KR100207987B1 - Hemispherical bearing system using magnetic material - Google Patents

Abstract

The present invention relates to a hemispherical bearing device using a magnetic material. According to the present invention, a fixed shaft fixed to a lower housing and a hemispherical surface are forcibly fitted to the fixed shaft so as to face each other and have a spiral shape on the hemisphere. A hemisphere in which a dynamic pressure generating groove is formed, a bush in which a groove having a shape equivalent to that of the hemisphere fitted to the fixed shaft and the fixed shaft is formed, and a first permanent magnet formed on an outer circumferential surface of the bushing; A second permanent magnet is formed in the lower housing spaced apart from the first permanent magnet by a predetermined gap, so that the first permanent magnet and the second permanent magnet are repulsed with each other.

Description

Hemisphere bearing device using magnetic material

The present invention relates to a hemisphere bearing device using a magnetic material, and more particularly, to a hemisphere bearing device using a magnetic material provided with a pair or two pairs of permanent magnets when mutual repulsion occurs at a predetermined position of the hemisphere bearing device. .

As is well known in recent years, the driving motors required for driving various devices due to the rapid development of the electrical and electronics industry, for example, the polygon mirror drive of a laser printer, the spindle motor of a hard disk, the head of a VCR Drive motors require high-precision, high-speed rotational performance without shaft shaking or shaft shaking in order to search, store, and reproduce more data in a shorter time due to the characteristics of the device.

Accordingly, research is being conducted on various types of bearing devices that enable such motor rotation along with the development of a drive motor that stably rotates at high speed while suppressing shaft shake and shaft vibration of the drive motor.

As a kind of bearing device, a fluid bearing device that has been proven to have high speed and high precision stability is widely used. Such a fluid bearing device is a hemispherical bearing device and a conical bearing device that simultaneously support radial and thrust loads. Is being used.

Among these fluid bearing devices, a polygon mirror driving device of a laser printer to which a hemispherical bearing device, which supports radial and thrust loads at the same time and is suitable for ultra-high rotation, is described with reference to FIG. 1. Same as

The polygon mirror driving device of the laser printer to which the hemispherical bearing device is applied has a hemisphere 30 (35) having a fixed shaft (20), which is the center of rotation of the polygon mirror (10), and a hemispherical surface pressed into the fixed shaft (20). ) And bushings 40 supporting radial and thrust loads of hemispheres 30 and 35, motors 50 and 55 as driving devices, hubs 60, upper housings 75 and lower housings ( 70).

The lower housing 70 is press-fitted with a fixed shaft 20 to which hemispheres 30 and 35 are fixed, and a hub such that a polygon mirror 10 and a motor rotor 55 are installed on the outer circumferential surface of the bushing 40. 60 is press-fitted, and as a result, the hemispheres 30 and 35 and the fixed shaft 20 are fixed and the bushing 40 is rotatable about the fixed shaft 20, and the motor rotor ( A motor stator 50 is formed spaced apart from the predetermined interval 55.

On the other hand, the bushing 40 for supporting the radial load and the thrust load of the hemispheres 30 and 35 has a through hole with a diameter larger than the fixed shaft 20 at the center of the solid cylindrical rod having a predetermined diameter. After forming, hemisphere grooves 30a and 30b which are the same as the curvature of the pre-machined hemispheres 30 and 35 are formed at both ends of the rod, and the hemispheres 30 and 35 and The spacer 40a for adjusting the gap gap between the hemisphere grooves 30a and 30b is inserted.

Referring to the accompanying drawings, the action of the polygon mirror driving device to which the hemisphere bearing device configured as described above will be described.

First, when power is applied to the motor stator 55 and the motor rotor 50 and the bushing 40 starts to rotate, the lower hemisphere groove 30a of the bushing 40 is gravityd by a load applied to the bushing 40. It descends in the direction and is in close contact with the lower hemisphere 30 without a gap.

