JP2006340430A - Device and method for magnetizing brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for magnetizing a magnet which can reduce cogging torque by meeting counter electromotive voltage required for a motor, in a specified magnetizing current. <P>SOLUTION: A magnetizer and columnar or circular magnetic substances are arranged to magnetize a columnar magnet. The columnar magnet is inserted into a cylindrical magnetizing yoke. The magnetizer forms 2n (n is an integer of one or over) pieces of magnetic poles in the above annular magnet by magnetic flux which pierces it through outward in the circumferential direction from the center of the magnetizing yoke by adding the magnetizing yoke a current. Each magnetic substance is arranged at the roughly center of each magnetic pole at the magnet peripheral face inserted into the above magnetizing yoke. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an annular magnet used as a rotor of a brushless motor, and more specifically to an apparatus and method for magnetizing the annular magnet. More specifically, the present invention relates to an apparatus for magnetizing an annular magnet capable of reducing cogging torque and a technique of the method.

  Information-related devices such as hard disk drives (hereinafter referred to as HDDs) and CD-ROMs in recent years are used for applications such as conventional server personal computers and desktop personal computers, as well as mobile phones, music players, and videos. Market demand is diversifying, such as shock resistance, vibration resistance, miniaturization, thinning, and noise reduction.

  In particular, the market demand for HDDs, which are expected to greatly expand their future uses, is becoming stricter year by year. Among the market demands, noise, which is one of the most familiar performances for end users, has become a market demand that cannot be met by conventional PC standards, and each HDD manufacturer has reduced noise. Various improvements have been made to achieve this.

  Noise is generated when an object vibrates, and HDD manufacturers respond to customer demand for noise reduction by means such as reducing the resonance associated with the chassis.

  On the other hand, the motor used for the HDD must meet the market demand described above as well as the HDD. In particular, with regard to motor noise reduction (reduction in vibration), increase the rigidity around the motor drive system such as the stator core and magnet, which is the reduction in vibration generation, that is, increase the fixing strength of each component, etc. It corresponds by doing.

  However, as described above, information-related devices represented by HDDs are used in audio products, home appliances, etc., and noise, which is one of the performances that end users feel most familiar, Improvement alone has made the levels unsatisfactory for end users.

  Therefore, this time, in the motor used in the HDD, the noise is reduced (reduced vibration) by reducing the cogging characteristic of the motor, which has been thought to have no significant effect on reducing the noise.

  As a means for reducing the cogging characteristics, as described in Patent Document 1, 2n (n is a value for n) of magnetizing yokes of a magnetizing apparatus in which an annular magnet is installed in a magnetic field of external magnetization and magnetized. A technique is disclosed in which cogging is suppressed to a small value by providing a salient pole of an integer of 1 or more and making the shape of the salient pole an umbrella-shaped salient and specifying the central angle and electrical angle of the arc-shaped portion of each salient pole. .

Patent Document 2 discloses a technique for suppressing the occurrence of cogging by forming an uneven shape so that a change in magnetic flux distribution at the motor coil position between two adjacent magnetic poles changes smoothly on the inner peripheral surface of a ring-shaped magnet. Is disclosed.
Japanese Patent Laid-Open No. 10-248216 JP 2001-61246 A

  Cogging characteristics affect motor vibration. The magnitude of the cogging torque is also related to the back electromotive force and the magnetizing current. In order to reduce the cogging characteristics, the magnetizing current may be reduced, but this will reduce the back electromotive voltage. Further, in order to obtain the counter electromotive voltage necessary for the motor, it is only necessary to increase the magnetizing current. However, this deteriorates the cogging characteristic (cogging increases). In addition, the current that can be passed through the magnetized yoke is also limited, and with the recent miniaturization of motors (especially 2.5 inches or less), the winding diameter inside the yoke has also become smaller, and the limit on the applied current has become larger. It has become to.

  Based on this relationship, there is a method to reduce the cogging by making the tip shape of the magnetized yoke larger than the air gap at the center of the magnetic pole to reduce cogging. Is difficult to get.

