JPH033629A - Rotating device - Google Patents

Abstract

PURPOSE:To easily fabricate a product with reduced eddy current and preventing the locking by thermal expansion with a bearing clearance enlarged by rotatably supporting a bearing interposed between a rotor and a stator by supersonic gaseous bearing. CONSTITUTION:A stator 7 having a stator coil 7a is fixed to the inside circumference of a motor casing 1. Plural air supply channels 11 are diametrically provided in the center of the stator 7, with which high pressure air is supplied from an air supply plug 14. A rotor 6 fixed to a shaft 3 forms a recessed gas passage 9 in the center, and with both ends 8 narrowed, supersonic gaseous bearing 15 is formed. The shaft 3 of the rotor 6 is inserted into a hole 1a on both sides of the casing 1. On the other hand, a ball bearing 5 is provided to prevent thrust. After a motor was started, both ends of the rotor 6 are rotatably supported non-contactingly with supersonic air flow. A high speed device can thereby be assembled easily in which eddy current is reduced with the clearance of bearing enlarged and the occurrence of the locking by thermal expansion is prevented.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a rotating device such as a motor.

Conventional technology In order to make the motor for high-speed rotation drive more compact,
The present applicant has previously proposed a system in which a static pressure gas bearing is formed between the rotor and the stator. To explain with reference to FIG. 5, the rotating shaft 52 passes through the axial center position of the motor case 51,
A rotor 53 made of a magnet is fitted and fixed on the outer periphery of the rotating shaft 52, and a stator 54 is fitted and fixed on the inner periphery of the motor case 51 so as to face the outer periphery of the rotor 53 with a small gap therebetween. The inner circumferential surface of the stator 54 and the outer circumferential surface of the rotor 53 are formed smoothly, and a pair of circumferential grooves 55 are formed at appropriate positions from both ends, and a throttle passage 56 is formed in the circumferential grooves 55. A gas supply passage 57 is formed to supply high-pressure gas through the rotor 53, and a static pressure gas bearing 58 is formed in a minute gap between the outer peripheral surface of the rotor 53 and the inner peripheral surface of the stator 54.
is formed.

In the above configuration, the rotor 53 and the rotating shaft 52 are supported by the static pressure gas bearing 58 on the outer periphery of the rotor 53 to ensure high precision rotation, and the static pressure gas bearing 58 is located on the outer periphery of the rotor 53. Since the bearing radius is large, it has sufficient rigidity and load capacity even if a bearing gap of about 10 to 20 μm is formed, which is suitable for mass production, and the wide area between the pair of circumferential grooves 55 and 55 can be maintained at high pressure. This ensures a large load capacity.

On the other hand, a controlled magnetic bearing is known as a type of high-speed, high-precision bearing that uses electromagnets to actively control the shaft center position. This controlled magnetic bearing is non-contact and does not require the use of lubricant, so it is suitable for high-speed rotation with low torque and low noise. It can also be used in high vacuum, is free from contamination with lubricant, and has high speed control. It has features such as being able to obtain a rigid bearing, and it has been proposed to be applied to spindle bearings in processing machines such as milling machines, making use of its characteristics of being suitable for high-speed rotation and having high rigidity. There is.

The schematic configuration of the spindle drive device in this milling machine will be explained. In FIG. 6, 61 is a spindle, and an end mill 62 is fitted into one end of the spindle. The spindle 61 is rotatably supported near both ends by magnetic bearings 63a and 63b, and is configured to be driven by a motor 64 disposed in the middle. Further, a magnetic bearing 63a located at one end of the spindle 61 and a motor 6
A thrust bearing 65 is disposed between the two. 6
6a and 66b are sensors arranged at both ends of the spindle 61 to detect the radial position; 67 is the spindle 61;
This is a sensor provided at the other end to detect the position in the axial direction. 68a, 68b are magnetic bearings 63a, 63b, 65
This is a rolling bearing that supports the spindle 61 in abnormal situations where the spindle 61 does not operate effectively or when the bearing action is unstable such as when starting or stopping.

