JP2001268859A - High-speed rotation spindle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-speed rotation with a structure of rotation-driving a rotary shaft 2 by a large torque with an electric motor, and of a speed not lower than 100,000 revolutions per min (r.p.m) on top of that. SOLUTION: By the electric motor composed of a rotor 9 into which a rotary shaft 2 is inserted and fixed, and a stator 10 fixed to the inner surface of a housing 1, the shaft 2 is rotated. As a field magnet which constitutes the rotor 9, a manganese aluminum magnet is used. Since the tensile strength of the manganese aluminum magnet is large, it is not broken by centrifugal force caused by a high-speed rotation, and the above problem is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a high-speed spindle device which is rotated at a high speed of, for example, 100,000 min ^-1 (rpm) or more by an electric motor. Such a high-speed rotating spindle device is suitable for a machine tool such as a lathe for a machine tool for processing a dental handpiece or a minute component, or a machine tool such as a grinding machine and a drilling machine.

[0002]

2. Description of the Related Art For example, a treatment handpiece used by a dentist or a work handpiece used by a dental technician has been widely used which rotates a grindstone by the force of compressed air. In the case of such a conventional structure, a grindstone is attached to the tip, and a turbine blade fixed to a rotating shaft rotatably supported by a housing by a ball bearing is driven by the pressure of compressed air supplied into the housing. Drive rotationally. According to such a structure in which the rotating shaft is driven by compressed air, there is a limit to the high-speed rotation of the rotating shaft in consideration of securing a stable rotating speed.
The rotation speed is limited.

On the other hand, in order to reduce the discomfort of the patient during dental treatment or to improve the processing efficiency in processing dentures, it is required to increase the rotation speed of the rotating shaft.
In other words, it is required to increase the peripheral speed of the grindstone fixed to the tip of the rotating shaft so as to improve the sharpness and to reduce the cutting work in a short time. In the case of the conventional structure, if the amount of compressed air blown to the turbine blade is increased and the pressure is increased, the peripheral speed of the grindstone can be increased to some extent, but it is difficult to obtain a sufficient effect. In other words, when compressed air is used as the drive source for the rotating grindstone, the torque required to rotate this grindstone increases based on the cutting resistance during cutting of teeth and dentures by the grindstone, and the rotating shaft decelerates. And the cutting effect is reduced. In addition, the fluctuation of the torque based on the fluctuation of the contact surface pressure and the contact area of the contact portion between the tooth and the grinding wheel frequently and largely fluctuates the rotation speed of the rotating shaft, thereby increasing noise and other problems for the patient. Pleasure increases.

[0004] Under such circumstances, it is desired to use an electric motor as a drive source for a dental handpiece.
However, the strength of the field magnet constituting the rotor that rotates together with the rotating shaft is insufficient, and the end of the rotating shaft that fixes the grindstone, which is generated due to the imbalance of the field magnet, and the heat generated by the electric motor. Due to the effect of insufficient lubrication of the bearings supporting the rotating shaft, there is a limit to increasing the rotating speed of the rotating shaft. For this reason, conventionally, it was not possible to obtain high-speed rotation of 100,000 min ^-1 or more even in the case of a relatively small spindle device such as a dental handpiece.

[0005] Further, in order to cut a minute mechanical part, using a machine tool having a capacity corresponding to the size of the part to be processed is necessary from the viewpoint of securing processing accuracy.
Alternatively, it is preferable from the viewpoint of energy saving and resource saving. On the other hand, in the conventional case, a large machine tool that can process a large article even when processing a small mechanical component is often used. Such a condition requires excessive space and energy for the workpiece,
Moreover, it is difficult to ensure the processing accuracy, which is not preferable.

On the other hand, Nikkei BP, Inc.
No.544 of the technical magazine “Nikkei Mechanical” published in January
Nos. 38-39 describe that a high-speed rotary spindle device capable of rotating an axis of rotation at 50,000 min ^-1 using an electric motor as a drive source has been realized. In this structure, a samarium-cobalt sintered magnet is used as a field magnet constituting the rotor of the electric motor,
A laminated silicon steel sheet is used as the core of the stator.

[0007]

In the case of the high-speed rotating spindle device described in the technical magazine "Nikkei Mechanical" as described above, the structure using an electric motor as a driving source makes it possible to rotate at a higher speed than before. However, in order to realize higher-speed rotation far exceeding 50,000 min ^-1 , it is still desired to improve the following points.

