JP2007151283A - Brushless dc motor device and permanent magnet thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To significantly reduce the size, maintain and enhance the high torque characteristics and high efficiency, and further enhance the cogging torque of a brushless DC motor. <P>SOLUTION: The brushless DC motor is comprised of: a stator made of an electromagnet; and a rotor that is disposed at the central part thereof and has a magnetic core and a permanent magnet on the outer circumferential surface thereof. The permanent magnet is an anisotropic rare-earth bonded magnet whose maximum magnetic energy product is not less than 143 kJ/m<SP>3</SP>and not more than 279 kJ/m<SP>3</SP>and which is in the shape of a thin integrated ring magnetized in 14 poles. The stator has 12-pole teeth. If the radius of the rotor is r<SB>m</SB>, the radius of the magnetic core is r<SB>c</SB>, the radial thickness of the anisotropic rare-earth bonded magnet is d, and the radius of the motor is R, the motor is so constructed that the following relation holds: the ratio of the magnet thickness to the motor radius d/R is not less than 0.025 and not more than 0.045; and the ratio of the magnetic core radius to the motor radius r<SB>c</SB>/R is not less than 0.55 and not more than 0.72. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a DC brushless motor device and a permanent magnet used therefor. In particular, the present invention relates to a motor used in a continuous operation state such as a fan motor using an SPM type motor in an inner rotor type DC brushless motor and a permanent magnet used therefor.
The present invention relates to a motor having, for example, an output of 40-400 W class and a motor radius (magnetic circuit component, corresponding to a stator radius in the present invention; the same shall apply hereinafter) of 20-65 mm. For example, in a motor that exceeds 700 W, such as a power steering motor, the output is too high and is not included in the subject of the present invention.
Further, the present invention is intended for a motor having a working voltage of 100 to 400V. Therefore, the present invention is not used for a motor that is used at a low voltage such as 12V or 24V for automobiles.

In motors that are used not only for industrial use and home appliances but mainly always rotated, brush motors that are popular as motors have not been used due to brush wear.
In this motor that is always rotated, a cage-type three-phase induction motor compatible with a three-phase AC power source has been used for industrial use. For home use, a cage-type single-phase induction motor corresponding to a single-phase AC power source was used. In the mid-1980s, industrial microcomputers appeared and industrial cage type three-phase induction motors were designed to be more efficient by inverter control using the microcomputer.
Furthermore, in the cage type three-phase induction motor, the rotor is also an electromagnet, and current is passed through the cage. Therefore, both iron loss and copper loss have been greatly increased compared to a motor using a permanent magnet.
The same efficiency was achieved by using a DC brushless motor that uses permanent magnets to improve the efficiency of the cage-type three-phase induction motor.
And the maximum magnetic energy product 32 kJ / m ³ approximately ferrite sintered magnet in this brushless motor, 8 kJ / m ³ approximately ferrite bond magnets are used.

On the other hand, for home appliances, a cage-type single-phase induction motor was mainly used until the end of the 1980s.
However, since the early 1990s, general-purpose inverter control microcomputers for home appliances have appeared. By adopting it, the current is converted into three phases, and the efficiency is improved from about 50% to about 60% by using a squirrel-type three-phase induction motor, and the motor speed is made variable by inverter control. It was. Later, due to the increasing needs for energy saving as a countermeasure against global warming, DC brushless motors were adopted for household appliances from around 2000, and the efficiency was improved to 75 to over 80%.

As described above, in the motor for continuous rotation, application to the needs for higher efficiency has progressed.
However, in recent years, there has been a growing need for maintaining or further improving the current (high torque) output characteristics and high efficiency while further reducing the size and weight.
When designing a motor here, the motor is generally selected in consideration of the operating voltage in which the motor is used, the rated rotational speed, the rated torque, the efficiency, and the cost.
Specifically, a motor with a low cost that satisfies the rated rotational speed and the rated torque is selected from the motors corresponding to the operating voltage where the efficiency is close to the maximum.
Currently, 40-400 W class brushless motors for continuous rotation use an axially anisotropic magnet of sintered ferrite with 8 magnetic poles attached.
The latest motors currently used satisfy the rated torque at the rated rotational speed at an efficiency of 80% at the operating voltage.
In this type of DC brushless motor, normally, by increasing the motor volume, the stator diameter is increased to increase the coil space, or the magnet is enlarged, and the number of coil turns and the copper wire diameter are reduced. By adjusting, high torque and high efficiency are achieved.
However, if the motor is downsized, the torque and the like are insufficient, the output characteristics are lowered, and the efficiency is lowered even if various parameters are devised.
Therefore, it was thought that miniaturization and maintenance / improvement of torque characteristics and efficiency are not compatible.
On the other hand, the miniaturization was examined in the first half of the 1980s with the advent of rare earth sintered magnets (for example, Nd sintered magnets (318 kJ / m ³ )). However, simply applying a magnet having a strong magnetic force causes the supply magnetic flux to be too large and the electromagnet yoke on the stator side to be saturated, so the stator outer diameter has to be increased. Therefore, it did not contribute to downsizing.
In addition, if a magnet having a strong magnetic force is simply used, the iron loss in the stator becomes larger than that of a conventional motor, so that high efficiency cannot be achieved.
Furthermore, if a magnet having a strong magnetic force is simply used, the cogging torque tends to increase. Therefore, simply using a strong rare earth magnet cannot reduce the size, but rather reduces efficiency and increases cogging torque (torque non-uniformity (hereinafter omitted in parentheses)).
Therefore, rare earth sintered magnets such as Nd sintered with strong magnetic force maintain or improve the current torque characteristics and high efficiency, and maintain or reduce the cogging torque after reducing the size and weight of the current DC brushless motor. In order not to solve the problem, it has not been used for brushless motors in this field.

