JPH04271258A - Motor - Google Patents

Abstract

PURPOSE:To suppress the occurrence of cogging torque without lowering the torque of a motor. CONSTITUTION:Out of the top face S of the core slot 31 of a rotor 3 opposed to the inside periphery 1b of a cylindrical rotor 1, the shoulder part 32 high in magnetic flux density is formed into an obliquely cut face S2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to motors, and more particularly to a brushless DC motor equipped with a rotor made of permanent magnets.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 7, the brushless DC motor has a rotor 7 consisting of a plurality of permanent magnets 71, 71, . . . arranged in a cylindrical shape, and coils 8, 8, .
There is one in which a stator 9 is formed by radially arranging a plurality of core slots 91, 91, .

[0003] In the above motor, the core slot 91
, 91 . . . When a current is sequentially applied from a control circuit (not shown) to each of the coils 8, 8, . . . , wound around the coils 8, 91, .

0004

However, in the above motor, the shape of the tip end surface 91a of the core slot 91 is matched to the inner circumferential surface 7b of the rotor 7, as shown in FIGS. 7 and 8. If the rotor 7 is made into a cylindrical shape, there is a problem that the rotor 7 generates a so-called cogging torque and does not rotate smoothly, causing magnetic noise and noise, and increasing energy loss.

[0005] As shown in FIG.
1... is the shoulder portion 91 at the tip of the core slot 91.
This occurs when passing near b. From this, it was inferred that the above-mentioned cogging torque was caused by a biased distribution (concentration) of magnetic flux at the tips of the core slots 91, 91, . . .

That is, in the conventional core slot 91,
As described above, the tip surface 91a has a cylindrical shape that matches the inner circumferential surface 7b of the rotor 7, and the shape of the tip surface 91a is cylindrical to match the inner circumferential surface 7b of the rotor 7.
Since the shoulder portion 91b has a high magnetic flux density and the central portion 91c has a low magnetic flux density, there is a large difference in the energy of the magnetic field exerted on the rotor 7. Cogging torque is generated when the polarization point 7a of the rotor 7, which also has a high magnetic flux density, passes nearby.

The inner peripheral surface 7b of the rotor 7 and the core slot 9
The generation of cogging torque can be suppressed to some extent by increasing the distance between the permanent magnet and the tip end surface 91a of the permanent magnet, that is, by increasing the air gap, or by decreasing the magnetic force of the permanent magnet. However, in either case, there is a problem in that the torque of the motor decreases. core slot 91,
If the stator 9 is arranged at an angle with respect to the axis of the stator 9 (a so-called skew angle is provided), the shoulder portion 91b having a high magnetic flux density will obliquely intersect the polarization point 7a of the rotor 7. The generation of cogging torque can be suppressed. However, in this case, there is a problem that the starting torque of the motor decreases.

The present invention has been made in view of the above circumstances, and the present invention has been made in view of the above-mentioned circumstances.
The purpose of the present invention is to provide a motor that can suppress the generation of cogging torque.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the motor of the present invention has a rotor and a stator, and a space is formed between the inner peripheral surface of the rotor and the tip of the core slot of the stator. are arranged concentrically, and both shoulders facing the adjacent core slots at the tips of the core slots facing the inner circumferential surface of the rotor increase the gap between them and the inner circumferential surface. It is characterized by its shape.

[0010] Note that the shape of the shoulder portion that increases the gap with the inner circumferential surface may be such that the shoulder portion is located inside the circumcircle of the core slot, and the shape may be a crowning connected with a gentle curve, or It includes any other shapes, such as a straight tapered surface, a step shape, and so on.

[0011]

[Operation] According to the motor of the present invention having the above configuration,
The generation of cogging torque can be suppressed. this is,
The shoulder at the tip of the core slot, which has a high magnetic flux density, is shaped to increase the gap between the shoulder and the inner circumferential surface of the rotor. This reduces the influence of the magnetic field at the tip of the core slot on the rotor, and the above shape causes fluctuations in the distribution of the magnetic field at the tip of the core slot, reducing the concentration of magnetic flux on the shoulder. It is assumed that this is the cause.

Furthermore, since the central portion of the tip of the core slot is close to the inner circumferential surface of the rotor, the torque of the motor does not decrease.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The motor of the present invention will be explained below with reference to the drawings showing embodiments. As shown in Figure 1,
The motor of this embodiment is constructed by arranging a rotor 1 and a stator 3 concentrically.

