JP2001346395A - Brushless motor and rotation controller for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation controller for a brushless motor which causes currents to flow into a plurality of sensors only by connecting two signal conductors, and takes position signals out in order, in spite of its simple structure. SOLUTION: A position detector 18 is formed by combining an impedance converting circuit portion 11 composed by connecting a plurality of Hall elements fitted to a stator and connected in parallel with one another, in series to a reference impedance element, and bypass-connecting selective impedance elements which have different values respectively and are disconnected or connected by on/off operation of Hall elements by the magnetic fields of the rotor, to respective Hall elements, a voltage discriminating circuit portion 12 for discriminating output voltages of the converting portion 11, and a logical sum circuit portion 13 which finds the logical sum of the output voltages from the discriminating portion 12 and outputs a position signal of the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small brushless motor rotation control device and a brushless motor used in medicine or dentistry.

[0002]

2. Description of the Related Art A brushless motor provided with an electronic commutation mechanism, which removes mechanical contact parts such as a brush and a commutator from a DC motor, has recently been used in medicine or dentistry. Widely used for small cutting tools.

Generally, in this type of brushless motor,
The rotor composed of permanent magnets is rotated by energizing coils of a plurality of phases wound on the stator to form a rotating magnetic field, but the Hall element is used to detect the rotational position of the rotor. There are used a plurality of position sensors composed of a plurality of position sensors.

In general, such a position sensor is mounted on the same circuit board in terms of circuit configuration, or is generally configured as one block, but each of the sensors has a signal output terminal. Therefore, signal output terminals according to the number of sensors are derived in addition to the energizing terminals and the common terminals.

[0005] Therefore, signal lines corresponding to the number of these terminals are required. When the number of position sensors increases, the number of signal lines also increases, complicating the wiring, and operability, operability, and reliability during assembly. It is a factor that lowers.

FIG. 10 shows three position detection sensors S # 1-S # 1.
S # 3 is shown in one block.
Energizing terminal Tv, common terminal Tc provided for each sensor
Are connected in common, but since the signal output terminals T1 to T3 of the respective sensors are derived as they are, in addition to the energizing line and the common line, three signals according to the number of the sensors are provided. When signal lines are required and other signal processing units are connected, five signal lines are required, and three signal input ports are required for processing sensor signals.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the conventional sensor circuit section provided with a plurality of sensors increases the number of signal lines as the number of sensors increases as described above. It was made in view of the fact that
An object of the present invention is to provide a brushless motor rotation control device and a brushless motor, which have a simple structure, can supply current to a plurality of sensors simply by connecting two signal lines, and can sequentially extract position signals. I do.

[0008]

According to a first aspect of the present invention, there is provided a brushless motor rotation control device comprising: a rotor having a coil for applying a voltage for generating a rotating magnetic field; a stator for applying a voltage; A position detection circuit including a plurality of Hall elements disposed corresponding to each phase of the stator, wherein the position detection circuit turns on each of the Hall elements. By action
An impedance converter having a configuration in which selective impedance elements having different values additionally connected in parallel to each other are selectively connected to a reference impedance element in accordance with the on / off operation of the Hall element, thereby varying the combined impedance. A circuit unit, and a plurality of thresholds are set to identify an operation pattern of a combination of off and on of the plurality of Hall elements, and a voltage discrimination circuit unit for discriminating an output voltage of the impedance conversion circuit unit. An OR operation for calculating an OR operation of the output voltages from the voltage discriminating circuit unit in order to detect an OFF operation and an ON operation of the plurality of Hall elements in synchronization with a phase sequence change of a phase voltage applied to the stator. It is characterized by being configured in combination with a circuit unit.

In the impedance conversion circuit section provided in the position detection circuit which is a feature of this rotation control device, a plurality of Hall elements corresponding to each phase are arranged in parallel on a stator.
A signal that detects the operation pattern of the combination of OFF and ON of the stator, which changes with the rotation of the rotor, is transmitted to the voltage discriminating circuit via two signal lines, so connection is added when the Hall element is turned on. The impedance values of the selected impedance elements to be used are made different.

[0010] The voltage discriminating circuit section is provided with a plurality of threshold values for detecting a change in voltage level that changes in accordance with an operation pattern of a combination of off and on of the Hall element.

The Hall element constitutes, for example, a Hall switch as a switching element. In the case where the stator is constituted by a three-phase coil, six types of off-states are provided for each magnetic pole pair.
There is an operation pattern of a combination of ON.

The output voltage determined by the voltage determination circuit section only identifies the operation pattern of the combination of off and on of the Hall element, and determines which of the plurality of Hall elements is on and which is off. Can not. Therefore, the voltage output of the voltage discriminating circuit alone cannot be used for controlling the rotation of the motor.

Therefore, an OR circuit is provided to calculate the OR of the voltage output of the voltage discriminating circuit to turn off the Hall element,
It is configured to detect the ON operation. Therefore, in the OR circuit section, of the output voltage from the voltage discriminating circuit section, the arrangement position according to the electrical angle of the Hall element on the stator set in advance and the phase sequence change of the applied voltage applied to the stator are changed. In consideration of the above, an output voltage to be ORed is set to obtain a position detection voltage, that is, a position signal.