When the lower hemisphere 30 is in close contact with the lower hemisphere groove 30a, and the upper hemisphere 35 has a gap of several μm with the upper hemisphere groove 30b, when the bushing 40 rotates, Dynamic pressure generated by the fluid flowing into the spiral dynamic pressure generating groove (not shown) formed in the upper and lower hemispheres 30 and 35 has a lower gap between the upper hemisphere groove 30b and the upper hemisphere 35. Since greater than the gap between the 30 and the lower hemisphere groove 30a, the dynamic pressure generated in the lower portion is increased, so that the lower hemisphere groove 30a rises from the lower hemisphere 30 by the generated dynamic pressure.

However, as the bushing 40 rises from the lower hemisphere 30, the gap gap between the lower hemisphere 30 and the lower hemisphere groove 30a becomes wider, and conversely, the gap gap between the upper hemisphere 35 and the upper hemisphere groove 30b is increased. As it gradually narrows, the dynamic pressure formed by the upper hemisphere 35 and the upper hemisphere groove 30b tends to increase gradually.

In this way, the bushing 40 formed between the pair of hemispheres varies the gap spacing up and down little by little, and thus, the difference between the dynamic pressure generated in the lower hemisphere 30 and the dynamic pressure generated in the upper hemisphere 35 is the The bushing 40 rotates in equilibrium at a gap coinciding with its own weight.

However, such a conventional hemisphere bearing device is in such a state because two hemispheres, one of hemisphere grooves and hemisphere grooves are in close contact with each other due to the self-weight of the polygon mirror and the bushing motor in the stationary state. Due to the rotation of the hemisphere groove of the bushing, the hemisphere and the hemisphere groove that are in close contact with each other due to the dynamic pressure generated in the hemisphere require a predetermined time interval to be spaced from each other. Rotating in a close contact state causes wear of the hemisphere and the hemisphere groove, thereby reducing the life of the hemisphere bearing device.

Accordingly, the present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a first permanent magnet in a bushing, and a second permanent magnet in a lower housing spaced a predetermined distance from the first permanent magnet. By using the repulsive force of the first permanent magnet and the second permanent magnet to offset the load applied to the bushing by the repulsive force to reduce the time the bushing rises from the hemisphere by the load reduction applied to the bushing by friction An object of the present invention is to provide a hemispherical bearing device using a magnetic material which prevents the bearing device from shortening its life.

1 is a cross-sectional view showing a polygon mirror driving device of a laser printer to which a conventional hemisphere bearing device is applied.

Figure 2 is a cross-sectional view showing a polygon mirror driving device of a laser printer to which the hemisphere bearing device according to the present invention is applied.

3 is a view showing another embodiment according to the present invention.

Explanation of symbols for the main parts of the drawings

30,35: hemisphere 30a, 30b: hemisphere groove

100: first permanent magnet 200: second permanent magnet

300: third permanent magnet 400: fourth permanent magnet

The hemispherical bearing device using a magnetic material for achieving the object of the present invention comprises a fixed shaft fixed to the lower housing;

A hemisphere which is fitted to the fixed shaft so that the hemispheres face each other and a spiral-like dynamic pressure generating groove is formed in the hemisphere;

A bushing in which a groove having a shape equivalent to that of the hemisphere fitted to the fixed shaft and the fixed shaft is formed;

A first permanent magnet formed on an outer circumferential surface of the bushing, and a second permanent magnet formed in a lower housing spaced apart from the first permanent magnet by a predetermined gap so that the first permanent magnet and the second permanent magnet repel each other; It features.

Hereinafter, a polygon mirror driving device of a laser printer to which a hemisphere bearing device using the magnetic material of the present invention is applied will be described with reference to the accompanying drawings.

The polygon mirror driving apparatus is a polygon mirror 10 for deflecting a laser beam to a photosensitive drum (not shown) and a hemispherical bearing device 20, 30 for ultra-fast rotation of the polygon mirror 10 with minimal friction. 35 and 40, rotational force generating devices 50 and 55 coupled with the hemisphere bearing device to generate rotational force, and a lower housing (fixed support; 70) and an upper housing (fixed) to allow the components to be seated. A support portion 75).