In recent years, 159 kJ / m ³ grade anisotropic rare earth bonded magnets have appeared in the magnet field as described in JP-A-2005-116991.
Compared to sintered magnets, this magnet has excellent moldability and can be molded, oriented and magnetized in a ring shape, so that reduction in assembly man-hours and improvement in assembly accuracy can be expected, and application to brushless motors has been studied.
However, although this magnet is not as large as the Nd sintered magnet, it has the same problem because it has a much stronger magnetic force that is at least four times that of conventional ferrite magnets. It has been considered that it is difficult to achieve both reduction in size and weight of a brushless motor, maintenance and improvement of torque characteristics and efficiency, and maintenance or reduction of cogging torque.
JP 2005-116991 A

An object of the present invention is to reduce the size of a brushless motor using a sintered ferrite magnet in a small brushless motor that rotates constantly in one direction and is used in a fan motor or the like currently used and has an output of 40 to 400 W.・ If the conventional technology is reduced in weight, the torque characteristics and efficiency will be reduced and the torque characteristics and high efficiency will be maintained and improved while greatly reducing the size and weight to 1/2 or less. At the same time, the cogging torque is reduced.
In other words, if the motors have the same size, the object is to achieve both high torque characteristics, high efficiency, and reduction of cogging torque.
Another object of the present invention is to measure and maintain and improve both torque characteristics and efficiency while reducing the size and weight with a small amount of supplied magnet energy. Compared to a motor using a ferrite sintered magnet of a conventional level, the same torque and high efficiency are maintained and improved for the same supplied magnet energy while reducing the size and weight of the motor by more than 1/2.

Means for solving the problems and operational effects of the invention

The present inventors have a height of excellent magnetic characteristics and the degree of freedom of the shape of 159kJ / m ³ grade having an anisotropic rare earth bonded magnet, the results of extensive studies how to take advantage, by the following structure, It was found that the magnetic energy could be fully utilized to reduce all other issues while miniaturizing the motor.

In order to achieve the above-mentioned problem, the following means are effective.
The DC brushless motor according to claim 1 is a DC brushless motor including a stator made of an electromagnet, a rotor disposed at the center of the stator and having a magnetic core and a permanent magnet on the outer periphery thereof, wherein the permanent magnet has a maximum magnetic energy. The product is 143 kJ / m ³ or more and 279 kJ / m ³ or less, and is an integral ring-shaped, thin-walled anisotropic rare earth bonded magnet magnetized on 14 poles. The stator has 12 teeth When the radius of the rotor is r _m , the radius of the magnetic core is r _c , the radial thickness of the anisotropic rare earth bonded magnet is d, and the radius of the motor is R, the magnet thickness versus the motor The radius ratio d / R is 0.025 or more and 0.045 or less, and the magnetic core radius to motor radius ratio r _c / R is 0.55 or more and 0.72 or less.
A permanent magnet according to a second aspect of the present invention is a permanent magnet that constitutes a rotor that is disposed on the outer periphery of a magnetic core that is disposed at the center of the motor inside a stator made of an electromagnet of a DC brushless motor, The magnet has a maximum magnetic energy product of not less than 143 kJ / m ^{3 and not} more than 279 kJ / m ³ , and is an anisotropic ring-shaped anisotropic rare earth bonded magnet magnetized on 14 poles. A magnetic core radius when the radius of the rotor is r _m , the radius of the magnetic core is r _c , the radial thickness of the anisotropic rare earth bonded magnet is d, and the radius of the motor is R The motor radius ratio r _c / R is 0.55 or more and 0.72 or less, and the magnet thickness to motor radius ratio d / R is 0.025 or more and 0.72 or less. is there.