The position signal obtained by the position detection circuit is sent to the coil drive circuit together with the signal of the phase voltage applied to the stator, and the rotation of the motor is controlled.

Thus, according to this rotation control device, it is only necessary to mount the Hall element and the selective impedance element on the energized circuit board of the stator of the brushless motor.
The structure is simplified, and the size of the brushless motor can be further reduced. In addition, the impedance conversion circuit unit, that is, two signal lines derived from the stator can be used.

According to a second aspect of the present invention, there is provided a rotation control device for a brushless motor according to the first aspect, wherein the voltage discriminating circuit is a combination of a predetermined off-state and an on-state of a Hall element. And a threshold value for discriminating between a short circuit and a disconnection.

In this rotation control device, the voltage discriminating circuit section is constituted by a multi-level window comparator in which a plurality of threshold values are set, and there are six types of off-on operation patterns by three Hall elements. In such a case, a total of eight operation patterns can be detected by adding a short-circuit and a disconnection pattern thereto.

According to a third aspect of the present invention, there is provided a rotation control device for a brushless motor according to any one of the first to second aspects, wherein the stator has an energized circuit board. The circuit board is characterized in that the selective impedance element and the Hall switch having the built-in Hall element are pinned and mounted on a circuit board.

In this rotation control device, in the stator, each of the selection impedance element and the hole switch having a built-in Hall element causes connection pins derived therefrom to protrude from a hole formed in the energized circuit board. Since the structure is mounted by soldering, there is little occurrence of defects during coil molding or autoclave.

According to a fourth aspect of the present invention, in the rotation control apparatus for a brushless motor according to any one of the first to third aspects, the reference impedance element and the selection impedance element are resistors. When the stator has three phases, the ratio of the different resistance values of the selected impedance element is set to 1: 1.6 to 2.
2: 4 to 5.

Since the rotation control device clarifies the appropriate ratio of different resistance values by experimental values, a rotation control device exhibiting the effects of the present invention can be easily manufactured.

According to a fifth aspect of the present invention, there is provided a rotation control device for a brushless motor according to any one of the first to fourth aspects, wherein the voltage discriminating circuit unit and the OR circuit unit are microcomputers. It is characterized by comprising.

Therefore, the control device can be made compact.

A brushless motor according to a sixth aspect of the present invention is a brushless motor whose rotation is controlled by the brushless motor rotation control device according to any one of the first to fifth aspects, wherein the plurality of brushless motors are provided inside the brushless motor. Characterized in that the Hall element and the selective impedance element described above are mounted.

In the case where the rotation control device of the present invention is used, if a plurality of Hall elements and selective impedance elements are provided on the stator, the structure of the stator of the brushless motor is simplified, and signals from the stator are also provided. The number of wires can also be two, but this brushless motor exerts its effect.

However, the plurality of Hall elements and the selective impedance element may be provided not only in the stator but also in the inside of the brushless motor. In such a case, the number of necessary parts is small, The structure of the motor is simplified.

A brushless motor according to a seventh aspect is a brushless motor whose rotation is controlled by the brushless motor rotation control device according to any one of the first to fifth aspects, wherein a tube for connecting the brushless motor is provided. The plurality of Hall elements and the selective impedance element are mounted on the inside of a connection part or on the inside of an adapter provided between the brushless motor and the tube connection part. I do.

The plurality of Hall elements and the selective impedance element described above are not limited to the inside of the brushless motor, but can also be provided at the tube connection near the motor. In such a case, the number of necessary parts is small. The structure of the tube connection is simplified.

Further, the adapter can be provided inside an adapter provided between the brushless motor and the tube connecting portion. In this case, the structure of the adapter can be simplified and the conventional brushless motor can be provided. Even in the case of a motor, by adding this adapter, a plurality of Hall elements of the present invention and the above-described selective impedance element can be added, and the rotation control device of the present invention can be applied.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram conceptually showing a basic configuration of a rotation control device for a brushless motor according to the present invention.

The rotation control device 20 is composed of a rotor and a stator (to be described later). The brushless motor 10 constituting the impedance conversion circuit section 11 in terms of control, and two signal lines from the brushless motor 10 2fa, receives a voltage signal and detects a change in the voltage level. A voltage discriminating circuit unit 12 receives a discriminating signal from the voltage discriminating circuit unit 12, and calculates a logical position signal of a rotor of the brushless motor 10. The circuit unit 13 and the OR circuit unit 1
3, a coil drive circuit unit 15 that drives a coil provided on a stator of the brushless motor 10 in response to a position signal
It has.

In the case where the stator of the brushless motor 10 is configured as a three-phase coil, the stator is provided with three coils in this embodiment, and three driving coils for sending a driving current to the three coils are provided. The line 2fb connects the brushless motor 10 and the coil drive circuit unit 15.

