JP4965596B2 - Turbo type vacuum pump - Google Patents

Description

  The present invention relates to a turbo type vacuum pump, and more particularly to a turbo type vacuum pump including a magnetic bearing device that supports a rotating shaft in a non-contact manner by using a magnetic attraction force of an electromagnet.

  Since the magnetic bearing is a bearing that can support a floating body such as a rotating shaft in a non-contact manner, it can be used for, for example, a turbo molecular pump or the like to perform high-speed rotational movement. Such a magnetic bearing has various features such as no problem of bearing wear and maintenance-free since no lubricating oil is required. Such magnetic bearings include a radial active magnetic bearing that actively controls the floating position in the radial direction of the rotating shaft, and an axial active magnetic bearing that actively controls the floating position in the axial direction of the rotating shaft. A conventional example in which such a magnetic bearing is applied to a turbo vacuum pump is shown in FIGS.

  1 to 3, reference numeral 1 is a rotating shaft, reference numerals 2a to 2c are rotating blades attached to the rotating shaft 1, and reference numerals 3a to 3c are fixed blades arranged so as to face the rotating blades 2a to 2c, respectively. is there. The fixed blades 3a to 3c are attached to the inner surface of the pump stator 11, and their relative positions are fixed by spacers 4a and 4b. Reference numerals 5a and 5b denote axial active magnetic bearings for magnetically levitating the rotary shaft 1 in the axial direction via the magnetic bearing target 16, reference numeral 6 denotes an axial displacement sensor attached near the end of the rotary shaft 1, and reference numeral 7 denotes The sensor target is attached to the end of the rotary shaft 1 so as to face the axial displacement sensor 6. The displacement of the rotating shaft 1 is detected by an axial displacement sensor 6, and the rotating shaft 1 is supported at a predetermined position by the axial active magnetic bearings 5a and 5b based on the output signal of the axial displacement sensor 6. Although not shown, generally a radial active magnetic bearing for magnetically levitating the rotary shaft 1 in the radial direction is provided.

  Reference numeral 8A denotes a motor rotor attached to the central portion of the rotary shaft 1, reference numeral 8B denotes a motor stator that rotates the motor rotor 8A integrally with the rotary shaft 1, reference numerals 9a and 9b denote protective bearings (touch-down bearings), and reference numeral 10 denotes a fixed blade. It is a heater that heats 3a to 3c and spacers 4a and 4b. Reference numeral 12 denotes a cooling jacket that cools a portion of the pump stator 11 where the motor stator 8B and the axial active magnetic bearings 5a and 5b are positioned. Reference numeral 13a denotes a temperature detection thermistor attached to the winding of the motor stator 8B. Reference numeral 13b. Is a temperature detection thermistor attached to the winding of the axial active magnetic bearing 5a. The pump stator 11 is formed with an intake port 14 located on the upstream side of the rotary blade 2a and an exhaust port 15 located on the downstream side of the rotary blade 2c.

  The turbo vacuum pump having the above configuration is widely used in the semiconductor manufacturing process, and various reaction gases used in the semiconductor manufacturing process are exhausted by the turbo vacuum pump. In recent years, the amount of the reaction gas tends to increase due to an increase in the size of a semiconductor wafer, and accordingly, a semiconductor manufacturing apparatus is also increasing in size. Similarly, as the amount of reaction gas increases, the turbo vacuum pump is also increased in size, and further downsizing of the turbo vacuum pump is required. From such a requirement, the gap between the rotor blades 2a to 2c and the fixed blades 3a to 3c is made further smaller so that a large pressure difference is obtained between the intake port 14 and the exhaust port 15, and high exhaust Development of turbo-type vacuum pumps that achieve performance is underway.

  In general, the fixed blades 3a to 3c and the spacers 4a and 4b are heated to a high temperature by the heater 10 in order to prevent products generated during the semiconductor manufacturing process from adhering to the inside of the pump. For this reason, the radiant heat is transmitted to the rotating shaft 1 and the temperature of the rotating shaft 1 rises. In addition, the heat of the reaction gas that has been heated during the process and the frictional heat between the rotor blades 2a to 2c and the reaction gas are conducted to the rotating shaft 1, and the rotating shaft 1 reaches a high temperature over its entire length. Since the rotary shaft 1 is magnetically levitated by the axial active magnetic bearings 5a and 5b, the rotary shaft 1 is not in contact with the pump stator 11, and the rotary shaft 1 is placed in a vacuum atmosphere. For this reason, there is little heat dissipation from the rotating shaft 1, Therefore The rotating shaft 1 becomes very high temperature.

  On the other hand, the pump stator 11 is cooled by a cooling jacket 12 in order to prevent a temperature rise in a portion where the motor stator 8B and the axial active magnetic bearings 5a and 5b are arranged. As a result, the temperature difference between the rotary shaft 1 and the pump stator 11 becomes large, and the difference between the length L1 of the thermally expanded rotary shaft 1 and the length L2 of the pump stator 11 becomes large.

  Further, the axial displacement sensor 6 is disposed only in the vicinity of the other end of the rotating shaft 1 because of the structure of the turbo vacuum pump in which one end of the rotating shaft 1 is located at the intake port 14. For this reason, the axial displacement sensor 6 is normally disposed at a position away from the rotary blades 2a to 2c and the fixed blades 3a to 3c. As shown in FIG. 2, the axial active magnetic bearings 5a and 5b are controlled so that the gap dr between the axial displacement sensor 6 and the sensor target 7 is always constant, so that the rotary shaft 1 is based on the position of the sensor target 7. As shown in FIG. Then, since the temperature difference between the rotating shaft 1 and the pump stator 11 is large as described above, the elongation rates due to the thermal expansion of L1 and L2 are greatly different, and the rotating blades 2a to 2c and the fixed blades 3a to 3c are different. The gap dg narrows as the temperature of the rotary shaft 1 rises. As a result, if the gap dg between the rotary blades 2a to 2c and the fixed blades 3a to 3c is reduced in order to improve the exhaust performance of the turbo vacuum pump, they may come into contact during rotation. For this reason, it is necessary to ensure a gap of a certain level or more, which hinders the high exhaust performance of the turbo vacuum pump.

Ｎ：導線の巻数、Ｒｍ１：コアの磁気抵抗、Ｒｍ２：コイルとセンサターゲットとのギャップの磁気抵抗 For the axial displacement sensor 6 described above, a coil having a structure in which a conductive wire is wound around a magnetic material (core) such as a ferrite material or a laminated thin silicon steel plate is generally used because of a durability problem or the like. Such an axial displacement sensor is an inductive or eddy current displacement sensor that utilizes a change in impedance of a coil, and it is known that its magnetic permeability changes as the core temperature changes.
In general, the inductance Lc of the coil is expressed by the following equation.

N: number of turns of the conductor, Rm1: magnetoresistance of the core, Rm2: magnetoresistance of the gap between the coil and the sensor target

μ_０：真空透磁率、Ｌｅ：コアの実効磁路長、δ：ギャップ長さ、μ_Ｃ：コアの透磁率、Ａｅ：コアの実効断面積 The magnetic resistance Rm1 of the core and the magnetic resistance Rm2 of the gap between the coil and the sensor target are expressed by the following equations, respectively, when the leakage magnetic flux is ignored.

μ ₀ : Vacuum permeability, Le: Effective magnetic path length of core, δ: Gap length, μ _C : Core permeability, Ae: Effective cross-sectional area of core

Ｌｃ：コイルのインダクタンス、Ｒｃ：巻線の抵抗 The impedance Z _L of the coil is expressed by the following equation.

Lc: Coil inductance, Rc: Winding resistance

  As apparent from the equations (1) and (2), when the magnetic permeability of the core changes, the inductance changes, and the impedance changes from the equation (4), resulting in an error in the detected value of the axial displacement sensor. Will occur. In addition, a magnetic material such as a ferrite material generally has a characteristic that the magnetic permeability changes suddenly near the Curie temperature at which the material becomes paramagnetic. For this reason, when the temperature of the axial displacement sensor becomes higher than 100 ° C. and approaches the Curie temperature, the error further increases. As described above, when the gap between the rotary blades 2a to 2c and the fixed blades 3a to 3c is reduced, there is a problem that they come into contact with each other due to this error, and the axial displacement sensor is attached to the high temperature portion of the vacuum pump. I couldn't.

