JPH06253523A - Dc brushless motor and turbo molecular pump employing it - Google Patents

Abstract

PURPOSE:To provide a DC brushless motor which can be employed for a turbo molecular pump operating under high temperature environment by enhancing heat resistance of a sensor for detecting the commutation timing. CONSTITUTION:Rotor of a DC brushless motor is provided with a rotational position detecting plate 81 having protrusions 81a and recesses 81b and sensors 61A-61C, each comprising a coil, are arranged thereabout. Distances between the rotational position detecting plate 81 and the sensors 61A-61C vary depending on the rotational position of the rotor thus varying the inductances of the sensors 61A-61C. A sine wave oscillation circuit 82 applies AC voltage to the sensors 61A-61C and the voltages across the sensors 61A-61C are rectified by rectifying circuits 84A-84C. Comparators 85A-85C binarize the voltages to produce signals 101A-101C which are employed in the determination of the rotational position of the rotor. A ROM 89 then reduces signals for 104U, V, V phases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC brushless motor suitable for use in a high temperature environment and a turbo molecular pump using the same.

[0002]

2. Description of the Related Art Some turbo molecular pumps capable of obtaining an ultrahigh vacuum use a DC brushless motor to drive their rotor blades. The first advantage of using a DC brushless motor for a turbo molecular pump is that it is smaller and consumes less power than an induction motor. The second advantage is that the backup battery can be eliminated. In other words, in a turbo molecular pump, a non-contact magnetic bearing is used as a bearing, and a mechanical bearing is used for protection, but when power supply to the magnetic bearing device is stopped due to a power failure or the like during high-speed rotation. In order to prevent wear and damage of the rotor and the protective bearing, it is necessary to allow the rotor to come into contact with the protective bearing after the rotational speed of the rotor has become sufficiently low. Therefore, conventionally, a backup battery is provided, and in the event of a power failure, power is supplied from the backup battery to the magnetic bearing device to continue operation. When a DC brushless motor is used for such a turbo molecular pump, the DC brushless motor acts as a generator at the time of power failure and can supply the regenerated electric power to the magnetic bearing device, so that the backup battery is used as described above. It becomes unnecessary.

In DC brushless motors, Hall ICs, semiconductor elements such as magnetoresistive elements are often used as sensors for detecting commutation timing. There is also a sensorless control method that does not use a sensor that detects the commutation timing.

[0004]

However, sensors such as Hall ICs and magnetoresistive elements that detect the commutation timing of DC brushless motors have a low heat resistance temperature of around 100 ° C., which is a high temperature environment such as a turbo molecular pump. There is a problem that it cannot be used for the motor used in. In the case of a turbo molecular pump, the temperature is about 150 ° C. due to heat generation of the motor itself and friction of exhaust gas.

On the other hand, although there are various sensorless control systems, since it is not known where the rotor is located at the time of starting, it is difficult to start because a starting method of, for example, exciting and rotating while watching the state is adopted. There is a problem. Also, in order to start like a step motor,
Generally, there is a problem that the torque at startup is small.

Further, in the case of the sensorless control system, since the commutation timing signal is detected from the three-phase cable for supplying electric power to the motor, it is easily affected by the length of the cable, noise, etc. There is a problem that is required. Further, in the case of the sensorless control system, since the position of the rotor at the time of start-up is unknown as described above, there is a problem that the motor cannot be restarted even when it is rotating by inertia. In particular, in the turbo molecular pump, another pump that sucks the gas discharged by this turbo molecular pump is also used, and at the time of starting, only the other pump is operated first and then the turbo molecular pump is started. Before, the rotor of the turbo-molecular pump is swung by the operation of the other pump. Therefore, in the sensorless control system, it becomes difficult to start the turbo molecular pump.

The present invention has been made in view of the above problems, and has a high heat resistance of a sensor for detecting commutation timing, and a DC brushless motor suitable for use in a high temperature environment, and a turbo molecular pump using the same. The purpose is to provide.

