JPH03270666A - Spindle motor - Google Patents

Abstract

PURPOSE:To enhance durability by introducing pressurized air through pores of a fixed ceramic member into a gap between the rotary ceramic member of a rotor and the fixed ceramic member. CONSTITUTION:Opposed magnets 18, 19 repel from each other to be separated through a micro gap S1 thus regulating the movement of a rotary shaft 12 in the longitudinal direction. Air is pressure fed from a blower through a flow-in hole 11 into the space 23 of a motor chamber 7. The air flows from the space 23 through a vent 21 into a micro space S2 thence flows through the micro space S1 and flow-out holes 10, 11 to the outside. Consequently, static air pressure is produced in the micro space S2 and thereby the outer circumferential face at the opposite ends of the rotary shaft 12 is separated from the inner circumferential faces of the air flow-out holes 10, 11 through a space S3 and held in place.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a small spindle motor.

[Prior Art] Conventionally, in small spindle motors mainly used for dental medical instruments, the motor shaft placed inside the motor case is
It is rotatably supported on a part of the motor case via radial and thrust bearings, and the rotation of the motor shaft is transmitted to a rotating member such as a drill attached to the outer end of the motor shaft. There is.

[Problems to be Solved by the Invention] However, ball bearings are used in the bearings, and the balls are subject to severe wear due to the high-speed rotation of the motor shaft, so the service life is short, and the bearings must be used every year, or even every six months in some cases. Therefore, the problem remains that the replacement work is not only complicated but also uneconomical.

The present invention has been made to solve the above problems, and its purpose is to provide a spindle that has a long service life and hardly requires replacement, and is therefore highly economical and suitable for high-speed rotation. Our goal is to provide motors.

[Means for Solving the Problems] In order to achieve the above object, the spindle motor of the present invention includes a power transmission shaft, a plurality of N poles and S poles around the shaft, and magnetic poles adjacent to each other are different from each other. A field magnet arranged in an annular shape so that A rotating body formed by integrally fixing a pair of first magnetic members disposed through the rotating ceramic member, and a rotating body disposed outside the rotating ceramic member to restrict movement of the rotating body in the radial direction so as to allow the rotating body to rotate. a cylindrical fixed ceramic member for supporting; a pair of second magnetic members disposed on both sides of the rotary body to restrict movement of the rotary body in the thrust direction; a stator armature that drives a rotating body in cooperation with a field magnet; further, a thrust bearing is configured by magnetic pole repulsion between the first magnetic member and the second magnetic member; The gist is that pressurized air is introduced into the gap between the fixed ceramic member and the rotating ceramic member through small holes provided in the fixed ceramic member to construct a hydrostatic radial bearing.

[Operation] Therefore, when the rotating body is rotationally driven by the cooperation between the field magnet provided in the rotating body and the stator armature,
Pressurized air is introduced into the gap between the rotating ceramic member and the fixed ceramic member of the rotating body through the small holes in the fixed ceramic member. Further, the rotating body is rotated in both the radial direction and the thrust direction due to magnetic pole repulsion of the first and second magnetic members while maintaining a non-contact state with respect to each member surrounding the rotating body. Therefore, the wear of the members constituting the motor is minimized, durability is increased, and high-speed rotation is possible.

Further, since the rotating body has a structure in which a field magnet is provided between the power transmission shaft and the rotating peripheral ceramic member, the diameter of the spindle motor can be reduced, and the overall size of the spindle motor can be easily reduced.

Furthermore, since the rotating circumferential ceramic member and fixed circumferential ceramic member of the rotating body interposed between the field magnet and the stator armature are formed of ceramic materials, the relationship between the field magnet and the stator armature is The rotating body can be rotated smoothly without adversely affecting magnetic interaction.

Further, it is preferable that the magnetic bearing is formed by an annular magnet. The reason for this is that installation is easy and the entire motor can be made smaller. Furthermore, it is desirable that the outer peripheral portions of the hydrostatic bearing and the rotating body be made of ceramics.

The reason for this is that it has excellent durability against the heat generated when the rotating body rotates.

The gas supplied to the static pressure radial bearing is preferably air. The reason for this is that it can be easily done manually. Inert gases such as nitrogen can also be used.

It is preferable that the balance adjustment body is a leakage magnetic flux prevention body made of a magnetic material that prevents leakage magnetic flux in the axial direction of the field magnet.

As a result, the magnetic interaction between the field magnet and the stator armature is enhanced, and the rotating body is rotated smoothly.

It is desirable that the balance adjustment body has a recess formed therein for removably mounting a balancer thereon.

This makes it possible to adjust the balance of the rotating body as appropriate.
The rotating body is adjusted to the optimum state.

comprising a detection element that detects the magnetic pole of the field magnet,
It is preferable to control energization to the stator armature based on the detection of this magnetic pole.

Thereby, the spindle motor can be used without brushing, and the life of the motor can be improved.

Furthermore, examples of the ceramic material used for the rotating ceramic member and the fixed ceramic member include non-magnetic materials such as sintered silicon carbide material, sintered alumina material, and sintered silicon nitride material. According to these, the durability against the frictional heat generated by the sliding contact between the respective members is increased during the time when the rotating body is started, and the life of the spindle motor can be extended until the gas bearing is activated.

