JP2000291586A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent a rotor cylindrical body and a stator cylindrical body from being approached abnormally or brought into contact with each other in a vacuum pump equipped with a screw groove pump part. SOLUTION: In a composite type turbomolecular pump equipped with a screw groove pump part, formed out of a rotor cylindrical body 12, and of a stator cylindrical body 22 in such a way that a screw is formed in the inner circumferential surface 22a of the stator cylindrical body 22 to be formed into the screw groove pump part, an air gap sensor detecting an air gap formed between the outer circumferential surface 12a of the rotor cylindrical body 12 and the inner circumferential surface 22a of a stator cylindrical body 22 is fitted to the inner circumferential surface 22a adjacent to the lower end of the stator cylindrical body 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread groove comprising a rotor cylinder and a stator cylinder, wherein a thread is formed on one of an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder. The present invention relates to a vacuum pump having a pump unit, and more particularly, to prevention of contact between a rotor cylinder and a stator cylinder.

[0002]

2. Description of the Related Art As a vacuum pump having a thread groove pump portion, there is, for example, a compound turbo molecular pump. As is well known, a compound turbo molecular pump is designed to knock down molecules by a speed difference between a rotor blade rotating at a high speed of tens of thousands of revolutions per minute and a stator blade, and a screw groove formed on an inner peripheral surface of the stator and a rotor. Gas is discharged through a flow path formed by the outer peripheral surface and a turbine blade portion composed of multiple stages of rotor blades and multiple stages of stator blades, a rotor cylindrical body having a flat outer peripheral surface, and a screw. It is configured in combination with a thread groove pump portion formed of a stator cylindrical body having a grooved inner peripheral surface. The rotor is rotatably supported by bearings such as a five-axis control type magnetic bearing including an active radial magnetic bearing and an active thrust magnetic bearing. A touchdown bearing is provided to support the rotor shaft in an emergency such as a failure of a magnetic bearing.

[0003] The air gap between the two cylinders constituting the thread groove pump portion, that is, the air gap between the thread groove portion of the stator cylinder and the outer peripheral surface of the rotor cylinder (hereinafter, the air gap of the thread groove pump portion as necessary) Abbreviated as a gap)
In order to prevent the outer peripheral surface of the rotor cylinder from coming into contact with the thread groove of the stator cylinder, that is, to prevent the rotor side from coming into contact with the stator side, it is desirable that the gap be somewhat wide. However, the air gap of the screw groove pump portion is as narrow as possible in order to prevent the gas sucked from the suction port of the vacuum pump from flowing backward in the screw groove portion, that is, to improve the pumping speed efficiency of the vacuum pump. Spacing is desirable. In consideration of these two contradictory conditions and other conditions, the gap of the air gap of the thread groove pump portion is determined.

[0004] In addition to the air gap of the thread groove pump section, the above-mentioned composite turbo molecular pump has an air gap between a magnetic bearing and a rotor shaft, an air gap between a rotor blade and a stator blade, and a touchdown. An air gap such as an air gap between the inner ring of the bearing and the rotor shaft (hereinafter abbreviated as an air gap of the touch-down bearing as necessary) is also formed.

[0005] These air gaps are also set so as to prevent contact between the components and to have a size corresponding to each functional purpose. Among them, especially the air gap of the touchdown bearing is the air gap between the magnetic bearing and the rotor shaft, the air gap between the rotor blade and the stator blade, the air gap of the thread groove pump part, and other air gaps. It is set smaller than.
This is to prevent the rotor side from coming into contact with the stator side when the rotor shaft is supported by the touch-down bearing when the magnetic bearing stops functioning due to failure of the vacuum pump, entry into the atmosphere, power failure, or the like.

[0006] However, the touchdown bearing is a consumable item, and the touchdown bearing wears every time the rotor shaft is repeatedly touched down, and the air gap of the touchdown bearing gradually widens. If the air gap of the touch-down bearing expands beyond a certain value, it will not function as a touch-down bearing. Then, the rotor side and the stator side come into contact with each other at the time of touchdown.

[0007] The air gap of the thread groove pump section is not always as designed, but actually varies from product to product depending on the precision of parts and the assembly state. In addition, when the vacuum pump is in operation, the lower part of the cylinder of the rotor expands in the radial direction due to centrifugal force and heat, not only narrowing the air gap of the thread groove pump part, but also contacting the thread groove part of the stator cylinder body in some cases. Sometimes.

