JP2004084768A - Rolling bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing device in which uneven rolling elements are hardly caused, with a very small NRR-fc component, the torque is small, and the rotational accuracy is excellent. <P>SOLUTION: A ball bearing 1 comprises an inner ring 2, an outer ring 3, a plurality of balls 4 arranged in a rolling manner between the inner ring 2 and the outer ring 3, and a holder 5 to hold the balls 4 between the rings 2 and 3. The holder 5 comprises an annular main part and a plurality of pockets provided on one side of the main part. The diameter of the pitch circle of the pockets is set to be ≥ 100.0% and ≤ 101.5% of the diameter of the pitch circle of the pockets. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rolling bearing device, and in particular, to a hard disk drive (hereinafter, referred to as HDD), a flexible disk drive (FDD), a video tape recorder (VTR), a digital audio tape recorder (DAT), and a laser beam printer (LBP). The present invention relates to a rolling bearing device suitably used for a rotation supporting portion requiring high rotational accuracy in information devices such as audio and video equipment.
[0002]
[Prior art]
In the rolling bearing device used for the above-mentioned applications, run-out (NRR) of a rotation asynchronous component is a serious problem. In particular, HDDs have an improvement rate of recording density exceeding 100% per year, and the number of tracks per inch (TPI: track per inch) is also increasing. Therefore, the NRR of motors and bearings used in HDDs is increasing. Demands for reductions are becoming more stringent. Among the NRRs, the NRR-fc component (the number of revolutions of the rolling element), which is the NRR caused by the cage and the rolling elements, is particularly important.
[0003]
As a specific device of the rolling bearing device, for example, a factor of increasing the NRR-fc component of a rolling bearing having an inner ring, an outer ring, and a rolling element will be described. First, the diameter of a ball as a rolling element of a rolling bearing is increased. Secondly, the balls are not arranged evenly in the rolling bearing (hereinafter, referred to as unequal arrangement).
First, the difference between the diameters of the balls, which is the first factor, can be suppressed to some extent by improving the processing accuracy of the balls in recent years.
[0004]
Next, the unequal arrangement of balls, which is the second factor, will be described. The unequal arrangement of the balls is caused by the cage being eccentric in the rolling bearing, and as a result, the positions of the balls are unevenly distributed. Therefore, if the cage is less likely to be eccentric in the rolling bearing or the amount of movement of the ball in the pocket of the cage is reduced, the degree of unequal arrangement can be reduced.
[0005]
On the other hand, the diameter of the pocket of the retainer is slightly larger than the diameter of the ball so that the pocket does not strongly restrain the ball. Therefore, a gap called a pocket clearance is formed between the pocket and the ball. It will intervene. The presence of the pocket allows the ball to move within the pocket. The pocket diameter is designed in consideration of conditions such as the size of the rolling bearing, the use conditions of the rolling bearing, the material of the cage, and the like.
[0006]
Therefore, in the conventional rolling bearing, the diameter of the pocket is designed to be small in order to suppress the unequal arrangement of the balls, and the amount of movement of the balls in the pocket is reduced.
[0007]
[Problems to be solved by the invention]
However, if the pocket diameter is too small, the ball and the retainer are always in contact due to manufacturing errors, and the space for holding the lubricant is reduced, and the lubricant is easily scraped off at the pocket edge. Therefore, there is a possibility that problems such as deterioration of acoustic characteristics and seizure may occur due to poor lubrication. Therefore, there is a limit to reducing the pocket diameter. When the pocket diameter is reduced, the pocket restrains the ball and the torque increases.
[0008]
Therefore, the present invention solves the problems of such a conventional rolling bearing device, and unequal arrangement of the rolling elements hardly occurs, the NRR-fc component is extremely small, the torque is reduced, and the rolling bearing is excellent in rotational accuracy. It is an object to provide a device.
[0009]
[Means for Solving the Problems]
In order to solve the above problem, the present invention has the following configuration. That is, the rolling bearing of the present invention includes a plurality of rolling elements rotatably disposed between the inner ring raceway and the outer ring raceway, and a plurality of pockets formed in an annular or cylindrical shape intermittently extending circumferentially. And a retainer rotatably holding the rolling element in the pocket, wherein the pitch circle diameter of the pocket is 100.0 times the pitch circle diameter of the bearing. % Or more.
[0010]
In this case, the pocket clearance between the pocket and the rolling element is reduced, the eccentricity of the cage is suppressed, the unequal arrangement of the rolling elements is less likely to occur, and the NRR-fc component is reduced.
On the other hand, if the pitch circle diameter of the pocket is too large than the pitch circle diameter of the bearing, the pocket restrains the ball and the torque increases. In particular, there is a problem that the lubricant is easily scraped off at the pocket edge portion, and the acoustic life is shortened due to poor lubrication.
