JPH0145252Y2 - - Google Patents

Description

[Detailed explanation of the idea] (b) Industrial application fields The present invention relates to improvements in brushless motors.

(B) Prior Art As shown in FIG. 1, a conventional brushless motor has a magnetic shield plate 3 arranged on a printed circuit board 2 having a bearing part 1, and a coil attached to a winding core 4 supported by the bearing part 1. 5 and a ring-shaped magnet 7 is attached to the rotor yoke 6. The rotating shaft 9 of the rotor 8 is pivotally supported by the bearing part 1, and as shown in FIGS. It has a structure in which a plurality of through holes 10 are formed at positions facing the rotor 7 , and a Hall element 11 as a position detection sensor of the rotor 8 is arranged in each of the through holes 10 .

In the brushless motor configured in this way, the lead pin 12 of the Hall element 11
is connected to the printed circuit board 2 by soldering, and the Hall element main body 1 is connected in the through hole 10.
3 is housed in a tilted manner so that the Hall element 11 does not protrude too much from the relatively thin magnetic shielding plate 3, thereby making the brushless motor thinner.

However, in such a brushless motor, since the magnetic shield plate 3 is arranged between the printed circuit board 2 and the coil 5, etc., leakage of magnetic flux from the coil 5 can be prevented to some extent;
A plurality of through holes 10 for arranging the Hall elements 11 are formed in the magnetic shielding plate 3, and the through holes 10 having a large diameter are formed because the Hall elements 11 are arranged upside down.

Therefore, the magnetic flux of the coil 5 and magnet 7 may leak to some extent (approximately 2 to 3 Gauss) from the through hole 10, and for example, the influence on the floppy disk 14 attached to the end of the rotating shaft 9 cannot be ignored. However, there are drawbacks such as the fact that it can easily become a nozzle source for other electronic circuits.

(c) Purpose of the invention The present invention was made to solve these conventional drawbacks, and its purpose is to provide a brushless motor that has low leakage magnetic flux, is less likely to become a source of noise, and has good rotor position detection. do.

(d) Structure of the invention The invention consists of a rotor having a magnet, a coil that faces the magnet through a radial gap and rotates the rotor, and a magnetic shield plate that shields the magnetic flux generated by excitation of the magnet and the coil. a position detection sensor that detects the rotational position of the rotor and controls energization of the coil; a printed circuit board having a circuit pattern that connects the coil and the position detection sensor; and a through hole provided in the magnetic shield plate. It is equipped with a magnetic thin plate for closing.

The rotor is disposed on the upper periphery of the coil, and the magnetic shield plate has approximately the same size as the rotor, and is disposed between the coil and a printed circuit board below the coil so as to face the rotor. It is something. Further, the through hole is provided at a position facing the magnet to insert the position detection sensor, and the magnetic thin plate is arranged between the shield plate and the printed circuit board, and the magnetic thin plate is provided at a position facing the magnet. It is provided with a small hole for insertion of a lead pin.

In addition, in the present invention, a through hole is provided in the magnetic shield plate and this through hole is covered from below with a magnetic thin plate to form a space for inserting the position detection sensor. It is also possible to machine the shield plate to form a recess at the position corresponding to the through hole, but such machining (for example, press processing) can only be done at a very shallow depth (for example, 2 mm or less).
In the case of forming a recess, the processing time for forming the recess becomes relatively long, and the processing cost increases due to deterioration of the mold, etc., which is undesirable from a practical standpoint.

(E) Examples The details of the present invention will be explained below. Note that parts common to the conventional example are given the same reference numerals.

Furthermore, since the general configuration of the brushless motor of the present invention is substantially the same as that shown in FIG. 1, the description will be made with reference to FIG. 1 as well.

Printed circuit board 2 with electronic circuit formed in the figure
A bearing portion 1 is attached to the printed circuit board 2, and a magnetic shielding plate 3 is arranged so as to be overlapped with a magnetic thin plate 15, which will be described later, partially interposed on the printed circuit board 2.

