JP3211457B2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stator having a stator core, a plurality of slots provided on the stator core and arranged at equal angles, and a stator winding wound around the plurality of slots. The present invention relates to an improvement of a brushless motor having a structure including a stator and a rotor having a permanent magnet rotatably provided facing a magnetic pole surface of a stator core.

[0002]

2. Description of the Related Art In recent years, brushless motors using permanent magnets for rotors have been widely used for the purpose of improving control performance, high efficiency, and low noise of rotating electric machines. FIG. 4 shows a perspective view of a stator and a rotor of a four-pole adduction brushless motor that has conventionally been generally used.

In FIG. 4, reference numeral 1 denotes a stator of a brushless motor, 2 denotes a stator core, 3 denotes six slots provided on the stator core 2 and arranged at equal angles, and 4 denotes teeth of the stator core 2. Reference numeral 5 denotes a stator winding wound around the teeth portion 4, reference numeral 6 denotes a rotor of the brushless motor, reference numeral 7 denotes a permanent magnet rotatably provided facing the magnetic pole surface of the stator core 2. Reference numeral 8 denotes a stator core 2 provided inside the permanent magnet 7.
, N and S are four-pole magnetized poles of the permanent magnet 7, and θ ₁ , θ ₂ , θ ₃ , and θ ₄ are poles N and S
Is an angle indicating the extent of the rotation direction. θ ₁ , θ ₂ , θ ₃ ,
theta ₄ is made uniform by each 90 degrees.

FIG. 5 is a cross-sectional view showing the relationship between the slots 3 and the angles θ ₁ , θ ₂ , θ ₃ , θ ₄ at the moment during operation of the brushless motor. C is the boundary between the north and south poles. For simplicity, the stator winding 5 is not shown.

[0005] The brushless motor configured as described above is operated by energizing the stator windings 5 so that a rotating magnetic field is generated corresponding to the positions of the magnetic poles N and S of the rotor 6.

In the above-mentioned conventional structure, since the winding is wound by concentrated winding, the index at the time of winding is one.
The winding process is simple, but the boundary C between the poles N and S
When passing through the teeth portion 4, a substantially sinusoidal fluctuation of the rotational torque (hereinafter referred to as cogging torque) is caused by the decrease in the magnetic resistance. This cogging torque is 4
The same occurs at the boundary portion C at three places.

[0007] Six slots 3 are equally arranged, and the angles θ ₁ , θ ₂ , θ ₃ , θ ₄ indicating the extent of the rotation of the poles N, S of the permanent magnet 7 are also equal. The cogging torque T generated by the entire brushless motor
1 is four times the cogging torque generated at one boundary.

FIG. 6 shows an angle φ indicating the positional relationship of the boundary C.
5 is a diagram showing a definition of a maximum value Tm of cogging torque generated at one location of a boundary portion C. In FIG. 6, φ is 0
The degree of cogging torque is zero, and when the permanent magnet 7 rotates in the right direction, the cogging torque increases in a substantially sinusoidal manner while increasing, and becomes zero at 180 degrees. When the permanent magnet 7 rotates in the left direction, the cogging torque changes in a substantially sinusoidal manner while decreasing, and becomes zero at minus 180 degrees.

Accordingly, the cogging torque has a substantially sinusoidal characteristic with one slot pitch and one cycle. This can be expressed as (Equation 1) by a mathematical expression.

[0010]

(Equation 1)

As described above, in the brushless motor having the conventional structure, the cogging torque T1 is generated a number of times corresponding to the number of the slots 3 of the stator core 2 during one rotation of the rotor 6, and vibration and noise are generated during operation. In the worst case, there is a problem that it cannot be put to practical use.

In order to solve this problem, Japanese Utility Model Application
As described in Japanese Patent No. 62842, the thickness of the magnet is increased at the center of the magnetic pole to reduce the amount of magnetic flux at the boundary between the poles N and S to reduce the cogging torque, and to reduce the cogging torque.
As described in Japanese Patent Application Laid-Open No. 0-55248, a design has been devised in which the shape of the magnet is changed so that the magnetic poles are skewed, and the integral value of the cogging torque in the rotation axis direction is offset.

[0013]

However, such a device has the effect of reducing or canceling the cogging torque, but on the contrary, the cost at the time of manufacture is relatively high,
In addition, there has been a problem that the output of the brushless motor cannot be obtained as a result of the decrease in the effective magnetic flux amount, and the efficiency is reduced.

The present invention solves the above-mentioned conventional problems, cancels out the cogging torque and suppresses the decrease in the effective magnetic flux amount. As a result, vibration noise during operation is small, the output is large, and the efficiency is high. An object is to provide a brushless motor at low cost.

[0015]

To achieve this object, a brushless motor according to the present invention comprises a stator core, a plurality of slots provided on the stator core and arranged at equal angles, and a plurality of slots. A stator having a wound stator winding and a pseudo slot provided at the center of the teeth of the stator core, and a permanent magnet rotatably provided facing the magnetic pole surface of the stator core. A brushless motor having a structure having a rotor having a number of poles of the brushless motor in a divisor relationship of the sum of the number of slots and the number of pseudo slots,
The permanent magnet has a configuration in which the width of the magnetized poles is set to two types, and the difference between the widened and the narrowed magnetized poles is half the pitch of one slot.