[0008]

[Means for Solving the Problems] D of the invention according to claim 1
The C brushless motor includes a rotor having a permanent magnet, a stator coil for generating a magnetic field for rotating the rotor, a plurality of rotational position detecting coils provided at predetermined positions around the rotor, and rotational position detecting coils for detecting the rotational position. A rotor position detection plate that is provided on the rotor at a position facing the coil and that changes the inductance of the rotor position detection coil according to the rotor rotation position, and a rotor position detection coil inductance obtained from the rotor position detection coil. Based on the signal corresponding to the rotation position detection signal generation means for generating the rotation position detection signal of the rotor, and the current supplied to the stator coil based on the rotation position detection signal from the rotation position detection signal generation means. And a motor drive control means.

A DC brushless motor according to a second aspect of the present invention is such that the distance between the rotational position detecting plate in the first aspect of the invention and the rotational position detecting coil changes according to the rotational position of the rotor. Is. A turbo molecular pump according to a third aspect of the present invention includes a plurality of stator blades, rotor blades that rotate between the stator blades, and a motor that rotates the rotor blades. The invention uses the DC brushless motor of the invention.

[0010]

In the DC brushless motor and the turbo molecular pump of the present invention, the rotation position detecting plate rotates as the rotor of the DC brushless motor rotates, and the rotation position detecting plate rotates the rotation position according to the rotation position of the rotor. The inductance of the detection coil changes. Then, the position detection signal generation means generates a rotation position detection signal of the rotor based on a signal corresponding to the inductance of the rotation position detection coil obtained from the rotation position detection coil, and based on this rotation position detection signal, The electric current supplied to the stator coil is controlled by the motor drive control means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a DC brushless motor of the present invention and a turbo molecular pump using the same will be described in detail below with reference to FIGS. Figure 1
Represents the entire configuration of the turbo molecular pump device.

The turbo-molecular pump device 1 is installed in, for example, a semiconductor manufacturing device, and discharges process gas from a chamber or the like. In this example, a flange 11 is formed on the upper end of the outer casing 10 formed in a cylindrical shape, and is connected to the semiconductor manufacturing apparatus by a bolt or the like.

A plurality of stator blades 12 are provided inside the outer casing 10.
Are arranged, and a plurality of rotor blades 14 are arranged between the respective stator blades 12. The rotor blades 14 are provided on the outer peripheral wall of the rotor 15, and the rotor 15 is fixed to the rotor shaft 18 with bolts 19 so as to rotate in conjunction with the rotor shaft 18 made of a magnetic material.

The rotor 15 is supported by so-called magnetic bearings, and two pairs of radial electromagnets 20 are disposed above the rotor shaft 18 so as to face each other with the rotor shaft 18 interposed therebetween.
The pair of radial electromagnets are arranged so as to be orthogonal to each other. Adjacent to the radial electromagnet 20, the rotor shaft 1
Two pairs of radial position detection sensors 22 facing each other with 8 in between
2 pairs are provided.

Further, two pairs of radial electromagnets 24 are similarly arranged under the rotor shaft 18, and the radial electromagnets 24 are also provided with two pairs of radial position detection sensors 26 adjacent to each other. . These radial electromagnets 20, 24
When the exciting current is supplied to the rotor shaft 18, the rotor shaft 18 is magnetically levitated. This exciting current is controlled in response to position detection signals from the radial direction position detection sensors 22 and 26 during magnetic levitation, whereby the rotor shaft 18 is held at a predetermined radial position.

A DC brushless motor 30 is arranged between the radial position detection sensor 22 and the radial position detection sensor 26 inside the outer casing 10. This DC
When the brushless motor 30 is energized, the rotor shaft 18 and the rotor blades 14 fixed to the rotor shaft 18 rotate.

A disc-shaped metal disk 31 made of a magnetic material is fixed to the lower portion of the rotor shaft 18, and a pair of axial electromagnets 32 and 34 are arranged so as to sandwich the metal disk 31 and face each other. Has been done. Further, an axial position detection sensor 36 is arranged so as to face the cut end of the rotor shaft 18.

The exciting currents of the axial electromagnets 32 and 34 are controlled in accordance with the position detection signal from the axial position detection sensor 36, so that the rotor shaft 18 is held at a predetermined axial position. ing. A rotation speed sensor 38 for detecting the rotation speed of the rotor shaft 18 is arranged at the lower end of the rotor shaft 18.

An exhaust port 52 for exhausting a process gas or the like from the semiconductor manufacturing apparatus is arranged in the lower portion of the exterior body 10 of the turbo molecular pump device. Further, a temperature sensor 50 such as a thermistor is arranged near the exhaust port 52. Further, the turbo molecular pump device is connected to the controller 45 via the connector 44 and a cable.

