JP2588043Y2 - Brushless motor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor.

[0002]

2. Description of the Related Art Various proposals regarding brushless motors have hitherto been made, for example, as described in Japanese Patent Application Laid-Open No. 3-215153. FIG. 3 shows an example of this brushless motor. This motor is used, for example, as a streamer motor for driving a magnetic tape. In the figure, reference numeral 1 denotes a bracket having a through hole 1a formed at a predetermined position. On the upper surface of the bracket 1 in the figure, a hollow cylindrical holder 2 has a hollow portion and a through hole 1a. It is fixed by the screw 3 so as to substantially coincide with the axial direction. An annular flange 2a is formed on the outer periphery of the holder 2, and a stator coil (stator winding) is formed on the flange 2a.
4 is attached. The outer rings of the bearings 5 and 5 are fitted and fixed to the inner periphery of the holder 2, respectively, and the rotating shaft 6 is fitted and fixed to each inner ring. A boss 7 is fixed to the upper end of the rotary shaft 6 in the figure, and a cup-shaped rotor case 8 made of a soft magnetic material has a large-diameter opening on the opposite boss side (in the figure). It is fixed so as to open toward the lower side. An annular drive magnet 9 having a predetermined number of poles magnetized on the lower surface in the figure is attached to the inner peripheral surface of the rotor case 8 facing the stator coil 4. A yoke 12 is formed on the inner periphery of the boss-side end and is made of a soft magnetic material to form a main magnetic flux path and to prevent foreign matter from entering from outside. Rotor case 8
An annular plastic magnet 10 is fixed to the outer periphery of the device. An idler (not shown) for driving the cartridge tape is in contact with an outer periphery 10b of the small diameter portion of the plastic magnet 10, and an outer periphery 1b of the large diameter portion is provided.
0a is magnetized for FG (frequency generator). Plastic magnet 10 on the bracket 1
A magnetic sensor 11 for detecting a rotation frequency is disposed at a position facing the FG magnetized portion 10a. The magnetic sensor 11 is attached to a sensor holder 14.

When a predetermined sinusoidal current is supplied to the stator coil 4 via the coil terminal wire 13, a rotating force is generated, and the rotating shaft 6, the boss 7, the rotor case 8, the driving magnet 9, the yoke 12 and plastic magnet 10
The rotor is made to rotate. And
When the rotor rotates, a change in the magnetic field of the FG magnetization 10a is detected by the magnetic sensor 11, and feedback control or the like is performed based on an output signal from the magnetic sensor 11. When the rotor rotates, the outer periphery 10b of the small diameter portion of the plastic magnet 10 rotates to rotate the roller of the cartridge via the idler.

Here, it is desirable that the rotor has a small run-out during rotation in order to obtain good tape running. This is because if the deflection of the outer periphery 10b of the small diameter portion of the plastic magnet 10 is small, the peripheral speed, that is, the tape running speed, is stable, and if the deflection of the outer periphery 10a of the large diameter portion is small, the signal extracted by the magnetic sensor 11 is stable. Because.

[0005] Therefore, after assembling as shown in FIG.
The outer peripheral surface of the yoke 12 was subjected to lace processing (assembly processing).
Is adhered to the opening side portion, and it is difficult to remove as apparent from the drawing, and therefore, there is a problem that the stability of quality is hindered.

Therefore, the present applicant has solved the above-mentioned problems in a brushless motor filed separately from the present invention.
In this brushless motor, since the drive magnet 9 is configured to be fixed to the yoke 12, it is possible to perform lace processing before assembling the yoke 12 to which the drive magnet 9 is fixed to the rotor set. Therefore, the adverse effect of the magnetic attraction by the drive magnet 9 can be eliminated, and the adhesion of the cutting powder to the yoke 12 and the intrusion into the inside of the motor by the magnetic attraction during the lace processing are prevented.

