JP3740083B2 - DC brushless motor and turbo molecular pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DC brushless motor and a turbo molecular pump using the DC brushless motor as a driving means.
[0002]
[Prior art]
One of the vacuum pumps used in semiconductor manufacturing equipment is a turbo molecular pump. Some turbo molecular pumps use a DC brushless motor as a drive motor for rotor blades. In a DC brushless motor, a Hall element is often used as a sensor for detecting commutation timing.
[0003]
FIG. 5 is a diagram showing only the rotor drive system of the turbo molecular pump. In this turbo molecular pump, the stator coil 103 of the DC brushless motor 102 is provided so as to surround the rotor 101, and the Hall element 104 is arranged next to the stator coil 103, and the rotor 101 side corresponding to the Hall element 104 is arranged on the rotor 101 side. A hall element magnet 105 is provided at a position corresponding to the magnetic pole phase of the rotor 101, an excitation pattern for exciting the stator coil 103 is generated from the signal of each hall element 104, and the stator coil 103 is excited based on the excitation pattern. The rotor 101 is rotationally driven by supplying an electric current.
[0004]
[Problems to be solved by the invention]
However, in the conventional turbo molecular pump, since the installation space of the hall element 104 is set next to the stator coil 103, the stator portion of the DC brushless motor 102 becomes larger, and accordingly, the rotor 101 of the pump becomes longer. There was a problem. In addition, since the hall element magnet 105 is provided on the rotor 101 side, it is necessary to secure an extra installation space on the rotor 101. For this reason, the rotor 101 becomes long, which hinders downsizing. In addition, there is a problem of high costs. In addition, since the rotor of the turbo molecular pump, which is a high-speed rotating machine, becomes longer, there is a problem that the natural frequency is lowered and vibration is easily generated.
[0005]
In view of the above circumstances, an object of the present invention is to provide a DC brushless motor capable of reducing the rotor length and reducing the size and vibration, and a turbo molecular pump using the DC brushless motor.
[0006]
[Means for Solving the Problems]
The DC brushless motor according to the first aspect of the present invention includes a rotor having a permanent magnet, a stator coil that generates a magnetic field for rotating the rotor, and a groove provided at a position away from the stator coil and facing the rotor . A ring sensor that outputs a voltage proportional to the depth, and a ring shape that is provided at a position on the rotor opposite to the gap sensor so that the depth differs by a predetermined angle in the circumferential direction around the rotation axis of the rotor And a drive control means for rotating the rotor by supplying an excitation current to the stator coil based on the output of the gap sensor.
[0007]
In this DC brushless motor, since the gap sensor for detecting the rotational position of the rotor is provided at a position away from the stator coil, the size of the stator portion can be reduced, thereby shortening the length of the rotor. Can be achieved. In addition, although the magnetic pole phase of the rotor can be detected, the hall element and hall element magnet used in the conventional DC brushless motor are no longer required, which increases the number of parts and troublesome extra wiring. Therefore, the increase in cost can be suppressed, and the Hall element and the Hall element magnet that are arranged next to the stator coil are not necessary. Therefore, the rotor length can be shortened, whereby the rotational stability can be enhanced, and the DC brushless motor can be reduced in size and cost.
[0008]
The turbo molecular pump of the invention of claim 2 is provided with a plurality of stator blades and a rotor blade that is integrated with the rotor and rotates between the stator blades, and the stator coil is arranged so as to surround the outer periphery of the rotor. In the turbo molecular pump that evacuates by rotating the rotor blades at high speed with the DC brushless motor, a ring-shaped groove having a depth different from each other at a predetermined angle in the circumferential direction around the rotation axis of the rotor is provided on the rotor. A gap sensor that outputs a voltage proportional to the groove depth is provided at a position facing the groove on the casing side, and an excitation current is supplied to the stator coil based on the output of the gap sensor to drive the rotor to rotate. To do.