In particular, when using silicon carbide sintered material with excellent mechanical strength, it is possible not only to reduce the thickness of each ceramic member and downsize the entire motor, but also to dramatically improve wear resistance. The motor can be improved and have a longer lifespan.

Further, it is desirable that the gap formed between the rotating ceramic member and the stationary ceramic member of the rotating body is in the range of 3 to 20 μm. If it is less than this range, the rotating body will not be able to rotate, and if it exceeds this range, the entire motor will become larger or the rotating body will become loose when rotating, which will hinder high-speed rotation.

[Embodiment] An embodiment in which the present invention is embodied in a brushless type spindle motor will be described in detail below with reference to the drawings.

In the brushless type spindle motor shown in FIG. An O-ring 3 seals the space between the two surfaces. Further, a mounting ring 4 extending over the entire inner peripheral surface is formed at the other end of the cylindrical member 1, and a second closing plate 5 disposed on the outside thereof is fixed to the ring 4 with a plurality of screws 6. The other end of the cylindrical member 1 is closed. A motor chamber 7 is formed within the cylindrical member 1 in a region closed by the closing plate 2.

As shown in FIG. 2, a plurality of air inlet holes 8 are transparently provided in the first closing plate 2, and an external blower (
(not shown) to the motor chamber 7 of the cylindrical member 1 shown in FIG.
Air is pumped inside.

Furthermore, two through holes 9a are provided in the first closing plate 2.

For example, hoses for feeding air and water for dental treatment are routed from 9b to the second closing plate 5, bypassing the motor chamber 7, and air and water are injected outward from the second closing plate 5. It has become so.

Furthermore, circular air outflow holes 10 and 11 are formed in the center of each of the closing plates 2 and 5, respectively. and,
As shown in FIG. 1, a rotating shaft 12 extending in the length direction is disposed within the motor chamber 7, and one end of this rotating shaft 2 has its outer circumferential surface disposed within one outflow hole IO, and its inner circumferential surface The outer peripheral surface of the other end is loosely inserted into the inner peripheral surface of the other outflow hole 11 with a space s3 therebetween, and protrudes outward.

In the motor chamber 7, a rotating body R is attached to the rotating shaft 12. To explain this rotating body R, annular bushes 13 as balance adjusting bodies are fixed on the circumferential surfaces of both ends of the rotating shaft I2, and a rotating magnet 14 as a field magnet is held between these bushes 13. has been done. As shown in FIG. 3, this magnet 14 is composed of four permanent magnet pieces 15 having different magnetic poles arranged alternately in the circumferential direction. Further, as shown in FIG. 1, an annular fitting step portion 16 is formed in the outer layer of the opposing portion of each of the bushes I3, and a groove formed of a silicon carbide sintered material is formed between the bushes 13. A cylindrical cover 17 as a rotating ceramic member is fitted, thereby surrounding the outer peripheral surface of the rotating magnet 14. A plurality of recesses are formed on the outer circumferential surface of each bush 13 for removably mounting a balancer (not shown), and the load balance of the rotating body R is arbitrarily adjusted.

Furthermore, annular magnets 18 as first magnetic members are fixed to the outer surfaces of both bushes 13, and step portions 2 are provided on the first and second closing plates 2 and 5, respectively, facing the annular magnets 18.
Similarly, an annular magnet 19 as a second magnetic member is fitted in a and 5a. These opposing magnets 1
8.19 are used with different magnetic poles, and due to the repulsion of both magnets 18.19, the magnet 18 on the bushing 13 side is separated from the magnet 19 on the closing plates 2 and 5 side by a minute space S1, and the rotating shaft 12 Movement in the longitudinal direction is restricted. The bush 13, the rotating magnet 14, the cylindrical cover 17, and the magnet 18 constitute a rotating body R, and both the magnets 18 and 19 constitute a thrust magnetic bearing.

Between the opening plates 2 and 5, both ends of an enclosing member 20 as a fixed ceramic member made of a silicon carbide sintered material are supported so as to surround the rotating body R, and the inner peripheral surface and the rotating member A small space S between the body R and the outer peripheral surface of the cylindrical cover 17
2 communicates with the aforementioned microspace S1. Also,
The enclosing member 20 has Hall elements H arranged in a circumferential direction embedded in the central part in the length direction of the outer circumferential surface, and a plurality of ventilation holes 21 are provided in the inner circumferential surface of the cylindrical member I. A microspace S2 is communicated with a space 23 between the yoke Y and the outer peripheral surface of the surrounding member 20.

Then, the air is fed under pressure to each air outlet hole 10.11 of the first and second closing plates 2 and 5 via the air inflow hole 8 of the first closing plate 2 → ventilation hole 21 → minute space S2 → minute space S1. Due to the air pressure, each end of the rotating shaft 12 is held at a position where the outer circumferential surface is separated by a space S from the inner circumferential surface of the air outlet hole 10.11.