The rotor 1 includes a plurality of (six in the figure, ie, 12 poles) permanent magnets 11, 11, .
It is formed by The stator 3 includes a plurality of (nine in the figure) core slots 31, 31... which are arranged radially and have a substantially T-shaped cross section.
... includes coils 2 and 2 for synchronously rotating the rotor 1.
...is being circulated. In addition, at the center of the stator 3,
A through hole 30 is formed into which a fixed shaft (not shown) is fitted.

As shown by the two-dot chain line in FIG. 2, the core slot 31 has a center portion S1 of its tip surface S centered on the center point of the through hole 30 along the inner circumferential surface 1b of the rotor 1. Finished with a cylindrical surface. Further, as shown in FIGS. 2 and 3, both sides of the tip surface S, which is the front surface of the shoulders 32, 32 projecting left and right from the tip of the core slot 31, extend from the cylinder to the inside of the stator 3. Cut surface S2,
It is now S2. In the case of the embodiment, these cut surfaces S2, S2 are arranged so that the cut surfaces S2, S2 of the adjacent core slots 31, 31 are flush with each other, that is, the adjacent cut surfaces S2, S2 are The shape is along one plane including two generatrix lines included in the cylindrical surface constituting the cylindrical surface.

In the motor of this embodiment having the above-mentioned configuration, as shown in FIG. Since the gap with the peripheral surface 1b is large,
The generation of cogging torque can be suppressed. this is,
As mentioned above, the shoulders 32, 32 at the tip of the core slot 31, which have a high magnetic flux density, are cut to form the shoulder parts 32, 32.
32 and the inner circumferential surface 1b of the rotor 1, the influence of the magnetic field at the tip of the core slot 31 on the rotor 1 is alleviated, and the above shape allows the core to It is presumed that the cause is that the distribution of the magnetic field at the tip of the slot 31 fluctuates, and the concentration of magnetic flux on the shoulders 32, 32 is relaxed.

Furthermore, the center portion S1 of the tip surface S of the core slot 31 is finished as a cylindrical surface along the inner circumferential surface 1b of the rotor 1, and is close to the inner circumferential surface 1b.
Motor torque does not decrease. Therefore, according to the embodiment described above, it is possible to suppress the generation of cogging torque without reducing the torque of the motor.

Study of the influence of air gaps A stator 9 with a cross-sectional shape shown in FIG. 7 has coils 8, 8, . (radius 8.9
312mm, length 7mm), surface magnetic flux density 44
The rotor 7 was constructed by arranging six 00G permanent magnets 71 in a cylindrical shape so that the air gap had the value shown on the horizontal axis in FIG. 4, thereby forming the motor shown in FIG.

A torque measuring device is connected to the rotor 7 of the motor, and while rotating the motor by passing synchronous current through the coils 8, 8..., the cogging torque [OZ·IN] and the rotation speed of 3600 r. p. m. When 1 phase B. The EMF value [V] was measured. The above results are shown in FIG. In addition,
In the figure, the ─○─○─ line shows the measurement results of cogging torque, and the ─△─△─ line shows the B. It shows the measurement results of EMF values. Moreover, the dashed dotted line in the upper part of the figure indicates the above-mentioned B.
A line of 5.3V, which is the practical lower limit range of the EMF value, is shown, and the lower dotted line shows a line of 0.5 [OZ·IN], which is the upper limit range of the allowable cogging torque.

From the results shown in FIG. 4, the larger the air gap, the smaller the cogging torque, but at the same time, the B.
It was found that the EMF value also decreased and the motor torque decreased. Also, B. Even if the air gap is increased until the EMF value falls below the practical lower limit range of 5.3V, the cogging torque will greatly exceed the allowable upper limit range of 0.5 [OZ・IN]. From this, it was found that simply increasing the air gap could not sufficiently suppress the generation of cogging torque.

Study of the effect of magnetic flux density The rotor 7 is constructed by arranging six permanent magnets in a cylindrical shape with the surface magnetic flux density shown on the horizontal axis of FIG. In combination, the motor shown in FIG. 7 was formed. In addition, the air gap is 0.253m
It was set as m. Regarding the above motor, the cogging torque [OZ・IN] and
Rotation speed 3600r. p. m. When 1 phase B. EMF
The value [V] was measured.