The samarium-cobalt magnet forming the rotor of the electric motor has a density of about 8.4 g / cm ^3, which is as large as that of stainless steel, alloy steel, bearing steel, etc. forming the rotating shaft. Strength is 4.4 × 10 ⁷ N
/ M ^2, which is not necessarily a large value. When the density is high, the centrifugal force applied at the time of high-speed rotation is large, which leads to a large tensile stress acting inside. On the other hand, since the tensile strength is not sufficiently large, the high-speed rotating spindle device is as large as a dental handpiece.
It is difficult to achieve a rotation speed exceeding 70,000 min ^-1 even when the motor is incorporated in a mechanical device having a relatively small diameter (the outer diameter of the rotor is about 10 mm). That is, a rotor incorporating a samarium-cobalt magnet as a field magnet during such high-speed rotation breaks due to hoop stress, and therefore cannot be rotated at high speed.

The samarium-cobalt magnet constituting the rotor of the electric motor has a linear expansion coefficient of 8 to 11 × 10
⁻⁶ / ° C., which is almost the same as, or rather smaller than, the linear expansion coefficient (10 to 17 × 10 ⁻⁶ / ° C.) of the stainless steel, alloy steel, bearing steel, and the like that constitute the rotating shaft. Therefore, the amount of thermal expansion of the rotor based on heat generation during operation of the high-speed rotating spindle device is equal to or smaller than the amount of thermal expansion of the rotating shaft to which the rotor is fixed. For this reason, when the rotor is externally fitted and fixed to the rotating shaft without a gap, the rotating shaft strongly presses the inner peripheral surface of the rotor diametrically outward when the temperature rises, and the hoop stress further increases. , The allowable rotation speed decreases. In order to prevent an increase in hoop stress based on such a difference in coefficient of thermal expansion,
It is conceivable that the fitting state between the rotating shaft and the rotor is a clearance fit, and the rotor and the rotating shaft are fixed with an adhesive. However, in this case, the rotation speed used is limited by the adhesive strength of the adhesive (the hoop stress is reduced by the difference in linear expansion coefficient between the rotating shaft and the adhesive and between the rotor and the adhesive. At the same time, the adhesive part is subjected to shearing force, and if the stress is large, the adhesive part peels off.

For these reasons, 100,000 min
^A high-speed rotary spindle device capable of obtaining a rotational speed much exceeding 70,000 min ^-1 has not been realized. In view of such circumstances, the present invention has been made to realize a high-speed rotary spindle device capable of obtaining a rotational speed of 100,000 min ^-1 or more.

[0011]

A high-speed rotating spindle device according to the present invention includes a housing, a rotating shaft, a rotor, and a stator, similarly to a conventionally known spindle device. The rotating shaft is rotatably supported inside the housing by a bearing such as a ball bearing or a hydrostatic or hydrostatic bearing. The rotor has a field magnet and is fixed to an outer peripheral surface of the rotating shaft.
The stator is provided at a portion of the inner peripheral surface of the housing that faces the outer peripheral surface of the rotor. In particular,
The high-speed rotating spindle device of the present invention is used under the condition that the maximum rotational speed of the rotating shaft is 100,000 min ^-1 or more, and the field magnet constituting the rotor is made of manganese aluminum.

[0012]

According to the high speed rotary spindle device of the present invention configured as described above, even when the rotor is used under the condition that the maximum rotational speed is 100,000 min ^-1 or more, the rotor can be used for the following reasons. Can be prevented from being damaged.

First, the tensile strength of manganese aluminum constituting the field magnet is 2.9 × 10 ⁸ N / m
^{About 2} times, which is at least 6 times larger than the tensile strength (about 4.4 × 10 ⁷ N / m ² ) of samarium cobalt constituting the field magnet incorporated in the conventional structure described above. For this reason, even if the same tensile stress is applied, no breakage occurs.

Second, the density of the manganese aluminum is:
The density is about 5.1 g / cm ³ , which is smaller than the density of the samarium cobalt (about 8.4 g / cm ³ ). For this reason, even if the rotation speed is the same, the generated centrifugal force is reduced, and accordingly, high-speed rotation is possible.

