JPH09222118A - Bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing with high accuracy and excellent in its durability and whose machining is easy to be manufactured at a low cost. SOLUTION: In a bearing device, the inner peripheral surface of a cylindrical- shape bearing hole 10a in which a shaft 15 is inserted is considered a radial bearing surface 12 and also a dynamic pressure generating groove is provided on this radial bearing surface 12, and a radial dynamic pressure bearing member 10 in which the radial bearing surface 12 constitute a radial dynamic pressure bearing facing to the outer peripheral surface of a shaft 15, and a part facing to the bottom end surface 15a of the shaft 15 fittingly fixed to the bottom end part in the axial direction of the radial dynamic pressure bearing member 10 and inserted in a bearing hole 10A are considered a thrust bearing surface 13, and also is provided a thrust sliding bearing member 13a by which the thrust bearing surface 13 constitutes a thrust sliding bearing facing to the bottom end surface 15a of the shaft 15. And the radial dynamic pressure bearing member 10 and the thrust sliding bearing member 13a are formed by injection molding by using resins of mutually different substances.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laser printer,
The present invention relates to a bearing device used for an information device such as a magnetic disk device.

[0002]

2. Description of the Related Art Conventionally, a bearing device as shown in FIG. 5 has been used for a scanner motor for a polygon mirror of a laser printer which is an information device. In this bearing device, a shaft 2 having a groove 3 for generating a dynamic pressure formed on an outer peripheral surface thereof is inserted into a sleeve 1 which is a cylindrical member, and the dynamic pressure is generated when the sleeve 1 and the shaft 2 rotate relative to each other. The air pressure generated by the groove 3 is used to form a radial dynamic pressure air bearing that supports the sleeve 1 in the radial direction with respect to the shaft 2.
In the example of FIG. 5, the end of the sleeve 1 opposite to the shaft 2 insertion side is closed by the thrust plate 4, and the end face of the shaft 2 and the inner face of the thrust plate 4 facing the end face are closed. The pair of permanent magnets 5 and 6 are fixed so that repulsive force is generated between them, and the repulsive force of the permanent magnets 5 and 6 causes
A thrust magnetic bearing that axially supports the sleeve 1 with respect to the shaft 2 is configured.

[0003]

However, since the bearing device as shown in FIG. 5 has a structure in which air having low viscosity and no lubricity is used as the lubricating fluid,
The bearing surface such as the inner peripheral surface of the sleeve 1 and the outer peripheral surface of the shaft 2 needs to be finished with extremely high precision, and the bearing surface is also required to have good slidability. Therefore, generally, after grinding or honing the inner peripheral surface of the structural steel sleeve 1, nickel is polyfluorinated on the inner peripheral surface in order to improve corrosion resistance and ensure slidability. A composite plating impregnated with an ethylene resin was applied, and grinding or honing was performed again in order 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.

A groove 3 for generating dynamic pressure is formed on the outer peripheral surface of the shaft 2.
However, since the shaft 2 is usually made of stainless steel, the groove 3 for generating the dynamic pressure must be processed by etching, and the process is complicated and time-consuming, and the cost is high. There is a problem that Moreover, in the example of FIG. 5, since the thrust magnetic bearing is configured by utilizing the repulsive force of the permanent magnets 5 and 6, the structure is complicated and the number of parts is large, which is also a factor of the high cost. . Further, as a result of the repulsive force of the permanent magnets 5 and 6, the sleeve 1 is likely to fall off the shaft 2 as it is. Therefore, it is necessary to hold the sleeve 1 during transportation or the like to prevent it from falling off. It took time. Further, if the permanent magnets 5 and 6 are slightly eccentric from the center of the rotation shaft due to mounting error or the like, an eccentric load is applied to the radial bearing surface during rotation, which causes 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 to manufacture with high accuracy and excellent durability, easy processing, and low cost. An object of the present invention is to provide a bearing device capable of

[0006]

In order to achieve the above object, the bearing device according to the present invention is such that the inner peripheral surface of a cylindrical bearing hole into which a shaft is inserted is a radial bearing surface and the radial bearing is A radial dynamic pressure bearing member having a groove for generating a dynamic pressure on its surface, and the radial bearing surface facing the outer peripheral surface of the shaft to form a radial dynamic pressure bearing, and an axial direction of the radial dynamic pressure bearing member. A portion which is fixed to the end portion of the shaft and faces the tip end surface of the shaft inserted into the bearing hole is a thrust bearing surface, and the thrust bearing surface faces the tip end surface of the shaft to form a thrust slide bearing. And a thrust sliding bearing member, wherein the radial dynamic pressure bearing member and the thrust sliding bearing member are made of different resins.

