JPH08317622A - Brushless motor and rotation control method thereof - Google Patents

Abstract

PURPOSE: To provide a brushless motor and the rotation control method of the motor, which can suppress noises and vibrations to the minimum degree with the compact configuration and thin shape of the motor being achieved, and can perform the smooth rotation driving. CONSTITUTION: This is the brushless motor having a stator 3, wherein an armature coil 7 is wound around a salient pole part 5 of a stator core 6, and a rotor magnet 4, which is arranged so as to face the stator 3 with a gap being provided in the radial direction. The armature coil 7 comprises a plurality of coil phases. In the rotor magnet 4, a plurality of N poles and S poles are provided alternately in the circumferential direction. A groove part 8 is provided in the facing surface of the salient pole part 5 to the rotor magnet 4. At least a part of a coil body 9, which generates the induction voltage by the magnetic flux acting on the salient pole part 5 from the rotor magnet 4, is embedded in this groove part 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor and its rotation control method.

[0002]

2. Description of the Related Art A DC brushless motor is required to be further miniaturized and thinned while the motor structure and control circuit are complicated as the number of phases of armature coils is increased. Against this background, various types of so-called sensorless type brushless motors that do not have a rotational position detecting element such as a Hall element have been proposed in order to meet the above requirements. Such a motor is described, for example, in Japanese Patent Publication No. 6-22390. According to this, instead of the rotational position detecting element, a counter electromotive voltage induced in a coil phase that is not excited among the armature coils wound around the stator is used, whereby commutation of switching the coil phase is performed. I'm getting the timing.

[0003]

However, in the motor having the above-described structure, the back electromotive force induced in the coil phase is used to capture only the magnetic flux change amount of the winding facility portion in the (stator) salient pole teeth. However, the amount of change in magnetic flux on the other side of the rotor magnet is not sufficiently captured, and the back electromotive force can be detected only when the coil phase is not excited, making it difficult to accurately follow it. . Therefore, for the coil phase to be excited,
There is a problem that it becomes difficult to flow an appropriate exciting current, and therefore noises and vibrations such as electromagnetic noise and electromagnetic vibration become large. Furthermore, in such a state, it was difficult to desire a smooth rotational drive.

The present invention has been made to solve the above-mentioned problems existing in the prior art. The problem is to reduce the size and thickness of a motor while reducing noise and vibration. SUMMARY OF THE INVENTION It is an object of the present invention to provide a brushless motor and a rotation control method therefor capable of minimizing the rotation speed and achieving smooth rotation drive.

[0005]

In order to achieve the above object, a brushless motor of the present invention is a stator in which an armature coil is wound around a salient pole portion of a stator core, a salient pole portion of the stator core and a radial direction. A brushless magnet, wherein the armature coil comprises a plurality of coil phases, and the rotor magnet has a plurality of N poles and S poles alternately arranged in the circumferential direction. In the motor, a groove portion is provided on a surface of the salient pole portion facing the rotor magnet, and the groove portion includes a coil body that generates an induced voltage by a magnetic flux acting on the salient pole portion from the rotor magnet. At least a part is buried.

Further, in the above brushless motor, it is desirable that the groove portion is an auxiliary slot for reducing the cogging torque.

As a method for controlling the rotation of such a brushless motor, the induced voltage generated in the coil body is converted into a value corresponding to the rotational position of the rotor magnet.
The commutation signal is used to excite the armature coil.

Further, as the rotation control method, it is desirable to control the pulse width of the excitation to the armature coil by changing the electric resistance value corresponding to the temperature change of the coil body.

[0009]

According to the brushless motor of the present invention, the groove portion is provided on the surface of the salient pole portion of the stator core facing the rotor magnet. Then, at least a part of the coil body for generating an induced voltage by the magnetic flux acting from the rotor magnet to the salient pole portion is embedded in the groove portion. The induced voltage of this coil body can be used as a commutation signal for exciting the armature coil, corresponding to the rotational position of the rotor magnet. Unlike the conventional method of detecting the induced voltage by the drive coil, the coil body does not need to pass an exciting current to the coil body itself and can always detect the induced voltage. And since the coil body is arranged facing the rotor magnet, it is possible to directly capture the change in the magnetic flux from the rotor magnet,
As a result, the coil body can accurately and sufficiently grasp the amount of change in magnetic flux on the rotor magnet side of the stator, and can flow an appropriate exciting current to the excited coil phase. By controlling by such a method, noises and vibrations such as electromagnetic noises and vibrations can be minimized, and smooth rotation drive can be obtained.