The present inventors have found that the effect is particularly great when applied to a small DC brushless motor having a 40-400 W class and a motor radius of 20-65 mm.
Furthermore, according to the present invention, for example, a brushless motor using a current sintered ferrite magnet can maintain and improve torque characteristics and high efficiency while significantly reducing the size and weight to 1/2 or less, and at the same time, reducing the cogging torque. Achieved to reduce.
In addition, compared to a motor using a conventional sintered ferrite magnet, the torque characteristic and high efficiency were maintained and improved for the same supplied magnet energy while reducing the motor size by more than 1/2.
Incidentally, if the miniaturization level is suppressed to about 30%, for example, torque characteristics or efficiency can be further improved.

Here, a motor performance index _Eα is provided as an index of an important problem of the present invention in which both torque characteristics and high efficiency are maintained and improved after being reduced in size and weight.

E _α = k _T × η / V
Here, k _T is the torque constant of the motor, eta is the maximum efficiency of the motor, V is the motor magnetic circuit volume (motor magnetic circuit unit volume (stator sectional area + rotor sectional area) × was stator lamination thickness. Less The same). This index measures the level of both high efficiency and torque per unit motor magnetic circuit volume.
The motor performance index E _α value using the present ferrite sintered magnet in this field is 0.065 or less. On the other hand, the motor performance index _Eα value of the DC brushless motor that satisfies all the configurations of the present invention is more than twice as large as that of a motor using a conventional sintered ferrite magnet. This shows that the same torque and high efficiency can be maintained when a motor using a conventional sintered ferrite magnet is reduced to 1/2 or more in size and weight.

Furthermore, as another index, a motor performance index _Eβ is provided as an index for maintaining and improving both torque and high efficiency after being reduced in size and weight with less supplied magnet energy.

E _β = k _T × η / (V × Vm × (BH) max)
Here, k _T is the motor torque constant, η is the maximum motor efficiency, V is the motor magnetic circuit volume, Vm is the magnet volume used for the motor, and (BH) max is the maximum magnetic energy product used for the motor. .
This index measures the level of both high efficiency and torque per unit motor magnetic circuit volume per unit supplied magnet energy.
In this indication, the motor performance index E _beta values using ferrite sintered magnet of the state of the art is 80.4 or less. The motor performance index _Eβ value of a DC brushless motor that satisfies all the configurations of the present invention is set to a value that is twice or more that of a motor using a conventional sintered ferrite magnet. Yes.
This shows that torque and high efficiency can be maintained for the same supplied magnet energy when the motor is reduced to 1/2 or more in size and weight compared to a motor using a conventional ferrite sintered magnet. .

The reason why the present invention has such an epoch-making effect is not clear, but considering the result, the operational effect of each component can be estimated as follows. In addition, each of these structures cannot exhibit an effect independently, but exhibits an effect by interaction between all the other structures.
In addition, the reason for limiting the numerical value is determined by producing a plurality of motors whose specifications are shown in Tables 1 to 4 and measuring the motor characteristics. The experimental conditions were fixed as much as possible, such as keeping the motor outer diameter constant, so that the effects of each factor could be extracted.

1. Anisotropic rare earth bonded magnet In the present invention, a permanent magnet is defined as an anisotropic rare earth bonded magnet.
Because it is a bonded magnet, it can be molded with high dimensional accuracy in one piece with no bonding by bonding the magnet powder and resin.
When a ferrite sintered or rare earth sintered magnet is used, there is a magnetic resistance due to a gap between the magnet and the rotor due to a dimensional difference within a manufacturing intersection for each piece, a gap due to an adhesive between the magnet and the rotor, or the like. Further, when these are used, cogging torque is generated due to non-uniform gaps between the magnets due to positioning errors during bonding positioning, non-uniform gaps between the stator and magnets, and the like. On the other hand, by using an anisotropic rare earth bonded magnet integrally formed into a ring shape, it is possible to significantly reduce these magnetic resistances and improve the generation of cogging torque. In addition, since there is no gap between the magnetic poles, the magnetic flux supply area can be increased and sufficient magnetic flux can be supplied.
In addition, although the sintered magnet has a small electric resistance, the bond magnet is covered with a resin, which is an insulator, and rare earth metal particles are covered. Therefore, the generation of eddy current is reduced and the efficiency is improved.

2. Magnet Maximum Magnetic Energy Product The anisotropic rare earth bonded magnet of the present invention is required to have a maximum energy product of 143 kJ / m ³ or more and 279 kJ / m ³ or less after satisfying the other configuration of the present invention. Thereby, the subject of this invention can be achieved as mentioned above.
Figure 1 shows the effect of the magnet maximum magnetic energy product for the motor performance index E _alpha. Here, the experimental conditions are shown in Table 1.