The polygon mirror 10 has a through hole having a predetermined diameter, and the through hole of the polygon mirror 10 is coupled with the hub 60 again, and the hub 60 has two different diameters. The cylinders 60a and 60b are joined to each other, and the first cylinder 60a having the smaller diameter is formed to fit the through-hole of the polygon mirror 10, and the second cylinder has the larger diameter on the other side. The groove 60c of a predetermined diameter and a predetermined depth is dug into the cylinder 60b.

The bushing 40 is again coupled to the second cylinder 60b of the hub 60. The bushing 40 has a cylindrical shape having a predetermined height, and its diameter is slightly larger than that of the groove 60c. It has a diameter that fits tightly.

In addition, a through hole having a predetermined diameter is formed through the centers of both ends of the bushing 40, and the through hole is formed to have a diameter slightly larger than the diameter of the shaft 20 fixed to the lower housing 70. .

Both ends of the bushing 40, the hemispheres face each other again, hemisphere grooves 30a having a shape similar to the hemispheres 30 and 35 having a spiral-like dynamic pressure generating groove (not shown) formed on the hemispheres. ) And 30b are formed.

In addition, the hemisphere grooves 30a and 30b formed in the bushing 40 and the hemispheres 30 and 35 press-fitted into the shaft 20 are similar in shape to the hemisphere grooves of the bushing 40. When the hemispheres 30 and 35 are coupled to the 30a and 30b in close contact with each other, the gap between the bushings 40 and the hemispheres 30 and 35 does not form a gap for forming a fluid pressure. The fluid bearing will lose its function.

Therefore, for this reason, an appropriate gap is required between the bushing 40 and the hemispheres 30 and 35, and the through hole of the bushing 40 has a ring-shaped spacer having a precise height, a predetermined inner diameter, and an outer diameter ( 40a is fitted to maintain a predetermined gap between the hemispheres 30 and 35 and the bushing 40. That is, the lower hemisphere 30 and the lower hemisphere groove 30a are completely in contact by the action of gravity among the hemispheres 30, 35 and the upper and lower hemisphere grooves 30a, 30b formed as a pair. The upper hemisphere 35 is in a state of forming a gap of several micrometers with the upper hemisphere groove 30b.

A motor rotor 50 is formed on the outer circumferential surface of the bushing 40 formed as described above, and a predetermined position of the lower housing 70 mentioned above by the motor stator 55 is spaced apart from the motor rotor 50 by a predetermined distance. Installed in

In addition, a donut-shaped first permanent magnet 100 is attached to the outer circumferential surface of the bushing 40 in addition to the motor rotor 50 and the motor stator 55, so that the first permanent magnet 100 has a magnetic field. Two polar plates having two polarities, that is, an N pole and an S pole are attached to each other.

The second permanent magnet having the same shape and the same magnetic flux density as the first permanent magnet 100 may be formed in the lower housing 70 spaced apart from the first permanent magnet 100 formed on the outer circumferential surface of the bushing 40. 200 is formed, and the second permanent magnet 200 is also formed by attaching two polar plates.

The polar plates of the first permanent magnet 100 and the second permanent magnet 200 formed as described above face the polar plates having the same polarity to each other, so that the first permanent magnet 100 and the second permanent magnet 200 are the same. Repulsion is caused by the polar plates.

Referring to the accompanying drawings, the action of the hemisphere bearing device using the magnetic material of the present invention configured as described above is as follows.

First, in response to the magnetic flux density of the first permanent magnet 100 formed on the outer circumferential surface of the bushing 40 and the second permanent magnet 200 formed on the lower housing 70, Repulsive force is generated in the second permanent magnet 200.

In addition, since the second permanent magnet 200 is in a fixed state, the first permanent magnet 100 may vertically move in the same direction as the moving direction of the bushing 40 so that the first permanent magnet 100 may be moved. And the repulsive force generated by the second permanent magnet 200 acts against the self-weight of the bushing 40 and the load in the direction of gravity generated by the bushing 40 such as the motor 50, 55, the polygon mirror 10, and the like. do.

Accordingly, the load in the gravity direction is canceled by the repulsive force of the first permanent magnet 100 and the second permanent magnet 200 so that the load in the gravity direction is reduced.