[0007]

However, the brushless motor has the following problems. That is, the yoke 12 to which the drive magnet 9 is fixed is attached to the rotor case 8 by positioning the drive magnet 9 in the axial direction.
This is done by press-fitting the inner peripheral surface of the drive magnet and aligning the ends thereof flush with each other. However, since the axial position of the drive magnet 9 due to the press-fitting tends to fluctuate, the drive magnet 9 and the stator coil 4 are connected to each other. There is a problem in that it cannot be separated at a predetermined distance, and therefore the characteristics vary. In addition, there is a fear that the plastic magnet 10 may be loosened, shifted, or fall off over time.

In view of the above, the present invention provides a brushless device in which the positioning of the yoke to which the driving magnet is fixed is accurately performed, the characteristics are stabilized, and the plastic magnet is securely fixed to the rotor case, thereby preventing displacement and falling off. An object is to provide a motor.

[0009]

In order to achieve the above object, a brushless motor according to the present invention has a boss fixed to a rotating shaft, a cup-shaped rotor case fixed to the boss, and an outer periphery of the rotor case. A plastic magnet fixed to the surface, a magnetic sensor arranged to face an FG magnetized portion magnetized on the outer periphery of the plastic magnet, an annular drive magnet rotating integrally with the rotor case, In a brushless motor having a stator coil facing a driving magnet, a concave portion is formed at a plurality of locations on the circumference of the outer peripheral surface of the rotor case, and a convex portion is formed on an inner peripheral surface at a position corresponding to the concave portion. The plastic magnet is molded and fixed to the outer peripheral surface of the rotor case, and the drive magnet is fixed to the yoke. In contact with the end surface of the convex portion, it is characterized by comprising the yoke fitted and fixed to the inner circumference of the rotor casing.

[0010]

According to the brushless motor in such a means, when the plastic magnet is molded and fixed to the outer peripheral surface of the rotor case, the plastic magnet flows into the concave formed on the outer peripheral surface of the rotor case, and the plastic magnet enters the concave. The projection is formed, and the plastic magnet is securely fixed to the rotor case.
Also, by the convex portion formed on the inner peripheral surface of the rotor case,
The yoke is accurately positioned, and the drive magnet and the stator coil fixed to the yoke can always be kept at a predetermined distance.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a brushless motor showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and is the same as that described in the prior art of FIG. The reference numerals are used, and the description is omitted here. The feature of the brushless motor of this embodiment is that a plurality of locations on the circumference of the hollow cylindrical portion of the rotor case 18 are bent toward the shaft 6, that is, inward, and the bent portion 18A The point is that a convex portion 20c corresponding to the concave outer peripheral portion is formed on the plastic magnet 20.

Here, the bent portion 18 of the rotor case 18
A is formed, for example, by press stamping, and is formed near the boundary between the poles of the drive magnet 9 as shown in FIG. In addition, plastic magnet 2
The 0 convex portion 20c is formed on the outer peripheral surface of the rotor case 18 by, for example, pouring a plastic magnet and molding.

Then, the yoke 12 to which the drive magnet 9 is fixed is pressed into the rotor case 18 and the yoke 12 is brought into contact with the end face 18a of the bent portion 18A of the rotor case 18 so that the yoke 12 is positioned. It has become.

In this embodiment, in order to make the axial length of the motor the same as that shown in FIG. 3, the flange to which the stator coil 4 of the holder is fixed is connected to the upper end in FIG. The holder 2
The function of No. 2 has not changed at all from the conventional one, and the sign of the FG magnetized portion 20a of the plastic magnet 20 and the outer periphery 20b of the small diameter portion has also been changed by changing the sign of the plastic magnet. 3 is exactly the same as that shown in FIG.

As described above, in this embodiment, a plurality of locations on the circumference of the hollow cylindrical portion of the rotor case 18 are bent toward the shaft 6 to form a bent portion 18A, and the plastic magnet 20 is attached to the rotor case 18. The drive magnet 9 is fixed to the yoke 12 while being fixed to the outer peripheral surface of the case 18, and the yoke 12 is brought into contact with the end surface 18 a of the bent portion 18 A to fit the yoke 12 to the inner peripheral surface of the rotor case 18. Because it is fixed, plastic magnet 2
When the plastic magnet 20 is molded and fixed to the outer peripheral surface of the rotor case 18, the plastic magnet 20 flows into a concave portion formed on the outer peripheral surface of the rotor case 18, and the convex portion 20c of the plastic magnet 20 is formed in the concave portion. Are securely fixed to the rotor case 18. Therefore, it is possible to prevent the plastic magnet 20 from shifting or falling off.
The bent portion 18A formed on the rotor case 18 accurately positions the yoke 12 so that the drive magnet 9 and the stator coil 4 fixed to the yoke 12 are always kept in a predetermined position. It can be separated. Therefore, it is possible to stabilize the motor characteristics.