ここでは最大磁気エネルギー積以外の諸元は固定している。最大磁気エネルギー積の増加に伴い性能指標Ｅ_αは、はじめは急激に増加し、その後は増加率が徐々に低下していく。
図１中の黒丸●は、従来使用されている８極着磁したフェライト焼結磁石を使用したモータ（以下、従来例と記す。）のモータ性能指標Ｅ_αを示す。また、図中の太点線は、従来例の２倍の性能を示す線である。この図より、最大磁気エネルギー積が１４３ｋＪ／ｍ^３を超えると、従来例の２倍以上の性能指標Ｅ_αを得ることができる。

Here, the specifications other than the maximum magnetic energy product are fixed. Maximum magnetic energy product performance index E _alpha with an increase in, initially rapidly increased, then the rate of increase gradually decreases.
A black circle in FIG. 1 indicates a motor performance index E _α of a motor (hereinafter, referred to as a conventional example) using a ferrite sintered magnet magnetized with eight poles, which has been conventionally used. Moreover, the thick dotted line in a figure is a line which shows the performance twice as much as a prior art example. From this figure, when the maximum magnetic energy product exceeds 143 kJ / m ³ , a performance index E _α that is twice or more that of the conventional example can be obtained.

Figure 2 shows the effect of maximum magnetic energy product of the permanent magnets for the motor performance index E _beta. Here, the experimental conditions are the same as in Table 1. As the maximum magnetic energy product increases, the performance index _Eβ initially decreases rapidly, and then the rate of decrease becomes moderate.
The filled in circles ● shows the motor performance index E _beta prior art. From this figure, when the maximum magnetic energy product is 279 kJ / m ³ or less, it is possible to obtain a motor performance index E _β that is twice or more that of the target conventional motor.
In this experiment, experiments at 239, 318, and 398 kJ / m ³ were performed by computer simulation. This is because an anisotropic rare earth bonded magnet of this level cannot be manufactured at this time.
From the above, the maximum magnetic energy product of the permanent magnet is set to 143 kJ / m ³ or more and 279 kJ / m ³ or less.

3. Magnet thickness d / stator radius r ratio (hereinafter referred to as d / r value)
By making the d / r value of the permanent magnet as thin as 0.025 or more and less than 0.045, the object of the present invention can be achieved as described above in combination with other components.
Figure 3 shows the effect of the d / r value for the motor performance index E _alpha. Here, the experimental conditions are shown in Table 2.

ステータ諸元を固定し、ロータ部の外径一定で、磁石厚さを変化させた。ｄ／ｒ値の増加に伴い性能指標Ｅ_αは急激に増加し、その後、性能指標Ｅ_αが飽和する。
図中の黒丸●は、従来例のモータ性能指標Ｅ_αを示す。また、図中の太点線は、従来例の２倍の性能を示す線である。この図より、ｄ／ｒ値が０．０２５以上では、目標である従来モータの２倍以上の性能指標Ｅ_αを得ることができる。

The stator specifications were fixed, and the magnet thickness was changed with the outer diameter of the rotor portion being constant. As the d / r value increases, the performance index _Eα rapidly increases, and then the performance index _Eα is saturated.
The filled in circles ● shows the motor performance index E _alpha conventional example. Moreover, the thick dotted line in a figure is a line which shows the performance twice as much as a prior art example. From this figure, the d / r value is 0.025 or more, it is possible to obtain more than twice the performance index of the conventional motor is the target E _alpha.

Figure 4 shows the effect of d / r value for the motor performance index E _beta. Here, the experimental conditions are the same as in Table 2. The increase in accordance with the performance indicators _E β of d / r value decreases rapidly, then, reduction rate has slowed. Bold circle in FIG ● shows the motor performance index E _beta prior art. A thick dotted line in the figure indicates a motor performance index _Eβ that is twice that of the conventional example. From this figure, the d / r value is 0.045 or less, it is possible to obtain more than twice the motor performance index of the conventional example is the target E _beta.
From the above, the d / r value of the permanent magnet is set to 0.025 or more and 0.045 or less.
The thickness of the anisotropic rare earth bonded magnet is preferably 0.7 mm or more and 2.5 mm or less.

4). Magnetic core radius to motor radius ratio r _c / R (hereinafter referred to as r _c / R value)
By setting the r _c / R value of the permanent magnet to 0.55 or more and 0.72 or less, the problem of the present invention can be achieved in combination with other constituent elements.
FIG. 5 shows the influence of r _c / R on the motor performance index E _α . Here, the experimental conditions are shown in Table 3.

