JPH03222664A - Brushless motor - Google Patents

Abstract

PURPOSE:To protect a magnetoresistance element against breakdown by providing a fixing holder with a first protrusion facing with an FG magnet and setting the gap between the edge of the first protrusion and the magnetosensitive face of the magnetoresistance element equal to the gap between the FG magnet and the magnetoresistance element. CONSTITUTION:A fixing holder 20 mounted on a circuit board 26 and having a magnetoresistance element 32 facing through a predetermined gap with an FG magnet 18 is provided with a first protrusion 33 facing with the FG magnet 18, and the gap between the edge of the first protrusion 33 and the magnetosensitive face 32a of the magnetoresistance element 32 is set equal to the gap between the FG magnet 18 and the magnetoresistance element 32. Consequently, when the FG magnet 18 is located at a predetermined position, a gap is formed automatically between the FG magnet 18 and the magnetoresistance element 33 and the gap between the FG magnet 18 and the magnetoresistance element 33 is covered with the first protrusion 33.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brushless motor having a mounting holder for a magnetoresistive element provided for use in optical discs, VTR capstan motors, etc. that require a high-precision rotation mechanism. It is something.

[Conventional technology]

7 and 8 are diagrams showing a conventional brushless motor disclosed in, for example, Japanese Utility Model Application Publication No. 64-47573. In the figures, (1) is a holder, a bearing (2 is installed inside,
A board (3) is attached to the outer wall. (A) is a coil provided on this board, (5) is a shaft fitted into the above bearing (2), and (6) is a rotor plate fitted to one end of this shaft, with an opening on one side. (7) It has a bottomed shape. (f) is the main magnet provided in this rotor plate so as to face the coil 4), (9) is the FG magnet provided on the outer wall of the rotor plate +61, and αω is the main magnet provided on the substrate (3). Mounting holder (1) is fixed with screw (11).
2) is the FG magnet (9) installed on this mounting holder.
) and are magnetoresistive elements facing each other with a predetermined distance a.

The conventional brushless motor is constructed as described above, and the rotor plate (6) having the main magnet (8) and the FG magnet (9) is moved by attraction and repulsion due to the magnetic field generated by energizing the coil (4). Rotate. Then, the magnetoresistive element (12) is connected to the FG magnet (9).
), the rotational speed of the rotor plate (6) and shaft (5) can be detected as a signal. Based on this signal, a control circuit (not shown) controls the acceleration and deceleration of the motor. The rotation speed can be fixed.

[Problem to be solved by the invention]

In the conventional brushless motor as described above, if the distance a between the magnetoresistive element (12) and the FG magnet (9) is too wide, it will not be possible to read the recorded magnetism, and if it is too narrow, collisions due to vibration will occur. A gauge must be used to adjust this distance a, resulting in poor mounting accuracy.Furthermore, the surface of the magnetoresistive element (12) is weak in strength and will break if it comes into contact with other parts. However, there was a problem in that the surface of the magnetoresistive element (12) was easily scratched by the gauge.

Further, there was a problem in that foreign matter could enter between the rotating side and the magnetoresistive element (12) after assembly and destroy the magnetoresistive element (12).

This invention was made to solve the problem,
The distance between the main magnet and FG magnet can be adjusted with high accuracy and reliability through a simple process, and
The object of the present invention is to obtain a brushless motor that can prevent foreign matter from entering after adjustment.

[Means to solve the problem]

The brushless motor according to the present invention has a bottomed shape with an opening on one side, a driving magnet on the inner wall, and an FG on the outer wall.
A rotor plate provided with a magnet, a shaft fitted to the rotor plate, a bearing into which the shaft is fitted are installed internally, and a stator provided on a side wall so as to face the driving magnet at a predetermined distance. a holder having a magnetic resistance element mounted on the circuit board and facing the FG magnet at a predetermined distance on a magnetically sensitive surface; A first protrusion facing the FG magnet is provided, and the distance between the tip surface of the first protrusion and the magnetically sensitive surface of the magnetoresistive element is made equal to the distance between the FG magnet and the magnetoresistive element. .

Further, the FG magnet is provided with a second protrusion facing the magnetoresistive element and an adjustment part, and the protrusion length of the second protrusion and the F
The sum of the distance between the G magnet and the magnetic resistance element is made equal to the distance between the tip end surface of the first protrusion and the magnetically sensitive surface of the magnetic resistance element.

