JP4412444B2 - Dental handpiece - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an instrument for dental treatment, and more particularly to a dental handpiece using a bearingless motor.
[0002]
[Prior art]
Conventionally, in a motor for a micromotor handpiece that does not use a bearing, the rotor is held in a contactless manner by sending compressed air to the gap between the rotor sleeve and the bearing sleeve in the radial direction. The thrust direction was set by a permanent magnet. Moreover, since the compressed air was not sent when the motor stopped, the stator and the rotor were in contact. Furthermore, the rotational speed of the shaft was measured by arranging a plurality of detection sensors.
[0003]
[Problems to be solved by the invention]
However, the compressed air supply 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 precise machining, and the shaft is formed by a permanent magnet in the thrust direction. The set of was complicated and required precision machining. When the motor is stopped, since there is no compressed air, the stator and the rotor are in contact with each other, and there is a possibility that the motor rotates while in contact with the air control circuit at the time of start.
In addition, the detection sensors for a plurality of rotational speeds and the transmission of the signals have deteriorated the space efficiency in the limited handpiece and are troublesome. The present invention provides a dental handpiece that solves these problems.
[0004]
[Means for Solving the Problems]
In view of the above, the present inventors have solved this problem by the following means as a result of intensive experimental research.
An instrument for cutting teeth in dental treatment, and a motor used in a micromotor handpiece (hereinafter referred to as a dental handpiece) integrates an inner rotor type motor and a magnetic bearing function into a motor body, Ri Oh in the bearingless motor that does not have an independent bearing mechanism, is a dental handpiece of the following configuration.
(1) In the dental handpiece, comprising a coil group for generating a winding group and the radial force generates torque in the stator, the stator inside, silicon permanent magnets forming the pole is arranged it comprises a rotating element that moves performed and radially rotational movement which is composed of steel or solid iron core or the like,
Moreover, it said the stator outer periphery housing is configured, also, the rotor is configured on a motor shaft within the housing, the motor shaft is provided with a structure formed by connecting the dental handpiece Become
By adjusting the current amplitude and phase of the winding group by the interaction between the magnetomotive force generated by supplying current to the stator winding group and the magnetic force of the permanent magnet of the rotor , torque and radial force are adjusted. The radial force has a function of adjusting the rotor position in the radial direction or suppressing radial vibration, and the torque has a function of adjusting the rotational speed of the rotor. Do Ri,
Further, an annular permanent magnet facing the same pole that suppresses axial displacement and radial displacement is arranged at the end of the motor shaft, and is housed in the housing.
A dental handpiece in which contact between the stator and the rotor and the end of the motor shaft is eliminated when the motor is stopped and rotated .
(2) In the dental handpiece according to (1), instead of an annular permanent magnet facing the same pole that suppresses axial displacement and radial displacement at the end of the motor shaft,
A plurality of annular permanent magnets that are slightly different from each other in a direction in which the diameter is increased by facing the same pole that suppresses axial displacement and radial displacement at the end of the motor shaft are arranged in a step shape. dental handpiece said.
[0005]
(3) In the dental handpiece according to (1), instead of an annular permanent magnet facing the same pole that suppresses axial displacement and radial displacement at the end of the motor shaft,
A frustoconical permanent magnet with the upper and lower surfaces made hollow with the same poles that suppress axial displacement and radial displacement obliquely facing each other at the end of the motor shaft is housed in the housing of the micromotor handpiece. dental handpiece characterized in that it comprises Te.
(4) A high-frequency sine wave voltage or a high-frequency voltage generated by PWM is superimposed on the winding that generates the torque of the stator, and the self-inductance or the mutual inductance changes depending on the radial position of the rotor. Thus, it has a function of detecting an induced voltage generated at the winding terminal and a function of estimating a radial position from the detected induced voltage, and does not require a radial position sensor (1) to The dental handpiece according to any one of (3).
