JP2006194414A - Antifriction bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antifriction bearing with excellent acoustic performance and rotatability as well as good fretting resistance at low cost. <P>SOLUTION: A deep groove ball bearing 1 includes an outer ring 2, an inner ring 3 and a plurality of balls 4 as rolling elements arranged between the outer ring 2 and the inner ring 3 in such a manner that they can roll freely. The outer ring 2 and the inner ring 3 are formed of high-carbon chromium bearing-steel. The balls 4 are formed of martensitic stainless steel in which the size of eutectic carbide is 10μm or less, and the sphericity of the balls is 25nm or less and the surface roughness thereof is 4nmRa or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing optimal for a small motor bearing used in information equipment such as a hard disk drive (HDD) device.

  Conventionally, as rolling bearing materials, bearing steel such as SUJ2, martensitic stainless steel such as SUS440C or 13Cr, and case-hardened steel such as SCr420 or SCM420 are used. For example, HDD devices, video tape recorders, etc. For small motor bearings used in information equipment such as fan motors and audio / video equipment, quietness (acoustic performance), rotational performance such as non-repeatable run out (NRRO), anti-fretting High performance is required in many items such as performance, and martensitic stainless steel that is excellent in anti-fretting performance is used to prevent torque fluctuations and torque spikes due to fretting wear.

  However, in recent years, with the increase in the density of HDD devices, the disk thickness has been increased and the rigidity of the disk has been strengthened. This has resulted in an increase in disk inertia, or a head for cost reduction. Due to the fact that the disk runout increases with the reduction in the number, it is desired to further improve the anti-fretting performance of the small motor bearing.

And, as a method to improve the anti-fretting performance, (1) Mix sulfur grease such as molybdenum sulfide and zinc sulfide as an extreme pressure additive in the grease to be sealed, and (2) Enclose the grease on the cage in the groove. And (3) changing the material of the rolling element to ceramic, and (4) nitriding the surface of the rolling element. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 11-303874

  However, if grease is mixed with sulfur compounds such as molybdenum sulfide and zinc sulfide as extreme pressure additives, the acoustic performance of the rolling bearing may be reduced, and if grease is sealed in the groove, the rolling bearing The dynamic torque increases and the runout of the rotation asynchronous component of the cage (NRROfc component) may become unstable, and the rotational performance of the rolling bearing may be degraded. Also, the rolling element is made of ceramic, or the surface of the rolling element If the nitriding treatment is applied to the rolling bearing, there is a risk of increasing the cost of the rolling bearing.

In addition, conventional stainless steel tends to lower the processing accuracy due to the presence of a large amount of coarse eutectic carbide enriched in Cr, and it is a rolling bearing that depends on the shape accuracy of inner and outer rings and rolling elements. In terms of acoustic performance and rotational performance, stainless steel products are inferior to bearing steel products, for example.
On the other hand, Patent Document 1 finds a relationship between C and Cr concentrations that can suppress the formation of coarse eutectic carbides, and further sets the content of Si, Mn, Cr, Mo, V, etc. to a predetermined threshold. Although stainless steel has been disclosed to improve workability by keeping it within the value, there is a quantitative description of the machining accuracy of inner and outer rings and rolling elements that are directly related to the acoustic performance and rotational performance of rolling bearings. Not done.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a rolling bearing that has excellent acoustic performance and rotational performance and also has excellent anti-fretting performance at low cost.

  In order to achieve the above-described object, a rolling bearing according to the present invention is a rolling bearing comprising an outer ring, an inner ring, and a plurality of rolling elements that are disposed between the outer ring and the inner ring so as to be capable of rolling. The outer ring and the inner ring are made of high carbon chrome bearing steel, and the rolling element is made of martensitic stainless steel having a eutectic carbide size of 10 μm or less, and has a sphericity of 25 nm or less and a surface roughness. It is characterized by being 4 nmRa or less.

