JPS6145736Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotor for a surface facing motor in which a rotor magnet and a stator coil are axially opposed to each other.

This type of surface-facing type or flat type brushless motor is equipped with a disk-shaped rotor yoke that holds a rotor magnet and serves as a magnetic path material. The rotor yoke generally has a cylindrical magnetic shielding peripheral wall around its outer periphery in order to prevent the magnetic flux of the magnet from leaking to the outside as much as possible. Further, a spacer or a positioning member for the magnet is required to separate the magnet and the outer peripheral wall so that the magnetic flux of the magnet is not short-circuited by the outer peripheral wall and to arrange the magnet at a predetermined position. As this spacer or positioning member, a stepped portion formed adjacent to the inner surface of the outer peripheral wall may be used. Therefore, this type of rotor yoke is generally manufactured by cutting (machining) a round bar or block of soft iron, and at this time, the above-mentioned outer peripheral wall and stepped portion are formed. This requires a large number of man-hours to process the parts, which is one of the causes of high costs. Furthermore, when reducing the moment of inertia of the rotor to improve the response characteristics of the motor, there is a limit to how thin the rotor yoke can be made through machining, and it has been difficult to further reduce the moment of inertia.

The present invention has been made in view of the above-mentioned problems, and aims to form a rotor yoke having the above-mentioned functions and structure at extremely low cost, and to reduce the moment of inertia.

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a vertical cross-sectional view of a two-phase switching type brushless motor to which the present invention is applied, Fig. 2 is a plan view of the rotor shown in Fig. 1, Fig. 3 is a plan view of the auxiliary yoke, and Fig. 4 is a conventional FIG. 3 is a partial cross-sectional view showing the rotor yoke of FIG.

As shown in FIG. 1, a cylindrical sleeve 2 is caulked and fixed to the center of a circular stator substrate 1. As shown in FIG. Oil-impregnated bearings 3 and 4 made of sintered metal are press-fitted into the upper and lower end portions of the center hole of the sleeve 2. A rotor 7 having a shaft 6 is rotatably supported by bearings 3 and 4 attached to the sleeve 2 of the stator board 1.

A disk-shaped rotor yoke 9 is caulked and fixed to one end of the shaft 6 via a brass boss 8. This rotor yoke 9 is formed by pressing parts into an outer peripheral wall 28.
It is shaped like a plate with a Therefore, the rotor yoke 9 is made as thin as possible to reduce the moment of inertia of the rotor. rotor yoke 9
A ring-shaped auxiliary yoke 17 shown in FIG. 3 is fixed to the front side of the yoke by spot welding. This auxiliary yoke 17 compensates for the insufficiency of the magnetic path cross-sectional area of the thin rotor yoke 9. Auxiliary yoke 17
is formed from a sheet metal press part, with 3 parts around its outer circumference.
It has two equally spaced protrusions 27. Since the convex portion 27 is inscribed in the outer circumferential wall 28 of the rotor yoke 9, the auxiliary yoke 17 is positioned relative to the rotor yoke 9 during welding.

A plurality of protrusions 26 for magnet positioning are further formed on the outer periphery of the auxiliary yoke 17. These protrusions 26 are shorter than the protrusions 27, and are bent toward the magnetic adhesion side of the auxiliary yoke 17, as shown in FIG. Therefore, as shown in FIG. 2, when assembling the motor, a plurality of magnets 16S and 16N are arranged along the convex portion 26 and fixed with adhesive while being positioned at predetermined positions in the radial direction of the motor. The positioning of each magnet 16 in the circumferential direction is performed based on three convex portions 27 spaced at 120° intervals. Further, when the magnet 16 is attached, the outer circumferential wall 28 of the rotor yoke and the outer surface of the magnet 16 are separated by a predetermined distance, thereby preventing short-circuiting of the magnetic flux of the magnet 16.

A stator 20 is disposed on the fixed side, closely facing the magnet 16. This stator 20 includes a coil substrate 19 and a coil 2 consisting of an A phase and a B phase.
It consists of 1. Coil board 19 is made of, for example, a flexible printed board, and is fixed to stator board 1 via spacer 22 .
A circuit pattern is formed on the surface side of the coil board 19, and the lead terminals of the coil 21 are connected to the circuit pattern, and the coil board 19 is pulled out to the outside to connect a motor drive circuit element (not shown). ) is installed.