In the bearing device of the present invention, the radial dynamic pressure bearing member having a groove for generating a dynamic pressure and having a radial bearing surface, and the thrust slide bearing portion having a thrust bearing surface are both injection-molded using a resin material. And the like. As a result, the processing of each bearing member is facilitated, and the number of parts of the bearing device is reduced, so that the cost can be reduced. Further, by forming the dynamic pressure generating groove on the radial bearing surface, it is not necessary to provide the dynamic pressure generating groove on the outer peripheral surface of the shaft as in the conventional case.

Further, since the radial dynamic pressure bearing member and the thrust slide bearing member are made of resins of different materials, the fluidity of the radial dynamic pressure bearing member is good because of the performance required for each bearing member. , It is possible to select a resin that has a small molding shrinkage and is strong and has excellent wear resistance, and a thrust sliding bearing member that has particularly excellent slidability and wear resistance. By forming each bearing member by injection molding or the like using the above resin as a material, it becomes possible to make the bearing highly accurate and excellent in durability.

In this case, it is preferable that oil reservoirs having a diameter larger than that of the radial bearing surface and continuous with the groove for dynamic pressure generation are formed along the circumferential direction at both axial end portions of the radial bearing surface. By doing so, the oil as the lubricating fluid can be replenished from the oil reservoir to the radial bearing surface,
It is possible to further improve the durability of the radial dynamic pressure bearing member.

As a resin material for the radial dynamic pressure bearing member, polyphenylene sulfide resin (PPS) is used.
It is preferable to use carbon fiber (CF) filled in. By forming a radial dynamic pressure bearing member by injection molding or the like using such a resin material, molding of the radial dynamic pressure bearing member can be facilitated, and wear resistance, durability and strength are improved. Can be achieved.

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. Here, when the polyphenylene sulfide resin (PPS) is filled with another filler in addition to the carbon fibers, it is preferable to limit the total amount of the fillers to the range of 20 to 50% by weight. If the total amount of the fillers is less than 20% by weight, the molding shrinkage at the time of molding may be large and the predetermined molding accuracy and strength may not be ensured. Molding accuracy may not be ensured.

When the above-mentioned filler is filled with polytetrafluoroethylene (PTFE), it is 5 to 20% by weight.
It is preferable to fill only. Filling with polytetrafluoroethylene makes it possible to improve the slidability of the radial bearing surface. Here, if the amount is less than 5% by weight, the slidability deteriorates. On the other hand, if the amount is more than 20% by weight, PTFE has a large linear expansion coefficient and segregates easily during injection molding, so that molding accuracy may not be ensured. is there.

Further, as the resin material of the thrust slide bearing member, it is preferable to use a resin composition containing polyamide 6 resin (PA6) and polyethylene resin (PE). By molding a thrust sliding bearing member using such a resin composition, the sliding property is excellent and
In particular, it becomes possible to make it excellent in abrasion resistance under high surface pressure.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an explanatory sectional view for explaining a bearing device as an example of an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a groove for generating a dynamic pressure, and FIG. 3 shows a bearing device of the present embodiment. It is a longitudinal cross-sectional view showing a state of being incorporated in a spindle motor for a polygon scanner.

First, the structure will be described. The bearing device according to the present embodiment includes a radial dynamic pressure bearing member 10 and a thrust slide bearing member 13a, and each of the bearing members 10 and 13a is formed by injection molding. It is made of molded plastic. A cylindrical bearing hole 10A is formed inside the radial dynamic pressure bearing member 10 with its axis extending vertically. The upper end side of the bearing hole 10A is open, and the lower end side is closed by a thrust slide bearing member 13a fitted and fixed by press fitting or the like. A flange 10B is formed on the outer peripheral surface of the lower end portion of the radial dynamic pressure bearing member 10 with bolt insertion holes 10a and the like used when fixing the stator and the like to the radial dynamic pressure bearing member 10.
Are integrally formed.