[0009]
In this turbo molecular pump, since the gap sensor for detecting the rotor magnetic pole phase of the DC brushless motor is provided at a position away from the stator coil, it is possible to detect the rotor magnetic pole phase , The size can be reduced, whereby the pump rotor length can be shortened, whereby the turbo molecular pump can be reduced in size, cost and vibration. In addition, since the Hall element and Hall element magnet used in the conventional DC brushless motor are no longer required, there is no increase in the number of parts and unnecessary wiring trouble, and the cost increase can be suppressed. The arranged hall element and hall element magnet are not required. Therefore, the rotor length can be shortened, whereby the rotational stability can be enhanced, and the turbo molecular pump can be reduced in size and cost.
[0010]
A turbo molecular pump according to a third aspect of the present invention is the turbomolecular pump according to the second aspect, wherein a thrust disk for transmitting a thrust load acting on the rotor to the casing via a thrust magnetic bearing is provided integrally with the rotor at the end of the rotor. It is characterized by providing a groove.
[0011]
In this turbo molecular pump, a gap sensor for detecting the rotor magnetic pole phase of the DC brushless motor is provided at a position away from the stator coil, so that it is possible to detect the magnetic pole phase of the rotor, The size can be reduced, whereby the pump rotor length can be shortened, whereby the turbo molecular pump can be reduced in size, cost and vibration. In addition, the DC brushless motor can be driven by one gap sensor. In addition, since the Hall element and Hall element magnet used in the conventional DC brushless motor are no longer required, there is no increase in the number of parts and unnecessary wiring trouble, and the cost increase can be suppressed. The arranged hall element and hall element magnet are not required. Therefore, the rotor length can be shortened, whereby the rotational stability can be enhanced, and the turbo molecular pump can be reduced in size and cost.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a turbo molecular pump having a built-in DC brushless motor as driving means. The turbo molecular pump P has a configuration in which various components are provided inside a casing 1. In the casing 1, an intake port 1c is formed in the upper half 1a, and an exhaust port 1d is formed in the lower half 1b. In the casing 1, an axial flow step portion PA is provided at the upper portion, and a thread groove step portion PB is provided at the lower portion. The axial flow step portion PA is mainly composed of moving blades (rotor blades) 5 and stationary blades (stator blades) 3 provided in multiple stages, which will be described later, and the thread groove step portion PB is formed in a spiral thread groove 13 on the rotor 4. And the seal ring 15 fixed inside the casing 1.
[0017]
More specifically, the rotor 4 is disposed in the rotor chamber 2. The rotor 4 is configured to include a rotor shaft 4a erected vertically and moving blades 5 arranged radially around the rotor shaft 4a. A stationary blade 3 is fixed to the inner periphery of the casing upper half 1a.
[0018]
The rotor 4 is formed with a thread groove rotor portion 14 in which a thread groove 13 is formed below the rotor blade 5. The thread groove rotor portion 14 is formed with a thread groove 13 on a surface facing the seal ring 15 fixed to the inner periphery of the casing 1, and is slightly between the crest portion of the thread groove 13 and the inner periphery of the seal ring 15. Gaps are formed.
[0019]
A thrust disk 6 is provided at the lower end of the rotor shaft 4a. Thrust magnetic bearings 8 are provided on the upper and lower surfaces of the thrust disk 6 so as to face each other. By thrusting the thrust disk 6 magnetically, the thrust load acting on the rotor 4 via the thrust bearing 8 is provided. Is transmitted to the casing 1. Further, radial magnetic bearings 7a and 7b are respectively provided above and below the facing surface of the rotor shaft 4a and the casing 1 so as to be positioned above and below the DC brushless motor 11 for driving the rotor. Further, a ball bearing 9 is provided as a radial upper protective bearing at the upper end portion of the rotor shaft 4a, and a ball bearing 10 is provided as a radial and thrust lower protective bearing at the lower end neck portion.
