JP2001145280A - Permanent magnet synchronous motor - Google Patents

Abstract

(57) [Problem] To provide a stator and a permanent magnet even when the number of permanent magnet groups provided on a rotor yoke of a radial air gap type permanent magnet synchronous motor is two or three. The fluctuation of the magnetic flux during rotation is reduced to suppress the torque fluctuation during rotation. SOLUTION: A stator having a plurality of magnetic plates laminated in the axial direction of the rotor, and the rotor are arranged around a rotor yoke provided in the axial direction and at intervals in the axial direction. It has at least two permanent magnet groups, each of the two permanent magnet groups has a plurality of permanent magnets magnetized in the radial direction of the rotating shaft, and the two permanent magnet groups are located on the rotor yoke. Radial air
In the gap type permanent magnet synchronous motor, a magnetic plate corresponding to a gap between the two sets of permanent magnets among the plurality of magnetic plates is replaced with a non-magnetic plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a synchronous motor using a permanent magnet, and more particularly to a permanent magnet synchronous motor in which torque fluctuation (torque pulsation) of the motor is reduced.

[0002]

2. Description of the Related Art Synchronous motors using permanent magnets are widely used as control motors such as servomotors because of their high efficiency and excellent controllability.

FIG. 4 is a sectional view of a conventional radial air gap type permanent magnet synchronous motor cut in a direction perpendicular to a rotor axis. A rotor yoke 12 is provided in an axial direction of the rotor shaft 10 (a direction perpendicular to the drawing) and around the shaft 10, and around the rotor yoke 12,
A plurality (six in the illustrated case) of permanent magnets 14 are arranged.

The plurality of permanent magnets 14 are alternately magnetized in opposite directions (the direction of magnetization is indicated by an arrow). Each of the plurality of permanent magnets 14 has a circumferential direction (a circumferential direction of the rotor shaft 10).
Is thinner than the center (the reason will be described later). Because of this cross-sectional shape, each of the permanent magnets 14 is also called a C-shaped magnet. The rotor 16 is provided with the rotor shaft 1 described above.
0, a rotor yoke 12, and a plurality of permanent magnets 14.

Around the rotor 16, a gap (air gap: about 0.7 m) is formed in a radial direction (radial direction).
m), a stator 18 is provided. As described above, since the air gap is provided in the radial direction, the permanent magnet synchronous motor shown in FIG. 3 is referred to as a radial air gap type.

The stator 18 has a stator yoke 20 and a plurality of teeth (teeth) 22 extending from the stator yoke 20 to the inside. Further, a coil (a three-phase Y-connection distributed and wound) is provided in the slot 24 between the teeth. U, V, and W shown in the figure indicate that the coil has a three-phase winding. In the example of FIG. 4, the number of teeth 22 is 18
The number of turns of each coil (the number of turns per slot) is, for example, about 30 turns.

FIG. 5A is a plan view of the stator 18 viewed from the axial direction of the rotating shaft 10, and FIG. 5B is a sectional view of the stator 18 taken along line AA in FIG. It is sectional drawing. As shown in FIG. 5B, the stator 18 is formed by stacking a plurality of magnetic thin plates 26 (for example, an electromagnetic steel plate, a silicon steel plate, or the like having a thickness of about 0.5 mm).

When the permanent magnet type synchronous motor shown in FIGS. 4 and 5 is used as a servomotor or the like that requires high-precision torque control, torque fluctuations during motor rotation (torque pulsation, cogging torque) It is important to make) as small as possible.

The change in magnetic flux density (flux disturbance) in the air gap (air gap) between the permanent magnet 14 and the teeth 22 of the stator 18 appears as a motor torque fluctuation.

As one method for reducing the torque fluctuation during rotation, as described above, the end portions of the permanent magnet 14 are made thinner than the center portion to reduce the change in the magnetic flux density in the air gap. Has been conventionally proposed.