  In particular, in recent years, the miniaturization of the power block portion, that is, the configuration of the portion composed of the stator core, magnet, coil wire, etc., specifically, the axial direction of the magnet that increases the number of stacks of the stator core It has become difficult to increase the back electromotive force by increasing the height, increasing the number of turns of the coil wire, or the like.

  Therefore, an object of the present invention is to provide a magnetic material in the vicinity of the pole center, thereby satisfying the back electromotive voltage necessary for the motor while the magnetization current is limited and maintaining the low cogging characteristics. It is to provide a possible magnetizing device and magnetizing method.

  In order to solve the above-mentioned conventional problems, the invention of claim 1 is characterized in that 2n (n is an integer of 1 or more) in which an annular magnet is made of a magnetic material and a magnetizing coil connected to a magnetizing power source is wound on the outer periphery. Is inserted into a cylindrical magnetized yoke having a plurality of protrusions, and a large current is applied to the magnetized yoke by discharging the current charged in the magnetized power source, so that the center of the magnetized yoke is directed outward in the circumferential direction. Each of a magnetizing device for forming a magnetic pole having 2n poles (n is an integer of 1 or more) in the annular magnet by generating a magnetic flux penetrating through the magnet and an outer peripheral surface of the magnet inserted in the cylindrical magnetizing yoke The circumferential width of the magnetized column disposed substantially at the center of the magnetic pole is characterized by an electrical angle of 140 degrees or less.

  According to the present invention, it is possible to increase the magnetic flux of only the central part of the S pole part and the N pole part while smoothly switching the S pole and the N pole of the magnet, while maintaining the motor characteristics (back electromotive voltage). Cogging torque can be reduced.

  According to the invention of claim 2, an annular magnet is inserted into a cylindrical magnetizing yoke, an electric current is applied to the magnetizing yoke, and magnetic flux penetrates from the center of the magnetizing yoke toward the outer side in the circumferential direction. A magnetizing device for forming a magnetic pole having 2n poles (n is an integer of 1 or more) on the magnet and a predetermined gap in a portion of the outer peripheral surface of the magnet inserted in the cylindrical magnetizing yoke and opposed to the substantially central portion of each magnetic pole The magnetized columns are arranged within a range of 140 degrees or less in terms of electrical angle in a configuration in which magnetized columns arranged so as to be connected are connected, or in a state where two or more magnetized columns can be separated.

  According to the present invention, it is possible to increase the magnetic flux of only the central part of the S pole part and the N pole part while smoothly switching the S pole and the N pole of the magnet, while maintaining the motor characteristics (back electromotive voltage). The cogging torque can be reduced, and an inexpensive magnetized column can be easily attached to the magnetizing device.

  According to a third aspect of the present invention, in the first or second aspect, the magnetic body is movable in the radial direction from the center of the magnetized yoke.

  The invention of claim 4 is a brushless motor equipped with an annular magnet magnetized by the magnetizing device and magnetizing method according to claim 1, claim 2 and claim 3. It is.

  According to the third aspect of the present invention, since the coaxiality of the magnet inner diameter with respect to the outer diameter of the magnetizing yoke at the time of magnetization can be greatly improved, the occurrence of magnetizing misalignment and the like can be suppressed, and motor torque unevenness and cogging unevenness can be prevented. It is possible to reduce the number of brushless motors with low noise.

  As described above, according to the magnetizing apparatus and magnetizing method of the annular magnet according to the present invention, the magnetic body is arranged at the center of the magnetic pole, so that the switching of the S pole N pole of the magnet can be performed smoothly. It is possible to increase the magnetic flux only in the central part of the pole part and the N pole part, and the cogging torque can be reduced while maintaining the motor characteristics (back electromotive voltage).

  Further, since the coaxiality of the magnet inner diameter with respect to the outer diameter of the magnetizing yoke at the time of magnetization can be greatly improved, it is possible to suppress the occurrence of magnetization misalignment and the like to reduce motor torque unevenness and cogging unevenness.

  In addition, the annular magnetizing apparatus and magnetizing method according to the present invention do not require phasing of the magnet, so that it is possible to magnetize the conventional production tact.

  Moreover, when the movement in the radial direction is possible, it also serves as means for ensuring the positional accuracy of the magnet with respect to the magnetizing yoke, and can be magnetized with little variation in magnetization.