Unlike the armature coil, the coil body does not need to be energized. Therefore, a coil wire having an extremely small wire diameter can be used, and the coil body itself can be made small.
Moreover, since the coil body is embedded in the groove of the salient pole portion, there is no need for a mounting space such as a conventional position detecting element, and the coil body can operate without supplying power, thus reducing the size of the motor. The thickness can be reduced.

Further, since the groove portion of the salient pole portion in which the coil body is embedded serves as an auxiliary slot for reducing the cogging torque, torque pulsation is suppressed, so that noise and vibration are further reduced in addition to the above. In addition, smooth rotation drive can be obtained.

Further, as described above, in the rotation control method in which the induced voltage generated in the coil body is used as a commutation signal for exciting the armature coil in accordance with the rotational position of the rotor magnet, The excitation of the armature coil may be pulse-width controlled by changing the electric resistance value corresponding to the temperature change of the body. Generally, the bearing rigidity of the motor tends to decrease due to the increase in the environmental temperature of the motor and the increase in the motor temperature. However, by the above pulse width control, changes in the exciting current can be gently modulated in response to a decrease in the bearing rigidity of the motor, noise and vibration can be reduced, and smooth rotational drive can be obtained. Further, since it is not necessary to provide a detection means such as a temperature sensor separately, it is more desirable to reduce the size and thickness of the motor.

[0013]

Embodiments of the brushless motor according to the present invention will be described with reference to the accompanying drawings. 1 is an overall sectional view of a spindle motor for rotating a recording disk, FIG. 2 is an enlarged perspective view of a portion of a stator 3 in FIG. 1, FIG. 3 is a perspective view showing a stator core 6 thereof, and FIG. FIG. 4 is a plan view showing a part of the core 6. This brushless motor is a device (not shown)
A housing 1 which is mounted and fixed to the side includes a rotor hub 2 which is rotationally driven by mounting a recording disk (not shown). A cylindrical portion 18 is integrally formed in the center of the housing 1 so as to penetrate therethrough in the vertical direction in the drawing. The bearing sleeve 10 is provided on the inner peripheral portion of the cylindrical portion 18.
Is installed.

The rotor hub 2 has a disk shape, and a recording disk is mounted on the stepped portion 16 on the upper surface thereof. A shaft 17 is coaxially provided on the inner side of the rotor hub 2, and a free end side of the shaft 17 is fitted into the bearing sleeve 10 to be rotatably supported. In the present embodiment, the inner peripheral portion of the bearing sleeve 10 and the outer peripheral portion of the shaft 17 fitted therein are
A dynamic pressure generating groove is provided on the bearing sleeve 10 side so that the dynamic pressure bearing is supported by the lubricating fluid. As a result, the shaft 17 is supported by the radial bearing. Further, the thrust plate 24 attached to the lower end of the cylindrical portion 18 is provided with a dynamic pressure generating groove on the upper surface thereof to receive the lower end of the shaft 17 and support the dynamic pressure bearing in the thrust direction.

The stator 3 is mounted on the outer peripheral portion of the cylindrical portion 18. A rotor magnet 4 is annularly arranged on the inner peripheral portion of the lower end of the rotor hub 2 so as to face the stator 3 in the radial direction. As shown in FIGS. 2 and 3, the stator 3 is composed of a stator core 6 formed by six salient pole portions 5 extending radially and an armature coil 7 wound around the stator core 6. . Stator core 6
Is formed by laminating thin magnetic plates such as electromagnetic steel plates to a required thickness. The salient pole portion 5 includes a pole piece 11 for winding each coil phase of the armature coil 7, and a tooth 12 facing the rotor magnet 4. An inner peripheral portion of the core back 13 having an annular shape is fitted onto the cylindrical portion 18, and a cutout groove 25 is provided in the inner peripheral portion so that the flexible circuit board 19 can be easily inserted.