In the above configuration, the spindle 61 is raised by detecting the radial and axial positions of the spindle 61 using the sensors 66a, 66b, and 67, and controlling the magnetic bearings 63a, 63b, and 65 according to the amount of eccentricity. It can be held in a predetermined position with precision, and by rotating the spindle 61 with the motor 64, highly accurate machining can be performed with the end mill 62.

Problem to be Solved by the Invention However, in the motor configured as shown in FIG. 5, the rotor 53 rotating at high speed generates heat due to eddy current loss.
There is a problem in that the amount of deformation of the rotor 53 due to the thermal expansion is extremely large compared to the bearing clearance, and exceeds the allowable amount of deformation. For example, the rotor 53 with a diameter of 30m5+ is
When the temperature increases by 0°C, the amount of expansion becomes approximately IO μm.

In addition, eddy current loss increases in proportion to the square of the rotation speed,
As the speed increases, the heat generated by the rotor 53 increases, so cooling the rotor 53 becomes an essential condition. However, if the bearing gap of the hydrostatic bearing is about 10 μm, it is difficult to flow a large amount of cooling gas between the rotor 53 and the stator due to the viscous resistance of the gas, and therefore it is difficult to suppress the heat generation of the rotor 53. It is.

Furthermore, when applied to high-speed processing machines, etc., the environment around the bearing is not necessarily kept clean, and there is a risk that the bearing may become locked if dirt, mackerel, etc. enter the bearing gap.

In addition, in the spindle driving device using magnetic bearings shown in FIG. 6, the above problem is solved because the bearing gap can be made large, but the two radial bearings 63a, 63b and the thrust bearing 65 are each equipped with a sensor 66a. , 66b, 67
Since the bearings 66a, 66b, 67 are required, there is a problem of high cost.
This requires a large amount of installation space, which increases the cost and size of the device.

In addition, the supersonic gas bearing devised by Mie et al., which uses supersonic gas flow as a gas bearing for high-speed rotation, is useful for example in ``lubrication''.
Volume 33, No. 5, P345-349 (1988)
It is disclosed in et al.

However, in order to make the motor more compact, it is not envisaged that it will be applied to solve the above problems.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a rotating device that is capable of high speed rotation and has a compact configuration.

Means for Solving the Problems In order to achieve the above object, the present invention is characterized in that the rotor is rotatably supported by a supersonic gas bearing interposed between the stator and the rotor.

Function According to the present invention, since a gas with low viscosity is used as the bearing fluid, friction is low and it is possible to cope with high speed rotation, and since a supersonic gas bearing that utilizes inertia force is used, the pressure at the bearing outlet end can be reduced. It can be increased regardless of the ambient pressure, so sufficient rigidity and load capacity can be obtained even if the bearing gap is widened. As a result, by creating a sufficient bearing gap in the stator and rotor, there is no risk of locking even if there is thermal expansion, and since the bearing gap is large, sufficient cooling can be achieved by flowing a large amount of gas, allowing cooling. Due to the large effect, even if heat generation due to eddy current loss is large, thermal expansion can be reduced, and high speeds can be achieved.

Therefore, it is possible to provide a supersonic gas bearing between the stator and rotor of a high-speed rotating motor, which eliminates the need for bearings on both sides of the motor, making the entire rotating device more compact and reducing the natural frequency. There is no risk of locking when passing critical speeds, and since the bearing clearance is large, the machining accuracy of the stator and rotor does not need to be high, and gas supply management is similar to that of ordinary hydrostatic bearings. Although it is not as sophisticated as the previous model, it is possible to achieve effects such as cost reduction.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

In FIG. 1, reference numeral 1 denotes a motor case, which has a space 2 in which a stator and a rotor are placed, and a rotating shaft 3 passing through the axial center of the space 2. One end wall 1a of motor case l
A thrust bearing 5 externally fitted and fixed to the rotating shaft 3 is fitted into a bearing hole 4 formed in the bearing hole 4 . In the space 2, a rotor 6 equipped with a samarium cobalt magnet is fixed to the outer periphery of the rotating shaft 3, and a stator 7 is mounted with a stator coil 7a facing the outer periphery of the rotor 6 with a small bearing gap. is arranged and is fitted and fixed to the inner circumference of the motor case 1.