  Embodiments of a magnet magnetizing apparatus and magnetizing method used in the brushless motor of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a schematic diagram of an 8-pole magnetized yoke of a magnet magnetizing apparatus used in a brushless motor according to a first embodiment of the present invention. The verification of FIG. 4 was performed with a 12-pole magnetized yoke, but there was no problem because it was an electrical angle verification of a cylindrical magnetized yoke having 2n (n is an integer of 1 or more) projections.

  A magnetized annular magnet 1 shown in FIGS. 1 and 2 is inserted into an 8-pole magnetized yoke 2. On the outer periphery of the annular magnet 1 inserted into the 8-pole magnetized yoke 2, magnetized columns 3 made of a magnetic material having a fan-shaped cross section are arranged at equal intervals. In the octupole magnetized yoke 2, a coil wire 5 is wound around a stator core 4, and a high voltage current is applied to the coil wire 5 to magnetize the annular magnet 1.

  At this time, the central portion in the circumferential direction of the magnetized column 3 made of a magnetic material having a fan-shaped cross section is positioned on the approximate center line of the circumferential outer peripheral surface of each slot of the stator core 4 of the eight-pole magnetized yoke 2. The central portion of the magnetized column 3 is arranged in a range of 140 degrees or less in electrical angle on a circular line that is coaxial with the outer diameter of the annular magnet 1 and passes through the central portion of the previous magnetized column 3. ing.

  Further description will be made with reference to FIG. 2 which is a cross-sectional view taken along line a-a ′ of FIG. 1. Here, the annular magnet 1 is inserted on the outer peripheral side of the stator core 4 around which the coil wire 5 of the magnetized yoke 2 is wound with a minute gap, for example, a radial gap of 0.1 mm. Further, on the outer peripheral side of the annular magnet 1, magnetized columns 3 made of a magnetic material having a fan-shaped cross section are provided at equal intervals in the circumferential direction at the same interval as the gap. Since the magnetized column 3 is smaller than the magnetic pole width, that is, in this case, 12 poles, the electrical angle is set to 140 ° or less. The magnetized column 3 is arranged so that the inner peripheral surface side center point of the magnetized column 3 facing the point where the inner peripheral center point of the stator core 4 and the outer peripheral surface are in contact with each other at right angles is the same straight line. Has been. Even when the number of poles is different, the configuration within the above-mentioned magnetic pole angle range may be performed.

  FIG. 4 summarizes the distribution of the magnetic flux direction of the magnet in the magnetizing apparatus and the magnetizing method shown in FIG. 1, FIG. 2, and FIG. Specifically, a range of 90 degrees in electrical angle including the coil wire 5 of the salient pole portion 9 of the stator core 4 with the center point of the magnetized yoke 2 shown in FIG. 4 (d) hatched portion) was verified.

  3 (a) and 3 (b) show a state without a magnetizing ring, FIGS. 3 (c) and 3 (d) show a state with an annular magnetized ring 6, and FIGS. It is the schematic of the magnetizing apparatus of the state which has arrange | positioned the type | mold magnetic body in the magnet outer peripheral part.

  4 (a) shows a state without a magnetized ring, FIG. 4 (b) shows a state in which a fan-shaped magnetic body is disposed on the outer periphery of the magnet, and FIG. 4 (c) shows a state where FIG. The distribution of the magnetic flux direction of the magnets magnetized by the respective magnetizing devices and methods with the annular magnetized ring 6 is shown. FIG. 4D shows a verified part.

  In the state without the magnetized ring in FIG. 4A, the magnetic flux direction is perpendicular to the outer peripheral surface of the magnet in the vicinity of the center portion in the circumferential direction of the salient pole portion of the stator core 4, but as it approaches the adjacent pole. The direction of magnetic flux is approaching sideways rather than vertical.

  In a state where the fan-shaped magnetic body in FIG. 4B is arranged on the outer periphery of the magnet, the magnetic flux direction is perpendicular to the outer periphery of the magnet in the portion where the magnetized column 3 is arranged. As shown in FIG. 4A, the magnetic flux direction of the portion where the magnetized column 3 is not arranged approaches the side rather than the vertical as it approaches the adjacent pole.