[0011]
Therefore, if the pitch circle diameter of the pocket is set to 100.0% or more of the pitch circle diameter of the bearing and 101.5% or less, the NRR-fc component is reduced and the pocket restrains the rolling element. And the torque does not increase.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a rolling bearing device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the structure of a ball bearing 1 according to an embodiment of the present invention. FIGS. 2 to 4 show crowned cages (hereinafter, cages and cages) provided in the ball bearing 1 of FIG. FIG. 5 is a perspective view of 5).
[0013]
The ball bearing 1 includes an inner ring 2, an outer ring 3, a plurality of balls 4, which are rotatably disposed between the inner ring 2 and the outer ring 3, and a holding member that holds the ball 4 between the two wheels 2, 3. Vessel 5.
The outer peripheral portions of the annular seal plates 6 and 6 are locked to the inner peripheral surfaces of both ends of the outer ring 3, and the opening between the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 3 is , 6, the grease (not shown) existing in the space formed between the inner ring 2 and the outer ring 3 (where the balls 4 are installed) leaks to the outside or floats to the outside. This prevents dust from entering the space.
[0014]
Further, the retainer 5 includes an annular main part 8 and a plurality of pockets 9 provided on one surface of the main part 8, and the pockets 9 are arranged facing each other with an interval therebetween. It is formed from a pair of elastic pieces 10. The opposing surfaces of the pair of elastic pieces 10, 10 constituting each pocket 9 are spherical or cylindrical concave surfaces.
[0015]
Then, the balls 4 are pushed between the pair of elastic pieces 10 and 10 while the gap between the elastic pieces 10 and 10 is elastically expanded. Can be held.
Such a retainer 5 is integrally formed by molding a resin material by a method such as injection molding.
[0016]
Examples of the resin material include polyamide resins such as nylon 66 and nylon 46, fluorine resins such as PTFE and ETFE, ether ketone resins such as polyetheretherketone resin (PEEK), polyethersulfone resin (PES), and polyethersulfone resin (PES). Oxymethylene resin (POM), polybutylene terephthalate resin (PBT), linear polyphenylene sulfide resin (L-PPS), polyamideimide resin (PAI), polyetherimide resin (PEI), thermoplastic polyimide resin (TPI), And polyether nitrile resin (PEN).
[0017]
A reinforcing material such as a fiber may be added to these resin materials in order to impart strength. Examples include glass fibers, carbon fibers, aramid fibers, and various whiskers such as potassium titanate. The amount of the reinforcing material to be added may be appropriately selected in consideration of the strength, moldability, assemblability, and the like of the cage. Usually, it is 5 to 40% by weight.
Further, a lubricant such as a lubricating oil may be added to these resin materials in order to impart lubricity. When molding the cage, it is desirable to improve the accuracy of the cage by using a multipoint gate. Note that the retainer 5 may be made of a metal material.
[0018]
The cage 5 that is arranged between the inner ring 2 and the outer ring 3 and that holds the ball 4 so as to be able to roll freely uses the pitch circle diameter PCD1 of the pocket 9 as 100% of the pitch circle diameter PCD2 of the ball bearing 1. The size is not less than 0.0% and not more than 101.5%.
For reference, FIG. 10A shows the clearance between the pocket 9 and the ball 4 when the pitch circle diameter PCD1 of the pocket 9 and the pitch circle diameter PCD2 of the ball bearing 1 are the same. (B) shows the clearance between the pocket 9 and the ball 4 when the pitch circle diameter PCD1 of the pocket 9 is set to 101.0% of the pitch circle diameter PCD2 of the ball bearing 1.
[0019]
By setting the pitch circle diameter PCD1 of the pocket 9 to 100.0% or more of the pitch circle diameter PCD2 of the ball bearing 1, the clearance between the pocket 9 and the ball 4 becomes small, and the whirling caused by the eccentricity of the retainer 5 is reduced. This prevents the unequal arrangement of the balls 4 from occurring. In addition, the eccentricity of the retainer 5 is suppressed, and the NRR-fc component can be easily achieved without particularly reducing the pocket clearance.
[0020]
Furthermore, by setting the pitch circle diameter PCD1 of the pocket 9 to be 101.5% or less of the pitch circle diameter PCD2 of the ball bearing 1, the pocket 9 does not restrain the ball 4 and prevents an increase in torque. Can be.
As shown in FIG. 3, chamfers 11 and 12 may be provided on the outer edge of the pocket 9. Further, as shown in FIG. 4, a projection 13 may be provided on a part of the concave surface of the pocket 9. Then, a surface roughness of Ra: 1 to 3 μm and Rt: about 5 to 20 μm is formed so that the lubricating oil easily accumulates on the surface in the pocket 9, thereby improving lubricity.