As a method of further reducing the torque fluctuation, as shown in FIG. 6, two permanent magnet groups 30 and 32 are arranged in the axial direction of the rotating shaft 10 and at intervals around the rotor yoke 12. In addition, it has been proposed that the positions of the permanent magnet groups 30 and 32 in the circumferential direction are shifted from each other. Although the two permanent magnet groups 30 and 32 themselves have the same configuration, the permanent magnet groups 30 and 32 are fixed to the rotor 16 when the rotor 16 rotates by disposing them in the circumferential direction. The change in the magnetic flux density in the air gap with the element 18 can be reduced.

That is, the disturbance of the lines of magnetic force at the respective ends of the plurality of permanent magnets constituting each set of permanent magnets is reduced by shifting the two sets of permanent magnets relative to each other in the circumferential direction of the rotor yoke 12. That is what we are trying to solve.

The distance 34 between the two sets of permanent magnets 30 and 32 in the axial direction of the rotor varies depending on the size of the motor itself, but is about 0.5 mm to 5.0 mm. The angle θ of the “shift” in the circumferential direction between the two permanent magnet groups 30 and 32
Is called a step skew angle. Although two sets of permanent magnet groups 30 and 32 are shown in FIG. 6, three sets can be used if the rotor shaft is long enough.

However, as described above, when the number of the permanent magnet groups is small (two or three), the step skew angle is large even if the respective permanent magnet groups are shifted from each other in the circumferential direction. However, the disturbance of the magnetic flux caused by the magnet ends constituting each permanent magnet group cannot be ignored.

[0015]

In order to solve this problem, four or more permanent magnet groups are provided to reduce the angle of misalignment (step skew angle) between adjacent permanent magnet groups, and to reduce the number of permanent magnet groups. It is conceivable to reduce the disturbance of the magnetic flux caused by the ends of the constituent magnets. However, there is a problem that the manufacturing cost increases because the number of magnets used increases. Further, in the case of a small motor, the length of the rotor yoke is limited, so that fine processing of the magnets constituting the permanent magnet group is required, and there is a problem that the production cost rises.

[0016]

SUMMARY OF THE INVENTION Therefore, the present invention reduces the disturbance of the magnetic flux between the stator and the permanent magnet even when the number of the permanent magnet groups provided on the rotor yoke is two or three. The purpose of the present invention is to suppress the fluctuation of torque during operation.

[0017]

According to one embodiment of the present invention, there is provided a permanent magnet synchronous motor having a stator and a rotor provided through a space inside the stator; Has a plurality of magnetic plates laminated in the axial direction of the rotor; the rotor has at least two magnetic plates arranged around a rotor yoke provided in the axial direction and spaced in the axial direction. A set of permanent magnets, each of the two sets of permanent magnets having a plurality of permanent magnets magnetized radially of the axis;
The two sets of permanent magnets are radial air gap type permanent magnet synchronous motors provided at a predetermined angle from each other on the yoke; and the first and second magnetic plates among the plurality of magnetic plates. The magnetic plate corresponding to the gap between the permanent magnet groups is replaced with a non-magnetic plate.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
An embodiment will be described. 4 to 6 used in the description of the conventional example will be referred to as needed.

As described above, in the conventional permanent magnet motor shown in FIGS. 4 to 6, two sets of permanent magnets 30 and 32 are provided at intervals D in the axial direction of the rotor shaft 10. ,
They are arranged so as to be shifted by a step skew angle θ in the circumferential direction of the shaft 10. However, since the step skew angle θ is large in the two permanent magnet groups, it is difficult to sufficiently compensate for the change in the magnetic flux density at the end of each magnet 14 in each of the permanent magnet groups 30 and 32. .

For this reason, the first embodiment according to the present invention, as shown in FIG. 1, uses a permanent magnet group 30 (see FIG. 5) of a laminated magnetic thin plate of a conventional stator 18. And 3
The magnetic thin plate corresponding to the gap between the two (see FIG. 6) is replaced with a non-magnetic plate 40. Other configurations of the motor are the same as those of the related art.

The non-magnetic plate 40 is manufactured using, for example, aluminum, copper, non-magnetic stainless steel, paper, bakelite, wood or the like. The thickness of the nonmagnetic plate 40 is shown in FIG.
Or the same as the length D of the permanent magnet group 30 and the gap 34
A slightly larger value is used.