A disc-shaped back yoke 10 is attached to the upper end of the boss 8 at a predetermined distance from the coil 21 of the stator 20 so as to rotate together with the rotor 7.
A plurality of holes 23 are formed in the back yoke 10 to prevent resonance or vibration. The back yoke 10 is fixed to the boss 8 of the rotor 7 by the attraction force of the magnet 16. When the motor is assembled, washers 14 and 15 are inserted into the shaft 6, and synthetic resin cap members 11 and 12 are fitted into both ends of the sleeve holding the bearings 3 and 4. Furthermore, a pulley 13 is attached to the tip side of the shaft 6.

FIG. 4 is a partial sectional view of a conventional rotor yoke 9 for comparison with the above embodiment. This rotor yoke 9 is made by machining from a soft iron bar, and an outer peripheral wall 28 and a step portion 29 for magnet positioning are formed during machining. The rotor yoke 9, which is formed into a dish shape, cannot be made thinner than a certain level at the bottom because of machining. Therefore, it is difficult to reduce the moment of inertia. Also, the number of manufacturing steps is extremely large.

On the other hand, the rotor yoke 9 of this embodiment is made of a pressed sheet metal part, and the auxiliary yoke 17, which is also made of a pressed sheet metal part, is provided in the part where the magnetic path cross-sectional area is insufficient, so that the moment of inertia can be reduced. This also ensures a sufficient magnetic path cross-sectional area. Further, the number of manufacturing steps can be reduced, and component costs can be reduced. Furthermore, since the magnet positioning portion can be formed on the auxiliary yoke 17, even if the rotor yoke 9 is formed of a pressed part, the magnet 16 can be easily and accurately positioned without providing a separate spacer or positioning member. Can be fixed.

As described above, the present invention has a two-layer structure consisting of the rotor yoke 9 and the auxiliary yoke 17.
Positioning of the auxiliary yoke 17 with respect to the auxiliary yoke 17 and rotor magnets 16N, 16S with respect to the auxiliary yoke 17
The positioning of the first and second positions provided on the auxiliary yoke 17
This is achieved with a simple configuration by the convex portions 27 and 26,
Since the rotor magnets are arranged at a predetermined distance from the outer peripheral wall of the rotor yoke 9,
Even with a two-layer structure, there is no need for special spacers or positioning members, and workability during assembly is also good. Therefore, it is possible to use a two-layer structure yoke, in which the rotor yoke is made of a thin sheet metal part and the auxiliary yoke compensates for the lack of magnetic path cross section, without any problems, resulting in a motor with a low moment of inertia and low cost. is obtained.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a two-phase switching type brushless motor to which the present invention is applied, Fig. 2 is a plan view of the rotor shown in Fig. 1, Fig. 3 is a plan view of the auxiliary yoke, and Fig. 4 is a conventional FIG. 3 is a partial cross-sectional view showing the rotor yoke of FIG. In addition, in the symbols used in the drawings, 7...
... rotor, 9 ... rotor yoke, 16 ... magnet, 17 ... auxiliary yoke, 19 ... coil substrate, 21 ... coil, 26, 27 ... convex portion.

Claims (1)

[Scope of Claim for Utility Model Registration] In a rotor of a surface-facing motor in which a rotor magnet mounted on a rotor yoke and a stator coil face each other in the motor axial direction, a ring-shaped motor is interposed between the rotor yoke and the rotor magnet. an auxiliary yoke; and a magnetic shielding outer circumferential wall formed on the rotor yoke to prevent the magnetic flux of the rotor magnet from leaking to the outside; The rotor magnet has a plurality of first convex portions inscribed in the outer circumferential wall, and a plurality of second convex portions that protrude by bending toward the magnet mounting surface side and circumscribe the outer circumferential edge of the rotor magnet; The auxiliary yoke is positioned with respect to the outer circumferential wall of the rotor yoke by the convex portion, and the rotor magnet is positioned on the auxiliary yoke with a predetermined gap from the outer circumferential wall by the second convex portion. A surface-facing motor rotor characterized by: