JPH02261925A - Dynamic pressure bearing device - Google Patents

Abstract

PURPOSE:To raised the bearing assembly accuracy, and maintain the high accuracy, and obtain the stable and fine characteristic by pressing-in a fixed plate between thick parts of a thrust plate to joint them, and making a top surface of the fixed plate abut to the inner surface of a thin part of the thrust plate. CONSTITUTION:A thrust plate 3 and a fixed plate 2b are formed so that a step part where a thickness of the inner periphery of the thrust plate 3 is thinner than a thickness of the periphery is jointed with a peripheral surface of a projecting part 2c of the fixed plate 2b and that the inner periphery of the thrust plate 3 abuts on the projecting part 2c of the fixed plate 2b. The projecting part 2c of the fixed plate 2 is thereby fitted in a lower recessed part of the thrust plate 3, and the two 2b, 3 are jointed. The step where a thickness of the inner periphery is thinner than a thickness of the periphery is provided opposite to a thrust bearing surface of the thrust plate 3, and the thin inner periphery abuts on the fixed plate 2b. The form accuracy of the thrust plate 3 is thereby facilitated, and the accuracy at the time of assembly is also facilitated, while a cost is made inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in Industry] The present invention relates to a hydrodynamic bearing device. This device is suitable as a bearing for a rotating unit used in a deflection scanning device used, for example, in a laser beam printer.

[Prior Art] The configuration of a conventional hydrodynamic bearing device is shown in FIG. 6, which includes a shaft 1 having a herringbone-shaped dip 10 carved on its radial surface, and a sleeve rotatably fitted to the shaft 1. 2 and a thrust plate 3 which is connected to the end face of the shaft 1 and the sleeve 2 and is held in the thrust direction, a shallow spiral groove is carved, and a lubricating fluid is filled between the shaft 1, the sleeve 2, and the thrust plate 3. ing. When the shaft 1 rotates, lubricating fluid flows through these gaps. Therefore, on the radial surface, pressure is generated in the radial direction by the herringbone-shaped shallow groove 10, resulting in a non-contact state. Similarly, pressure is generated on the thrust surface by the spiral shallow groove 11, and the shaft is supported without contact. Further, the thrust plate 3 is provided with a hole 7 at the center, a hole 8 at the periphery, and a groove 9 through which the holes 7 and 8 communicate. This causes the lubricating fluid to circulate around the thrust plate. This makes it possible to prevent the generation of negative pressure on the outer peripheral side of the thrust bearing forming portion and to diffuse heat.

Note that a recess 5 is provided on the open end side of the sleeve 2 (upper end side in the figure), and at a position further on the open side of the recess 5, the rotating shaft 1
A shallow groove 6 is provided in which fluid flows in the direction of the thrust bearing, and the structure prevents lubricating fluid from scattering.

Furthermore, in order to stabilize the floating characteristics, the recess (shallow groove 1)
In some cases, a small diameter hole is provided near the position corresponding to the position between the shallow groove 6 and the shallow groove 6.

[Problems to be Solved by the Invention] However, in the conventional example described above, when the thrust plate 3 is made of metal, machining such as cutting is required, and the groove footing is insufficient in terms of accuracy. It is possible, but the cost will be high. In addition, when molding is performed using a resin material (polyacetal, polycarbonate, PPS, etc.), the shape of the thrust pressure generating part becomes wavy or concave due to contraction of the resin after molding, resulting in the accuracy of the thrust plate 3 itself. Guarantees become difficult. Furthermore, it is difficult to guarantee precision during assembly, the contact points are unstable when the system is stationary, the friction torque may increase during startup, and there is a high possibility that wear will occur due to uneven contact. Furthermore, even during rotation, the ability to generate thrust pressure is reduced, resulting in unstable bearing characteristics.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a hydrodynamic bearing device that can improve bearing assembly accuracy, maintain high precision, and provide stable and good characteristics.

[Means and effects for solving the problem] According to the present invention, a step is provided on the side opposite to the thrust bearing surface of the thrust plate such that the wall thickness of the inner circumference is thinner than the wall thickness of the outer circumference. By configuring the thin inner periphery of the thrust plate to abut against the fixed plate, it is easier to achieve shape accuracy of the thrust plate, it is easier to achieve accuracy during assembly, and the cost is also lower. .