FIG. 2 is a block diagram showing an electrical configuration of the turbo molecular pump device 1 and the controller 45. As shown in this figure, the turbo molecular pump device 1 includes a DC brushless motor 30, a rotational position detection sensor 61 for detecting the rotational position of the rotor of the DC brushless motor 30, and
The electromagnet 62 (radial electromagnet 20, which constitutes the magnetic bearing,
24 and the axial electromagnets 32, 34. )When,
A magnetic bearing position detection sensor 63 (representing the radial position detection sensors 22 and 26 and the axial position detection sensor 36) is provided. The rotational position detection sensor 61 is
It is arranged around a rotation position detection plate described later.

Further, the controller 45 is a CPU (central processing unit) 71 for controlling the entire turbo molecular pump device.
And a ROM (Read Only Memory) 73, a RAM (Random Access Memory) 74, and an input / output interface circuit (I in the figure) connected to the CPU 71 via a bus 72 such as an address bus and a data bus.
/ O. ) 75 and the input / output interface circuit 7
5, a motor drive control circuit 76 as a motor drive control means, a rotational position detection signal generation circuit 77, and a magnetic bearing control circuit 78 are provided. The motor drive control circuit 76 supplies a three-phase drive current to the stator coil of the DC brushless motor 30 under the control of the CPU 71. The rotational position detection signal generating circuit 77 generates a rotational position detection signal of the rotor from the output signal of the rotational position detection sensor 61. The magnetic bearing control circuit 78 controls the exciting current of the electromagnet 62 based on the output signal of the position detection sensor 63 to hold the rotor shaft 18 at a predetermined position.

FIG. 3 shows a rotational position detecting plate in this embodiment,
It is a circuit diagram which shows the structure of the rotation position detection sensor 61 and the rotation position detection signal generation circuit 77. Rotation position detection plate 81
Is made of a magnetic material such as a silicon steel plate and has a large radius.
1a and a concave portion 81b having a small radius are formed in a disc shape alternately provided every 90 °. The rotational position detection plate 81 is attached to the rotor shaft 18 and
It is designed to rotate with it. The center of gravity of the rotational position detection plate 81 coincides with the center of rotation.

The rotational position detection sensor 61 is composed of three sensors 61A, 61B, 61C arranged at 120 ° intervals around the rotational position detection plate 81, and each sensor 61A, 6A.
Each of 1B and 61C is composed of a coil. The rotational position detection signal generation circuit 77 includes the sensors 61A and 61A.
A sine wave oscillation circuit 82 connected to one ends of B and 61C,
A coil 83A and a rectifier circuit 84A connected to the other end of the sensor 61A, a coil 83B and a rectifier circuit 84B connected to the other end of the sensor 61B, and a coil 83C and a rectifier circuit 84C connected to the other end of the sensor 61C. , One input end is connected to the output end of each rectifier circuit 84A, 84B, 84C, and the other input end is a reference voltage source 86A, 86
B, 86C connected to the comparators 85A, 85B,
It is equipped with 85C. The coils 83A, 83B,
The other end of 83C is grounded.

The rotational position detection signal generating circuit 77 further includes two latch circuits 87 and 88 and a ROM 89. The output terminal of the comparator 85A is connected to the address input terminal A0 of the ROM 89 and the latch circuit 8
7 is connected to the clock input terminal. Comparator 8
The output terminal of 5B is connected to the address input terminal A1 of the ROM 89 and is connected to the clear input terminal of the negative logic input of the latch circuit 87. The output terminal of the comparator 85C is connected to the address input terminal A2 of the ROM 89.
Further, the power supply voltage Vcc is applied to the D input terminal of the latch circuit 87 and is fixed in the H (high) state. The Q output end of the latch circuit 87 is connected to the clock input end of the latch circuit 88, the Q output end of the latch circuit 88 is connected to the address input end A3 of the ROM 89, and the negative output end of Q of the latch circuit 88 (Q in the figure is shown. Is connected to the D input terminal of the latch circuit 88. Also, ROM 89
From the data output terminals D0, D1, and D2 of the U phase commutation position detection signal 104U, the V phase commutation position detection signal 104V, and the W phase commutation position detection signal 104W, respectively. Is output.