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 dynamic pressure bearing is provided so as to face the outer peripheral surface 15b of the shaft 15 inserted into the shaft 0A, and the radial bearing surface 12 has a groove 1 for generating dynamic pressure.
1 is formed. In this embodiment, the dynamic pressure generating grooves 11 are two herringbone grooves. However, the present invention is not limited to this, and one herringbone groove may be used, or another type. It may be.

The upper and lower ends of the radial bearing surface 12 in the axial direction are used as an oil sump 14 for replenishing the radial bearing surface 12 with oil as a lubricating fluid to improve its durability.
It is connected to A and 14B. These oil sumps 14A,
14B is continuous in the circumferential direction, and the oil sump 1 on the upper end side
4A has a cylindrical shape with a diameter larger than that of the radial bearing surface 12, and the oil sump 14B on the lower end side is a circumferential groove. The oil sump 14A on the upper end side communicates with the upper end of the groove 11 for dynamic pressure generation, and the oil sump 14B on the lower end side thrust thrust bearing member 13a.
Is located above and communicates with the lower end of the groove 11 for generating dynamic pressure.

The depth H of the oil sumps 14A and 14B is shown in FIG.
Further, the depth is made substantially equal to the depth h ₀ of the groove 11 for dynamic pressure generation, which is enlarged and shown with the axis thereof in the left-right direction. The reason is that the oil reservoirs 14A and 14B preferably have a large capacity, that is, a deeper depth, from the viewpoint of replenishing the lubricating fluid, while the molded radial dynamic bearing member 1 is used in plastic injection molding.
Since it is necessary to forcibly remove the core pin of the mold from 0, if the depth H of the oil sump 14B on the lower end side is made deeper than the depth h ₀ of the groove 11 for dynamic pressure generation, the radial bearing is used when the mold is removed. This is because the surface 12 may be damaged. However, since the oil sump 14A on the upper end side is on the side where the mold is removed, it can be deeper than h _{0 if} necessary. Further, the oil sump 14A on the upper end side may be a large-diameter conical surface whose diameter increases upward.
Further, the oil sump 14A on the upper end side may be a circumferential groove having a depth of h ₀ .

If the direction of removing the mold is reversed from that described above, the oil sump 14B on the lower end side is on the side of the direction of removing the mold, so that it can be made deeper than the depth h ₀ of the groove for dynamic pressure generation, if necessary. . Further, the mounting hole 13b for mounting the thrust slide bearing member 13a can be formed at the time of injection molding. 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 upper end opening of the bearing hole 10A that is easily affected by orientation and solidification speed. Since the vicinity and the inner peripheral surface of the lower end of the bearing hole 10A, which is easily affected by the flange 10B, is affected by the difference in the heat shrinkage speed depending on the position when shrinking due to the temperature decrease of the resin, it is difficult to secure the molding accuracy. Is. That is, by forming the oil reservoirs 14A and 14B in which the molding accuracy is not so important at a position where it is difficult to ensure the molding accuracy, it is possible to secure the lubricating fluid replenishment route while solving the problem in the processing accuracy. You can do it.

In this embodiment, as shown in FIG. 1, two herringbone grooves are axially connected to each other to form a groove 11 for generating a dynamic pressure, and each herringbone groove is bent. Widths A and B of the end portion in the axial direction with respect to the point,
It is a so-called asymmetric groove wider than the widths a and b of the axially inner portion. 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. This is because it becomes stronger, and the lubricating fluid can be prevented from leaking from the radial bearing surface 12 to the outside, which is preferable for ensuring durability.

The thrust slide bearing member 13a is made of a disk-shaped member having a diameter larger than that of the bearing hole 10A, and is fitted and fixed by press fitting into a mounting hole 13b formed continuously at the lower end of the bearing hole 10A. The lower end of the hole 10A is closed. In addition, in this embodiment, the thrust slide bearing member 13a is press-fitted, but it is not necessarily limited to this. For example, instead of press-fitting, it may be bonded or screwed. It just needs to be fixed.