[0006]
(5) A function for detecting a voltage generated in the stator winding, a circuit for integrating the voltage, and a function for detecting an integrated value of the voltage, and a rotation angle position of the rotor by an analog or digital electronic circuit. And a function of driving an inverter circuit based on the detected rotation angle, the inverter circuit having a function of supplying a voltage or current synchronized with the rotation angle position of the rotor, and a Hall element The dental handpiece according to any one of (1) to (4), wherein a rotational angle position sensor of the rotor is not required.
(6) A permanent magnet disposed on the rotor is provided with a metal plate or a net-like good conductor, and when the motor shaft is displaced, a damping force due to an eddy current is generated (1) to (5) The dental handpiece according to any one of the above.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
A bearingless motor that adds a function to generate torque to a two-axis control radial magnetic bearing that generates electromagnetic force of two axes orthogonal to the torque and radial direction by one electromagnetic machine is (Vol. 117, No. 9, IEEJ, 1997) "Bearingless motor" by Fukao Tadashi and Akira Chiba) and sensorless control of bearingless motor (The Institute of Electrical Engineers of Japan, February 25, 1999, "Driverlessless sensor sensorless control" Fukao Tadashi, Chiba Akira, Kazufumi Muronoi), etc.
Further, regarding a permanent magnet in which an axial displacement and a radial displacement suppressing radial displacement are arranged so as to be obliquely opposed and integrated with each other (Japanese Patent Laid-Open No. 10-306823 “Permanent Magnet and this Permanent Magnet”). Magnetic levitation support structure using magnets ").
Furthermore, the measurement of the number of rotations of the shaft without using a detection sensor is described in (Transistor Technology February 2000 “Sensorless DC Motor Driving Method” by Satoshi Kusaka) and the like.
However, the above was an independent matter.
The present invention utilizes the characteristics of each of these matters, in particular the housing of the dental micromotor handpiece lightweight compact and high-speed rotation is required, together housed new and a progressive dental Ha Ndopisu and the Provide [0008]
【Example】
Examples of implementation of the present invention will be described below with reference to the drawings.
FIG. 1 is an external view of a dental handpiece (biaxial control bearingless motor / permanent magnet / straight type handpiece) according to 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 example is referred to as a micromotor handpiece.
In the figure, 1 is a micromotor handpiece, 2 is a front part of the handpiece, 3 is an attachment / detachment adapter, 4 is an O-ring, 5 is a motor clutch, 6 is a retaining ring, 7 is an attachment / detachment part, and 8a is a motor shaft side thrust. Permanent magnet for case side thrust, 9a for permanent magnet for motor shaft side radial, 9b for permanent magnet for case side radial, 10 for sleeve, 11 for water conduit, 12 for rotor, 13 for stator 14 is a motor case, 15 is a water joint, 16 is an air joint, 17 is an air passage, 18 is an electric signal pin, 19 is a lamp, 20 is a motor shaft , 27 is a stator, 28 is a gap, Reference numeral 29 denotes a plug portion, and 36 denotes a bearingless motor.
[0009]
As shown in FIG. 1, the micromotor handpiece 1 can be attached to and detached from the handpiece front part 2 and the motor case 14 housing the bearingless motor 36 at the place of the attaching / detaching part 7 and to the tooth at the time of treatment. Water injection, air blowing, etc. can be performed in the same manner as before.
The bearingless motor 36 is disposed at the central portion of the motor case 14, the motor shaft 20 is disposed at the center when viewed from the front and rear, and annular shaft-side radial permanent magnets 9 a are provided at both ends of the motor shaft 20. It is fixed orthogonally to.
On the outer periphery of the annular permanent magnet, the inner diameter of 9b of the annular case-side radial permanent magnet is opposed to a narrow gap. The magnets repel each other with the same polarity, and hold the entire upper, lower, left, and right circumferences of the motor shaft 20 in a non-contact manner during rotation and when stopped.