The outer circumferential surface of the rotor 6 is formed into a non-cylindrical surface 8 machined so that the diameter is small at the center and gradually increases toward both ends. A cylindrical gas passage 9 having a large passage cross-sectional area at the center and the smallest passage cross-sectional area at both ends is formed between the inner peripheral surface and the inner peripheral surface.

An annular groove 10 is formed in the center of the inner circumferential surface of the stator 7, and a plurality of air supply passages 11 are formed that penetrate the stator 7 in the radial direction so as to open into the annular groove 10. Furthermore, the air supply passage 11 on the inner peripheral surface of the motor case 1
An annular passage 12 is formed at a position facing the motor case 1, and is connected to a gas supply source (not shown) via a through hole 13 passing through the motor case l and an air supply plug 14 screwed into the through hole 13. This gas supply source has the ability to supply gas such that the flow velocity at the outlet ends of both ends of the gas flow path 9 is higher than the speed of sound, and the supersonic gas bearing 15 is configured in the gas flow path 9. .

Although the features are illustrated in an extreme manner in FIG. 1 for easy viewing, the bearing clearance between the rotor 6 and stator 7 is 0.1+
It is on the order of ++m, and even at the maximum gap in the center it is 0.
It is approximately 2 to 0.4 ms+.

In the above configuration, when the stator coil 7a is driven by flowing current, the radial load of the rotor 6 and rotating shaft 3 is supported by the supersonic gas bearing 15 on the outer periphery of the rotor 6 in a non-contact manner. At this time, since the gas flow velocity at the outlet end of the gas flow path 9 is made sonic or supersonic using the supersonic gas bearing 15, as shown by the solid line in FIG. The pressure can be discontinuous with the surrounding pressure (usually atmospheric pressure), which is shown as a diagonal line, compared to being continuous with the surrounding pressure as shown with a dashed line in normal hydrostatic gas bearings. A larger load capacity can be obtained by the area. In addition, since the supersonic gas bearing 15 utilizes the inertial force of gas,
Compared to conventional hydrostatic gas bearings that utilize viscous force, it is possible to ensure greater rigidity even with a larger gap. By increasing the bearing gap in this way, high-precision rotation can be maintained for a long period of time even if the machining accuracy is not high, and since a large amount of gas flows through the gas flow path 9, heat generation due to eddy current loss in the rotor 6 is reduced. Even if this occurs, it can be effectively cooled, thermal expansion can be reduced, and a high-speed motor can be realized.

On the other hand, the thrust load acting on the rotating shaft 3 is supported by a thrust bearing 5 having an appropriately configured structure. Note that a similar supersonic gas bearing may also be applied to this thrust bearing.

Next, a specific example of the structure of the rotor 6 will be explained with reference to FIG.

A plurality of laminated cores 21 are fixed with clamp bins 22, and a permanent magnet 23 is externally fitted and fixed to the outer periphery of the laminated iron core 21, and a stainless steel pipe 24 is externally fitted and fixed to the outer periphery. This rotor 6 is constructed by fixing a laminated iron core 21 with a plurality of clamp bins 22, then shrink-fitting a permanent magnet 23 and a stainless steel vibrator 24, and then
Manufactured by caulking 2. Stainless steel vibe 24 is 1
It is made by forming a stainless steel plate with a thickness of about 1.5 mm into a cylindrical shape and welding it into a pipe shape. A rotor 6 made up of the stainless steel vibe 24, permanent magnets 23, and laminated iron core 21 is fixed to the rotating shaft 3 by shrink fitting. after that,
A non-cylindrical machined surface 8 that forms a gas flow path 9 of the supersonic gas bearing 15 between the outer circumferential surface of the stainless steel vibrator 24 and the inner circumferential surface of the stator 7 is machined.

