JP3337230B2 - Magnetic bearing type turbo molecular 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 magnetic bearing type turbo molecular pump used for an exhaust system of an etching apparatus in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Conventionally, a magnetic bearing type turbo molecular pump of this type is known as shown in FIG. 4. In this turbo molecular pump, a displacement sensor 2 detects a displacement amount of a rotor 1, and The radial floating position of the rotor 1 is detected from the detection result. Then, the detected value is compared with a preset target value, and the electromagnet 3 is excited based on the comparison deviation. On the other hand, the displacement amount of the rotor 1 is
Is detected, and the axial floating position of the rotor 1 is detected from the detection result. Then, the detected value is compared with a preset target value, and the electromagnet 5 is excited based on the comparison deviation.

That is, such a turbo molecular pump is configured to support the rotor 1 at a predetermined position by the magnetic force of each of the electromagnets 3 and 5 generated as described above.

The turbo molecular pump is configured such that when the high frequency motor 6 is driven to rotate the rotor 1 at a high speed, gas or the like is sucked from an inlet 7 and exhausted from an outlet 8. I have. The rotation speed sensor 9 detects the rotation speed of the rotor 1.

By the way, in the semiconductor manufacturing process, particularly when the above-mentioned turbo molecular pump is used in the exhaust system of the etching apparatus, a highly reactive gas is often exhausted. Does not satisfy the specified conditions, deposits (Al
cl ₃ , B ₂ O _3, etc.) cannot be avoided.

In particular, when the turbo molecular pump is temporarily stopped for some reason, the rotor 1 is fixed to other members such as the stator blade 10 due to the above-mentioned deposits, and the turbo molecular pump is stopped. Is not restarted.

Therefore, in such a turbo-molecular pump, the inside of the pump is kept in a vacuum state, and then the atmosphere is introduced thereinto. The rotor 1 is blown off and the rotor 1 is separated from other members.

[0008]

However, in such a conventional magnetic bearing type turbo molecular pump, when the rotor 1 is fixed to another member as described above and the turbo molecular pump cannot be restarted, In order to introduce the atmosphere into the pump, it is necessary to provide at least a port for introducing the atmosphere and equipment such as a gate valve on the intake port 7 side and the exhaust port 8 side.

In addition, when the above-mentioned gate valve is operated by an operator, the operation is troublesome. Also, when the gate valve is automatically operated by a sequencer or the like,
It takes time and effort to create a sequence program, making it extremely inconvenient.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to separate the adhesion between a rotor and other members by forcibly vibrating the rotor. In order to achieve the above object, the present invention provides a position sensor unit for detecting a floating position of a rotor, an electromagnet for magnetically levitating the rotor, and a detection value output from the position sensor unit. A magnetic bearing type turbo molecular pump comprising: an electromagnet control unit that excites the electromagnet based on the comparison deviation; and a rotation speed sensor that detects the rotation speed of the rotor. Determining means for determining whether or not the rotor is fixed to another member based on a detection value output from the section or a detection value output from the rotation speed sensor; If it is determined that the rotor is fixed, characterized in that a and vibration signal generation section adding rotor vibration signal to the target value.

[0011]

According to the present invention, when the determination means determines that the rotor is stuck, the excitation signal generator adds the rotor excitation signal to the target value. As a result, the target value fluctuates according to the rotor excitation signal, and the rotor is forcibly vibrated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a magnetic bearing type turbo-molecular pump according to the present invention will be described below in detail with reference to FIGS.

Since the basic configuration of the turbo-molecular pump is the same as that of the prior art, the same members are denoted by the same reference numerals and detailed description thereof will be omitted.

This turbo-molecular pump has a position sensor section a as shown in FIG.
And a position detection circuit 11 are provided.
Detects the radial displacement of the rotor 1 and outputs the detection result S ₁ to the position detection circuit 11. Position detection circuit 11
It is configured to detect a radial floating position of the rotor 1 from the detection result, and outputs the detected value S ₂ to the electromagnet control unit b.

The electromagnet controller b has a comparator 12
Is provided, the comparator 12 obtains the comparison deviation S ₂₀ is compared with the detected value S ₂ preset and target value S _0. This comparison deviation S ₂₀ whereas output to the electromagnet drive circuit 14 via the phase compensation circuit 13, the electromagnet drive circuit 14 is configured to energize the electromagnet 3 on the basis of the comparison deviation S _20. The displacement sensor 4 and the electromagnet 5
Is incorporated in another position sensor unit and an electromagnet control unit (not shown) in the same manner as the displacement sensor 2 and the electromagnet 3.

That is, such a turbo molecular pump is configured to support the rotor 1 at a predetermined position by the magnetic force of each of the electromagnets 3 and 5 generated as described above.

Further, the turbo-molecular pump is provided with a protection sequence control circuit 15. The protection sequence control circuit 15 detects the detection value (rotation speed of the rotor 1) S ₃ from the rotation speed sensor 9 and the position detected value with S ₂ (radial floating position of the rotor 1) is input from the detection circuit 11, it intended to perform the Furochato as shown in FIG. 2, the result of the execution of such Furochato, protection sequence control circuit Reference numeral 15 designates the excitation command S ₄ as the excitation signal generator 1
Output to 6.

On the other hand, when the excitation signal generator 16 receives the excitation command S ₄ as described above, it generates, for example, a sine wave or the like as a rotor excitation signal S ₅ , and sends it to the comparator 12. The rotor excitation signal S ₅ is output from the comparator 12 to the target value S ₀ .

