JPH09105409A - Bearing device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide an excellent durability, easy processing, and low cost manufacturing. SOLUTION: A bearing member 10 is made of plastic, and a cylindrical bearing hole 10A having an axial center oriented in the up-down direction is formed in this. The upper end of the bearing hole 10A is open and communicates with the outside, and the lower end is closed to form a bottom surface. A radial bearing surface 12 constituting a radial bearing is provided on the inner peripheral surface of the bearing hole 10A so as to face the outer peripheral surface of a shaft inserted into the bearing hole 10A, and a dynamic pressure generating groove 11 is provided on the radial bearing surface 12. . Both ends in the axial direction of the radial bearing surface 12 are oil sumps 14A, 14B for replenishing the radial bearing surface 12 with oil as a lubricating fluid.
Connect to The oil sump 14A on the opening side has a diameter larger than that of the radial bearing surface 12, and the oil sump 14B on the bottom side is a circumferential groove. The oil sump 14A on the opening side is the dynamic pressure generating groove 11
And the bottom side oil reservoir 14B communicates with the lower end side of the dynamic pressure generating groove 11. The depths of the oil sumps 14A and 14B are made substantially equal to the depth of the dynamic pressure generating groove 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device suitable for use in a laser printer, a magnetic disk device, etc., and particularly to a bearing device which is excellent in durability, easy to process and can be manufactured at low cost. It is a thing.

[0002]

2. Description of the Related Art A conventional bearing device has a structure as shown in FIG. That is, the sleeve 1 which is a cylindrical member
A shaft 2 having a dynamic pressure generating groove 3 formed on the outer peripheral surface thereof is inserted into the sleeve 1 and the sleeve 1 is utilized by utilizing the air pressure generated by the dynamic pressure generating groove 3 when the sleeve 1 and the shaft 2 rotate relative to each other.
A radial dynamic pressure air bearing that supports the shaft 2 in the radial direction is configured. Further, in the example of FIG. 4, the end portion of the sleeve 1 on the side opposite to the shaft 2 insertion side is closed by the thrust plate 4, and the end surface of the shaft 2 and the inner surface of the thrust plate 4 facing the end surface are A pair of permanent magnets 5 and 6 are fixed so as to generate repulsive force with each other, and the repulsive force of the permanent magnets 5 and 6 constitutes a thrust magnetic bearing that axially supports the sleeve 1 with respect to the shaft 2. doing.

Here, the sleeve 1, the thrust plate 4, and the shaft 2 which constitute the bearing member are usually manufactured from a structural steel material such as carbon steel.

[0004]

However, in the radial dynamic pressure air bearing as shown in FIG. 4, since air having a low viscosity and no lubricity is used as the lubricating fluid, the inside of the sleeve 1 is It is necessary to finish the bearing surface such as the peripheral surface and the outer peripheral surface of the shaft 2 with extremely high precision, and the bearing surface is required to have good slidability. Therefore, generally, after grinding or honing the inner peripheral surface of the structural steel sleeve 1, in order to improve the corrosion resistance and ensure the slidability, nickel is added to the inner peripheral surface of polyfluoroethylene. A composite plating impregnated with a system resin was applied, and grinding or honing was performed again to secure dimensional accuracy. As described above, since the sleeve 1 needs to be plated and grinding or honing is required before and after the plating, there is a problem that the processing cost increases.

Further, it is necessary to form a dynamic pressure generating groove 3 on the outer peripheral surface of the shaft 2, but since the shaft 2 is usually made of stainless steel, the dynamic pressure generating groove 3 must be processed by etching. However, there is a problem that the process is complicated and takes time, and the cost is high. Moreover, in the example of FIG. 4, the thrust magnetic bearing is configured by utilizing the repulsive force of the permanent magnets 5 and 6, so that the structure is complicated and the number of parts is large, which also contributes to the high cost. . Further, as a result of the repulsive force of the permanent magnets 5 and 6, particularly, the sleeve 1 is likely to fall off the shaft 2 as it is, and therefore a presser is required to prevent the fall off during transportation,
It took time to assemble it. Furthermore, if the permanent magnets 5 and 6 are slightly eccentric from the center of the rotation shaft due to mounting errors or the like, an eccentric load is applied to the radial bearing surface during rotation,
This caused deterioration of durability of the radial bearing surface.

