KR100222998B1 - A scanning motor equipped with a fluid bearing apparatus having an increased dynamic pressure generating area and a method for forming a dynamic pressure generator - Google Patents

Abstract

A method of forming a scanning motor and a dynamic pressure generating member having a fluid bearing device having increased dynamic pressure generating area is disclosed.

Dynamic pressure is eliminated by removing the spacer contact surface to compensate for the loss of dynamic pressure caused by the reduction of the dynamic pressure generation area by the spacer contact surface formed on the hemispherical dynamic pressure generating member for interposing the spacer in the hemispherical bearing device, which is one of the conventional fluid bearing devices. By allowing the area to be generated to increase in axial and radial loads, and furthermore by omitting the step of forming the spacer contact surface, the process procedure can be reduced to improve the performance of the fluid bearing device and increase productivity and productivity.

Description

Scanning motor and dynamic pressure generating member forming method having fluid bearing device with increased dynamic pressure generating area

The present invention relates to a scanning motor having a fluid bearing device having an increased dynamic pressure generating area, and more particularly, to a dynamic pressure generating area of a dynamic pressure generating member generating a predetermined dynamic pressure in a hemisphere bearing device applied to the scanning motor. The present invention relates to a dynamic pressure generating member having an increased axial rigidity and a radial rigidity and a method of forming the dynamic pressure generating member for mass production of the dynamic pressure generating member.

Recently, due to the rapid development of information and computer industry, drive motors required to drive various devices, such as scanning motor of laser printer, spindle motor of hard disk drive, head drive motor of VCR, etc. In order to perform a lot of data retrieval, storage, and playback in a short time, there is a demand for high-precision ultra-high speed rotation performance without shaft shaking or shaft shaking.

Accordingly, research has been conducted on various types of bearing devices that enable the driving motor to rotate as well as the development of the driving motor that stably rotates at high speed while suppressing shaft shaking and shaft vibration of the driving 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. Etc. are used.

Referring to the accompanying drawings, as an example, a configuration and an operation of a scanning motor to which a hemisphere bearing device having a characteristic capable of simultaneously supporting an axial load and a radial load among these fluid bearing devices is applied.

1 illustrates an example of a scanning motor to which a hemisphere bearing device having a conventional spacer is applied.

The hemispherical bearing device applied to the scanning motor 1 inserts a spacer 20 having a predetermined length in a cylindrical shape into a shaft 10 fixed to a plate-shaped lower bearing bracket 5, The amount of interference is largely suppressed so that the hemispherical surfaces of the hemispherical dynamic pressure generating members 30 and 40 having the spacer contact surfaces 20a formed on both ends thereof face each other.

In this way, the dynamic pressure generating members 30 and 40 fitted to the shaft 10 are cylindrical in shape and have a hemispherical groove having the same curvature as the dynamic pressure generating members 30 and 40 at both ends, and somewhat more than the shaft 10. It is large enough to support the bushing 50 having a through hole into which the spacer 20 is fitted and a hub 70 formed on the outer circumferential surface of the cylinder to protrude so that the polygon mirror 60, which is a rotating body, is seated.

In addition, the bushing 50 is provided with a donut-shaped thin plate 75, and a rotor bracket 80, which is a rotor, is attached to the plate 75, and a bearing bracket 5 spaced a predetermined distance from the rotor 80. ), A stator 85 is attached.

As the bushing 50 rotates in the hemispherical bearing device having a spacer applied to the conventional scanning motor 1 configured as described above, a predetermined fluid pressure is generated in the dynamic pressure generating members 30 and 40. This requires essentially a clearance between the hemisphere groove of the bushing 50 and the hemispherical surface of the dynamic pressure generating members 30 and 40, so that the spacer 20 has a hemisphere of the bushing 50. To form a gap between the groove and the dynamic pressure generating member 30, 40 must be processed with a very high precision.

In order to obtain such high precision, there is a problem that requires a lot of processing time and repetitive processing, and recently, a hemispherical bearing device without a spacer has been shown.

FIG. 2A illustrates a spacer-less hemisphere bearing device applied to a scanning motor, in which a spring 100 having a predetermined modulus of elasticity is interposed in place of the spacer in the hemispherical bearing of FIG. 1 and two dynamic pressure generating members 30 are provided. The lower dynamic pressure generating member 30 is inserted to slide up and down with respect to the shaft 10, and the upper dynamic pressure generating member 40 is fitted to have a large amount of interference with respect to the shaft 10. It is.