In the example shown in FIG. 3, the through hole 13 communicating with the gas supply source extends toward the rear end of the motor.

In the above embodiment, an example was shown in which the gas passage 9 was formed as a non-cylindrical machined surface 8 on the outer periphery of the rotor 6 and a cylindrical surface on the inner periphery of the stator 7, but conversely, the inner circumferential surface of the stator 7 was formed as a non-cylindrical machined surface, It goes without saying that the outer peripheral surface of the rotor 6 may be a cylindrical surface, or both may be non-cylindrical processed surfaces.

FIG. 4 explains the schematic configuration of an embodiment in which the present invention is applied to a spindle drive device in a milling machine. 31
is a spindle, and an end mill 32 is fitted to one end thereof. The spindle 31 is configured to be driven by a motor 33 disposed at its intermediate portion, and an ultrasonic gas bearing 36 is configured between a rotor 34 and a stator 35 of the motor 33. 37 is a gas supply passage that supplies gas to the supersonic gas bearing 36. Further, a thrust magnetic bearing 38 is disposed at the other end of the spindle 31. 39
is a protective rolling bearing that supports the spindle 11 when the bearing action is unstable.

In this embodiment, since the motor 33 is equipped with a radial bearing made of a supersonic gas bearing, the radial magnetic bearings on both sides of the motor in the conventional spindle drive device shown in FIG. 6 can be omitted, resulting in a much more compact configuration. It becomes.

In the above embodiment, a brushless DC motor was used as an example, but
It can be applied to any type of motor such as a transistor motor, hermetic motor, AC motor, electronic governor motor, coreless motor, etc.

Further, in the above embodiment, the present invention was applied to a motor, but it can also be applied to a magnetic bearing having the same configuration as a motor used to cope with higher speeds.
The load capacity of the bearing can then be reinforced.

Effects of the Invention According to the rotating device of the present invention, since the bearing fluid is a gas with low viscosity as described above, it is possible to cope with high-speed rotation with low friction. Since a bearing is used, the pressure at the bearing outlet end can be increased regardless of the surrounding pressure, and therefore sufficient rigidity and load capacity can be obtained even if the bearing gap is increased. As a result, by increasing the bearing clearance, there is no risk of the stator or rotor becoming locked even if there is thermal expansion.Furthermore, since the bearing clearance is large, sufficient cooling can be achieved by flowing a large amount of gas, and the cooling effect is improved. By making it large, thermal expansion can be reduced even if heat generation due to eddy current loss is large, and high speeds can be achieved.

Therefore, it is possible to provide a supersonic gas bearing between the stator and rotor of a high-speed rotating motor, and as a result, bearings are not required on both sides of the motor, making it possible to make the entire rotating device more compact. In addition, the natural frequency of the rotating shaft is large, so there is no fear of locking when passing through critical speeds, and the processing machine can be run at high speed.By increasing the speed of the processing machine, processing accuracy can be improved and processing time can be shortened. In addition, since the bearing clearance can be large, the machining precision of the stator and rotor does not need to be high, and the gas supply management does not have to be as precise as that of ordinary hydrostatic bearings, reducing costs. Demonstrate effects such as being able to achieve

[Brief explanation of the drawing]

FIG. 1 is a vertical side view showing the configuration of a motor in an embodiment of the present invention, FIG. 2 is a pressure distribution characteristic diagram of a supersonic gas bearing, and FIG. 3 is a vertical side view of a specific configuration example of the same embodiment. Fig. 4 is a longitudinal sectional front view of an embodiment in which the present invention is applied to a milling machine, Fig. 5 is a longitudinal sectional side view of a motor previously proposed by the applicant, and Fig. 6 is a longitudinal sectional front view of a conventional milling machine. be. 6.34...Rotor, 7.35...Stator, 15.36...Supersonic gas bearing.

Claims (1)

[Claims] A rotating device characterized in that a rotor is rotatably supported by a supersonic gas bearing interposed between a stator and a rotor.