The present invention has been made by paying attention to various problems that such a conventional bearing device has, and is a bearing device which has excellent durability, is easy to process, and can be manufactured at low cost. Is intended to provide.

[0007]

In order to achieve the above object, a bearing device according to a first aspect of the present invention has a cylindrical bearing hole formed in a plastic bearing member, and the bearing hole The inner peripheral surface is provided with a radial bearing surface that constitutes a radial bearing so as to face the outer peripheral surface of the shaft inserted into the bearing hole, and a thrust slide bearing is formed between the bottom surface of the bearing hole and the end surface of the shaft. Then, a groove for dynamic pressure generation is formed on the radial bearing surface, both axial ends of the radial bearing surface are respectively connected to oil sumps, and an oil sump on the bottom side is substantially equal to the groove for dynamic pressure generation. A circumferential groove that is continuous in the circumferential direction at a depth and communicates with the dynamic pressure generating groove, and the oil reservoir on the opening side has a larger diameter than the radial bearing surface and is continuous in the circumferential direction and communicates with the dynamic pressure generating groove. It is characterized by that.

In the bearing device of the present invention, the bearing member having the groove for dynamic pressure generation and having both the radial bearing surface and the thrust slide bearing surface can be molded by injection molding or the like using a plastic material. As a result, the processing of the bearing member is facilitated and the number of parts of the bearing device is reduced. Further, by this, it is not necessary to provide the dynamic pressure generating groove on the shaft member.

Next, the invention described in claim 2 is different from the structure described in claim 1, in that the bearing member is formed of a plastic in which carbon fiber (CF) is filled in polyphenylene sulfide resin (PPS) as a molding material. It is characterized by being a member. By configuring the bearing member with the plastic made of the resin as described above, the bearing member has excellent wear resistance, durability, and strength, and can be easily molded.

The filler to be filled in the polyphenylene sulfide resin (PPS) may be the carbon fiber alone or polytetrafluoroethylene (PTF).
Other fillers such as E) may be mixed. At this time,
When the polyphenylene sulfide resin (PPS) is filled with another filler in addition to the carbon fiber, it is preferable to limit the total amount of the fillers to the range of 20 to 50% by weight. If the amount is less than 20% by weight, the molding shrinkage at the time of molding may be large and the predetermined molding accuracy may not be ensured. If the amount is more than 50% by weight, the fluidity of the resin may be deteriorated and the accuracy may not be secured. This is because.

When polytetrafluoroethylene (PTFE) is filled as the other filling material, it is 5 to 2
It is recommended to fill only 0% by weight. By filling with this polytetrafluoroethylene, the slidability of the bearing surface of the bearing member is improved. Here, if the amount is less than 5% by weight, the slidability is deteriorated, and if the amount is more than 20% by weight, PTFE has a large linear expansion coefficient and tends to segregate during injection molding, so that the molding accuracy may not be secured. .

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views showing an embodiment of the present invention, and FIG. 1 is a longitudinal sectional view of a bearing member 10 of a bearing device according to the present invention. First, the structure will be described.
The bearing member 10 in the present embodiment is made of plastic, and has a cylindrical bearing hole 10A with a center line directed in the up-down direction, and the upper end side of the bearing hole 10A is open to the outside. The lower end side of the bearing hole 10A is closed to form a bottom surface. The bearing member 10
A flange 10B is integrally formed on the outer peripheral surface of the lower end portion of the bearing 10 with bolt through holes 10a and the like used when fixing the stator and the like to the bearing member 10.

Further, the bearing hole 1 is formed on the inner peripheral surface of the bearing hole 10A.
A radial bearing surface 12 constituting a radial bearing is provided so as to face the outer peripheral surface 15b of the shaft 15 inserted into the shaft 0A, and a dynamic pressure generating groove 11 is formed in the radial bearing surface 12. Then, both ends of the radial bearing surface 12 in the axial direction (vertical direction in FIG. 1) are filled with oil as a lubricating fluid.
2 is connected to the oil sumps 14A and 14B used to replenish the oil and improve its durability. These oil sumps 14A and 14B are continuous in the circumferential direction, the oil sump 14A on the opening side has a cylindrical shape with a diameter larger than that of the radial bearing surface 12, and the oil sump 14B on the bottom side is a circumferential groove. The oil sump 14A on the opening side communicates with the upper end of the dynamic pressure generating groove 11, and the oil sump 14B on the bottom side communicates with the lower end of the dynamic pressure generating groove 11.