The central portion of the upper surface of the thrust slide bearing member 13a is raised in a convex spherical shape, and the upper surface of the thrust slide bearing member 13a is the thrust bearing surface 13. Specifically, as shown in FIG. 3, the flat lower end surface (tip surface) 15a of the shaft 15 inserted into the bearing hole 10A and facing the thrust bearing surface 13 is in point contact with the convex spherical surface of the thrust bearing surface 13. By doing so, a thrust slide bearing that can suppress the friction torque during rotation is configured.
When the axial load is large, a groove (not shown) for generating dynamic pressure is provided on the thrust bearing surface 13 or the lower end surface 15a of the shaft 15 facing the thrust bearing surface 13, and the radial dynamic pressure bearing member 10 of the shaft 15 is provided. The wear of the thrust bearing surface 13 may be reduced by generating buoyancy due to the dynamic pressure effect that accompanies the rotation of the. In addition, the thrust bearing surface 13
In place of the convex spherical surface, a convex flat surface may be projected, or the upper surface of the thrust bearing surface 13 may be flat and the lower end surface 15a of the opposite shaft 15 may be a convex spherical surface or a convex flat surface. In short, any shape may be used as long as the friction during rotation can be reduced and partial contact with the shaft 15 can be prevented.

The thrust slide bearing member 13a has a through hole 10b at a position radially outward from the convex spherical surface, that is, at a position where it does not contact the lower end surface 15a of the shaft 15.
Are formed. The 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 position of the through hole 10b does not necessarily have to be formed in the thrust slide bearing member 13a.
It may be formed on the bottom of the radial dynamic pressure bearing member 10. The point is that when the mating shaft 15 is inserted, it may be at a position where the air in the bearing hole 10A can be pushed out. Also, after assembly,
The through hole 10b may be sealed with a tape or the like. In addition,
If the viscosity of the lubricating fluid is low, or the gap between the shaft 15 and the radial dynamic pressure bearing member 10 is large, the bearing hole 10A of the shaft 15
When the air in the bearing hole 10A is pushed out at the time of insertion into the hole, the through hole 10b may be omitted.

Here, in this embodiment, for example, polyphenylene sulfide resin is used as the resin material for forming the radial dynamic pressure bearing member 10 in order to ensure strength, easy molding, and good lubricity. (PPS
Resin) with carbon fiber and 5 to 20% by weight of polytetrafluoroethylene (PTFE) as a filler, and the total amount of the filler is 20 to 50% by weight.
As a resin material for forming the thrust slide bearing member 13a, a polyamide 6 resin (PA6) and a polyethylene resin (PE) are provided in order to sufficiently secure slidability and abrasion resistance particularly at high surface pressure. A resin composition is used.

With respect to the resin material forming the radial dynamic pressure bearing member 10, if the filling amount of the above-mentioned filling material is too large, molding becomes difficult, and conversely, if it is too small, the strength cannot be secured, so both requirements are satisfied. Therefore, the filling amount of the filler is preferably set in the above range. If the filling amount of polytetrafluoroethylene is more than 20% by weight, it tends to segregate during molding, and conversely 5% by weight.
If the amount is less than the above range, the slidability deteriorates. Therefore, in order to satisfy both requirements, the filling amount of polytetrafluoroethylene is preferably in the above range.

Here, in addition to the above-mentioned filler, a filler such as glass fiber or molybdenum disulfide may be separately filled in order to improve strength, dimensional stability, slidability and the like. . In addition, the filling amount of the filling material is 20 to 50 in total.
It is preferably in the range of% by weight. The total number of fillers is 2
If it is less than 0% by weight, the molding shrinkage at the time of injection molding becomes large and desired molding accuracy cannot be secured.
If the amount is larger than the above range, the fluidity of the resin during injection molding deteriorates, and the desired molding accuracy may not be ensured.