A connecting portion 20 of the flexible circuit board 19 is attached to the outer peripheral portion of the upper side of the cylindrical portion 18 so as to surround it. It extends to the outside. The lead wire 21 of each coil phase of the armature coil 7 is electrically connected to the land portion provided on the connection portion 20 of the flexible circuit board 19 by soldering.

On the outer peripheral portion 14 of each tooth 12 facing the rotor magnet 4, two grooves 8 are provided at a predetermined interval in the circumferential direction, and are substantially parallel to each other in the axial direction (vertical direction in the drawing). Is formed to extend. A coil 9 provided separately from the armature coil 7 is embedded in these grooves 8, 8. Each coil 9 has a groove 8, 8 on each tooth 12.
The lead wire 22 is electrically connected to the land portion of the connection portion 20 provided on the flexible circuit board by soldering.
The grooves 8 and 8 can be used as fastening portions for integrally forming when a required number of thin magnetic plates are stacked and fixed as the stator core 6, and this portion is subjected to, for example, laser welding. Alternatively, a crimping portion for crimping and fixing can be provided.

The rotor magnet 4 has N poles and S poles alternately magnetized in the circumferential direction so that a total of 4 magnetic poles are magnetized. On the other hand, the stator 3 having the salient pole portion 5 of 6 magnetic poles is a coil of each phase. Is composed of an armature coil 7 having a three-phase coil phase, in which a salient pole portion 5 and a salient pole portion 5 that faces each other in the radial direction constitute a one-phase coil, and these are arranged to face each other in the radial direction to form a radial gap. Type outer rotor type brushless motor.

According to the brushless motor of the present invention, as described above, the surface of the stator core 6 facing the rotor magnet 4, that is, the outer peripheral portion 14 of the tooth 12, is
Grooves 8, 8 are provided. Since a coil 9 is provided in each of the grooves 8 and 8, an induced voltage is generated in the coil 9 by the magnetic flux acting on the tooth 12 from the rotor magnet 4 by the rotational driving of the motor. The induced voltage of the coil 9 can be used as a commutation signal for exciting the armature coil 7 in accordance with the rotational position of the rotor magnet 4. Therefore, the coil 9 functions as a so-called search coil for commutation. (Hereinafter, the coil 9 is referred to as a search coil)

The search coil 9 is different from the conventional method of detecting the induced voltage by the drive coil, and is different from the conventional method.
It is not necessary to send an exciting current to itself. As a result, the search coil 9 can always accurately and sufficiently grasp the amount of change in the magnetic flux on the rotor magnet 4 side of the stator 3, and an appropriate exciting current for each of the three excited coil phases. Can be drained.

Next, the energization process for properly flowing the exciting current by the circuit means for time-integrating the induced voltage of the search coil 9 will be described with reference to the circuit example of FIG. The induced voltage of the search coil 9 is time-integrated from the commutation point of the exciting current excited by the armature coil 7 to the next commutation point. The integration result is the amount of magnetic flux received from the rotor magnet 4 of the search coil 9 at that time. As a concrete means for time integration, an integrating circuit using an operational amplifier Q1 as shown in the figure can be adopted. L indicates the search coil 9,
One is connected to the minus terminal of the operational amplifier Q1 via the resistor R, and one is connected to the plus terminal. A capacitor C is connected between the output terminal of Q1 and the negative terminal.

A pair of transistors Q2 and Q3 are connected to the output side T2 of the operational amplifier Q1 and their collectors are connected via resistors R2 and R3. The respective emitters are also interconnected via diodes D1 and D2. At the bases of transistors Q2 and Q3,
The resistors R4 and R5 are connected, and the NOT circuit Q4 is further connected to the Q2 side. An impulse circuit A which is at a high level only at the time of commutation of the armature coil 7 is connected to the terminal T1 input to the transistors Q2 and Q3, and this signal is input. As a result, a predetermined integral output is obtained at the output terminal T1 of the operational amplifier Q1.

