JPS59204456A - Dc motor - Google Patents

Abstract

PURPOSE:To enable to reduce the thickness of a DC motor while having high speed starting property by providing first and second drive magnets which are respectively magnetized in perpendicular and axial directions to a rotational shaft, and respectively supplying magnetic fluxes in radial and axial directions. CONSTITUTION:A DC motor has a rotor assembly I , a stator assembly II and a housing assembly III. The assembly I has a rotational shaft 1, a turntable 2, a rotor yoke mounting boss 3, a rotor yoke 4, and the first and second drive magnets 5, 12. The magnet 5 is magnetized in a direction perpendicular to the shaft 1, and the magnet 12 is magnetized axially. The magnet 5 supplies the magnetic flux circumferentially, and the magnet 12 supplies the magnetic flux from the plane direction. These magnetic fluxes cross the stator winding 7 to generate a torque.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a DC motor used in a magnetic disk drive.

Conventional configurations and their problems Information devices such as magnetic disk drives are becoming thinner, and drive DC motors are also becoming thinner, but the starting characteristics remain the same as before. ``There is a need for something with shorthand dynamic characteristics. In addition, not only magnetic disk devices but also other devices using DC motors are becoming thinner and smaller, and the DC motors used in these devices are also required to be thinner and have high-speed startup characteristics.

Conventionally, a DC motor having a configuration shown in FIG. 1 or 2 has been used in a magnetic disk drive. Figure 1 shows a DC motor with slotted layers facing each other, and the rotor assembly (■) consists of a rotating shaft 1, a tar table 2 fixed to the rotating shaft 1, and a rotor yoke mounting boss fixed to the rotating shaft 1. 3
and the rotor yoke 4 fixed to the rotor yoke mounting boss.
and a drive magnet 5 fixed to the inner peripheral surface of the rotor yoke.
It consists of Note that the drive magnet 5 is attached to the rotating shaft 1.
It is magnetized in the direction perpendicular to (radial direction). on the other hand,
The stator assembly (■) includes a toothed stator yoke 6 disposed facing the drive magnet 5 with a predetermined gap in the radial direction;
It consists of a stator winding 7 and is fixed to the housing assembly (2).

...Using assembly ■ incorporates bearings 8 and 9 that rotatably support the rotating shaft 1 and bearings 8 and 9.
It is composed of Uzing 10. Note that 11 is a printed circuit board for mounting the position detection element, detecting the speed, and connecting the stator windings.

FIG. 2 shows a face-to-face DC motor, and the rotor assembly 1 includes a rotating shaft 1, a turntable 2 fixed to the rotating shaft 1, and a rotor yoke mounting boss 3 fixed to the rotating shaft 1.
and the rotor yoke 4 fixed to the rotor yoke mounting boss 3, and fixed to the inner surface of the rotor yoke. It is composed of a driving magnet 5. Note that the drive magnet 5 is magnetized in the axial direction (vertical direction in the figure).

On the other hand, the stator assembly (2) includes the stator 6, the printed circuit board 11 fixed to the stator yoke 6, and the printed circuit board 1.
The stator winding 7 is fixed to the housing assembly 1, and the stator winding 7 is fixed to the housing assembly 1. The housing assembly (2) has the same structure as the conventional example shown in FIG. In either case, the rotor's position signal is detected by a Hall element and the current flowing through the drive winding is controlled to rotate the rotor.

5/°--mi In the configuration of the above conventional example, in the case of the configuration shown in FIG.
The air gap between the stator yoke 6 and the drive magnet 5 can be easily set to about 0.5 mm because it is easy to obtain mechanical precision, so the operating point of the magnetic circuit is usually a permeance coefficient of 5 to 1 oz. It has a high value.

The driving magnet 5 has a ring-shaped anisotropic ferrite magnet, which is different from an isotropic ferrite magnet.
Ring-shaped isotropic magnets are generally used because they do not offer very good characteristics and are extremely expensive.

In the case of the above motor example, when the motor height is above a certain height, the permeance coefficient is large, so a large starting torque can be obtained, and the cost is low.

However, in the case of thinning, the coil end heights A and B of the stator winding 7 can hardly be changed, so the decrease in the motor height directly leads to a decrease in the thickness of the stator yoke 6. Therefore, for example, if the motor height is 10
In a motor with a thickness of 3 mm and a stator yoke 6, if the motor height is lowered by 10 mm to 9 mm and 61'-'', the thickness of the stator yoke 6 will be 2 mm, and the thickness will decrease by about 30 mm. As a result, the motor regulation (rate of change in rotational speed per unit torque, the value decreases as the motor gets larger), which is one of the main characteristics that expresses the volumetric efficiency of the motor, approximately doubles.
The drawback was that the volumetric efficiency was only about half as low.