  In general, the change in the gap between the sensor target and the core and the change in the impedance are not directly proportional to each other from equations (1) to (4). The narrower the gap, the steeper the change in impedance. As it becomes larger, the change in impedance becomes gentler. Therefore, in order to accurately control the magnetic levitation position of the rotating shaft 1 in the axial direction using the axial displacement sensor 6, it is necessary to correct the characteristic curve of the sensor target displacement amount-the output value of the axial displacement sensor to a straight line. It was.

  In FIG. 2, the axial displacement sensor 6 is installed on the axis center line of the rotating shaft 1. On the other hand, in the example shown in FIG. 3, the axial displacement sensor 6 is installed at a position deviating from the axial center line of the rotating shaft 1 and is disposed so as to face the sensor target 7 perpendicular to the rotating shaft 1. As shown in FIG. 3, when the axial displacement sensor 6 is installed at a position other than the axis center line of the rotation shaft 1, the axial displacement sensor 6 is separated from the rotation center of the rotation shaft 1. For this reason, the gap between the sensor target 7 and the axial displacement sensor 6 greatly changes as indicated by dr1 and dr2 shown in FIG. 3 due to the swinging of the rotary shaft 1 due to the unbalance of the rotary shaft 1 (inclination of the rotary shaft 1). Will do. The axial displacement sensor 6 detects this gap, and the axial active magnetic bearings 5a and 5b are controlled based on the output value of the axial displacement sensor 6, so that the rotational shaft 1 is axially driven by the rotational speed component of the rotational shaft 1. There is a problem that vibration is applied in the direction, which is a factor that limits the installation position of the axial displacement sensor 6.

  In order to prevent contact between the rotor blades 2a to 2c and the fixed blades 3a to 3c due to thermal expansion, as shown in FIG. 1, temperature detecting thermistors 13a and 13b attached to the motor stator 8B and the axial active magnetic bearing 5a. Is used to estimate the temperature of the rotating shaft 1 and stop the operation of the pump before the rotating blades 2a to 2c and the fixed blades 3a to 3c come into contact with each other. However, since the temperature detection thermistors 13a and 13b indirectly measure the temperature of the rotary shaft 1, accurate temperature measurement cannot be performed, and contact between the rotary blades 2a to 2c and the fixed blades 3a to 3c is completely avoided. I couldn't.

  The present invention has been made in view of the above points, and it is possible to improve the exhaust performance by reducing the gap between the rotary blade and the fixed blade, and to accurately estimate the temperature and thermal expansion amount of the rotary shaft. It is another object of the present invention to provide a turbo vacuum pump that can be used and that can issue an alarm or stop operation before a rotor blade and a fixed blade contact each other.

In order to solve the above-described problem, one aspect of the present invention is arranged to face at least a pair of axial magnetic bearings that magnetically levitate a rotating shaft, a rotating blade attached to the rotating shaft, and the rotating blade. In a turbo vacuum pump including a fixed blade and a motor that rotationally drives the rotating shaft, an exhaust unit is configured by disposing the rotating blade and the fixed blade near one end of the rotating shaft. together with the a first axial displacement sensor for detecting the axial position of the rotary shaft, wherein the axial magnetic bearing, the other end portion of the protective bearings for restricting axial movement of said rotary shaft said rotary shaft A motion control unit is configured by being disposed in the vicinity, and a second axial displacement sensor for detecting the axial position of the rotating shaft is disposed in the vicinity of the exhaust unit.

  According to the present invention, even when the rotary shaft is thermally expanded, the gap between the axial magnetic bearing and the magnetic bearing target can be maintained substantially constant, and the axial magnetic bearing and the magnetic bearing target are in contact with each other. Can be prevented. Further, according to the present invention, it is possible to detect the temperature and thermal expansion amount of the rotating shaft based on the deviation between the output values of the first and second axial displacement sensors. It is also possible to switch between the first and second axial displacement sensors according to the rotational speed of the rotating shaft and the temperature of the rotating shaft.

A preferred embodiment of the present invention, the motion control unit is accommodated in the housing, before Symbol the second by controlling the temperature of the housing by the cooling mechanism based on the output value of the second axial displacement sensors The output value of the axial displacement sensor is controlled .
According to the present invention, the amount of thermal expansion of the rotating shaft can be calculated using the first and second axial displacement sensors. Then, based on the calculation result, it is possible to obtain a stable exhaust performance by controlling the cooling mechanism so that the gap between the rotary blade and the fixed blade is always in an optimum state.

In a preferred aspect of the present invention, an alarm operation is performed based on output values of the first axial displacement sensor and the second axial displacement sensor.
According to the present invention, by calculating the thermal expansion amount of the rotating shaft using the first and second axial displacement sensors, it is possible to perform an alarm operation before the rotating blade and the fixed blade contact each other. It is possible to prevent the mold vacuum pump from being damaged. The operation may be stopped before the rotating blades and the fixed blades contact each other.

A preferred embodiment of the present invention, the material constituting the front Symbol housing is characterized in that it has a larger linear expansion coefficient than the linear expansion coefficient of the material of the rotary shaft.
Usually, during operation of the turbo vacuum pump, the temperature of the rotating shaft is higher than the temperature of the housing. For this reason, due to the difference in thermal expansion between the rotating shaft and the housing, the gap between the second axial displacement sensor attached to the housing and the sensor target attached to the rotating shaft changes during operation. . According to the present invention, even when the temperature difference between the rotating shaft and the housing becomes large, the amount of thermal expansion between the rotating shaft and the housing can be made substantially equal. As a result, the gap between the second axial displacement sensor and the sensor target can be maintained constant.

In a preferred aspect of the present invention, a plurality of the rotary blades and the fixed blades are provided, and gaps formed between the plurality of rotary blades and the plurality of fixed blades are separated from the second axial displacement sensor. It is set so that it may become large.
According to the present invention, the plurality of gaps formed between the rotary blade and the fixed blade can be made equal to each other.

  A magnetic bearing device according to a reference example of the present invention includes at least a pair of axial magnetic bearings for magnetically levitating a rotating shaft, at least one axial displacement sensor for detecting an axially levitating position of the rotating shaft, and the axial displacement sensor And a magnetic bearing control device for controlling the exciting current of the axial magnetic bearing so that the rotating shaft magnetically levitates at a predetermined position based on the output value of the rotating shaft, and is concentric with the rotating shaft in the vicinity of a high temperature portion of the rotating shaft. This sensor target is provided, and the axial displacement sensor is disposed at a position facing the sensor target. In this reference example, in a magnetic bearing device that supports a rotating shaft in a high temperature state, the influence of thermal expansion of the rotating shaft due to high temperature is reduced, and the amount of run-out due to unbalance of the rotating shaft is superimposed on the output value of the axial displacement sensor. An object of the present invention is to provide a magnetic bearing device that can prevent the occurrence of the rotation and can attach an axial displacement sensor to a place other than the end of the rotating shaft and stably control the position of the rotating shaft in the axial direction. Is.

  According to the magnetic bearing device, the influence of the thermal expansion of the rotating shaft can be minimized. For example, when the magnetic bearing device is used in a turbo type vacuum pump, the axial displacement sensor is disposed in a region where the rotation shaft is at the highest temperature, that is, in the vicinity of the rotary blade and the fixed blade. With such an arrangement, the amount of displacement of the rotor blade is minimized, and contact between the rotor blade and the fixed blade can be prevented. Therefore, the clearance between the rotary blade and the fixed blade can be further reduced to improve the exhaust performance.

