JPS63314155A - Brushless motor - Google Patents

Abstract

PURPOSE:To reduce a torque ripple by forming irregular shapes in positions of a protective cover opposed to an index magnet. CONSTITUTION:In positions of a cover 6 opposed to the locus of rotation of an index magnet 3, a plurality of protrusions 6a are provided at given spaces over the whole periphery. In this case, an apparatus is so constituted that an attraction force is generated between the protrusions 6a provided in said cover 6 and the index magnet 3 in accordance with the timing for a generated torque to be minimized. Then, when a motor is rotated, there appears a torque wave with 12 periods per rotation. However, it is possible to contrive to raise the bottom of the valley portion of a torque waveform by an upper attraction force. Therefore, a minimum starting torque value can be put up and a torque ripple can be reduced to improve the performance of said motor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a brushless motor mainly used for computer-related motors, etc., and is particularly aimed at increasing the minimum starting torque and reducing torque ripple. It is something.

Conventional Technology Conventionally, in order to increase the minimum starting torque and reduce torque ripple, measures have been taken by changing the number of windings, current, etc., and by modifying the core shape.

A conventional brushless motor will be described below with reference to the drawings.

FIG. 3 is a side sectional view of a conventional brushless motor, and FIG. 4 is a plan sectional view. A core 1 having an armature coil 10 wound thereon is fixed to a pace 7, and a shaft 8 is supported inside the base 7 via a bearing 9, making it rotatable. Further, a rotor yoke 6 is press-fitted into the lower part of the shaft 8, and has a main magnet 2 at a position facing the core 1, and has one index magnet 3 for an index signal on the outer circumferential side. Further, a Hall IC 4 is disposed as a magnetic flux detection element at a position facing the index magnet 3, and is configured to obtain an index signal indicating the rotational phase of the rotor yoke 6. Further, a protective cover 8 made of a magnetic material is provided between the rotor yoke 6 and the Hall IC for motor protection and magnetic shielding.
It is arranged to cover 4.

Problems to be Solved by the Invention In such a brushless motor, peaks and valleys (torque ripples) occur at regular intervals in the torque waveform due to the number of poles of the main magnet 2, the number of balls in the core, etc. as shown in Figure 5. The structure is such that In addition, motor torque is generally referred to as minimum starting torque, and since its magnitude is evaluated as superior or inferior, it is desirable to reduce torque ripple.

The present invention provides a brushless motor in which such structurally generated torque ripple can be improved by devising the shape of the cover.

Means for Solving the Problems In order to achieve this object, the brushless motor of the present invention has an uneven shape formed on the protective cover at a position facing the index magnet.

Effect: According to this configuration, the magnetic attractive force between the index magnet and the cover changes periodically due to the uneven shape, so the above-mentioned torque ripple is reduced by utilizing this periodic change in the attractive force. It is something that can be done.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a plan sectional view of a brushless motor in an embodiment of the present invention. 1 is a core around which the armature coil 10 is wound, 2 is a main magnet magnetized into 4 poles,
5 is a rotor yoke, 3 is an index magnet, and 4 is a cover made of a magnetic material for the Hall IC 16, and the main configurations thereof are the same as the conventional configuration, and the explanation thereof will be omitted.

The difference from the conventional structure is that a plurality of protrusions 6a are provided at predetermined intervals around the entire circumference of the cover 6 at positions facing the rotation locus of the index magnet 30.

The brushless motor of this embodiment configured as above will be explained. As can be seen in the conventional example shown in FIG. 6, a torque wave of 12 cycles appears per revolution, and it can be seen that the minimum starting torque also appears every 30 degrees.

The present embodiment is configured such that an attractive force is generated between the protrusion 6a provided on the cover 6 and the index magnet 3 at the timing when the index magnet 3 becomes the minimum.

As described above, according to this embodiment, as shown in FIG. 2, it is possible to raise the valley part of the torque waveform, increase the minimum starting torque and reduce torque ripple, and use the index magnet 3 for the purpose of the index signal. As well,
It has a structure that can be effectively utilized in terms of torque.

Note that FIGS. 1 and 2 described in this embodiment are examples to which the present invention can be applied, and the shape of the protrusions, the number of protrusions, the distance from the index magnet, etc. are not limited thereto.

Effects of the Invention As described above, the present invention effectively utilizes the index magnet, which is originally used to obtain index signals, and the cover, which is provided for the purpose of protecting the inside, in terms of motor torque by devising the shape of the cover. It must be possible to
In particular, without adding any new parts, torque ripple can be reduced, minimum starting torque can be increased, and motor performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a plan sectional view of a brushless motor in an embodiment of the present invention, and FIG. 2 is a torque waveform diagram in the same embodiment.
FIG. 3 is a side sectional view of a conventional brushless motor, FIG. 4 is a sectional view of the same, and FIG. 6 is a torque waveform diagram of the conventional example. 1... Core, 2... Main magnet, 3... Index magnet, 4...
... Hall IC, s ... Rotor yoke, 6 ...
...Cover, 6a...River/cover inner protrusion. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
-Core 2-11 Main Magetei Volume 3--Fn7--Z-S7-G Imogai C--Cover Fig. 2 5vA Nine Seas

Claims (1)

[Claims] An index signal magnet is disposed on the outer periphery of the rotor yoke, and an index signal indicating the rotational phase of the rotor yoke is obtained from a magnetic flux detection element disposed opposite to the magnet. 1. A brushless motor, comprising: a cover made of a magnetic material; and a plurality of protrusions provided on the cover at positions facing the rotation locus of the magnet.