KR100238034B1 - Journal bearing apparatus - Google Patents

Abstract

The present invention improves the shape of the inner surface of the sleeve supporting the shaft in order to prevent the whirling phenomenon occurring in the shaft rotating at high speed to vary the gap interval between the inner surface of the sleeve and the shaft at regular intervals, thereby generating on the shaft The present invention relates to a journal bearing device that reduces production costs by eliminating whirling.

According to the present invention includes a shaft having a journal portion formed in a cylindrical shape, and a journal support member in which the journal portion is inserted to support the journal, wherein the journal support member is bisected into a circle to form two semicircles, A semicircle offset shaft hole having a cross-sectional shape in which the center of the semicircle and the center of the other semicircle are staggered by a predetermined interval is formed.

Description

Journal bearing device {JOURNAL BEARING APPARATUS}

The present invention relates to a journal bearing device, and more particularly, in order to prevent the whirling phenomenon occurring in the shaft rotating at high speed, so that the shape of any one of the inner surface or the shaft of the sleeve supporting the shaft is changed regularly The present invention relates to a journal bearing device in which a gap between a shaft and an inner surface of a sleeve is varied at regular intervals according to the inner surface of the sleeve or the shape of the shaft, thereby eliminating a whirling phenomenon occurring on the shaft and reducing production costs.

Recently, as is well known, the head drive of a video tape recorder, the scanning motor which is a polygon mirror drive of a laser printer, the camcorder drive motor, etc. are gradually increasing in size and size, and these drives are precise and stable. Fluid bearings are mainly used because they require a bearing that can rotate at high speed.

Such fluid bearings have been developed in a variety of dynamic pressure generating grooves such as spiral dynamic pressure generating grooves and herringbone shaped dynamic pressure generating grooves to minimize frictional forces that hinder rotation of the shaft by radial and thrust loads.

These various dynamic pressure generating grooves are cavitation caused by the nonlinear processing of the shaft, the density imbalance of the shaft, and the failure of the fluid film between the shaft and the supporting members supporting the shaft, even if the shaft is precisely machined. It is used for the purpose of preventing the whirling phenomenon, which is a rotational instability phenomenon caused by the shaft.

1 is a perspective view illustrating a laser scanning unit used in a laser printer to which a fluid bearing device having such a dynamic pressure generating groove is applied.

1, a semiconductor laser diode 10 for emitting a laser beam used as a light source, a collimator lens 20 for making the laser beam emitted from the semiconductor laser diode 10 into parallel light with respect to an optical axis; And a cylindrical lens 30 which makes the parallel light through the collimator lens 20 into the linear light in the horizontal direction with respect to the sub-scanning direction, and the linear linear light through the cylindrical lens 30 in the horizontal direction. A polygon mirror 40 is formed which moves by scanning.

In addition, the scanning motor 50 for rotating the polygon mirror 40 at an isoline velocity, and has a constant negative refractive index with respect to the optical axis and polarized light of the isoline velocity through the polygon mirror 40 in the main scanning direction An imaging lens group 70 for correcting spherical aberration to focus on the scanning surface, and a laser beam through the imaging lens group 70 is vertically reflected to form a dot on the surface of the photosensitive drum 60 that is an imaging surface. An imaging reflection mirror 75 for forming an image, a horizontal synchronous mirror 80 for reflecting a laser beam through the imaging lens group 70 in a horizontal direction, and a laser reflected from the horizontal synchronous mirror 80 It consists of an optical sensor 90 for receiving and synchronizing the beam.

2 is a cross-sectional view taken along line AA ′ of the scanning motor 50 of FIG. 1.

The centrifugal force acting on the shaft by the high speed rotational rotation of the shaft 30, and the shaft 30 on either side of the inner surface of the sleeve 20 or the shaft 30 to which the journal of the shaft 30 is fitted in the scanning motor. And the shaft 30 is in an unstable rotation state because the discontinuous fluid pressure is generated by the cavitation caused by the fluid not being completely filled and partially filled in the gap between the sleeve and the sleeve 20). Whirring will occur.