FIG. 4 is a circuit diagram showing the sensor section in detail. Although only the sensor 61A is shown in this figure, the other sensors 61B and 61C have the same configuration. As shown in this figure, the sensor 61A and the coil 83A are connected in series to the sine wave oscillation circuit 82. Coil 83A
The inductance of is a fixed value. In addition, the rectifier circuit 84
A is connected to the connection point between the sensor 61A and the coil 83A.

FIG. 5 is an explanatory view showing the arrangement of the sensors 61A, 61B and 61C. As shown in this figure, the sensor 6
1A is U of the stator coil of the DC brushless motor 30.
The sensor 61B is arranged at a position corresponding to the phase winding 90U.
Is arranged at a position corresponding to the V-phase winding 90V, and the sensor 6
1C is arranged at a position corresponding to the W-phase winding 90W. Note that, as shown in FIG. 6, the U-phase winding 90U, the V-phase winding 90V, and the W-phase winding 90W are connected by star connection.

In FIG. 4, the sine wave oscillating circuit 82 generates a sine wave of 75 kHz, for example. Where the rotor shaft 1
When the rotation position detecting plate 81 rotates with the rotation of 8, the convex portions 81a and the concave portions 81b of the rotation position detecting plate 81 alternately face the sensor 61A, and therefore the distance between the rotation position detecting plate 81 and the sensor 61A. Changes. The inductance of the sensor 61A increases as the distance between them decreases, and decreases as the distance increases. Therefore, the AC voltage at the connection point between the sensor 61A and the coil 83A decreases as the distance between the rotational position detection plate 81 and the sensor 61A decreases, and increases as the distance increases. The same applies to the sensors 61B and 61C.

Next, the operation of the rotational position detection signal generation circuit shown in FIG. 3 will be described. DC brushless motor 30
The rotation position detection plate 81 rotates with the rotation of the rotor of
As described above, the sensor 61A according to the rotational position of the rotor,
The inductances of 61B and 61C change. Therefore,
The sensors 61A, 61B, and
AC voltage is applied to 61C, and sensors 61A, 61B, 6
The voltage across 1C is rectified into a direct current by the rectifier circuits 84A, 84B, 84C, and the value is comparators 85A, 8C.
Signal 101 obtained by binarization with 5B and 85C
The rotational position of the rotor can be known from A, 101B and 101C.

However, the signal 101 obtained by the above method
Timings of A, 101B, and 101C are different from the signals when the Hall IC is used as the sensor for detecting the rotational position. Therefore, in this embodiment, the ROM 89 is used to convert the signal into the same signal as that of the Hall IC. The conversion of this signal will be described in detail below with reference to FIGS. 7 to 10.

FIG. 7 shows the sensors 61A and 6 in this embodiment.
It is explanatory drawing which shows arrangement | positioning of the sensor when using Hall IC, without using 1B and 61C. As shown in this figure, the U-phase Hall IC 91U is arranged 60 ° before the U-phase winding 90U in the rotation direction, and the V-phase Hall IC 91V is V
It is placed 60 ° before the phase winding 90V in the direction of rotation and W
The phase hall IC 91W is arranged 60 ° before the W-phase winding 90W in the rotation direction.

FIG. 8 shows the Hall ICs 91U and 9 shown in FIG.
It is explanatory drawing which shows the relationship between the signal obtained from 1V, 91W, the rotation position of a rotor, and the timing of commutation, (a)-
(C) shows Hall ICs 91U and 91 shown in FIG. 7, respectively.
The signal waveform obtained from V and 91W is shown, (d) shows the rotation position of a rotor, (e) shows commutation timing.

In this embodiment, the comparators 85A, 85
Signals 101A, 101B, 10 obtained from B and 85C
1C and the signal 103 obtained from the latch circuit 88, the ROM 89 causes the Hall ICs 91U, 91
ROM 89 is used to obtain a signal similar to that obtained from V, 91W. The ROM 89 stores output data corresponding to each address as shown in FIG.