The rotation control device 20 has a plurality of Hall elements, that is, a position sensor of the rotor, provided on the stator of the brushless motor 10 as will be described in detail later. The signals from the two signal lines 2fa are processed by the voltage discriminating circuit unit 12 and the OR circuit unit 13 to obtain a rotor position signal.
As a result, the three drive lines 2f
By b, a drive current is sent to the coil of the stator, and the rotation of the brushless motor 10 is controlled.

That is, irrespective of the number of phases of the stator, only two signal lines 2fa are required, and the number of drive lines 2fb is the number corresponding to the number of phases. In the case of three phases, the brushless motor 10, ie, the stator Requires only five input / output lines.

The above-described impedance conversion circuit 1
1. The voltage discriminating circuit section 12 and the OR circuit section 13 are integrated as a position detecting circuit 18, and the voltage discriminating circuit section 12
Since the and OR circuit unit 13 can be constituted by the microcomputer 19, the control device can be made compact.

FIG. 2 is a block diagram showing a schematic configuration of a main part of a rotation control device of a brushless motor according to the present invention in which a position detection circuit is incorporated. The same parts as those already described are denoted by the same reference numerals, and redundant description will be omitted.

The position detection circuit 18 includes an impedance conversion circuit section 11, a voltage discrimination circuit section 12, and an OR circuit section 13.
It is comprised including.

Here, the impedance conversion circuit 11
Corresponds to three Hall switches Hu, Hv, and Hw, and three resistance elements Ru, Rv, and Rw having different resistance values provided as selective impedance elements are turned on / off operations of the corresponding Hall elements. And by connecting and disconnecting in parallel with each other, the selective impedance element R
u, Rv, and Rw are configured to vary the parallel combined resistance, whereby the level V of the voltage signal input from the impedance conversion circuit unit 11 to the voltage determination circuit unit 12 is adjusted.
h (which is a voltage shared by the parallel circuit of the selection impedance of the circuit constituted by the reference impedance element and the parallel synthesis circuit of the selection impedance element) is changed in accordance with the combination pattern of turning on and off the Hall element.

It is to be noted that, in practice, instead of turning on and off the Hall element, a switch element formed of a transistor built in the Hall switch is turned on and off in response to the output of the Hall element. .

In FIG. 2, it is assumed that the rotor is rotated by applying a three-phase rotating magnetic field to the stator. Since three Hall elements are arranged on the stator in accordance with the electrical angle, ,
The three Hall switches Hu, Hv, and Hw cannot take two combination patterns in which all are turned on or all are turned off.
As shown in (b), the combination pattern changes to six types.

The voltage discriminating circuit section 12 constitutes a multi-level window comparator in which ten comparators CP1 to CP10 are connected in parallel, and a reference input terminal of each of the comparators CP1 to CP10 has another constant voltage power supply. , Five reference voltages Vh1 defined by a voltage dividing circuit configured by connecting nine resistors R1 to R9 in series.
To Vh5 (Vh1 to Vh5 are sequentially set to larger values as shown in FIG. 4), and the other signal input terminals are connected in common. Is input.

Also, ten comparators CP1 to CP
An output terminal 10 is input to an OR circuit unit 13 to be described later to turn on three Hall switches Hu, Hv, and Hw.
The off signal is ORed in accordance with a phase sequence change of the phase voltage applied to the stator.

That is, the OR circuit section 13 has three Os
R gates OR1 to OR3 are combined, and each of the gates OR1 to OR3 performs on / off operations of three Hall switches Hu, Hv, and Hw based on a phase sequence change of a phase voltage applied to the stator. Demodulation is performed according to the operation.

In this case, the combination pattern to be ORed is composed of three Hall switches Hu, Hv,
Hw is specified by focusing on or off operation. For example, when focusing on off operation, for the Hall switch Hu, the logical OR of the outputs of the voltage discriminating circuit unit 12 detecting the patterns 1, 2 and 6 is obtained. For the Hall switch Hv, the output of the voltage discriminating circuit unit 12 detecting the patterns 4, 5, and 6 is ORed, and for the Hall switch Hw, the voltage discriminating circuit unit 12 detects the patterns 2, 3, and 4. OR of the output is calculated, and three Hall switches H
The on / off operation of the hall element built in u, Hv, Hw is demodulated.

The output to be ORed by the OR circuit unit 13 varies depending on the structure of the brushless motor, that is, the number of magnetic poles of the rotor and the phase pattern of the voltage applied to apply a rotating magnetic field to the stator. It goes without saying that the configuration of the logical sum circuit unit is changed according to the circuit configurations of the impedance conversion circuit unit and the voltage determination circuit unit.

Reference numeral 14 denotes a disconnection short-circuit detecting circuit.
Reference voltages Vh0, Vh6 (where Vh0 <Vh1, V
h6> Vh5) with two different comparators CP1
0 and CP11 are connected in parallel, the voltage signal Vh from the impedance conversion circuit unit 11 is determined, and disconnection and short circuit of the impedance circuit unit 11 including the Hall switches Hu, Hv and Hw are detected.

The brushless motor 10 is configured as a three-phase motor.
u, Cv, and Cw are provided.

