JP2002253576A - Dental handpiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in a conventional dental handpiece or the poor space efficiency within the handpiece because the rotator of the bearing-less motor of the conventional handpiece is rotated in contact with a stator when a pneumatic control circuit has a trouble at starting or the like, and has a plurality of rotating speed detection sensors and signal transmission lines. SOLUTION: This dental handpiece comprises a winding group 13 for generating a torque in a stator 27, a winding group for generating a radial force in the above winding group, and a radially moving rotator 12 having a magnetic pole permanent magnet arranged within the stator, and the rotator 12 is arranged on the main axis within a housing arranged on the circumference of the stator. The torque generating winding of the stator has the function of detecting the induced voltage of the winding to estimate the radial position, a circuit for detecting and integrating the generated voltage of the stator winding, the function of detecting this value, the function of detecting the rotating angle and position of the rotator by an electronic circuit, and the function of driving an inverter circuit by the rotating angle. The circuit has the function of supplying the voltage or current synchronized to the rotating angle position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an instrument for dental treatment, and more particularly to a dental handpiece using a bearingless motor.

[0002]

2. Description of the Related Art Conventionally, in a bearingless motor, a rotor is held in a non-contact manner in a radial direction by sending compressed air to a gap around a rotor sleeve and a bearing sleeve so that the rotor floats in a non-contact manner. Had set the shaft with permanent magnets. Further, when the motor is stopped, the stator and the rotor are in contact because the compressed air is not sent. Further, the rotational speed of the shaft is measured by arranging a plurality of detection sensors.

[0003]

However, the supply of the compressed air for holding the rotor in a non-contact manner with the compressed air and the structure of the rotor sleeve and the bearing sleeve are complicated and require precision machining. In addition, the setting of the shaft by the permanent magnet in the thrust direction was complicated and required precision machining. When the motor is stopped, the stator and the rotor are in contact with each other since there is no compressed air. In addition, the detection sensors for detecting a plurality of rotation speeds and the transmission of the signals have reduced the space efficiency in a limited handpiece and have been troublesome. The present invention provides a dental handpiece that solves these problems.

[0004]

DISCLOSURE OF THE INVENTION In view of the above, the present invention, etc.
As a result of intensive experimental research, this problem was solved by the following means. An instrument for tooth cutting in dental treatment, a motor used for a micromotor handpiece (hereinafter referred to as a dental handpiece), which integrates an inner rotor type motor and a magnetic bearing function into a motor body, A bearingless motor having no independent bearing mechanism, comprising: (1) a group of windings for generating torque on a stator;
The winding group of the stator includes a winding group that generates a radial force or one winding group, and inside the stator, silicon steel or solid steel in which permanent magnets that constitute magnetic poles are disposed. A rotor configured to perform a rotary motion and move in a radial direction, such as an iron core, and further, a housing is configured on an outer periphery of the stator, and the rotor is mounted on a main shaft in the housing. The main shaft is provided with a structure connected to a dental handpiece, and the main shaft has an interaction with a magnetomotive force generated by supplying a current to the stator winding group. A function to generate torque and radial force by adjusting the current amplitude and phase;
The radial force has a function of adjusting the position of the rotor in the radial direction or suppressing vibration in the radial direction, and the torque has a function of adjusting the rotation speed of the rotor. Dental handpiece. (2) A high-frequency sine wave voltage or a high-frequency voltage generated by PWM is superimposed on the stator torque generating winding, and the self-inductance or the mutual inductance changes depending on the radial position of the rotor. By detecting the induced voltage generated at the winding terminal,
The dental handpiece according to (1), which has a function of estimating a radial position from the detected induced voltage and does not require a radial position sensor.

(3) It has a function of detecting a voltage generated in the winding of the stator, a circuit for integrating the voltage and a function of detecting an integrated value of the voltage, and an analog or digital electronic circuit for the rotor. It has a function of detecting a rotation angle position and a function of driving an inverter circuit based on the detected rotation angle, and the inverter circuit has a function of supplying a voltage or a current synchronized with the rotation angle position of the rotor. The dental handpiece according to (1) or (2), which does not require a rotation angle position sensor of the rotor such as a Hall element. (4) A metal plate or a net-like good conductor is disposed on the permanent magnet disposed on the rotor, and a damping force due to eddy current is generated when the main shaft is displaced (1) to (3). The dental handpiece according to any one of the preceding claims. (5) The bearingless motor according to any one of (1) to (4), wherein the bearingless motor is a two-axis control in which a function of generating torque is added to a radial position control magnetic bearing. The dental handpiece as described. (6) The bearingless motor according to any one of (1) to (5), wherein two two-axis control motors are arranged in series and four-axis control is performed to control each motor. Dental handpiece.

(7) At the end of the motor shaft, there is disposed an annular permanent magnet having opposite poles for suppressing axial displacement and radial displacement, and is housed in the housing of the micromotor handpiece. When the motor stops and rotates,
The dental handpiece according to any one of (1) to (6), wherein contact between the stator and the rotor is eliminated. (8) At the end of the motor shaft, a plurality of ring-shaped permanent magnets slightly different in the direction in which the diameter increases with the same pole opposing the same pole that suppresses axial displacement and radial displacement are arranged stepwise. The method according to any one of (1) to (7), wherein the stator is accommodated in a housing of the micromotor handpiece so that the contact between the stator and the rotor is eliminated when the motor stops and rotates. Dental handpiece. (9) At the end of the motor shaft, a truncated conical permanent magnet whose upper and lower surfaces are hollow, with the same poles obliquely opposed to suppress axial displacement and radial displacement, is placed inside the housing of the micromotor handpiece. The dental handpiece according to any one of (1) to (8), wherein the stator and the rotor are not in contact with each other when the motor is stopped and rotated. (10) On both shafts of the motor, an annular touch-down bearing having abrasion resistance which prevents the rotor and the stator from coming into contact with each other when the motor is stopped is disposed vertically. A dental permanent magnet as set forth in any one of (1) to (6), wherein an annular permanent magnet having the same pole facing each other is disposed and housed in a housing of the motor handpiece. Handpiece.

[0007]

Embodiments of the present invention will be described with reference to the drawings. A bearingless motor that adds a function of generating torque to a two-axis control radial magnetic bearing that generates torque and two-axis electromagnetic force in the radial direction by one electromagnetic machine is described in (IEEJ Vol. 117, No. 9, 1997). "Bearingless motors" by Tadashi Fukao and Akira Chiba) and sensorless control of bearingless motors (February 25, 1999, IEEJ, Linear Drive Workshop, "Sensorless control of bearingless motors" by Tadashi Fukao,
Akira Chiba, Kazufumi Muronoi) and others,
Regarding a permanent magnet which is disposed obliquely with respect to an axial direction and a radial direction which suppresses axial displacement and radial displacement, and which are integrally arranged (Japanese Patent Laid-Open No. 10-306823).
"A permanent magnet and a magnetic levitation support structure using the permanent magnet"). Furthermore, measurement of the number of rotations of a shaft without using a detection sensor is described in "Transistor Technology, February 2000," Method of Driving a Sensorless DC Motor "by Satoshi Kusaka.
And so on. However, the above was an independent matter. The present invention makes use of the features of each of these items, and in particular, a novel and inventive dental motor handpiece that is housed together in a housing of a dental micromotor handpiece that is required to be lightweight and small and that high speed rotation is required. I will provide a.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external view of a dental handpiece (two-axis control bearingless motor / permanent magnet / straight type handpiece) of the present invention, and a longitudinal sectional view of a detachable fitting portion and a bearingless motor storage portion. Hereinafter, the dental handpiece of the above case is referred to as a micromotor handpiece.
In the drawing, 1 is a micromotor handpiece, 2 is a front part of the handpiece, 3 is a detachable adapter, 4 is an O-ring, 5 is a motor clutch, 6 is a retaining ring, 7 is a detachable part, and 8a is a shaft-side thrust. A permanent magnet, 8b is a case-side thrust permanent magnet, 9a is a shaft-side radial permanent magnet, 9b is a case-side radial permanent magnet, 10b.
Is a sleeve, 11 is a water pipe, 12 is a rotor, 13 is an armature winding of a stator, 14 is a motor case, 15 is a water coupling, 16 is an air coupling, 17 is an air passage, 18 is an electric signal pin, 19 Is a ramp, 20 is a shaft, 27 is a stator,
28 is a gap, 29 is a plug portion, and 36 is a bearingless motor.

As shown in FIG. 1, in the micromotor handpiece 1, the handpiece front part 2 and the motor case 14 accommodating the bearingless motor 36 can be attached and detached at the attachment / detachment portion 7, and the micromotor handpiece 1 can be used for medical treatment. Water injection into the teeth,
Blowing of air or the like can be performed in the same manner as in the related art.
The bearingless motor 36 is disposed at the center of the motor case 14, and the shaft 20 is disposed at the center when viewed from the front and rear. At both ends, an annular shaft-side radial permanent magnet 9a is orthogonal to the shaft 20. It is fixed. The inner diameter of the annular case-side radial permanent magnet 9b faces the outer periphery of the annular permanent magnet with a small gap therebetween. The magnets repel each other with the same polarity, and hold the entire upper, lower, left, and right circumferences of the shaft 20 in a non-contact manner even during rotation and stop.

An annular shaft-side thrust permanent magnet 8a is disposed outside each of the radial permanent magnets 9a of the shaft 20, and a ring-shaped permanent magnet 8a fixed to the end of the detachable adapter 3 is provided at a position facing the permanent magnet 8a. The thrust permanent magnet 8b and the annular thrust permanent magnet 8b disposed on the plug portion 29 face each other with a gap. The above magnets repel each other with the same polarity, and hold the thrust directions before and after the shaft 20 in a non-contact manner even during rotation and stop. As described above, the rotor 12 is always kept in a non-contact state.

FIG. 2 is a cross-sectional view of FIG. 1A-A '.
In the figure, 21a is an N-pole permanent magnet embedded in the rotor, 21b is an S-pole permanent magnet embedded in the rotor, 22
Is a four-pole motor winding, 23 is a two-pole position control winding, 24 is the stator tooth, 25 is the direction of the wire from the other side to the front, 26
Is the direction of traffic from the near side to the other side, NU / NV / NW
Is 1/4 of 3 phase 4 pole, NUb / NVb / NWb is 3
One-half of the phase 2 pole, φs indicates the direction of rotation. The armature winding 13 (FIG. 1) of the stator: the four-pole motor winding 22 and the two-pole position control winding 23 (FIG. 2) are wired as shown in the figure. The motor used for the instrument for cutting teeth (micromotor handpiece 1) in the dental treatment shown in FIGS. 1 and 2 integrates an inner rotor type motor and a magnetic bearing function into the motor main body, and becomes independent. Bearingless motor with no bearing mechanism

The motor includes a stator armature winding 13 (FIG. 2) for supporting and rotating the rotor 12 in a non-contact manner, and an N-pole permanent magnet 21a and an S-pole permanent magnet 21b. As shown in FIG. 2, the rotor 12 is buried at right angles and symmetrically in all directions.
Each of the permanent magnets 21a and 21b of S is a long and long plate-like integrated type. Instead, a large number of narrow plate-like permanent magnets are arranged at small intervals, and are embedded shallowly along the circumference. ,
Further, a structure in which a permanent magnet is not inserted in two places between the respective poles may be employed (not shown). Further, the radial position control of the rotor 12 is performed by generating a force acting in a radial direction from the center of the rotor by unbalancing the rotating magnetic field and performing a radial position control winding (bipolar position control). Winding 2
3), in addition to the motor windings (4-pole motor windings 22) of the armature of the motor stator, and another set of windings (2-pole position control windings) different from the number of poles of the motor. 2
3), the current flowing through the winding distorts the magnetic flux distribution in the air gap 28 between the stator 27 and the rotor 12, and generates a radial force on the rotor due to the distortion of the magnetic field distribution. A mechanism for magnetically holding the rotor,