[Effect]

In this invention, there is provided a rotor plate having an opening on one side and a bottomed shape, a drive magnet on the inner wall and an FG magnet on the outer wall, a shaft fitted into the rotor plate, and a shaft into which the shaft is fitted. a holder having a stator installed therein and a stator provided on a side wall to face the driving magnet at a predetermined distance; a circuit board mounted on the holder; and a FG magnet mounted on the circuit board. a mounting holder having magnetoresistive elements facing each other at a magnetically sensitive surface with a predetermined interval, the mounting holder is provided with a first protrusion facing the FG magnet, and the distal end surface of the first protrusion and the By making the distance between the magnetically sensitive surface of the magnetoresistive element equal to the distance between the FG magnet and the magnetoresistive element, the first protrusion of the mounting holder is
The mounting holder can be fixed by contacting the G magnet, and when the FG magnet comes to the fixed position, the gap between the FG magnet and the magnetic resistance element is automatically formed, and the first protrusion The gap between the FG magnet and the magnetoresistive element is covered.

Further, the FG magnet is provided with a second protrusion facing the magnetoresistive element and an adjustment part, and the protrusion length of the second protrusion and the F
By making the sum of the distance between the G magnet and the magnetic resistance element equal to the distance between the tip end surface of the first protrusion and the magnetically sensitive surface of the magnetic resistance element, the first protrusion of the mounting holder can be brought into contact with the adjustment part. When the FG magnet comes to a fixed position, a gap between the FG magnet and the magnetic resistance element is automatically formed, and the first protrusion connects the FG magnet to the magnetic resistance element. The distance between the resistive element and the resistive element is covered.

〔Example〕

FIGS. 1 to 3 are diagrams showing an embodiment of the present invention,
In the figure, (15) is the rotor plate, which has an opening (1
6) and has a bottomed shape. (17) is a driving magnet provided on the inner wall of the rotor plate, and (18) is an FG magnet provided on the outer wall of the rotor plate (15) to generate a signal generating magnetic field. (18a) is the magnetized surface of this FG magnet, (19) is the shaft fitted approximately in the center of the rotor plate (15), (20)
is a holder that has a bearing (21) inside which this shaft is inserted and rotatably supported, and a circuit board mounting part (
22). (23) is the side wall (2
4) is a stator provided so as to face the driving magnet (17), and consists of a stator core around which a coil (25) is wound. (26) is the circuit board mounting part (
22), on which electronic components (27) are mounted. Reference numeral (28) denotes a mounting holder disposed on this circuit board, which is L-shaped with a mounting hole (29) on one side and an upright element mounting portion (30) on the other. ), the element mounting portion (30) is fixed so as to face the FG magnet (18). Note that the mounting hole (29) is formed to be long with its length extending in the direction of the adjustable element mounting portion (30) with respect to the mounting hole 31). (32) is a magnetoresistive element attached to the outer wall of the element mounting part (30), which is attached to the FG magnet (18).
The FG magnet (
Detect the signal recorded in 18). (32b) is a terminal provided on the magnetically sensitive surface (32al), and (33) is a terminal protruding from the element mounting portion (30) of the mounting holder (28) to face the FG magnet (18). At the first protrusion, the distal end surface of the first protrusion and the magnetoresistive element (3
The distance B between the magnetically sensitive surface (32a) and the magnetoresistive element (3) is
2) and FG magnet)-(18>).

As a result, the magnetized surface (L8a) of the FG magnet (18)
) and the distal end surface of the first protrusion (33) is zero in the radial direction of the rotor plate (15). (40) is a stopper of the holder (20), which is fitted onto the shaft (19).

In the brushless motor configured as above,
As shown in FIGS. 4(a), (b), and (c), the assembly consists of a holder (20) having a circuit board (26) that is temporarily fixed with a mounting holder (28) or mounting screws (31). The shaft (19) having the rotor plate (15) is press-fitted into the bearing (21), and as shown in (b), the magnetized surface (18al) of the FG magnet (18) and the first protrusion (33 ), the mounting holder (28
) is attached to the circuit board (26) and fixed with 31). In this case, the magnetoresistive element (32) is the FG magnet (
18) Even if it is inside, the first protrusion (33) is pushed out by the FG magnet (18), so the FG magnet (18) does not directly hit the magnetoresistive element (32).

Furthermore, when the shaft (19) is pushed into the normal position as shown in (c), the magnetized surface (18a) and the first protrusion (33) are displaced in the height direction and come into contact. There is no difference between the magnetically sensitive surface (32a) of the magnetoresistive element (32) and the first
It faces the tip surface of the protrusion (33) at a distance B. Then, the first protrusion (33) covers the magnetized surface (18a) and the magnetically sensitive surface D2a). Next, as in the conventional case, the rotor plate (15) rotates due to the attraction and repulsion caused by the magnetic field generated by energizing the coil (25), and the magnetic resistance element (32) is recorded on the FG magnet (18). By reading the magnetic field, the rotor plate (15)
And the rotation speed of the shaft (19) can be detected as a signal. By controlling acceleration and deceleration using this signal as a reference by a control circuit (not shown), the rotational speed of the brushless motor is fixed.

