JPH04236152A - Spindle motor - Google Patents

Abstract

PURPOSE:To realize both high starting torque and high speed rotation by varying the length of gap between a stator and a rotor according to the rotation. CONSTITUTION:A magnet assembly 2 comprising a rotor magnet 2b and a rotor frame 2a is disposed oppositely to a stator core 4. The magnet assembly 2 is coupled through a spring 3 with a hab 1. When a spindle motor halts, no centrifugal force is exerted on the magnet assembly 2 and the spring 3 is not displaced thus minimizing an air gap delta. Upon rotation of the spindle motor, centrifugal force is exerted on the magnet assembly 2 and the spring 3 is displaced. The air gap delta is increased as the rotational speed increases thus realizing high speed rotation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor used in magnetic disk drives and the like.

0002

[Prior Art] In recent years, magnetic disk drive devices (hereinafter referred to as H
(DD) is increasingly being installed in small, lightweight office automation equipment such as laptop computers and notebook-sized computers. HDDs installed in these OA devices, especially notebook-sized personal computers, are required to be smaller and lighter and have higher recording density.

[0003] Furthermore, since notebook-sized personal computers are often used on battery power, the operating time when using the battery is long, and therefore the HD
It is desired that D has low power consumption. In addition, conventional HDD drive voltages were 5V and 12V, but
In a notebook-sized computer that is powered by a battery, the drive voltage for the HDD is a single 5V.

By the way, in HDDs, contact, start, and stop (hereinafter referred to as C) are performed between the magnetic head and the magnetic disk.
Because SS) is repeated, the spindle motor mounted on the HDD needs to overcome the load torque caused by the frictional force between the magnetic head and the magnetic disk to start up. FIG. 5 is a cross-sectional view taken along the line AA of a conventional outer rotor type spindle motor, which includes a hub 10, a rotor frame 11, a rotor magnet 12, a winding 13, a stator core 14, a bracket 15, a shaft 16, and the like.

[0005] When this spindle motor is used in an HDD, if the drive voltage of the HDD is a single 5V, the drive voltage of the spindle motor will naturally also be 5V, and in a conventional configuration based on 12V drive, the starting torque will be reduced. This has been addressed by changing the rotor magnet from ferrite to rare earth to increase the magnetic flux in the magnetic circuit and increasing the motor's torque constant.

[0006]

However, in the spindle motor having the above structure, the decrease in starting torque due to a decrease in drive voltage is dealt with by increasing the magnetic flux in the magnetic circuit, so the rotational speed is sacrificed. That is, by increasing the magnetic flux, the back electromotive force constant also increases, so the maximum rotation speed becomes small, making it impossible to obtain the desired rotation speed.

Furthermore, the torque at the desired rotational speed becomes small, making constant speed control difficult. Conventionally, spindle motors have been designed based on a compromise between starting torque and rotational speed, resulting in the problem that a satisfactory starting torque cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a spindle motor that can achieve both high starting torque and high rotation.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a spindle motor including a stator and a rotor disposed outside the stator. A spring that is held movable in a direction perpendicular to the rotation direction is
It is installed on the rotor.

0010

[Operation] According to the present invention, since the spindle motor is configured as described above, the magnet attached to the rotor moves in a direction perpendicular to the rotational direction of the rotor due to the rotation of the motor, and the distance between the stator and the magnet is reduced. becomes smaller.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a spindle motor showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line A-A of the same, showing a hub 1, a magnet assembly 2, a spring 3, a stopper 6, and a rotor 10. and stator 20
The stator core 4 and the coil 5 are provided. The magnet assembly 2 is composed of a rotor frame 2a and a rotor magnet 2b, and is attached to the hub 1 by a spring 3 so as to be movable in the radial direction. Note that the stopper 6 defines the maximum displacement of the magnet assembly 2 in the radial direction, and the support member 7 supports the magnet assembly 2 in the vertical direction.

Next, the operation of the embodiment of the present invention will be explained. In FIG. 1, centrifugal force acts on the magnet assembly 2 as the hub 1 rotates. Now, the centrifugal force is F0
, the mass of one magnet assembly 2 is m, the distance from the center of rotation is r, and the rotational angular velocity is ω, then F0 =
It becomes mrω2. Further, if the spring constant of the spring 3 is k, the amount of displacement is x, and the force with which the spring 3 presses the magnet assembly 2 due to the displacement is F1, then F1 = kx. F0
=F1, so x=mrω2/k holds true.

From this equation, it can be seen that the displacement x increases as the rotational angular velocity ω increases, that is, the distance between the rotor magnet 2b and the stator core 4 (hereinafter referred to as gap length) δ
It can be seen that becomes larger. On the other hand, rotor magnet 2
The magnetic flux density Bg in the air gap between b and the stator core 4 is inversely proportional to the air gap length δ, that is, when δ→large, Bg
→ small, and when δ → small, Bg → large holds true. Therefore, the relationship between ω and Bg holds that when ω→large, B→small, and when ω→small, Bg→large.

By the way, if the torque generated by the motor is T, the torque constant is KT, and the input current is I, then T=KT.
Becomes I. Also, if the maximum rotation speed of the motor is ωmax, the back electromotive force constant is KE, and the input voltage is V, then ωmax
=V/KE. The torque constant KT and the back electromotive force constant KE are both the magnetic flux density Bg in the air gap.
is proportional to. Therefore, it can be seen that in order to obtain high torque, the gap length δ should be made small, and in order to obtain high rotation, the gap length δ should be made large.

FIG. 3 is an explanatory diagram showing the state of the spindle motor according to the embodiment of the present invention when it is stopped, and FIG. 4 is an explanatory diagram showing the state when it rotates at high speed. When stopped, as shown in FIG. 3, no centrifugal force acts on the magnet assembly 2, so the spring 3 is not displaced and the gap length is minimized. Therefore, high starting torque can be obtained. Furthermore, during rotation, as shown in Figure 3, centrifugal force acts on the magnet assembly 2, displacing the spring 3, so as the rotation speed increases, the gap length increases, making high-speed rotation possible. .

It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0017]

[Effects of the Invention] As described above in detail, according to the present invention, the magnets attached to the rotor move in a direction perpendicular to the rotational direction of the rotor due to the rotation of the motor, and the distance between the stator and the magnets is reduced. Therefore, it is possible to achieve both high starting torque and high rotation speed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a spindle motor showing an embodiment of the present invention.

[Fig. 2] A- of a spindle motor showing an embodiment of the present invention.
It is an A sectional view.

FIG. 3 is an explanatory diagram showing a state of the spindle motor of the present invention when it is stopped.

FIG. 4 is an explanatory diagram showing a state of the spindle motor of the present invention during high speed rotation.

FIG. 5 is a sectional view taken along line AA of a conventional spindle motor.

[Explanation of symbols]

1 Hub 2 Magnet assembly 2a Rotor frame 2b Rotor magnet 3 Spring 4 Stator core 5 Coil 6 Stopper 7 Support member

Claims (1)

[Claims] 1. A spindle motor comprising a stator and a rotor disposed outside the stator, comprising a magnet facing the stator and a spring movably holding the magnet in a direction perpendicular to the rotational direction of the rotor. , a spindle motor characterized in that the rotor is provided with the rotor.