By the above control, the amount of magnetic flux received from the rotor magnet 4 on the outer circumference 14 of the stator can be directly measured. Therefore, it is easy to see whether or not the stator 3 (stator core 6) is magnetically saturated with respect to the magnetic field generated by the exciting current flowing through the armature coil 7 in the stator outer peripheral portion 14. That is, it is possible to increase the rotational torque obtained by the exciting current to the maximum without flowing unnecessary exciting current that cannot increase the magnetic flux density on the stator surface and does not contribute to the rotating torque.
The motor efficiency can be improved.

Therefore, by controlling by such a method, noises and vibrations such as electromagnetic noises and vibrations can be minimized, and smooth rotational drive can be obtained. As described above, since the search coil 9 does not need to be supplied with an exciting current or the like, a coil wire having an extremely small wire diameter can be used, and the search coil 9 does not occupy space and is bulky. It can be easily provided on the teeth 12 of the stator core 6. Search coil 9 is groove 8,
Since it is embedded in No. 8, there is no need for a mounting space such as a conventional position detecting element, and therefore, the motor can be made smaller and thinner.

According to the present embodiment, the grooves 8, 8 provided on the outer peripheral portion 14 of the tooth 12 have an electrical angle of 40 on the tooth 12 with respect to the rotor magnet 4 having a total of four magnetic poles.
The grooves 8 and 8 have a function as an auxiliary slot for reducing the cogging torque. Therefore, the stator core 6 in which the search coil 9 is embedded
By using the grooves 8 and 8 as auxiliary slots for reducing the cogging torque, torque pulsation is suppressed, so that noise and vibration are further reduced, and smooth rotational drive can be obtained.

Grooves 8, 8 are formed in the teeth 12 of the stator core 6.
In addition to the auxiliary slot, the outer peripheral portion 1 is provided.
It goes without saying that it can be provided at any position of 4. And in addition to providing all of each tooth 12,
The same number can be provided for each phase corresponding to the coil phase to which the armature coil 7 is energized. At that time, at least a part of the search coil 9 may be embedded in the grooves 8 and 8, and the search coil 9 can be freely selected depending on the groove shape and the search coil connection method. 5 and 6 shown below are
This shows another embodiment in which the search coil is wound around the teeth. As in FIG. 4, a partially enlarged view of the stator 6 is shown, and the same parts and members are given the same numbers. . Note that the armature coils are omitted from the illustration, as in FIG. 4.

According to the embodiment shown in FIG. 5, the teeth 12 of the salient pole portion 5 have the outer peripheral portion 28 formed in a stepwise shape in a plan view, so that the radial gap with the rotor magnet 4 is ( It is configured to gradually increase in size (from the left side of the figure to the right side). As a result, the rotor magnet 4
It is designed to improve the smoothness of rotation while avoiding the dead center associated with rotation of the. The search coil 26 (or 27) is wound and provided between the groove 29 on the side surface of the tooth and the step 30 (or 31) at the step-shaped boundary. In this embodiment, the search coil 26 (2
One groove in which 7) is buried is used as the stepped portion 30 (31) (hence the stepped portion is regarded as a groove). Also in this case, noise and vibration can be reduced and the motor can be made smaller and thinner as in the above-described embodiment.

In FIG. 6 shown below, a shallow groove 33 having a curved surface is provided on the outer peripheral portion 32 of the tooth 12 along the inner peripheral surface of the rotor magnet 4, and an insulating member 34 is provided on the surface of the shallow groove 33. The search coil 35 is attached. The search coil 35 may be formed in a spiral shape or a zigzag shape in addition to the winding shape shown in FIGS. 2 and 5.
It suffices if it is provided so that the magnetic flux from the rotor magnet 4 is cut off and an induced voltage is generated. Further, the search coil 35 may be used as a so-called sheet coil in which a coil body is formed on a thin insulating base material, and the search coil 35 may be provided by being attached to the groove 33. It should be noted that the groove 33 can have a groove width and a groove depth set so as to serve as auxiliary slots for reducing the cogging torque with respect to the rotor magnet 4.

