JP3103222B2 - Vacuum pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump.

[0002]

2. Description of the Related Art Conventionally, in a vacuum pump having an exhaust performance in a pressure range from atmospheric pressure to about 10 ^-4 torr, normally, in order to detect the degree of vacuum of a portion V to be depressurized, it is usually 10 ^-2 torr from atmospheric pressure. A vacuum gauge (for example, a Pirani gauge) for measuring to a degree and a vacuum gauge (for example, an ionization vacuum gauge) for measuring a pressure lower than this were necessary for measuring the ultimate pressure.

[0003]

As described above, two vacuum gauges are required, and the Pirani gauge for measuring the pressure at the time of low vacuum is expensive, so that the production cost is high. was there. By the way, the Pirani gauge has an advantage that measurement accuracy is good. However, when the pressure is reduced from atmospheric pressure to about 10 ^-2 torr, the measured value of the degree of vacuum does not require much accuracy, but it is sufficient if it is possible to confirm that the evacuation is progressing with the required accuracy. There was also.

Therefore, an object of the present invention is to reduce the degree of vacuum.
An object of the present invention is to provide a vacuum pump capable of measuring with desired accuracy and at low cost.

[0005]

In order to achieve the above object, a vacuum pump according to the present invention comprises: a rotor; an axial magnetic bearing having an electromagnet for supporting the rotor in a non-contact manner; A vacuum pump provided with a means for controlling a current supplied to the electromagnet of the axial magnetic bearing in order to hold the same at a required position, wherein a display means for displaying the degree of vacuum of the portion to be depressurized based on a current value flowing through the electromagnet is provided. It is characterized by having.

[0006]

According to the vacuum pump having the above structure, the rotor is
An axial force is received in accordance with the pressure difference between the pressure-reduced portion and the atmospheric pressure. On the other hand, the control means adjusts the current value of the electromagnet of the axial magnetic bearing to oppose the axial force. Generates magnetic coercive force by electromagnetic force. As a result, the rotor is held at a required position in the axial direction. In addition, the display means,
A display corresponding to the pressure of the pressure-reduced portion is performed based on the value of the current supplied to the electromagnet.

The pressure difference between the pressure-reduced portion and the atmospheric pressure is proportional to the axial force, and the current value is varied according to the force. The indication has a sufficient correlation with the pressure of the part to be depressurized.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a schematic configuration diagram of a vacuum pump as one embodiment of the present invention. Referring to FIG. 1, the vacuum pump includes a housing H including an upper pump housing PH and a lower motor housing MH, and a rotor chamber 1 formed in pump housing PH and communicating with a portion to be depressurized V.
And a rotor shaft 3 fixed to the rotor 2 coaxially and extending in the motor housing MH and rotatably driven while being supported in a non-contact manner in the motor housing MH; A computing means C for calculating the degree of vacuum in the rotor chamber 1 and a digital display as a display means for displaying the degree of vacuum computed by the computing means C. A is provided.

In the motor housing MH, an upper touch-down bearing 4 for receiving the rotor shaft 3 when it is stopped, a radial magnetic bearing 5 for supporting the rotor shaft 3 in a non-contact manner in a radial direction, and a rotor shaft Motor 3, a radial magnetic bearing 7, a lower touch-down bearing 8, an axial magnetic bearing 9 for supporting a disk 3a fixed to the lower end of the rotor shaft 3 in a non-contact manner in the axial direction, and a rotor shaft. An axial sensor 10 facing the lower end surface of the rotor shaft 3 and detecting the axial displacement of the rotor shaft 3 in a non-contact manner is provided.

At the upper part of the pump housing PH, there is provided a suction port 1a for communicating the part to be decompressed V with the rotor chamber 1.
An exhaust port 1b for exhausting the air in the rotor chamber 1 to the atmospheric pressure side is provided below the pump housing PH. The axial magnetic bearing 9 has a pair of electromagnets 9a and 9b that are arranged to face each other across the disk 3a. In this vacuum pump, the rotor shaft 3 is held at a required position in the axial direction by control means (not shown) included in a processing unit (not shown) for controlling the operation of the vacuum pump. That is, the control means adjusts the current supplied to the electromagnets 9a and 9b based on the axial displacement of the rotor shaft 3 detected by the axial sensor 10, thereby adjusting the attraction force of the electromagnets 9a and 9b. The rotor shaft 3 is magnetically levitated to a required position in the axial direction.

The calculating means C is included in the above-mentioned processing section, and based on the following equations (P), (Q) and (R), the pressure on the suction port 1a side of the rotor chamber 1 (the part to be depressurized V) is determined. The differential pressure ΔP from the pressure (atmospheric pressure) on the exhaust port 1b side is calculated, the pressure P of the pressure-reduced portion V is calculated from the differential pressure ΔP, and a signal based on the pressure P is output to the digital display A. . Fz = [K ₁ (I ₁ / δ ₁ ) ² −K ₂ (I ₂ / δ ₂ ) ² ] (P) ΔP = Fz / S (Q) P = P ₀ −ΔP (R) Fz is a force for pushing the rotor 2 upward in the axial direction caused by the differential pressure ΔP, S is the pressure receiving area of the rotor 2, δ ₁ and δ ₂ are the respective electromagnets 9 a and 9 _b obtained based on a signal from the axial sensor 10. The air gap amounts between the disk 9a and the disk 3a, I ₁ and I _2, are the values of the electromagnets 9a and 9
The value of the current supplied to b, P ₀ is the atmospheric pressure.