Here, when the lower dynamic pressure generating member 30 is pushed downward by the spring 100 and the clearance between the hemisphere grooves of the dynamic pressure generating members 30 and 40 and the bushing 50 reaches a predetermined gap, the lower dynamic pressure generating member The lower dynamic pressure generating member 30 is fixed to the fixing ring 110 so that the 30 does not generate any further displacement, so that the hemisphere bearing device can be smoothly operated without a long processing time and a spacer repeatedly processed precisely. will be.

Figure 2b is a cross-sectional view showing the hemispherical dynamic pressure generating member of Figure 1a as follows in more detail.

The pair of dynamic pressure generating members 30 and 40 has a hemispherical shape in which the diameter of the spherically processed sphere is equally divided into two, and the dynamic pressure generating members 30 and 40 are hemispherical dynamic pressure generating members 30 and 40. The first cut surface 30a, 40a which is a diameter portion of the first cut surface 30a, 40a, and the second cut surface cut parallel to the first cut surface 30a, 40a at a spaced distance from the first cut surface 30a, 40a. 30b) and 40b are formed, and this 2nd cut surface 30b and 40b becomes the spacer contact surface 20a mentioned above.

Here, the through holes 30c and 40c are formed by connecting the centers of the first cut surfaces 30a and 40a and the centers of the second cut surfaces 30b and 40b.

As mentioned above, the lower dynamic pressure generating member 30 of the dynamic pressure generating member 30 and 40 should be slidable about the shaft 10, so that the diameter of the through hole 30c of the lower dynamic pressure generating member 30 is the shaft ( It should be somewhat smaller than the diameter of 10).

At this time, the diameters of the second cut surfaces 30b and 40b are formed to be somewhat larger than the diameters of the through holes 30c, and the springs 100 are formed on the second cut surfaces 30b and 40b.

Here, the? BC formed by the arbitrary C ₁ point on the edge surfaces of the second cut surfaces 30b and 40b, the lower middle point B of the through hole 30c, and the upper middle point A, is the present embodiment. At 33 °.

However, the spacer contact surface 20a is formed in the hemispherical dynamic pressure generating member of such a hemispherical bearing device without the conventional spacer, as in the hemispherical bearing device with the conventional spacer. It functions as a simple seating system. By processing the spacer contact surface of the dynamic pressure generating member, the process procedure and the dynamic pressure generating area are reduced to generate maximum force acting in the axial direction and force acting on the radial load. There is a problem such as not letting.

Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to remove unnecessary portions of the dynamic pressure generating member of the spacer without a spacer, which is a fluid bearing device, to generate dynamic pressure of the dynamic pressure generating member. To maximize the capability and reduce unnecessary machining processes by machining unnecessary parts.

1 is a cross-sectional view showing a scanning motor to which a conventional hemisphere bearing device is applied.

2A is a cross-sectional view showing a scanning motor to which a hemisphere bearing device without a conventional spacer is applied;

2B is a cross-sectional view of the dynamic pressure generating member of FIG. 2A.

3 is a cross-sectional view showing a scanning motor to which the hemisphere bearing device according to the present invention is applied.

4 is a cross-sectional view showing the hemispherical dynamic pressure generating member of FIG.

Figure 5a is a graph of the performance test of the hemispherical dynamic pressure generating member of Figure 1 and the dynamic pressure generating member of Figure 4 under the same conditions,

5B is a graph of the results of FIG. 5A.

Figure 6 is a view showing a method for forming a hemispherical dynamic pressure generating member according to the present invention.

* Explanation of symbols for main parts of the drawings

210: polygon mirror 220: bushing

230: hub 260,270: dynamic pressure generating member

260a, 270a: first cut surface 260b, 270b: second cut surface

280: fixed shaft

The method of manufacturing a dynamic pressure generating member which is a core part of the hemispherical bearing device applied to the scanning motor for achieving the object of the present invention comprises the steps of forming a hollow having a predetermined diameter in the center of the cylindrical rod having a predetermined diameter; Filling a hollow with a predetermined resin, cutting the rod by the volume of the dynamic pressure generating member, forging the cut rod to form a sphere, and dividing the sphere into two to form a pair of hemispheres Characterized in that it comprises a.

Preferably the aforementioned resin is characterized in that it is a thermoplastic polyacetal resin resistant to abrasion.

