JP2536512B2 - Magnetic bearing device for turbo molecular pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic bearing device for a turbo molecular pump including an emergency braking system for a rotor shaft.

[Prior Art] When using a completely levitation type magnetic bearing for the rotor shaft of a turbo molecular pump (hereinafter referred to as TMP), the rotor shaft is brought into contact (touchdown) when the magnetic bearing malfunctions, also serving as support when the pump is stopped. ) Is equipped with a touch-down bearing (ball bearing) for backup. Malfunctions of magnetic bearings include not only the failure of the magnetic control system resulting in malfunction or loss of control, but also accidents such as disconnection of control cables, disconnection of connectors from the original TMP, and forgetting to connect them. If such a malfunction occurs, abnormal vibration or the like occurs and the rotor shaft repeatedly contacts the touchdown bearing, or particularly in the latter case, the rotor shaft completely contacts the touchdown bearing.

[Problems to be Solved by the Invention] However, in this type of TMP, the touchdown bearing (ball bearing) cannot be lubricated, so that the touchdown bearing may contact the rotor shaft at an early stage. There is a problem of damage. The reason why lubricating oil or grease cannot be supplied to the touchdown bearing is
In the first place, one of the aims of applying magnetic bearings to TMP is because it is rooted in achieving a completely dry (oil-free) vacuum without contamination of the exhaust system by oil vapor or the like.

Therefore, as a measure to improve the durability of a touchdown bearing that supports a high-speed rotating body in a vacuum, it has been proposed to use a ball bearing coated with gold, silver, tin, etc. The reality is that it is unavoidable that it will be damaged early by repeated use.

As described above, in the TMP that uses the magnetic bearing system, the life of the touchdown bearing is short, which causes an accident that the rotor is destroyed due to runout of the shaft, or else maintenance of the touchdown bearing is difficult. It creates troublesome problems.

[Means for Solving the Problems] The present invention solves such problems by contacting a touchdown bearing with a rotor shaft that rotates at an extremely high speed due to malfunction of a magnetic bearing during operation of a TMP. If such a situation occurs, the solution will be solved by immediately stopping the rotation and taking measures to minimize damage to the touchdown bearing.

That is, the means adopted by the present invention for solving the problem is a TMP including a magnetic bearing that supports the rotor shaft in a levitation manner inside the motor housing, and a touchdown bearing that backs up the rotor shaft when the magnetic bearing malfunctions. A magnetic bearing failure detecting means for detecting a malfunction of the magnetic bearing and a gas introduction system passage for introducing gas into the motor housing are additionally provided, and a gas introduction valve interposed in the gas introduction passage is provided. It is to be opened when the bearing failure of the magnetic bearing failure detection means is detected.

[Operation] With this configuration, when the magnetic bearing malfunctions during the operation of the TMP, the magnetic bearing malfunction detecting means detects it.
Further, the gas introduction valve is opened, and the gas is introduced into the vacuum motor housing from the attached gas introduction system passage.

Then, the gas introduced into the motor housing is
A braking force by viscous resistance is applied to the rotor shaft that is rotating at a high speed to stop the rotation of the rotor shaft. In fact, it is known that the braking action by viscous resistance of the introduced gas works stronger than the electrical braking action from the motor.

Further, as the gas introduced into the motor housing flows through the inside of the motor housing, the touchdown bearing, which generates heat due to friction, is given a cooling action that cannot be obtained in a vacuum. It also acts to reduce the coefficient of friction.

Therefore, if the rotor shaft, which is rotating at a high speed, comes into contact with the touchdown bearing due to a failure of the magnetic bearing, etc., the rotation of the rotor shaft is stopped immediately, and at the same time, the touchdown bearing is cooled and the friction is reduced. As a result, the touchdown bearing can be minimally damaged.

Moreover, in the present invention, the gas introduced into the motor housing provides a braking force due to viscous resistance to the rotor shaft that is rotating at a high speed, thereby stopping the rotation of the rotor shaft. Since an excessive resistance is not directly applied to the turbo molecular pump, a sufficient amount of gas is introduced into the motor housing when a bearing failure is detected, and the turbo molecular pump is urgently stopped within a practically effective time without damaging or damaging the rotor blades. It becomes possible.

[Embodiment] An embodiment of the present invention will be described below in detail with reference to the drawings.

Figure 1 shows a TM equipped with a magnetic bearing of the complete levitation system.
The principal part structure of P is shown in figure.

In this motor, a rotor shaft 2 to which a rotor 1 is fixed is attached to a built-in motor 4a in a motor housing 3,
It is configured to be rotationally driven by 4b, and around the rotor shaft 2 inside the motor housing 3,
Magnetic bearings 5, 7 and 9 for levitationally supporting the rotor shaft 2 sandwiching the motor are arranged.

The magnetic bearing 5 is formed by arranging electrode stones 5a around the rotor shaft 2 with a predetermined gap above the motor, and constitutes a radial bearing that supports the rotor shaft 2 in the radial direction. In the vicinity of the magnetic bearing 5,
A radial sensor 6 for detecting the radial displacement of the rotor shaft 2 is attached. The magnetic bearing 7 is formed by arranging an electrode stone 7a paired with the magnetic bearing 5 at a position below the motor, and also constitutes a radial bearing. A radial sensor 8 is also attached in the vicinity thereof. Further, the magnetic bearing 9 is disposed in the motor housing 3 at the lower end portion of the rotor shaft 2, and the thrust ring 10 is detachably attached to the lower end portion of the rotor shaft 2 with a predetermined gap above and below the thrust ring 10. Electromagnets 9a and 9b sandwiching the ring 10
Are arranged to form a thrust bearing that supports the rotor shaft 2 together with the rotor 1 in the axial direction. Further, a thrust sensor 11 for detecting the axial displacement of the rotor shaft 2 is attached to face the lower end of the rotor shaft 2.

