JP3019983B2 - Super finishing processing method for rolling bearings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to superfinishing of a rolling bearing.

[0002]

2. Description of the Related Art Rolling bearings are generally manufactured through processes such as forging, cutting, heat treatment, polishing, superfinishing, and assembly. Among these processes, super-finishing, which is the final finishing process for single parts, is one of the important machining processes that determine the functions of the product. This is an important step.

[0003] Therefore, a lot of original manufacturing know-how of each bearing maker is included in this processing step. In particular, the type of grindstone used (grain size, hardness, type of binder, etc.), the processing conditions (number of rotations of the work, the number of rocking of the grindstone, pressing force, etc.)
Two-stage processing divided into stages, or two-axis processing that repeatedly performs processing using different types and grain sizes of grinding wheels, etc.
One-axis two-stage processing (a processing method in which processing conditions such as the number of revolutions, pressing force, and oscillation number are changed in the middle with the same grindstone), and two-axis four-step processing (a method in which both the type and processing conditions of the whetstone are changed in the middle) Various processing methods are performed.

[0004] In super-finishing, the work rotates and the grindstone swings in the axial direction while being pressed against the work, so that the trajectories of the grindstone drawn on the finished surface intersect. Therefore,
Grinding marks due to the abrasive grains of the grindstone, that is, the grinding stitches intersect.
Regarding the super finish processing of the raceway surface on which the rolling elements roll, conventionally, it is preferable to increase the processing efficiency by reducing the crossing angle of the grinding line by the grindstone as much as possible and to reduce the surface roughness of the raceway surface as much as possible. It has been considered. However, it has been found that there is room for improvement from the viewpoint of the acoustic characteristics of the bearing.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for superfinishing a raceway surface which is optimal for improving the sound of a rolling bearing.

[0006]

Means for Solving the Problems The present invention has solved the problem by making the crossing angle of the grinding line by a grindstone as small as possible in super finishing of the raceway surface of a rolling bearing.

In super finishing of a raceway surface of a rolling bearing in which machining is performed in two stages or in two or more types of machining conditions or types of grindstones, an intersection angle of a grindstone by a grindstone in an initial rough machining is set to 0. .3 degrees or less (claim 1). In addition, the above-mentioned intersection angle is set to 1. when processing is performed with a relatively hard finishing wheel such as a CBN wheel in the final stage.
0 degrees or less (claim 2).

In super finishing of a raceway surface of a rolling bearing in which processing is performed in a single process without changing processing conditions or the type of a grindstone, the crossing angle of a grinding line with a grindstone is 0.3 degrees. The following is defined (claim 3).

[0009]

In the super-finishing of a rolling bearing, as shown in FIG. 1 (A), a grindstone 3 is swung at right angles to the rotating direction while pressing a grindstone 3 against a rotating work, that is, a raceway surface 2 of an inner ring 1 in this case. Therefore, as shown in FIG. 1B, the grinding lines by the grindstone cross each other. The intersection angle 2θ of the grinding line is
It becomes smaller as the number of swings of the grindstone becomes relatively lower than the number of rotations of the work. Table 1 shows the work diameter (bottom diameter of raceway groove) 1
In the case of 6.444 mm, the number of work rotations 5000 rpm, and the swing amplitude 1.73 mm, the swing numbers 100, 400, and 70
An example of the intersection angle at 0 cpm is shown.

[Table 1]

[0010] By reducing the intersection angle 2θ of the grinding, the unevenness, width and length of the intersection are reduced, and the generation of bulges and burr-like projections along the grinding is minimized. As the raceway surface after processing, a finished surface having uniform properties, that is, uniform surface roughness, ground lines, etc., and good flatness can be obtained. Further, generation of dust at the time of use of the bearing due to falling off of burrs and the like can be suppressed.

FIG. 2 is a schematic view of a grinding line (grinding streak). FIG. 2A shows a bulge 6 around the grinding line 5.
(B) shows a burr-like chip 8. 4 is abrasive grains,
7 denotes a chip, and 9 denotes a contact mark with a single abrasive. As the angle θ formed by the grinding line is larger, the bulge 6 as shown in FIG. 2A is larger, and furthermore, burrs like chips 8 as shown in FIG. Conversely, the smaller the angle θ is, the smaller the swelling is, and the burr-like chips 8 are less likely to be generated. In addition, since the grinding line intersects at a large angle θ, the unevenness in the circumferential direction becomes larger than that at a small angle θ. The worse the sharpness of the abrasive grains, the higher the swelling, and the higher the degree of burr-like chip generation.

[0012]

Embodiments of the present invention will be described below.
[Embodiment 1] The inner and outer rings of the ball bearing # 6201 model number after the completion of the grinding process are respectively put into a superfinishing machine.
Roughing is performed using a CBN grinding wheel (cubic boron nitride grinding wheel, particle size # 4000). The processing conditions are as follows. Spindle rotation speed 5000 rpm Grinding stone swing number 100 cpm Grinding stone pressurization 3.0 kgf Processing time 25 sec Removal allowance Approximately 6 μm The intersection angle formed by the grinding line under the above conditions is 0.24 degrees.
Next, as a finishing process, a polishing grindstone based on chromium oxide or white alumina (grain size # 6000 to 80
(Approximately 00) and processing is performed under optimum processing conditions of about 1 μm.