The output voltage determined by the voltage determining circuit unit only identifies the operation pattern of the combination of the off and on of the Hall switches Hu, Hv and Hw, and turns on which of the plurality of Hall elements is on and which is off. Cannot be determined. Therefore, the voltage output Vh of the voltage determination circuit unit 12 alone cannot be used for the rotation control of the motor.

Therefore, a configuration is provided in which an OR circuit section 13 is provided to obtain a logical sum of the output voltages Vh of the voltage discriminating circuit sections 12 to detect the OFF and ON operations of the Hall switches Hu, Hv and Hw. For this reason, in the OR circuit unit 13, among the output voltages Vh from the voltage discriminating circuit unit 12, the arrangement positions of the Hall switches Hu, Hv, and Hw set in advance according to the electrical angle on the stator 2 are determined. The position signal is obtained by setting the output voltage Vh to be ORed in consideration of the phase sequence change of the applied voltage applied to the element.

The position signal obtained by the position detection circuit 18 is sent to the coil drive circuit section 15 to control the rotation of the motor.

Thus, according to the rotation control device 20, the stator 2 of the brushless motor 10 need only be provided with the selection impedance elements Ru, Rv, and Rw in addition to the Hall switches Hu, Hv, and Hw. The brushless motor can be simplified, and the size of the brushless motor can be further reduced. Further, it is possible to use only two signal lines derived from the impedance conversion circuit unit 11, that is, the stator 2.

In FIG. 2, I (I1 to I6)
Is the sum of the selection currents Iru, Irv, Irw that flow when the Hall elements incorporated in the three Hall switches Hu, Hv, Hw are turned on according to the rotation position of the stator, in which the selection impedance elements Ru, Rv, Rw are turned on. When a rotating magnetic field is formed by a stator to which a three-phase AC voltage is applied to a two-pole rotor, as described above, the operation of turning on and off the Hall switches Hu, Hv, and Hw is performed as described above. Six values (I1 to I6) are taken in accordance with the pattern.

Here, Vo is the reference impedance element R
0, and Vh is a Hall switch Hu, H
The shared voltage of the parallel combination circuit of the selected impedance elements selectively connected in parallel by v and Hw (the voltage output from the impedance conversion circuit section 11 to the voltage determination circuit section 12) and Vc are transmitted to the impedance conversion circuit section. Assuming a combined voltage to be applied, these output currents I (I1 to I
6) There is the following relationship among the shared voltage Vo, the shared voltage Vh, and the composite voltage Vc. Vo = I (I1 ~ I6) * Ro Vh = Vc-Vo I1 = Rv * Rw * (2 * Ion + Ioff + Irv + Irw) / (Rv * Rw + Ro *
(Rv + Rw)) I2 = Rv * (2 * Ion + Ioff + Irv) / (Ro + Rv) I3 = Ru * Rv * (2 * Ion + Ioff + Iru + Irv) / {Ru * Rv + Ro
* (Ru + Rv)) I4 = Rv * (2 * Ion + Ioff + Iru) / (Ro + Ru) I5 = Ru * Rw * (2 * Ion + Ioff + Iru + Irw) / {Ru * Rw + Ro
* (Ru + Rw)} I6 = Rw * (2 * Ion + Ioff + Irw) / (Ro + Rw) Iru = (Vc-Vo) / Ru Irv = (Vc-Vo) / Rv Irw = (Vc-Vo Here, “*” indicates multiplication and “/” indicates division.

Here, Ion and Ioff are current consumptions of the Hall switches Hu, Hv and Hw. As can be understood from the above equation, the currents Ion and Ioff do not depend on the shared voltage Vh, and It is desirable that the current is smaller than the currents Iru, Irv, Irw of the selected impedance element.

FIG. 3A shows a design example of each component of the impedance conversion circuit section, and FIG. 3B shows a three-phase AC voltage applied to a two-pole rotor designed based on the design values. Output current flowing through the impedance conversion circuit unit applied when a rotating magnetic field is formed by the stator to which
It is a figure which shows the six ON / OFF combination operation | movement pattern shown corresponding to the ON / OFF operation | movement of three Hall switches Hu, Hv, Hw.

FIG. 4A is a diagram showing the operation of identifying the ON / OFF operation pattern of the Hall element by the voltage discriminating circuit. In this figure, the output of the impedance conversion circuit is not a voltage but a current. Shown as a change.
Vh1 to Vh5 indicate threshold values for determining six operation patterns of the Hall element, Vh0 indicates a short circuit, and Vh6 indicates a threshold value for determining a disconnection. , (B)
Is a pattern identification signal output by the voltage discriminating circuit, and (c) is a demodulated output voltage of the three Hall switches Hu, Hv, Hw demodulated by the OR circuit.

The OR circuit section 13 performs an OR operation on the output voltage of the voltage discriminating circuit section 12 according to the following equation,
As a result, an output voltage as shown in FIG. 4C is output as a position signal.

Hu = V (16) + V (14) + V (1
5) Hv = V (15) + V (11) + V (1
3) Hu = V (13) + V (12) + V (1
6) FIG. 5 is a diagram for explaining the relationship between the off / on operation of the Hall element incorporated in the Hall switch of the present invention and the change in the position between the rotor and the stator. As shown, as the element rotates in the counterclockwise direction, the on / off state of the Hall element changes, resulting in a combination pattern as shown in FIG.