[0020]
The DC brushless motor 11 has a structure in which a stator coil 11a is arranged so as to surround the outer periphery of the rotor shaft 4a, and a permanent magnet (not shown) constituting a rotor magnetic pole is fitted on the outer periphery of the rotor shaft 4a. Yes. The DC brushless motor 11 generates an excitation pattern of the stator coil 11a by detecting the rotational position of the rotor based on the signal from the rotor magnetic pole phase detection unit 20 provided on the thrust disk 6 by a drive control means (not shown). The excitation pattern supplies the exciting current to the stator coil 11a to rotationally drive the rotor shaft 4a.
[0021]
In this case, the rotor magnetic pole phase detection unit 20 for taking a signal for controlling the driving of the DC brushless motor 11 is disposed in the thrust disk 6 portion away from the stator coil 11a of the DC brushless motor 11, and is disposed on the rotor shaft 4a. The hall element magnets that have been placed and the hall elements that have been placed facing them are omitted.
[0022]
The configuration of the rotor magnetic pole phase detector 20 will be described in detail with reference to FIG. A sensor 25 for detecting the rotor rotational position is provided at a position on the casing side facing the lower surface of the thrust disk 6. Three sensors 25 are arranged at a pitch of 60 degrees on the same circumference around the rotation center of the thrust disk 6. In addition, a target 26 is provided at a position on the thrust disk 6 facing the sensor 25 to cause the sensor 25 to output a signal corresponding to the rotational position of the rotor shaft 4a. FIG. 2 shows the case of a DC brushless rotor pole number of 2 and a pole detection sensor arrangement of 60 degree intervals.
[0023]
The target 26 is formed in a pattern corresponding to the number of rotor magnetic poles of the DC brushless motor 11, and the target 26 in this example is a half area (180 degrees of the circumference) around the rotation center of the thrust disk 6. (Range) only. Different signals are output to the sensor 25 depending on whether the target 26 is present or not.
[0024]
The rotor magnetic pole phase detector 20 is configured by a combination of the sensor 25 and the target 26. As a combination of the sensor 25 and the target 26,
(1) Combination of gap sensor and uneven pattern on the surface of the thrust disk 6 (2) Combination of photo sensor and light and dark pattern on the surface of the thrust disk 6 (3) Combination of magnetic sensor and magnetic pole pattern on the thrust disk 6 side, etc. Is possible.
[0025]
When the combination of the gap sensor (1) and the uneven pattern on the surface of the thrust disk 6 is adopted, a gap sensor (such as an eddy current proximity sensor) is arranged at the position of the sensor 25 in FIG. A recess (groove) is formed at the position of the target 26. And the rotational phase of the rotor shaft 4a is determined by detecting the range of a recessed part and the range without a recessed part (range corresponding to a convex part) with a gap sensor.
[0026]
(2) When a combination of a photosensor and a light and dark pattern on the surface of the thrust disk 6 is adopted, the photosensor is arranged at the position of the sensor 25 in FIG. A mark with an identification color (black when the other part is a metal color) is formed. Then, the rotational phase of the rotor shaft 4a is determined by detecting a “bright” range (a range without a black mark) and a “dark” range (a range with a black mark) with a photosensor.
[0027]
(3) When a combination of a magnetic sensor and a magnetic pole pattern on the thrust disk 6 side is employed, a magnetic sensor (magnetoelectric conversion element such as a Hall element) is disposed at the position of the sensor 25 in FIG. Magnets having different polarities are arranged in a circular area. Then, the rotational phase of the rotor shaft 4a is determined from the alternating magnetic poles detected by the magnetic sensor.
[0028]
In either case, a target formation range, a divided region, or the like is set in accordance with the rotor magnetic pole phase of the DC brushless motor 11.
[0029]
In the turbo molecular pump P, the DC brushless motor 11 is driven to rotate the rotor 4 during vacuum exhaust. Then, after the first compression is performed between the moving blade 5 and the stationary blade 3 by the rotation of the rotor 4, the second compression is performed by the thread groove 13 of the thread groove step portion PB, and the exhaust port 1d. It flows in the direction and is evacuated. At this time, the rotor magnetic pole phase detection unit 20 configured by a combination of the sensor 25 and the target 26 detects the rotor magnetic pole phase of the motor, and the DC brushless motor 11 is driven based on the signal.