FIG. 10 is a timing chart showing the signal conversion operation by the ROM 89 during normal rotation.
Depending on the rotational position of the rotational position detection plate 81 shown in (e),
From the comparators 85A, 85B, and 85C, (a)-
The signals 101A, 101B, and 101C shown in (c) are output. Also, from the latch circuit 88, as shown in (d), when the signal 101B is in the H (high) state, the signal 101
A signal 103 that alternately switches between H and L (low) is output at the timing when A rises. These signals 101
R specified by A, 101B, 101C, 103
The address of the OM 89 is as shown in (f) in hexadecimal notation. The data corresponding to the address of the ROM 89 is as shown in (j). This data is ROM8
9 are output from the output terminals DO to D2, respectively (g) to
As shown in (i), U-phase signal 104U and V-phase signal 1
The signal becomes 04V and the W-phase signal 104W. This signal 104
U, 104V, 104W are Hall I as shown in FIG.
It is a signal similar to the signal obtained from C. Then, based on these signals 104U, 104V, 104W, the CPU 71 shown in FIG. 2 controls the motor drive control circuit 76, and commutation is performed at the timing as shown in (k).

In this embodiment, the reverse rotation of the motor is prevented by the latch circuits 87 and 88 shown in FIG. This will be described with reference to FIGS. 11 and 12. 11A to 11E show the signals 101A and 101B, the output signal 102 of the latch circuit 87, the output signal 103 of the latch circuit 88, and the rotational position of the rotational position detection plate 81 at the time of normal rotation of the motor. In addition, FIG.
(E) shows the signals 101A and 101B, the output signal 102 of the latch circuit 87, the output signal 103 of the latch circuit 88, and the rotational position of the rotational position detection plate 81, assuming that the motor continues to rotate in the reverse direction.

As shown in FIG. 11, 180 ° during normal rotation
The output signal 102 of the latch circuit 87 rises every rotation,
In response to this, the output signal 103 of the latch circuit 88 becomes 180
° Reverse every rotation. On the other hand, as shown in FIG. 12, the output signal 102 of the latch circuit 87 is fixed to L at the time of reverse rotation, and as a result, the output signal 103 of the latch circuit 88.
Is fixed to L or H and does not change. Therefore, at first, the correct U-phase signal 104U, V-phase signal 104V, and W-phase signal 104W are not output from the ROM 89.
Within 0 ° rotation, the correct U-phase signal 104U, V-phase signal 104V, and W-phase signal 104W are output, and normal rotation is started. In the turbo molecular pump, reversal of about 180 ° at the time of start-up does not cause any problem.

As described above, according to the present embodiment, the rotational position detecting sensor 61 is composed of a simple coil, so that it has high heat resistance. Therefore, the DC brushless motor 30 can be used in a high temperature environment like the turbo molecular pump 1. Further, as compared with the sensorless DC brushless motor, the DC brushless motor 30 of the present embodiment has a sensor, so that a large torque can be obtained even at the time of starting, and the adjustment according to the length of the cable is unnecessary.

Further, in this embodiment, since a signal similar to the signal when the conventional Hall IC is used as the rotational position detecting sensor is obtained, DC using the conventional Hall IC is obtained.
The motor drive control circuit can be configured by using the control circuit or IC for the brushless motor as it is.

Next, a modification of this embodiment will be described with reference to FIG. In this modification, a rotational position detection plate 111 having the shape shown in FIG. 13 is provided instead of the rotational position detection plate 81 shown in FIG.
A ternary circuit is provided instead of 85C, and the latch circuits 87 and 88 in FIG. 3 are removed.

The rotational position detection plate 111 is provided with convex portions 111a and 111b having a large radius and concave portions 111c having a small radius alternately provided every 90 °.
The radius of a is larger than the radius of the convex portion 111b. When this rotational position detecting plate 111 is used, the inductance of each sensor 61A, 61B, 61C changes in three steps, and the level of the output signal also changes in three steps. In this modification, the output signals of the sensors 61A, 61B, and 61C are each ternarized by a ternarization circuit, and each is converted into 2-bit data, which is used as an address input of the ROM 89 shown in FIG. In the ROM 89, a Hall IC is provided corresponding to each combination of data from the ternary circuit which is an address input.
The output data is stored so that a signal similar to the above is output.

According to this modification, the rotational position detecting plate 11
Since the two convex portions 111a and 111b of 1 can be identified,
Without providing the latch circuits 87 and 88 shown in FIG. 3, a signal similar to that of the Hall IC can be obtained only from the output signals of the sensors 61A, 61B and 61C.