[0021]
Next, the result of calculating the NRR-fc component of the ball bearing 1 having the above configuration will be described. This NRR-fc component moves the ball 4 to the limit (contacts the pocket) in the eccentric direction of the cage 5 in the pocket of the cage 5 when the cage is maximally eccentric in the radial direction. 4 is obtained assuming that the unequal array of 4 is maximized (see FIG. 5).
[0022]
The graph of FIG. 6 shows that the ball bearing 1 of the first embodiment uses a bearing having an inner diameter of 4 mm, an outer diameter of 10 mm, a width of 2.6 mm, a ball diameter of 1/16 inch and eight balls, and the pitch circle of the pocket 9. FIG. 14 shows a calculation result of an NRR-fc component obtained by changing the diameter PCD1. FIG. In the calculation of the NRR-fc component, the ratio of the diameter of the pocket 9 of the retainer to the diameter of the ball 4 (pocket diameter / ball diameter) was used as a scale indicating the size of the pocket clearance.
[0023]
The horizontal axis of this graph is the pocket diameter / ball diameter, and the vertical axis is the NRR-fc component. The straight lines 60 to 69 in this graph show the results of changing the ratio (PCD1 / PCD2) between the pitch circle diameter PCD1 of the pocket 9 and the pitch circle diameter PCD2 of the ball bearing 1. And the straight line 60 is the case where the ratio of PCD1 / PCD2 is 98.0%, the straight line 61 is also 98.5%, the straight line 62 is 99.0%, and the straight line 63 is 99.5%. The bold straight line 64 is also 100.0%, the straight line 65 is also 100.5%, the straight line 66 is also 101.0%, the straight line 67 is also 101.5%, and the straight line 68 is In the case of 102.0%, the straight line 69 is also in the case of 102.5%.
[0024]
From the graph of FIG. 6, if the ratio (PCD1 / PCD2) of the pitch circle diameter PCD1 of the pocket 9 to the pitch circle diameter PCD2 of the ball bearing 1 is 100.0% or more (straight line 64 to straight line 69), the NRR-fc component is obtained. It can be seen that the NRR-fc component increases when PCD1 / PCD2 is less than 100% (straight line 60 to straight line 63).
[0025]
Here, the cage 5 in which the PCD1 / PCD2 is 0.5% intervals from 100.0% to 102.5% is prototyped, and the result of the torque measurement is shown in the graph of FIG. The cage 5 has a pocket diameter of 10% of the ball diameter, and the measurement conditions are as follows: inner ring rotation 4200 r / min, preload 7.8 N, and two bearings.
From the graph of FIG. 7, the torque value is small when PCD1 / PCD2 is 100.0%, 100.5%, and 101.0%, slightly increased at 101.5%, and is increased when it exceeds 101.5%. Is rapidly increased. This is because when PCD1 / PCD2 is larger than 101.5%, the pocket clearance becomes smaller, the ball 4 and the pocket 9 are more likely to come into contact with each other, and the torque is rapidly increased.
[0026]
Therefore, as is clear from the graphs of FIGS. 6 and 7, if the pitch circle diameter PCD1 of the pocket 9 is set to 100.0% to 101.5% of the pitch circle diameter PCD2 of the ball bearing 1, the inequality of the ball 4 becomes uneven. It becomes difficult to form the arrangement, the NRR-fc component is reduced, and the ball bearing 1 with small torque and excellent rotation accuracy can be obtained.
Next, the result of the second embodiment in which the NRR-fc component was calculated in the same manner as described above using another ball bearing 1 having a different dimension from the ball bearing 1 used in the first embodiment, This is shown in the graph of FIG. The ball bearing 1 according to the second embodiment is a bearing having an inner diameter of 5 mm, an outer diameter of 13 mm, a width of 4 mm, a ball diameter of 2 mm, and eight balls.
[0027]
The straight lines 71 to 79 in FIG. 8 show the results obtained by changing the ratio (PCD1 / PCD2) between the pitch circle diameter PCD1 of the pocket 9 and the pitch circle diameter PCD2 of the ball bearing 1. When the ratio of PCD1 / PCD2 is 98.5%, the line 72 is 99.0%, the line 73 is 99.5%, and the bold line 74 is 100.0%. , The straight line 75 is also 100.5%, the straight line 76 is also 101.0%, the straight line 77 is also 101.5%, the straight line 78 is also 102.0%, and the straight line 79 is The same applies to 102.5%.