The four-pole motor winding 22 and the two-pole position control winding 23 are provided on one stator, and the mutual inductance between the two windings is proportional to the displacement of the rotor 12. High-frequency current (for example, 20 kc)
A carrier wave generated by an oscillator, and superimpose the two-pole position control winding 2
3 to detect the induced voltage proportional to the rotor displacement and to use the estimated value of the radial displacement of the rotor 12 for feedback to realize non-contact support of the main shaft. When,

Further, a comparator for detecting the position of the rotor 12 from the induced voltage generated in the armature winding of the stator 27 (generated voltage detection function, voltage integration circuit and detection function of the same integral value), and a rotor Sensorless arithmetic circuit (with the function of detecting the rotation angle position of an analog or digital electronic circuit) which receives the position detection signal and outputs drive timing, output transistor control circuit (a circuit that drives an inverter circuit based on the detected rotation angle) And a three-phase inverter circuit (a function of supplying a voltage or current synchronized with the rotation angle of the rotor) by an output transistor that supplies a drive current to the motor, and does not require a rotation angle position sensor such as a Hall element. It is a sensorless DC motor. The above is an outline of a bearingless motor having various functions based on the above-mentioned documents.

FIG. 3 is a cross-sectional view taken along the line AA 'of FIG. 1 in which a good conductor of a metal plate is disposed on a permanent magnet disposed on a rotor of a bearingless motor. In the figure, 25 indicates a metal plate. As shown in the figure, the basic configuration is the same as that of FIG. 2 described above, except that the N-pole permanent magnet 21a and the S-pole permanent magnet 21b embedded in the rotor 12 are additionally provided with a good conductor metal plate 25. Are arranged. In place of the above-mentioned metal plate, a mesh-like metal or a flat sheet-like one in which many coils are formed and arranged in a plane may be used.
With this configuration, when the main shaft is displaced, current flows due to eddy current, and a damping force is generated.
The support of the main shaft is easy.

A bearingless motor is basically a two-axis control in which a torque generating function is added to a radial position control magnetic bearing. In a two-axis control bearingless motor, displacement in the radial direction is reduced. Since the shaft tilt cannot be controlled only by controlling the shaft, the tilt of the shaft is suppressed by permanent magnets that suppress the radial displacement at both ends (Fig. 1). Then, the inclination of the axis can also be controlled. FIG. 4 is a longitudinal sectional view in which a four-axis control bearingless motor and a permanent magnet are combined. As shown in the figure, the bearingless motor 36 is configured by arranging two motors of the two-axis control shown in FIG. 1 in series and performing four-axis control for controlling each of the motors. In addition to controlling, the inclination of the axis can be controlled. Therefore, during rotation, only the axial displacement needs to be suppressed by the permanent magnets 8a and 8b at both ends. In order to avoid contact between the rotor 12 and the stator 13 when stopped, permanent magnets 9a and 9b are provided on both sides of the shaft to suppress displacement in the radial direction.

FIG. 5 is a longitudinal sectional view in which a two-axis control bearingless motor and an annular permanent magnet are combined in a stepwise manner. In the figure, reference numeral 30a denotes a small outside diameter annular permanent magnet for a motor shaft, 31c denotes a large outside diameter annular permanent magnet, 30b denotes a small inside diameter annular permanent magnet for a stator, and 31d denotes a large inside diameter annular magnet for a stator. As shown in the figure, an annular permanent magnet (small outer shaft for the motor shaft 20) having a slightly different diameter in the direction in which the diameter of the motor shaft 20 faces the same pole that suppresses axial displacement and radial displacement is slightly increased. Annular permanent magnet 30
a, a plurality of large-diameter annular permanent magnets 31c, a small-diameter annular permanent magnet 30b for the stator, and a large-diameter annular magnet 31d for the stator are arranged in a plurality of steps, and are provided inside the housing of the micromotor handpiece 1. When the motor is stopped and rotating,
Eliminates contact between stator and rotor.