According to the rolling bearing of the present invention, the inner and outer rings are made of high carbon chromium bearing steel, and the rolling elements are made of martensitic stainless steel having a eutectic carbide size of 10 μm or less. Both inner and outer rings and rolling elements can be processed with high accuracy. In particular, it is possible to improve the processing accuracy of stainless steel, which has conventionally been difficult to perform with high accuracy, to the same processing accuracy as that of bearing steel. The sphericity of rolling elements (balls) is 25 nm or less, and the surface roughness is 4 nm Ra. It becomes possible to process with the following high precision. Thereby, it is possible to provide a rolling bearing having acoustic performance and rotational performance equivalent to those of a rolling bearing in which inner and outer rings and rolling elements are made of high carbon chrome bearing steel, and also having excellent anti-fretting performance.
In addition, relatively high-priced martensitic stainless steel is used for rolling elements with simple shapes, and high-carbon chromium bearing steel is used for inner and outer rings that have a complicated shape and larger volume than rolling elements. In addition, a rolling bearing can be provided at a lower cost than when martensitic stainless steel is used for both rolling elements.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a deep groove ball bearing according to an embodiment of the present invention.
As shown in FIG. 1, a deep groove ball bearing 1 according to an embodiment of the present invention has an outer ring 2 and an inner ring 3, and an outer ring raceway surface 2 a formed on the inner circumferential surface of the outer ring 2 and the outer circumference of the inner ring 3. A plurality of balls 4 that are rolling elements are held by a cage 5 between the inner ring raceway surface 3 a formed on the surface so as to freely roll. Seals 6 are disposed at both axial ends between the outer ring 2 and the inner ring 3.

The outer ring 2 and the inner ring 3 are made of high carbon chrome bearing steel such as SUJ2. Further, the balls 4 as rolling elements are made of martensitic stainless steel having a eutectic carbide size of 10 μm or less, and are processed to have a sphericity of 25 nm or less and a surface roughness of 4 nmRa or less.
Examples of the martensitic stainless steel in which the size of the eutectic carbide is 10 μm or less include, by weight%, C: 1.5% or less, Cr: 10% or more and 20% or less, Mn: 0.1% or more and 0 An alloy steel containing 0.8% or less, Si; 0.1% or more and 1.0% or less, N: less than 0.2% can be exemplified.

According to this embodiment, the outer ring 2 and the inner ring 3 are formed of high carbon chrome bearing steel, and the balls 4 that are rolling elements are formed of martensitic stainless steel having a eutectic carbide size of 10 μm or less. Since it did in this way, the outer ring | wheel 2, the inner ring | wheel 3, and the ball | bowl 4 can be processed with high precision together. In particular, it is possible to improve the processing accuracy of stainless steel, which has conventionally been difficult to perform with high accuracy, to the same processing accuracy as that of bearing steel, and the ball 4 has a high sphericity of 25 nm or less and a surface roughness of 4 nmRa or less. It becomes possible to process with high accuracy. Thereby, it is possible to provide the deep groove ball bearing 1 having the same acoustic performance and rotational performance as the bearing in which the inner and outer rings and the rolling elements are made of high-carbon chromium bearing steel, and also having excellent anti-fretting performance.
In addition, a relatively expensive martensitic stainless steel is used for the ball 4 having a simple shape, and a high-carbon chromium bearing steel is used for the outer ring 2 and the inner ring 3 having a complicated shape and a larger volume than the ball 4. The deep groove ball bearing 1 can be provided at a lower cost than when martensitic stainless steel is used for both the inner and outer rings and the rolling elements.

  In order to confirm the effect of the present invention, the outer ring and the inner ring are formed from SUJ2, and the balls as rolling elements are formed from martensitic stainless steel having a eutectic carbide size of 10 μm or less. In addition, for comparison with the embodiment, each test performed on a comparative example in which all of the outer ring, the inner ring, and the rolling element are formed from SUJ2 will be described. The rolling bearings of the examples and comparative examples are deep groove ball bearings having an outer diameter of 13 mm, an inner diameter of 5 mm, and a width of 5 mm.