Third, the linear expansion coefficient of the manganese aluminum is about 20 to 22 × 10 ⁻⁶ / ° C., which is much larger than the linear expansion coefficient of samarium cobalt (8 to 11 × 10 ⁻⁶ / ° C.). Also, the coefficient of linear expansion of the stainless steel, alloy steel, bearing steel, etc. constituting the rotating shaft is sufficiently larger than the linear expansion coefficient (10 to 17 × 10 ⁻⁶ / ° C.). Therefore, the amount of thermal expansion of the rotor based on heat generation during operation of the high-speed rotating spindle device is equal to or smaller than the amount of thermal expansion of the rotating shaft to which the rotor is fixed. Therefore, even if the rotor is externally fitted and fixed to the rotating shaft without any gap, the rotating shaft does not strongly press the inner peripheral surface of the rotor outward in the diameter direction when the temperature rises, and acts on the rotor. An increase in hoop stress can be suppressed, and a decrease in allowable rotation speed can be prevented. Further, the rotor can be fixed to the rotating shaft by press-fitting, shrink-fitting of the rotor, cold fitting of the rotating shaft, or the like. Because of this,
As in the case where the rotor and the rotating shaft are fixed with an adhesive, the allowable rotation speed is not limited by the adhesive strength of the adhesive.

Due to these synergistic effects, the permissible rotational speed of the high-speed rotary spindle device of the present invention is as large as that of a dental handpiece when incorporated in a relatively small-diameter mechanical device whose outer diameter of the rotor is approximately 10 mm. It reaches about 230,000 min ^-1 . In the case of the conventional structure using the samarium-cobalt magnet rotor described above, the allowable rotation speed under the same conditions was about 70,000 min ^-1 , whereas in the case of the present invention, the allowable rotation speed was three times or more. The rotation speed can be obtained.

[0017]

FIG. 1 shows a first embodiment of the present invention. This example shows a case where the present invention is applied to a high-speed rotating spindle device incorporating a brushless DC motor. Rotating shaft 2 inside housing 1
Is rotatably supported by a pair of ball bearings 3, 3 corresponding to the bearing described in the claims. The inner races 4, 4 constituting the respective ball bearings 3, 3 have step portions 5, 5, each of which has an outer end surface (an end surface on the opposite side in the axial direction) formed near the middle end of the rotary shaft 2. To prevent displacement in the direction away from each other. On the other hand, the inner end surfaces (end surfaces facing each other in the axial direction) of the outer races 6, 6 constituting each of the ball bearings 3, 3 correspond to step portions 7, 7 formed on the inner circumferential surface of the opening of the housing 1. , Directly or via a preload spring 8. With this configuration, preload is applied to the two ball bearings 3, and the rotating shaft 2 is rotatably supported inside the housing 1 without rattling. The two ball bearings 3, 3 are filled with a lubricant such as grease so that the two ball bearings 3, 3 rotate smoothly with a small force.

A portion of the intermediate portion of the rotary shaft 2 located on the inner peripheral side of the housing 1 between the pair of ball bearings 3, 3 is made of manganese aluminum, which is a feature of the present invention. A rotor 9 composed of a field magnet is externally fitted and fixed by interference fit. On the other hand, a stator 10 is supported and fixed on a portion of the inner peripheral surface of the housing 1 facing the outer peripheral surface of the rotor 9. This stator 1
No. 0 is constituted by winding an armature coil 12 around a laminated core 11 formed by laminating a number of magnetic metal thin plates in the axial direction. The armature coil 12 is connected to a motor inverter 13 to constitute a high-speed rotary spindle device that drives the rotary shaft 2 to rotate based on energization.

At the time of using the high-speed rotary spindle device constructed as described above, the motor inverter 13 is fixed to a tip (right end in FIG. 1) of the rotary shaft 2 with, for example, a grindstone for dental treatment supported. Then, the armature coil 12 is energized. As a result, the rotating shaft 2 to which the rotor 9 is fixedly fitted is rotated at a high speed exceeding 100,000 min ^-1 . Although a large centrifugal force acts on the rotor 9 with this high-speed rotation, in the case of the high-speed rotation spindle device of the present invention, since the rotor 9 is made of a manganese aluminum magnet, this rotor 9 There is no destruction.
This will be described in detail below.

Conventionally, a rare earth magnet such as samarium cobalt or a ferrite magnet has been used as a field magnet constituting the rotor of the electric motor. On the other hand, in the case of the present invention, a manganese aluminum magnet is used as a field magnet constituting the rotor 9. Manganese aluminum magnets, among rare-use magnets that do not use rare elements such as cobalt, can be obtained at a low tensile strength,
Has excellent mechanical strength including compressive strength, high-speed rotation,
Withstands high-load operating environments. Moreover, the manganese aluminum magnet is preferable as a material constituting the rotor of the electric motor because it has good machinability and has a variety of magnetizations.

