JPH084766A - Air bearing device - Google Patents

Abstract

PURPOSE:To prevent local thermal deformation by arranging plural temperature sensors and cooling elements in a dotted shape in an air bearing, and controlling the respective cooling elements according to temperatures in respective places in the air bearing so that the temperatures in the respective places fall within a preset temperature range. CONSTITUTION:Plural temperature sensors 36 to 39 and plural electronic cooling elements 31 to 34 are incorporated into an air bearing 10 having a cylindrical rotor 11 fixed to a rotary shaft and a stator 20 to rotatably support the rotor 11 by securing a space to pass gas supplied through an air passage 28 or the like between it and an outer peripheral surface of the rotor 11. The temperature distribution of the air bearing 10 is grasped by a computer according to output signals of the respective temperature sensors 36 to 39, and a heat absorbing quantity (= an electric current quantity supplied to the electronic cooling elements) of respective electronic cooling elements 31 to 34 is found, and the respective electronic cooling elements 31 to 34 are driven so as to absorb heat equivalent to this heat absorbing quantity. Thereby, local thermal deformation is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air bearing device incorporated in an ultra-precision processing machine, an ultra-precision measuring machine or the like.

[0002]

2. Description of the Related Art In recent years, air bearings are often used as bearings incorporated in ultra-precision processing machines and ultra-precision measuring machines. In general, other bearings such as ball bearings have solid contact on the bearing surface,
It is difficult to obtain a rotational accuracy higher than the mechanical accuracy of the bearing surface. However, in the air bearing, since the rotor floats above the stator due to the high-pressure air film, the rotational accuracy of several tens of nm or more can be obtained without depending on the mechanical accuracy of the bearing surface. Therefore, air bearings are increasingly used in devices that require highly accurate rotational movement accuracy.

This air bearing is also characterized in that frictional heat is less likely to occur and there is a thermal advantage because there is no solid contact between the bearing surfaces. However, the gap between the bearing surface of the rotor of the air bearing and the bearing surface of the stator is as narrow as several tens of μm, and if high-pressure air of ten dozen MPa is subjected to relative motion of the bearing surface due to rotation of the rotor, shearing of the air will occur. The force causes frictional heat to generate heat. Therefore, the faster the rotor speed, the more
It has been revealed that a large amount of heat is generated and the air bearing is thermally deformed.

Conventionally, in ultra-precision processing machines and ultra-precision measuring machines, measures have been taken to reduce the thermal deformation of the processing machine by keeping the ambient temperature constant or by flowing cooling water to the heat generated from the motor. are doing. However, recently, the machining accuracy required for machining has also increased, and the heat generated in the air bearing cannot be ignored. Thermal deformation of the air bearing hinders the improvement of machining accuracy. It is one of the points.

Therefore, as a technique for reducing the thermal deformation of the air bearing, for example, a method of lowering the temperature of the high-pressure air supplied to the air bearing by about 10 ° C. according to the number of rotations of the rotor, rotor rotation information and processing conditions. There has been proposed a method (described in Japanese Patent Laid-Open No. 60-192118) in which the total amount of heat generated is predicted in advance and the heat corresponding to the predicted amount of heat generated is absorbed by an electronic cooling element attached to the bearing.

[0006]

However, in the former technique of lowering the temperature of the high pressure air, the heat transfer coefficient from the air bearing to the high pressure air is not so large because the heat transfer coefficient between the solid surface and the high pressure air is small. However, although it is effective at low speed rotation with a small amount of heat generation, there is a problem that the air bearing cannot be sufficiently cooled at the time of high speed rotation with a large amount of heat generation, which may cause thermal deformation.

The latter technique using the electronic cooling element is effective as a cooling method for the air bearing, and is effective when the heat generation amount is large, but the heat generation amount is comprehensively judged and the cooling is performed. Therefore, there is a problem that local thermal deformation due to local temperature rise cannot be dealt with. Specifically, for example, the relative speed between the stator and the rotor is considerably different depending on the fact that the gap of ten and several μm between the rotor and the stator is not always constant, and the radial position on the bearing surface in the thrust direction. As a result, the temperature may rise locally. Although not due to the air bearing itself, in the case where the rotor and the motor for rotating the rotor are integrated, heat generated by the motor may affect the air bearing. The present invention has been made by paying attention to these problems of the related art, and the air bearing can be effectively used even in the case where a large amount of heat is generated such as when rotating at a high speed and the temperature distribution is biased. It is an object of the present invention to provide an air bearing device that can be cooled to a minimum temperature to minimize thermal deformation and improve the rotational accuracy of the shaft.