ここでは、モータ外径（ステータ外径と同じ）Ｒと磁石厚さｄを固定し、磁性コア半径ｒ_ｃを変化させ、その他の諸元を固定した。ｒ_ｃ／Ｒ値の増加に伴い性能指標Ｅ_αは増加し、途中でピークを持ち、その後減少することを発見した。
このｒ_ｃ／Ｒ値は、本発明の特徴部分なので、従来例においてもモータ性能指標Ｅ_αに対する上記ｒ_ｃ／Ｒ値の影響を測定した。実験条件は、本発明と同様に、従来例のモータの諸元を、モータ外径（ステータ外径と同じ）Ｒと磁石厚さｄを固定し、磁性コア半径ｒ_ｃを変化させ、その他の諸元を固定しておこなった。従来例におけるモータ性能指標Ｅ_αに対する上記ｒ_ｃ／Ｒ値の影響は図中の黒丸●で示した。従来例のモータは磁石厚さ、磁石の最大磁気エネルギー積、磁石磁極等が大きくことなるためか、性能指標Ｅ_αのピークが０．０６５と低く、そのピークを示すｒ_ｃ／Ｒ値は０．３８のあたりにある。
図中の太点線は、従来例モータにおいてｒ_ｃ／Ｒ値を振ったときの最高値の２倍の性能指標Ｅ_αを示す線である。永久磁石のｒ_ｃ／Ｒ値を０．５５以上、０．７２以下の範囲で目標値である従来例の２倍以上のモータ性能指標Ｅ_αを得ることができる。よって、永久磁石のｒ_ｃ／Ｒ値を０．５５以上、０．７２以下としている。

Here, R and magnet thickness d (same as the stator outer diameter) motor outer diameter is fixed and varying the magnetic core radius r _c, to fix the other specifications. r c _/ a with performance index increase in _R value E _alpha increases found that middle has a peak, then decreases.
Since this r _c / R value is a characteristic part of the present invention, the influence of the r _c / R value on the motor performance index E _α was also measured in the conventional example. Experimental conditions were similar to the present invention, a conventional example of specifications of the motor, the motor outer diameter (same as the stator outer diameter) to secure the R and magnet thickness d, by changing the magnetic core radius r _c, other It was done with fixed specifications. The influence of the r _c / R value on the motor performance index E _α in the conventional example is indicated by black circles ● in the figure. Conventional motor magnet thickness, or for different maximum magnetic energy product, magnet poles, etc. is large magnets, low peak performance indicators E _alpha is 0.065, the r _{c /} R value indicating the peak 0 It is around .38.
The thick dotted line in the figure is a line indicating a performance index _Eα that is twice the maximum value when the r _c / R value is swung in the conventional motor. The r _{c /} R value of the permanent magnets than 0.55, it is possible to obtain more than twice the motor performance index E in the conventional example is a target value _α in the range of 0.72 or less. Therefore, the r _c / R value of the permanent magnet is set to 0.55 or more and 0.72 or less.

5. Number of Magnet Pole The above-mentioned permanent magnet can achieve the object of the present invention by being magnetized to 14 poles mainly in the radial direction while being satisfied with the other configuration of the present invention.
By being magnetized mainly in the radial direction, magnetic flux can be supplied to the stator facing the magnet. The magnetic pole of the magnet is a multiple of two.
FIG. 6 shows the influence of the number of magnetic poles of the permanent magnet on the cogging torque. The experimental conditions are shown in Table 4.

ここでは、磁石磁極数のみを変化させている。磁極数の増加に伴い、コギングトルクが減少し、１４極で最小値を取り、１６極で大幅に増加する。図中の太丸●は、従来例のコギングトルクを示している。図中の太点線は、従来例のコギングトルクを示す。この図より、磁石磁極数が１４極において、従来例よりもコギングトルクの低減することができる。

Here, only the number of magnet magnetic poles is changed. As the number of magnetic poles increases, the cogging torque decreases, takes a minimum value at 14 poles, and increases significantly at 16 poles. A bold circle ● in the figure indicates the cogging torque of the conventional example. The thick dotted line in the figure indicates the cogging torque of the conventional example. From this figure, when the number of magnetic poles is 14, the cogging torque can be reduced as compared with the conventional example.

Figure 7 shows the effect of the number of magnet poles of the motor performance index E _alpha. Here, the experimental conditions are the same as in Table 4.
Motor performance index E _alpha has a peak in the number of magnet poles 14 poles. Bold circle in FIG ● shows the motor performance index E _alpha conventional example. Moreover, the thick dotted line in a figure is a line which shows the performance twice as much as a prior art example. From this figure, it is possible to magnet poles get more than twice the performance index of a conventional motor, which is the target E _alpha 14 poles.