[Embodiment] Figure 's1 is a drawing showing an embodiment of the present invention. 6th
Components that are the same as those in the figures are designated by the same numbers. Rotating shaft 1 is sleeve 2
It is rotatably fitted to the other end, and a herringbone-shaped shallow groove 10 (groove depth of about 2 to 20 um) is cut therein. In addition, the sleeve 2 is provided with a resin material (
(e.g. polyacetal, polycarbonate, PPS, etc.)
The thrust plate 3 formed by molding is fixed. The thrust plate 3 has a shallow groove 11 (groove depth of about 2 to 20 um) carved therein to support the rotating shaft in the thrust direction, and a hole 7 is provided in the center. On the opposite surface (bottom side in the figure) where the shallow groove 11 is carved, there is a step such that the wall thickness of the inner circumference is thinner than that of the outer circumference, and there is also a part where the wall thickness of the outer circumference is thicker. A plurality of grooves 9 are cut into the lower surface of the . On the other hand, a convex portion 2c for attaching the thrust plate 3 is provided on the flat surface plate 2b. This convex portion 2C is provided with a groove 9a so that the hole 7, groove 9, and groove 9a are connected to each other after assembly.

Next, the operation of the hydrodynamic bearing having the above configuration will be explained. When the rotating shaft 1 starts rotating, the space 1a between the sleeve 2 and the slab I/plate 3
The fluid interposed in 20 is forced into the center by the shallow groove 11,
The pressure increases, causing the rotating shaft 1 to float. The pumped fluid passes through the central hole 7, groove 9a, and groove 9 that communicate with each other, returns to the gap 20, and circulates.

Here, the thrust plate 3 and the fixed plate 2b are the thrust plate 3 and the fixed plate 2b.
A stepped portion such that the thickness of the inner circumferential portion is thinner than that of the outer circumferential portion and the outer circumferential surface of the convex portion 2c of the fixed plate 2b are joined by press fitting or the like, and the inner circumferential portion of the thrust plate 3 and the fixed plate The structure is such that the convex portions ±C of 2b abut against each other. This results in
The convex portion 2C of the fixed plate 2b is fitted into the recess on the lower surface of the thrust plate 3, and the two are combined.

Next, regarding the shape accuracy of the thrust plate 3 in the present invention,
This will be explained using FIG. FIG. 2(a) is a diagram showing a thrust plate 3 molded from a resin material according to the present invention.
A step is provided on the surface opposite to the surface (top surface) in which the shallow groove 11 for the thrust bearing is carved so that the thickness of the inner circumference is thinner than the thickness of the outer circumference. This creates a recess on the bottom surface,
A protrusion 2C for mounting and holding the thrust plate is press-fitted here.

Shrinkage of the resin material due to molding generally occurs during the cooling process after molding, and the amount of shrinkage is determined in proportion to the wall thickness, and it can be considered that the shrinkage occurs in the direction where the cooling process is slowest.

Therefore, in the shape of the present invention, cooling of the part marked x in the figure is slow, so shrinkage occurs toward the x mark, and due to the difference in wall thickness between the outer and inner circumferences, the shape after shrinkage is as shown by the dotted line. It becomes a shape. Incidentally, when the conventional shape is not molded using a resin material, the shape becomes as shown in FIG. 2(b).

Here, if we focus on the shape accuracy of the bearing surface, the shape after molding will be stable in a convex shape, and the flatness of the shape will also be less than a few μm (excluding the component of Shallow Pickling 10), and when it is stationary, Since the rotating shaft 1 and the thrust plate 3 are in contact with each other near the hole in the center, the friction torque at the time of starting is reduced and wear and the like are less likely to occur.

On the other hand, since the thickness of the inner circumferential portion is thinner than that of the outer circumferential portion, the amount of deformation of the inner circumferential portion is small, so that it is suitable as a reference during installation. Therefore, the outer peripheral surface of the convex portion 2c of the fixed plate 2b and the step such that the thickness of the inner peripheral part of the thrust plate 3 is thinner than that of the outer peripheral part are joined by press fitting or the like, and the inner peripheral part of the thrust plate 3 and By configuring the fixing plate 2b so that the protrusions 2c collide with each other, the accuracy of the thrust bearing surface of the thrust plate 3 after assembly (for example, the perpendicularity with the radial bearing surface) can be easily achieved.