In such a rough or finished two-axis or two-stage machining system, the effect of the surface finish on the acoustic quality of the bearing is as follows. Combined with the degree and smallness,
It was found that it was mainly affected by the surface finish during roughing.

FIG. 3 shows that the number of oscillations of the grindstone at the time of rough machining is 100 c.
Experimental results obtained by performing acoustic comparisons of test samples when pm, 400 cpm, and 700 cpm were used, and three types of grindstones were used in the finishing process, and the other conditions were the same.

It has been found that those having a low number of oscillations of the grindstone at the time of rough machining, in other words, those having a small crossing angle formed by the grinding line show the lowest noise value. However, as shown in the figure, the finishing was also performed using a CBN grinding wheel (B in the figure, grain size # 800).
In the case of using (0), the number of swings of the grindstone at the time of roughing is 400 c.
pm (crossing angle: 0.96) also showed a low noise value. This fact indicates that, as with CBN, a grindstone having a hardness higher than that of the other grindstones described above (knoop hardness of CBN of about 5).
000, the Knoop hardness of white alumina is about 2,000), which means that the influence of the surface due to the roughing is considerably corrected at the time of finishing, and this is inferred from FIG. Is done.

FIGS. 4 (A) to 4 (C) show a roughness curve in the axial direction of the # 6201 inner ring, and FIG. 4 (A) shows a coarse oscillation number of 100 cpm.
4B and 4C show the results obtained by applying a finishing super using the following various kinds of grinding stones to those having a coarse superposition of 400 and 700 cpm, respectively. Is multiplied by The processing conditions for the finish super are all the same. Chromium oxide-based grindstone CBN-based grindstone White alumina-based and silicon-carbide-based grindstone The removal superfluous is removed so that the 100-200 μm valley is eliminated by the finishing superficial, but the feature of only the coarse superficial is the finishing superficial. You can see the remnants later.
This indicates that the processing with the coarse super also affects the finish super.

FIGS. 5A to 5C show crude products # 6201.
3 shows an inner ring axial direction roughness curve. Here, if the expressions “valley” and “hill” are used as shown in FIG.
The one with 00 cpm has a relatively shallow valley (about 100 nm), and the hills have relatively few irregularities. In addition, the height of adjacent hills is also uniform. Next, when the whetstone rocking number is 400 cpm, the valley becomes deep (about 200 nm) and the unevenness of the hill becomes large. In addition, there are steps on the height of adjacent hills. And the whetstone rocking number is 700 cpm
, The depth of the valley is the same as that of the above-mentioned 400 cpm, but a wide valley can be seen (width 10 μm).
m), the unevenness of the hills becomes even larger. The adjacent hills have large steps, and the hills themselves are also inclined. Table 2 shows the measured values of the # 6201 inner ring axial direction roughness.

[Table 2]

[Embodiment 2] Ball bearing # after completion of the grinding process
The inner and outer rings of model No. 6201 are respectively put into a superfinishing machine, and superfinishing is performed using a CBN grinding wheel (grain size # 4000) or a relatively sharp grinding wheel. The processing conditions are as follows. Spindle rotation speed 5000 rpm Grinding stone swing number 100 cpm Grinding stone pressurization 3.0 kgf Processing time 25 sec Removal allowance Approximately 6 μm The intersection angle formed by the grinding line under the above conditions is 0.24 degrees.
Usually, there are not many examples of such a so-called one-shaft or one-step machining system, but there have been demands for satisfying the sound quality required as a sound quality characteristic of the bearing or as a bearing for low noise. Applies to cases.

FIG. 6 shows that the number of swings of the grindstone at the time of superfinishing is 1
The experimental results obtained by comparing the noise and acoustic values of the test samples when 00 cpm, 400 cpm, and 700 cpm and other conditions are the same are shown. As is clear from the figure,
It can be seen that those having a low number of swings at the time of processing, in other words, those having a small intersection angle formed by the grinding line show the lowest noise value.

A deep groove ball bearing # 6201 was subjected to an acoustic quality improvement test by improving raceway surface characteristics, and the outline thereof will be described below. First, Tables 3 to 6 show a list of processing conditions of the samples.

[Table 3]

[Table 4]

[Table 5]

[Table 6] Here, the lot abbreviations in Tables 4 and 5 will be described. As can be seen from Table 3, the numerals 1, 4, and 7 represent the coarse swing numbers of 100, 400, and 700 cpm, respectively. Is crude only, T is TM6
000 whetstone finish product, P is PBN8000I whetstone finish product,
G represents a DG6000 grinding stone finish. In addition, AP and SP are low swing products (one shaft 2
(Step, 100/50 cpm) are a coarse super finished product and a finished super finished product, and AB and SB are a coarse super finished product and a finished super finished product, respectively. Table 6 illustrates the grindstones used.

