JPH06105490A - Rotor for revolving field type motor - Google Patents

Abstract

PURPOSE:To reduce cogging toque by setting the shape of a pawl within predetermined range. CONSTITUTION:The ratio theta/omega of a spreading angle omega[rad] per one pole of a rotor 20 in which 2pi [rad] is divided by the number P of poles (e.g. P=8) to spreading angle theta [rad] formed between linear ends of an end 26d connected from a rotary axial center 24a is set in a range of theta/omega=0.25-0.45. Further, the ratio r/R of the radius R[mm] of a pole board 22 to the radius (r) [mm] of curvature of an outer periphery (shoulder) 26f adjacent to a side 26b of a pawl 26 is set in a range of r/R=0.60-0.85. Thus, cogging torque can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary field type electric motor used for positioning control of a servomotor or the like, and in particular, it has a permanent magnet and a pair of magnetic pole plates sandwiching the permanent magnet.
The present invention relates to low cogging of a rotor of a rotary field type electric motor in which a plurality of claw portions are formed on a magnetic pole board.

[0002]

2. Description of the Related Art Generally, when a rotating field type electric motor, for example, a servomotor is rotated at a constant speed and stopped at a fixed position, it is necessary to reduce the cogging torque in order to improve the accuracy of the servo system at the rotating and stopping positions. Conventionally, as a rotor of a rotary field type motor, (a) and (b) of FIG.
As shown in [XX sectional view of (a)], both magnetic pole faces 11a and 11b of the annular permanent magnet 11 magnetized in the axial direction.
In addition, N poles and S poles are alternately arranged along the outer peripheral surface of the permanent magnet, and as shown in FIG. 2C (side schematic view of rotor of conventional rotary field type motor). A so-called claw pole in which a pair of disc-shaped magnetic pole disks 12 having a plurality of claw portions 12a whose outer peripheral portions are formed in a rectangular shape is sandwiched, and a rotary shaft 14 is provided at the rotary shaft centers of the permanent magnet 11 and the magnetic pole disk 12. Rotating rotors are known.

By the way, the claw pole type rotor in the rotating field type motor has a drawback that the cogging torque is larger than that of the permanent magnet type rotor in which the NSNS pole is directly formed on the peripheral surface of the permanent magnet. . This is because the plurality of claws are made of a magnetic material such as iron, so that the magnetic flux concentrates only on the claws facing the teeth of the stator. Further, since the outer periphery of the claw portion of the conventional claw pole type rotor is rectangular, when the rotor rotates, the magnetic flux from the claw portion side toward the teeth of the stator is abruptly generated between the adjacent claw portions. It is because it changes to.

[0004]

SUMMARY OF THE INVENTION In consideration of the above facts, an object of the present invention is to provide a rotor of a rotating field type motor having a low cogging torque.

[0005]

In order to solve the above-mentioned drawbacks, the present invention is directed to an axially magnetized annular permanent magnet and a pair of permanent magnets fixed so as to sandwich both magnetic pole surfaces. Disk-shaped magnetic pole disk, a plurality of claw portions in which N poles and S poles are alternately arranged from the outer peripheral end of the magnetic pole disk to the outer peripheral portion along the outer peripheral surface of the permanent magnet, the permanent magnet and the magnetic pole. In a rotor of a rotating field type electric motor having a rotary shaft provided at a rotary shaft center of a board, the claw portion is adjacent to the bent portion and the bent portion facing the magnetic pole board, and , A pair of side surface portions facing each other, a pair of inclined portions extending from each side surface portion in a direction toward the center of the claw portion, and a tip portion which is an end surface formed by connecting the respective inclined portions. And a substantially trapezoidal shape including, and connecting each of the ends of the tip portion from the rotation axis. A tip spread angle defined by a spread angle formed by a straight line is θ [rad], and 2π [rad] is divided by the number of poles corresponding to the number of the claws, so that the rotor is defined by a spread angle. Is ω [rad], the radius of the magnetic pole plate is R [mm], and the bending radius of the shoulder portion adjacent to the side surface portion of the outer peripheral portion of the claw portion is r.
[Mm], θ / ω = 0.25 to 0.45, r
It is characterized in that it is set within a range of /R=0.65 to 0.85.

[0006]

According to the above construction, the rotor of the rotating field type electric motor of the present invention has the permanent magnet magnetized in the axial direction and the rotary shaft center of the pair of magnetic pole plates sandwiching both magnetic pole surfaces of the permanent magnet. A rotating shaft is provided and is formed on the outer peripheral end of the magnetic pole plate.
A bent portion, a side surface portion, an inclined portion, and a tip portion are present in the plurality of claw portions in which the south poles are alternately configured, and the outer peripheral portion of the claw portion is formed in a substantially trapezoidal shape. Therefore, compared to the conventional rotor of the rotary field type electric motor in which the claws are rectangular, the magnetic flux from the claws to the teeth of the stator does not change rapidly between the adjacent claws.

