JP2003113843A - Roller bearing and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the acoustic service life of a bearing, and to satisfy the initial acoustic performance. SOLUTION: In a roller bearing 10 with a plurality of rolling bodies 13 disposed between an outer ring 11 and an inner ring 12, at least one of raceway surfaces of the outer ring 11 and the inner ring 12 has a large number of groove-like recessed parts 5 of the depth of >=0.03 μm and <=0.08 μm, and the pitch of 5-20 μm, and a smooth surface 4 with the roughness of <=0.005 μm Ra by the center line average height at parts other than the groove-like recessed parts 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in rolling bearings used in precision equipment such as HDDs (hard disk drives) and VTRs.

[0002]

2. Description of the Related Art Ball bearings used in spindle motors of HDDs and VTRs are required to have excellent rotational performance and acoustic performance. However, this type of ball bearing is exposed to high temperatures due to the heat generated by the high speed rotation of the motor. In many cases, the viscosity of the lubricating oil will be low and a sufficient oil film will not be formed on the contact surface. As a result, there is a problem that metal contact occurs between the balls and the raceway surface, resulting in increased bearing vibration and sound, which impedes normal operation of the bearing.

Therefore, as a measure for improving the lubrication performance of rolling bearings, as disclosed in Japanese Unexamined Patent Publication No. 1-272020,
There has been proposed a rolling bearing in which a large number of groove-shaped recesses are formed on the raceway surface by means such as superfinishing so as to enhance the retaining force of the lubricant.

[0004]

However, in the conventional rolling bearing described above, the specifications such as the depth of the groove-shaped recess and the roughness of the smooth surface other than the groove-shaped recess are naturally limited at present in view of processing. Therefore, although the groove-shaped recesses provide the effect of improving the lubricity, the effect of improving the initial acoustic performance, which is important for HDDs and VTRs, is not sufficient, and in recent years, the performance requirements for bearings have become increasingly severe. There is an unsolved problem that it is difficult to deal with the growing HDD and VTR.

The present invention has been made in order to eliminate such inconvenience, and appropriately sets the specifications of the depth of the groove-shaped recess formed on the raceway surface and the roughness of the smooth surface other than the groove-shaped recess. It is an object of the present invention to provide a rolling bearing and a method of manufacturing the same that can improve the lubrication performance, prolong the acoustic life of the bearing, and satisfy the initial acoustic performance.

[0006]

In order to achieve the above object, the invention according to claim 1 is a rolling bearing in which a plurality of rolling elements are arranged between an outer ring and an inner ring. At least one of the orbital surfaces of is at a depth of 0.03 μm or more and 0.08 μm or less, pitch 5
It is characterized in that it has a large number of groove-shaped recesses of up to 20 μm and a smooth surface having a center line average roughness of 0.005 μmRa or less in a portion excluding the groove-shaped recesses.

According to a second aspect of the present invention, in the first aspect, the plurality of groove-shaped recesses extend in the circumferential direction of the raceway surface and are arranged parallel to each other in the axial direction. . According to a third aspect of the present invention, there is provided a rolling bearing including a step of forming a groove-like recess on the raceway surface by subjecting at least one of the raceway surfaces of the outer race and the inner race to a grinding stone. A method, wherein the whetstone,
By using a superfinishing grindstone used in the final step of multistage superfinishing, and processing the raceway surface with the superfinishing grindstone, the raceway surface has a depth of 0.03 μm or more and 0.08 μm or less and a pitch of 5 to 20 μm. The present invention is characterized in that a large number of groove-shaped recesses and a smooth surface having a center line average roughness of 0.005 μmRa or less are formed in a portion excluding the groove-shaped recesses.

According to a fourth aspect of the present invention, in the third aspect, the superfinishing grindstone has a total weight of the abrasive grains of the grindstone of 100.
, 50 to 90% of the weight is silicon carbide abrasive grains,
One of the fused alumina abrasive grains and the mixed abrasive grains thereof is used as the first abrasive grain, and the remaining 50 to 10% of the weight is an average of 0.5 to 2 times the average abrasive grain size of the first abrasive grain. A cubic boron nitride abrasive grain or a diamond abrasive grain having an abrasive grain size is used as a second abrasive grain, and the second abrasive grain and the first abrasive grain are mixed and bonded by a binder for a vitrified grindstone. It is characterized by

According to a fifth aspect of the present invention, in the fourth aspect, the first abrasive grains having an average abrasive grain size of 0.6 to 2 μm are replaced with the second abrasive grains having an average abrasive grain size of 1 to 4 μm. It is characterized in that they are mixed and bonded by the binder for vitrified grindstone.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to the drawings. Ball bearing 10 of this embodiment
As shown in FIG. 1, a plurality of rolling elements 13 are disposed between an outer ring 11 and an inner ring 12 via a cage 14, and each raceway surface of the outer ring 11 and the inner ring 12 has With reference to FIG. 2, a large number of groove-shaped recesses 5 having a depth D of 0.03 μm or more and 0.08 μm or less and a pitch P of 5 to 20 μm, and the roughness except for the groove-shaped recesses 5 is a center line. A smooth surface 4 having an average roughness of 0.005 μmRa or less is formed.