As such, when power is applied to the motors 50 and 55 while the load of the bushing 40 is reduced, and the motor 50 starts to rotate, spiral dynamic pressure generating grooves formed in the hemispheres 30 and 35 ( A predetermined fluid flows into the hemisphere 30 and the hemisphere grooves 30a and 30b generate a predetermined fluid pressure.

At this time, the magnitude of the fluid pressure generated between the hemispheres 30 and 35 and the hemisphere grooves 30a and 30b is increased in proportion to the rotational speed of the bushing 40 and is lower than the magnitude of the magnetic weight applied to the bushing 40. When the magnitude of the fluid pressure generated between the hemisphere 30 and the lower hemisphere groove 30a increases, the hemisphere groove 30b of the bushing 40 is spaced apart from the hemisphere 30 to maintain a predetermined gap. The time taken for the injury from the hemisphere 30 to be defined as the injury time.

As mentioned earlier, the lift time is proportional to the magnitude of the load on the bushing 40 when the revolutions are the same and inversely proportional to the acceleration of rotation when the load on the bushing 40 is constant. That is, to increase the time of injury, increase the weight of the bushing 40, or to reduce the rotational acceleration of the bushing 40 and reduce the time of injury, reduce the weight of the weight of the bushing 40, or bushing 40 Increase the rotational acceleration.

According to the present invention, the magnitude of the fluid pressure generated in the hemispheres 30 and 35 and the hemisphere grooves 30a and 30b is constant (the number of revolutions is constant), but the first permanent magnet 100 and the second permanent magnet 200 are The load applied to the bushing 40 is reduced due to the repulsive force generated by), and as a result, the injury time is shortened, so that the hemisphere 30 and the hemisphere groove 30a are rotated in close contact with the hemisphere 30 and It is possible to prevent shortening of the life of the hemisphere bearing device due to wear of the hemisphere groove 30b.

3 is a view showing another embodiment according to the present invention, the hemispherical bearing device using a magnetic material according to the present invention is a third permanent magnet 300 in the cylinder of the small diameter of the hub 60 of FIG. The fourth permanent magnet 400 is installed at a position spaced apart from the third permanent magnet 300 by a predetermined distance, and the fourth permanent magnet 400 is fixedly supported by the upper housing 75.

As described above, by installing a pair of permanent magnets having a predetermined magnetic flux density in the hemispherical bearing device to reduce the load on the bushing to reduce the floating time of the bushing away from the hemisphere to reduce wear of the hemisphere and hemisphere There is an effect of preventing the reduction of the life of the hemispherical bearing device.

Claims (7)

A fixed shaft fixed to the lower housing; A hemisphere which is fitted to the fixed shaft so that the hemispheres face each other and a spiral-like dynamic pressure generating groove is formed in the hemisphere; A bushing in which a groove having a shape equivalent to that of the hemisphere fitted to the fixed shaft and the fixed shaft is formed; A first permanent magnet formed on an outer circumferential surface of the bushing, and a second permanent magnet formed in a lower housing spaced apart from the first permanent magnet by a predetermined gap so that the first permanent magnet and the second permanent magnet repel each other; Hemispherical bearing device using a magnetic material characterized in that. The hemispherical bearing device using magnetic materials according to claim 1, wherein the first permanent magnet is formed of two polar plates, an N polar plate and an S polar plate. The hemispherical bearing device using magnetic materials according to claim 1, wherein the second permanent magnet is formed of two polar plates, an N polar plate and an S polar plate. The hemispherical bearing device using magnetic materials according to claim 2 or 3, wherein the first and second permanent magnets face the same polar plate. The hemispherical bearing device using magnetic materials according to claim 1, wherein a rotatable body is attached to the bushing. 6. The third permanent magnet of claim 5, wherein a third permanent magnet is formed on an upper surface of the rotating body, and a fourth permanent magnet is formed at a spaced distance from the third permanent magnet. Hemispherical bearing device using a magnetic material, characterized in that the magnet is to repel each other. The hemispherical bearing device using magnetic material according to claim 6, wherein the fourth permanent magnet is formed in an upper housing.

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