JPS5947958A - Brushless motor - Google Patents

Abstract

PURPOSE:To improve the torque ripple of a brushless motor by providing one set of two magnetic units in a stator, disposing the units at the optimum positions, and cancelling the drop of the torque produced at a drive coil by cogging produced at the units. CONSTITUTION:Plate magnetic units 10A, 10B are respectively provided in a stator corresponding to the phases of drive coil. The unit 10A corresponding to phase A is disposed at the position of an electric angle 9/9pi in the rotating direction of a drive magnet 3 clockwise from the center l of the drive coil A1, and the unit 10B corresponding to phase B is disposed at the position of an electric angle 13/8 clockwise from the center l of the drive coil 4A1. The width of the unit in circumferential direction is pi/8 of an electric angle. Thus, the drop of the torque produced by the drive coil can be cancelled by cogging produced by the unit which is disposed in a stator, thereby reducing the torque ripple.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a two-phase full-wave or four-phase half-wave brushless motor with improved torque ripple.

(Construction of conventional example and its problems) FIG. 1 is a sectional view of a conventional brushless motor. The rotor portion (1) includes a rotating shaft l, a ring-shaped drive magnet 3 magnetized in the direction of the rotating shaft, a disc-shaped rotor yoke 2 that constitutes a magnetic circuit of the driving magnet 3, and a rotating shaft 1.
and a rotor knife 8 for fixing the rotor yoke 2. The stator unit (U) includes a drive coil 4 that is arranged to face the magnetic pole surface of the drive magnet 3 with a gap g interposed therebetween, a substrate 5 that fixes the drive coil 4, and a stator yoke 6 that constitutes a magnetic circuit. A bearing 7 that rotatably supports the rotating shaft 1 of the rotor portion (I), and a driving magnet.

and a magnetically sensitive element 9 for detecting the rotational position of the seat 3.

FIG. 2 is a plan view of a conventional example of a stator section (III) in a two-phase full-wave drive force type having an S-pole magnetized drive magnet 3, in which the drive coil 4 has two phases (human phase and B phase). 1.4 A2 and 4B1 for drive coil 4.

It consists of 4B2, and the A-phase and B-phase drive coils are electric or
Drive coils for each phase 4AI, 4A2 and 4B, 4
B2 are connected in series and arranged with a phase difference of 4π which is an integral multiple of 2π in electrical angle.

Further, the opening angle of each drive coil is π in electrical angle.

In the conventional motor described above, the drive coil 4A1゜41
2.481 + 4If a constant current is applied to B2 by switching electrical angles at a predetermined timing, (a) in Fig. 3 is obtained.
), the torque is not constant, and a drop D in torque occurs near the point of current switching, which leads to an increase in drooling and pull, which causes uneven rotation.

(Objective of the Invention) Therefore, the present invention provides a brushless motor that improves the drawbacks of the conventional example and reduces torque ripple.

According to the present invention, one set of two magnetic bodies is placed in the stator portion.
By providing a set or multiple sets and arranging these magnetic bodies optimally, the drop in torque generated by the drive coil is offset by the cogging generated by the magnetic body, and as a result, the torque ripple is reduced. It is something.

Hereinafter, embodiments will be described in detail with reference to the drawings.

(Explanation of Embodiment) FIGS. 4 and 5 show an embodiment of the present invention, and the same parts as in FIGS. 1 and 2 are given the same reference numerals, and the explanation thereof will be omitted. . IOA and 10E are plate-shaped magnetic bodies respectively provided in the stator portion corresponding to each phase (A phase and B phase) of the drive coil. The magnetic body 10A corresponding to the A phase is moved clockwise from the center t of the drive coil 4Al (the magnetic body 10B corresponding to the B phase is the drive coil 4A).

each is placed. Note that the width of each magnetic body in the circumferential direction was expressed as T in electrical angle.

When this embodiment configured as described above is operated, cogging torque is generated by the magnetic bodies 10A and IOB, as shown in FIG. That is, the cogging generated by the magnetic body 10A has a peak near the switching point between the N pole and the S pole of the magnetic field, so the cogging generated by the magnetic body 10B is as shown by the dotted line R1, and the cogging generated by the magnetic body 10B is the cogging R1 due to the magnetic body 10AK.
Since there is a phase difference of 1/2 in electrical angle, the result is as shown by the dashed dotted line R2. Therefore, two magnetic bodies 10A, IOH
The resultant cogging generated by is shown by the solid line R.