Preferably, the forging-formed dynamic pressure generating member in a spherical shape is characterized in that the sphere polishing process by lapping, polishing.

A scanning motor having a fluid bearing device which increases the dynamic pressure generating area to which the dynamic pressure generating member formed by the above method is applied is spaced apart from an axis having a predetermined diameter, a first surface formed across the diameter and a predetermined distance from the first surface. A hemispherical dynamic pressure generating member having a second pressure surface formed in parallel with each other, the second surface facing each other and having a dynamic pressure generating groove formed thereon, a bushing rotating to receive the dynamic pressure generating member, the dynamic pressure generating member and the bushing; It includes a gap adjusting means for adjusting the gap of the, characterized in that it comprises a dynamic pressure generating device formed so that the diameter of the second surface is the same as the diameter of the shaft.

Preferably, the gap adjusting means includes an elastic member interposed between the second surfaces of the dynamic pressure generating member that is slidable with respect to the shaft to generate the pressing force, and a fixing member for limiting the displacement of the dynamic pressure generating member generated with respect to the shaft. It features.

Hereinafter, the manufacturing method of the dynamic pressure generating member of the hemispherical bearing device applied to the scanning motor and the scanning motor will be described in detail.

3 is a cross-sectional view showing a hemisphere bearing device applied to a scanning motor according to the present invention in one embodiment.

As shown in the figure, a flat polygonal smooth reflective mirror surface and a central portion are arranged to deflect the laser beam generated by the laser diode (not shown) or the surface emitting diode (not shown) to the imaging plane of the imaging body such as a photosensitive drum. The bushing 220 is coupled to the through hole of the polygon mirror 210 to rotate and support the polygon mirror 210 having the through hole at high speed.

When the bushing 220 is described in more detail, the bushing 220 is a hollow cylindrical shape having a predetermined height and a predetermined diameter, and a through hole is formed to penetrate both ends of the bushing 220 at a predetermined diameter.

In addition, hemispherical hemispherical grooves are formed at both ends of the bushing 220 to have a predetermined depth and a diameter smaller than the end diameter of the bushing 220, and the outer circumferential surface of the bushing 220 protrudes perpendicular to the bushing 220. Thus, the hub 230 supporting the aforementioned polygon mirror 210 is formed. Here, the rotor 240 for generating a rotational force in the bushing 220 to the lower side of the hub 230 is attached to the plate-shaped plate 245 in a donut shape, where the stator is spaced apart from the rotor 240 by a predetermined distance. 240a is formed.

On the other hand, a plate-shaped bearing bracket 250 for supporting the hemispherical bearing device as a whole is formed with a shaft hole having a certain diameter, the fixed shaft 280 of a diameter slightly larger than the shaft hole is fitted to the shaft hole.

In this way, the fixed-shaft 280 which is forcibly fitted to the bearing bracket 250 is forcibly fitted with the dynamic pressure generating member facing the hemisphere.

This will be described with reference to FIG. 4.

The pair of dynamic pressure generating members 260 and 270 has a hemispherical shape that is bisected by the diameter portion of the sphere processed with high spherical degree. The dynamic pressure generating members 260 and 270 have a hemispherical dynamic pressure generating member 260 and 270. The first cut surfaces 260a and 270a, which are diameter portions, and the second cut surfaces 260b cut parallel to the first cut surfaces 260a and 270a at a spaced distance from the first cut surfaces 260a and 270a. ) 270b is formed.

Through holes 260c such that the fixed shaft 280 slides in the central portion of the dynamic pressure generating members 260 and 270 having the first cut surfaces 260a and 270a and the second cut surfaces 260b and 270b. 270c is formed, of which the through hole 260c of the upper dynamic pressure generating member 260 is slightly smaller than the diameter of the fixed shaft 280 to be fitted to the fixed shaft 280, but the lower dynamic pressure generating member 270 has a through hole 270c which is somewhat larger than the fixed shaft 280 so as to be able to slide after being fitted to the fixed shaft 280.

Here, the important thing is that when the through hole 270c is formed in the lower dynamic pressure generating member 270, the second cut surface 270b having the same diameter as the through hole 270c is formed by the formation of the through hole 270c. In other words, this means that the diameter of the second cut surface 270b is the same as the diameter formed by the through hole 270c.

∠ ABC formed by an arbitrary C ₂ point on the edge surface of the through hole 270c, B as the lower middle point and A as the upper middle point of the through hole 270c forms 24 ° in this embodiment. have.