[0030]
In the case of this turbo molecular pump P, the rotor magnetic pole phase detector 20 of the DC brushless motor 11 is provided at a position away from the stator coil 11a, so that the size of the stator portion can be reduced, and thereby the rotor of the pump 4 can be shortened. Therefore, the turbo molecular pump can be reduced in size, cost, and vibration.
[0031]
Note that a rotation detection sensor (pulse sensor) for detecting the number of rotations of the rotor 4 is often provided around the thrust disk 6 so that the rotor magnetic pole phase is detected using the rotation detection sensor. It is also possible to do. Hereinafter, the rotor magnetic pole phase detector 20B improved as described above will be described. Here, a gap sensor is used as a sensor constituting the rotor magnetic pole phase detection unit 20B, and a groove (concave portion) is used as a target.
[0032]
3A and 3B are diagrams showing a schematic configuration of the rotor magnetic pole phase detector 20B. FIG. 3A is a sectional side view, FIG. 4B is a plan view of the target, and FIG. 4A is a ring-shaped groove formed as a target. The figure which shows the change of a depth change and the sensor output voltage corresponding to it, (b) is a figure which shows the rotor magnetic pole phase detection signal calculated based on the output voltage of a sensor.
[0033]
On the lower surface of the thrust disk 6, a ring-shaped groove 30 having a rectangular cross section centering on the rotational axis of the rotor shaft 4a is provided as a target. The ring-shaped groove 30 is divided into six parts every 60 degrees in the circumferential direction, and the divided grooves 30a to 30f are different in depth in order. When the starting end portion of the division groove 30a having the shallowest depth is set to 0 ° and the cross section of the division grooves 30a to 30f is developed in the rotation direction of the rotor shaft 4a, the division grooves 30a to 30f are formed as shown in FIG. The rotor shaft 4a gradually increases in depth along the rotational direction A by a certain depth. Therefore, one gap sensor 33 provided at a position facing the ring-shaped groove 30 outputs a voltage proportional to the depth of each of the divided grooves 30a to 30f.
[0034]
In this case, the phase pattern of the dividing grooves 30a to 30f corresponds to the phase of the rotor magnetic pole of the DC brushless motor 11 (see FIG. 1), and the control means (not shown) detects the rotor magnetic pole phase based on the signal from the gap sensor 33. Signals H1, H2, and H3 are output. That is, according to the magnitude of the output voltage V of the gap sensor 33, the control means outputs a signal under the following conditions.
(A) When V2 <V <V5, the H1 signal is output.
(B) When V4 <V, the H2 signal is output.
(C) When V6 <V or V <V3, the H3 signal is output.
[0035]
The H1 to H3 signals correspond to signals output by the Hall element in a normal DC brushless motor, and the control means determines the rotational position of the rotor based on this signal, and the DC based on the determination result. By supplying an excitation current to the stator coil 11 a of the brushless motor 11, the rotation of the rotor 4 can be controlled. Therefore, the DC brushless motor 11 can be driven by one sensor. In addition, since the existing rotation detection sensor can be used, there is no merit in that the number of parts is increased and unnecessary wiring is not required. In addition, the pulse detection for rotation speed calculation should just count ON of H2 signal, for example.
[0036]
In the above embodiment, the case where the rotor magnetic pole phase detection unit 20 is provided at the position on the lower surface side of the thrust disk 6 is shown. However, the sensor and the target constituting the rotor magnetic pole phase detection unit are provided on the side of the rotor shaft 4a. It may be provided. In that case, it is important not to extend the distance between the bearings (the substantial length of the rotor) by providing it in a portion other than between the radial magnetic bearings 7a and 7b.
[0037]
【The invention's effect】
As described above, according to the DC brushless motor of the first aspect of the present invention, since the gap sensor for detecting the rotational position of the rotor is provided at a position away from the stator coil, the rotor length is shortened. Therefore, the motor can be reduced in size, cost, and vibration.