Now, drive coils 4 Al', 4A2 and 4B1.

The torque ripple generated by 4B2 is shown in (a) in Figure 3.
), and on the other hand, the magnetic material L OA
, 10B as shown in Figure 3(b) (5
) When cogging torque is generated, (a) and (b) are combined to form an improved torque ripple as shown in (c) of Fig. 3. That is, in the present invention, the magnetic body 10A is arranged so that the peak of cogging torque occurs at the position of the drop in the torque generated by the drive coil.

10B, therefore, the magnetic body 10A.

The cogging generated by 10B is caused by the drive coil 4-A.
The effect is that the torque drop caused by l l 4A2 * 4B1 + 4B2 is offset, and the torque ripple is greatly improved.

If the required magnitude of cogging torque cannot be obtained with the two magnetic bodies 10A and IOB, the magnetic body 10A.

A plurality of sets of magnetic bodies can be arranged in the stator portion, with 10B as one set. Here, drive magnet 3 with S pole magnetization
Taking as an example the case of a two-phase all-heavy system, as shown in FIG.
A8 is at a position T+nπ (n is 1, 2...8) in electrical angle from the center l of an arbitrary drive coil, for example 4A, in the clockwise direction (rotation direction of the rotor part R) as a reference, and B The magnetic bodies 10B1 to 10B$ belonging to group (6) are respectively arranged at positions of ¥10·π in electrical angle clockwise from the center l. Therefore, each set of magnetic material, ie (10A+).

10B+ ), (10A2.10B2 )...(10A
Since the cogging generated by each of a and l0B8 coincides with R in FIG. 6, the combined cogging of eight sets of magnetic materials has an amplitude eight times that of one set and a waveform with the same phase. Therefore, the number of pairs of magnetic bodies can be freely selected in order to generate the necessary cogging.

FIG. 7 shows another embodiment of the present invention, in which a plurality of holes 11 are provided in a substrate 5 to which a drive coil 4 is fixed, and a magnetic body 10 is mounted in the holes.

In this way, the magnetic bodies can be arranged as shown in FIG. 8 without being affected by the position of the drive coil 4 at all.

It is clear that the present invention (ri) can also be applied to drive magnets with different numbers of poles.

(Effects of the Invention) As explained above, according to the present invention, torque ripple is greatly improved because the drop in torque generated by the drive coil is offset by the cogging generated by the magnetic material disposed in the stator section. Significant effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional example of a brushless motor, FIG. 2 is a plan view of the stator section, and FIG. 3 is a relationship between torque ripple caused by the drive coil and cogging caused by the magnetic material.
FIG. 4 is a sectional view of an embodiment of the present invention, FIG. 5 is a plan view of the stator section of the same embodiment, FIG. 6 is a diagram showing cogging waveforms, and FIG. 7 is a diagram illustrating an embodiment of the invention. 8th cross-sectional view of the embodiment of
The figure is a plan view showing the general arrangement of magnetic bodies according to the present invention. 1... Rotating shaft, 2... Rotor yoke, 3... Drive magnet, 4 (4A1 .4A2 .4B1 r 4
B2)... Drive coil, 5... Board, 6...
Stator yoke, 10 (10A, 10A1~10Ag
, 10B, 10B1-l0B8)...Magnetic material. Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) A two-phase full-wave or four-phase rotor having a rotor section having a drive magnet and a rotor yoke, and a stator section having a plurality of drive coils and stator yokes arranged opposite to the magnetic pole surface of the drive magnet with an air gap interposed therebetween. In the half-wave brushless motor, the stator section is provided with one or more sets of magnetic stubs each consisting of two first and second magnetic bodies, and when n is an arbitrary integer and i-, the magnetic stubs are Each of the first magnetic bodies is disposed at a position of electrical angle +nπ clockwise (rotation direction of the rotor) from the center of any one of the drive coils as a reference, and each of the first magnetic bodies of the magnetic A brushless motor characterized in that the second magnetic bodies are respectively arranged at positions s 10nπ in electrical angle in the hourly 5π hand direction from the center. (2) The circumferential width α of the magnetic body is 0〈α〈 in electrical angle.
The brushless motor according to claim (1), wherein the brushless motor is T. (3) The brushless motor according to claim (1), wherein the magnetic body is installed in a hole provided in a substrate that holds the drive coil.