[0008]

In order to achieve the above object, an air bearing device is provided with a plurality of temperature sensors scattered on the air bearing and a plurality of cooling elements. Based on the temperature at each location inside the air bearing detected by the plurality of temperature sensors, the plurality of cooling elements are controlled so that the temperature at each location falls within a predetermined temperature range for each location. A cooling control means is provided.

Here, in the air bearing device, the stator faces a part of an outer peripheral surface of the rotor (hereinafter referred to as a bearing surface), and the gas is interposed between the stator and the bearing surface of the rotor. It is preferable that a bearing surface passing therethrough is formed, and the plurality of temperature sensors and the plurality of cooling elements are provided in the stator along the bearing surface. In the air bearing device, the stator has a bearing surface that faces the bearing surface of the rotor and allows the gas to pass between the stator bearing surface and the rotor bearing surface. A gas passage through which the gas to be supplied is formed is formed between the stator and a bearing surface, and some of the plurality of temperature sensors and the plurality of cooling elements are provided along the gas passage in the stator. And the remaining part may be provided along the bearing surface in the stator.

The cooling element may be a Peltier element having a heat absorbing surface and a heat radiating surface. In this case, it is preferable that the heat absorption surface side of the Peltier element faces the bearing surface side, and a cooling fluid passage through which a cooling fluid flows is formed on the heat radiation surface side of the Peltier element.

[0011]

In the present invention, the electronic cooling elements attached to the air bearings are individually controlled based on the temperature information of the individual temperature sensors, so that cooling is performed according to the temperature distribution inside the air bearings. The internal temperature difference can be minimized. Therefore, local thermal deformation can be suppressed inside the air bearing.
Further, by providing a temperature sensor in the immediate vicinity of the bearing surface of the air bearing, the rotational state of the rotor can be known from the temperature change, and therefore the amount of heat generated can be calculated and cooled accordingly.

Further, since the temperature of the gas just before flowing into the bearing surface of the air bearing can be adjusted by the cooling element, the bearing surface can be effectively cooled.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the bearing device according to the present invention will be described below with reference to the drawings. As shown in FIG. 4, the air bearing device of this embodiment includes a plurality of temperature sensors 3
6, 37, 38, 39 and a plurality of electronic cooling elements 31, 3
Air bearing 10 incorporating 2, 33, 34
And the temperature distribution of the air bearing 10 is grasped based on the signals from the plurality of temperature sensors 36, 37, 38, 39, and the heat absorption amount of each of the plurality of electronic cooling elements 31, 32, 33, 34 (= The computer 60 for determining the amount of supplied current) and the electronic cooling elements 31, 32, 33, 34 so as to absorb heat corresponding to the amount of heat absorbed by the electronic cooling elements 31, 32, 33, 34 determined by the computer 60. A cooling element drive circuit 61 for driving the air bearing system, an air supply system 62 for supplying compressed air into the air bearing 10, and a cooling water supply system 65 for supplying cooling water into the air bearing 10.

As shown in FIG. 1, the air bearing 10 has a rotor 11 fixed to the rotating shafts 42 and 55 and rotating together with the rotating shafts 42 and 55, and a space through which gas passes between the outer peripheral surface of the rotor 11. It is configured to have a stator 20 that rotatably supports the rotor 11 so as to be rotatable, and a base 15 that supports the stator 20. As shown in FIG. 3, the air bearing 10 of the present embodiment is of a motor integrated type. The motor 40 includes a rotor 41 connected to the rotor 11 of the air bearing 10, a stator 45 formed in an annular shape around the rotor 41, a hollow cylindrical motor housing 48 that covers these, and a rotation of the rotor 41. It has an encoder 50 for detecting the amount and an under cover 49 that covers the encoder 50.