[0038]
According to the turbo molecular pump of the second aspect of the present invention, since the sensor for detecting the rotor magnetic pole phase of the DC brushless motor is provided at a position away from the stator coil, the rotor length of the pump can be shortened. Therefore, it is possible to reduce the size, cost and vibration of the pump.
[0039]
According to the turbo molecular pump of the invention of claim 3, a ring-like groove having a depth different from each other by a predetermined angle in the circumferential direction around the rotation axis of the rotor on the rotor at the thrust disk portion at the end of the rotor, and the casing Since a gap sensor that outputs a voltage proportional to the depth of the groove is provided at a position facing the side groove, the size of the stator portion of the DC brushless motor can be reduced, and the rotor length can be shortened. Therefore, it is possible to contribute to miniaturization, cost reduction, and vibration reduction of the turbo molecular pump.
[0040]
Furthermore, since the rotor magnetic pole position can be detected using the existing rotor rotation detection sensor, the Hall element and magnet used in the conventional DC brushless motor are not required. Moreover, since it can be carried out only by changing the target structure of the current rotation detection sensor, it can be realized at a low cost without increasing the number of parts and troublesome wiring. In addition, since the Hall element and Hall element magnet that are arranged next to the stator coil are not required, the rotor length can be shortened, thereby reducing the size, cost, and vibration. Can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the overall configuration of a turbo molecular pump according to an embodiment of the present invention.
2A and 2B are diagrams showing a configuration of a rotor magnetic pole phase detection unit of a DC brushless motor built in the turbo molecular pump, wherein FIG. 2A is a cross-sectional view, and FIG. 2B is a plan view showing a positional relationship between a target and a sensor. .
FIGS. 3A and 3B are diagrams showing a schematic configuration of another rotor magnetic pole phase detector, in which FIG. 3A is a side sectional view and FIG. 3B is a plan view of a ring-shaped groove formed as a target.
4A is a diagram showing a change in the depth of the ring-shaped groove in FIG. 3 and a corresponding change in sensor output voltage, and FIG. 4B is a rotor magnetic pole phase detection calculated based on the output voltage of the sensor. It is a figure which shows a signal.
FIG. 5 is a configuration diagram of a DC brushless motor in a conventional turbo molecular pump.
[Explanation of symbols]
P Turbo molecular pump 1 Casing 3 Static blade (stator blade)
4 Rotor 4a Rotor shaft 5 Rotor blade (rotor blade)
6 Thrust disk 8 Thrust magnetic bearing 11 DC brushless motor 11a Stator coils 20 and 20B Rotor magnetic pole phase detector 25 Sensor 26 Target 30 Ring-shaped groove (target)
33 Rotation position detection sensor

Claims (3)

A rotor having a permanent magnet, a stator coil that generates a magnetic field for rotating the rotor, and a gap sensor that is provided at a position away from the stator coil and opposed to the rotor and outputs a voltage proportional to the depth of the groove And a ring-shaped groove provided at a position on the rotor opposite to the gap sensor so that the depth differs by a predetermined angle in the circumferential direction around the rotation axis of the rotor, and based on the output of the gap sensor A DC brushless motor comprising drive control means for supplying an excitation current to the stator coil to rotationally drive the rotor. A plurality of stator blades and a rotor blade integrated with the rotor and rotating between the stator blades are provided inside the casing, and the rotor blades are rotated at high speed by a DC brushless motor in which a stator coil is arranged so as to surround the outer periphery of the rotor. In the turbo molecular pump that evacuates by
A ring-shaped groove having a depth different from each other by a predetermined angle in the circumferential direction around the rotation axis of the rotor on the rotor, and a voltage that outputs a voltage proportional to the groove depth at a position facing the groove on the casing side A turbo molecular pump characterized in that a sensor is provided, and an excitation current is supplied to a stator coil based on an output of a gap sensor to rotationally drive a rotor. 3. The thrust disk according to claim 2, wherein a thrust disk for transmitting a thrust load acting on the rotor via a thrust magnetic bearing to the casing is provided integrally with the rotor at the end of the rotor, and a groove is provided in the thrust disk. Turbo molecular pump.

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