In order to supply magnetic flux to the stator facing the magnet, the orientation / magnetization of the magnet is appropriately selected from generally used radial orientation / magnetization, polar orientation / magnetization, hybrid orientation / magnetization, etc. be able to. The hybrid orientation / magnetization is a method in which, in a ring magnet composed of a plurality of magnetic poles, the main pole portion is radially oriented / magnetized, and the interface portion between adjacent main pole portions is polar anisotropic oriented / magnetized. In addition, a known orientation / magnetization method can be used.

6). Status lot number The number of slots must be 12 poles.
In the case of a brushless motor, the number of slots is a multiple of three. When the number of magnetic poles of the magnet is 14, the number of slots is the minimum of the number of magnetic poles and the number of slots in order to minimize the cogging torque and from the viewpoint of symmetry of the magnetic attraction force related to the stator. The common multiple is relatively large and 12 poles, which are even poles.
In the experiments described so far, the shape of the stator teeth was set such that the width h of the teeth pole and the thickness t of the back yoke portion of the teeth were constant as shown in FIG.

7). The number of coil turns is preferably 150 to 400 turns, which is a common-sense range that is usually used in a small (inner rotor type SPM) DC brushless motor of a general AC power supply. In this experiment, in order to make the conditions constant, the volume was set to 360 and the space factor was constant. The coil winding method was a concentrated winding method.

8). Working voltage The working voltage of the present invention is used in the range of 100 to 400V. In general, a high voltage type is used to reduce power consumption. In the high voltage type, the number of coil turns is increased, the magnetomotive force is increased, the coil wire diameter is reduced, the electric resistance of the coil is increased, and the current is reduced, thereby reducing the power consumption. This experiment was performed at 280 V in order to keep the conditions constant. Note that the air gap between the stator and the rotor is constant at 0.5 mm this time. However, when this gap is reduced, the magnetic resistance is further reduced, and the size can be further reduced.

  Hereinafter, the present invention will be described based on embodiments. In addition, this invention is not limited to the following embodiment.

FIG. 8 is a cross-sectional view of a magnetic circuit component of a DC brushless motor (hereinafter simply referred to as a motor) according to an embodiment of the present invention. The motor of the embodiment is flattened in the stacking direction of the motor in the direction perpendicular to the drawing, and realizes a significant downsizing that reduces the volume of the magnetic circuit portion to ½. Of course, the motor stacking thickness direction is constant, and the motor outer diameter can be reduced.

The motor according to this embodiment includes a stator 1, a coil 2 wound around the stator, a rotor 3 provided at the center of the motor, and a rotating shaft 4 extending from the center of the rotor 3. In the rotor 3, an anisotropic rare earth bonded magnet 32, which is an integral ring-shaped permanent magnet, is arranged on the outer periphery of a cylindrical magnetic core 31.
For comparison in volume, FIG. 9 shows an 8-pole-12-tooth motor using a conventional sintered ferrite magnet 932 as a conventional example. FIG. 10 shows a case in which the sintered ferrite magnet 932 and the anisotropic rare earth bonded magnet 832 are simply replaced in the 8-pole-12-tooth structure using the conventional sintered ferrite magnet 932 as Comparative Example 1. In this case, even if the anisotropic rare earth bonded magnet is simply replaced with 9 mm, it cannot be magnetized. Therefore, in Comparative Example 1, it is assumed that magnetization has been achieved, and the result of computer simulation is listed. Here, for comparison, the other specifications of the motor using the conventional ferrite sintered magnet 932 and the motor simply replacing the magnet are the same.

In Comparative Example 2, in the structure of 8 poles-12 teeth using the conventional sintered ferrite magnet 932, the sintered ferrite magnet 932 and the anisotropic rare earth bonded magnet 832 have the same output characteristics as the conventional example. FIG. 11 shows the case where is replaced. Here, for comparison, the magnet thickness d was set so that the dimensional specifications other than the magnet thickness d were the same, and the output characteristics were the same as the conventional example.
Further, for comparison between the conventional motor and the present invention, in the embodiment, the stator outer diameter (same as the motor outer diameter) is the same as that of the conventional motor, and the output characteristics are the same.

  Table 5 shows the specifications and evaluation results of each example, conventional example, and comparative example.

尚、上記異方性希土類ボンド磁石３２は、出願人により、近年ようやく量産化が可能となったものである。例えば、この異方性希土類ボンド磁石３２は、特許２８１６６６８号公報、特許第３０６０１０４号公報の製造方法で作製される。この異方性希土類ボンド磁石３２は、最大磁気エネルギー積で２１５ｋＪ／ｍ^３程度までのものを現在製造することができる。

The anisotropic rare earth bonded magnet 32 has been finally mass-produced by the applicant in recent years. For example, the anisotropic rare earth bonded magnet 32 is manufactured by the manufacturing method described in Japanese Patent No. 2816668 and Japanese Patent No. 3060104. This anisotropic rare earth bonded magnet 32 can now produce one of up to about 215kJ / m ³ a maximum magnetic energy product.