Here, the depth H of the oil sumps 14A, 14B
Is approximately equal to the depth h _{0 of} the dynamic pressure generating groove 11 which is enlarged in the axial direction in FIG. The reason is that the oil sump 14A, 1
4B is preferable as the volume is larger or deeper, while the molded bearing member 10 is used for injection molding of plastic.
Since it is necessary to forcibly remove the core pin of the mold from the above, if the depth H of the oil sump 14B on the bottom surface side is made deeper than the depth h _{0 of the} groove 11 for dynamic pressure generation, the radial bearing surface 1 is removed when the mold is removed.
2 is likely to be damaged. However, since the oil sump 14A on the opening side is on the side where the mold is pulled out, it can be deeper than h _{0 if} necessary. In addition, the oil sump 14 on the opening side
A may be a conical surface having a large diameter on the opening side. Further, the oil sump 14A on the opening side may be a circumferential groove having a depth of h ₀ .

The oil sumps 14A and 14B are formed at both ends of the radial bearing surface 12 when the bearing member 10 is molded by plastic injection. The inner surface near the both ends of the bearing hole 10A is oriented or solidified. This is because it is easily affected by the speed and is affected by the difference in the heat shrinkage speed depending on the position when shrinking due to the temperature decrease of the plastic, and therefore it is difficult to secure the molding accuracy. That is, at a position where molding accuracy is difficult, the oil sump 14 where molding accuracy is not so important
By forming A and 14B, it is possible to secure a replenishing path of the lubricating fluid while solving the problem of processing accuracy.

In this embodiment, as shown in FIG. 1, two herringbone grooves are connected in the axial direction to form a dynamic pressure generating groove 11, and the bending points of each herringbone groove are also formed. The widths A and B of the end portion in the axial direction at the boundary are defined as so-called asymmetric grooves wider than the widths a and b of the inner portion in the axial direction. This is because even if the dimensional accuracy and shape of the radial bearing surface 12 are slightly poor, the flow of the lubricating fluid due to the pump action, which works to push it toward the central portion in the axial direction, is more than the flow toward the outer side in the axial direction. It also becomes stronger and it is possible to prevent the lubricating fluid from leaking from the radial bearing surface 12 to the outside.

On the other hand, the bottom surface of the bearing hole 10A is raised in the shape of a convex spherical surface at the center thereof, and the bottom surface of the bearing hole 10A serves as a thrust bearing surface 13. Specifically, FIG.
As shown in FIG. 7, the lower end surface 15a of the shaft 15 inserted into the bearing hole 10A is in point contact with the convex spherical surface of the thrust bearing surface 13, thereby forming a thrust slide bearing capable of suppressing friction torque during rotation. . Also, the bearing hole 10A
A through hole 10b penetrating the bearing member 10 from the bottom surface of the bearing hole 10A is formed on the bottom surface at a position radially outward from the convex spherical surface, that is, at the bottom surface of the bearing hole 10A that does not contact the lower end surface 15a of the shaft 15. ing. This through hole 10b
Is used as an air vent hole when the shaft 15 is inserted into the bearing hole 10A, thereby facilitating the assembling work.

The through hole 10b is not limited to the above position and may be provided at another place as long as it is the bottom surface of the bearing hole 10A. The point is that it is sufficient that the air in the bearing hole 10A can be pushed to the outside when the shaft 15 is inserted. After the assembly, the through hole 10b may be sealed with a tape or the like. When the viscosity of the lubricating fluid is low or the gap between the shaft 15 and the bearing member 10 is large and the air in the bearing hole 10A is pushed out when the shaft 15 is inserted into the bearing hole 10A, the through hole 10b is formed. You don't have to.