According to the present invention, such ON / OFF operation patterns of the Hall elements are determined by selecting impedance elements Ru, Rv, Rw provided corresponding to the respective Hall elements.
Are additionally connected in parallel due to the ON operation of the Hall element, and the change in the parallel combined resistance value is indicated by the output voltage Vh.
And further processing of a voltage discriminating circuit section and a logical sum circuit section is added to turn on each Hall element,
The off state is demodulated in accordance with the phase sequence change of the phase voltage applied to the stator, and the demodulated on / off signal is used to detect the position of the rotor with respect to the stator to control the rotation of the brushless motor. We are using.

According to the present invention, the different resistance values of the selective impedance elements Ru, Rv, and Rw are different from the values of the parallel combined resistance values obtained when the Hall element is turned on. It is desirable to be as far away as possible.

According to the experimental results of the present inventors, it has been confirmed that setting the ratio of the resistance values to 1: 1.6 to 2.2: 4 to 5 can be used sufficiently. .

FIG. 6 is a diagram for explaining the structure of a pin-mounted stator energizing circuit.

As can be seen from this figure, in this rotation control device, the stator 2 has a selective impedance element R
It is sufficient to mount only the u, Rv, and Rw and the Hall switches Hu, Hv, and Hw each having a built-in Hall element, and the structure is very simple.

Further, since these need only be mounted on the current-carrying circuit board 2d, the selective impedance elements Ru, Rv, Rw and the Hall switch H can be mounted without surface mounting.
Since the connection pins derived from u, Hv, and Hw are made to protrude from the holes formed in the current-carrying circuit board 2d and are mounted by soldering, there is little occurrence of defects during coil molding or autoclave.

As shown in FIG. 6, the current-carrying circuit board 2d of the stator 2 is provided with selective impedance elements Ru, Rv, Rw and Hall switches Hu, Hv, Hw.
Only two terminals 2f, which are two signal terminals 2fa serving as signal lines and three terminals 2fb serving as drive lines for three-phase coils, are led out.

The symbol “2b” added to the parentheses “()” of each of the Hall switches Hu, Hv, and Hw is obtained by grasping the Hall switches Hu, Hv, and Hw as hardware components. Sign.

FIG. 7 is a partially broken external perspective view showing an example of the stator of the present invention.

The stator 2 is formed as a three-phase, three-turn coil 2a for generating the rotating force of the brushless motor 10, ie, a rotating magnetic field, a Hall switch 2b for detecting the magnetic field of the rotor 1, A bobbin 2c constituting an inner peripheral portion of the child 2 and a rear end (right side in the figure) of the bobbin 2c
The stator 2 is provided with a current-carrying circuit board 2d which is provided in a disk shape in a direction perpendicular to the longitudinal axis direction, that is, in the outer circumferential direction, and has terminals 2f extended therefrom. These coils 2a, Hall switches 2b, bobbins 2c, The energized circuit board 2d and the like
Is characterized by being integrally coated with a resin.

The bobbin 2c is a right cylinder, and its inner diameter is set so that there is a gap with respect to the outer diameter of the rotor 1 to such an extent that the rotation of the rotor 1 is not hindered.
A coil 2a for generating a rotating magnetic field for the permanent magnet of the rotor 1 is surrounded by a substrate 2d provided at the rear end.

The coil 2a is formed along the outer periphery of the bobbin 2c by a press coil forming method. In this example, the coil 2a thus formed is
The outer periphery of the bobbin 2c is surrounded by three turns so as to be divided into three, but this is a three-phase brushless motor, and is not limited to three.

This press coil making method is to wind a self-fused electric wire composed of a good electric conductor such as copper with a bobbin-less winding machine, and simultaneously apply hot air to fuse the electric wires together. A coil wound and set in a mold is set, and an electric wire is flowed through the coil to generate heat and soften, and then pressed to form a coil having a predetermined shape. A feature is that a spring is provided, and the pressure of the spring is adjusted so as not to apply the pressing pressure at once during pressing.

By doing so, a coil having a desired shape, in particular, a coil having a small thickness in the radial direction and uniformly surrounding the rotor can be obtained without leaving any residual stress on the electric wire of the formed coil. Can be formed, and a coil suitable for a brushless motor coil whose outer diameter is desired to be reduced can be obtained.

The hole switch 2b itself has heat resistance, but in combination with the integral resin coating, the heat resistance is further improved, and the autoclave sterilization resistance of the entire brushless motor is further improved. In addition, the Hall element detects the rotation of the rotor at the point where the magnetic flux reverses, so it is susceptible to changes in the magnetic flux. Therefore, the function of the Hall element is sufficiently exhibited.

FIG. 8 is an exploded perspective view showing an example of the brushless motor of the present invention.