Accordingly, since the shaft 30 revolves very unstable in the sleeve 20 by the whirling phenomenon, the shaft 30 prevents a whirling phenomenon that causes vibration and vibration in the shaft 30, and at the same time, the shaft 30 ) And the first dynamic pressure generating portion 35 which is a herringbone-shaped groove having a bent portion 80 bent at a predetermined angle to generate a fluid pressure for contactlessly rotating the inner surface of the sleeve 20 in a predetermined interval. Formed.

3 is a cross-sectional view taken along line BB ′ of FIG. 2.

The herringbone-shaped first dynamic pressure generating groove 35 is formed in a plurality of circularly arranged along the circumference of the inner surface or the shaft 30 of the sleeve 20 at equal intervals, and the self-weight and According to the load, the groove area and the number of the first dynamic pressure generating grooves 35 are determined.

In addition, the first dynamic pressure generating groove 35 is formed with a first fluid pressure generating portion 40 and a second fluid pressure generating portion 45 for introducing a fluid into the bent portion 80. The dynamic pressure generating groove 35 is formed to a depth of several micrometers by processes such as turning, etching, and CVD deposition.

On the other hand, the thrust bearing 50 in which a spiral-shaped second dynamic pressure generating groove 50a for supporting the thrust load acting in the vertical direction of the shaft 30 and generating the fluid pressure for floating the shaft 30 is formed. ) Supports one end of the shaft 30.

The aforementioned shaft 30 is press-fitted with a hub 70 for seating the polygon mirror 85, and the hub 70 is provided with a motor rotor 60 and spaced apart from the motor rotor 60 by a predetermined distance. Where a motor stator (not shown) is formed, the polygon mirror 85 is rotated by the motor rotor and the motor stator.

The polygon mirror driving apparatus using the conventional fluid bearing configured as described above is as follows.

First, when power is applied to the motor rotor and the motor stator and the motor rotor starts to rotate, the polygon mirror 85 pressed into the hub 70 gradually rotates while increasing the angular acceleration at a time when the angular acceleration is zero. After reaching the number (7000-20000 rpm), it rotates at constant speed.

At this time, the rotation of the shaft 30 in the journal outer peripheral surface of the shaft surrounded by the sleeve 20 of the shaft 30 by the rotation of the shaft 30 and the journal end that is in contact with the thrust bearing 50. Vortex having the same direction as the direction is formed, the vortex formed at this time flows into the first fluid pressure generating portion 40 and the second fluid pressure generating portion 45 of the first dynamic pressure generating groove (35).

At this time, the fluid supplied to the first dynamic pressure generating groove 35 is the fluid is collected in the bent portion 80 shows a tendency of the bent secondary curve having a vertex (P _max ) as shown in the graph of FIG. The fluid 30 is spaced apart from the sleeve 20 and the thrust bearing 50 by a predetermined pressure to rotate with a minimum frictional force.

However, since the machining process of the first dynamic pressure generating groove formed in the conventional journal fluid bearing has to be processed with high precision while being processed in multiple stages, the machining process is difficult and the production cost increases accordingly.

In addition, when the first dynamic pressure generating groove is not formed due to such a problem, vibration and shaking occur in the shaft due to the whirling phenomenon described above, thereby degrading the rotational performance of the shaft.

Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is not to form a dynamic pressure generating groove on either side of the shaft support member for supporting the shaft, but instead of the sleeve for supporting the shaft or shaft. It is to provide a control board bearing device to prevent any whirling phenomenon by processing any one side in the shape of 2 arc, 3 arc, 4 arc, semi-circle offset.

1 is a perspective view showing a conventional laser scanning unit.

2 is a cross-sectional view taken along line AA ′ of the scanning motor of FIG. 1.

3 is a sectional view taken along the line B-B 'of FIG.

Figure 4 is a cross-sectional view of the journal and the sleeve portion of the scanning motor according to the present invention in a transverse direction.

5 is a cross-sectional view showing another embodiment of the present invention.

Figure 6 is a cross-sectional view showing another embodiment of the present invention.

Figure 7 is a cross-sectional view showing another embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

30a: shaft 30b: sleeve

A: Long axis B: Short axis

The journal bearing device for achieving the object of the present invention includes a journal portion formed at one end of the shaft having a cylindrical shape, the journal support member is inserted into the journal support to support the journal, journal support The member is bisected to form two semicircles, and a semicircle offset shaft hole having a cross-sectional shape in which the center of one semicircle and the center of the other semicircle are staggered by a predetermined interval is formed.