Here, the plastic material forming the bearing member 10 has strength, is easy to mold, and in order to ensure good lubricity, for example, polyphenylene sulfide resin (PPS resin) is used as a filler with carbon. The fiber and polytetrafluoroethylene (PTFE) are filled in an amount of 5 to 20% by weight, and the optimum filling amount is 20 to 50% by weight in total. If the filling amount of the filler is too large, it becomes difficult to mold. On the contrary, if the filling amount is too small, the strength cannot be ensured. Therefore, in order to satisfy both requirements, the filling amount of the filler is within the above range. Was preferred. Further, if the filling amount of polytetrafluoroethylene is more than 20% by weight, it tends to segregate during molding, while conversely if it is less than 5% by weight, the slidability deteriorates. In order to satisfy the above condition, the filling amount of polytetrafluoroethylene is preferably set in the above range.

The carbon fiber content is preferably 5 to 40% by weight. This is because if it is less than 5% by weight, the strength required for the bearing member may not be secured, and 40% by weight
This is because if the amount is larger, molding may be difficult. Here, in addition to the filler as described above, a filler such as glass fiber or molybdenum disulfide may be separately filled in order to improve strength, dimensional stability, slidability and the like.

The total amount of the above fillers is 20.
It is preferably in the range of ˜50% by weight. If the total amount of the fillers is less than 20% by weight, the molding shrinkage during injection molding becomes large, and the desired molding accuracy cannot be ensured, and if it exceeds 50% by weight, the fluidity of the resin during injection molding becomes large. There is a possibility that the quality will deteriorate and desired molding accuracy cannot be secured.

As the plastic material forming the bearing member 10, in addition to the above, glass fiber or carbon fiber for improving strength and dimensional stability, and polytetrafluorocarbon for improving slidability. It may be a polyacetal resin or a nylon resin to which a solid lubricant such as fluoroethylene or molybdenum disulfide is added. Further, in order to prevent the bearing member 10 from being deformed with time, it is preferable to perform a so-called annealing treatment in which a heat treatment is performed at a high temperature, if necessary.

As this annealing treatment method, for example, there is a method of heating and holding it free, or a forced annealing in which a rod is inserted into the bearing hole 10A to heat it in order to suppress a change in inner diameter and a change in shape. Next, the function and effect of this embodiment will be described. That is, the shaft 15 is inserted into the bearing hole 10A of the bearing member 10 having the above-described structure, and the oil serving as the lubricating fluid is interposed in the gap between the bearing member 10 and the shaft 15. If relative rotation occurs between the shaft 15 and the shaft 15, high pressure is generated in the gap between the radial bearing surface 12 and the shaft 15 by the dynamic pressure generating groove 11, so that the shaft 15 is supported in the radial direction and the bearing hole is formed. Since the bottom surface of 10A and the lower end surface 15a of the shaft are in point contact, the friction torque between them is sufficiently small.
Smooth relative rotation between the bearing member 10 and the shaft 15 is ensured.

Further, since oil is used as the lubricating fluid, it has high viscosity and lubricity, which also eliminates the need to finish the surface of the bearing hole 10A with extremely high precision,
The cost is reduced, and both axial ends of the radial bearing surface 12 are connected to the oil sumps 14A and 14B so that the lubricating fluid can be replenished, so that the durability of the radial bearing surface 12 is particularly improved.

With the above structure, the bearing member 10 in which the dynamic pressure generating groove 11 is formed can be molded by injection molding of plastic, so that the manufacturing cost can be kept low. it can. Further, since it is not necessary to form a dynamic pressure generating groove on the outer peripheral surface of the shaft 15, the manufacturing cost of the shaft can be reduced, and the thrust bearing is the sliding bearing as described above. Since the structure is simplified and the number of parts is reduced, the cost can be reduced.

FIG. 3 is a diagram showing an example of application of the bearing member 10 to an actual device, which is a vertical sectional view of a spindle motor for a polygon scanner. That is, the bearing member 10
Is a state in which its axis is oriented vertically, and a ferromagnetic back yoke 21 is fixed to the upper surface of the flange 10B of the bearing member 10. A ring-shaped substrate 20 is coaxially disposed on the outer periphery of the bearing member 10 with a predetermined distance from the back yoke 21, and a coil 22 is disposed between the substrate 20 and the back yoke 21. The back yoke 21 and the coil 22 constitute a stator of a plane facing motor.