In the magnetic bearing device, when the axial magnetic bearing does not function, the protective bearing that supports the rotating shaft and / or the axial magnetic bearing may be disposed in the vicinity of a high temperature portion of the rotating shaft.
This prevents the contact between the rotating shaft and the protective bearing even when the rotating shaft is thermally expanded by arranging the protective bearing that supports the rotating shaft in the axial direction in the vicinity of the high temperature portion of the rotating shaft. Can do. Further, according to the present invention, the gap between the axial magnetic bearing and the magnetic bearing target attached to the rotating shaft can be set to be even narrower by arranging the axial magnetic bearing near the high temperature portion of the rotating shaft. . As a result, it is possible to reduce power consumption by reducing the current flowing through the drive coil of the axial magnetic bearing, and it is possible to reduce the diameter and number of turns of the drive coil and to reduce the size of the axial magnetic bearing.

In the magnetic bearing device, a plurality of the axial displacement sensors are provided, and each of the plurality of axial displacement sensors includes a coil, detects a displacement of the rotating shaft based on a change in impedance of the coil, and includes the plurality of the coils. A plurality of the coils may be connected in parallel and / or in series along the circumferential direction of the rotating shaft.
Further, in the magnetic bearing device, the axial displacement sensor includes a coil, detects a displacement of the rotating shaft based on a change in impedance of the coil, and moves a lead wire of the coil along a circumferential direction of the rotating shaft. It is good also as a structure wound.
Thereby, it is possible to prevent the amount of swing due to the unbalance of the rotating shaft from being superimposed on the output value of the axial displacement sensor, and the axial magnetic bearing can stably control the position of the rotating shaft in the axial direction. It becomes possible.

In the above-mentioned magnetic bearing device, an averaging device that provides a plurality of the axial displacement sensors, arranges the plurality of axial displacement sensors along the circumferential direction of the rotating shaft, and averages the output values of the plurality of axial displacement sensors. May be provided.
As a result, even when the axial displacement sensor is an optical type or the like, it is possible to prevent the amount of swing due to the unbalance of the rotating shaft from being superimposed on the output value of the axial displacement sensor. The position in the axial direction can be stably controlled.

In the magnetic bearing device, a plurality of the axial displacement sensors may be provided, and the plurality of axial displacement sensors may be disposed on both sides of the sensor target in the axial direction of the rotating shaft so as to sandwich the sensor target.
As a result, the characteristic curve of the sensor target displacement amount-axial displacement sensor output value can be corrected to a substantially straight line, so that the position of the rotating shaft in the axial direction can be accurately detected. Therefore, the rotary shaft can be stably magnetically levitated by the axial magnetic bearing. Further, even when the temperature of the core constituting the axial displacement sensor changes and the impedance fluctuates, it is possible to cancel the influence.

  A turbo vacuum pump according to another embodiment of the present invention includes at least a pair of axial magnetic bearings for magnetically levitating a rotating shaft, at least one axial displacement sensor for detecting an axially levitating position of the rotating shaft, A magnetic bearing control device that controls an exciting current of the axial magnetic bearing so that the rotary shaft magnetically levitates at a predetermined position based on an output value of the axial displacement sensor, a rotary blade attached to the rotary shaft, and the rotation An exhaust section provided with a fixed wing arranged to face the wing and a motor for rotationally driving the rotary shaft, and arranging the rotary wing and the fixed wing in the vicinity of one end of the rotary shaft And a motion control unit having the motor and the axial magnetic bearing is disposed on the other end side of the rotary shaft, and the axial control unit is disposed near the exhaust unit. Having a configuration of arranging the catcher Le displacement sensor.

  In the turbo type vacuum pump, the exhaust section composed of the rotor blades and the stationary blades is usually heated during operation due to heat generated by friction between the rotor blades and gas, heater heating for preventing product adhesion, and the like. According to the turbo type vacuum pump having the above-described configuration, the exhaust part that is at a high temperature and the motion control part configured by the axial magnetic bearing, the motor, and the like are structurally separated, and the axial magnetic bearing, the motor, etc. It is possible to protect the electrical component from high heat. Further, according to the turbo type vacuum pump having the above configuration, the axial displacement sensor for detecting the axial displacement of the rotating shaft is provided in the vicinity of the exhaust portion, and the rotating shaft is set in a predetermined axial direction based on the output value of the axial displacement sensor. By supporting the position, the base point of the extension of the rotating shaft can be used as the measurement point of the axial displacement sensor. As a result, the axial gap between the rotary blade and the fixed blade can be reduced, and as a result, the exhaust performance of the turbo vacuum pump can be improved and the operation can be stabilized.

In the turbo vacuum pump, the protective bearing and / or the axial magnetic bearing that supports the rotating shaft when the axial magnetic bearing does not function may be disposed in the vicinity of the exhaust part.
This prevents the contact between the rotating shaft and the protective bearing even when the rotating shaft is thermally expanded by arranging the protective bearing that supports the rotating shaft in the axial direction in the vicinity of the high temperature portion of the rotating shaft. Can do. In general, in a broadband turbo vacuum pump having a large pressure difference between the intake port and the exhaust port, a large axial force acts on the rotating shaft due to the pressure difference. According to the present invention, by arranging the axial magnetic bearing near the high temperature portion, the gap between the axial magnetic bearing and the magnetic bearing target attached to the rotary shaft can be set to be even narrower. As a result, the axial magnetic bearing can generate a magnetic attractive force corresponding to the force in the axial direction. Furthermore, it is possible to reduce power consumption by reducing the current flowing through the drive coil of the axial magnetic bearing, and it is possible to reduce the size of the drive coil and reduce the size of the turbo vacuum pump.

Further, in the turbo type vacuum pump, a plurality of the axial displacement sensors are provided, each of the plurality of axial displacement sensors includes a coil, detects a displacement of the rotating shaft based on a change in impedance of the coil, and A coil may be arranged along the circumferential direction of the rotating shaft, and the plurality of coils may be connected in parallel and / or in series.
Further, in the turbo type vacuum pump, the axial displacement sensor includes a coil, detects displacement of the rotating shaft based on a change in impedance of the coil, and guides the coil along the circumferential direction of the rotating shaft. May be wound around.
In the turbo type vacuum pump, a plurality of the axial displacement sensors are provided, the plurality of axial displacement sensors are arranged along a circumferential direction of the rotating shaft, and the output values of the plurality of axial displacement sensors are averaged. An averaging device may be provided.
In the turbo type vacuum pump, a plurality of the axial displacement sensors may be provided, and the plurality of axial displacement sensors may be disposed on both sides of the sensor target in the axial direction of the rotating shaft so as to sandwich the sensor target.

According to the present invention and the above reference example, the following excellent effects can be obtained.
(1) By disposing the axial displacement sensor near the portion where the rotating shaft becomes the highest temperature, that is, in the vicinity of the rotating blade and the fixed blade, the amount of displacement of the rotating blade can be minimized. Therefore, the clearance between the rotary blade and the fixed blade can be further reduced to improve the exhaust performance.
(2) By disposing a protective bearing that supports the rotating shaft in the axial direction in the vicinity of the high temperature portion of the rotating shaft, even if the rotating shaft is thermally expanded, contact between the rotating shaft and the protective bearing is prevented. Can do. Further, by disposing the axial magnetic bearing in the vicinity of the high temperature portion of the rotating shaft, the gap between the axial magnetic bearing and the magnetic bearing target attached to the rotating shaft can be set to be even narrower. As a result, it is possible to reduce power consumption by reducing the current flowing through the drive coil of the axial magnetic bearing, and it is possible to reduce the diameter and number of turns of the drive coil and to reduce the size of the axial magnetic bearing.

(3) It is possible to prevent the amount of swing due to the unbalance of the rotating shaft from being superimposed on the output value of the axial displacement sensor, and to control the position of the rotating shaft in the axial direction stably by the axial magnetic bearing. It becomes possible.
(4) Even when the axial displacement sensor is an optical type or the like, it is possible to prevent the amount of swing due to unbalance of the rotating shaft from being superimposed on the output value of the axial displacement sensor, and the axial magnetic bearing can rotate the rotating shaft. The position in the axial direction can be stably controlled.
(5) Since the characteristic curve of the sensor target displacement amount-axial displacement sensor output value can be corrected to a substantially straight line, the position of the rotating shaft in the axial direction can be accurately detected. Therefore, the rotary shaft can be stably magnetically levitated by the axial magnetic bearing. Further, even when the temperature of the core constituting the axial displacement sensor changes and the impedance fluctuates, it is possible to cancel the influence.