The above results are shown in FIG. In the figure, the line ─○─○─ shows the measurement results of cogging torque, and the line ─△─△─ shows the result of measurement of cogging torque. It shows the measurement results of EMF values. Furthermore, the two upper and lower dashed dotted lines in the figure each indicate the same line as in FIG. 4 . From the results in FIG. 5, the cogging torque can be reduced as the surface magnetic flux density of the permanent magnet is reduced, but at the same time, B. The EMF value also decreases,
It was found that the motor torque decreased. Also,
B. Even if the surface magnetic flux density is reduced until the EMF value approaches the practical lower limit range of 5.3V, the cogging torque will exceed the allowable upper limit range of 0.5 [OZ・IN], From this, it was found that the generation of cogging torque cannot be sufficiently suppressed simply by reducing the surface magnetic flux density.

Examination of influence of cutting amount Each core slot 3 has a cross-sectional shape shown in FIG. 1, and the shoulder portions 32, 32, .
A stator 3 in which a coil wire having a diameter of 0.13 mm is wound 40 times around 1, 31... to form coils 2, 2...
(radius 8.9312 mm, length 7 mm), six permanent magnets 11 having a surface magnetic flux density of 3300 G were arranged in a cylindrical shape to constitute the rotor 1, and the motor shown in FIG. 1 was formed. In addition, the amount of cutting work is as shown in FIG.
It was calculated as the difference d [mm] from the radius D (=8.9312 mm). Further, the air gap was set to 0.253 mm.

Regarding the above motor, the cogging torque [OZ·IN] and the rotation speed of 3600 r. p. m. When 1 phase B. E.M.
The F value [V] was measured. The above results are shown in FIG. In the figure, the line ─○─○─ shows the measurement results of cogging torque, and the line ─△─△─ shows the result of measurement of cogging torque. It shows the measurement results of EMF values. In addition, the upper and lower two dashed lines in the figure are
Each shows the same line as in FIG. 4.

From the results shown in FIG. 6, it was found that by increasing the amount of cutting, the cogging torque could be reduced without reducing the motor torque. Also, B. EMF
While maintaining the cogging torque above the practical lower range of 5.3V, the cogging torque is kept within the allowable upper range of 0.3V.
5 [OZ·IN] could be lowered to below, and it was found that the generation of cogging torque could be sufficiently suppressed.

[0026]

Effects of the Invention The motor of the present invention is constructed as described above, and the shoulder portion at the tip of the core slot, which has a high magnetic flux density, is processed so that the rotor can be moved from the center of the tip of the core slot. Since the gap with the inner circumferential surface is large, it is possible to suppress the generation of cogging torque without reducing the torque of the motor.

[0027] Therefore, since the motor of the present invention rotates smoothly, it does not generate magnetic noise or noise or increase energy loss, and can be effectively used for applications such as servo motors. ing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the internal structure of an embodiment of a motor of the present invention.

FIG. 2 is an enlarged view of the stator used in the above embodiment.

FIG. 3 is a perspective view of the stator.

[Figure 4] Cogging torque and motor B・EMF value [
It is a graph which shows the relationship between [V] and the size [mm] of an air gap.

[Figure 5] Cogging torque and motor B・EMF value [
It is a graph which shows the relationship between [V] and the surface magnetic flux density [G] of a permanent magnet.

[Figure 6] Cogging torque and motor B・EMF value [
It is a graph which shows the relationship between [V] and the amount of cutting [mm].

FIG. 7 is a sectional view showing the internal configuration of an example of a conventional motor.

FIG. 8 is an enlarged view of the stator used in the conventional example.

[Explanation of symbols]

1 Rotor 1b Inner peripheral surface 11 Permanent magnet 3 Stator 31 Core slot 32 Shoulder S　　　　Tip surface S1 Central part S2 Cut surface

Claims (1)

[Claims] Claim 1: A rotor consisting of permanent magnets arranged in a cylindrical shape, and a stator consisting of a plurality of core slots arranged radially, between the inner circumferential surface of the rotor and the tips of the core slots. The core slots are arranged concentrically with an air gap, and the shoulders facing the adjacent core slots at the tips of the core slots facing the inner circumferential surface of the rotor increase the air gap with the inner circumferential surface. A motor characterized by being shaped like this.