A shaft 15 is inserted into the bearing hole 10A of the bearing member 10. A ferromagnetic yoke 23 is fixed to the shaft 15, and a permanent magnet rotor magnet is attached to the lower surface of the yoke 23. 24 is fixed. On the upper side of the yoke 23, a polygon mirror 26 is coaxially fixed to the shaft 15 via a mounting flange 25, and the yoke 23 and the rotor magnet 24 constitute a rotor of a plane-opposed motor that axially faces the stator. There is.

With the spindle motor having such a structure, while the above-described effect of the bearing device can be obtained, the magnetic force of the rotor magnet 24 is the stator even when the motor is not driven. Is sucked in the axial direction, and it is difficult for the shaft 15 to come out of the bearing member 10 during transportation,
There is no need to separately provide a press or the like in order to prevent the dropout as in the related art, and there is an advantage that the labor and the like during assembly are simplified. When the attractive force is insufficient only by the magnetic force of the rotor magnet 24, the permanent magnets may be fixed to the yoke 23 and the substrate 20 so as to attract each other, or the yoke 23 may be attached to the substrate 20. The permanent magnets may be fixed so as to face each other, and the force of the permanent magnets to attract the ferromagnetic yoke 23 may be used to prevent the shaft 15 from coming off.

Although the dynamic pressure generating grooves 11 are two herringbone grooves in the above embodiment, the present invention is not limited to this, and one herringbone groove may be used, or other herringbone grooves may be used. It may be in the form. Further, in the above-described embodiment, the thrust spherical bearing is formed by forming the convex spherical surface at the center of the bottom surface of the bearing hole 10A, but when the axial load is large, the thrust slide bearing is opposed to the bottom surface of the bearing hole 10A or this. A groove for dynamic pressure generation may be formed in the end surface 15a of the shaft 15, and buoyancy may be generated by the dynamic pressure effect associated with the rotation of the shaft 15 with respect to the bearing member 10 to reduce wear of the thrust slide bearing portion. Further, instead of the convex spherical surface shown in FIG. 1, a cylindrical convex portion may be provided coaxially on the bottom surface of the bearing hole 10A, and in some cases, a convex spherical surface or a cylindrical convex portion is provided on the end surface 15a of the shaft 15. You may do it. Bearing hole 10
It is preferable to make the contact between the bottom surface of A and the end surface 15a of the shaft 15 at the central portion of the bottom surface of the bearing hole 10A in order to reduce friction during rotation.

In the above embodiment, the radial bearing surface 12 and the thrust bearing surface 13 are integrally formed.
A sleeve having a radial bearing surface 12 in the through hole and a disc having a thrust bearing surface 13 at the end face are formed as separate members, and the outer peripheral surface of the lower end portion of the sleeve is provided as a disc. The bearing member 10 may be formed by press-fitting into the portion.

Further, in the above embodiment, the case where the bearing device according to the present invention is applied to the polygon scanner motor has been described, but the application target of the present invention is not limited to this, and a magnetic disk device. Of course, it can also be applied as a spindle motor for an optical disk device or the like. Although the plane-opposed motor has been described, it may be a circumferentially-opposed motor in which the rotor magnet is axially displaced with respect to the stator so that the shaft 15 does not come off from the bearing member 10.

[0032]

EXAMPLES The bearing member 10 of the bearing device as described above was manufactured under the following conditions. The bearing member 10 was produced by injection molding using a plastic in which PPS was filled with 30% by weight of carbon fiber, 15% by weight of PTFE, and several% of other filler such as graphite as a molding material. The total amount of the above fillers was 50% by weight or less.

The manufactured bearing member 10 has an inner diameter of 4 mm.
φ, the outer diameter was 7 mm, the wall thickness was 1.5 mm, and the length in the axial direction was 12 mm. However, in order to confirm with a predetermined molding accuracy, the dynamic pressure generating groove 11 and the oil sump 1
4A and 14B are not formed. FIG. 5A is a diagram in which the circularity of the inner peripheral surface of the bearing hole 10A of the bearing member manufactured under the above conditions is measured, and from this figure, the inner peripheral surface of the bearing hole 10A according to the present invention has an inner peripheral surface of 2 μm or less. It can be seen that the roundness becomes.