Further, in FIG. 7, the outer peripheral side of the tooth may be projected, contrary to the above embodiment. As shown in the drawing, a protrusion 38 may be formed on the outer peripheral portion 36 of the tooth 12, and the search coil 37 may be wound around the protrusion 38. In this embodiment, both sides 39 of the protrusion 38 are provided. Three
The portion 9 corresponds to the mounting groove of the search coil 37.
In this case as well, the same effects as those of the above-described embodiment can be obtained, and the same effects can be obtained, and a description thereof will be omitted.

By the way, in the brushless motor shown in FIG. 1, the bearing support of the rotor hub 2 is constituted by a dynamic pressure bearing having a lubricating fluid. Generally, in this case, unlike the other ball bearings, the viscosity of the lubricating fluid decreases with an increase in the temperature of the motor and the ambient temperature, and as a result, the bearing rigidity decreases. Then, the electromagnetic noise and the electromagnetic vibration caused by the stator 3 and the rotor magnet 4 become relatively large, and the natural frequency of the motor also decreases. In particular, in a spindle motor that rotationally drives a recording disk, such a decrease in natural frequency is fatal and causes a read / write error.

However, according to the brushless motor of the present invention, even if the bearing rigidity is lowered due to the above reason, it can be dealt with by the following control method. That is, in the rotation control in which the induced voltage generated in the search coil 9 is used as a commutation signal for exciting the armature coil 7 corresponding to the rotational position of the rotor magnet 4, it corresponds to the temperature change of the search coil 9. Due to the change in the electric resistance value, the excitation of the armature coil 7 can be handled by controlling the pulse width.

As shown in FIG. 10, a current-voltage conversion circuit can be used. L the search coil 9 coil
Is connected to the base of the transistor Q5, and the collector of Q5 is connected to the power supply via the resistor R6, and is also connected to the negative terminal of the comparator Q6. The threshold voltage is input to this minus terminal. A triangular wave is input to the plus terminal of the comparator Q6. A signal having a determined pulse width is output to the output terminal of the comparator Q6. For the operation of this circuit, first, the threshold level for determining the pulse width is set. That is, when the temperature is high, the resistance value of L of the search coil 9 increases, and in this case, the base current of the transistor Q5 decreases. When the base current is small, the threshold voltage becomes high. When the threshold voltage is high, the pulse width of the output voltage becomes narrow. As the pulse width becomes narrower, the switching in the vicinity of the commutation point can be performed more slowly, and the electromagnetic vibration force due to the switching is reduced.

As a result, a more appropriate exciting current can be supplied even with respect to the motor environmental temperature and the motor temperature rise, noise and vibration can be reduced, and smooth rotational drive can be obtained. Further, since it is not necessary to provide a detection means such as a temperature sensor separately, it is more desirable to reduce the size and thickness of the motor.

The brushless motor of the present invention is shown in FIG.
A rotor magnet 4 surrounds the outer peripheral side of the stator 3,
Although the outer rotor type is shown, the present invention is not limited to this, and as another embodiment, the inner rotor type shown in FIG. 8 can be applied. Also in this case, the stator 43 is the same as in FIG.
And the rotor magnet 44 are radial gaps having a gap in the radial direction. Unlike FIG. 1, in FIG. 8, the shaft 47 is fixed to the housing 41. The rotor hub 42 is rotatably supported via the pair of bearings 48, 49 mounted on the shaft 41. Rotor hub 4
For example, a recording disk (not shown) mounted on the disk 2 is received and fixed on the collar-shaped portion 46. An annular rotor magnet 44 is externally fitted to the outer peripheral portion of a yoke member 45 provided in the lower portion of the rotor hub 42, and the rotor magnet 44 is surrounded by the stator 43 on the inner peripheral portion of the housing.

In the stator 43, the salient pole portion 52 of the stator core 50 is provided with the grooves shown in FIGS. 1 to 7, and the search coil 51 is embedded therein. Therefore, also in the brushless motor having the configuration of FIG. 8, the same operation and effect as already described can be achieved.

Although the embodiments of the brushless motor of the present invention have been described above, the design changes or modifications can be freely made without departing from the gist of the present invention, and the combinations between the respective embodiments can be appropriately selected, and the stator Shape and number of magnetic poles,
The winding method, the groove shape of the tooth portion, the arrangement method of the search coil, the number of magnetic poles of the rotor magnet, the magnetizing method and the like are arbitrary.