Among such excellent properties of the manganese aluminum magnet, the tensile strength, which is particularly important for high-speed rotation of the rotating shaft, is shown in FIG. 2 in comparison with the samarium-cobalt magnet. As apparent from FIG. 2, the tensile strength of the manganese aluminum magnet used in the high-speed spindle device of the present invention is much higher than the tensile strength of the samarium-cobalt magnet used in the conventional high-speed spindle device. For example, in order to withstand a large hoop stress generated when a rotary shaft having an outer diameter of about 10 mm and externally fixedly mounted thereon is rotated at a high speed exceeding 100,000 sec ⁻¹ , a field constituting the rotor is required. 200 for magnetic magnet
A tensile stress of × 10 ⁶ N / m ² or more is required. As apparent from FIG. 2 based on this numerical value, the manganese aluminum magnet used in the present invention satisfies this condition, but the samarium cobalt magnet conventionally used does not satisfy this condition.

FIG. 3 shows the relationship between the rotation speed of a rotor made of a manganese aluminum magnet or a samarium cobalt magnet and having an outer diameter of 10 mm, and the hoop stress based on the centrifugal force generated with the rotation. I have. The samarium-cobalt magnet conventionally used has a high density (8.4 g).
/ Cm ³ or so), since the allowable limit tensile strength to increase significant centrifugal force and hoop stress with increasing rotation is low,
It can only rotate up to about 70,000 min ^-1 . On the other hand, in the case of the manganese aluminum magnet used in the present invention, the density is low (about 5.1 g / cm ³ ), the centrifugal force and the hoop stress increase slowly with the increase in rotation, and the allowable limit is increased. Due to its high tensile strength, it can be rotated up to about 230,000 min ^-1 . That is, in the case of the present invention using a manganese aluminum magnet, it is possible to rotate about 3.3 times as fast as the conventional case using a samarium cobalt magnet.

Next, FIG. 4 shows the relationship between the outer diameter of the rotor and the rotation when the rotor is rotated at 70,000 min ^-1 which is the maximum rotation speed obtained by a rotor of a samarium cobalt magnet having an outer diameter of 10 mm. 2 shows the relationship with the hoop stress based on the centrifugal force generated with the above. When the rotor is made of a samarium-cobalt magnet, the rotor is broken by centrifugal force when the outer diameter is 10 mm, whereas when the rotor is made of a manganese aluminum magnet, the outer diameter can be increased to 35 mm. . This leads to an increase in the degree of freedom in designing a high-speed rotating spindle device.

In addition, in the case of the present invention, the linear expansion coefficient of the manganese aluminum magnet constituting the rotor 9 is 20 to 22 × 1.
0 ⁻⁶ / ° C., which is the linear expansion coefficient (8 to 11 × 10 ⁻⁶ /) of the samarium-cobalt magnet constituting the rotor in the conventional case.
C.), and a combination larger than the linear expansion coefficient (10 to 17 × 10 ⁻⁶ / ° C.) of the steel material forming the rotating shaft 2 becomes possible. By realizing such a combination (the coefficient of linear expansion of the material forming the rotor 9 is made larger than the coefficient of linear expansion of the material forming the rotating shaft 2),
Even when the rotating shaft 2 thermally expands due to heat generated by the operation of the high-speed spindle device, the rotor 9 thermally expands more, so that the hoop stress applied to the rotor 9 increases (which is larger than that based on centrifugal force). No) never.

In the case of the high-speed rotating spindle device of the present invention, as described above, the amount of thermal expansion of the rotor 9 is made larger than the amount of thermal expansion of the rotating shaft 2, so that the rotor 9 is The attachment can be a fixed fit by an interference fit. Therefore, there is no need to use an adhesive as in the above-described conventional structure, and the allowable maximum rotation speed is not limited by the adhesive strength of the adhesive.

On the other hand, the product obtained by winding the armature coil 12
What laminated | stacked the silicon steel plate in the axial direction as the layer core 11
I'm using High speed by incorporating such laminated core 11
When the electric motor of the rotary spindle device is configured,
Suppress the generation of eddy current and reduce heat generation and rotational resistance
Can do things. In particular, the use of such a laminated core 11
The effect of the combination with the rotor 9 made of manganese aluminum magnet
100,000 min in total^{- 1} When realizing the above high-speed rotation
And more remarkably.