On the other hand, in the case of the configuration shown in FIG. 2, the magnetic flux linkage area of the stator winding 7 is significantly improved compared to the configuration shown in FIG.
Even if the motor is made thinner, the above-mentioned magnetic flux linkage area hardly changes, so the thinning does not cause an extreme deterioration in volumetric efficiency as in the configuration shown in Figure 1, but the configuration shown in Figure 2 generally has a drive magnet. 5 and the stator yoke 6, which improves the volumetric efficiency of the motor and the demagnetization characteristics of the magnet.
In other words, since the maximum energy is extracted from the magnet, the operating point of the magnetic circuit is a permeance coefficient of 0.8 to 1.
It is set to a small value such as 5G/Qe. Also,
The drive magnet 5 is magnetized in the axial direction and is a disc-shaped anisotropic ferrite magnet 7'. Anisotropic ferrite magnets are used because they can be produced relatively inexpensively.

In either case, in the configuration of the conventional example described above, if a fabric-based magnet or the like with high energy output is used as the drive magnet 5, the magnetic flux interlinking with the stator winding 7 increases by 10/10, and the generation per unit current increases. Since the torque is reduced, the starting characteristics and volumetric efficiency are the same as above, but the big problem is that the price increases by a much larger proportion.

In addition, in the case of the configuration shown in FIG. 1, the drive magnet 6 is fixed to the inside of the outer periphery of the rotor yoke 4, and the volume of the drive magnet 5 can be small, so the inertia of the rotor assembly is relatively small. In this case, as described above, the body efficiency is low, that is, the generated torque is extremely small, resulting in poor starting characteristics. (In other words, the startup time becomes longer.) This becomes an extremely serious problem when used in information equipment and the like. On the other hand, in the case of the configuration shown in Fig. 2, although the ratio of reduction in generated torque due to the thinning is not as great as that of the configuration shown in Fig. 1, since the operating point of the magnetic circuit is essentially low,
The torque generated per unit volume of the drive magnet 5 is small, and in order to generate a predetermined torque, the volume of the drive magnet 5 must be increased. Therefore, the inertia of the rotor assembly I increases and the starting characteristics are poor.

As mentioned above, none of the configurations could satisfy the characteristics required for information equipment and the like in terms of volumetric efficiency and startup characteristics.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and provides a magnetic circuit with a high operating point and a low inertia rotor, as well as a surface facing magnetic circuit with a high operating point, thereby achieving high volumetric efficiency and high speed. The present invention provides a thin motor that exhibits starting performance.

Structure of the Invention The present invention includes a first drive magnet that is magnetized in the direction perpendicular to the rotation axis, and a second drive magnet that is magnetized in the axial direction, and the first drive magnet is magnetized in the circumferential direction ( By supplying magnetic flux from the radial direction and the second driving magnet supplying magnetic flux from the planar direction (axial direction), it is possible to reduce the thickness while maintaining high-speed startup characteristics.

DESCRIPTION OF THE EMBODIMENT FIG. 3 shows an embodiment of the present invention. still,
Components with the same reference numerals as in FIGS. 1 and 2 indicate the same components.

In FIG. 3, the second drive magnet 12 is fixed to the rotor yoke 4 located in the space between it and the axial end face of the stator yoke 6, which was a dead space due to the presence of the stator winding 7, and It is configured to maintain a predetermined gap in the axial direction of the assembly H1. Note that this second drive magnet 12 is magnetized in the axial direction (vertical direction in the figure). Therefore, in this configuration, the first drive magnet 7 supplies magnetic flux from the circumferential direction as in the configuration shown in FIG. 5, magnetic flux is supplied from the plane direction.

However, in the case of the configuration shown in FIG. 2, the gap between the drive magnet 5 and the stator yoke 6 is large, and is 1 ol'.

From the point of view of volumetric efficiency and magnetic flux demagnetization characteristics, the operating point of the magnetic circuit must be set to a small value such as a permeance coefficient of 0.8 to 1. Whereas the generated torque per volume was small, in the case of the embodiment of the present invention, the gap between the second drive magnet 12 and the stator yoke 6 is configured to be quite small, and the permeance coefficient at the operating point of the magnetic circuit is 4. ~8
G/Qe is provided with a magnetic circuit which is quite large and has the characteristic of facing each other.

That is, the magnetic flux emitted from the drive magnet 6 passes through the stator yoke 6 and interlinks with the stator winding 7 to generate torque, and at the same time, the magnetic flux generated by the second drive magnet 12 also flows from the surface of the stator yoke 6 facing the drive magnet 12. It enters the stator yoke 6 and interlinks with the stator winding 7 to generate torque. Of course, since each of the generated torques described above is always applied in the same direction, the starting torque becomes larger by the increase in the second drive magnet 12 than in the configuration shown in FIG. The permeance coefficient at the operating point of the magnetic circuit is extremely large.
The torque generated per volume of the drive magnets 7 and 12 is large. Therefore, the starting characteristics are such that the inertia of the rotor yoke 4 is higher than that of the second drive magnet 12 than in the configuration shown in FIG.
However, the increase in starting torque is much larger, resulting in extremely high volumetric efficiency and high-speed starting characteristics. -! In addition, when the stator yoke 6 becomes thinner, the magnetic flux caused by the first drive magnet 6 decreases, but the magnetic flux caused by the second drive magnet 12 hardly changes even if the stator yoke 6 becomes thinner, as in the configuration shown in FIG. Therefore, the effects of the present invention become more apparent as the thickness becomes thinner.