Here, the manufacturing method of the dynamic pressure generating member according to the present invention will be described with reference to FIG.

The dynamic pressure generating members 260 and 270 applied to the hemisphere bearing device are in contact with the hemisphere groove of the bushing 220 to simultaneously apply the axial force and the radial force acting from the bushing 220. It is a member that supports.

Such dynamic pressure generating members 260 and 270 are manufactured in a hemispherical shape to simultaneously support the axial load and the radial load in order to form such a hemispherical dynamic pressure generating member 260 and 270. First, as shown in FIG. 6A, a drilling operation is performed to create a hollow in a long rod made of stainless or aluminum, which is filled with a perforator such as a Mannesmann piercer.

Subsequently, as shown in FIG. 6B, a plastic-based thermoplastic resin (polyacetal resin) is filled in the hollow portion of the rod having the hollow hole, and then cooled and cured.

When the thermoplastic resin is cooled in this way, the volume of the hemisphere is calculated so that the rod filled with the thermoplastic resin is equal to the calculated volume of the hemisphere (at this time, an additional volume should be added in consideration of lapping, polishing, and fins). Cut the rod as shown.

As shown in FIG. 6D, a part of the cut rod is placed inside the mold where the spherical shape is carved again, and the mold is pressed from both sides to process the cut rod into a spherical shape.

As shown in Fig. 6E, the rod processed into a spherical shape is processed with a high spherical degree by lapping and polishing machines. The reason for lapping and polishing the spherical shape is to process the spherical shape rather than the hemispherical shape. This is because it is easy to do and the processing precision is high.

After heating and eluting the POM resin filled in the processed spherical shape, the bulb is bisected to be symmetrical to form a pair of dynamic pressure generating members 260 and 270, and then the lower dynamic pressure generating member 270. The portion to be) forms a through hole 270a to be somewhat larger than the diameter of the fixed shaft 280 mentioned above.

A spiral-shaped dynamic pressure generating groove (not shown) is formed on the surface of the dynamic pressure generating members 260 and 270 at a depth of several micrometers, and TiN (titanium nitride) and DLC (Diamond-Like-Carbon) coating layers and fixing rings, which are wear-resistant layers, are formed. Forming a fixed ring groove to be combined with (275) to produce a complete pair of dynamic pressure generating grooves (260, 270).

Returning, after inserting the lower dynamic pressure generating member 270 and the fixing ring 275 and the bushing described above into the fixed shaft 280 fit to the bearing bracket 250 by the method of FIG. A spring 290 having a predetermined modulus of elasticity is inserted.

Finally, the upper dynamic pressure generating member 260 and the fixing ring are inserted to adjust the fixing ring 275 so that the hemisphere groove of the bushing 230 and the upper and lower dynamic pressure generating member 260 maintain a predetermined gap.

As described above, the dynamic pressure generating members 260 and 270 of the hemispherical bearing device applied to the scanning motor of the present invention can be visually confirmed that the area in which dynamic pressure is generated is increased compared to the conventional dynamic pressure generating members. How much the performance of the member is increased compared to the conventional dynamic pressure generating member will be described with reference to Table 1, Table 2, and FIG.

Table 1 shows simulation data of the dynamic pressure generating member according to the present invention constructed and coupled as described above and the conventional dynamic pressure generating member having the second cut surfaces 30b and 40b (see FIG. 2b) under the same conditions. It is a table.

Conventional dynamic pressure generating member Dynamic pressure generating member of the present invention Clearance (㎛) 3.0 μm 3.0 μm Angular speed (rpm) 25,000 r.p.m 25,000 r.p.m ABC 33 ° 24 ° Dynamic pressure generating groove area same Etc same

In Table 1, the gap in the second row is the interval between the hemisphere groove and the dynamic pressure generating member when the bushing 220 rotates at a constant speed, and the angular velocity is the rotational speed per minute of the bushing 220.

사이의 각도 θ₁으로 도시되었다.ABC ₁ shown in FIG. 2B is connected to a line connecting any C ₁ on the circumferential edge of the second cut surfaces 30b and 40b with B as the lower midpoint of the through hole and A as the upper midpoint as described above. By line segment

The angle between is shown as θ ₁ .