In the case of a DC brushless motor used in a device in which rotor balance is important, such as a turbo molecular pump, the two convex portions 111a are arranged so that the center of gravity of the rotational position detecting plate 111 coincides with the rotational center. , 111b may be changed in thickness or a weight may be attached.

The rotational position detecting plate is not limited to the one having the convex portion and the concave portion, but may be any one that changes the inductance of the sensor according to the rotational position, for example, 90 °.
It may be a disk provided with magnetic bodies having different magnetic permeability alternately. Further, the DC brushless motor of the present invention can be used not only in the turbo molecular pump but also in various devices.

[0043]

As described above, according to the first to third aspects of the present invention, the sensor for detecting the commutation timing is composed of a simple coil, so that the sensor has a high heat resistance and can be used like a turbo molecular pump. There is an effect that the DC brushless motor can be used even in a high temperature environment.

Further, since the DC brushless motor according to the present invention has the sensor for detecting the commutation timing, the starting torque can be obtained as compared with the sensorless DC brushless motor. This has the effect of eliminating the need for adjustments according to the length of the cable.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a turbo molecular pump device of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a turbo molecular pump device and a controller in FIG.

3 is a circuit diagram showing a configuration of a rotation position detection plate, a rotation position sensor, and a rotation position detection signal generation circuit in FIG.

FIG. 4 is a circuit diagram showing in detail the sensor unit in FIG.

5 is an explanatory diagram showing the arrangement of sensors in FIG. 3. FIG.

FIG. 6 is an explanatory diagram showing a wire connection state of the winding wire in FIG. 5;

FIG. 7 is an explanatory diagram showing an arrangement of sensors when a Hall IC is used as a rotational position detection sensor.

8 is an explanatory diagram showing a relationship between a signal obtained from the Hall IC shown in FIG. 7, a rotor rotation position, and commutation timing.

9 is an explanatory diagram showing the content of data stored in a ROM shown in FIG. 3. FIG.

10 is an explanatory diagram showing a signal conversion operation by the ROM shown in FIG.

FIG. 11 is an explanatory diagram showing the operation of the rotational position detection signal generation circuit of FIG. 3 when the motor rotates normally.

FIG. 12 is an explanatory diagram showing the operation of the rotational position detection signal generation circuit of FIG. 3 when the motor rotates in reverse.

FIG. 13 is an explanatory diagram showing another example of the rotational position detection plate in the embodiment.

[Explanation of symbols]

 12 stator blade 14 rotor blade 15 rotor 18 rotor shaft 30 DC brushless motor 61 rotational position detection sensor 76 motor drive control circuit 77 rotational position detection signal generation circuit 81 rotational position detection plate

Claims (3)

[Claims] 1. A rotor having a permanent magnet, a stator coil for generating a magnetic field for rotating the rotor, a plurality of rotational position detecting coils provided at predetermined positions around the rotor, and a rotational position detecting coil for detecting the rotational position. A rotor position detection plate that is provided on the rotor at a position facing the coil and that changes the inductance of the rotor position detection coil according to the rotor rotation position, and an inductor for the rotor position detection coil obtained from the rotor position detection coil. Based on a signal corresponding to the rotation position detection signal generation means for generating a rotation position detection signal of the rotor, and a current supplied to the stator coil based on the rotation position detection signal from the rotation position detection signal generation means. A DC brushless motor, comprising: a motor drive control means. 2. The DC brushless motor according to claim 1, wherein a distance between the rotational position detecting plate and the rotational position detecting coil changes according to a rotational position of the rotor. 3. A plurality of stator blades, a rotor blade rotating between the stator blades, a motor rotating the rotor blades, a rotor having permanent magnets, and a stator for generating a magnetic field for rotating the rotors. A coil, a plurality of rotational position detecting coils provided at predetermined positions around the rotor, and a rotor provided at a position facing the rotational position detecting coil, the rotational position detecting coil depending on the rotational position of the rotor. Rotation position detection signal generation that generates the rotation position detection signal of the rotor based on the rotation position detection plate that changes the inductance of the coil and the signal according to the inductance of the rotation position detection coil that is obtained from the rotation position detection coil Means and a motor for controlling the current supplied to the stator coil based on the rotational position detection signal from the rotational position detection signal generating means. Turbomolecular pump characterized by comprising a DC brushless motor having a dynamic control unit.