Further, FIG. 5 (b) is a view of measuring the cylindricity, and from this figure, the vicinity of the open end of the inner peripheral surface of the bearing hole 10A is tilted inward by 3 to 4 μm. It can be seen that, except for the vicinity, the inner peripheral surface of the bearing hole 10A of the bearing member 10 according to the present invention has a cylindricity of 2 μm or less. next,
When the dynamic pressure generating groove 11 and the oil sumps 14A and 14B were provided and the bearing member 10 was injection molded under the above conditions, FIG. 6 was obtained. However, the depth of each of the oil reservoirs 14A and 14B and the dynamic pressure generating groove 11 provided on both axial ends of the bearing hole 10A was set to about 8 μm.

Even in this case, as can be seen from FIG. 6A, the circularity of the inner peripheral surface of the bearing hole 10A is 2 μm or less. Further, as can be seen from FIG. 6 (b), the shape accuracy of the inner peripheral surface of the bearing hole 10A provided with the dynamic pressure generating groove 11 is 2
It can be seen that it is less than μm. As described above, the bearing hole 10A of the bearing member 10 according to the present invention sufficiently satisfies the molding precision required for the dynamic pressure bearing, such that the dynamic pressure generating groove 11 is also accurately molded.

Further, it is confirmed that the sliding property and the wear resistance are excellent, and it is possible to suppress the impact and damage when the bearing device comes into contact with the shaft at the time of starting and stopping. In particular, although the thrust bearing surface is easily worn, the bearing hole 10A of the bearing member 10 according to the present invention has the wear resistance required for the thrust slide bearing surface.

[0037]

As described above, in the bearing device according to the present invention, the dynamic pressure generating groove is formed in the inner peripheral surface of the bearing hole formed in the plastic bearing member to form the bearing hole. A thrust slide bearing was constructed between the bottom surface and the end surface of the shaft inserted in this bearing hole, and both axial end portions of the radial bearing surface were connected to an oil sump, resulting in excellent durability and easy machining. The effect that it can manufacture at low cost is acquired.

At this time, if the invention described in claim 2 is adopted, it is possible to obtain an effect that a bearing member having excellent wear resistance, durability, strength and the like can be easily processed, and the bearing can be easily processed. It is possible to reduce the impact and damage when the bearing member comes into contact with the shaft at the time of starting and stopping the device.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a bearing member according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a dynamic pressure generating groove.

FIG. 3 is a vertical sectional view of a spindle motor showing an application example of the present invention.

FIG. 4 is a vertical sectional view showing an example of a conventional bearing device.

FIG. 5 is a view of a bearing member measured in an example,
(A) is a measurement of circularity, and (b) is a measurement of cylindricity.

FIG. 6 is a view of the bearing member measured in the example,
(A) is a measurement of circularity, and (b) is a measurement of cylindricity.

[Explanation of symbols] 10 bearing member 10A bearing hole 11 dynamic pressure generating groove 12 radial bearing surface 13 thrust bearing surface 14A, 14B oil sump 15 shaft 15a lower end surface (end surface of shaft) 15b outer peripheral surface of shaft

Claims (2)

[Claims] 1. A radial bearing in which a cylindrical bearing hole is formed in a plastic bearing member, and an inner peripheral surface of the bearing hole faces a peripheral surface of a shaft inserted into the bearing hole to form a radial bearing. A bearing surface is provided, a thrust slide bearing is formed between the bottom surface of the bearing hole and the end surface of the shaft, and dynamic pressure generating grooves are formed on the radial bearing surface, and both axial ends of the radial bearing surface are formed. The portions are respectively connected to the oil sumps, and the oil sumps on the bottom side are circumferential grooves that are continuous in the circumferential direction at a depth substantially equal to the dynamic pressure generating grooves and communicate with the dynamic pressure generating grooves. The bearing device is characterized in that the oil sump has a diameter larger than that of the radial bearing surface, is continuous in the circumferential direction, and communicates with the dynamic pressure generating groove. 2. The bearing device according to claim 1, wherein the bearing member is a member made of a plastic in which carbon fibers are filled in a polyphenylene sulfide resin as a molding material.