According to an experiment by the present inventor, the spread angle per pole defined by the spread angle obtained by dividing 2π [rad] by the number of poles corresponding to the number of claws is ω [rad], The tip end divergence angle defined by the divergence angle formed by the straight lines connecting the rotation axis and both ends of the tip of the claw is θ [r
ad], the ratio θ / ω and the cogging torque T have a relationship as shown in the graph of FIG. 3A, and two critical points G1 and G2 may exist. found. Therefore, by setting the ratio θ / ω within the range of 0.25 to 0.45, it is possible to obtain the rotor of the rotating field type motor having a low cogging torque. This ratio θ /
The smaller the ω, the closer the trapezoidal claw part is to a triangle, and the area of the outer peripheral part of the claw part (the area facing the teeth of the stator).
Becomes smaller.

Further, when the radius of the magnetic pole plate is R and the bending radius of the outer peripheral portion (shoulder portion) adjacent to the side surface of the claw portion is r, the ratio r / R and the cogging torque T are , Fig. 3
It has been found that there is a relationship as shown in the graph of (b) and there are two critical points H1 and H2. Therefore, by setting the ratio r / R within the range of 0.65 to 0.85, the rotor of the rotating field type electric motor having a low cogging torque can be obtained. The ratio r / R represents the degree of shoulder lowering of the outer peripheral portion (shoulder) of the claw portion, and the ratio r / R
Is smaller, the degree of shoulder drop is larger and the air gap between the rotor and the stator is increased.

[0009]

As described above, according to the present invention, the cogging torque can be reduced by setting the shape of the claw portion within a predetermined range, so that the accuracy of the servo system at the rotation and stop positions is improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the rotor of the rotating field type electric motor of the present invention will be described with reference to the drawings.

A front view of an embodiment relating to the rotor of the rotating field type electric motor of the present invention is shown in FIG. A sectional view taken along the line YY shown in FIG. 1A is shown in FIG.

The rotor 20 of the rotary field type motor in the embodiment of the present invention is a claw pole type rotor, and has both magnetic pole faces 21a of an annular permanent magnet 21 magnetized in the axial direction.
21b, a pair of iron disk-shaped magnetic pole disks 22 are fixed,
The permanent magnet 21 is sandwiched between the two magnetic pole disks 22, and the rotation axis 24a of the permanent magnet 21 and the two magnetic pole disks 22 is set.
The rotary shaft 24 is inserted therethrough. Both poles 22
A plurality of iron claw portions 26 are integrally formed with the magnetic pole disk 22 in the axial direction so that the N poles and the S poles are alternately arranged along the outer peripheral surface of the permanent magnet 21 at the respective outer peripheral ends. It is formed in a bent state.

The rotor 20 of the rotary field type electric motor according to the embodiment of the present invention has eight claws, which are the N pole and the S pole.
Therefore, the number P of poles corresponding to the number of claws is eight.

As shown in FIG. 1C (a schematic side view for explaining the shape of the claw portion 26), the claw portion 26 is adjacent to the bent portion 26a facing the magnetic pole plate 22 and the bent portion 26a. And a pair of side surfaces 26b facing each other, a pair of slopes 26c extending from the side surfaces 26b in the direction of the center of the claw, and the slopes 26c. The outer peripheral surface 26e of the claw portion 26 has a substantially trapezoidal shape.

In the embodiment of the present invention, the number of poles P is
(P = 8) Divide 2π [rad] by 2 to divide the divergence angle ω [rad] per one pole of the rotor 20 from the rotation axis 24a to both ends of the tip portion 26d, and form a tip portion formed by each straight line. The ratio θ / ω with the spread angle θ [rad] is calculated between the two critical points G1 and G2 shown in FIG.
It is set to an intermediate value (θ / ω = 0.35) of 0.25 to 0.45). Further, the radius R [mm] of the magnetic pole board 22 and the outer peripheral portion (shoulder portion) 26f adjacent to the side surface portion 26b of the claw portion 26.
The ratio r / R to the bending radius r [mm] between the two critical points H1 and H2 shown in FIG. 3 (b) (r / R = 0.60).
.About.0.85) (r / R = 0.73).

The cogging torque T on the vertical axis shown in FIGS. 3A and 3B is measured by a cogging torque detector (not shown) which is connected to the rotary shaft 24 and is rotated together with the rotary shaft 24. And between the critical points G1 and G2 (θ / ω
= 0.25 to 0.45) and between the critical points H1 and H2 (r
/R=0.60 to 0.85), it is proved that the value of the cogging torque T is extremely small.