(6) In the turbo vacuum pump, electrical components such as axial magnetic bearings and motors having a low heat resistance are structurally separated from the exhaust part that becomes high temperature and the motion control part composed of axial magnetic bearings and motors, etc. Can be protected from high heat. In addition, an axial displacement sensor for detecting the axial displacement of the rotating shaft is provided near the exhaust portion, and the rotating shaft is extended by supporting the rotating shaft at a predetermined axial position based on the output value of the axial displacement sensor. Can be used as a measurement point of the axial displacement sensor. As a result, the axial gap between the rotary blade and the fixed blade can be reduced, and as a result, the exhaust performance of the turbo vacuum pump can be improved and the operation can be stabilized.

(7) The temperature and thermal expansion amount of the rotating shaft can be detected based on the deviation of the output values of two or more axial displacement sensors that are separated from each other in the axial direction. It is also possible to switch and use each axial displacement sensor according to the rotational speed of the rotating shaft and the temperature of the rotating shaft.
(8) By using two or more axial displacement sensors, the amount of thermal expansion of the rotating shaft can be calculated. Further, based on the calculation result, it is possible to obtain a stable pump performance by controlling the cooling mechanism so that the clearance between the rotor blade and the stationary blade of the turbo vacuum pump is always in an optimum state. .

(9) By calculating the amount of thermal expansion of the rotating shaft using two or more axial displacement sensors, it is possible to perform an alarm operation before the rotor blade and fixed blade contact, and the turbo vacuum pump is damaged. This can be prevented in advance.
(10) Provided is a turbo type vacuum pump that can stably levitate the rotating shaft without being affected by the thermal expansion of the rotating shaft, and can prevent contact between the rotating blade and the fixed blade. can do.

It is a schematic diagram which shows the conventional turbo type vacuum pump. It is a schematic diagram which shows the principal part of the turbo type vacuum pump shown in FIG. It is a schematic diagram which shows the other structural example of the conventional turbo type vacuum pump. It is a schematic diagram which shows the principal part of the turbo type pump which concerns on the 1st reference example of this invention. FIG. 5A is a schematic diagram showing a configuration example of an axial displacement sensor incorporated in a turbo type vacuum pump according to a second reference example of the present invention, and FIG. 5B is an axial view shown in FIG. It is a connection diagram of a displacement sensor. It is a graph which shows a mode that the inductance of the axial displacement sensor shown in FIG.5 (b) changes. FIG. 7A is a schematic diagram showing a configuration example of an axial displacement sensor incorporated in a turbo type vacuum pump according to a third reference example of the present invention, and FIG. 7B is shown in FIG. It is a connection diagram of an axial displacement sensor. It is a graph which shows a mode that the inductance of the axial displacement sensor shown in FIG.7 (b) changes. It is a schematic diagram which shows the axial displacement sensor and averaging process system which are integrated in the turbo type vacuum pump which concerns on the 4th reference example of this invention. FIG. 10A is a schematic diagram showing a configuration example of an axial displacement sensor incorporated in a turbo vacuum pump according to a fifth reference example of the present invention, and FIG. 10B is a connection diagram of the axial displacement sensor. FIG. 10 (c) is a connection diagram of an axial displacement sensor incorporated in the conventional turbo vacuum pump shown in FIG. It is a graph which shows the relationship between a displacement amount and the output of an axial displacement sensor. It is a schematic diagram which shows the principal part of the turbo type vacuum pump which concerns on the 6th reference example of this invention. It is a mimetic diagram showing a turbo type vacuum pump concerning an embodiment of the present invention. It is a schematic diagram which shows the magnetic bearing control apparatus integrated in the turbo type vacuum pump shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a schematic diagram showing the main part of the turbo pump according to the first reference example of the present invention. 4, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and duplicate explanations are omitted. As shown in FIG. 4, reference numeral 6 denotes an axial displacement sensor that detects displacement in the axial direction of the rotating shaft 1, and reference numeral 7 denotes a disk-shaped sensor target concentric with the rotating shaft 1 attached to the rotating shaft 1. . Reference numeral 11 schematically represents a pump stator (housing) that holds the axial magnetic bearings 5a and 5b, the fixed blades 3a to 3c, the spacers 4a and 4b, and the like.

  The axial displacement sensor 6 is fixed to the pump stator 11 and is disposed so as to face the sensor target 7. The axial displacement sensor 6 and the sensor target 7 are disposed in the vicinity of the rotor blades 2a to 2c. More specifically, the axial displacement sensor 6 and the sensor target 7 are located immediately downstream of the rotor blade 2c, and are disposed between the rotor blade 2c and the motor rotor 8A. The axial magnetic bearings 5 a and 5 b are connected to the magnetic bearing control device 17. The magnetic bearing control device 17 is configured to control the excitation current of the axial magnetic bearings 5a and 5b based on the output value of the axial displacement sensor 6 so that the rotary shaft 1 is magnetically levitated at a predetermined position. Reference symbol L1 ′ represents the length from the rotor blade 2a upstream of the rotating shaft 1 to the sensor target 7, and reference symbol L2 ′ represents the length from the fixed blade 3a upstream of the pump stator 11 to the axial displacement sensor 6. , L3 represents the length of the pump stator 11 from the axial displacement sensor 6 to the downstream end.

  Usually, the rotating shaft 1, the fixed blades 3a to 3c, and the spacers 4a and 4b are heated to high temperatures due to heat conduction of frictional heat with the heater 10 (see FIG. 1) and the reaction gas of the rotating blades 2a to 2c. For example, the temperature of the part of the rotary shaft 1 to which the rotary blades 2a to 2c are attached, the rotary blades 2a to 2c, the fixed blades 3a to 3c, and the spacers 4a and 4b are 150 to 250 ° C. On the other hand, since the pump stator 11 is cooled by a cooling jacket (cooling mechanism) 12 (see FIG. 1), the amount of thermal expansion of the pump stator 11 is small. For example, the temperature of the pump stator 11 is 50 to 100 ° C., and the portion of the rotary shaft 1 located in the vicinity of the axial magnetic bearings 5a and 5b is 100 to 150 ° C. Even if the pump stator 11 is thermally expanded, since the axial displacement sensor 6 is attached in the vicinity of the rotary blades 2a to 2c, the change in L3 is caused in the gap dg between the rotary blades 2a to 2c and the fixed blades 3a to 3c. Has no effect.

  The rotating shaft 1 extends in the direction (up and down direction in FIG. 4) toward the upstream end and the downstream end of the rotating shaft 1 with the position of the sensor target 7 as a base point due to thermal expansion, and the change in L1 ′ is the rotating blade 2a. Will affect the gap dg between ˜2c and fixed wings 3a-3c. However, as described above, the fixed blades 3a to 3c and the spacers 4a and 4b are also heated to high temperatures due to the radiant heat of the heater 10, the reaction gas, and the rotor blades 2a to 2c. As a result, the thermal expansion amounts of L1 ′ and L2 ′ are almost equal. Become. Therefore, even if L1 'and L2' change due to a temperature rise, the amount of change in the gap dg is significantly reduced. Thereby, even if the gap dg is further narrowed, there is no possibility that the rotary blades 2a to 2c and the fixed blades 3a to 3c come into contact with each other, and the exhaust performance can be improved.

  FIG. 5A is a schematic diagram showing a configuration example of an axial displacement sensor incorporated in a turbo type vacuum pump according to a second reference example of the present invention, and FIG. 5B is an axial view shown in FIG. It is a connection diagram of a displacement sensor. FIG. 6 is a graph showing how the inductance of the axial displacement sensor shown in FIG. Note that the configuration of this reference example that is not specifically described is the same as that of the first reference example, and therefore redundant description thereof is omitted.

  As shown in FIG. 5A, a disc-shaped sensor target 7 is attached to the rotary shaft 1, and axial displacement sensors 601 a and 601 b are disposed in the vicinity of the sensor target 7. These axial displacement sensors 601a and 601b are induction type or eddy current type displacement sensors each formed of a coil. The axial displacement sensors 601 a and 601 b are arranged at positions shifted by 180 ° along the circumferential direction of the rotary shaft 1 so as to face the sensor target 7. The axial displacement sensors 601a and 601b are located in the vicinity of the rotary blades 2a to 2c (see FIG. 4).