As described above, by replacing the magnetic plate at the portion corresponding to the gap 34 between the permanent magnet groups 30 and 32 (see FIG. 6) with the non-magnetic plate 40,
Most of the magnetic flux emitted from the magnetic plate 40 (see FIG. 6) enters a plurality of magnetic plates located above the non-magnetic plate 40 (on the drawing), and most of the magnetic flux entering the permanent magnet group 30 is located above the magnetic plate 40 (see FIG. (On the drawing). Similarly, most of the magnetic flux of the magnetic flux emitted from the permanent magnet group 32 enters a plurality of magnetic plates located below the nonmagnetic plate 40 (on the drawing), and most of the magnetic flux of the magnetic flux entering the permanent magnet group 32 is non-magnetic. The magnetic flux is emitted from a plurality of magnetic plates located below the magnetic plate 40 (on the drawing). Since the gap between the stator and the rotor is very narrow, the above phenomenon can be obtained. Therefore, it is possible to prevent the magnetic flux from being disturbed due to the end portions of the permanent magnets constituting each of the permanent magnets 30 and 32.

In the conventional example, the torque fluctuation cannot be ignored even when three permanent magnet groups are used. However, the present invention eliminates the above-mentioned "flux disturbance" when three permanent magnet groups are used. It turns out that it can control more effectively.

In the second embodiment of the present invention, as shown in FIG. 2, a portion of the nonmagnetic plate 40 provided on the stator 18 on the rotor side is removed to form a gap 44, and It aims at the same effect as the embodiment.

In the third embodiment of the present invention, as shown in FIG. 3, a portion of the nonmagnetic plate 40 provided on the stator 18 on the rotor side is removed to form a gap 44. This is the same as the second embodiment. However, unlike the first or second embodiment, the tip of the teeth 22 of the stator 18 is
To respond to. The reason is that the permanent magnet group 3
The magnetic flux exiting from zero is facilitated to enter a plurality of magnetic plates located above the nonmagnetic plate 40 (on the drawing), and the magnetic flux entering the permanent magnet group 30 is placed above the nonmagnetic plate 40 (on the drawing). This is because the magnetic flux is emitted from the plurality of magnetic plates located.
Similarly, the magnetic flux emitted from the permanent magnet group 32 is
The magnetic flux entering the permanent magnet group 32 is made easy to enter a plurality of magnetic plates located below (on the drawing)
This is because the magnetic flux is emitted from a plurality of magnetic plates located below (on the drawing).

The results of experiments conducted by the inventor of the present invention on the present invention and the conventional example will be described below. The experiment was performed using Nd-
Although the test was performed with an Fe-B-based permanent magnet, the present invention is not limited to such a permanent magnet.

The permanent magnet was manufactured in the following steps. Purity 9
9.7% by weight of Nd, Fe, Co, M (M is Al, S
i, Cu) and B having a purity of 99.5% by weight were melt-cast in a vacuum melting furnace to produce an ingot. Next, the ingot was coarsely pulverized with a jaw crusher, and further jet milled in a nitrogen stream to obtain an average particle size of 3.5 μm.
Was obtained. This powder was subjected to 12
Molding was performed at a molding pressure of 1.0 t / cm ² in a magnetic field of kG. This molded body was sintered at 1090 ° C. for 1 hour in Ar gas, and subsequently heat-treated at 580 ° C. for 1 hour.
Thereafter, grinding was performed with a grindstone to obtain a permanent magnet. As a characteristic of the permanent magnet, Br (residual magnetic flux density) is 13.
0 kG, iHc is 15 kOe, bHc is 12.4 kOe
And (BH) _max was 40 MGOe.

In the experiments, the conventional synchronous motor using the permanent magnet described above (FIGS. 5 and 6) and the synchronous motor according to the first embodiment of the present invention using the permanent magnet described above (FIGS. 5 and 6) were used. Using a nonmagnetic plate 40 corresponding to FIG. 6), the cogging torque and the induced voltage generated between the wires of the three-phase winding (see FIG. 4) were measured. The rated torque of the conventional motor used this time is 0.63 Nm / 3000 rpm
Met.