2 is a graph showing the measurement result of the initial bearing G value (vibration acceleration), FIG. 3 is a graph showing the measurement result of NRRO, FIG. 4 is a graph showing the measurement result of NRROfc (NRRO of the cage), and FIG. 5 is NRROball. FIG. 6 is a graph showing the measurement result of NRROball + (ball NRRO).
FIGS. 7 to 8 change with the test time in an endurance test in which 1.5 kgf of preload was applied to the deep groove ball bearings of the example and the comparative example and rotated at a rotational speed of 5400 rpm in an environment of 70 ° C. FIG. 7 is a graph showing a case where a deep groove ball bearing using a martensitic stainless steel ball having an eutectic carbide of 10 μm or less of the example is lubricated with a carbonate ester grease (HF3 grease). 8 is a graph when a deep groove ball bearing using the SUJ2 ball of the comparative example is lubricated with a carbonate ester grease (HF3 grease).
FIG. 9 is a graph showing the anti-fretting performance using the G value increase amount as an index.

  As shown in FIG. 2, regarding the initial G value of the bearing, the deep groove ball bearing of the example shows the same value as the deep groove ball bearing of the comparative example, and it can be seen that there is little vibration and excellent acoustic performance.

  As shown in FIG. 3 to FIG. 6, for each NRRO, the deep groove ball bearing of the example shows the same value as the deep groove ball bearing of the comparative example, and the runout of the rotational asynchronous component is small and stable. It turns out that it is excellent in performance.

  As shown in FIGS. 7 and 8, the deep groove ball bearings of the examples and comparative examples tend to increase in G value as the test time elapses. It can be seen that there is little change in the G value compared to the deep groove ball bearing, and it has excellent durability performance.

  As shown in FIG. 9, regarding the anti-fretting performance using the increase in G value as an index, the deep groove ball bearing of the example has a significantly small increase in the G value compared to the deep groove ball bearing of the comparative example, and is resistant to fretting. It turns out that it is excellent in performance.

  From the above results, it was proved that the rolling bearing according to the present invention has excellent acoustic performance and rotational performance as a whole, and also has excellent anti-fretting performance.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  For example, although the rolling bearing has been described as a deep groove ball bearing in the above-described embodiment, the present invention is not limited to this, and is applicable to other types of rolling bearings such as a cylindrical roller bearing, a needle roller bearing, and a conical bearing. be able to.

It is a longitudinal cross-sectional view which shows one Embodiment of the rolling bearing of this invention. It is a graph which shows the measurement result of the bearing initial G value (vibration acceleration) of an Example and a comparative example. It is a graph which shows the measurement result of NRRO of the deep groove ball bearing of an example and a comparative example. It is a graph which shows the measurement result of NRROfc (NRRO of a cage) of the deep groove ball bearing of an example and a comparative example. It is a graph which shows the measurement result of NRROball- (ball NRRO) of the deep groove ball bearing of an example and a comparative example. It is a graph which shows the measurement result of NRROball + (ball NRRO) of the deep groove ball bearing of an example and a comparative example. It is a graph at the time of lubricating the deep groove ball bearing of an Example with carbonate ester system grease (HF3 grease), showing the measurement result of G value which changes with test time in the endurance test of the deep groove ball bearing of an example. It is a graph at the time of lubricating the deep groove ball bearing of a comparative example with carbonate ester system grease (HF3 grease), showing the measurement result of G value which changes with test time in the endurance test of the deep groove ball bearing of a comparative example. It is a graph which shows the fretting-proof performance which used the amount increase of G value of the deep groove ball bearing of the Example and the comparative example as a parameter | index.

Explanation of symbols

1 Deep groove ball bearing (rolling bearing)
2 Outer ring 3 Inner ring 4 Ball (rolling element)
5 Cage

Claims (1)

A rolling bearing comprising an outer ring, an inner ring, and a plurality of rolling elements arranged to roll between the outer ring and the inner ring,
The outer ring and the inner ring are made of high carbon chrome bearing steel,
The rolling bearing is characterized in that the rolling element is made of martensitic stainless steel having a eutectic carbide size of 10 μm or less, and has a sphericity of 25 nm or less and a surface roughness of 4 nmRa or less.

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