  As shown in FIG. 5B, the two axial displacement sensors 601a and 601b are connected in series. Normally, when the rotary shaft 1 is swung around due to imbalance between the rotary shaft 1 and the rotor blades 2a to 2c, the inductances Lc-a and Lc-b of the axial displacement sensors 601a and 601b are close to sine waves as shown in FIG. It changes with the waveform, and the phases are shifted from each other by 180 °. By connecting these axial displacement sensors 601a and 601b in series as shown in FIG. 5B, the inductances Lc-a and Lc-b are combined to form a combined inductance Lc '. Accordingly, the combined inductance Lc ′ can be approximated to an axial displacement component obtained by canceling the radial swing component of the rotating shaft 1.

  FIG. 7A is a schematic diagram showing a configuration example of an axial displacement sensor incorporated in a turbo type vacuum pump according to a third reference example of the present invention, and FIG. 7B is shown in FIG. It is a connection diagram of an axial displacement sensor. FIG. 8 is a graph showing how the inductance of the axial displacement sensor shown in FIG. 7B changes. Note that the configuration of this reference example that is not specifically described is the same as that of the first reference example, and therefore redundant description thereof is omitted.

  As shown in FIG. 7A, the axial displacement sensors 602a, 602c, 602b, and 602d are arranged to face one side of the sensor target 7 attached to the rotating shaft 1. These axial displacement sensors 602a, 602c, 602b, and 602d are induction type or eddy current type displacement sensors each composed of a coil. The axial displacement sensors 602a, 602c, 602b, and 602d are arranged with a 90 ° shift in the circumferential direction of the rotary shaft 1, and are arranged in the vicinity of the rotary blades 2a to 2c (see FIG. 4). As shown in FIG. 7B, the axial displacement sensors 602a and 602b and the axial displacement sensors 602c and 602d facing each other at an interval of 180 ° are connected in series, and two sets of axial displacement sensors 602a, 602a, 602b and axial displacement sensors 602c and 602d are connected in parallel.

  In FIG. 7A, when the rotary shaft 1 is swung around due to the unbalance of the rotary shaft 1 and the rotor blades 2a to 2c (see FIG. 4), the inductance Lc− of each axial displacement sensor 602a, 602c, 602b, 602d. As shown in FIG. 8, a, Lc-c, Lc-b, and Lc-d change while drawing a waveform close to a sine wave, and are out of phase with each other by 90 °. By connecting the axial displacement sensors 602a, 602c, 602b, and 602d as shown in FIG. 7B, the inductances Lc-a, Lc-c, Lc-b, and Lc-d are combined to form a combined inductance Lc ′. Thus, the combined inductance Lc ′ can be brought close to the axial displacement component obtained by canceling the radial swing component of the rotating shaft 1.

  By increasing the number of axial displacement sensors (coils) to 2, 4, 8,... And connecting these axial displacement sensors in series and / or in parallel, the conical motion and parallel motion of the rotating shaft 1 are combined. It is clear that the radial displacement component can be canceled even more with respect to the complicated radial swing. In this way, by arranging an even number of axial displacement sensors at equal intervals along the circumferential direction of the rotating shaft 1, the position of the rotating shaft 1 in the axial direction can be accurately detected. In addition, the conducting wire of an axial displacement sensor (coil) may be wound along the circumferential direction of the rotating shaft 1, and the displacement may be detected over the whole surface of the sensor target 7 in the circumferential direction.

  FIG. 9 is a schematic diagram showing an axial displacement sensor and an averaging processing system incorporated in a turbo vacuum pump according to a fourth reference example of the present invention. Note that the configuration of this reference example that is not specifically described is the same as that of the first reference example, and therefore redundant description thereof is omitted. A plurality of grooves 7 a extending in the radial direction are formed on one surface of the disk-shaped sensor target 7. A rotational speed sensor 22 is disposed at a position facing the groove 7a, and the rotational speed of the rotary shaft 1 is detected by the rotational speed sensor 22. Reference numerals 6E and 6F denote optical axial displacement sensors, and these axial displacement sensors 6E and 6F are arranged at equal intervals along the circumferential direction of the rotary shaft 1 in proximity to the sensor target 7.

  The axial displacement sensors 6E and 6F are connected to the sensor circuit devices 20a and 20b, respectively. The sensor circuit devices 20a and 20b convert the size of the gap between the axial displacement sensors 6E and 6F and the sensor target 7 into a voltage signal, and the voltage signal is transmitted as an analog signal to the A / D converters 21a and 21b, respectively. . The voltage signals (analog signals) from the sensor circuit devices 20a and 20b are converted into digital signals by the A / D converters 21a and 21b, and then input to the averaging device (arithmetic device) 24. On the other hand, the output signal of the rotation speed sensor 22 is sent to the rotation speed conversion device 23, and the rotation speed conversion device 23 converts the output signal of the rotation speed sensor 22 into a voltage pulse. The axial displacement sensors 6E and 6F are arranged with an interval of 180 °.

  In such a configuration, the axial displacement of the rotating shaft 1 including the radial swing component is detected by the two axial displacement sensors 6E and 6F and converted into voltage signals by the sensor circuit devices 20a and 20b, respectively. Then, it is transmitted to the A / D converters 21a and 21b. Voltage signals (analog signals) from the sensor circuit devices 20a and 20b are converted into digital signals by the A / D converters 21a and 21b and input to the averaging device 24. The averaging device 24 calculates the displacement of the rotating shaft 1 only in the axial direction by averaging the two digital signals (the output signals of the axial displacement sensors 6E and 6F). At this time, the rotational speed of the rotary shaft 1 detected by the rotational speed sensor 22 is input to the averaging device 24 through the rotational speed converter 23, and only the rotational frequency components of the rotary shaft 1 are output signals from the axial displacement sensors 6E and 6F. It is possible to obtain a more accurate displacement in the axial direction of the rotary shaft 1.

  FIG. 10A is a schematic diagram showing a configuration example of an axial displacement sensor incorporated in a turbo vacuum pump according to a fifth reference example of the present invention, and FIG. 10B is a connection diagram of the axial displacement sensor. FIG. 10 (c) is a connection diagram of an axial displacement sensor incorporated in the conventional turbo vacuum pump shown in FIG. Note that the configuration of this reference example that is not specifically described is the same as that of the first reference example, and therefore redundant description thereof is omitted.

  The axial displacement sensors 604 a, 604 b, 604 c, and 604 d are disposed on both sides of the sensor target 7 in the axial direction of the rotary shaft 1. That is, the axial displacement sensors 604a and 604c are disposed to face each other so as to sandwich the sensor target 7, and similarly, the axial displacement sensors 604b and 604d are disposed to face each other so as to sandwich the sensor target 7. The axial displacement sensors 604a and 604c and the axial displacement sensors 604b and 604d forming a pair are arranged in the vicinity of the rotary blades 2a to 2c (see FIG. 4) with a 180 ° shift in the circumferential direction of the rotary shaft 1.

  The axial displacement sensors 604a to 604d are inductive or eddy current type displacement sensors each composed of a coil, and these axial displacement sensors (coils) 604a to 604d are connected in series as shown in FIG. It is connected. The AC signal source OSC is connected to the axial displacement sensors 604a to 604d connected in series, and the capacitor Cx is connected in parallel to the axial displacement sensors 604a to 604d. The capacitor Cx is adjusted so as to resonate with the total inductance of the axial displacement sensors 604a to 604d, thereby increasing the sensitivity of the axial displacement sensors 604a to 604d. Voltage dividers Rx1 and Rx2 that divide the output of the AC signal source OSC are connected in series with each other, and these voltage dividers Rx1 and Rx2 are connected in parallel with the axial displacement sensors 604a to 604d. Reference numeral 31 denotes a differential amplifier, and reference numeral 30 denotes a synchronous detection device that converts a displacement signal from the differential amplifier 31 into a direct current.