Here, in order to facilitate understanding of the following description, the center axis of the bearing rotor 11 and the center axis of the motor rotor 41 (located on the center axis of the bearing rotor 11) extend in the vertical direction. In addition, the air bearing 10 is provided on the motor 40.
Therefore, here, the lower end of the bearing rotor 11 and the upper end of the motor rotor 41 are connected to each other, and
An encoder 50 is attached to the lower end portion of 1. The motor rotor 41 has a rotating shaft 42 and a permanent magnet 43 provided on the outer circumference of the rotating shaft 42. A flange 44 is formed on the upper end of the rotary shaft 42.
The motor stator 45 has an iron core 47 that is annularly arranged around the rotor 41, and a coil 46 that is annularly formed around the rotor 41. The motor stator 45 is fixed to the inner peripheral surface of a motor housing 48 having a cylindrical shape in the air. An under cover 49 that covers the encoder 50 attached to the lower end of the motor rotor 41 is fixed to the lower end of the housing 48. This housing 48
Is fixed to the bearing base 15 at its upper end. The bearing base 15 covers the entire motor 40.

The rotor 11 of the air bearing 10 is shown in FIG.
As shown in FIG. 1, a cylindrical body portion 12, a disc-shaped input shaft mounting flange portion 13 formed at the lower end thereof, and a disc-shaped output shaft mounting flange portion 14 formed at the upper end thereof are provided. are doing. As shown in FIG. 3, the flange 56 of the output rotary shaft 55 has bolts 57 on the output shaft mounting flange portion 14.
The flange 44 of the motor rotor 41 is connected to the input shaft mounting flange portion 44 by a bolt 51. The upper surface of the input shaft mounting flange portion 13 and the lower surface of the output shaft mounting flange portion 14 are horizontally flat and form thrust bearing surfaces 13a and 14a. In addition, the outer peripheral surface of the cylindrical body 12 is the radial bearing surface 1
2a is formed.

The stator 20 of the air bearing 10 is formed in a cylindrical shape around the cylindrical body 12 between the input shaft mounting flange portion 13 and the output shaft mounting flange portion 14 of the bearing rotor 11. This stator 20
A cylindrical bearing surface forming member 21 having bearing surfaces 22a, 23a, 24a facing the bearing surfaces 12a, 13a, 14a of the rotor 11, and a stator provided on the outer peripheral side of the bearing surface forming member 21. It has a main body block 26. The inner peripheral surface of the bearing surface forming member 21 is the rotor 11
Of the cylindrical cylindrical body 2 facing the radial bearing surface 12a of the
2, a disc-shaped upper disc portion 24 whose upper surface faces the upper thrust bearing surface 14a of the rotor 11 and is formed on the upper end of the cylindrical body portion 22, and a lower surface of the lower thrust bearing surface 1 of the rotor 11.
It has a disk-shaped lower disk part 23 which is formed at the lower end of the cylindrical body part 22 and faces 3a. The inner peripheral surface of the cylindrical body portion 22 of the bearing surface forming member 21 forms a radial bearing surface 22a, and the upper surface of the upper disk portion 24 and the lower surface of the lower disk portion 23 form thrust bearing surfaces 24a, 23a. . As shown in FIG. 2, the stator body block 26 is composed of six fan-shaped blocks 26a, 26b, ... An air passage 28 through which compressed air from the air supply system 62 passes in each of the blocks 26a, 26b, ....
And the cooling water passage 2 through which the cooling water from the cooling water supply system 65 passes
7 are formed. The bearing surface forming member 21 has an air passage 25 for guiding the compressed air, which has passed through the air passage 28 of the stator body block 26, between the rotor bearing surfaces 12a, 13a, 14a and the stator bearing surfaces 22a, 23a, 24a. Are formed.