[0028]
From the graph of FIG. 8, when the ratio (PCD1 / PCD2) of the pitch circle diameter PCD1 of the pocket 9 to the pitch circle diameter PCD2 of the ball bearing 1 is 100.0% or more (straight line 74 to straight line 79), the NRR-fc component is obtained. It can be understood that the NRR-fc component increases when PCD1 / PCD2 is less than 100% (straight lines 71 to 73).
[0029]
A prototype of the retainer 5 in which PCD1 / PCD2 has a 0.5% interval from 100.0% to 102.5% and a torque measurement is shown in a graph of FIG. 9 shows that the torque value is PCD1. It was found that when / PCD2 was 100.0%, 100.5%, and 101.0%, the torque value was small, and when it exceeded 101.5%, the torque value suddenly increased. This is because, similarly to the first embodiment, when PCD1 / PCD2 is larger than 101.5%, the pocket clearance is reduced, the ball 4 and the pocket 9 are more likely to come into contact with each other, and the torque is rapidly increased. Because.
[0030]
Therefore, also in the second embodiment, when the pitch circle diameter PCD1 of the pocket 9 is set to 100.0% to 101.5% of the pitch circle diameter PCD2 of the ball bearing 1, uneven arrangement of the balls 4 is less likely to occur. The NRR-fc component is reduced, and the ball bearing 1 with small torque and excellent rotation accuracy can be obtained.
Note that the present embodiment is an example of the present invention, and the present invention is not limited to the present embodiment.
[0031]
For example, in the present embodiment, a ball bearing has been described as an example, but the present invention can be applied to various types of rolling bearings. For example, radial rolling bearings such as angular ball bearings.
The same effect can be obtained not only in the rolling bearing but also in a bearing unit in which a raceway surface on which a rolling element rolls is formed on a shaft or a sleeve.
[0032]
Further, the shape and type of the cage, the type of the resin material, and the like are not limited to the present embodiment as long as the objects of the present invention can be achieved.
[0033]
【The invention's effect】
As described above, according to the rolling bearing device of the first aspect of the present invention, the pitch circle diameter of the pocket is set to 100.0% or more of the pitch circle diameter of the bearing. Irregular arrangement of moving objects is less likely to occur, and reduction of the NRR-fc component can be easily achieved.
[0034]
Further, according to the rolling bearing device of the second aspect, the pitch circle diameter of the pocket is set to 100.0% or more and 101.5% or less of the pitch circle diameter of the bearing, so that the effect of the first aspect can be obtained. In addition to this, the pocket does not restrict the rolling element, and an increase in torque can be prevented.
Therefore, the rolling bearing device of the present invention has very excellent rotational accuracy.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a structure of a ball bearing which is an embodiment of a rolling bearing device of the present invention.
FIG. 2 is a perspective view of a crown cage provided in the ball bearing of FIG. 1;
FIG. 3 is a perspective view showing a modified example of the crown type cage of FIG. 2;
FIG. 4 is a perspective view showing another modification of the crown-shaped retainer of FIG. 2;
FIG. 5 is a conceptual diagram showing a state of a ball in which a crown-shaped cage is eccentric and is unequally arranged.
FIG. 6 is a graph showing the value of the NRR-fc component when the ratio between the pitch circle diameter of the pocket and the pitch circle diameter of the bearing changes in the ball bearing.
7 is a graph showing torque values when the ratio between the pitch circle diameter of the pocket and the pitch circle diameter of the bearing changes in the ball bearing of FIG. 6;
FIG. 8 is a graph showing the value of the NRR-fc component when the ratio between the pitch circle diameter of the pocket and the pitch circle diameter of the bearing changes in the ball bearing of another embodiment.
9 is a graph showing torque values when the ratio between the pitch circle diameter of the pocket and the pitch circle diameter of the bearing changes in the ball bearing of FIG. 8;
FIG. 10 is a view showing the clearance between the pocket and the ball when the pitch circle diameter of the pocket and the pitch circle diameter of the bearing are changed.
[Explanation of symbols]
1 ball bearings (rolling bearing devices)
2 inner ring 3 outer ring 4 balls (rolling element)
5 Cage 9 Pocket PCD1 Pitch circle diameter of pocket PCD2 Pitch circle diameter of bearing

Claims (2)

A plurality of rolling elements rotatably disposed between the inner raceway and the outer raceway, and a plurality of pockets formed in an annular or cylindrical shape intermittently in the circumferential direction; And a retainer for rollingly holding the rolling element in the rolling bearing device,
A rolling bearing, wherein the pitch circle diameter of the pocket is 100.0% or more of the pitch circle diameter of the bearing. 2. The rolling bearing device according to claim 1, wherein the pitch circle diameter of the pocket is set to a size of 101.5% or less of the pitch circle diameter of the bearing.

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