The brushless motor 10 has a rotor shaft 1
b, a rotor 1 having a permanent magnet 1a and bearings 1c, 1f on both sides thereof, and an outer case 4 for rotatably supporting the rotor 1 and accommodating the entire brushless motor 10.
And a core unit 3 housed in the outer case 4 and containing a core (not shown) made of a magnetic material, and a stator 2 housed in the core unit 3 and provided with a coil.
And a rear bracket 5 to be fitted behind the stator 2 and the outer case 4 (to the right in the drawing), and an intermediate bracket 6 for connecting the rear bracket 5 to a connecting portion between the rear bracket 5 and the main body. I have.

The permanent magnet 1a of the rotor 1 has a rotor shaft 1b
And the outer periphery is covered. Out of the bearings 1c and 1f provided on both sides of the permanent magnet 1a, the outer diameter of the bearing 1c on the left side in the drawing, that is, the front side is larger than the outer diameter of the bearing 1f on the rear side. The outer diameter of the bearing 1c is larger than the outer diameter of the permanent magnet 1a.

The bearing 1c is fitted in a bearing hole 4a in front of the outer case 4, the permanent magnet 1a is housed inside the stator 2, and the bearing 1f is mounted in the bearing hole 5 of the rear bracket 5.
a, the bearing holes 4 of these outer cases 4
a, the inner diameter of the bearing hole 5a of the stator 2 and the rear bracket 5,
It corresponds to each opponent.

Therefore, in a state where the core unit 3, the stator 2, the rear bracket 5 and the like are assembled to the outer case 4, the rotor 1 can be assembled and removed from the front with the bearing bodies 1c and 1f attached. Therefore, it is easy to assemble and disassemble. In particular, the bearings 1c and 1f of the rotor 1 that are worn out by use and need to be replaced are large, and the rotor 1 is brushlessly assembled without disassembling other parts while the rotor 1 is assembled. If it can be removed from the motor 10, it is very convenient for repair and replacement.

At the tip of the rotor shaft 1b of the rotor 1, there is provided a joint 1i for transmitting a rotational force to a treatment instrument, for example, a shank portion of a handpiece. The inner diameter of the bearing 1c on the joint 1i side is provided. Is larger than the outer diameter of the joint 1i. Therefore, as described above, after replacing the bearing 1c on the joint 1i after extracting the rotor shaft 1b with the bearings 1c and 1f assembled, the old bearing 1c is removed without removing the joint 1i. In addition, a new bearing 1c can be attached, and the bearing can be easily replaced or replaced.

Balancers 1j and 1k are provided between the permanent magnet 1a of the rotor shaft 1b and bearings 1c and 1f provided so as to sandwich the permanent magnet 1a. This balancer 1j, 1
k is made of a metal which can be easily cut, for example, brass or the like, is fixed to the rotor shaft 1b, and a part thereof is appropriately cut and removed so that the dynamic balance of the entire rotor 1 can be maintained. Has become. When the dynamic balance is set to be appropriate in this way, even if the rotor 1 rotates at a high speed, no blurring due to imbalance occurs, and the rotor 1 is suitable as a rotation driving means of the treatment instrument.

The stator 2 is characterized by being integrally coated with a resin, including the coil. In FIG. 1, only the integrally molded resin 2e is visible in appearance. This integral resin coating is performed using a predetermined jig or the like so that the axes of the inner and outer diameters coincide with each other separately from the entire assembly of the brushless motor 10. Terminals 2f protrude from the rear of the stator 2, and when the rear bracket 5 is incorporated into the stator 2, these terminals 2f protrude further rearward from the rear bracket 5 so that electrical connection can be made. It has become.

The core unit 3 serves as an iron core for strengthening the magnetic field of the coil of the stator 2. The core unit 3 is configured to cover the outer periphery and both side surfaces of a core (not shown) in which a plurality of ring-shaped silicon steel sheets are laminated. It is restrained by the core case 3h. The two conduits 3c visible on the outer periphery of the core unit 3 supply water and air necessary for dental treatment from the main body side (the right side in the figure) to the tip side (the left side in the figure, that is, the rotary tool side). The core case 3h is fitted into a cut groove 3b provided through the outer periphery of the core case 3h in the axial direction, and the outer side is restrained and fixed to the inner periphery of the outer case 4.

In this example, the cut grooves 3b are provided at four places on the outer periphery of the core case 3h, and the electric conduits (not shown) are similarly fitted into the remaining two grooves 3b. It has become. Thus, the core unit 3
It is possible to supply necessary fluids and the like without providing an extra space between the outer case 4 and the outer case 4. As a means, this brushless motor 10 is suitable.

Since the core unit 3 and the stator 2 are detachable as shown in the figure, only one of the core unit 3 and the stator 2 can be replaced as compared with an integrated unit, and repair can be performed. This simplifies the process and reduces the repair cost.

As described above, the outer case 4 is provided with a bearing hole 4a for receiving the bearing body 1c in front of the rotor 1 at the front, which is not visible in the drawing but is open at the rear. Further, a through hole 4b is provided on the periphery of the front bearing hole 4a. When the core unit 3 is housed in the outer case 4, the conduit 3c and the like can be seen through the through hole 4b. I have.