[0037]

Since the brushless motor of the present invention has the above-mentioned structure, it has the following effects. That is, according to claim 1 and claim 3, the search coil can accurately and sufficiently grasp the amount of magnetic flux change on the rotor magnet side of the stator, and is appropriate for the excited coil phase. A strong exciting current can be passed. By controlling by such a method, noises and vibrations such as electromagnetic noises and vibrations can be minimized, and smooth rotation drive can be obtained.

Unlike the armature coil, the search coil does not need to be energized, so that a coil wire having an extremely small wire diameter can be used, and the search coil itself can be made small. Moreover, since the coil body is embedded in the groove of the salient pole,
There is no need for a mounting space such as a conventional position detecting element, so that the motor can be made smaller and thinner.

According to the third aspect of the present invention, since the groove portion of the salient pole portion in which the search coil is embedded is an auxiliary slot for reducing the cogging torque, the pulsation of torque is suppressed. In addition, noise and vibration are reduced, and smooth rotation drive can be obtained.

Furthermore, according to claim 4, the induced voltage generated in the search coil as described above is used as a commutation signal for exciting the armature coil in accordance with the rotational position of the rotor magnet. In the rotation control method, the change of the electric resistance value corresponding to the temperature change of the search coil causes
Since the excitation of the armature coil is controlled by the pulse width, a more appropriate excitation current can be applied even when the environmental temperature of the motor or the temperature of the motor rises, and noise and vibration can be reduced and smoothed. Rotation drive is obtained. And
Since it is not necessary to provide detection means such as a temperature sensor separately,
It is more desirable to reduce the size and thickness of the motor.

As described above, according to the brushless motor of the present invention, it is possible to reduce the size and thickness of the motor, suppress noise and vibration to the minimum, and perform smooth rotation drive, and a brushless motor thereof. A rotation control method is provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an entire brushless motor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of the brushless motor shown in FIG.

FIG. 3 is a perspective view showing a main part of the brushless motor of FIG.

FIG. 4 is a plan view showing a part of the brushless motor of FIG.

FIG. 5 is a plan view showing another embodiment of the brushless motor of the present invention.

FIG. 6 is a plan view showing still another embodiment of the brushless motor of the present invention.

FIG. 7 is a plan view showing still another embodiment of the brushless motor of the present invention.

FIG. 8 is an overall sectional view showing still another embodiment of the brushless motor of the present invention.

FIG. 9 is a circuit diagram of an embodiment for driving the brushless motor of the present invention.

FIG. 10 is a circuit diagram of another embodiment for driving the brushless motor of the present invention.

[Explanation of symbols]

 1 Housing 2 Rotor Hub 3 Stator 4 Rotor Magnet 6 Stator Core 7 Armature Coil 8 Groove 9 Search Coil (Coil Body) 10 Bearing Sleeve 17 Shaft 19 Flexible Circuit Board

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H02P 6/18 H02P 6/02 371S

Claims (4)

[Claims] 1. A stator having a salient pole portion of a stator core wound with an armature coil, and a rotor magnet arranged to face the salient pole portion of the stator core with a gap in the radial direction. A brushless motor having a plurality of coil phases, wherein the rotor magnet is provided with a plurality of N poles and S poles alternately in the circumferential direction, wherein a groove portion is provided on a surface of the salient pole portion facing the rotor magnet. The brushless motor is characterized in that at least a part of a coil body that generates an induced voltage by a magnetic flux acting from the rotor magnet to the salient pole portion is embedded in the groove portion. 2. The brushless motor according to claim 1, wherein the groove portion forms an auxiliary slot for reducing cogging torque. 3. A method for controlling rotation of a brushless motor according to claim 1, wherein the induced voltage generated in the coil body excites the armature coil in correspondence with a rotational position of the rotor magnet. The rotation control method for the brushless motor is characterized in that 4. The rotation control method for a brushless motor according to claim 3, wherein the excitation of the armature coil is pulse-width controlled by changing the electric resistance value corresponding to the temperature change of the coil body.