  In FIG. 10C, the symbol Ld is a fixed inductance, and this fixed inductance Ld is connected in series with the axial displacement sensor 6. The capacitor Cx is connected in parallel with the fixed inductance Ld and the axial displacement sensor 6 connected in series. The capacitor Cx is adjusted so as to resonate with the total inductance of the axial displacement sensor 6 and the fixed inductance Ld. In addition, in FIG.10 (c), the structural member which attached | subjected the code | symbol same as FIG.10 (b) represents the same structural member.

  FIG. 11 is a graph showing the relationship between the amount of displacement and the output of the axial displacement sensor. In the conventional axial displacement sensor 6 shown in FIG. 10C, the relationship between the displacement amount of the sensor target 7 and the output of the axial displacement sensor 6 is as shown by a line la and is not a straight line. In general, since the fixed inductance Ld is at a position away from the axial displacement sensor 6, when the temperature of the axial displacement sensor 6 rises, the line la changes as a line lb.

  In the conventional example shown in FIG. 1, one axial displacement sensor 6 is arranged on one side of the sensor target 7, whereas in FIG. 10A, axial displacement sensors 604 a to 604 d are arranged so as to sandwich the sensor target 7. Has been placed. Accordingly, the impedance of the axial displacement sensors 604a + 604b and the impedance of the axial displacement sensors 604c + 604d change nonlinearly so as to cancel each other. Thereby, the relationship between the displacement amount of the sensor target 7 and the outputs of the axial displacement sensors 604a to 604d becomes a line lc in FIG. 11 and can be made substantially straight. Furthermore, when the temperature of the axial displacement sensors 604a to 604d rises, the impedance of all the axial displacement sensors (coils) 604a to 604d in FIG. The divided voltage does not change at point b. As a result, the relationship between the displacement amount of the sensor target 7 and the outputs of the axial displacement sensors 604a to 604d becomes the same as the line lc in FIG. 11, and the influence of the temperature change can be canceled.

  FIG. 12 is a schematic diagram showing a main part of a turbo vacuum pump according to a sixth reference example of the present invention. In FIG. 12, constituent members denoted by the same reference numerals as those in FIG. 1 indicate the same or corresponding constituent members, and redundant description thereof is omitted. The configuration of this reference example that is not particularly described is the same as that of the first reference example. As shown in FIG. 12, a ring-shaped sensor target 7 is attached to the bottom of the rotary blade 2 c, and a plurality of axial displacement sensors 6 are arranged along the circumferential direction of the rotary shaft 1 so as to face the sensor target 7. It is arranged at equal intervals. The axial magnetic bearings 5 a and 5 b are arranged immediately downstream of the axial displacement sensor 6. Further, the protective bearing 9 a that restricts the movement of the rotary shaft 1 in the axial direction and the radial direction is disposed at a radially inner position of the axial displacement sensor 6. As described above, the axial magnetic bearings 5a and 5b, the axial displacement sensor 6, the sensor target 7, and the protective bearing 9a are arranged in the vicinity of the rotor blades 2a, 2b, and 2c that are at a high temperature. Symbol L4 represents the length from the axial displacement sensor 6 of the rotating shaft 1 to the magnetic bearing target 16, and symbol L5 represents the length from the magnetic bearing target 16 of the rotating shaft 1 to the downstream end of the rotating shaft 1. To express.

  The rotating shaft 1 extends vertically along the axial direction with the position of the sensor target 7 as a base point due to thermal expansion. As a result, the gap dm between the magnetic bearing target 16 and the upstream axial magnetic bearing 5a increases, and at the same time, the gap dm 'between the magnetic bearing target 16 and the downstream axial magnetic bearing 5b decreases. However, with regard to the influence of thermal expansion, only L4 needs to be considered, and L5 can be ignored. Therefore, the decrease in the gap dm ′ is smaller than the conventional turbo vacuum pump shown in FIG. 1, and the total gap dm + dm ′ is reduced. Even if it sets, the magnetic bearing target 16 and the axial magnetic bearing 5b do not contact.

Ｓ：鉄心の断面積 In the case of a broadband turbo booster pump or the like, the differential pressure between the intake port pressure P1 and the exhaust port pressure P2 is very large, and the rotary shaft 1 is lifted upward toward the intake port 14 by this differential pressure. At this time, since the rotary shaft 1 is pulled back downward by the downstream axial magnetic bearing 5b, the axial magnetic bearing 5b consumes a considerable amount of power.
Here, the magnetic attraction force F of the magnetic bearing is expressed by the following equation when the magnetic permeability and leakage flux of the iron core (core) are ignored.

S: Cross-sectional area of the iron core

Ｎ：巻線のターン数、Ｉ：コイルに流す電流、ｄｍ：磁極と磁気軸受ターゲットとの隙間 The magnetic flux density B is expressed by the following formula.

N: number of turns of winding, I: current flowing in coil, dm: gap between magnetic pole and magnetic bearing target

  As is clear from the equations (5) and (6), when the gap dm 'decreases, the magnetic attractive force increases, and the axial magnetic bearings 5a and 5b can exert a further magnetic attractive force. Further, when the magnetic attractive force is constant, the number of turns of the winding and the current flowing through the coil can be reduced by reducing the gap dm ′, thereby reducing the power consumption of the axial magnetic bearings 5a and 5b. It becomes possible. Accordingly, since the number of turns and the current are reduced, the axial magnetic bearings 5a and 5b can be reduced in size.

  FIG. 13 is a schematic diagram showing a turbo vacuum pump according to an embodiment of the present invention. The difference between this embodiment and the sixth reference example shown in FIG. 12 is that the first axial displacement sensor, the sensor target, the axial magnetic bearing, and the protective bearing that regulates the movement in the axial direction are the ends of the motion control unit. And a second axial displacement sensor and a sensor target are provided in the vicinity of the exhaust portion. Hereinafter, the configuration of the present embodiment will be described in detail.

  As shown in FIG. 13, the turbo vacuum pump has a plurality of rotor blades 52A to 52C (hereinafter, appropriately referred to as rotor blades 52) in an upper housing (upper pump stator) 51 having an intake port 51A and an exhaust port 51B. And a plurality of fixed wings 53A to 53C (hereinafter, referred to as fixed wings 53 as appropriate). The rotary blade 52 and the fixed blade 53 constitute an exhaust part 90.

  An upper radial magnetic bearing 56 and a lower radial magnetic bearing 57 are disposed on both sides of the motor 55, and the rotary shaft 54 is supported in the radial direction by the upper radial magnetic bearing 56 and the lower radial magnetic bearing 57. A disc-shaped magnetic bearing target 58c is concentrically fixed to the lower portion of the rotating shaft 54, and a pair of axial magnetic bearings 58a and 58b (hereinafter, appropriately referred to as an axial magnetic bearing 58) is sandwiched between the magnetic bearing targets 58c. Has been placed. The rotating shaft 54 is supported in the axial direction by an axial magnetic bearing 58. The magnetic bearings 56, 57, and 58 are all active magnetic bearings.

  A sensor target 61 is attached to the downstream end of the rotating shaft 54, and a first axial displacement sensor 59 is attached to the lower housing (lower pump stator) 63 so as to face the sensor target 61. A sensor target 62 is attached to the rotary shaft 54 in the vicinity of the rotary blade 52, and a plurality of second axial displacement sensors 60 are arranged in the circumferential direction of the rotary shaft 54 so as to face the sensor target 62. Are arranged at equal intervals.

  An upper protective bearing (upper touchdown bearing) 65 is disposed in the vicinity of the upper radial magnetic bearing 56, and a lower protective bearing (lower touchdown bearing) 66 is disposed in the vicinity of the axial magnetic bearing 58. The rotary shaft 54 is formed with a recess 54 a extending in the circumferential direction at a position corresponding to the lower protective bearing 66. The lower protective bearing 66, the axial magnetic bearing 58, the sensor target 61, and the first axial displacement sensor 59 are arranged close to each other. When the magnetic bearings 56, 57, 58 are abnormal, the upper protective bearing 65 supports the rotary shaft 54 in the radial direction instead of the upper radial magnetic bearing 56, and the lower protective bearing 66 is the lower radial magnetic bearing 57 and the axial magnetic bearing. Instead of 58, the rotary shaft 54 is supported in the radial direction and the axial direction.