In the above embodiment, the first drive magnet 7 and the second magnet 5 are configured separately, but as shown in FIG. The first drive magnet part 13a is magnetized in the direction perpendicular to 1, and the second drive magnet part 13a is magnetized in the axial direction.
It goes without saying that the same effect can be produced even if 3b is integrally magnetized.

FIG. 6 shows another embodiment of the present invention, in which it is applied to a current motor equipped with a commutator and current. In the figure, 21 is a stator yoke configured in a cup shape, and inside the outer periphery, there is a stator yoke in a direction perpendicular to the rotating shaft 22 (radial direction).
A ring-shaped first drive magnet 23 magnetized in the axial direction (vertical direction in the figure) is fixedly attached, and a disc-shaped second drive magnet magnetized in the axial direction (vertical direction in the figure) is located on the inside facing the rotor yoke, which will be described later. 24 is fixed. Reference numeral 25 denotes a cup-shaped bracket having an oil-impregnated bearing 26 at its center, which supports the rotary shaft 22 together with an oil-impregnated bearing 27 provided at the center of the stator yoke 21 . 28 and 29 are rotating shafts 22
Bracket 25 with a brush that contacts commutator 30 equipped on
It is attached via a brush plate spring (not shown) to a synthetic resin bottom plate 31 provided on the inner lower surface of the brush plate. A rotor yoke 32 is fixed to the rotating shaft 22, and a rotor winding 33 is wound around the rotor yoke. Note that the rotor yoke 32 faces the drive magnets 23 and 24 fixed to the stator yoke 21 with a certain gap in between.

1s t -:j The above configuration also provides the same effects as the configuration shown in FIG. 3. Although the first drive magnet 23 is configured in a ring shape, it goes without saying that it may be configured in a C-shape.

FIG. 6 shows a comparison of the measured values of the characteristics of the conventional DC motor shown in FIG. 1 and the DC motor of the present invention shown in FIG. In FIG. 6, A is the torque-rotational speed characteristic of a conventional DC motor, B is the torque-current characteristic of a conventional DC motor, C is the custom-made torque-rotational speed of the present invention, and D is the torque-current characteristic of the present invention. be.

As shown in FIG. 6, the starting torque is approximately 1.5 times greater, but the inertia of the rotor assembly I is only approximately 1.1 times greater. Also, the motor leg ration is cleared by approximately %. Note that the outer diameter of the rotor yoke 4 is 50 mm,
The thickness is 7 mm.

Effects of the Invention As is clear from the above description, the present invention provides the following effects.

(b) Characteristics can be dramatically improved with a simple configuration that is almost the same as the conventional one.

14''-Nib (B) Since the second drive magnet is installed using the space that was previously available, the volume utilization rate is extremely high.

2) The second j driving magnet faces the front side, but since the air gap with the stator core is extremely small, the permeance coefficient at the operating point of the magnetic circuit can be increased, and the generated torque per volume of the second driving magnet is large. It has good volumetric efficiency.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional slotted layer-opposing type DC motor, FIG. 2 is a cross-sectional view of a conventional slotless surface-opposed DC motor, and FIG. 3 is a cross-sectional view of a DC motor showing an embodiment of the present invention. 4 and 5 are cross-sectional views showing other embodiments of the present invention, and FIG. 6 is a characteristic diagram of a conventional DC motor and actual measurements after implementing the present invention. 1.22... Rotating shaft, 4.32... Rotor yoke, 5, 23... First drive magnet, 6... Stator yoke, 7. ...Stator winding, 1o...Housing, 11.24
. . . Second driving magnet 15, 33 . . . Rotor winding. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 Figure 3! Figure 4 Figure 5? ? Figure 6 (l-cm)

Claims (4)

[Claims] (1) A first drive magnet magnetized in a direction perpendicular to the rotating shaft, a cup-shaped rotor yoke to which the first drive magnet is fixed, a rotating shaft to which the rotor yoke is attached, and the first drive magnet. Equipped with a stator yoke disposed facing the magnet with a predetermined gap in the radial direction, a stator winding wound around the stator yoke, and a bearing that supports the stator yoke and rotatably supports the rotating shaft. a second drive magnet that is magnetized in the axial direction and fixed to the rotor yoke while maintaining a predetermined gap in the axial direction from the stator yoke. (2) The DC motor according to claim 1, wherein the first drive magnet and the second drive magnet are integrally formed. (3) 10th drive 2 magnetized in a direction perpendicular to the rotation axis
`` '' A dynamic magnet, a stator yoke to which the first driving magnet is fixed, and a rotor yoke disposed opposite to the first driving magnet with a predetermined gap in the radial direction.
A rotor winding wound around the rotor yoke, a rotating shaft to which the rotor yoke is attached, and a second drive magnet that is magnetized in the axial direction and fixed to the stator yoke while maintaining a predetermined gap in the axial direction from the rotor yoke. A DC motor equipped with (4) The DC motor according to claim 3, wherein the first drive magnet and the second drive magnet are integrally formed.