[0010]
An annular motor shaft side thrust permanent magnet 8a is disposed on each outer side of the radial permanent magnet 9a of the motor shaft 20, and an annular thrust fixed to the end of the attachment / detachment adapter 3 at a position facing it. The permanent magnet 8b and the annular thrust permanent magnet 8b disposed on the plug portion 29 are opposed to each other with a gap.
The magnets repel each other with the same polarity, and hold the thrust direction before and after the motor shaft 20 in a non-contact manner during rotation and when stopped. By the above, the rotor 12 is always held in a non-contact state.
[0011]
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 4 pole motor winding, 23 is a 2 pole position control winding, and 24 is Stator teeth, 25 is the direction from the far side to the near side, 26 is the direction from the near side to the far side, NU / NV / NW is one-fourth of three-phase four-pole, NUb / NVb NWb indicates a half of the three-phase two-pole, and φs indicates the rotation direction.
The stator armature winding 13 (FIG. 1): the 4-pole motor winding 22 and the 2-pole position control winding 23 (FIG. 2) are wired as shown in the figure.
The motor used for the tooth cutting instrument (micromotor handpiece 1) in the dental treatment shown in FIG. 1 and FIG. 2 integrates an inner rotor type motor and a magnetic bearing function into the motor body, and is independent. Bearingless motor that does not have a bearing mechanism
[0012]
FIG. 2 shows 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. The rotor 12 is embedded at right angles and symmetrically in all directions,
The N and S permanent magnets 21a and 21b shown in FIG. 2 are a long and wide plate-like integrated type. Instead, a large number of narrow and narrow plate-like permanent magnets are spaced slightly apart. It is good also as a structure which arrange | positions and embeds shallowly along the periphery, and does not put a permanent magnet in two places between each pole (not shown).
Further, the radial position control for the rotor 12 is performed by generating a force acting in the radial direction from the center of the rotor by making the rotating magnetic field unbalanced and generating a force acting in the radial direction from the center of the rotor. Windings 23),
In addition to the motor winding (four-pole motor winding 22) of the motor stator armature, another winding (two-pole position control winding 23) different from the number of poles of the motor is wound. The current flowing in this winding distorts the magnetic flux distribution in the air gap 28 between the stator 27 and the rotor 12 and generates a radial force in the rotor due to the distortion of the magnetic field distribution, thereby holding the rotor magnetically. A mechanism to
[0013]
The 4-pole motor winding 22 and the 2-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. A high-frequency current (for example, a carrier wave from a 20 kc oscillator) is superimposed on the wire, an induced voltage proportional to the rotor displacement is detected from the two-pole position control winding 23, and an estimated value of the radial displacement of the rotor 12 is used as feedback. Sensorless without using a radial position sensor of the motor shaft that realizes non-contact support of the main shaft using,
[0014]
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 rotor position detection Sensorless arithmetic circuit that receives the signal and outputs the drive timing (with detection function of rotation angle position of analog or digital electronic circuit),
Output transistor control circuit (circuit that drives the inverter circuit based on the detected rotation angle) and inverter circuit using an output transistor that supplies drive current to the motor (function to supply voltage or current synchronized with the rotation angle of the rotor) And a three-phase sensorless DC motor that does not require a rotational angle position sensor such as a Hall element.
The above is an outline of a bearingless motor combining various functions based on the above-mentioned documents.
[0015]
3 is a cross-sectional view taken along the line AA ′ of FIG. 1 in which a good conductor of a metal plate is provided on a permanent magnet provided on a rotor of a bearingless motor.
In the figure, reference numeral 25 denotes a metal plate.
As shown in the figure, the basic configuration is the same as that of FIG. 2 except that the outer periphery of the N-pole permanent magnet 21 a and the S-pole permanent magnet 21 b embedded in the rotor 12 is a metal plate 25 of a good conductor. Is arranged.
