since the current is supplied to the 9YL side and the power supply control can be performed while quickly consuming the power, the high-speed response can be effectively secured without generating a resistance loss and without requiring a cooling measure such as a heat sink.
[0041]
Since the inductances and resistances of the magnetic pole coils 9YL, 9YR,... In the upper magnetic bearing 9 are the same, a common bias power supply is used, and a bias current supply system is provided as a separate system. One system is sufficient for the bias drive control circuit 33.
[0042]
【The invention's effect】
As described above, according to the first and third aspects of the present invention, in a magnetic bearing of a high-speed rotating body such as a turbo molecular pump, high-speed responsiveness can be effectively secured without requiring a cooling measure such as a heat sink.
[0043]
According to the second and fourth aspects of the invention, high-speed response can be ensured while simplifying the circuit configuration. In addition, the bias current supply system is different from the current supply system of the first aspect, so that the application of the bias current and the control of the supply current according to the air gap variation between the rotating shaft and the magnetic bearing are independently performed with high precision. , And high-precision magnetic bearing control becomes possible.
[0044]
According to the fifth aspect of the present invention, in order to perform position control of two coordinate axes (Χ axis, Y axis) in the radial direction of the rotating shaft, the radial magnetic bearing including an upper bearing and a lower magnetic bearing; And a thrust magnetic bearing for controlling the position of the coordinate axis (Z-axis) in the thrust direction.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a correspondence diagram similar to FIG. 2 in a magnetic bearing control circuit of an upper magnetic bearing according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a magnetic bearing control circuit of an upper magnetic bearing according to the related art.
FIG. 3 is a block diagram showing a main block configuration of a pump unit A and a power supply unit B of a turbo molecular pump to which the present invention is applied.
FIG. 4 is an overall sectional view of a turbo-molecular pump to which the present invention is applied.
[Explanation of symbols]
A Pump body B Power supply unit 5 Rotor blade 7 Rotating shaft 9 Upper magnetic bearings 9YL, 9YR ... Magnetic pole coil 10 Lower magnetic bearing 11 Thrust magnetic bearings 24 #, 24Y Position sensor 31 Magnetic bearing drive power supply 32 #, 32Y Magnetic bearing control circuit 33A First Driving control circuit 33B Bias driving control circuit (second driving control circuit)
41 Inversion circuit 42 Pulse width modulation circuit 43YL, 43YR ... Magnetic pole switching element 44 FET transistor 46 Backflow prevention diode 52 Voltage converter (bias DC power supply)
53 Switching element for bias

Claims (5)

The rotating shaft portion is controlled by energizing each pair of magnetic bearings disposed at symmetric positions with a rotating shaft connected to a load or a magnetic member (hereinafter, referred to as a rotating shaft portion) rotating integrally with the rotating shaft interposed therebetween. In a high-speed rotating body that rotates the rotating shaft at a high speed while maintaining in the air,
In accordance with a variation in the air gap between the rotating shaft portion and the magnetic bearing, the control of the current supplied to the electromagnet magnetic pole coil constituting the magnetic bearing is performed by ON / OFF pulses applied to the switching element, and the respective magnetic poles are controlled. Energizing a magnetic bearing used for a high-speed rotating body, wherein the current energy of the coil is commutated to the other magnetic pole coil at a position facing the rotating shaft portion every time the pulse to the one magnetic pole coil is turned off. Control method. 2. The magnetic bearing control method according to claim 1, wherein an energizing system of a bias current flowing through each magnetic pole coil is provided separately from the energizing system of claim 1 in order to increase the static rigidity of each magnetic bearing. . A high-speed rotating body that rotates the rotary shaft at a high speed while maintaining the rotary shaft in the air by energizing the magnetic bearings of each pair disposed at symmetrical positions with the rotary shaft connected to the load interposed therebetween. ,
A first control circuit for controlling a current supplied to an electromagnet coil constituting the magnetic bearing in accordance with a change in air gap between the rotating shaft portion and the magnetic bearing; ON / OFF control of the switching element connected to the magnetic pole coil is performed by applying a pulse that is controlled in accordance with the air gap variation, and a pair of magnetic pole coils at a position opposing the rotating shaft portion on the upstream side of the switching element are connected. And energizing the magnetic bearings used in the high-speed rotating body, wherein the current energy of each magnetic pole coil is commutated to the other magnetic pole coil at the opposing position every time the pulse to one magnetic pole coil is turned off. Control circuit. A first control circuit according to claim 3 ,
A second control circuit that supplies a bias current to each magnetic pole coil to increase the static rigidity of each magnetic bearing,
4. The current supply control circuit for a magnetic bearing used in a high-speed rotating body according to claim 3 , wherein said two control circuits are configured so that currents can be applied to said magnetic pole coils by separate systems. One or a plurality of radial magnetic bearings having at least two pairs of magnetic pole coils facing the rotary shaft to perform position control of two coordinate axes (座標 axis, Y axis) in the radial direction of the rotary shaft;
5. A thrust magnetic bearing having at least one pair of magnetic pole coils opposed to a magnetic plate orthogonal to the rotation axis for performing position control of a coordinate axis (Z axis) in a thrust direction of the rotation axis. In the energization control circuit of
A plurality of magnetic pole coil groups in the radial magnetic bearing or the thrust magnetic bearing, wherein a bias current can be applied by a second control circuit common to each corresponding magnetic bearing; .

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