FIG. 6 is a longitudinal sectional view of a combination of a two-axis control bearingless motor and a truncated conical permanent magnet having a hollow upper and lower surface. In the drawing, reference numeral 32 denotes a frustum-shaped permanent magnet for a motor shaft, and 33 denotes a frustum-shaped permanent magnet for a stator. As shown, the motor shaft 20
A frusto-conical permanent magnet having a hollow upper and lower surface (oblique frustum-shaped permanent magnet 3 for a motor shaft) having diagonally opposite poles for suppressing axial displacement and radial displacement,
2. The frustoconical permanent magnet 33) for the stator is housed in the housing of the micromotor handpiece 1 to eliminate the contact between the stator and the rotor when the motor stops and rotates.

FIG. 7 is a longitudinal sectional view in which a four-axis control bearingless motor, a permanent magnet and a touchdown bearing are combined. In the figure, reference numeral 34 denotes an annular touchdown bearing for a stator, and reference numeral 35 denotes an annular touchdown bearing for a motor shaft. As shown in the drawing, the shaft-side thrust permanent magnet 8a and the case-side thrust permanent magnet 8b as the annular permanent magnets for axial displacement suppression are made to face the ends of the motor shaft 20 and the case 14 with the same poles. It is arranged. In addition, opposite ends of the stator 27 and the motor shaft 20 are opposed to each other to prevent wear of the rotor 12 and the stator 27 when the motor is stopped. An annular touchdown bearing 34 for the motor and an annular touchdown bearing 35) for the motor shaft are disposed and housed in the housing of the motor handpiece 1.

[0020]

According to the present invention, the following excellent effects are exhibited. 1. According to the invention of claim 1 of the present invention, in an instrument for cutting teeth in dental treatment, a motor used for a micromotor handpiece includes a winding group that generates torque on a stator, A rotor that has a winding group or a single winding group that generates a radial force in the winding group, and performs a rotary motion in which a permanent magnet constituting a magnetic pole is disposed inside the stator and moves in a radial direction. The rotor is disposed on a main shaft in a housing formed on the outer periphery of the stator, and the main shaft has a structure connected to a dental handpiece, and supplies current to a stator winding group. By adjusting the current amplitude and phase of the winding group by the interaction with the magnetomotive force generated by the function, the function of generating the torque and the radial force, and the radial force adjusts the rotor position in the radial direction Or radial Function of suppressing vibration and torque, to become a function of adjusting the rotational speed of the rotor, when the rotor is eccentric from the center of the stator can be controlled around the rotor. According to the second aspect of the present invention, a high-frequency sine wave voltage or a high-frequency voltage generated by PWM is superimposed on a winding for generating torque of the stator, and the self-inductance depends on the radial position of the rotor. Alternatively, a function of detecting an induced voltage generated at the winding terminal due to a change in mutual inductance and a function of estimating a radial position from the detected induced voltage are provided, so that a radial position sensor is not required. .

According to the third aspect of the present invention, a function for detecting a voltage generated in the winding of the stator, a circuit for integrating the voltage, and a function for detecting an integrated value of the voltage are provided. The electronic circuit has a function of detecting the rotation angle position of the rotor and a function of driving the inverter circuit based on the detected rotation angle, and the inverter circuit supplies a voltage or current synchronized with the rotation angle position of the rotor. Since the function is provided, a rotation angle position sensor for a rotor such as a Hall element is not required. According to the fourth aspect of the present invention, a metal plate or a net-like good conductor is disposed on the permanent magnet disposed on the rotor, and when the main shaft is displaced, a damping force due to eddy current is generated. Can be suppressed. According to the fifth aspect of the present invention, since the bearingless motor is a two-axis control in which a function of generating torque is added to the radial position control magnetic bearing, the rotor is magnetically supported with a simple structure. Can be. According to the sixth aspect of the present invention, the bearingless motor has two biaxially controlled motors arranged in series and controls each of them.
Since the axis control is performed, the tilt of the axis can be controlled in addition to the displacement in the radial direction.