Next, the operation of the turbo-molecular pump configured as described above will be described with reference to the flowchart shown in FIG.

According to this turbo-molecular pump, the start signal S ₆ to the protection sequence circuit 15 is input (step 100), some kind of abnormality is determined whether or not detected (step 102), the determination If the result is no, ie, if any way no abnormality is detected, the protection sequence circuit 15 outputs the operation start command (acceleration command) S ₇ to the inverter circuit 17 (see Figure 3 (a)). As a result, the high frequency motor 6 is driven to rotate the rotor 1 (step 104).

[0021] Thereafter, the rotation of the rotor 1 based on S ₃ (rotational speed of the rotor 1) detection value output from the speed sensor 9 determines whether or not the acceleration normal sense (step 10
6) If the determination result is Yes, that is, if the vehicle is accelerating, it is determined that the rotor 1 is not fixed to another member (step 108).

On the other hand, when the result of the determination in step 106 is No, i.e., if for acceleration command S ₇ is output rotation of the rotor 1 is not accelerated (Fig. 3
(See (b)), it is determined that the rotor 1 is fixed to another member, and the rotor 1 is caused to vibrate. The vibration behavior, after protection sequence circuit 15 has output the operation stop command (deceleration command) S ₈ to the inverter circuit 17 (Step 1
10) The counter is started, and the first vibration operation is counted, that is, the number of vibration operations is counted as a value (step 112).

Then, it is determined whether or not the value of the counter (the number of vibration operations) has reached a predetermined set value (step 114). If the determination result is No,
Protection sequence circuit 15 outputs the excitation instruction S ₄ in the vibration signal generator 16 (see Figure 3 (c)).

On the other hand, upon receiving the vibration command S ₄ , the vibration signal generator 16 outputs the rotor vibration signal S ₅ to the comparator 12 for a predetermined time, and the comparator 12 outputs the rotor vibration signal S 5. ₅ is added to the target value S _0. As a result, the target value S ₀ fluctuates according to the rotor excitation signal S ₅ (FIG. 3).
(See (d)), and the rotor 1 is forcibly vibrated. After the elapse of the predetermined time, the process returns to step 102 (step 116).

If the result of the determination in step 114 is Yes, the rotor 1 remains fixed to another member even though the vibration operation has been performed for the predetermined set value. This state is displayed as abnormal so as to be understood by the operator (step 118).

By the way, if the determination result in step 102 is Yes, the i.e. if it detects some kind of abnormality, the detection value (radial floating position of the rotor 1) flying than S ₂ of the rotor 1 of the position detection circuit 11 It is determined whether or not the position is abnormal (step 120).
In the case of es, that is, when the flying position of the rotor 1 is abnormal, it is determined that the rotor 1 is fixed to another member, and
The process proceeds to step 112.

On the other hand, if the result of the determination in step 120 is No, an abnormality has been detected for a reason other than the floating position of the rotor 1, and even in this case, it is displayed so as to be understood by the operator as abnormal as described above. (Step 11
8).

Therefore, according to the above-described embodiment, when it is determined that the rotor is fixed to another member, the excitation signal generator adds the rotor vibration signal to the target value. Since the rotor fluctuates according to the excitation signal and the rotor is forcibly vibrated, the rotor can be separated from other members without separately providing a device for separating the rotor.

In the above-described embodiment, the radial floating position of the rotor 1 is used. Instead of this, a position sensor unit (not shown) including the displacement sensor 4 is used. The same effect as described above can be obtained even if the axial floating position is used.

The output of the rotor vibration signal may be arbitrarily set, but its frequency is preferably equal to the resonance frequency of the bearing.

[0031]

In the magnetic bearing type turbo-molecular pump according to the present invention, when the determination means determines that the rotor is fixed to another member, the excitation signal generation section sets the rotor vibration signal to the target value. The target value fluctuates according to the rotor excitation signal, and the rotor is forcibly vibrated, so that the rotor can be separated from other members without providing a separate device for separating the rotor. it can. Therefore, a low-cost pump can be provided.

In addition, since the above-described vibration of the rotor is performed by the determination means and the excitation signal generation unit, no labor is required and the usability is good.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a magnetic bearing type turbo molecular pump according to the present invention.

FIG. 2 is a flowchart illustrating the operation of the magnetic bearing type turbo-molecular pump.

FIG. 3 is an explanatory diagram illustrating an example of the operation of the magnetic bearing type turbo-molecular pump.

FIG. 4 is a sectional view showing a basic configuration of a magnetic bearing type turbo molecular pump.

[Explanation of symbols]

a position sensor portion b electromagnet control unit 1 rotor 3 electromagnet 9 rotational speed sensor 16 vibration signal generator S ₀ target value S ₄ rotor vibration signal

Claims (1)

(57) [Claims] A position sensor for detecting a floating position of the rotor; an electromagnet for magnetically levitating the rotor; a detection value output from the position sensor and a preset target value; An electromagnet control unit that excites the electromagnet based on the comparison deviation, and a magnetic bearing type turbo molecular pump including a rotation speed sensor that detects the rotation speed of the rotor, the detection value output from the position sensor unit, or Determining means for determining whether or not the rotor is fixed to another member based on a detection value output from the rotation speed sensor;
If it is determined by the above determination means that the rotor is stuck,
A magnetic bearing type turbo-molecular pump, comprising: a vibration signal generating section for adding a rotor vibration signal to the target value.