The difference between the motor of this embodiment (FIG. 8) and the conventional motor (FIG. 9) is that 8 poles of sintered ferrite magnet 932 having a maximum magnetic energy product of 32 kJ / m ³ of the conventional motor is first attached. Instead of the arrangement, 14 magnetic poles are adopted in the integrated ring-shaped anisotropic rare earth bonded magnet 32 made of Nd-FE-B magnet powder having a maximum magnetic energy product of 183 kJ / m ³ or the like. Here, any known materials can be used for the anisotropic rare earth bonded magnet.
The second feature is to make the permanent magnet thinner. In the conventional motor, the magnet thickness is 9 mm, but the magnet thickness in this embodiment is as very thin as 1.5 mm. According to Table 5, the magnet thickness to stator radius ratio d / R is 0.025 and satisfies 0.025 or more and 0.045 or less at 0.030.
Furthermore, the greatest feature of the present invention is that the ratio of the magnetic core in the entire motor in the radial direction is greatly increased as compared with the conventional motor. That is, the ratio of the magnetic core radius to the motor radius r _c / R is made larger than that of the conventional motor. In the motor of the conventional example, _{r c} / R value is 0.38 and the proportion of the magnetic core is small, the motor of the present invention, at _{0.69, r} c / R value at 0.55 above, 0.72 Satisfying the following, it is greatly increased as compared with the conventional example.

By adopting these configurations, as shown in Table 5, compared to the conventional example, in the case of the example, the height in the motor shaft direction is greatly reduced to ½ in the same output characteristics, and the volume Is reduced to 1/2. This example also, to 2.1 times compared with the conventional example in motor performance index E _alpha, in the motor performance index E _beta is compared to the conventional example, it is significantly improved to 2.7 times. Further, the cogging torque is reduced by about 20% compared to the conventional example. When this embodiment is applied to a fan motor, rotation unevenness can be greatly reduced.

In Comparative Example 1, since the sintered ferrite magnet 932 is simply applied to the anisotropic rare earth bonded magnet 832, the output characteristic is about 1.5 times, but the motor performance index E _α is the same as the conventional example. Although it is improved to some extent by 1.6 times compared with the present invention, it is not possible to obtain an excellent effect that exceeds twice as in the present invention. Further, the motor performance index E _beta of Comparative Example 1, compared with the conventional example, as reduced to 1/4 Conversely, not be totally effective use of the supply magnet energy exceeds twice as in the present invention An excellent effect is not obtained at all.
These are presumably because, when a strong magnet is used excessively with the magnetic circuit configuration of the conventional example, a large iron loss is generated and the magnet energy per unit magnet usage is reduced. Further, the cogging torque is extremely increased by 24 times compared to the conventional example, and the reduction of the cogging torque as in the present invention is not seen at all.

In Comparative Example 2, when the anisotropic rare earth bonded magnet 832 is applied instead of the ferrite sintered magnet 932, the output characteristics are made the same, and the magnet thickness is set to the d / R value. In order to satisfy, it is set to 0.04. The motor performance index _Eα is improved to some extent by about 1.6 times as compared with the conventional example, but an excellent effect exceeding twice as in the present invention cannot be obtained. Also, the motor performance index E _beta of Comparative Example 2, compared with the conventional example, although improved to some extent about 1.6 times, 2 times exceeds such excellent effects of the present invention can not be obtained. These are mainly reduced in torque constant and efficiency in this case because the magnet poles are the same eight poles as the conventional example and the _rc / R value is 0.53 outside the scope of the present invention. I think that the.
Further, the cogging torque is extremely increased by 16 times compared to the conventional example, and the reduction of the cogging torque as in the present invention is not seen at all.
As described above, the present invention does not simply apply a high performance anisotropic rare earth bonded magnet to the structure of 8 poles-12 teeth using a conventional sintered ferrite magnet, but has a high potential of the anisotropic rare earth bonded magnet. By organically combining the number of magnetic poles, magnet thickness, magnetic core radius, etc., brushless motors using current sintered ferrite magnets can be significantly reduced in size and weight to 1/2 or less, which could not be predicted in the past. However, the present invention provides a DC brushless motor that maintains and improves torque characteristics and efficiency, and at the same time achieves cogging torque reduction.

The above-described experimental examples and examples have been studied focusing on 40 W class motors.
Here, FIG. 12 and FIG. 13 show values of motor performance indexes E _α and E _β of a motor in which a conventional ferrite sintered magnet of 40 to 200 W is configured with 8 magnetic poles and a motor according to the configuration of the present invention. The configuration of these motors is shown in Table 6.