As the resin material forming the radial dynamic pressure bearing member 10, in addition to the above, glass fiber or carbon fiber for improving strength and dimensional stability, and for improving slidability. It may be a polyacetal resin or a nylon resin to which a solid lubricant such as polytetrafluoroethylene or molybdenum disulfide is added. Further, in order to prevent the radial dynamic pressure bearing member 10 from being deformed with time, it is preferable to perform a so-called annealing process 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 and heated 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 radial dynamic pressure bearing member 10 having the above-described configuration, and the radial dynamic pressure bearing member 10 and the shaft 15 are inserted.
If relative rotation occurs between the radial dynamic pressure bearing member 10 and the shaft 15 with oil as a lubricating fluid interposed in the gap between the radial dynamic pressure bearing groove 10 and the radial bearing surface 12 by the dynamic pressure generating groove 11.
High pressure is generated in the gap between the shaft 15 and the outer peripheral surface of the shaft 15,
Is supported in the radial direction, and the lower end surface 15a of the shaft 15 is
Since the convex spherical surface of the thrust bearing surface 13 and the lower end surface 15a of the shaft 15 are in point contact with each other, the friction torque between the two is sufficiently small. Therefore, the radial dynamic pressure bearing member 10
A smooth relative rotation between the shaft 15 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 for finishing the surface of the bearing hole 10A with extremely high precision.
The cost is reduced, and the axial upper and lower 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 radial dynamic pressure bearing member 10 having the groove 11 for generating dynamic pressure and having the radial bearing surface 12 and the thrust slide bearing member 13a having the thrust bearing surface 13 are provided. Since both can be formed by injection molding using resin as a material, the manufacturing cost thereof can be kept low. Further, since it is not necessary to form a groove for generating dynamic pressure on the outer peripheral surface of the shaft 15, the manufacturing cost of the shaft can be reduced, and
Since the thrust bearing is the slide bearing as described above, the structure is simplified and the number of parts is reduced, so that the cost can be reduced.

Further, since the radial dynamic pressure bearing member 10 and the thrust slide bearing member 13a are injection molded using resins made of different materials, each bearing member 10, 13 is formed.
Depending on the performance required for a, the radial dynamic pressure bearing member 10
Is a resin with good fluidity, small molding shrinkage, strength, and excellent wear resistance. For thrust slide bearing 13a, a resin with particularly good slidability and wear resistance is separately prepared. Each bearing member 10 can be selected.
It is possible to make a and 13a highly accurate and excellent in durability.

FIG. 3 is a view 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 radial dynamic pressure bearing member 10 is in a state in which its axis is oriented vertically, and the ferromagnetic back yoke 21 is fixed to the upper surface of the flange 10B of the radial dynamic pressure bearing member 10. A ring-shaped substrate 20 is coaxially arranged on the outer periphery of the radial dynamic pressure bearing member 10 with a predetermined distance from the back yoke 21, and a coil 22 is arranged between the substrate 20 and the back yoke 21. The substrate 20, the back yoke 21, and the coil 22 constitute a stator of a plane facing motor.

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

With the spindle motor having such a structure, while the above-described effects of the bearing device can be obtained, even when the motor is not driven, the magnetic force of the rotor magnet 24 is the stator. Is sucked in the axial direction, and it is difficult for the shaft 15 to come out of the bearing hole 10A 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.

In the above embodiment, the bearing device according to the present invention is applied to a polygon scanner motor, but the application of the present invention is not limited to this, and a magnetic disk device is used. Of course, it can also be applied as a spindle motor for an optical disk device or the like.
Further, although the plane-opposed motor has been described, 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 may be used.

[0036]

EXAMPLE The radial dynamic pressure bearing member 10 and the thrust slide bearing member 13a of the bearing device as described above were manufactured under the following conditions. The radial dynamic pressure bearing member 10 is
A resin obtained by filling S with 30% by weight of carbon fiber, 15% by weight of PTFE, and several% of other filler such as graphite was used as a molding material, and was produced by injection molding. The total amount of the above fillers was 50% by weight or less.

On the other hand, the thrust slide bearing member 13a is
Using a resin composition containing PA6 and PE as a molding material,
It was made by injection molding. Radial dynamic pressure bearing member 10
Has an inner diameter of 4 mmφ, an outer diameter of 7 mmφ and a wall thickness of 1.5 mm,
It was formed into a cylindrical shape having a length of 12 mm in the axial direction. However, the depths of the oil reservoirs 14A and 14B and the dynamic pressure generating groove 11 provided in the bearing hole 10A were set to about 8 μm.

FIG. 4 (a) is a diagram in which the circularity of the inner peripheral surface of the bearing hole 10A of the radial dynamic pressure bearing member 10 manufactured under the above conditions is measured. From this figure, the bearing hole 1 according to the present invention is shown.
It can be seen that the inner peripheral surface of 0 A has a roundness of 2 μm or less. Further, FIG. 4B is a diagram in which the cylindricity is measured,
From this figure, a bearing hole 10A provided with a groove 11 for generating a dynamic pressure is shown.
It can be seen that the inner peripheral surface has a cylindricity of 2 μm or less.