Grease lubrication is suitable for lubrication of the ball bearings 3, 3 in order to improve maintainability. A preferable grease that can be used in this case is, for example, NS High Lube (trade name) manufactured by Kyodo Yushi Co., Ltd. This grease reduces the rotational resistance and reduces the above-mentioned ball bearings 3,
The rolling resistance of the bearing 3 is reduced (reduced torque), and it is possible to contribute to realization of high-speed rotation of the rotating shaft 2 supported by each of the ball bearings 3.

In order to further increase the speed, it is preferable to use ceramic as the material of the balls 14 constituting the ball bearings 3. The reason is as follows. When an electric motor composed of the rotor 9 and the stator 10 is used as a drive source of the rotating shaft 2 rotatably supported by the ball bearings 3, 3, the respective ball bearings 3, The oil film existing in the contact portion between the rolling surface of each of the balls 14, 14 and the inner raceway provided on the outer peripheral surface of the inner race 4 and the outer raceway provided on the inner peripheral surface of the outer race 6 May become thinner. Each ball 14, 1
If a ceramic having a smaller density than the commonly used bearing steel is used as the material of the material 4, the centrifugal force acting on each of the balls 14, 14 during rotation of the rotary shaft 2 is reduced, and each of the ball bearings is used. It is possible to suppress the load applied to the third and third components and to suppress the increase in the amount of generated heat. In addition, each ball 14, 1
In the case where 4 is made of ceramic, even if the oil film existing in the contact portion becomes insufficient, it is possible to prevent metal materials of the same kind from coming into contact with each other and to improve friction resistance and seizure resistance. , Speeding up can be achieved. By forming the inner race 4 and the outer race 6 from stainless steel, it is possible to improve the corrosion resistance of the ball bearings 3 including the inner race 4 and the outer race 6.

Since a preload is applied to each of the ball bearings 3 and 3 by the preload spring 8, positioning in the axial direction is accurately performed, and deflection of the rotary shaft 2 is suppressed.
The sliding of each of the balls 14, 14 can be suppressed. still,
As a method for applying a preload to each of the ball bearings 3 and 3, when high speed is required, a constant pressure preload method using an elastic material such as a preload spring 8 is suitable as shown. On the other hand, for applications requiring high rigidity, fixed position preload for fixing the inner races 4, 4 and the outer races 6, 6 constituting the ball bearings 3, 3 at predetermined positions is preferable. In addition, as the direction of applying the preshoot, a back-to-back combination in which the action point distance with respect to the rotating shaft 2 is large and the load capability against moment load is excellent is suitable, but when assembly workability of a high-speed rotating spindle device is required. Can also adopt a front combination.

When the high-speed rotation spindle device of the present invention is implemented, when the rotation speed becomes high, the unbalanced force due to the imbalance affects the rotation performance, so that the rotation shaft 2 and the rotor 9 are assembled. Therefore, it is necessary to remove the imbalance and perform a balance correction operation. As shown in FIG. 5, for example, as shown in FIG. 5, the parts for fixing the inner rings 4, 4 of the ball bearings 3, 3 at the both ends of the rotating shaft 2 are supported by jigs 31, 31, for example. It is performed in the state of having done. Then, by rotating the rotary shaft 2 and the rotor 9 and correcting the balance by using the outer peripheral surface of a portion near the rotor 9 at the intermediate portion of the rotary shaft 2 or both end surfaces of the rotor 9 as a correction surface, proper Can make balance corrections.
In order to perform such a balance correcting operation, it is preferable to provide an unbalance correcting section on the rotating shaft 2. or,
When the balance is corrected by shaving off a part of the rotating shaft 2 or the rotor 9 using a grinder or the like,
The shape of the shaved part in the circumferential direction should be streamlined,
It is desirable to minimize wind noise. Further, the rotor 9
After externally fixing the rotor 9 to the rotary shaft 2, the outer peripheral surface of the rotary shaft 2 is polished by supporting a portion to which the inner rings 4, 4 are to be externally fixed. The coaxiality with the outer peripheral surface can be improved.

Next, FIG. 6 shows a case where the high-speed rotary spindle device of the present invention using an electric motor as a drive source as shown in FIG. 1 is used, and a conventional high-speed rotary spindle device using compressed air as a drive source. 2 shows the characteristics of the load torque and the output rotation speed during machining. In any case,
The outer diameter of the rotating shaft 2 is 3.175 mm, the axial length is 30 mm,
The outer diameter of the rotor 9 is 10 mm and the outer diameter of the housing 1 is 25 mm
And Ball bearings 3 for supporting the rotating shaft 2
Has an inner diameter of 3.175 mm, an outer diameter of 6.350 mm, a width of 2.38 mm, a ball diameter of 1 mm, a number of balls of 7, and a material of 4 inner rings.
And SUS440C in which outer ring 6 is stainless steel, ball 1
Reference numerals 4 and 14 are ceramics Si ₃ N ₄ . The lubrication was grease lubrication by the NS high lube. Each of the ball bearings 3 was preloaded as a rear combination.
The balance correction of the rotating body combining the rotating shaft 2 and the rotor 9 is performed at a position of a radius of 3 mm by 0.001 g.
It was made as follows.