사이의 θ₂를 나타내고 있다. 쉽게 알수 있듯이, ∠ABC 가 작아질수록 반구 표면적은 반비례로 증가하게 된다.ABC ₂ connects the line segments connecting A and B, which are the centers of both ends of the through hole 270c, with C ₂ , which is an arbitrary point on the edge surface of the through hole 270c that is the second cut surface 270b of FIG. 4.

Θ ₂ in between is shown. As can be readily seen, the hemispheric surface area increases inversely with decreasing ∠ABC.

<Table 2> is a result generated after experimenting the conventional dynamic pressure generating member and the dynamic pressure generating member according to the present invention under the same conditions.

Conventional dynamic pressure generating member Dynamic pressure generating member of the present invention Axial load 0.292 kg _f (A) 0.417 kg _f (I) Radial bearing load 0.195 kg _f (ⅰ) 0.228 kg _f (ii) Power consumption (w) 0.236 w (B) 0.246 w (A)

<Table 2> is the result of having performed the simulation on the conditions of <Table 1>.

As can be seen from the results of Table 2, the dynamic pressure generating member of the present invention is raised relative to the conventional dynamic pressure generating member in both the axial force, the raidal force and the power consumption.

Here, if the performance efficiency of the conventional dynamic pressure generating member and the dynamic pressure generating member of the present invention is calculated as follows.

100 × {(A-B) / B}

Yes;

Equation 1 compares the difference in power consumption between the conventional dynamic pressure generating member and the dynamic pressure generating member of the present invention. As can be seen from <Equation 1>, according to the dynamic pressure generating member of the present invention, the power consumption is increased by about 4.7% compared to the conventional dynamic pressure generating member.

This is because the surface area of the dynamic pressure generating member according to the present invention is increased and thus the friction area is also increased.

100 × {(I-A) / A}

Yes;

<Equation 2> is a result of comparing the axial load of the conventional dynamic pressure generating member and the dynamic pressure generating member of the present invention based on the result of <Table 2>, and shows that the axial support load is increased by about 42%. .

Here, most of the axial load and the radial load received by the dynamic pressure generating members 260 and 270 according to the present invention by the bushing 220 acts as the axial load and the radial load acts small. Therefore, this increase in the axial support load will soon increase the floating force of the bushing 220 to increase the rotational stability of the polygon mirror.

100 × {(ii-ⅰ) / ⅰ}

Yes;

<Equation 3> shows that, when the conventional dynamic pressure generating member and the dynamic pressure generating member of the present invention were simulated under the same conditions, the radial bearing load of the dynamic pressure generating member according to the present invention was increased by about 16.9% compared to the conventional dynamic pressure generating member. .

As described in detail above, the scanning motor to which the hemispherical bearing device with the spacer which is a fluid bearing device is removed is applied according to the reduction of the dynamic pressure generating area generated by the spacer contact surface formed in the hemispherical dynamic pressure generating member through the spacer. By eliminating the formation of the spacer contact surface to compensate for the dynamic pressure loss, the axial load and the radial load are increased, and the process procedure is reduced, thereby improving the performance of the fluid bearing device and increasing productivity and productivity.

Claims (5)

An axis having a predetermined diameter; Hemispherical dynamic pressure fitted to the shaft with the first surface formed across the diameter and the second surface formed parallel to be spaced apart from the first surface by a predetermined distance, and the second surface facing each other. A generating member; A bushing to receive and rotate the dynamic pressure generating member; It includes a gap adjusting means for adjusting the gap between the dynamic pressure generating member and the bushing, And a dynamic pressure generating device formed such that the diameter of the second surface is equal to the diameter of the shaft. 2. The method of claim 1, wherein the gap adjusting means includes an elastic member interposed between a second surface of the dynamic pressure generating member that is slidable about an axis to generate a pressing force, and a displacement of the dynamic pressure generating member generated about the shaft. Scanning motor comprising a fixing member. A method of forming a dynamic pressure generating member; Forming a hollow having a predetermined diameter at the center of the cylindrical rod having a predetermined diameter; Filling the hollow with a predetermined resin; Cutting the rod by the volume of the dynamic pressure generating member; Forging the cut rod to form a sphere; Dividing the sphere into two to form a pair of hemispheres. 4. The method of claim 3, wherein the resin is a thermoplastic polyacetal resin that is resistant to abrasion. 4. A method for forming a dynamic pressure generating member according to claim 3, wherein said dynamic pressure generating member forged formed into said spherical shape is sphere polished by lapping and polishing.

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