[0016]

With this configuration, the cogging torque generated at each boundary portion has a value represented by (Equation 1), but the sum of the cogging torque generated in the entire brushless motor is determined by the phase of each cogging torque. Are different and can be canceled out to zero.

[0017]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a brushless motor according to one embodiment of the present invention. 4 poles, 12 stator cores
The six slots 13 are arranged at equal angles. Further, a pseudo slot 13a having a gap sufficiently larger than the gap between the teeth and the magnetic poles is provided at the center of the six teeth of the stator core 12, and the number of poles is approximately the sum of the number of slots and the number of pseudo slots. It is a number relationship.
Magnetization pole width θ ₁₁ , θ ₁₂ , θ ₁₃ , θ _{14 of the} permanent magnet 15
Are 105 degrees (1.75 slot pitch) and 10
There are two types, 5 degrees (1.75 slot pitch), 75 degrees (1.25 slot pitch), and 75 degrees (1.25 slot pitch), and the difference between the wider and narrower is 1 slot pitch. It is configured to be half (30 degrees).

The cogging torque T2 of the brushless motor configured as described above is expressed as (Equation 2).
This value will be zero. Further, there is no significant decrease in the effective magnetic flux amount in the cogging torque reduction specification as in the above-described conventional example. Therefore, the vibration noise during operation is small and the output is large,
An efficient brushless motor can be provided.

[0020]

(Equation 2)

(Embodiment 2) FIG. 2 is a cross-sectional view of a brushless motor according to a second embodiment of the present invention. 4 poles
The number of poles and slots 13 of the stator core 12 is six and arranged at an equal angle. Furthermore, a pseudo slot 13a is provided at the center of the six teeth of the stator core, and the number of poles is a divisor of the sum of the number of slots and the number of pseudo slots. The widths of the magnetized poles of the permanent magnet 15 are θ ₂₁ , θ ₂₂ ,
θ ₂₃ and θ ₂₄ are two types of 75 degrees (1.25 slot pitch), 105 degrees (1.75 slot pitch), 75 degrees (1.25 slot pitch), and 105 degrees (1.75 slot pitch), respectively. The difference between the wide side and the narrow side is half (30 degrees) of one slot pitch.

The cogging torque T3 of the brushless motor configured as described above is expressed as (Equation 3).
This value will be zero.

[0023]

(Equation 3)

(Embodiment 3) FIG. 3 is a cross-sectional view of a brushless motor according to a third embodiment of the present invention. 4 poles
The number of poles and slots 13 of the stator core 12 is six and arranged at an equal angle. Furthermore, a pseudo slot 13a is provided at the center of the six teeth of the stator core, and the number of poles is a divisor of the sum of the number of slots and the number of pseudo slots. The widths of the magnetized poles of the permanent magnet 15 are θ ₃₁ , θ ₃₂ ,
θ ₃₃ and θ ₃₄ are 112.5 degrees (1.875 slot pitch), 82.5 degrees (1.375 slot pitch), 82.5 degrees (1.375 slot pitch), 8
There are two types, 2.5 degrees (1.375 slot pitch), and the difference between the wide and narrow sides is half (30 degrees) of one slot pitch.

The cogging torque T4 of the brushless motor configured as described above is expressed as (Equation 4).
This value is zero.

[0026]

(Equation 4)

[0027]

According to the present invention constructed as described above, it is possible to reduce the amount of magnetic flux at the boundary between N and S by changing the magnet pressure, and to prevent skew magnetization by changing the shape of the magnet. It is possible to provide a brushless motor that can cancel the cogging torque, suppress the decrease in the effective magnetic flux amount, and consequently reduce the vibration noise during operation, and have a large output and good efficiency.

Furthermore, since these effects can be realized without changing the conventional brushless motor manufacturing process,
An inexpensive brushless motor with good characteristics can be provided.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of a brushless motor according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a brushless motor according to a third embodiment of the present invention.

FIG. 4 (a) is a perspective view of a rotor of a four-pole adduction brushless motor in a conventional example. (B) is a perspective view of a stator of a four-pole adduction brushless motor in a conventional example.

FIG. 5 is a cross-sectional view showing the moment during operation of the brushless motor of FIG. 4;

FIG. 6 shows an angle φ indicating a positional relationship of a boundary C, and a boundary C
Showing the definition of the maximum value Tm of the cogging torque generated in one place of FIG.

[Explanation of symbols]

12 Stator core 13 Slot 15 Permanent magnet θ ₁₁ , θ ₁₂ , θ ₁₃ , θ ₁₄ Magnetization pole width of permanent magnet

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-42255 (JP, A) JP-A-6-86524 (JP, A) JP-A-5-137304 (JP, A) 79174 (JP, U) Actually open 56-171579 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02K 29/00, 21/00, 1/27 H02K 5/24

Claims (1)

(57) [Claims] 1. A stator core, a plurality of slots provided in the stator core and arranged at equal angles, a stator winding wound around the plurality of slots, and teeth of the stator core A brushless motor having a structure including a stator having a pseudo slot provided in a central portion thereof, and a rotor having a permanent magnet rotatably provided facing a magnetic pole surface of the stator core, The number of poles of the brushless motor is a divisor of the sum of the number of slots and the number of pseudo slots, and the permanent magnet has two types of pole widths for magnetization,
A brushless motor characterized in that the difference between the wide and narrow poles of magnetization is half of one slot pitch.