In addition, in the magnetic bearing device of the complete levitation system as described above, touch-down bearings (unlubricated ball bearings) 12, 13, 13 for backing up the rotor shaft 2 when the magnetic bearings 5, 7, 9 malfunction Is attached. That is, the radial touchdown bearing 12 is arranged in the motor housing 3 above the magnetic bearing 5, and the radial thrust touchdown bearings 13, 13 are arranged in the motor housing 3 between the magnetic bearing 7 and the magnetic bearing 9. are doing. These touch-down bearings 12, 13, 13 support the rotor shaft 2 that is touched down when the TMP is stopped, and during operation, the rotor shaft 2 comes into contact with the rotor shaft 2 when the magnetic bearing malfunctions. Needless to say, the clearance is adjusted so as to prevent direct contact with the magnetic bearing.

In the other figures, 14 is an exhaust port of the TMP, which is usually connected with a back pump such as an oil rotary pump RP. Further, reference numeral 15 denotes a cable conducting port for leading out a cable from an electromagnet or a sensor in the motor housing 3 to a magnetic control circuit 16 installed outside.

Therefore, according to the present invention, in the TMP in which the rotor shaft 2 is levitationally supported by the magnetic bearing device, according to the present invention, the following configuration is additionally provided in order to cope with the malfunction of the magnetic bearings 5, 7, 9. are doing.

That is, the magnetic bearing failure detection means 1 for detecting each malfunction (EMERGENCY) of the magnetic bearings 5, 7, and 9 described above.
7 are installed. This detection means 17 is the magnetic control circuit 1
6 is built in and is integrally configured.
And each gap are monitored, and if they deviate from the proper gap size and approach abnormally, it is determined that the bearing is malfunctioning. Then, at the same time when the malfunction of the bearing is determined, the EMERGENCY signal is transmitted and the driving by the motors 4a and 4b is stopped. At this time, generally, the motor brakes are simultaneously activated. Also, at this time, an alarm is issued, and the shut-off valve on the TMP intake side (not shown) is automatically closed.

In addition, a vent 18 is provided at the bottom of the motor housing 3,
A gas introduction system passage 19 for introducing gas from the outside is connected to the vent 18 via a normally closed gas introduction valve 20.

The gas introduction valve 20 sends an EMERGENC signal when the magnetic bearing defect detecting means 17 determines that the bearing operation is defective.
When the Y signal is received, it is opened at the same time and gas is immediately introduced into the motor housing 3 from the outside.

With a TMP with such a configuration, during operation,
When the rotor shaft 2 loses control due to a failure of each magnetic bearing and its control system, a handling error, an earthquake, a wire breakage accident, or other external factors, the magnetic bearing failure detection means 17 causes the failure of the magnetic bearing. The EMERGENCY signal is transmitted to the gas introduction valve 20 provided in the introduction path 19, and the gas introduction valve 20 that receives this signal is opened, and the gas is exhausted from the pump chamber during operation and inside the motor housing 3 in a vacuum state. The gas will be introduced immediately.

However, when the motor housing 3 is filled with gas, the above-described braking action on the rotor shaft 2 and the cooling action on the touchdown bearings 12, 13 and 13 and the action of lowering the friction coefficient are exhibited, so that the rotor is reduced. When the shaft 2 comes into contact with the touchdown bearings 12, 13, 13, which are instantly rotated at tens of thousands of revolutions, the contact time and heat generation and the degree of wear can be shortened and alleviated. That is,
It is possible to minimize the damage that each touchdown bearing receives each time it comes into contact, and to extend its service life.

Regarding the magnetic bearing device to which the present invention is applied,
Of course, the structure is not limited to the structure shown in the illustrated example, but is generally applicable to those using a magnetic bearing. Further, the specific configuration of the magnetic bearing defect detection means does not matter.

As described in detail above, in the TMP magnetic bearing device of the present invention, when the rotor shaft comes into contact with the touchdown bearing for some reason, the magnetic bearing malfunctions, and the motor housing By immediately introducing gas from the outside to the inside of the rotor, the rotor shaft can be stopped quickly and the touchdown bearing can be protected and cooled by the introduced gas.
Thereby, the damage of the touchdown bearing can be alleviated and the life of the touchdown bearing can be improved. Moreover, the present invention provides a braking force utilizing the viscous resistance of the introduced gas to the rotor shaft that is rotating at high speed inside the motor housing, and does not cause excessive resistance to directly act on the rotor blades. By introducing a sufficient amount of gas into the motor housing at the time of detection, the turbo molecular pump can be brought to an emergency stop within a practically effective time without damaging or damaging the rotor blades.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a partial cross section showing an outline of the TMP bearing device of the present invention. 1 ...... Rotor 2 ...... Rotor shaft 3 ...... Motor housing 5 ...... Radial magnetic bearing 7 ...... Radial magnetic bearing 9 ...... Thrust magnetic bearing 12 ...... Radial touchdown bearing 13 ...... Radial thrust touchdown bearing 17 ... … Magnetic bearing failure detection means 19 …… Gas introduction path 20 …… Gas introduction valve

Claims (1)

(57) [Claims] 1. A turbo molecular pump comprising a magnetic bearing for levitationally supporting a rotor shaft inside a motor housing, and a touchdown bearing for backing up the rotor shaft when the magnetic bearing malfunctions. A magnetic bearing defect detecting means for detecting and a gas introducing system passage for introducing gas into the motor housing are attached, and a gas introducing valve interposed in the gas introducing system passage is used as a bearing of the magnetic bearing defective detecting means. A magnetic bearing device for a turbo molecular pump, which is opened when a defect is detected.