As is clear from FIG. 6 showing the results of experiments conducted under such conditions, according to the high-speed rotary spindle device of the present invention using an electric motor as a drive source as shown in FIG. The rotation state can be stabilized as compared with a conventional high-speed rotating spindle device used as a driving source. That is, when a load torque is applied to the rotating shaft 2, in the case of the conventional structure using compressed air as the driving source, the rotating speed of the rotating shaft decreases, and the rotating speed temporarily increases when the load is removed. However, in the case of the structure of the present invention using an electric motor as a drive source, the rotation speed of the rotating shaft 2 hardly changes regardless of the load state.

FIG. 7 shows a second embodiment of the present invention.
An example is shown. Since the basic structure of the present example is the same as that of the first example described above, the same parts are denoted by the same reference numerals as in FIG. 1 and duplicate description is omitted. In the case of this example,
The rotor 9 which is a manganese aluminum magnet and the rotating shaft 2 are attached and fixed by a combination of press-fitting and bonding. In order to secure the bonding strength, a plurality of concave grooves 25, 25 are formed on the outer peripheral surface of the intermediate portion of the rotary shaft 2, and an adhesive is interposed in each of the concave grooves 25, 25.
Such a configuration is effective for increasing the tolerance when the linear expansion coefficient of the manganese aluminum magnet forming the rotor 9 is significantly larger than the linear expansion coefficient of the steel material forming the rotating shaft 2. That is, the rotor 9 is connected to the rotating shaft 2,
When the outer fitting is fixed only by the interference fit, it is necessary to strictly control the assembly tolerance between the outer diameter of the rotating shaft 2 and the inner diameter of the rotor 9 in consideration of a change in interference due to thermal expansion. On the other hand, in the case of the present embodiment, by using the bonding together, it is possible to increase the tolerance between the outer diameter and the inner diameter, thereby reducing the cost.

As a metal thin plate constituting the laminated core 11 around which the armature coil 12 is wound, a silicon steel sheet to which 6.5% by weight of silicon (Si) is added is used. The use of a silicon steel sheet containing 6 to 7% by weight of silicon in an iron-based alloy makes it possible to reduce the core loss, reduce magnetostriction, increase magnetic permeability, stabilize quality, and ensure non-directionality. By improving various required characteristics, a high-performance electric motor can be realized. And the rise to the rated high-speed rotation speed is fast, and the ON-O
It is possible to realize a high-speed rotating spindle device suitable for applications where FF is repeated. As described above, as the silicon steel sheet in which 6 to 7% by weight of silicon is added to the iron-based alloy, for example, NK Super E core (trade name, silicon content: 6.5% by weight) manufactured by NKK can be used. .

The lubricant for lubricating each of the ball bearings 3 is made of a material having a very small effect on the human body, for example, poly-α-olefin (PAO), IS
It is desirable to use liquid paraffin such as VG32 and VG68 in O standard. When grease lubrication is used as the lubrication method, it is effective to use a double-sided seal in which seal plates are provided at both ends in the axial direction of each of the ball bearings 3 and 3 from the viewpoint of preventing grease leakage. Alternatively, as shown in FIG. 7, a one-sided seal structure in which a seal plate 15 is provided only on the end face side of the rotating shaft 2 among the axial end portions of the ball bearings 3 is used. Providing the grease holding space 16 on the side of the opening 3 is also effective from the viewpoint of preventing grease leakage.
In the case of adopting such a structure, the method of supplying grease from the lubricant supply device 30 through the lubricant supply hole 17 also requires the amount of grease present in each of the ball bearings 3, 3 to be increased over a long period of time. It is effective from the aspect of securing sufficient.

Also, a cushioning material such as an O-ring 18 may be interposed between the outer peripheral surface of the outer ring 6 of one or both of the ball bearings 3 and the inner peripheral surface of the housing 1 to enhance the vibration isolation effect and to increase the rotation. This is effective from the viewpoint of suppressing the unbalance of the parts and the vibration caused by the external force.

