JPH0543879B2 - - Google Patents

Description

Detailed Description of the Invention <<Field of Industrial Application>> The present invention relates to a turbomolecular pump in which the rotor is supported by a magnetic bearing during operation, and in particular, the rotor is supported by an emergency bearing when the magnetic bearing is out of control. This invention relates to a turbomolecular pump.

<<Prior art>> In a turbomolecular pump whose rotor is supported by a magnetic bearing during operation, if the magnetic bearing becomes uncontrollable due to a power outage or circuit abnormality, the rotor will collide with the magnetic bearing's electromagnet, position sensor, and motor windings. The magnetic bearing is damaged and the pump cannot be restarted.

Therefore, this type of turbomolecular pump is equipped with an emergency bearing in addition to the magnetic bearing, and when the magnetic bearing cannot be controlled, the rotor is supported by the bearing, preventing collision between the magnetic bearing and the rotor. ing.

≪Problems to be solved by the invention≫ However, in the past, when the magnetic bearings were out of control, the rotor was supported only by the bearings, so if the rotor was rotating at high speed at that time, it would cause heat generation and impact. The bearing was damaged, and there was a risk that the rotor would become welded to the bearing due to the bearing lock, making it impossible to restart the pump.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to prevent damage to the emergency bearing due to heat generation and impact even if the magnetic bearing becomes uncontrollable while the rotor is rotating at high speed. It is an object of the present invention to provide a turbo-molecular pump of this type that can reliably avoid welding of the rotor to its bearing due to bearing lock.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a magnetic bearing that supports the rotor during operation, an emergency bearing that supports the rotor when the magnetic bearing cannot be controlled, and a pump backrest. a gas introduction pipe that introduces gas from the outside to the pressure side;
The present invention is characterized in that it has a valve that is provided in the gas introduction pipe and is opened when the magnetic bearing cannot be controlled.

<<Operation>> In the present invention, when the magnetic bearing is out of control, gas is introduced from the outside to the back pressure side of the turbo molecular pump, and the introduced gas rapidly reduces the rotational speed of the rotor, which is in an uncontrolled state. Since the rotational energy of the rotor is absorbed, the amount of heat generated in the emergency bearing is significantly reduced.

In addition, the introduced gas rapidly reduces the rotation speed of the rotor,
Since the rotational energy of the rotor is absorbed, the amount of heat generated in the emergency bearing is further reduced.

<<Example>> Hereinafter, a preferred example of the turbo-molecular pump according to the present invention will be described.

In the figure, a plurality of fixed blades 12 are arranged in the axial direction on the inner wall surface of a stator 10, which has a substantially cylindrical shape, and a plurality of rotary blades 16 are arranged on the outer wall surface of a rotor 14 arranged inside the stator 10. The fixed blades 12 are arranged alternately in the axial direction.

The rotor 14 is internally supported by a stator column 18, and the rotor 14 is internally supported during pump operation.
The magnetic bearing supporting the stator column 18
An axial electromagnet 20 and a radial electromagnet 2 provided in
2 is included.

Furthermore, the rotor 14 is rotationally driven by a motor 23 provided on the stator column 18, and its rotation speed, axial position, and radial position are measured by a sensor 2.
4, 26, and 28, respectively.

Furthermore, as the above-mentioned emergency bearings, dry type ball bearings 30 are used, which are provided on the upper and lower sides of the stator column 18, respectively.

In an emergency, the upper ball bearing 30 supports the upper part of the rotor in the axial and radial directions, and the lower ball bearing 30 supports the lower part of the rotor in the radial direction.

Further, a pipe 34 is inserted into the pump through a base 38 in parallel with the exhaust port 32 provided on the lower side of the pump, and an inert gas at normal pressure is supplied to the pipe 34 from the outside via a valve 38. Supplied.

Furthermore, the valve 38 detects a control abnormality of the magnetic bearing from the detection signal of the sensor 28, and is controlled to open and close by a control device (not shown) that detects an abnormality in the power supply, and if any abnormality is detected, the magnetic bearing cannot be controlled. (However, at that time, the main valve (not shown) is closed in advance).

Since this embodiment is configured as described above,
When the magnetic bearing is out of control, gas is introduced from the outside to the back pressure side of the pump, and the introduced gas rapidly reduces the rotational speed of the rotor 14 and absorbs the rotational energy of the rotor 14, so the amount of heat generated in the emergency bearing 30 is reduced. reduced.

As explained above, according to this embodiment, when the magnetic bearing is out of control, the rotor 14 rotates at high speed (e.g.
24,000 rpm), the introduced gas rapidly reduces the rotational speed of the rotor 14 and absorbs the rotational energy of the rotor 14, so the amount of heat generated in the bearing 30 is significantly reduced. Therefore, damage to the bearing 30 (especially the lower side) can be effectively prevented, and welding of the rotor to the bearing due to the bearing lock can be reliably avoided.

<<Effects>> As explained above, according to the present invention, even if the rotor is rotating at high speed when the magnetic bearing cannot be controlled, gas is introduced from the outside to the back pressure side of the pump. The gas rapidly reduces the rotational speed of the rotor and significantly reduces the amount of heat generated in the emergency bearing. Therefore, damage to the emergency bearing can be effectively prevented, and rotor welding to the bearing due to bearing lock can be reliably avoided, and as a result, safety and reliability against control abnormalities of the magnetic bearing can be significantly improved. .

[Brief explanation of the drawing]

The drawing is a configuration explanatory diagram showing a preferred embodiment of a turbomolecular pump according to the present invention. 10... Stator, 12... Fixed wing, 14...
Rotor, 16...rotor blade, 18...stator column, 20, 22...electromagnet, 30...bearing, 34...tube, 38...valve.

Claims (1)

[Claims] 1. A magnetic bearing that supports the rotor during operation, a sensor that detects the rotor support position, an emergency bearing that supports the rotor when the magnetic bearing cannot be controlled, and a gas introduction pipe that introduces gas from the outside to the back pressure side of the pump. A turbo-molecular pump characterized in that it has a valve that is provided in the gas introduction pipe and is controlled to open when it is detected that the magnetic bearing has become uncontrollable based on a detection signal from the sensor.