A core 4 is supported on the bearing 1 , a coil 5 is wound around the core 4 , and a lead wire of the coil 5 is connected to an electronic circuit on a printed circuit board 2 .

A rotor 8, which is made up of a ring-shaped magnet 7 fixed to the inside of a cup-shaped rotor yoke 6, has a rotating shaft 9 attached to its center of rotation, and the rotating shaft 9 is supported by a bearing 1. A rotor 8 is arranged to cover the coil 5.

As shown in FIG. 4, the magnetic thin plate 15 has an arcuate band shape at a position facing the magnet 7, and small holes 16 are formed at predetermined intervals.

In a portion of the magnetic shield plate 3 that overlaps with the magnetic thin plate 15, a through hole 10 is formed as an elongated space that overlaps with the small hole 16 and has a larger diameter than the small hole 16.

Inside the through hole 10, a Hall element 11 is connected to the lead pin 12 by soldering so as to be planted on the printed circuit board 2 through the small hole 16.
2 is placed horizontally on the magnetic thin plate 15 so as to be bent. That is, a magnetic thin plate 15 is arranged between the printed circuit board 2 and the main body 13 of the Hall element 11, in other words, on the side of the main body 13 opposite to the magnet 7.

Note that the Hall element 11 detects the position of the rotor 8 and switches and controls the coil 5 via an electronic circuit.

The above-mentioned magnetic thin plates 15 may have a structure in which individual thin small disc-shaped plates are arranged under the main body 13 of the Hall element 11, or further, the magnetic thin plate 15 may be attached to the Hall element main body 13 with an adhesive mixed with a magnetic substance. The structure may be such that it is fixed to the printed circuit board 2.

(f) Effects of the invention As explained above, the brushless motor of the invention has a through hole 10 formed in the magnetic shield plate 3 disposed opposite the magnet 7 of the rotor 8.
A position detection sensor 11 that detects the position of the rotor 8 and controls the coil is disposed, and a through hole 10 is provided on the side of the sensor 11 that does not face the rotor.
Since the magnetic thin plate 15 that covers the through hole 1 is provided, the through hole 1
Since the leakage magnetic flux is reduced from 0, it is possible to suppress the influence on the motor load, for example, the floppy disk 14, and the generation of noise on the electronic circuit as much as possible.

Moreover, since the magnetic thin plate 15 is arranged in the through hole 10, the magnetic flux density to the sensor body 13 is improved compared to when the through hole 10 is simply formed, and the position of the rotor 8 can be detected reliably and stably. be converted into

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing a brushless motor, Figs. 2 and 3 are a plan view and longitudinal sectional view of main parts of a conventional brushless motor, and Figs. 4 and 5 are a brushless motor of the present invention. FIG. 1 is a plan view and a partial vertical cross-sectional view of a main part of an embodiment of a motor. DESCRIPTION OF SYMBOLS 1... Bearing part, 2... Printed circuit board, 3... Magnetic shield plate, 4... Winding core, 5... Coil, 6...
...Rotor yoke, 7...Magnet, 8...Rotor, 9...Rotating shaft, 10...Vacancy (through hole), 1
1...Sensor (Hall element), 12...Lead pin, 13...Sensor body (Hall element body), 1
4... Floppy disk, 15... Magnetic thin plate,
16...Small hole.

Claims (1)

[Claims for Utility Model Registration] A rotor having a magnet, a coil that faces the magnet through a radial gap and rotates the rotor, and a magnetic shield plate that shields magnetic flux generated by excitation of the magnet and the coil. a position detection sensor that detects the rotational position of the rotor and controls energization of the coil; a printed circuit board having a circuit pattern that connects the coil and the position detection sensor; and a through hole provided in the magnetic shield plate. the rotor is disposed on the upper periphery of the coil; the magnetic shield plate has approximately the same size as the rotor; The through hole is provided at a position facing the magnet and the position detection sensor is inserted therein, and the magnetic thin plate is arranged between the magnetic shield plate and the printed circuit board. A brushless motor, further comprising a small hole for inserting a lead pin of the position detection sensor.