  In the state with the annular magnetized ring 6 in FIG. 4 (c), the magnetic flux direction is perpendicular to the outer peripheral surface of the magnet in most parts, but in the vicinity of the adjacent pole, the magnetic flux direction is not vertical but lateral. It is approaching.

  As can be seen from the result of verifying the distribution of the above magnetic flux direction, the magnetic flux direction is perpendicular to the outer peripheral surface of the magnet from the stator core, that is, the magnet is sufficiently magnetized. This is the state 4 (c).

  However, according to the graph in which the coercive force of the pair of magnetic poles shown in FIG. 6 is compared in each case, the magnetic poles are switched (points changing from the N pole to the S pole) at an electrical angle of 180 degrees (FIG. 4C). It can be seen that the inclination angle is the largest in the case of. This indicates that cogging is the largest (vibration is large when changing from N pole to S pole). In addition, the coercive force of the pair of magnetic poles in the case of FIG. 4A (the state without the magnetizing ring) has a small inclination angle (small cogging) but a small area of the graph. This indicates that the back electromotive force is small.

  As described above, the motor is in a state where high back electromotive force and low cogging are close to ideal. The two conditions, ie, the state without the magnetized ring and the state with the annular magnetized ring do not satisfy the conditions necessary for this motor.

  On the other hand, the result of verifying the distribution of the magnetic flux direction in FIG. 4B and the coercive force of the pair of magnetic poles in FIG. 6 are in the middle positions of the two conditions, and the high back electromotive force and low cogging are close to ideal. I know that there is.

  Furthermore, FIG. 5 shows the circumferential width from the center point of the magnetized column 3 made of a fan-shaped magnetic body, that is, the back electromotive force and the cogging torque (% on the vertical axis) with respect to the magnetic pole angle (electrical angle on the horizontal axis). It is the graph which showed the relationship.

  First, regarding the relationship between the magnetic pole angle and the cogging torque, the value of the cogging torque is the lowest when the magnetic pole angle is about 0 degrees and about 108 degrees in electrical angle. Next, regarding the relationship between the magnetic pole angle and the counter electromotive voltage, it is a proportional relationship with a relatively small inclination, and is the most efficient value when the magnetic pole angle is about 108 degrees in electrical angle. For the motor, the cogging torque is small and the most effective value of the back electromotive force is ideal. That is, the state closer to the ideal state than the simulation result of FIG. 5 is the state where the cogging torque is small and the magnetic pole angle at which a relatively efficient back electromotive voltage can be obtained is about 108 degrees in electrical angle. It turns out that it is (best mode).

  Further, from the relationship between the cogging torque, the counter electromotive voltage, and the magnetic pole angle in FIG. 5, when the electrical angle is 180 degrees, the counter electromotive voltage change rate is 100% and the cogging torque change rate is 100%. Thus, the cogging torque is less than half in the portion of 140 degrees or less (indicated line portion in FIG. 5). In this range, a value close to 100% can be set for the counter electromotive voltage by setting the magnetizing column, and the magnetizing column may be set in accordance with the market demand standard.

  If this electrical angle is in the range of 140 degrees or less, it becomes possible to select the magnetic pole angle according to the market requirement standard for the counter electromotive voltage that is the performance of the motor while satisfying the low cogging torque. And the degree of freedom in designing the magnetized yoke are increased.

  FIG. 7 shows another form of the magnetized column 3 made of a magnetic material having a fan-shaped cross section at equal intervals on the outer periphery of the annular magnet 1. Each magnetized column 3 is connected to the lower side in the axial direction. By making the magnetizing column 3 in this form, it is possible to install the magnetizing column 3 with respect to the magnetized yoke 2 while maintaining the necessary coaxiality accuracy. The coaxiality of the yoke, magnet, and magnetized column becomes more accurate, and low cogging torque can be realized. Furthermore, it is desirable that there be a cut or the like so that it can be divided for fine adjustment.