A plurality of electronic cooling elements 32, 33, 34 are provided on the outer peripheral surface of the stator body block 26 in contact with the bearing surface forming member 21 so as to be scattered. , 34 are provided on the outer peripheral surface except the heat insulating material 29. Also,
Inside the stator body block 26, a plurality of electronic cooling elements 31, 31, ... Are provided so as to be scattered along the air passage 28. A plurality of these electronic cooling elements 31,
Of the parts 32, 33, 34, the one provided in the portion of the bearing surface forming member 21 that comes into contact with the cylindrical body 12 is the radial bearing electronic cooling element 32, which is the disk portion 23, 24 of the bearing surface forming member 21. The electronic cooling element 33 for the inner side of the thrust bearing is provided in a portion that comes into contact with the inner peripheral portion of the
a, 34a, the disk portions 23, 24 of the bearing surface forming member 21.
The ones provided in the portion in contact with the portion near the outer periphery of the thrust bearing outer electronic cooling elements 33b, 34b,
What is provided along the air passage 28 is an air-cooling electronic cooling element 31. 2, which is a sectional view taken along line II-II in FIG. 1, the electronic cooling elements 31, 32,
34 is hatched, but this is done to clarify the existence of the electronic cooling elements 31, 32, 34, and does not show the cross section of the electronic cooling elements 31, 32, 34. .

The electronic cooling elements 31, 32, 3 of this embodiment
Reference numerals 3 and 34 are so-called Peltier elements, and the amount of heat absorbed and the amount of heat generated can be controlled by adjusting the amount of current passed through them. The heat absorption surface of each Peltier element is the bearing surface 22.
It is provided so as to face the a, 23a, 24a or the air passage 28 side, and the heat generating surface thereof faces the cooling water passage 27 side.

A plurality of temperature sensors 36, 36, ... Are provided in the air passage 28 inside the stator body block 26. Further, the bearing surface forming member 21 also includes the bearing surfaces 22
A plurality of temperature sensors 37, 38, 39 are provided so as to be scattered along a, 23a, 24a. In the present embodiment, these temperature sensors 36, 37, 38, 39 are provided for each electronic cooling element 31, 32, 33, 34. That is, in this embodiment, the temperature sensor 36,
37, 38, 39 are the electronic cooling elements 31, 32, 3
One is provided in the vicinity of 3, 34, and the electronic cooling elements 31, 3
The same number as the electronic cooling elements 31, 32, 33, 34 is provided so that a one-to-one correspondence with 2, 33, 34 is established.

As shown in FIG. 4, the air supply system 62 includes a compressed air supply source (not shown) for supplying compressed air, and the compressed air from the compressed air supply source to the air passage 28 of the bearing stator 20. And an air flow rate control valve 64 provided in the air pipe 63 for controlling the flow rate of the compressed air. The cooling water supply system 65 also supplies a cooling water supply source (not shown) that supplies the cooling water and a cooling water pipe 66 that guides the cooling water from the cooling water supply source to the cooling water passage 27 of the bearing stator 20. When,
The cooling water pipe 66 has a cooling water flow rate adjusting valve 67 for adjusting the flow rate of the cooling water.

The computer 60 has a CPU (not shown) for executing various calculations, a memory (not shown) for storing various programs and data, a cooling element drive circuit 61, and temperature sensors 36, 37. , 38, 39
And an interface (not shown) connected to each of the control valves 64 and 67 for transmitting and receiving a signal to and from each of the control valves 64 and 67, respectively. The operation of the bearing device will be described. First, before driving the motor 40, the air supply system 6
2, compressed air is supplied into the air bearing 10, and the bearing surfaces 12a, 13a, 14a of the bearing rotor 11 and the bearing surfaces 22a, 23a, 24a of the bearing stator 20.
An air film is formed between and. Further, the cooling water supply system 65
Supply cooling water into the air bearing 10.

As described above, the motor 40 is driven while the compressed air and the cooling water are being supplied into the air bearing 10. The motor 40 is driven to drive the bearing rotor 11
When the output rotary shaft 55 rotates, the rotor bearing surface 12
a, 13a, 14a and stator bearing surfaces 22a, 23a,
The bearing surfaces generate heat due to the relative movement of the air between the bearing surfaces and 24a and the bearing surfaces. Also, as a matter of course, the heat from the motor 40 is also transmitted to the air bearing 10.