FIG. 3 is a diagram showing another embodiment of the hydrodynamic bearing according to the present invention. In the portion where the thickness of the outer circumference of the thrust plate 3 is thicker than the thickness of the inner circumference, the outer circumference is further thickened in a tapered shape. With such a configuration, during assembly such as press-fitting, the inner circumference is located at the convex portion 2c of the fixing plate 2b.
Since the outer circumferential portion is hard to come into contact with the fixing plate 2b when abutting against the bearing surface, it is easy to insert the bearing surface, and it is possible to improve the shape accuracy of the bearing surface without deteriorating the accuracy after assembly.

FIG. 4 is a diagram showing still another embodiment according to the present invention. The rotary shaft 1 is provided with a hole 21 at the center of the shaft end and a plurality of holes 22 communicating with the hole 21, so that fluid circulates therethrough. The thrust plate 3 has a flat plate shape, but is provided with a step such that its wall thickness is thinner at the inner circumference than at the outer circumference. The structure is such that the inner circumference of the thrust plate 3 and the protrusion 2c of the fixed plate 2b abut against each other.

In this case, the shape of the thrust plate 3 after shrinkage when molded from the resin material is as shown by the dotted line in FIG. Deformation of the inner surface is also reduced. Therefore, it is possible to obtain the same effects as in the above-mentioned embodiments. In the case of the conventional shape, the shape is as shown in FIG. 5(a).

Note that other shapes such as a tapered shape may be used as the shape of the step that makes the inner circumferential portion thinner than the outer circumferential portion.

[Effects of the Invention] As explained above, the shape of the thrust plate 3 is formed by molding using a resin material, and the thickness of the inner circumference is thinner than the thickness of the outer circumference on the surface opposite to the thrust bearing surface. By providing a step such that the thin inner circumferential portion and the convex portion 2C of the fixed plate 2b butt against each other, it becomes easier to achieve the shape accuracy of the bearing surface of the thrust plate 3, and the accuracy during assembly is improved. This has the effect of making it easier to produce, as well as lowering the cost.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of main parts of a hydrodynamic bearing device according to the present invention, Fig. 2
Figure (a) is an explanatory diagram of the modification of the thrust plate according to the present invention, the second
FIG. 3 is a side view of another example of the thrust plate according to the present invention, and FIG. 4 is a diagram illustrating another example of the thrust plate according to the present invention. Main part configuration diagram, 5th
Figure (a) is an explanatory diagram of the modification of the thrust plate in Figure 4, 'js5
FIG. 6B is a diagram illustrating a modification of a conventional thrust plate, and FIG. 6 is a diagram illustrating a main part configuration of a conventional hydrodynamic bearing device. 1st: rotating shaft 2 sleeve 2b: fixed plate 2C: convex portion 3 nislast plate. No.

Claims (5)

[Claims] (1) a shaft, a sleeve that rotatably supports the shaft in the radial direction, and a fixed plate fixed to the end of the sleeve;
a thrust plate attached to the fixed plate for supporting the shaft in the thrust direction; the thrust plate has a thick outer portion in the thrust direction; A dynamic pressure bearing device characterized in that the solid parts are joined by press-fitting, and the upper surface of the fixed plate is brought into contact with the thin inner surface of the thrust plate. (2) A hydrodynamic bearing device according to claim 1, characterized in that a shallow groove is formed in at least one of the thrust surface of the thrust plate or the shaft and at least one of the radial surface of the sleeve or the shaft. . (3) The thrust plate has a hole for fluid circulation passing through the center of the thin inner surface, and a gap is provided between the outer periphery of the thrust plate and the sleeve, and the gap and the hole in the thrust plate are formed. The dynamic pressure bearing device according to claim 1, characterized in that the dynamic pressure bearing device is configured such that the two are in communication with each other. (4) The dynamic pressure bearing device according to claim 1, wherein the thrust plate is made of a resin material. (5) The dynamic pressure bearing device according to claim 1, wherein the outer thick portion of the thrust plate is formed so as to become thicker toward the outside.