The inventor further conducted the following experiment with the rotor of the rotating field type electric motor of the embodiment of the present invention having the above-mentioned structure.

In this experiment, as shown in FIG. 4A, the outer peripheral surface 26e of the substantially trapezoidal claw portion 26 is parallel to the parallel lines A1 and B at equal intervals along the rotation direction of the rotor 20.
1, C1, D1, and E1 are divided into regions, and the rotor 2
The magnetic flux density distribution B on each parallel line at the time of 0 rotation is measured by a Gauss meter, and the result is shown in FIG. 4 (b). In FIG. 4B, the waveform diagram (A
2) to (E2) are parallel lines A1 divided into respective regions.
~ E1 represents the magnetic flux density distribution B, and waveform chart (F) represents the composite magnetic flux density distribution in waveform charts (A2) to (E2). As is clear from the waveform diagram (F), in the rotor of the rotating field type electric motor of the present embodiment, in the combined magnetic flux density distribution of the claw portion 26, the sine wave disturbance causing the cogging torque is seen. However, it is proved that the cogging torque is reduced because it draws a smooth sine wave.

In the embodiment of the present invention, the ratio θ / ω and the ratio r / R value are set to intermediate values between the critical points G1 and G2 and between the critical points H1 and H2, respectively, but not limited to this. , Ratio θ / ω and ratio r / R are the critical points G1,
Any value is effective as long as it is within the range between G2 and the critical points H1 and H2.

As another embodiment, as shown in FIG. 5, when the portion connecting the pair of inclined portions 26c of the claw portion 26 and both ends of the tip end portion 26d has a curvature, the tip end spread angle θ [ rad] is the tangent line K1, K2 of both the inclined portions 26c.
Is the angle formed by the respective straight lines connecting the two points Q and Q'where the tangent line L of the tip portion 26d intersects with the rotation axis 24a.

[Brief description of drawings]

FIG. 1 shows an embodiment relating to a rotor of a rotating field type electric motor of the present invention, (a) is a front view of the rotor, (b) is a sectional view taken along line YY of (a), FIG. 7C is a schematic side view illustrating the shape of the claw portion.

FIG. 2 shows a rotor of a conventional rotary field type motor,
(A) is a front view of a rotor, (b) is sectional drawing which follows the XX line of (a), (c) is a side surface schematic diagram explaining the shape of a claw part.

FIG. 3 is a graph illustrating the basis of the present invention, (a)
Is a graph showing the relationship between the ratio θ / ω and the cogging torque T, and (b) is a graph showing the relationship between the ratio r / R and the cogging torque T.

FIG. 4 (a) is an explanatory view in which the outer peripheral surface of the claw portion of the above-described embodiment is divided into regions by parallel lines, and FIG. 4 (b) is
It is a wave form diagram showing magnetic flux density distribution B on each parallel line of (a).

FIG. 5 is an explanatory diagram showing a tip end spread angle θ of a claw portion having a curvature in a rotor according to another embodiment.

[Explanation of symbols]

 20 rotor 21 permanent magnet 22 magnetic pole disk 24 rotary shaft 24a rotary shaft center 26 claw portion 26a bent portion 26b side surface portion 26c inclined portion 26d tip portion 26e outer peripheral surface 26f outer peripheral portion (shoulder portion) θ tip end spread angle ω rotor Spread angle per pole R radius of pole plate r bending radius

Claims (1)

[Claims] 1. An axially magnetized annular permanent magnet, a pair of disc-shaped magnetic pole plates fixed so as to sandwich both magnetic pole surfaces of the permanent magnet, and an outer peripheral end of the magnetic pole plate. Rotation including a plurality of claw portions having N poles and S poles alternately arranged on an outer peripheral portion along the outer peripheral surface of the permanent magnet, and a rotating shaft provided on a rotating shaft center of the permanent magnet and the magnetic pole plate. In the rotor of the magnetic field type motor, the claw portion includes a bent portion that faces the magnetic pole board, a pair of side surface portions that are adjacent to the bent portion and that face each other, and the side surfaces from the side surface portion. It is a substantially trapezoidal shape that includes a pair of inclined portions that extend obliquely toward the center of the claw portion and a tip portion that is an end surface formed by connecting the respective inclined portions, The tip divergence angle defined by the divergence angle formed by each straight line connecting both ends is θ
[Rad] and the number of poles corresponding to the number of the claw portions is 2π
The divergence angle per one pole of the rotor defined by the divergence angle divided by [rad] is ω [rad], the radius of the magnetic pole plate is R [mm], and the outer peripheral portion of the claw portion is The bending radius of the shoulder portion adjacent to the side portion is r
[Mm] is set in the range of θ / ω = 0.25 to 0.45 r / R = 0.60 to 0.85. .