The plurality of temperature sensors 36, 37, 38, 39 provided in the bearing stator 20 detect the respective temperatures and output the values to the computer 60.
The computer 60 includes a plurality of temperature sensors 36, 37, 3
The temperature distribution of the air bearing 10 is grasped on the basis of the temperatures detected by the sensors 8 and 39 in the air bearing 10. The allowable temperature range is stored in advance in the memory of the computer 60 for each location in the air bearing 10. The computer 60 uses the allowable temperature range and the temperatures detected by the temperature sensors 36, 37, 38, 39. And the cooling element supply current amount that can keep each part within the allowable temperature range is compared with each electronic cooling element 31, 32, 33, 3
It is determined for each 4 and is output to the cooling element drive circuit 61.
The cooling element drive circuit 61 includes the electronic cooling elements 31, 32,
The computer 60 supplies the amount of electric current determined by the computer 60.

Each electronic cooling element 31, 32, 33, 34
Absorbs the heat according to the amount of current supplied from the cooling element drive circuit 61, and releases this amount of heat. Each of the electronic cooling elements 32, 33, 34 has a heat absorption surface that is a bearing surface 22.
The bearing surfaces 22a, 23a, 24a or the air passage 2 are provided so as to face the a, 23a, 24a side or the air passage 28 side, and the heat generating surface thereof faces the cooling water passage 27 side.
While cooling the compressed air in 8, the heat from the heat generating surface is absorbed by the cooling water passing through the cooling water passage 27.

As a result, the bearing surfaces 22a, 23a, 24a of the bearing stator 20 can be kept within the allowable temperature range. In addition, the bearing surface 1 of the bearing rotor 11
2a, 13a, 14a, the bearing surface 12a,
Since the stator bearing surfaces 22a, 23a, 24a facing 13a, 14a via the compressed air are contained within the allowable temperature range, as a result, they can also be contained within the allowable temperature range. This rotor bearing surface 12a, 13
Needless to say, the cooling elements 32, 33, 34 for the bearings provided on the stator 20 indirectly contribute to the cooling of the cooling elements a, 14a, but the electronic cooling element 31 for air cooling has a great significance. Hold. That is, the compressed air is cooled by the air cooling electronic cooling element 31,
It is supplied between the rotor bearing surfaces 12a, 13a, 14a and the stator bearing surfaces 22a, 23a, 24a. Therefore, this compressed air causes the stator bearing surfaces 22a, 23
a, 24a as well as rotor bearing surfaces 12a, 13a,
This is because 14a is also cooled.

Here, the temperature distribution of the air bearing 10 will be specifically described. Thrust bearing surface 23a, 2
4a, the outer peripheral portion farther from the rotor central axis is closer to the air and the bearing surface 23 than the inner peripheral portion closer to the rotor central axis.
The relative speed with respect to a and 24a becomes large. For this reason, in the thrust bearing surfaces 23a and 24a, the amount of heat generation is larger in the outer peripheral side portion far from the rotor central axis than in the inner peripheral side portion closer to the rotor central axis. Therefore, in the present embodiment, a larger amount of current is supplied to the thrust bearing outer side electronic elements 33b and 34b than to the thrust bearing inner side electronic cooling elements 33a and 34a, and the outer peripheral side portions of the thrust bearing surfaces 23a and 24a are supplied. Cooling effectively.

Further, in this embodiment, the air bearing 10
Since the motor 40 is provided below, the amount of heat in the lower portion of the air bearing 10 is larger than that in the upper portion of the air bearing 10 due to the heat from the motor 40. For this reason, in this embodiment, more current is supplied to the cooling element provided in the lower part of the air bearing 10 than in the cooling element provided in the upper part of the air bearing 10 to effectively cool the lower part of the air bearing 10. There is.

As described above, in this embodiment, even if the heat generation amount of a specific portion in the air bearing 10 is large, this specific portion can be grasped and cooled effectively, so that the local portion can be effectively cooled. Thermal deformation can be suppressed. Further, not only the air between the rotor bearing surface and the stator bearing surface is cooled, but also the rotor 11 is directly cooled by the electronic cooling elements 32, 33, 34, so that the total amount of heat generated at high speed rotation is reduced. Even if the number is large, the air bearing 10 can be cooled efficiently. Therefore, in this embodiment, thermal deformation can be minimized and the rotation accuracy of the shaft can be improved.