As a result, the groove-shaped recess 5 for holding the lubricant is formed.
Depth and roughness of the smooth surface 4 other than the groove-like recess 5 are set appropriately, lubrication performance is improved, and oil film runout does not occur even under high temperature and long-term use conditions, prolonging the acoustic life of the bearing. HD that requires low noise and high rotation accuracy while also satisfying initial acoustic performance.
It can be suitably used as a ball bearing for a D or VTR.

Further, in this embodiment, since the large number of groove-shaped recesses 5 extend along the circumferential direction of the raceway surface and are arranged in parallel to each other in the axial direction, the groove-shaped recesses 5 are raced. Compared with one in which the groove-shaped recesses 5 are arranged so as to intersect each other at an angle with respect to the circumferential direction of the surface, and one in which the groove-shaped recesses 5 are arranged at a right angle to the circumferential direction, It is possible to reduce the frequency with which the rolling elements pass through the groove-shaped recess 5,
As a result, it is possible to further improve the rotation accuracy and the acoustic accuracy.

Next, the groove-shaped recess 5 and the smooth surface 4
A method of forming the will be described. Ball bearings for HDDs and VTRs, which require low noise and high rotation accuracy, need to improve the roughness of the raceway surface. Therefore, the process of removing the harmful grinding surface with rough roughness and the process for obtaining the required roughness Efficiently manufactured by the multi-stage super finishing consisting of and. In multi-stage superfinishing, it is common to use different grindstones suitable for the step of removing the grinding surface and the step of improving the roughness, a coarse grindstone is used in the step of removing the grinding surface and a fine grindstone in the step of improving the roughness. .

If a deep groove-shaped recess formed after the step of removing the ground surface is processed so as to be left in the subsequent step of improving the roughness, a predetermined groove-shaped recess and a smooth surface can be obtained. It is difficult to properly set the specifications of the roughness of the smooth surface 4 other than the concave portion 5 and to form it stably and efficiently. Therefore, in this embodiment, by using the following superfinishing stone in the final step of multistage superfinishing,
The groove-shaped recess 5 and the smooth surface 4 are formed on the raceway surface.

That is, in this superfinishing whetstone, when the total weight of the whetstone of the whetstone is 100, 50 to 90% of the weight is either silicon carbide abrasive grains, fused alumina abrasive grains or mixed abrasive grains thereof. As one, this is the first abrasive grain, and the remaining 50 to 10
% Of cubic boron nitride abrasive grains or diamond abrasive grains having an average abrasive grain size of 0.5 to 2 times the average abrasive grain size of the first abrasive grains as the second abrasive grains. Abrasive grains and the first
The abrasive grains are mixed and bonded with a binder for vitrified grindstone.

In this case, the first abrasive grains having an average abrasive grain size of 0.6 to 2 μm are mixed with the second abrasive grains having an average abrasive grain size of 1 to 4 μm, and the mixture for the vitrified grindstone is used. It is preferably bound. The present invention is not limited to the above-mentioned embodiment, and can be appropriately modified without departing from the gist of the present invention. For example, in the above embodiment, a ball bearing is adopted as the rolling bearing, but the present invention is not limited to this, and the present invention may be applied to a roller bearing or other rolling bearings.
Further, in the above-described embodiment, the case where the groove-shaped recess 5 and the smooth surface 4 are formed on each raceway surface of the outer race 11 and the inner race 12 is taken as an example, but the invention is not limited to this, and the outer race may be used depending on the application. The groove-shaped recess 5 and the smooth surface 4 may be formed on any of the raceway surfaces of the inner ring 11 and the inner ring 12.

[0017]

EXAMPLE First, referring to FIG. 3 and FIG.
A fused alumina abrasive grain (first abrasive grain) 1 of μm and a cubic boron nitride abrasive grain (second abrasive grain) 2 having an average grain size of 3 μm are mixed at a weight ratio of 5: 5 to form a vitrified grindstone. The super-finishing grindstone U was formed by binding with the binder 3 for use. It should be noted that appropriate pores are included between the fused alumina abrasive grain 1, the cubic boron nitride abrasive grain 2, and the binder 3 for vitrified grindstone.