Note that the minute space S2 between the outer circumferential surface of the cylindrical cover 17 and the inner circumferential surface of the surrounding member 20 is shown wider than the actual size (approximately 3 μm) in the drawing to emphasize the air flow path. Both 17 and 20 are in sliding contact 1 through air, and the minute space S2 is extremely narrow to the extent that air leaks. Then, the cylindrical cover 17 and the ventilation hole 2
1 constitutes a radial air bearing.

Three coils 22 are arranged in the circumferential direction on the outer peripheral surface of the surrounding member 20, and when a Hall element (not shown) detects the magnetic pole of the magnet piece 15, the direction of the current flowing through the coils 22 is switched as appropriate. The rotating body R is controlled to rotate in one direction, either forward or reverse.

Now, on the left and right sides of the spindle motor configured as described above, due to the repulsion of the magnets 18 and 19 facing each other, both the magnets 18 and 19 are separated from each other by a minute distance S1, thereby regulating the movement of the rotating shaft 12 in the longitudinal direction. are doing. In addition, the air forced from the blower flows through the air inlet hole 1.
1 into the space 23 of the motor chamber 7. and,
Air flows from the space 23 through the ventilation hole 21 to the microspace S2.
From there, it passes through the small space S1 of the aircraft to the air outflow hole IO.
, 11 to the outside. Therefore, static pressure of air is generated in the micro space 82, and the rotating shaft 12 is maintained in a state in which the outer circumferential surface of its end is separated from the inner circumferential surfaces of both air outlet holes 10.11 by a space S3. be done.

Therefore, when the coil 22 is energized and the rotating body R is rotated in a predetermined direction based on the detection of the magnetic pole of the magnet piece 15 by the Hall element H, the rotating shaft 12 is The repulsive force of the magnets 18 and 19 applies a load in the thrust direction, and the air in the space S3 receives a load in the radial direction. Therefore, unlike the ball bearings used in conventional products, the non-contact structure prevents wear and deterioration of the bearings, eliminating the need for replacement even if the spindle motor is used for a long period of time.

Further, since the cylindrical cover 17 and the surrounding member 20 interposed between the field magnet 14 and each electromagnetic coil 23 are formed of a non-magnetic silicon carbide sintered material, the field magnet 14 and each electromagnetic coil 23 are The rotating body R is rotated smoothly without any waste without adversely affecting the magnetic interaction with the coil 24.

The diameter of the cylindrical member 1 in this example is 22wn, which is extremely small, the thrust load capacity is 100g, the radial load capacity is 2000g, and the number of rotations used is 3000-4.
0000 rpm, static pressure generation air pressure is 3.0
kg/car.

In this embodiment, a brushless type small spindle motor has been described as an example, but it is also possible to adopt a brush type motor and omit the Hall element H.

[Effects of the Invention] As described in detail above, the present invention has the effect that the bearing means has a long service life and there is no need to replace it, which is excellent in economical efficiency.

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing a spindle motor of the present invention;
FIG. 2 is a side view thereof, and FIG. 3 is a sectional view taken along the line ■-■ in FIG. 1. 12... Power transmission shaft, 13... Bush as a balance adjustment body, 14... Rotating magnet 1 as a field magnet 17... Cylindrical cover as a rotating ceramic member 18... No. 1: an annular magnet as a magnetic member; 19: an annular magnet as a second magnetic member; 20: an enclosing member as a fixed peripheral ceramic member; 23: an electromagnetic coil as a stator armature.

Claims (1)

[Claims] 1. A power transmission shaft (12);
2) a field magnet (14) in which a plurality of N poles and S poles are arranged in an annular shape such that adjacent magnetic poles are different poles, and the outer peripheral surface of the field magnet (14); A cylindrical rotating ceramic member (17
) and a pair of first magnetic members (18) arranged at both ends of the rotating ceramic member (17) via a pair of balance adjusting bodies (13), respectively, are integrally fixed to each other. and disposed outside the rotating ceramic member (17),
A cylindrical fixed ceramic member (20) that rotatably supports the rotating body (R) by restricting movement of the rotating body (R) in the radial direction; A pair of second magnetic members (
19), disposed outside the fixed ceramic member (20);
The rotating body (R
), further comprising a stator armature (23) that drives the first magnetic member (18) and the second magnetic member (1
A thrust bearing is constructed by magnetic pole repulsion between the fixed ceramic member (20) and the fixed ceramic member (20) through a small hole (21) provided in the fixed ceramic member (20). A spindle motor in which pressurized air is introduced into a gap with a ceramic member (19) to form a static pressure radial bearing. 2. The spindle motor according to claim 1, wherein the balance adjusting body (13) is a leakage magnetic flux prevention body made of a magnetic material that prevents leakage magnetic flux in the axial direction of the field magnet (14). . 3. The spindle motor according to claim 1 or 2, wherein the balance adjustment body (13) is formed with a recess (B) for removably mounting a balancer thereon. 4. Claim 1, further comprising a detection element (H) for detecting the magnetic pole of the field magnet (14), and controlling energization to the stator armature (23) based on the detection of the magnetic pole. Or the spindle motor according to 2.