The rotating shaft 54 extends over the entire turbo vacuum pump, and one end of the rotating shaft 54 is located in the vicinity of the intake port 51A. Then, the exhaust portion 90, the upper protective bearing 65, the sensor target 62, the second axial displacement sensor 60, the upper radial magnetic bearing 56, the motor 55, the lower portion are sequentially arranged in the axial direction from the end on the intake side of the rotating shaft 54. A radial magnetic bearing 57, a lower protective bearing 66, an axial magnetic bearing 58, a sensor target 61, and a first axial displacement sensor 59 are disposed. A motion control unit 91 is constituted by the respective components from the upper protection bearing 65 to the first axial displacement sensor 59. The motion control unit 91 is cooled by a cooling jacket (cooling mechanism) 64 provided in the lower housing 63.

  In order to avoid contact between the rotating side and the fixed side, the axial gaps db and db ′ between the lower protective bearing 66 and the recess 54a are axial gaps dg1 to dg3 between the rotating blade 52 and the fixed blade 53, and axial magnetic bearings. It is set smaller than the axial gaps dm and dm ′ between 58a and 58b and the magnetic bearing target 58c (dg1 to dg3> db, db ′, dm, dm ′> db, db ′). Thus, in the turbo vacuum pump according to the present embodiment, the axial gaps db and db 'between the lower protection bearing 66 and the recess 54a are set to be the smallest.

  In the above configuration, the first axial displacement sensor 59 detects the amount of axial displacement of the rotary shaft 54, and based on the detected amount of displacement, from the axial magnetic bearing 58 via the feedback control device (magnetic bearing control unit). The axial direction position of the rotating shaft 54 is kept constant. Thereby, when the rotation shaft 54 is thermally expanded, the reference position of the axial extension of the rotation shaft 54 can be set as the position of the sensor target 61. Therefore, the axial gaps db and db ′ between the lower protective bearing 66 and the recess 54 a and the axial gaps dm and dm ′ between the axial magnetic bearings 58 a and 58 b and the magnetic bearing target 58 c are affected by the thermal expansion of the rotating shaft 54. It can be maintained almost constant without receiving.

  That is, when installing the first axial displacement sensor 59, it is important to consider the following points. (1) A lower protective bearing 66 that restricts the axial movement of the rotating shaft 54 and a first axial displacement sensor 59 that detects the axial position of the rotating shaft 54 are installed close to each other. (2) The first axial displacement sensor 59 and the axial magnetic bearing 58 are installed close to each other. In these points (1) and (2) (axial displacement sensor, sensor target, axial magnetic bearing, protective bearing for restricting axial movement are collectively arranged), the sixth reference shown in FIG. Examples are the same as in this embodiment. However, in consideration of the shaft vibration characteristics of the entire pump rotor composed of rotating shafts, rotor blades, etc. and the assembly of the pump, axial displacement sensors, sensor targets, axial magnetic bearings, and protective bearings that restrict axial movement are combined. It may be arranged on the shaft end side of the motion control unit.

  Further, with the above configuration, the exhaust section 90 composed of the rotary blade 52 and the fixed blade 53, the rotary shaft 54 composed of the motor 55, the magnetic bearings 56, 57, 58, the axial displacement sensors 59, 60, and the like. It is possible to structurally separate the motion control unit 91, and it is possible to prevent the heat of the exhaust unit 90 that becomes high temperature from being transmitted to the motion control unit 91 having a low heat resistance. In the present embodiment, the temperature of the portion of the rotary shaft 54 located in the exhaust portion 90, the rotary blades 52A to 52C, the fixed blades 53A to 53C, and the spacers 4a and 4b is 150 to 250 ° C., for example. On the other hand, the temperature of the part of the rotating shaft 54 located in the motion control unit 91 is, for example, 100 to 150 ° C., and the temperature of the lower housing 63 is 50 to 100 ° C.

  Note that the axial gaps dg1 to dg3 between the rotary blade 52 and the fixed blade 53 change due to a temperature change of the rotary shaft 54, a temperature change of the lower housing 63, and the like, as in the conventional example. For this reason, in the present embodiment, the gap between the sensor target 62 and the second axial displacement sensor 60 is measured by the second axial displacement sensor 60 disposed in the vicinity of the exhaust unit 90, and the measured value is converted to the turbo. It is used as information necessary for the control operation and protection operation of the vacuum pump. Thereby, the operation stability and high exhaust performance of the turbo vacuum pump are achieved. Hereinafter, the control operation and the protection operation of the turbo vacuum pump will be described with reference to FIGS. 13 and 14.

  FIG. 14 is a schematic diagram showing a magnetic bearing control device incorporated in the turbo type vacuum pump shown in FIG. As shown in FIG. 14, the first and second axial displacement sensors 59 and 60 are connected to sensor circuit devices 70a and 70b, respectively. The displacement amounts of the rotating shaft 54 detected by the first and second axial displacement sensors 59, 60 are converted into voltage signals by the sensor circuit devices 70a, 70b. The sensor circuit devices 70a and 70b are connected to the control unit 76 via A / D converters 75a and 75b, respectively. The voltage signals are converted from analog signals to digital signals by the A / D converters 75a and 75b, and then controlled. Input to the unit 76.

  The sensor circuit device 70a is connected to the phase compensator 71 via the adder / subtractor 73, and the voltage signal from the sensor circuit device 70a is corrected by the phase compensator 71 so that the rotating shaft 54 is stably floated. . The phase compensator 71 is connected to the axial magnetic bearing 58 via a current amplifier 72 so that a current for correcting the displacement amount of the rotating shaft 54 is supplied from the current amplifier 72 to the axial magnetic bearings 58a and 58b. It has become. Reference numeral 77 is an alarm indicator for indicating that the rotary shaft 54 is in an abnormal state of the turbo type vacuum pump, and this alarm indicator 77 is connected to the control unit 76. Reference numeral 80 is an electromagnetic valve that opens and closes the flow path of the coolant flowing into the cooling jacket 64, and this electromagnetic valve 80 is operated by a drive device 78. The drive device 78 is connected to the control unit 76, and the electromagnetic valve 80 is operated based on a signal from the control unit 76. Reference numeral 79 denotes an inverter that accelerates or decelerates the rotational speed of the rotating shaft 54 rotated by the motor 55. The inverter 79 accelerates or decelerates the rotational speed of the rotating shaft 54 via the motor 55 based on a signal from the control unit 76. It is like that.

  In the above configuration, the axial displacement amount of the rotating shaft 54 is detected by the first axial displacement sensor 59, converted into a voltage signal by the sensor circuit device 70 a, and then sent to the phase compensator 71. The amount of displacement as a voltage signal is corrected by the phase compensator 71 and then sent to the current amplifier 72. Then, a current sufficient to correct the amount of displacement flows from the current amplifier 72 to the axial magnetic bearings 58a and 58b, whereby the rotary shaft 54 is stably magnetically levitated in the axial direction. However, during operation of the turbo vacuum pump, the pump rotor constituted by the rotary shaft 54, the rotary blades 52, etc. thermally expands or contracts in the axial direction with the position of the sensor target 61 as a base point. For this reason, the axial gaps dg1 to dg3 between the rotary blade 52 and the fixed blade 53 change, and in the worst case, the rotary blade 52 and the fixed blade 53 come into contact with each other and the operation becomes impossible.

  In the present embodiment, in addition to the first axial displacement sensor 59, a second axial displacement sensor 60 is provided. The two displacement amounts detected by the first and second axial displacement sensors 59, 60 are input to the control unit 76 through the sensor circuit devices 70a, 70b and the A / D converters 75a, 75b. The amount of thermal expansion or temperature of the rotating shaft 54 is calculated by comparing the two displacement amounts. When the calculated thermal expansion amount (temperature) exceeds a predetermined thermal expansion amount (temperature), the control unit 76 causes the alarm display 77 to display that the rotating shaft 54 is in an abnormal state. Thus, it becomes possible to prevent the vehicle from becoming inoperable. When the thermal expansion of the rotating shaft 54 continues further, it is possible to output a stop signal from the control unit 76 to the inverter 79 to perform a protective operation such as stopping the operation.