As described above, the gap of the air gap of the thread groove pump portion is set so that the outer peripheral surface of the rotor cylinder does not come into contact with the thread groove portion of the stator cylinder during normal operation or touchdown, and the suction port of the vacuum pump. The size is set so that the gas sucked from above does not flow backward in the screw groove portion. Therefore, in the above-described composite turbo molecular pump,
When the magnetic bearing is functioning normally, the air gap of the thread groove pump section does not become abnormally narrow, or the rotor cylinder and the stator cylinder do not come into contact with each other. However, as described above, when the touch-down bearing is worn and the gap of the air gap of the touch-down bearing is widened, even when the air gap of the thread groove pump portion is as designed, at the time of touch-down, Contact between the rotor side and the stator side occurs.

If the interval of the air gap of the touch-down bearing is constantly monitored, and if the interval becomes larger than a certain value, an alarm is issued to urge the replacement of parts or to stop the operation of the vacuum pump. Good, but this has not yet found an effective solution. This is largely due to the very small air gap spacing of the touchdown bearings.

A method for constantly monitoring the operation failure of a magnetic bearing is disclosed in Japanese Patent Application Laid-Open No. 63-23997, Japanese Patent Application Laid-Open No.
As disclosed in, for example, Japanese Patent No. 1697, several proposals have been made. By detecting a malfunction of the magnetic bearing, the shock received by the touch-down bearing is reduced, and the wear of the touch-down bearing is reduced. Indirectly in this manner, contact between the rotor side and the stator side is prevented.

[0011] However, the air gap of the thread groove pump part differs from product to product depending on the precision of parts and the assembling condition, and the lower part of the cylindrical body of the rotor expands in the radial direction due to centrifugal force and heat when the vacuum pump is operated. In view of the above, the method of always monitoring the operation failure of the magnetic bearing cannot prevent the rotor side and the stator side from approaching abnormally or coming into contact with each other.

[0012]

The object of the present invention is to provide a rotor cylinder and a stator cylinder, and one of an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder. An object of the present invention is to reliably prevent abnormal approach and contact between a rotor cylinder and a stator cylinder in a vacuum pump having a thread groove pump portion having a thread formed therein.

[0013]

In order to solve the above-mentioned problems, the present invention comprises a rotor cylinder and a stator cylinder, and a screw is provided on one of an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder. In the vacuum pump having a thread groove pump portion formed with a groove, an air gap between the outer peripheral surface of the rotor cylinder and the inner peripheral surface of the stator cylinder is detected at a predetermined position on the inner peripheral surface of the stator cylinder. An air gap sensor was provided.

A plurality of the air gap sensors are provided on the inner peripheral surface of the stator cylinder at predetermined intervals in a circumferential direction. Further, the air gap sensor is disposed on an inner peripheral surface near a lower end of the stator cylinder.

One of a contact sensor and an eddy current sensor is used as the air gap sensor. The contact sensor is constituted by a pair of contacts arranged on the inner circumferential surface of the stator cylinder at a predetermined minute interval in a circumferential direction.

Further, a vacuum pump having a thread groove pump portion composed of a rotor cylinder and a stator cylinder is provided with an air gap between an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder. An air gap sensor for detecting an air gap value, a memory for storing an air gap value detected by the air gap sensor, a discriminator for comparing the detected air gap value with a set value, and an air gap value detected by the discriminator. And an interlock circuit that activates the interlock when it is determined that is less than or equal to the set value.

[0017]

FIG. 1 is a longitudinal sectional view of one embodiment of a compound turbo molecular pump to which the present invention is applied. This composite turbomolecular pump is a large flow rate turbomolecular pump combining a turbine blade portion and a thread groove pump portion, and includes a rotor 10, a stator 20, and a magnetic bearing device 30 that rotatably supports the rotor 10. Have been. The rotor 10 includes a rotor cylinder 12 having a multi-stage rotor blade 11 and a flat outer peripheral surface 12a. Stator 20 includes a plurality of stator blades 21 and a stator cylinder 22 having a threaded inner peripheral surface 22a. The multi-stage rotor blades 11 and the multi-stage stator blades 21 constitute the turbine blade portion, and the rotor cylinder 12 having a flat outer peripheral surface 12a and the stator cylinder 22 having a threaded inner peripheral surface 22a are formed by the screw Construct a groove pump part.

The magnetic bearing device is a so-called five-axis control type magnetic bearing device, comprising a rotor shaft 31, a first radial magnetic bearing 32 comprising a radial electromagnet 32a and a radial displacement sensor 32b, and a radial electromagnet 33a. A second radial magnetic bearing 33 including a radial displacement sensor 33b, a first thrust magnetic bearing 34 including an axial electromagnet,
It comprises a second thrust magnetic bearing 35 including an axial electromagnet, an axial displacement sensor 36, a touchdown bearing 37, and a high frequency motor 38.