It is desirable to provide a dustproof mechanism in order to prevent foreign substances such as tooth treatment cutting powder generated when used as a dental handpiece from entering the inside of the handpiece. Such a dustproof mechanism includes a seal plate 1 provided on each of the ball bearings 3 for preventing grease leakage.
In addition to 5 and 15, it is conceivable to provide labyrinth seals 28, 28, an air seal, and the like between the housing 1 and the rotating shaft 2. In addition, compressed air is sent from the compressed air supply device 29 into the housing 1 to increase the pressure in the housing 1, and the bearings 3, 3
It is also effective to reduce the airflow that enters inside as much as possible. Such a structure suppresses a temperature rise of each of the ball bearings 3 and 3 irrespective of heat generation of the electric motor, and the oil film thickness inside each of the ball bearings 3 and 3 and the rigidity of each of the ball bearings 3 and 3 It is also effective to secure

As shown in FIG. 7, it is possible to minimize the space volume in the housing 1 and to mold the armature coil 12 with a coating 19 made of synthetic resin to make the surface smooth.
This is effective for reducing wind noise and windage loss generated when the rotor 9 rotates at high speed. In this example, the attachment portion 21 for the tool or the work 20 is provided directly at the end of the rotating shaft 2. However, in order to improve the handling, a separate rotation provided with such an attachment portion 21 is provided. It is also possible to adopt a structure in which the shaft is formed separately from the rotating shaft 2 provided in the handpiece main body, and the separate rotating shaft is driven by a coupling device groove such as a coupling.

FIG. 8 shows a third embodiment of the present invention.
As an example, a case where the present invention is applied to a small machine tool for processing a small workpiece is shown. Since the basic structure of this example is also the same as that of the above-described first example or the above-mentioned second example, the same parts are denoted by the same reference numerals as in FIGS. In the case of this example, a cooling cover 22 is provided on the outer peripheral surface of the housing 1 in order to suppress a temperature rise due to heat generated in the electric motor and the ball bearings 3 and 3 formed by the rotor 9 and the stator 10. I am wearing it. Then, inside the cooling cover 22 (between the inner peripheral surface of the cooling cover 22 and the outer peripheral surface of the housing 1), a coolant such as oil, water, or air is supplied to the cooling medium supply device 2.
It can be sent freely from 3. The type of the refrigerant is selected in consideration of cost, heat absorption, workability, and the like. A rotation speed sensor 24 is mounted on a portion of the inner surface of the housing 1 facing the rotor 9 so that the rotation speed of the rotating shaft 2 can be measured.

In the case of the present embodiment, the ball bearings 3, 3
Is performed by a slight amount of lubrication such as oil-air lubrication to reduce the rotational torque of each of the ball bearings 3 and 3 so as to realize high speed. Alternatively, as a method of lubricating each of the ball bearings 3, 3, a method in which a lubricant is directly or mixed with air and sent into the inside of each of the ball bearings 3, 3 about once a day may be adopted. it can. Of course, as in the case of the above-described second example, grease can be sent in.

In the first and second examples of the above-described embodiment, the balls 14, 14 constituting each of the ball bearings 3, 3 are made of ceramic, so that these ball bearings 3, 3 are formed. Even if the oil film existing in the contact portion becomes insufficient, the same kind of metal material is prevented from coming into contact with each other, and the friction resistance and seizure resistance are improved and the speed is increased. On the other hand, when the present invention is applied to a machine tool as in this example, in order to increase the support rigidity of the rotating shaft 2, the preload is applied to each of the ball bearings 3, 3 by a fixed position preload. Often done. In such a case, if the balls 14, 14 incorporated in the respective ball bearings 3, 3 are made of ceramic, due to a difference in thermal expansion between the metal inner ring 4 and the outer ring 6 when the temperature rises, There is a possibility that pre-emption may occur. For this reason, when performing the fixed-position preload, the balls 14, 14 have little (or no) difference in the amount of thermal expansion between the inner ring 4 and the outer ring 6.
Made of steel (each having a linear expansion coefficient in the range of 10.1 to 13.5 × 10 ⁻⁶ ) or having a large linear expansion coefficient (10.5
× 10 ⁻⁶ ) It is necessary to use ceramic such as zirconia. In this case, if there is a possibility that lubricity may not be sufficiently ensured, the rolling surfaces of the balls 14, 14 may be nitrided,
It is effective to prevent the metal materials of the same kind from contacting each other by performing a surface treatment with a coating such as ceramic or DLC (diamond-like carbon). In the case of this example, it is preferable that the preload application direction of each of the ball bearings 3 is a back-to-back combination in order to obtain a large rigidity.