As described above, the rear bracket 5 is covered with the bearing hole 5a for receiving the bearing body 1f after the rotor 1 and the core unit 3 and the stator 2 are assembled to the outer case 4 as described above. In this case, the hole 5b for projecting the terminal 2f of the stator 2 to the rear and the conduit 3c fitted in the cut groove 3b of the core unit 3 and the like similarly to the hole 4b of the outer case 4 project. A hole 5c is provided.

The outer diameter of the intermediate bracket 6 is formed with two types of male screws having different pitches. Among them, the male screw 6a on the left side of the figure, that is, the front side of the brushless motor 10
Is engaged with the outer case 4, and the core unit 3, the stator 2,
It functions to fix the rear bracket 5 and the like inside the outer case 4. The male screw 6b on the rear side of the brushless motor 10
The motor 10 is used for connection to a flexible tube (not shown) for supplying electricity, water, air, and the like to the motor 10.

In the brushless motor 10, the rotor 1 is inserted from the front of the outer case 4 (left side in the figure) as shown in the figure, while the conduit 3c and the like are fitted from the rear of the outer case 4. The assembly is completed only by sequentially inserting the core unit 3, the stator 2 integrally coated with resin, and the rear bracket 5, and the centering of the rotor 1 and the stator 2 is not required, and the assembly of the entire brushless motor is simplified. .

Further, since the entire stator 2 is integrally covered with the resin and the coil and the like are not exposed on the outer periphery of the stator 2, the coil is not damaged when the stator 2 is fitted inside the core unit 3. Further, as a secondary effect, the heat insulating property of the coating resin improves the heat resistance of the stator, which has been a weak point in heat resistance, and also improves the heat resistance of the entire brushless motor.

FIG. 9 is a fragmentary front view showing another example of the brushless motor of the present invention.

This figure shows a state in which the handpiece A is mounted on the handpiece body B in which the brushless motor 10 is incorporated.

The handpiece body B is connected to a brushless motor 10 and a flexible tube C for supplying electricity, water, air, etc. to the motor 10 in a detachable manner. Part 7,
The tool connecting portion 7 includes a one-touch engaging means 7a which allows the handpiece A to be attached and detached with one touch.

FIGS. 6 and 7 show selective impedance elements Ru and R, which are important components of the rotation control device of the present invention.
v, Rw and Hall switch H with a built-in Hall element
Although an example in which u, Hv, and Hw are provided on the stator has been described, the Hall switch incorporating the selective impedance element and the Hall element is not limited to the stator, and the brushless motor 1
The brushless motor 10 can be provided at a suitable portion inside the motor 0, and also in this case, the structure of the brushless motor 10 is simplified because few parts are required.

In this case, the motor can be mounted on the brushless motor 10 by integral molding without using aerial wiring or using a current-carrying circuit board of the stator.

The Hall switch and the selective impedance element are not limited to the inside of the brushless motor, but may be provided at a tube connecting portion Ba provided at the end of the tube C which is detachable from the motor in the vicinity thereof. Yes, in that case also, the number of necessary parts is small, so that the structure of the tube connection is simplified.

Further, they can be provided inside a detachable adapter (not shown) provided between the brushless motor 10 and the tube connecting portion Ba. In this case, this adapter is used. In addition to simplifying the structure of-, even with a conventional brushless motor, it is possible to add a plurality of Hall elements and selective impedance elements of the present invention by adding this adapter. Will be able to apply.

[0098]

According to the brushless motor rotation control device of the present invention, the stator of the brushless motor includes:
It is only necessary to provide a selective impedance element other than the Hall element, so that the structure is simplified and the size of the brushless motor can be further reduced. In addition, the impedance conversion circuit unit, that is, two signal lines derived from the stator can be used.

According to the rotation control device for a brushless motor according to the second aspect, in addition to the effect of the first aspect, the voltage discrimination circuit section is constituted by a multi-level window comparator in which a plurality of threshold values are set. When there are six types of operation patterns of a combination of off and on with one Hall element, a total of eight operation patterns can be detected by adding short-circuit and disconnection patterns.

According to the rotation control device for a brushless motor according to the third aspect, in addition to the effect of any one of the first and second aspects, in the stator, a selection impedance element and a Hall switch having a built-in Hall element are provided. In each case, the connection pins derived from each are formed so as to protrude from holes formed in the current-carrying circuit board and are mounted by soldering, so that there is little occurrence of defects during coil molding or autoclave.

According to the rotation control device for a brushless motor of the fourth aspect, in addition to the effects of any one of the first to third aspects, the appropriate ratio of the different resistance values of the selected impedance element is clarified by an experimental value. Therefore, a rotation control device exhibiting the effects of the present invention can be easily manufactured.

According to the rotation control device for a brushless motor according to the fifth aspect, in addition to the effect of any one of the first to fourth aspects, the voltage discriminating circuit section and the logical sum circuit section are constituted by microcomputers. The control device can be made compact.

According to the brushless motor of the sixth aspect, since the rotation control device of the present invention is used, if a plurality of Hall elements and selective impedance elements are provided on the stator,
The structure of the stator of the brushless motor is simplified,
The number of signal lines from the stator can also be two.