Hereinafter, with reference to the accompanying drawings, the journal bearing device of the present invention will be described.

Figure 4 is a cross-sectional view of the journal and the sleeve portion of the journal bearing device of the present invention in a cross-sectional view as an embodiment of the reference numeral 30a is a shaft having a predetermined diameter and 30b to support the shaft (30a) It is a cylindrical sleeve 30b into which the journal portion of the shaft 30 is fitted.

A cross section of the inner surface of the sleeve 30b is a lemon shape (lemon bore) having a long axis (A) and a short axis (B), and the difference between the length of the axis (B) and the diameter of the axis (30a) If D is the difference between the major axis and the diameter of the shaft 30a as E, the length relationship between D and E is processed so that D <E.

That is, the dynamic pressure generated at D, which is a gap formed between the shaft 30a and the short axis B, is greater than the dynamic pressure generated at the shaft 30a and the long axis A, and the shaft 30a is formed at the short axis B. The whirling phenomenon at the high speed of rotation of the shaft 30a is reduced because the shaft 30a is constrained in the two portions in this way, acting as if it is supported in two portions.

FIG. 5 shows a three-circle journal bearing that acts as a further reduction of whirling and supporting the shaft 30a in three parts than a two-circle journal bearing, where three circles having the same diameter may overlap. In this case, the intersection points (G, E, F) of three points occur in the overlapping part. In this case, the line segment connecting the three points (G, E, F) will be referred to as three arcs. The generated closed curve becomes the inner surface of the sleeve 30b. The shaft 30a having a predetermined diameter is fitted to the inner surface of the sleeve 30b.

At this time, the gap formed between the shaft 30a and the inner surface of the sleeve 30b is the largest in the G, E, F portion of the sleeve 30b, and the midpoint portions g, e, In f), the gap formed by the shaft 30a is the smallest so that the shaft 30a generates the greatest dynamic pressure in the gap formed with the shaft 30a the smallest, so that the shaft 30a is substantially the same as that supported by the three parts. You get

At this time, the shaft 30a is constrained at three points in the same manner as the two circular arcs, thereby preventing a whirling phenomenon occurring during rotation.

6 and 7 are cross-sectional views each showing a four-circle journal bearing and a semi-circle offset journal bearing. In FIG. 6, four corners formed by overlapping four circles to support the shaft 30a at four portions. In the case where the closed curve formed by connecting (H, I, J, K) is formed as the inner side of the sleeve 30b, the clearance gap formed with the shaft 30a is the largest in H, I, J, K and h. Since it is the smallest at, i, j, k, the axis 30a is actually constrained at four portions of h, i, j, k to suppress the whirling phenomenon.

FIG. 7 shows that a gap formed between the inner surface of the sleeve 30b and the shaft 30a formed by arranging the centers of the semicircles having a bisected shape of the circle alternately left and right is constant according to the inner surface shape of the sleeve 30b. An embodiment in which a whirling phenomenon occurring on the shaft 30a is prevented by varying the period is shown.

As described in detail above, the gap between the inner surface of the shaft and the sleeve is formed by processing the inner surface of the sleeve into 2 arcs, 3 arcs, 4 arcs, semicircle offsets, and the like. By constraining the shaft at multiple points by changing it according to the shape, it is possible to prevent whirling occurring on the shaft and to increase rotational stability of the shaft.

In the present invention, in order to periodically change the gap between the shaft and the shaft support member, the shaft support member is processed into two circular arcs, three circular arcs, four circular arcs, a semicircle offset, and the like. , 3 arc, 4 arc, and semi-circle offset may be the same effect as the above embodiment.

Claims (1)

A shaft having a journal portion formed in a cylindrical shape; The journal portion is inserted to include a journal support member for supporting the journal, The journal support member is formed by dividing a circle into two semicircles, and a semicircle offset shaft hole having a cross-sectional shape in which the center of one semicircle and the center of the other semicircle are staggered by a predetermined interval. Journal bearing device.

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