Further, as described above, the rotor case 1
8 is formed near the boundary between the poles of the drive magnet 9 so that part of the magnetic flux of the drive magnet 9 directly enters the rotor case 18 without passing through the stator coil 4. Therefore, the magnetic flux distribution of the drive magnet 9 can be approximated to a sinusoidal wave with respect to the rotation angle of the rotor, and the rotation of the motor can be made smooth.

Since the drive magnet 9 is fixed to the yoke 12 in the same manner as the brushless motor filed separately by the present applicant, the yoke 12 to which the drive magnet 9 is fixed is removed. In the state (before assembly), it is possible to perform the lace processing for taking out the run-out, so that the adverse effect of the magnetic attraction by the drive magnet 9 during the lace processing can be eliminated. Therefore, the cutting powder does not adhere to the yoke 12 or enter the inside of the motor by magnetic attraction during the lace processing, so that it is of course possible to improve the stability of quality.

Although the invention made by the present inventors has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say, for example, in the above-described embodiment, an example in which the brushless motor is used as a streamer motor for driving a magnetic tape is described, but it goes without saying that the brushless motor can be used as a motor for other purposes. It is possible.

[0019]

As described above, according to the brushless motor of the present invention, the concave portion is provided at a plurality of locations on the circumference of the outer peripheral surface of the rotor case, and the convex portion is provided at the inner peripheral surface at a position corresponding to the concave portion. The plastic magnet is formed and fixed to the outer peripheral surface of the rotor case, and the drive magnet is fixed to the yoke. The yoke is brought into contact with the end surface of the projection, and the yoke is fitted and fixed to the inner peripheral surface of the rotor case. When the plastic magnet is molded and fixed to the outer peripheral surface of the rotor case, the plastic magnet flows into a concave portion formed on the outer peripheral surface of the rotor case, and a convex portion of the plastic magnet is formed in the concave portion.
The plastic magnet is securely fixed to the rotor case. Therefore, it is possible to prevent the plastic magnet from shifting or falling off. In addition, the convex portion formed on the inner peripheral surface of the rotor case accurately positions the yoke, so that the drive magnet fixed to the yoke and the stator coil can always be separated by a predetermined distance. Therefore, the motor characteristics can be stabilized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a brushless motor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view of a brushless motor showing a conventional technique.

[Explanation of symbols]

 Reference Signs List 4 stator coil 6 rotating shaft 7 boss 9 drive magnet 11 magnetic sensor 12 yoke 18 rotor case 18A concave portion (convex portion) 18a convex end face 20 plastic magnet 20a FG magnetized portion

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02K 29/08 H02K 21/00

Claims (1)

(57) [Scope of request for utility model registration] 1. A boss fixed to a rotating shaft, a cup-shaped rotor case fixed to the boss, a plastic magnet fixed to an outer peripheral surface of the rotor case, and magnetized on an outer periphery of the plastic magnet. A brushless motor comprising: a magnetic sensor arranged to face the FG magnetized portion; a ring-shaped drive magnet rotating integrally with the rotor case; and a stator coil facing the drive magnet. Concave portions are formed at a plurality of locations on the circumference of the outer peripheral surface of the rotor case, and convex portions are formed on the inner peripheral surface at positions corresponding to the concave portions, and the plastic magnet is molded and fixed to the outer peripheral surface of the rotor case, The drive magnet is fixed to a yoke, and the yoke is brought into contact with an end surface of the convex portion, and the yoke is attached to an inner peripheral surface of the rotor case. Brushless motor that is fitted and fixed.