The digital display A changes the displayed value in accordance with the signal based on the pressure P from the calculating means C. The operation of this vacuum pump will be described. When the rotor shaft 3 is driven by the built-in motor 6 in a state where the rotor shaft 3 is supported by the radial magnetic bearings 5 and 7 and the axial magnetic bearing 9 in a non-contact manner, suction is performed from the portion to be decompressed V through the suction port 1a. The exhausted air is exhausted from the exhaust port 1b into the atmosphere, and the pressure in the depressurized portion V is reduced. As the pressure in the pressure-reduced portion V increases, the rotor 2 receives an axial upward force Fz proportional to the differential pressure ΔP, and the rotor 2 and the rotor shaft 3 move upward from a required position. The axial sensor 10 detects the axial displacement of the rotor shaft 3, and based on the detected output, control means adjusts the current values I ₁ and I ₂ of the electromagnets 9 a and 9 b of the axial magnetic bearing 9, and A magnetic coercive force is generated by an electromagnetic force against the directional force Fz. As a result, the rotor 2 is held at a required position in the axial direction.

According to this embodiment, the calculating means C is an electromagnet
Current value I to 9a and 9b₁, I _TwoOr the air gap
Δ₁, Δ_TwoBased on the above equations (P), (Q),
(R) is calculated, and the calculation result (pressure P of the pressure-reduced portion V)
Is output to the digital display A. Digital display A
Indicates the operation result of the operation result C. As a result,
The degree of vacuum of the pressure part V can be recognized. The above differential pressure ΔP
Is the weight of the rotor 2 as shown in the equations (P) and (Q).
Is proportional to the axial force Fz, and according to the force Fz,
Above air gap amount δ₁, Δ_TwoChanges, and the current
Value I₁, I_TwoIs varied, so that the energizing current value I₁,
I_Two, Air gap δ₁, Δ_TwoThe above display based on
Has a sufficient correlation with the pressure of the part V to be decompressed.
Therefore, the trueness of the portion to be decompressed V having the required accuracy is
You can gain emptiness. Moreover, conventional expensive pirani
Computing means composed of electronic circuits that are less expensive than gauges
C and the digital display A only
The degree can be recognized. In particular, the current value I₁, I
_TwoAnd air gap δ₁, Δ_TwoAbout
And a control signal for maintaining the axial position of the rotor 2.
It is a new method to grasp these.
There is no need to provide additional means, which is cost effective.
You.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, a numerical value corresponding to the pressure of the pressure-reduced portion V is displayed. It may be displayed. Further, in the above embodiment, the arithmetic means C may be omitted, and the digital display A may directly display the current values I ₁ and I ₂ . Even in this case, the degree of vacuum and the current values I ₁ , I ₂
The degree of vacuum can be known if the correspondence relationship with is obtained. In addition, the manufacturing cost can be further reduced.

As the display means, an analog indicator can be used in addition to the above embodiment. Further, a plurality of lamps corresponding to the level of the degree of vacuum may be sequentially turned on. Further, a single lamp may be used, and the flashing interval may be changed according to the level of the degree of vacuum. The configuration of the axial magnetic bearing 9 is such that in addition to the configuration shown in the above embodiment, a permanent magnet is used instead of one electromagnet and the remaining one electromagnet controls the axial displacement of the disk 3a. It may be. Even in such an axial magnetic bearing, the degree of vacuum can be detected from the current flowing through one electromagnet.

In addition, various design changes can be made without changing the gist of the present invention.

[0017]

As described above, according to the vacuum pump of the present invention, the degree of vacuum of the portion to be depressurized is displayed based on the value of the current flowing through the electromagnet of the axial magnetic bearing that supports the rotor in a non-contact manner. The manufacturing cost is lower than when a vacuum gauge such as Pirani gauge is used. Moreover, the pressure difference between the part to be depressurized and the atmospheric pressure is proportional to the axial force,
Since the value of the energizing current to the electromagnet is varied according to the force, the display based on the energizing current value by the display means has a sufficient correlation with the pressure of the part to be depressurized, and therefore has the required accuracy. The degree of low vacuum can be measured and recognized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a vacuum pump according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotor room 2 Rotor 3 Rotor shaft 3a Disk 9 Axial magnetic bearing 9a, 9b Electromagnet A Digital display (display means)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takuchi Ueyama 3-5-8 Minamisenba, Chuo-ku, Osaka City Inside Koyo Seiko Co., Ltd. (72) Inventor Takashi Yamamoto 3-12 Chikushinmachi, Sakai-shi, Osaka Daiki (58) Field surveyed (Int. Cl. ⁷ , DB name) F04D 19/04 F04D 29/04 F16C 32/04

Claims (1)

(57) [Claims] 1. An axial magnetic bearing having a rotor, an electromagnet for supporting the rotor in a non-contact manner, and a current supplied to the electromagnet of the axial magnetic bearing for holding the rotor at a required position in the axial direction. A vacuum pump comprising: means for displaying a degree of vacuum of a portion to be decompressed based on a current value flowing through the electromagnet.