In this embodiment, the temperature sensors 36, 37, 38, 39 are provided only on the stator 20, but the rotor 11 is also provided with a temperature sensor, and the stator 20 is based on the temperature detected by the temperature sensor. The temperature of the compressed air may be adjusted by the electronic cooling element 31 for air cooling provided in the. Further, not only the temperature sensor but also the electronic cooling element may be provided in the rotor 11. However, in the case where the motor is provided with the electronic cooling element and the temperature sensor, these rotate together with the rotor 11. Therefore, it is necessary to provide the rotor 11 with a slip ring so that signals or currents can be exchanged with the outside.

[0031]

According to the present invention, even if a large amount of heat is generated at a specific location in the air bearing, this specific location can be grasped and cooled effectively, so that local thermal deformation can be prevented. Can be suppressed. In addition, since the air bearing is directly cooled by the cooling element, it is possible to obtain a far greater cooling effect than cooling a gas having a small heat capacity and cooling the air bearing only with this cooled gas. . Therefore, in the present invention, thermal deformation is minimized,
The rotation accuracy of the shaft can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an air bearing according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a vertical sectional view of an air bearing motor according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an overall configuration of an air bearing device according to an embodiment of the present invention.

[Explanation of symbols]

10 ... Air bearing, 11 ... Rotor, 12a ... (Rotor) radial bearing surface, 13a ... (Rotor) lower thrust bearing surface, 14a ... (Rotor) upper thrust bearing surface, 15 ... Base, 20 ... Stator, 21 ... Bearing surface forming member, 22a ... (for stator) radial bearing surface, 23a
... (stator) lower thrust bearing surface, 24a ... (stator) upper thrust bearing surface, 25, 28 ... air passages,
27 ... Cooling water passage, 29 ... Heat insulating material, 31 ... Air cooling electronic cooling element, 32 ... Radial bearing electronic cooling element, 33
a, 34a ... Electronic cooling element for thrust bearing inner side, 33
b, 34b ... Thrust bearing outside electronic cooling element, 40 ... Motor, 60 ... Computer, 61 ... Cooling element drive circuit,
62 ... Air supply system, 65 ... Cooling water supply system.

Claims (4)

[Claims] 1. A cylindrical rotor fixed to a rotating shaft and rotating together with the rotating shaft, and a stator rotatably supporting the roller with a gap between the outer peripheral surface of the rotor and a passage of gas. In an air bearing device including an air bearing configured as described above, a plurality of temperature sensors are provided in the air bearing so as to be scattered, and a plurality of cooling elements are provided in a scattered manner. Based on the temperature at each location in the air bearing detected by the temperature sensor, cooling control means for controlling the plurality of cooling elements is provided so that the temperature at each location falls within a predetermined temperature range for each location. An air bearing device characterized by being provided. 2. A bearing surface is formed on the stator so as to face a part of an outer peripheral surface of the rotor (hereinafter referred to as a bearing surface) and to pass the gas through the bearing surface of the rotor. The air bearing device according to claim 1, wherein the plurality of temperature sensors and the plurality of cooling elements are provided in the stator along the bearing surface. 3. A bearing surface is formed on the stator so as to face a part of an outer peripheral surface of the rotor (hereinafter referred to as a bearing surface) and to allow the gas to pass therethrough. In addition, a gas passage through which the gas supplied is formed between the bearing surface of the rotor and the bearing surface of the stator, and among the plurality of temperature sensors and the plurality of cooling elements,
2. The air bearing device according to claim 1, wherein a part of the air bearing device is provided along the gas passage in the stator, and a remaining part of the air bearing device is provided along the bearing surface in the stator. 4. The cooling element is a Peltier element having a heat absorbing surface and a heat radiating surface, the heat absorbing surface side of the Peltier element faces the bearing surface side, and cooling fluid flows to the heat radiating surface side of the Peltier element. The air bearing device according to claim 2 or 3, wherein a fluid passage is formed.