The cogging torque is the difference between the maximum value and the minimum value of the pulsating torque. In this experiment, a torque detector was connected to one end of the rotating shaft 10 of the motor, and the cogging torque was measured by rotating the separately prepared motor at the other end of the rotating shaft 10 at a low speed of 10 rpm or less. I asked. On the other hand, the induced voltage was measured by rotating a motor connected to the other end of the shaft 10 at 1000 rpm.

The gap between the rotor 16 and the stator 18 (air
The gap (see FIG. 4) is 0.7 mm, and the permanent magnet group 30
And 32 have a length of 15 mm in the direction of the rotation axis 10,
The length D of the gap 34 between the permanent magnet groups 30 and 32 is 3 mm,
The step skew angle is 5 ^° , the interval between the adjacent magnets of each of the permanent magnet groups 30 and 32 is 1.5 mm, the height of the center and the end of each magnet (C type magnet) is 3 mm and 2 mm, respectively.
The thickness of the non-magnetic material was 3 mm.

As a result of the experiment, the following values were obtained. First Embodiment of the Present Invention (a) Cogging torque (Nm): 0.003 (b) Induced voltage (mV (effective value) / rpm):
54 Conventional Example (a) Cogging torque (Nm): 0.016 (b) Induced voltage (mV (effective value) / rpm):
65

As described above, the cogging torque is the difference between the maximum value and the minimum value of the pulsating torque. In a high-accuracy control permanent magnet synchronous motor, the target value is 1% or less of the rated torque. Rated torque is 0.63Nm / 3000rpm
Therefore, the target value is 0.006 Nm, and it can be seen from the experimental results that the cogging torque (torque fluctuation) of the motor according to the present invention is the target value, but has not reached the target value in the related art. Furthermore, it can be said that the induced voltage of the motor to which the present invention is applied is substantially the same as that of the conventional motor and there is no problem.

[0033]

As described above, according to the present invention,
A simple improvement of the stator can greatly reduce torque fluctuations.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment according to the present invention.

FIG. 2 is a diagram illustrating a second embodiment according to the present invention.

FIG. 3 is a diagram illustrating a third embodiment according to the present invention.

FIG. 4 is a view for explaining a conventional permanent magnet synchronous motor.

FIG. 5 is a view for explaining a stator of a conventional permanent magnet synchronous motor.

FIG. 6 is a view for explaining a rotor related to both the present invention and a conventional permanent magnet synchronous motor.

[Explanation of symbols]

 10: Rotor shaft 12: Rotor yoke 14: Permanent magnet 16: Rotor 18: Stator 20: Stator yoke 22: Stator teeth (teeth) 24: Slot provided in the stator 26: Magnetic material Thin plate 30, 32: Permanent magnet group 34: Spacing between permanent magnet groups 40, 40 ': Non-magnetic thin plate 44: Space (gap) provided on the rotor side of non-magnetic thin plate

Claims (3)

[Claims] 1. A stator having a stator and a rotor provided inside the stator via a space, wherein the stator has a plurality of magnetic plates laminated in the axial direction of the rotor. At least two rotors are arranged around a rotor yoke provided in the axial direction and spaced apart in the axial direction.
A plurality of permanent magnet groups, each of the two permanent magnet groups having a plurality of permanent magnets magnetized in a radial direction of the axis, wherein the two permanent magnet groups are mutually fixed on the yoke. In the radial air gap type permanent magnet synchronous motor provided at an angle, the magnetic material corresponding to the gap between the first and second permanent magnet groups among the plurality of magnetic material plates of the stator. A permanent magnet synchronous motor characterized in that the plate is replaced by a non-magnetic plate. 2. The permanent magnet synchronous motor according to claim 1, wherein an end of said non-magnetic plate on said stator side is removed to form a gap. 3. The stator has a plurality of teeth extending in a radial direction with respect to the axis of the rotor, and the shape of the tips of the teeth is as follows.
The permanent magnet synchronous motor according to claim 2, wherein an end of the nonmagnetic plate on the stator side is removed to correspond to a gap provided.