As shown in FIG. 4, the surface of the grindstone when superfinishing is performed by the superfinishing grindstone U, as shown in FIG. 4, shows the hardness of the abrasive grains of the cubic boron nitride abrasive grains 2 and the fused alumina abrasive grains 1. Due to the difference and difference in average abrasive grain size, fused alumina abrasive grain 1
Is increased, the protrusion amount h of the cubic boron nitride abrasive grains 2 is appropriately obtained, and the ratio of the protruding cubic boron nitride abrasive grains 2 is also appropriately obtained.

FIG. 5 shows a cross section of the surface to be machined when superfinishing is carried out using the above-mentioned superfinishing grindstone U. A smooth surface 4 of 0.005 μmRa or less is formed, and a depth of 0.03 μm or more and 0.08 is formed by the cubic boron nitride abrasive grains 2.
Numerous groove-shaped recesses 5 with a pitch P of 5 to 20 μm or less
Is formed.

Next, the test bearing J shown in FIG. 9 was mounted on the grease life tester shown in FIG. 10 and a rotation test was conducted. The test bearing J is a ball bearing having an inner diameter of 5 mm, an outer diameter of 13 mm, a width of 3 mm, and a ball diameter of 2 mm, in which a plurality of rolling elements 33 are arranged via a cage 34 between an outer ring 31 and an inner ring 32. The shield 35 is attached only to one end side in the direction.

Here, in this embodiment, the test bearing J in which the groove-shaped recess 5 and the smooth surface 4 are formed by the superfinishing grindstone U on each raceway surface of the outer ring 31 and the inner ring 32 is taken as an example, and the outer ring 31 is used. And a test bearing J in which each raceway surface of the inner ring 32 has a finished surface having a centerline average roughness of 0.010 μmRa (see FIG. 6) is referred to as Conventional Example 1, and each raceway surface of the outer ring 31 and the inner ring 32 has a centerline average roughness. Roughness 0.015 μmRa
(See FIG. 7) A test bearing J having a finished surface having groove-shaped recesses is referred to as Conventional Example 2, and the center line average roughness of each raceway of the outer ring 31 and the inner ring 32 is 0.005 μmRa (see FIG. 8). A test bearing J having a finished surface was designated as Conventional Example 3.
In addition, a test bearing J was filled with a grease composition in which a base oil was a carbonic acid ester and a thickener was lithium soap, and a test was conducted by rotating the inner ring.

The grease life tester rotates the test bearing J put in the housing H by the power of the motor 23 via the rubber belt 21 and the pulley 22. Then, the grease life tester is housed in a constant temperature bath adjusted to 60 ° C., and the inner ring 32 of the test bearing J in the housing H is stored.
Was rotated at a rotation speed of 5800 rpm (axial load 10 N) for a predetermined time. Housing H after a predetermined time
The test bearing J was taken out from the above, and the acoustic characteristics were investigated by mounting the Anderon meter on a measuring instrument modified so as to be evaluated by the vibration acceleration (mG). Survey results are shown in FIG. 11 and FIG.
2 shows.

FIG. 11 shows the measurement results of Conventional Examples 1 to 3, and as is clear from the figure, Conventional Example 2 in which a groove-like recess is formed on the raceway surface has a normal finished surface on the raceway surface. Although the increase in sound is smaller than that in Conventional Example 1, it can be seen that the initial sound is high due to the influence of the groove-shaped recess. Also,
Conventional Example 3 having a finished surface with a roughness half that of Conventional Example 1 on the raceway surface has good initial roughness due to improved roughness, but groove-shaped recesses are formed on the raceway surface. It can be seen that the increase in sound is larger than that of the formed Conventional Example 2.

On the other hand, in the embodiment shown in FIG. 12, the acoustic increase was suppressed to be lower than in the conventional examples 1 to 3 even in the high temperature and long time rotation test, and the finished surface was improved in the initial acoustic performance. It can be seen that the level is the same as that of Conventional Example 2.

[0025]

As is apparent from the above description, according to the present invention, the specifications of the depth of the groove-shaped recess holding the lubricant and the roughness of the smooth surface other than the groove-shaped recess are appropriately set. In addition, the lubrication performance is improved, the oil film is not broken even under high temperature and long time use conditions, and the acoustic life of the bearing can be extended, and the initial acoustic performance can be satisfied.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view for explaining a ball bearing which is an example of an embodiment of the present invention.