Next, FIGS. 7 to 11 show enlarged photographs of the inner ring raceway surface by a scanning electron microscope. From FIGS. 7 to 9, it can be seen that the crossing angle of the grinding line increases as the number of swings increases to 100, 400, and 700 cpm only with coarseness. Further, from FIG. 10, when the swing number is 700 cpm with a large intersection angle, burr-like projections are observed along the grinding line. These projections may remain even after completion of the finishing superposition, and are considered to have adversely affected the sound.

FIGS. 12 and 13 show graphs comparing sound. FIG. 12 shows the noise level, and FIG.
Indicates Anderon HB (high band).

Referring to the graph comparing the noise levels in FIG. 12, the exception is that in the group of P, the one with the coarse oscillating number of 400 cpm shows a low value in the group of T, P, G and A. It can be seen that the lower the coarse oscillation number, the lower the noise level. In addition, the crude only product “1A” is not inferior to the finished super finished product, and has an average of 31 d.
It shows a value of about BA. In addition, low swing products "A
For P "and" SP ", there was no effect obtained by reducing the number of swings to 100 cpm or less. "AB",
“SB” is shown for comparison.

Finally, for reference, FIGS. 14 and 15 show graphs of the axial roughness Ra value of the inner and outer raceway surfaces. As can be seen, only crude products ("AP", "1A", "4
A "," 7A ", and" AB ") have higher Ra values than finished super finished products.

[0025]

As described above, the present invention reduces the number of oscillations of the grindstone during superfinishing to minimize the crossing angle of the grindstone by the grindstone, thereby making it possible to perform rough machining only. Even after finishing, the acoustic value of the bearing is considerably improved. In other words, by relatively lowering the swing of the grindstone during the roughing with respect to the number of rotations of the work and suppressing the intersection angle of the grinding line by the abrasive grains, the unevenness of the intersection, the width, and the length are reduced. As a result, it is possible to minimize the occurrence of bulges and burr-like projections along the grinding line, and as a raceway surface after finishing processing, uniform properties, that is, uniform and uniform surface roughness, grinding marks, etc. A good finished surface can be obtained. Further, generation of dust at the time of use of the bearing due to falling off of burrs and the like can be suppressed. Therefore, according to the present invention, a rolling bearing having good acoustic quality can be manufactured.

[Brief description of the drawings]

FIG. 1A is a schematic diagram illustrating a super-finishing process of a bearing inner ring, and FIG. 1B is a schematic diagram illustrating an intersection angle of a grinding line by a grindstone.

FIG. 2 is a schematic view of a grinding line (grinding streak), where (A) shows a bulge and (B) shows burr-like chips.

FIG. 3 is a graph showing a relationship between the number of swings of a grindstone and a noise value according to the first embodiment.

4 is a # 6201 inner ring axial direction roughness curve diagram. FIG.

FIG. 5 is an inner ring axial direction roughness curve diagram of a rough only product # 6201.

FIG. 6 is a graph showing a relationship between a whetstone rocking number and a noise value according to the second embodiment.

FIG. 7 is a scanning electron micrograph showing the metal structure of the inner ring raceway surface in the case of a coarse only rocking number of 100 cpm.

FIG. 8 is a scanning electron micrograph showing the metal structure of the inner ring raceway surface in the case of a coarse only rocking number of 400 cpm.

FIG. 9 is a scanning electron micrograph showing the metal structure of the inner ring raceway surface when the coarse only rocking number is 700 cpm.

FIG. 10 is a scanning electron micrograph showing the metal structure of the inner raceway surface, and is a partially enlarged view of FIG. 9;

11 is a scanning electron micrograph showing the metal structure of the inner raceway surface, which is obtained by converting the vertical and horizontal directions in FIG.

FIG. 12 is a graph showing a result of comparing sound with a noise level.

FIG. 13 is a graph showing a result of comparing sounds with Anderon HB (high band).

FIG. 14 is a graph of the roughness Ra value in the axial direction of the outer raceway surface.

FIG. 15 is a graph of the roughness Ra value in the axial direction of the inner raceway surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner ring 2 Raceway surface 3 Grindstone 4 Abrasive grain 5 Grinding line (grinding streak) 6 Rise 7 Chip 8 Burr-shaped chip 9 Contact mark with single grindstone grain

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B24B 35/00 F16C 33/64

Claims (3)

(57) [Claims] 1. In super finishing of a raceway surface of a rolling bearing in which processing is performed in two stages or two or more types of processing conditions or types of grindstones, an intersection angle of a grindstone by an initial rough grinding wheel is determined. A super-finishing method for rolling bearings, characterized in that the angle is not more than 0.3 degrees. 2. The method according to claim 1, wherein the crossing angle of the grinding line by the grindstone in the initial rough machining is set to 1.0 ° or less, and the machining is performed by a relatively hard finishing grindstone such as a CBN grindstone in the final stage. 2. The super-finishing method of the rolling bearing according to 1. 3. In a super-finishing process of a raceway surface of a rolling bearing in which machining is performed in a single process without changing machining conditions or the type of a grinding wheel, the crossing angle of a grinding line with a grinding wheel is 0.3. A super-finishing method for rolling bearings, characterized in that the degree is not more than a degree.