The gap sensor 40 according to the present invention comprises a rotor cylinder 12 having a flat outer peripheral surface 12a and a stator cylinder 22 having an inner peripheral surface 22a having a thread groove. Is to be detected. That is, the air gap g shown in FIG. 2 which is a partially enlarged sectional view of the rotor cylinder and the stator cylinder of the thread groove pump portion.
Is to be detected. As is apparent from FIG. 2 and FIG. 3 which is a partial perspective view of the inner peripheral surface of the stator cylinder of the thread groove pump portion, the air gap g is formed between the outer peripheral surface 12 a of the rotor cylinder 12 and the stator cylinder 22. It is formed in a spiral shape in a substantially cylindrical gap between itself and the peripheral surface 22a.

In the hybrid turbomolecular pump shown in FIG. 1, the air gap sensor 40 is provided on the threaded inner peripheral surface 22a of the stator cylinder 22 as shown in FIG. As the air gap sensor 40, for example, a contact sensor or an eddy current sensor is used.

In order to prevent contact between the stator cylinder 22 and the rotor cylinder 12 due to the precession of the rotor 10, it is desirable to detect air gaps at a plurality of locations on the same circumference. Therefore, when using a plurality of air gap sensors 40 to improve the accuracy of gap detection,
These are arranged on the inner peripheral surface 22a with a thread groove of the stator cylinder 22 at predetermined intervals in the circumferential direction.

Further, since the lower end of the rotor cylinder 12 is farthest from the rotor shaft 31, when an abnormal touching occurs, the lower end is largely displaced as compared with the other parts, and may come into contact with the stator. High in nature. Therefore, the air gap sensor 40 is disposed on the inner peripheral surface near the lower end of the stator cylinder 22, thereby improving the reliability of gap detection.

The air gap sensor 40 includes a contact sensor 41
In the case of using the contact sensor 41, a pair of contacts 41a and 41b constituting the contact sensor 41 are arranged on the inner peripheral surface 22a of the stator cylinder 22 at a predetermined minute interval in the circumferential direction as shown in FIG. That is, the air gap sensor having the first contact 41a is arranged in the thread groove B, and the air gap sensor having the second contact 41b is arranged in the thread A. The contact portions are respectively a stator cylinder 22 and a rotator cylinder 12.
Are arranged on the inner circumferential surface 22a of the stator cylinder 22 so as to be on the same circumference in the gap between them, that is, at the same distance from the central axis of the stator cylinder 22 to the respective contact points. Therefore, the second contact 41b slightly protrudes from the thread A, and the first contact 41a protrudes considerably from the thread groove B. Thus, when the rotor 10 is supported at the normal position, the interval between the outer peripheral surface of the rotor cylinder 12 and each contact is the same.

Since the contact sensor 41 is disposed as described above, when the cylindrical body 12 of the rotor 10 made of metal such as aluminum contacts the contact sensor 41 on the side of the stator cylinder 22, each contact 41 a of the contact sensor 41 is provided. And 41b are conducted to generate a detection signal. This detection signal indicates that the air gap of the thread groove pump portion has become abnormally small, and thus the risk of contact between the inner peripheral surface of the rotor cylinder and the inner peripheral surface of the stator cylinder 22 has increased. ing.

The air gap sensor 40 includes an eddy current sensor 4
2 can be used. In this case, the eddy current sensor 42
Is installed on the threaded inner peripheral surface 22 a of the stator cylinder 22 in the same manner as the contact sensor 41. Unlike the contact sensor 41, the eddy current sensor 42 can detect the size of the air gap g and the air gap value.

FIG. 4 is a block diagram of a contact prevention device constituted by using an eddy current sensor 42 as the air gap sensor 40, and FIG. 5 is a flowchart of the operation thereof. In FIG. 4, a contact prevention device includes an eddy current sensor 42 for detecting an air gap, and a CP for performing various calculations and controls according to a program.
U43, a memory 44 for storing programs and data, a setting device 45 as an input means for setting installation values and the like, and an interlock circuit 46 for urgently stopping the operation of the vacuum pump
It is composed of

When the contact prevention device starts (101), the CPU 43 reads the air gap value from the eddy current sensor 42 and stores it in the memory 44 (102). Next, C
The PU 43 reads the set value and the air gap value from the memory 44 and compares them (103). As a result of the comparison, when it is determined that the air gap value is equal to or less than the set value, the interlock circuit is operated, the operation of the vacuum pump is stopped immediately (104), and the operation is terminated (105). Note that an alarm may be provided in the contact prevention device so that an alarm is issued when the air gap value becomes equal to or less than the set value. In addition, a simple contact prevention device that uses the contact sensor 41 as the air gap sensor, detects that the inner peripheral surface 12a of the rotor cylinder 12 has contacted the contact points 41a and 41b of the sensor unit, and generates an alarm, can also be configured. .