According to the seventh aspect of the present invention, the end of the motor shaft is provided with a ring-shaped permanent magnet facing the same pole for suppressing axial displacement and radial displacement, thereby providing a micro motor hand. Since the pieces are housed in the housing, the contact between the stator and the rotor can be eliminated when the motor stops and rotates. According to the eighth aspect of the present invention, the end of the motor shaft is provided with an annular permanent magnet that is slightly different in a direction in which the diameter is increased with the same pole facing the same pole for suppressing the axial displacement and the radial displacement. A plurality of stairs are arranged and housed in the housing of the micromotor handpiece. Therefore, with a simple structure, the contact between the stator and the rotor can be eliminated when the motor stops and rotates. According to the ninth and ninth aspects of the present invention, at the motor shaft end,
A frustoconical permanent magnet whose upper and lower surfaces are hollow and whose upper and lower surfaces are obliquely accommodated in the housing of the micromotor handpiece, which suppresses axial and radial displacements, is oriented in one direction. In addition, the contact between the stator and the rotor can be eliminated when the motor stops and rotates. According to the tenth aspect of the present invention, an annular touch-down bearing having abrasion resistance is provided on both shafts of the motor so as to prevent contact between the rotor and the stator when the motor is stopped. In addition, a ring-shaped permanent magnet facing the same pole that suppresses axial displacement is provided and housed in the housing of the motor handpiece, so that when the motor stops, wear of the stator and the rotor can be eliminated. .

[Brief description of the drawings]

FIG. 1 is an external view of a dental handpiece (two-axis control bearingless motor / permanent magnet / straight handpiece) of the present invention, and a longitudinal sectional view of a detachable fitting portion and a bearingless motor storage portion.

FIG. 2 is a cross-sectional view of FIG. 1A-A ′.

FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. 1 in which a good conductor of a metal plate is disposed on a permanent magnet disposed on a rotor of the bearingless motor.

FIG. 4 is a longitudinal sectional view in which a four-axis control bearingless motor and a permanent magnet are combined.

FIG. 5 is a longitudinal sectional view in which a two-axis control bearingless motor and an annular permanent magnet are combined in a stepwise manner.

FIG. 6 is a longitudinal sectional view of a combination of a two-axis control bearingless motor and a truncated conical permanent magnet having a hollow upper and lower surface.

FIG. 7 is a longitudinal sectional view in which a four-axis control bearingless motor, a permanent magnet, and a touchdown bearing are combined.

[Explanation of symbols]

1: Micro motor handpiece 2: Handpiece front part 3: Adapter for attachment / detachment 4: O-ring 5: Motor clutch 6: Retaining ring 7: Attachment / removal part 8a: Permanent magnet for shaft-side thrust 8b: Permanent magnet for case-side thrust 9a: Permanent magnet for shaft side radial 9b: Permanent magnet for case side radial 10: Sleeve 11: Water guide pipe 12: Rotor 13: Armature winding of stator 14: Motor case 15: Water joint 16: Air joint 17: Air passage 18: Electric signal pin 19: Lamp 20: Shaft 21a: N-pole permanent magnet embedded in rotor 21b: S-pole permanent magnet embedded in rotor 22: 4-pole motor winding 23: 2-pole Position control winding 24: Stator teeth 25: Direction of wire from the back to the front 26: Direction of wire from the front to the back 27: Fixed 28: Void 29: Plug part 30a: Small outer diameter annular permanent magnet for motor shaft 30b: Small inner diameter annular permanent magnet for stator 31c: Large outer diameter annular permanent magnet 31d: Large inner diameter annular magnet for stator 32: Motor shaft Frustoconical permanent magnet for stator 33: frustoconical permanent magnet for stator 34: annular touchdown bearing for stator 35: annular touchdown bearing for motor shaft 36: bearingless motor NU / NV / NW: 3 phase 4 pole 1/4 pole NUb / NVb / NWb: 1/2 pole of 3 phase 2 poles φs: Rotation direction