Further, instead of the metal plate, a mesh metal or a flat sheet in which a large number of coils are formed and arranged in a plane may be used. With this configuration, when the motor shaft is displaced, a current flows due to eddy current and a damping force is generated, so that the motor shaft is easily supported.
[0016]
Basically, the bearingless motor is a two-axis control that adds a function to generate torque to the radial position control magnetic bearing, but a two-axis control bearingless motor only controls the radial displacement. Since the tilt of the shaft cannot be controlled, the tilt of the shaft is suppressed by a permanent magnet that suppresses the radial displacement at both ends (FIG. 1). The tilt of the can also be controlled.
FIG. 4 is a longitudinal sectional view of a combination of a 4-axis control bearingless motor and a permanent magnet.
As shown in the drawing, the bearingless motor 36 is a four-axis control in which two 2-axis control motors shown in FIG. 1 are arranged in series and each is controlled. In addition to controlling, the tilt of the axis can be controlled.
Therefore, only the axial displacement needs to be suppressed during rotation by the permanent magnet 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 radial displacement.
[0017]
FIG. 5 is a longitudinal sectional view of a combination of a two-axis control bearingless motor and a stepped annular permanent magnet.
In the figure, 30a is a small outer diameter annular permanent magnet for a motor shaft, 31c is a large outer diameter annular permanent magnet, 30b is a small inner diameter annular permanent magnet for a stator, and 31d is a large inner diameter annular permanent magnet for a stator.
As shown in the figure, the end of the motor shaft 20 has an axial permanent magnet and an annular permanent magnet slightly different in the direction in which the diameter is increased by facing the same pole that suppresses the radial displacement. diameter annular permanent magnet 30a, the large outer diameter annular permanent magnets 31c, the small inner diameter annular permanent magnet 30b for the stator, a large inner diameter annular magnet 31d) by arranging a plurality stepped stators, the micromotor handpiece 1 It is housed in a housing to eliminate contact between the stator and the rotor when the motor is stopped and rotated.
[0018]
FIG. 6 is a longitudinal sectional view of a combination of a two-axis control bearingless motor and a truncated cone-shaped permanent magnet whose upper and lower surfaces are obliquely hollow.
In the figure, 32 is a truncated cone-shaped permanent magnet for a motor shaft, and 33 is a truncated cone-shaped permanent magnet for a stator.
As shown in the figure, a frustoconical permanent magnet having a hollow top and bottom surface (for a motor shaft) with the same pole that suppresses axial displacement and radial displacement obliquely facing each other at the end of the motor shaft 20. The frustoconical permanent magnet 32 and the frustoconical permanent magnet 33) are housed in the housing of the micromotor handpiece 1 to eliminate contact between the stator and the rotor when the motor is stopped and rotated. .
[0019]
FIG. 7 is a longitudinal sectional view of a combination of a 4-axis control bearingless motor, a permanent magnet, and a touchdown bearing.
In the figure, 34 is an annular touchdown bearing for a stator, and 35 is an annular touchdown bearing for a motor shaft.
As shown in the figure, the motor shaft side thrust permanent magnet 8a and the case side thrust permanent magnet 8b face each other at the ends of the motor shaft 20 and the case 14 as annular permanent magnets for suppressing axial displacement. Arranged. In addition, opposite ends of the stator 27 and the motor shaft 20 are opposed to an annular touch-down bearing (stator) having carbide and wear resistance that prevents the rotor 12 and the stator 27 from wearing when the motor is stopped. An annular touch-down bearing 34 for the motor and an annular touch-down bearing 35 for the motor shaft are disposed and housed in the housing of the motor handpiece 1.