The present invention has been described above by applying the present invention to a vacuum pump having a thread groove pump portion having a thread groove formed on the stator side. However, the screw is formed on the outer peripheral surface of the cylindrical body of the rotor. The present invention can also be applied to a vacuum pump having a thread groove pump portion whose outer peripheral surface is opposed to the flat inner peripheral surface of the cylindrical body of the stator and maintains a predetermined air gap therebetween.

The present invention can also be applied to a vacuum pump in which the rotor is supported by mechanical bearings such as rolling bearings and sliding bearings. It goes without saying that the present invention can be applied to all vacuum pumps including turbo molecular pumps and drag pumps.

[0030]

According to the present invention, in a vacuum pump having a thread groove pump portion, an air gap sensor is provided at a predetermined position on the inner peripheral surface of the stator cylinder, so that the outer peripheral surface of the rotor cylinder and the stator cylinder can be removed. The gap between the air gap and the inner peripheral surface can be directly and reliably detected. Further, by operating the interlock using the output signal of the air gap sensor, the contact between the rotor side and the stator side can be reliably prevented. Therefore, the reliability and durability of the vacuum pump having the thread groove pump section were improved.

Further, since the air gap sensor itself can be easily obtained and the number of steps for installing the air gap sensor in the thread groove pump portion can be reduced, the manufacturing cost of the vacuum pump to which the present invention is applied increases. There is almost no practical effect.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a combined type turbo molecular pump, which is a vacuum pump configured by applying the present invention, in which a turbine blade section and a thread groove pump section are combined.

FIG. 2 is a partially enlarged sectional view of a rotor cylinder and a stator cylinder of a thread groove pump section.

FIG. 3 is a partial perspective view of the inner peripheral surface of a stator cylinder of a thread groove pump section.

FIG. 4 is a block diagram of one embodiment of a contact prevention device.

FIG. 5 is a flowchart of the operation of the contact prevention device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rotor 11 Rotor blade 12 Rotor cylinder 12a Flat outer peripheral surface 20 Stator 21 Stator blade 22 Stator cylinder 22a Threaded inner peripheral surface 30 Magnetic bearing device 31 Rotor shaft 32 First radial magnetic bearing 32a Radial electromagnet 32b Radial direction Displacement sensor 33 Second radial magnetic bearing 33a Radial electromagnet 33b Radial displacement sensor 34 First thrust magnetic bearing 35 Second thrust magnetic bearing 36 Axial displacement sensor 37 Touch down bearing 38 High frequency motor 40 Gap sensor 41 Contact sensor 41a First Contact 41b Second contact 42 Eddy current sensor 43 CPU 44 Memory 45 Setting device 46 Interlock circuit

Claims (6)

[Claims] 1. A vacuum comprising a rotor cylinder and a stator cylinder, and having a thread groove pump portion having a thread formed on one of an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder. A vacuum, wherein the pump is provided with an air gap sensor for detecting an air gap between an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder at a predetermined position on an inner peripheral surface of the stator cylinder. pump. 2. The vacuum pump according to claim 1, wherein a plurality of said air gap sensors are arranged on the inner peripheral surface of said stator cylinder at predetermined intervals in a circumferential direction. 3. The vacuum pump according to claim 1, wherein the air gap sensor is provided on an inner peripheral surface near a lower end of the stator cylinder. 4. The air gap sensor according to claim 1, wherein the air gap sensor is a contact sensor having a pair of contacts arranged on the inner circumferential surface of the stator cylinder at a predetermined minute interval in a circumferential direction. 1 vacuum pump. 5. The vacuum pump according to claim 1, wherein said air gap sensor is an eddy current sensor. 6. A vacuum comprising a rotor cylinder and a stator cylinder, and having a thread groove pump portion having a thread formed on one of an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder. In the pump, an air gap sensor that detects an air gap between an outer peripheral surface of the rotor cylinder and an inner peripheral surface of the stator cylinder, a memory that stores an air gap value detected by the air gap sensor,
A contact prevention device comprising: a discriminator that compares the detected air gap value with a set value; and an interlock circuit that activates an interlock when the discriminator determines that the detected air gap value is equal to or less than a set value. A vacuum pump comprising a device.