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Kazunobu Ogawa, 2-1-2-4 Kamiochiai, Yono-shi, Saitama Prefecture Inside the Morita Tokyo Works (72) Inventor Hiroshi Sudo 2-1-2-24 Kamiochiai, Yono-shi, Saitama Stock A term A4 A11 AA13 AA20 BB02 CC12 GG02 GG17 GG21 5H019 AA05 BB01 CC03 DD01 DD04 DD07 DD10 FF03 5H607 AA12 BB01 BB09 BB14 BB26 J01 GG11 GG01 JK19 PP05

Claims (10)

[Claims] A stator having a winding group for generating torque;
Further, the winding group of the stator, a winding group that generates a radial force or a single winding group, inside the stator, silicon steel or permanent magnets that constitute a magnetic pole is disposed A rotor that performs a rotary motion and moves in a radial direction, which is configured by a solid iron core or the like, and further, a housing is configured on the outer periphery of the stator, and the rotor is provided in the housing. The stator is configured on a main shaft, and the main shaft has a structure connected to a dental handpiece. The main shaft has an interaction with a magnetomotive force generated by supplying a current to the stator winding group. The function of generating torque and a radial force by adjusting the current amplitude and phase of the group, and the function of adjusting the rotor position in the radial direction or suppressing the vibration in the radial direction, and The torque is Dental handpiece, characterized by comprising a function for adjusting the rotational speed of the child. 2. A high-frequency sine wave voltage or a high-frequency voltage generated by PWM is superimposed on a winding for generating torque of a stator, and a self-inductance or a mutual inductance depends on a radial position of the rotor. A function for detecting an induced voltage generated at the winding terminal by changing the position, and a function for estimating a radial position from the detected induced voltage, eliminating the need for a radial position sensor. 2. The dental handpiece according to 1. 3. A function for detecting a voltage generated in a winding of a stator, a circuit for integrating the voltage and a function for detecting an integrated value of the voltage, and the rotation of the rotor by an analog or digital electronic circuit. It has a function of detecting an angular position and a function of driving an inverter circuit based on the detected rotation angle, and the inverter circuit has a function of supplying a voltage or a current synchronized with the rotation angle position of the rotor, 3. The dental handpiece according to claim 1, wherein a rotation angle position sensor of a rotor such as a Hall element is not required. 4. A metal plate or a net-like good conductor is disposed on a permanent magnet disposed on a rotor, and when a main shaft is displaced, a damping force due to eddy current is generated.
4. The dental handpiece according to any one of the above items 3. 5. The bearingless motor according to claim 1, wherein the bearingless motor is a two-axis control in which a function of generating torque is added to a radial position control magnetic bearing.
The dental handpiece according to the above item. 6. The dental dental instrument according to claim 1, wherein two bearing-less motors are arranged in series and two-axis control motors are arranged in series, and four-axis control is performed to control each motor. Handpiece. 7. An endless end of the motor shaft is provided with an annular permanent magnet having opposite poles for suppressing axial displacement and radial displacement, and is housed in a housing of the micromotor handpiece. The motor according to claim 1, wherein when the motor stops and rotates, contact between the stator and the rotor is eliminated.
7. The dental handpiece according to any one of items 6 to 6. 8. A plurality of ring-shaped permanent magnets slightly different from each other in the direction in which the diameter increases with the same pole facing the axial direction and radial direction at the end of the motor shaft. The motor according to any one of claims 1 to 6, wherein the housing is housed in a housing of the micromotor handpiece, and when the motor stops and rotates, contact between the stator and the rotor is eliminated. Dental handpiece. 9. A micro motor handpiece is provided at the end of the motor shaft with a truncated conical permanent magnet having hollow upper and lower surfaces with the same poles for suppressing axial displacement and radial displacement obliquely facing each other. The dental handpiece according to any one of claims 1 to 6, wherein the dental handpiece is housed in a housing so that the stator and the rotor do not come into contact with each other when the motor stops and rotates. 10. An annular touchdown bearing having abrasion and wear resistance is provided on both shafts of the motor so as to prevent contact between the rotor and the stator when the motor is stopped. The dental hand according to any one of claims 1 to 6, wherein an annular permanent magnet whose opposite poles are suppressed to suppress displacement is provided and housed in a housing of the motor handpiece. piece.