Note that the mounting hole (29) of the mounting holder (20) is formed to be long with its length extending in the direction of the element mounting portion (30), but it may also be provided in the rotational direction and left/right direction as shown in FIG. Effects similar to those of the above embodiment can be expected.

In addition, as shown in FIG. 6, it becomes a magnetized surface (18a) on the FG magnet (18), and a magnetoresistive element (32).
A second protrusion (34) facing the is partially provided, and is equal to the sum of the protrusion length C of the second protrusion and the distance A between the magnetoresistive element (32) and the FG magnet (18). Set the distance between the tip surface of the first protrusion (33) and the magnetically sensitive surface (32a) of the magnetoresistive element (32) so that If the mounting holder (28) cannot come into contact with the magnetized surface (18a) by making the adjustment section (35), the mounting holder (28) can be brought into contact with the adjustment section (35) and adjusted, so that the magnetized surface (18a) Since it is protected, the above embodiment can be further improved.

〔Effect of the invention〕

As explained above, the present invention includes a rotor plate having an opening on one side and a bottomed shape, a driving magnet on the inner wall and an FG magnet on the outer wall, a shaft fitted to the rotor plate, and a shaft fitted to the rotor plate. a holder having a stator therein in which a bearing is fitted, and a stator provided on a side wall facing the driving magnet at a predetermined distance; a circuit board mounted on the holder; and a stator mounted on the circuit board. a mounting holder having a magnetoresistance element facing the magnet at a predetermined interval on a magnetically sensitive surface; the mounting holder is provided with a first protrusion facing the FG magnet; By making the distance between the magnetically sensitive surface of the magnetoresistive element equal to the distance between the FG magnet and the magnetoresistive element, the first protrusion of the mounting holder can be brought into contact with the FG magnet and the mounting holder can be fixed; FG when the FG magnet is in place
The gap between the magnet and the magnetoresistive element is automatically formed, and the gap is covered by the first protrusion, allowing the gap to be adjusted with high precision and inexpensively without performing a complicated adjustment process. Can be adjusted and gap protected.

Further, the FG magnet is provided with a second protrusion facing the magnetoresistive element and an adjustment part, and the protrusion length of the second protrusion and the F
By making the sum of the distance between the G magnet and the magnetic resistance element equal to the distance between the tip end surface of the first protrusion and the magnetically sensitive surface of the magnetic resistance element, the first protrusion of the mounting holder can be used as the adjustment part. The mounting holder can be fixed by making contact, and when the PG magnet comes to the fixed position, the gap between the FG magnet and the magnetic resistance element is automatically formed, and the magnetized surface can come into contact with the first protrusion. protection, and quality can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a perspective view of the mounting holder, FIG. 3 is a partial sectional view,
4<al, (bl, and c) are process diagrams similarly showing assembly, FIG. 5 is a perspective view of a mounting holder showing another embodiment of the present invention, and FIG. 6 is a further example of another embodiment of the present invention. FIG. 7 is a cross-sectional view showing a conventional brushless motor, and FIG. 8 is a partial plan view showing a conventional brushless motor. (15) is a rotor plate, (+61 is an opening) ,(
17) is the drive magnet, (I8) is the FG magnet, (19) is the shaft, (20) is the holder, (21) is the bearing, (23) is the stator, (26) is the circuit board, (2
8) is a mounting holder, (32) is a magnetic resistance element, (32a
) is a magnetically sensitive surface, (33) is a first protrusion, (34) is a second protrusion, and (35) is an adjustment portion.

Claims (2)

[Claims] (1) A rotor plate having an opening on one side and a bottomed shape, with a driving magnet on the inner wall and an FG magnet on the outer wall, and a shaft fitted to the rotor plate;
A holder having a bearing therein into which the shaft is fitted and a stator provided on a side wall to face the driving magnet at a predetermined distance, a circuit board mounted on the holder, and a circuit board mounted on the circuit board. and a mounting holder having a magnetic resistance element facing the FG magnet at a predetermined distance on a magnetically sensitive surface, the mounting holder being provided with a first protrusion facing the FG magnet, the first protrusion A brushless motor characterized in that the distance between the tip end surface of the magnetoresistive element and the magnetically sensitive surface of the magnetic resistance element is equal to the distance between the FG magnet and the magnetic resistance element. (2) The FG magnet is provided with a second protrusion facing the magnetoresistive element and an adjustment part, and the protrusion length of the second protrusion and the F
The brushless motor according to claim 1, wherein the sum of the distance between the G magnet and the magnetic resistance element is equal to the distance between the tip end surface of the first protrusion and the magnetically sensitive surface of the magnetic resistance element. .