[0020]
【The invention's effect】
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 tooth cutting in dental treatment, the motor used for the micromotor handpiece is
The stator is provided with a winding group for generating torque, and the winding group is provided with a winding group for generating a radial force or one winding group, and permanent magnets constituting magnetic poles are arranged inside the stator. with a rotating rotor which moves motion was carried out and radially, and more on the motor shaft within the housing that is configured to the stator periphery, the rotor is arranged, the motor shaft to the dental handpiece A function that generates torque and radial force by adjusting the current amplitude and phase of the winding group through interaction with the magnetomotive force generated by supplying current to the stator winding group with a connected structure And the radial force has the function of adjusting the radial rotor position or suppressing the vibration in the radial direction, and the torque has the function of adjusting the rotational speed of the rotor. If eccentric from the center of the It can be controlled around the child.
In addition, an annular permanent magnet facing the same pole that suppresses axial displacement and radial displacement is placed at the end of the motor shaft and housed in the housing of the micromotor handpiece, so that when the motor is stopped And at the time of rotation, the contact between the stator, the rotor and the end of the motor shaft can be eliminated.
2. According to the invention of claim 2,
A plurality of annular permanent magnets slightly different from each other in the direction in which the diameter is increased by facing the same poles that suppress axial displacement and radial displacement at the end of the motor shaft are arranged in a staircase pattern. Since it is housed in the housing of the handpiece, the contact between the stator and the rotor and the end of the motor shaft can be eliminated with a simple structure when the motor is stopped and rotated.
[0021]
3. According to the invention of claim 3,
Contained in the housing of the micromotor handpiece is a truncated cone-shaped permanent magnet with the upper and lower surfaces made hollow at the end of the motor shaft diagonally facing the same polarity to suppress axial displacement and radial displacement. With the orientation of one surface, contact between the stator and the rotor and the end of the motor shaft can be eliminated when the motor is stopped and rotated.
4. According to the invention of claim 4,
A high-frequency sine wave voltage or a high-frequency voltage generated by PWM is superimposed on the winding that generates the torque of the stator, and the self-inductance changes depending on the radial position of the rotor. Since it has a function of detecting the generated induced voltage and a function of estimating the position in the radial direction from the detected induced voltage, no radial position sensor is required.
5. According to the invention of claim 5,
A function for detecting the voltage generated in the stator winding, a circuit for integrating the voltage, and a function for detecting the integrated value of the voltage are provided, and the rotation angle position of the rotor is detected by an analog or digital electronic circuit. A function and a function of driving an inverter circuit based on the detected rotation angle, the inverter circuit having a function of supplying a voltage or a current synchronized with the rotation angle position of the rotor, and rotating a hall element or the like. No child rotation angle position sensor is required.
6. According to the invention of claim 6,
When a permanent magnet disposed on the rotor is provided with a metal plate or a net-like good conductor and the motor shaft is displaced, a damping force due to eddy current is generated, so that the displacement can be further suppressed.
[Brief description of the drawings]
FIG. 1 is an external view of a dental handpiece (biaxial control bearingless motor / permanent magnet / straight type handpiece) according to 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 ′.
3 is a cross-sectional view taken along the line AA ′ of FIG. 1 in which a good conductor of a metal plate is provided on a permanent magnet provided on a rotor of a bearingless motor.
FIG. 4 is a longitudinal sectional view of a combination of a 4-axis control bearingless motor and a permanent magnet.
FIG. 5 is a longitudinal sectional view of a combination of a two-axis control bearingless motor and a stepped annular permanent magnet.
FIG. 6 is a longitudinal sectional view of a combination of a two-axis control bearingless motor and a truncated cone permanent magnet whose upper and lower surfaces are obliquely hollow.
FIG. 7 is a longitudinal sectional view of a combination of a 4-axis control bearingless motor, a permanent magnet, and a touch-down bearing.