  Furthermore, the cooling capacity of the cooling jacket 64 provided in the lower housing 63 can be adjusted by operating the electromagnetic valve 80 to control the amount of displacement detected by the second axial displacement sensor 60. That is, when the gap between the second axial displacement sensor 60 and the sensor target 62 becomes smaller than the initial displacement, the drive device 78 closes the electromagnetic valve 80 to reduce the cooling capacity of the cooling jacket 64, thereby reducing the The housing 63 can be extended in the axial direction. In the example of the magnetic bearing control device shown in FIG. 14, the temperature of the lower housing 63 is controlled by operating the electromagnetic valve 80, but the circulation flow rate and temperature of the refrigerant introduced into the cooling jacket 64 are adjusted. Obviously it may be. Further, the temperature of the entire turbo vacuum pump can be controlled by increasing the installation area of the cooling jacket 64.

  In general, when a turbo vacuum pump is continuously operated, the turbo vacuum pump becomes high temperature, and the temperature of the turbo vacuum pump is greatly different between when the pump is started and when the pump is operated. In order to adjust the temperature of the turbo vacuum pump by the cooling jacket 64 so that the gap between the second axial displacement sensor 60 and the sensor target 62 is constant under such conditions, the lower housing 63 is configured. It is necessary to make the linear expansion coefficient of the material to be larger than the material constituting the rotation shaft 54 (linear expansion coefficient of the lower housing 63 ≧ linear expansion coefficient of the rotation shaft 54). This is because the rotating shaft 54 rotates in a non-contact manner in a vacuum, and the heat radiation is poor and the temperature tends to be high. On the other hand, the temperature of the rotating shaft 54 can be adjusted directly by the cooling jacket 64, This is because the temperature becomes higher than the temperature of the lower housing 63. Therefore, if the linear expansion coefficient of the lower housing 63 is not larger than the linear expansion coefficient of the rotating shaft 54, the second axial displacement sensor 60 and the sensor target 62 are adjusted even if the temperature of the lower housing 63 is adjusted by the cooling jacket 64. The gap between and cannot be kept constant.

For this reason, the lower housing 63 is made of a material having a linear expansion coefficient that is larger than the linear expansion coefficient of the material constituting the rotating shaft 54. As a material constituting the lower housing 63, an aluminum alloy, stainless steel (linear expansion coefficient: 10 to 24 × 10 ⁻⁶ / ° C.) or the like is preferably used. As a material constituting the rotating shaft 54, stainless steel or Fe-Ni alloys, ceramics (linear expansion coefficient 2 to 10 × 10 ⁻⁶ / ° C.) and the like are preferably used.

  Further, the axial gaps dg <b> 1 to dg <b> 3 between the rotary blade 52 and the fixed blade 53 of the exhaust unit 90 are set so as to increase as the axial distance from the second axial displacement sensor 60 increases. Thereby, the contact between the rotary blade 52 and the fixed blade 53 can be prevented, and the gaps dg1 to dg3 can be made as small as possible. That is, it is preferable that the axial gaps dg1 to dg3 satisfy dg1 ≦ dg2 ≦ dg3.

  Furthermore, the rotating shaft 54 can be moved via the D / A converter 74 and the adder / subtractor 73 based on the thermal expansion amount (temperature) of the rotating shaft 54. That is, the voltage signal input to the phase compensator 71 is adjusted by the adder / subtractor 73 according to the thermal expansion amount (temperature), and the current flowing through the axial magnetic bearing 58 is changed. Thereby, the rotating shaft 54 can be moved. In this case, it is necessary to move the rotating shaft 54 within a range where the rotating blade 52 and the fixed blade 53 or the lower protection bearing 66 and the rotating shaft 54 do not contact each other. With the configuration as described above, the turbo vacuum pump can be stably operated continuously over a wider temperature range.

In this embodiment, sensor targets 61 and 62 are provided on the surfaces facing the first and second axial displacement sensors 59 and 60, respectively, and these sensor targets 61 and 62 are fixed to the rotating shaft 54. . The sensor targets 61 and 62 are provided to improve the detection sensitivity of the first and second axial displacement sensors 59 and 60, and magnetic materials such as silicon steel and permalloy are preferably used. However, the magnetic material generally has a low mechanical strength, and when the turbo vacuum pump operates at high speed, the strength may be insufficient. In such a case, a high-strength ferromagnetic material such as martensitic stainless steel may be used for the rotating shaft 54, and the position of the rotating shaft 54 may be directly sensed without providing a sensor target.
Naturally, the present invention is not limited to the above-described embodiments, and the above-described configuration examples may be combined.

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2a, 2b, 2c Rotating blade 3a, 3b, 3c Fixed blade 4a, 4b Spacer 5a, 5b Axial magnetic bearing 6 Axial displacement sensor 7 Sensor target 8A Motor rotor 8B Motor stator 9a, 9b Protective bearing (touch down bearing)
DESCRIPTION OF SYMBOLS 10 Heater 11 Pump stator 12 Cooling jacket 13a, 13b Thermistor 14 Inlet 15 Exhaust 16 Magnetic bearing target 17 Magnetic bearing control apparatus 20a, 20b Sensor circuit apparatus 21a, 21b A / D converter 22 Rotational speed sensor 23 Rotational speed converter 24 Averaging device 30 Synchronous detection device 31 Differential amplifier 51 Upper housing 51A Inlet port 51B Exhaust port 52A, 52B, 52C Rotary blades 53A, 53B, 53C Fixed blade 54 Rotary shaft 55 Motor 56 Upper radial magnetic bearing 57 Lower radial magnetic bearing 58 Axial magnetic bearing 59 First axial displacement sensor 60 Second axial displacement sensor 61, 62 Sensor target 63 Lower housing 64 Cooling jacket (cooling mechanism)
65 Upper protective bearing 66 Lower protective bearing 70a, 70b Sensor circuit device 71 Phase compensator 72 Current amplifier 73 Adder / subtractor 74 D / A converter 75a, 75b A / D converter 76 Controller 77 Alarm indicator 78 Drive device 79 Inverter 80 Electromagnetic Valve 90 Exhaust part 91 Motion control part

Claims (5)

And at least a pair of axial magnetic bearings for magnetically levitating the rotating shaft, a rotating blade attached to the rotating shaft, a fixed blade disposed to face the rotating blade, and a motor for rotationally driving the rotating shaft. In the turbo-type vacuum pump provided,
While constituting the exhaust part by arranging the rotary blade and the fixed blade near one end of the rotating shaft,
A first axial displacement sensor for detecting the axial position of the rotary shaft, and the axial magnetic bearing, and a protection bearing for regulating the axial movement of the rotary shaft near the other end of the rotary shaft Configure the motion control unit by arranging,
A turbo type vacuum pump characterized in that a second axial displacement sensor for detecting an axial position of the rotary shaft is disposed in the vicinity of the exhaust section. In the turbo vacuum pump according to claim 1, wherein the motion control unit controls the temperature of the housing by the cooling mechanism based on the output value of the housed, prior Symbol second axial displacement sensors in a housing The turbo type vacuum pump characterized in that the output value of the second axial displacement sensor is controlled by the above .   2. The turbo vacuum pump according to claim 1, wherein an alarm operation is performed based on output values of output values of the first axial displacement sensor and the second axial displacement sensor. In the turbo vacuum pump according to claim 2, the material constituting the front Symbol housing, turbo, characterized in that it has a larger linear expansion coefficient than the linear expansion coefficient of the material constituting the rotary shaft Vacuum pump.   2. The turbo type vacuum pump according to claim 1, wherein a plurality of the rotary blades and the fixed blades are provided, and a gap formed between the plurality of rotary blades and the plurality of fixed blades is the second axial. A turbo type vacuum pump characterized in that it is set so as to increase as it moves away from a displacement sensor.

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