The plurality of Hall elements and the selective impedance element may be provided not only in the stator but also in the interior of the brushless motor. In such a case, the number of necessary parts is small, The structure of the motor is simplified.

According to the brushless motor according to the seventh aspect, since the rotation control device of the present invention is used, the plurality of Hall elements and the selective impedance element are not limited to the inside of the brushless motor, but the tube connection portion near the same. Also in this case, the number of necessary parts is small, so that the structure of the tube connecting portion is simplified.

Further, it can be provided inside an adapter provided between the brushless motor and the tube connecting portion. In this case, the structure of the adapter is simplified and the conventional brushless motor is used. Even in the case of a motor, by adding this adapter, a plurality of Hall elements of the present invention and the above-described selective impedance element can be added, and the rotation control device of the present invention can be applied.

[Brief description of the drawings]

FIG. 1 is a block diagram conceptually showing a basic configuration of a rotation control device of a brushless motor according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a main part of a rotation control device of a brushless motor of the present invention in which a position detection circuit is incorporated.

3A is a diagram illustrating a list of various characteristics of the impedance conversion circuit unit, and FIG. 3B is a diagram illustrating a list of operation patterns thereof;

4A is an output voltage of an impedance conversion circuit, FIG. 4B is an output voltage of a voltage discrimination circuit, and FIG. 4C is an output voltage of an OR circuit.

FIG. 5 shows the off and on operations of the Hall switch of the present invention;
Diagram for explaining the relationship between the position change between the rotor and the stator

FIG. 6 is a diagram illustrating the structure of a pin-mounted stator energizing circuit.

FIG. 7 is a partially broken perspective view showing an example of the stator of the present invention.

FIG. 8 is an exploded perspective view showing an example of the brushless motor of the present invention.

FIG. 9 is a front view of a main part cutaway showing another example of the brushless motor of the present invention.

FIG. 10 is a diagram showing a wiring example for a plurality of sensors in a conventional brushless motor rotation control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotor 2 Stator 2b (Hu, Hw, Hv) Hall switch 2d Energized circuit board 2f Pin terminal 10 Brushless motor 11 Impedance conversion circuit part 12 Voltage discrimination circuit part 13 OR circuit part 14 Disconnection short circuit detection circuit part 15 Coil drive Circuit section 18 Position detection circuit 19 Microcomputer 20 Rotation control device R0 Reference impedance element Ru, Rv, Rw Select impedance element SW1 to SW3 Hall element

Continuing on the front page (72) Inventor Kenji Kino 680 Higashihama-minamicho, Fushimi-ku, Kyoto F-term in Morita Manufacturing Co., Ltd. DA19 DC04 DC13 GG04 SS01 TT07

Claims (7)

[Claims] 1. A rotor having a magnet, a stator having a coil for applying a voltage for generating a rotating magnetic field, and a plurality of holes arranged corresponding to each phase of the stator. A rotation control device for a brushless motor, comprising: a position detection circuit including an element; wherein the position detection circuit includes a selection impedance element having a different value additionally connected in parallel to each other by an ON operation of each Hall element. Is selectively connected to the reference impedance element in accordance with the on / off operation of the Hall element, and an impedance conversion circuit section configured to vary the combined impedance thereof; and Multiple thresholds are set to identify combinations of movement patterns,
A voltage discriminating circuit for discriminating an output voltage of the impedance converting circuit, and detecting off and on operations of the plurality of Hall elements in synchronization with a phase sequence change of a phase voltage applied to the stator. Therefore, a rotation control device for a brushless motor, comprising a combination of a logical sum circuit unit for calculating a logical sum of output voltages from the voltage determination circuit unit. 2. The rotation control device for a brushless motor according to claim 1, wherein the voltage discriminating circuit includes a predetermined threshold value of an operation pattern of a combination of off and on of the Hall element, a short circuit, and a disconnection. And a threshold value for identifying the rotation of the brushless motor. 3. The rotation control device for a brushless motor according to claim 1, wherein said stator has an energizing circuit board, and said energizing circuit board has said selective impedance element and said hole. A rotation control device for a brushless motor having a structure in which a Hall switch having a built-in element is mounted with pins. 4. The rotation control device for a brushless motor according to claim 1, wherein the reference impedance element and the selection impedance element are resistors, and the stator has three phases.
The ratio of different resistance values of the selected impedance element is
A rotation control device for a brushless motor, wherein the ratio is 1: 1.6 to 2.2: 4 to 5. 5. A rotation control device for a brushless motor according to claim 1, wherein said voltage discriminating circuit and said OR circuit are constituted by a microcomputer. Control device. 6. A brushless motor whose rotation is controlled by the brushless motor rotation control device according to claim 1, wherein the plurality of Hall elements and the selective impedance element are provided inside the brushless motor. And a brushless motor characterized by mounting. 7. A brushless motor whose rotation is controlled by the brushless motor rotation control device according to any one of claims 1 to 5, wherein the inside of a tube connection portion for connecting the brushless motor or the brushless motor is provided. A brushless motor characterized in that the plurality of Hall elements and the selective impedance element are mounted in any one of adapters provided between the brushless motor and the tube connection portion.