FIG. 2 is an explanatory sectional view for explaining a groove-shaped concave portion and a smooth surface of an inner ring raceway surface of the ball bearing.

FIG. 3 is an explanatory perspective view for explaining a superfinishing stone used in the present invention.

FIG. 4 is an explanatory cross-sectional view for explaining how a groove-shaped recess and a smooth surface are formed on a surface to be processed by the superfinishing grindstone.

FIG. 5 is a cross-sectional view of a surface to be processed that has been superfinished by the superfinishing stone.

FIG. 6 is a roughness curve diagram of the races of the inner ring and the outer ring in the case of the ball bearing of Conventional Example 1 when the roughness of the center line average roughness is 0.010 μmRa.

FIG. 7 is a roughness curve diagram of the races of the inner ring and the outer ring in the ball bearing of Conventional Example 2 when the roughness of the center line average roughness is 0.015 μmRa.

FIG. 8 is a roughness curve diagram of the races of the inner ring and the outer ring in the case of the ball bearing of Conventional Example 3 when the roughness of the center line average roughness is 0.005 μmRa.

FIG. 9 is a sectional view of a ball bearing used as a test bearing.

FIG. 10 is an explanatory diagram for explaining a grease life tester.

FIG. 11 is a graph showing the relationship between time and vibration acceleration in the ball bearings of Conventional Example 1, Conventional Example 2 and Conventional Example 4.

FIG. 12 is a graph showing the relationship between time and vibration acceleration in the ball bearing of the example.

[Explanation of symbols]

1 ... fused alumina abrasive grains (first abrasive grain) 2. Cubic boron nitride abrasive grains (second abrasive grain) 3 ... Binding agent for vitrified grindstone 4 ... Smooth surface 5 ... Groove-shaped recess 10 ... Ball bearing (rolling bearing) 11 ... Outer ring 12 ... Inner ring 13 ... rolling elements U ... Super finishing whetstone

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16C 33/58 F16C 33/58 33/66 33/66 Z F term (reference) 3C049 AA02 AA09 CA01 CB01 3C058 AA02 AA09 CA01 CB01 CB10 3C063 AA02 BB02 BB03 BB04 BB07 BB19 BC05 EE01 FF23 3J101 AA01 AA02 AA32 AA42 AA52 AA62 BA51 BA53 BA54 BA55 CA14 CA15 DA12 FA01 FA31 FA32 GA53

Claims (5)

[Claims] 1. A rolling bearing having a plurality of rolling elements arranged between an outer ring and an inner ring, wherein at least one of the raceways of the outer ring and the inner ring has a depth of 0.03 μm or more. A large number of groove-shaped recesses with a pitch of 5 to 20 μm or less and the roughness except the groove-shaped recesses is 0.005 in terms of center line average roughness.
A rolling bearing having a smooth surface of not more than μmRa. 2. The rolling bearing according to claim 1, wherein the plurality of groove-shaped recesses extend in the circumferential direction of the raceway surface and are arranged parallel to each other in the axial direction. 3. A method of manufacturing a rolling bearing, comprising a step of forming a groove-shaped recess on the raceway surface by subjecting at least one of the raceway surfaces of the outer race and the inner race to a grinding stone. As the grindstone, a superfinishing grindstone used in the final step of multi-stage superfinishing is used, and the raceway surface is processed by the superfinishing grindstone to give a depth of 0.03 μm or more and 0.08 μm or more.
A large number of groove-shaped recesses having a pitch of 5 to 20 μm or less, and the roughness except the groove-shaped recesses is 0.
A method of manufacturing a rolling bearing, comprising forming a smooth surface having a diameter of 005 μmRa or less. 4. The superfinishing grindstone, when the total weight of the grindstones of the grindstone is 100, 50 to 90% of the grindstone is one of silicon carbide abrasive grains, fused alumina abrasive grains and mixed abrasive grains thereof. One of them is used as a first abrasive grain, and the remaining 50 to 10% of the weight thereof is a cubic boron nitride abrasive grain having an average abrasive grain size of 0.5 to 2 times the average abrasive grain size of the first abrasive grain or 4. The rolling bearing according to claim 3, wherein the diamond abrasive grains are second abrasive grains, and the second abrasive grains and the first abrasive grains are mixed and bonded with a vitrified grinding stone binder. Manufacturing method. 5. The first abrasive having an average abrasive grain size of 0.6 to 2 μm.
5. The method for manufacturing a rolling bearing according to claim 4, wherein abrasive grains are mixed with the second abrasive grains having an average abrasive grain size of 1 to 4 [mu] m and bonded by the binder for vitrified grindstone.