[Explanation of symbols]
1: Micromotor handpiece 2: Handpiece front part 3: Adapter for attachment / detachment 4: O-ring 5: Motor clutch 6: Retaining ring 7: Attachment / detachment part 8a: Permanent magnet for thrust on motor shaft side 8b: Permanent for case side thrust Magnet 9a: Radial permanent magnet for motor shaft side 9b: Permanent magnet for radial side of case 10: Sleeve 11: Water guide pipe 12: Rotor 13: Armature winding 14 of stator: Motor case 15: Water joint 16: Air joint 17: Air passage 18: Electric signal pin 19: Lamp 20: Motor shaft 21a: N-pole permanent magnet 21b embedded in the rotor: S-pole permanent magnet embedded in the rotor 22: 4-pole motor winding 23 : Bipolar position control winding 24: Stator teeth 25: Direction of communication from the far side to the front 26: Direction of communication from the near side to the far side 27: Fixed 28: Air gap 29: Plug portion 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 permanent magnet for stator 32: Motor shaft Frustum-shaped permanent magnet 33: frustum-shaped permanent magnet 34 for stator: annular touch-down bearing 35 for stator: annular touch-down bearing 36 for motor shaft: bearingless motor NU / NV / NW: three-phase four-pole 1/4 pole NUb / NVb / NWb: 1/2 pole of 3 phase 2 poles φs: Direction of rotation

Claims (6)

In a dental handpiece, comprising a coil group for generating a winding group and the radial force generates torque in the stator, the stator inside, silicon steel or solid which is a permanent magnet constituting a magnetic pole disposed and performs a rotational movement which is composed of a core or the like will comprise a rotary element that moves in a radial direction,
Moreover, it said the stator outer periphery housing is configured, also, the rotor is configured on a motor shaft within the housing, the motor shaft is provided with a structure formed by connecting the dental handpiece Become
By adjusting the current amplitude and phase of the winding group by the interaction between the magnetomotive force generated by supplying current to the stator winding group and the magnetic force of the permanent magnet of the rotor , torque and radial force are adjusted. The radial force has a function of adjusting the rotor position in the radial direction or suppressing radial vibration, and the torque has a function of adjusting the rotational speed of the rotor. Do Ri,
Further, an annular permanent magnet facing the same pole that suppresses axial displacement and radial displacement is arranged at the end of the motor shaft, and is housed in the housing.
A dental handpiece characterized in that contact between the stator and the rotor and the end of the motor shaft is eliminated when the motor is stopped and rotated . In the dental handpiece according to claim 1, instead of an annular permanent magnet facing the same pole that suppresses axial displacement and radial displacement at the end of the motor shaft,
A plurality of annular permanent magnets that are slightly different from each other in a direction in which the diameter is increased by facing the same pole that suppresses axial displacement and radial displacement at the end of the motor shaft are arranged in a step shape. dental handpiece said. In the dental handpiece according to claim 1, instead of an annular permanent magnet facing the same pole that suppresses axial displacement and radial displacement at the end of the motor shaft,
A frustoconical permanent magnet with the upper and lower surfaces made hollow, with the same polarity to suppress axial displacement and radial displacement obliquely facing each other at the end of the motor shaft, is housed in the housing of the micromotor handpiece. dental handpiece characterized in that it comprises Te. By superimposing a high-frequency sine wave voltage or a high-frequency voltage generated by PWM on the winding that generates the torque of the stator, the self-inductance or the mutual inductance changes depending on the radial position of the rotor, 4. A function of detecting an induced voltage generated at a winding terminal and a function of estimating a radial position from the detected induced voltage, wherein a radial position sensor is not required. A dental handpiece according to claim 1. A function for detecting the voltage generated in the stator winding, a circuit for integrating the voltage, and a function for detecting the integrated value of the voltage are provided, and the rotation angle position of the rotor is detected by an analog or digital electronic circuit. A function and a function of driving an inverter circuit based on the detected rotation angle, the inverter circuit having a function of supplying a voltage or a current synchronized with the rotation angle position of the rotor, and rotating a Hall element or the like The dental handpiece according to any one of claims 1 to 4, wherein a child rotation angle position sensor is not required . 6. A permanent magnet disposed on the rotor is provided with a metal plate or a net-like good conductor, and a damping force due to eddy current is generated when the motor shaft is displaced. Dental handpiece as described.

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