  FIG. 8 shows a state in which the magnetized column 3 made of a substantially columnar magnetic body can be operated in the center direction of the magnetized yoke, not fixed. That is, by making the magnetized column 3 operable in the center direction of the magnetized yoke, the above-described gap between the magnet and the magnetized column 3 and the gap between the magnet and the stator core (magnetized yoke) can be reduced. This makes it possible to improve the magnet position accuracy with respect to the stator during magnetization. In some cases, a structure that contacts the outer periphery of the magnet (inner periphery in the case of an inner rotor) can further improve the magnet position accuracy with respect to the stator, and can suppress variations in magnetization, resulting in reduced cogging. It becomes possible.

  Although not shown, the same effect can be obtained even if the magnetized columns are connected at other than the lower side in the axial direction. In addition, it is needless to say that there is no particular restriction on the shape of the portion connecting the magnetized columns because the magnetized columns need only be connected.

  The magnetizing device and magnetizing method for a brushless motor according to the present invention can reduce cogging torque while maintaining miniaturized motor characteristics (back electromotive voltage). Furthermore, it is possible to magnetize with little variation in magnetization.

Schematic diagram of a magnetizing apparatus in Embodiment 1 of the present invention Schematic diagram a-a 'sectional view of the magnetizing device in FIG. Schematic diagram of a magnetizing device without a magnetizing ring Schematic diagram b-b 'sectional view of a magnetizing device without a magnetizing ring Schematic diagram of a magnetizing device with a magnetizing ring Schematic diagram c-c 'sectional view of a magnetizing device with a magnetizing ring The figure which shows the distribution result of the magnetic flux direction in the magnetizing device without the magnetizing ring The figure which shows the distribution result of the magnetic flux direction in the magnetizing device with the magnetizing column The figure which shows the distribution result of the magnetic flux direction in the magnetizing device with the magnetizing ring Verification range schematic diagram of magnetic flux direction Diagram showing the relationship between magnetized column position, back electromotive force and cogging Diagram showing the relationship between magnetized column position and holding force Schematic diagram of a magnetizing device in Embodiment 2 of the present invention Illustration of moving direction of magnetized column

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnet 2 8 pole magnetizing yoke 3 Magnetizing column 4 Stator core 5 Coil wire 6 Annular magnetizing ring 7 Magnetic flux direction 8 Verification range of magnetizing direction 9 Salient pole part 10 Moving direction 11 Connection part

Claims (6)

The annular magnet is attached to the cylindrical magnetizing yoke of a magnetizing apparatus in which 2n (n is an integer of 1 or more) magnetizing columns are arranged around the cylindrical magnetizing yoke provided with magnetizing coils. Insert,
In a magnetization method of applying a current to the magnetized coil to form a number of magnetic poles equal to the number of pre-magnetized columns in the annular magnet,
A method for magnetizing an annular magnet, characterized in that the circumferential width of a magnetized column disposed at substantially the center of each magnetic pole on the outer peripheral surface of the annular magnet is 140 degrees or less in electrical angle. An annular magnet is inserted into the cylindrical magnetizing yoke of a magnetizing apparatus in which 2n (n is an integer of 1 or more) magnetizing columns are arranged around the cylindrical magnetizing yoke provided with magnetizing coils. ,
In a magnetization method of applying a current to the magnetized coil to form a number of magnetic poles equal to the magnetized columns in the annular magnet,
Each magnetized column arranged with a predetermined gap is connected to the outer peripheral surface of the magnet inserted into the cylindrical magnetized yoke while facing a substantially central portion of each magnetic pole, and the magnetized column is at an electrical angle. A method for magnetizing an annular magnet, wherein the magnet is disposed within a range of 140 degrees or less. A magnetizing apparatus in which a cylindrical magnetizing yoke provided with magnetizing coils and 2n (n is an integer of 1 or more) magnetizing columns are arranged around it. 4. An annular magnet magnetizing apparatus according to claim 3, wherein the first magnetized column is movable in the radial direction from the center of the magnetizing yoke. A brushless motor on which an annular magnet magnetized by the magnetizing method according to claim 1 or 2 is mounted. A brushless motor on which an annular magnet magnetized by the magnetizing device according to claim 3 or 4 is mounted.

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