図１２から、本発明のモータは４０〜２００Wにおいて、モータ性能指標Ｅ_αが、従来例に比べ２倍以上の性能を有していることがわかる。
また、図１３においても、本発明のモータは４０〜２００Wにおいて、モータ性能指標Ｅ_βが、従来例に比べ２倍以上の性能を有していることがわかる。

From Figure 12, the motor of the present invention in 40～200W, motor performance index E _alpha is seen to have more than twice the performance compared with the conventional example.
Also in FIG. 13, the motor of the present invention in 40～200W, motor performance index E _beta is seen to have more than twice the performance compared with the conventional example.

  The present invention relates to a DC brushless motor that always rotates in one direction, and is required to simultaneously reduce and reduce cogging torque while maintaining and improving torque characteristics and efficiency while significantly reducing size and weight. Can be used for motors. When the motor size is the same, the present invention can also be used for a DC brushless motor that requires high performance in torque characteristics and efficiency and reduction in cogging torque. In particular, the present invention is useful when used for a fan motor having an output of 40 to 400 W class. Here, the rated rotational speed in the case of a fan motor is about 1000 to 4000 rpm. It is also useful for positioning servo motors. However, the application is not limited to a fan motor or the like.

Characteristic diagram showing the relationship between the anisotropy maximum magnetic energy product and motor performance index of the rare-earth bonded magnet E _alpha Characteristic diagram showing the relationship between the anisotropy maximum magnetic energy product and motor performance index of the rare-earth bonded magnet E _beta characteristic diagram showing the relationship between d / R value and the motor performance index E _alpha characteristic diagram showing the relationship between d / R value and the motor performance index E _beta characteristic diagram showing the relationship between r c _{/ R} value and the motor performance index E _alpha Characteristic diagram showing the relationship between the number of magnet poles and cogging torque Characteristic diagram showing the relationship between the number of magnet poles and the motor performance index E _alpha Magnetic circuit sectional view of the DC brushless motor of the present invention Cross-sectional view of magnetic circuit of DC brushless motor using conventional sintered ferrite magnet Magnetic circuit sectional view of DC brushless motor of Comparative Example 1 Magnetic circuit sectional view of DC brushless motor of Comparative Example 2 Motor motor output and the present invention, and a characteristic diagram showing a relationship between the motor performance index E _alpha motor using a conventional sintered ferrite magnets Motor motor output and the present invention, and a characteristic diagram showing the relationship between the motor performance index E _beta of the motor using the conventional sintered ferrite magnets

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator of this invention 2 Coil of this invention 3 Rotor of this invention 31 Magnetic core of this invention 32 Anisotropic rare earth bonded magnet of this invention 4 Rotating shaft of this invention 91 Stator of conventional example 92 Coil of conventional example 93 Conventional example Rotor 931 Conventional magnetic core 932 Conventional ferrite sintered magnet 94 Conventional rotary shaft 81 Comparative stator 82 Comparative coil 83 Comparative rotor 831 Comparative magnetic core 832 Comparative anisotropy Rare earth bonded magnet 84 Comparative example rotating shaft

Claims (2)

A DC brushless motor comprising a stator comprising an electromagnet, a rotor having a magnetic core disposed at the center thereof and a permanent magnet on its outer periphery;
The permanent magnet has a maximum magnetic energy product of 143 kJ / m ³ or more and 279 kJ / m ³ or less, and is an integral ring-shaped, thin-walled anisotropic rare earth bonded magnet magnetized to 14 poles,
The stator has 12 poles of teeth,
When the radius of the rotor is r _m , the radius of the magnetic core is r _c , the radial thickness of the anisotropic rare earth bonded magnet is d, and the radius of the motor is R,
The magnet thickness to motor radius ratio d / R is 0.025 or more and 0.045 or less,
A DC brushless motor having a magnetic core radius to motor radius ratio r _c / R of 0.55 or more and 0.72 or less. A permanent magnet which is disposed inside the stator made of an electromagnet of a DC brushless motor and is disposed on the outer periphery of a magnetic core disposed at the center of the motor, and constitutes a rotor,
The permanent magnet has a maximum magnetic energy product of 143 kJ / m ³ or more and 279 kJ / m ³ or less, and is an integral ring-shaped, thin-walled anisotropic rare earth bonded magnet magnetized to 14 poles,
The stator has 12 poles of teeth,
When the radius of the rotor is r _m , the radius of the magnetic core is r _c , the radial thickness of the anisotropic rare earth bonded magnet is d, and the radius of the motor is R,
The magnetic core radius to motor radius ratio r _c / R is 0.55 or more and 0.72 or less,
A permanent magnet having a magnet thickness to motor radius ratio d / R of 0.025 or more and 0.72 or less.

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