When used as a machine tool, the rotational speed and torque of the rotary shaft 2 affect the finished surface and the processing accuracy. Therefore, it is necessary to control the rotational speed to improve the accuracy of the processed surface. May be. Therefore, in the case of the present embodiment, a magnetic sensor 26 for controlling the rotation speed of the rotating shaft 2 and a rotation speed control device 27 are provided. The rotation speed of the rotating shaft 2 is measured by the magnetic sensor 26 that detects the magnetism of the field magnet that forms the rotor 9 and a rotation speed control device 27 that receives a signal from the magnetic sensor 26. Then, based on the measured value, an appropriate amount of electric power for the target rotation speed is supplied to the motor inverter 13.
To the armature coil 12. The rotation speed sensor 24 used for detecting the rotation speed is a magnetic sensor 2 as described above.
6, a displacement sensor or an optical sensor may be used. Furthermore, depending on the application, the rotation speed can be detected by using the amount of current supplied to the armature coil 12 without using a sensor.

[0043]

Since the present invention is constructed and operates as described above, it is possible to rotate at a high speed exceeding 100,000 min ^-1 which has been difficult in the past, and to improve the performance of various mechanical devices. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first example of an embodiment of the present invention.

FIG. 2 is a graph showing a comparison between the tensile strength of a manganese aluminum magnet and the tensile strength of a samarium cobalt magnet.

FIG. 3 is a diagram showing the influence of the rotational speed on the tensile stress generated in a manganese aluminum magnet rotor and the tensile stress generated in a samarium cobalt magnet rotor when a rotor having an outer diameter of 10 mm is formed.

FIG. 4 is a graph showing the effect of the outer diameter of the rotor on the tensile stress generated in a manganese aluminum magnet rotor and the tensile stress generated in a samarium cobalt magnet rotor when the rotation speed is set to 70,000 min ^−1. FIG.

FIG. 5 is a side view showing a state in which a rotating body formed by externally fixing the rotor to the rotating shaft is balanced;

FIG. 6 shows that when the rotating shaft is rotated at 200,000 min ⁻¹ , the load torque applied to the rotating shaft is determined by the rotation speed of the rotating shaft driven by the electric motor and the rotation of the rotating shaft driven by compressed air. FIG. 4 is a diagram illustrating an effect on speed.

FIG. 7 is a sectional view showing a second example of the embodiment of the present invention.

FIG. 8 is a sectional view showing the third example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Rotating shaft 3 Ball bearing 4 Inner ring 5 step part 6 Outer ring 7 step part 8 Preload spring 9 Rotor 10 Stator 11 Laminated core 12 Elementary coil 13 Motor inverter 14 Ball 15 Seal plate 16 Grease holding space 17 Lubricant supply hole 18 O-ring 19 coating 20 work 21 mounting part 22 cooling cover 23 cooling medium supply device 24 rotation speed sensor 25 concave groove 26 magnetic sensor 27 rotation speed control device 28 labyrinth seal 29 compressed air supply device 30 lubricant supply device 31 jig

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F16C 25/08 F16C 25/08 Z 5H019 H01F 1/04 H02K 21/14 M 5H621 H02K 21/14 29/00 Z 5H622 29/00 H01F 1/04 Z (72) Inventor Hideo Okano 1-50, Kumeinuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3C045 FD08 3J012 AB02 AB06 BB01 CB03 DB13 FB10 HB02 3J103 AA02 AA13 AA21 CA13 CA62 CA78 DA05 EA08 FA01 FA12 FA14 GA02 GA52 HA03 HA06 HA15 HA16 HA32 HA33 HA37 4C052 AA06 BB02 CC03 CC12 5E040 AA09 CA01 NN15 5H019 AA05 CC03 5H621 HH01 JK17 5H622 AA03 CA01 PP05

Claims (1)

[Claims] 1. A housing, a rotating shaft rotatably supported inside the housing by a bearing, a rotor having a field magnet fixed to an outer peripheral surface of the rotating shaft, and an inner peripheral surface of the housing. And a stator provided at a portion facing the outer peripheral surface of the rotor. The high-speed spindle device used under the condition that the maximum rotation speed of the rotation shaft is 100,000 min ^-1 or more, A high-speed rotating spindle device characterized in that the field magnets constituting are made of manganese aluminum.