As described above, the bearing hole 10A of the radial dynamic pressure bearing member 10 sufficiently satisfies the molding precision required for the dynamic pressure bearing, such that the groove 11 for generating the dynamic pressure is also precisely molded. Next, Table 1 shows the comparison test results of the resin (PA6 and PE resin composition) used for the thrust slide bearing member 13a and the test piece made of other resin. The test was performed using a pin-plate type friction and wear tester, and the sliding characteristics and the friction characteristics in the unlubricated state and the lubricated state were measured for the test piece made of the resin of this example and the test piece of the comparative resin, respectively. evaluated.

The test conditions are as follows: applied load: 400 gf, sliding speed: 100 m / min, turning radius: 16 mm, mating material: SUS304, surface roughness 0.1 Ra, lubricating oil: mineral oil,
Test piece: manufactured by injection molding, diameter 6 mm, convex spherical surface SR
The resin material of each test piece was as follows. Example: Resin composition having polyamide 6 resin (PA6) and polyethylene resin (PE) Comparative example 1: Wax-added polyacetal Comparative example 2: Polyamide 6 resin (PA6) Comparative example 3: Ultra high molecular weight polyethylene (extruded) It is manufactured by machining a round bar) In addition, the wear of non-lubricated state is 0.1mm at the tip of the test piece.
Height is the sliding distance until wear and the dynamic friction coefficient μk
Was determined from the torque value generated on the test piece at that time. The wear in the lubricated state was the wear height of the tip of the test piece after a sliding distance of 1000 km, and the dynamic friction coefficient μk was calculated from the torque value of the test piece at that time.

[0041]

[Table 1]

As is clear from Table 1, the thrust slide bearing of this embodiment is superior in slidability and wear resistance to those made of other resins, and particularly wear resistance. It turns out that it is excellent. As described above, since the bearing members 10 and 13a of the bearing device according to the present invention are the resin bearings having excellent slidability and abrasion resistance, the bearings 10 and 13a are protected from impact and damage when they come into contact with the shaft at the time of starting and stopping. The thrust slide bearing member 13a, which can be suppressed, has sufficient wear resistance required for the thrust bearing surface, which is particularly susceptible to wear.

[0043]

As is apparent from the above description, according to the present invention, a radial dynamic pressure bearing member having a groove for dynamic pressure generation and having a radial bearing surface, and a thrust slide bearing member having a thrust bearing surface are provided. Can be formed by injection molding or the like using a resin as a material, so that the manufacturing cost thereof can be kept low.

Further, since it is not necessary to form a groove for generating a dynamic pressure on the outer peripheral surface of the shaft to be inserted into the bearing hole, the manufacturing cost of the shaft can be reduced, and the thrust bearing is a slide bearing. Therefore, this also simplifies the structure and reduces the number of parts, so that the cost can be reduced. Furthermore, since the radial dynamic pressure bearing member and the thrust sliding bearing member are made of resins of different materials, it is possible to select the optimum resin for each bearing member separately depending on the performance required for each bearing member. Therefore, each bearing member can be made highly precise and excellent in durability.

Further, since each bearing member is a resin bearing having excellent slidability and abrasion resistance, it is possible to suppress impact and damage when it comes into contact with the shaft during starting and stopping.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view for explaining a bearing device that is an example of an embodiment of the present invention.

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

FIG. 3 is a vertical cross-sectional view showing a state in which the bearing device of the present embodiment is incorporated in a spindle motor for a polygon scanner.

4A and 4B are diagrams showing the results of measurement of the radial dynamic pressure bearing member in the example, where FIG. 4A shows the roundness measured, and FIG. 4B shows the cylindricity measured.

FIG. 5 is an explanatory sectional view for explaining an example of a conventional bearing device.

[Explanation of symbols]

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

Claims (1)

[Claims] 1. A radial bearing surface is formed on the inner peripheral surface of a cylindrical bearing hole into which the shaft is inserted, and a groove for generating dynamic pressure is provided on the radial bearing surface, and the radial bearing surface is the shaft. A radial dynamic pressure bearing member facing the outer peripheral surface of the radial dynamic pressure bearing, and a tip end surface of the shaft fixed to an axial end of the radial dynamic pressure bearing member and inserted into the bearing hole. The thrust dynamic bearing member and the thrust plain bearing, wherein the facing portions are thrust bearing surfaces, and the thrust bearing surface faces the tip end surface of the shaft to form a thrust plain bearing. A bearing device characterized in that the member and the member are formed of different resins.