JPH03172614A - Roller bearing - Google Patents

Abstract

PURPOSE:To lengthen the life of a track face and to reduce the manufacturing cost of a roller bearing by forming the surface of a roller rolling element into random minute rough faces, and restricting the roughness in axial and circumferential directions of the minute rough faces within a fixed range, and also finishing the track face of a bearing ring by grinding process. CONSTITUTION:The surface of the roller rolling element 3 of a roller bearing 1 is formed with minute rough faces in random directions. When the surface roughness of the minute rough face 3a is measured in axial and circumferential directions to indicate them through a parameter RMS, the ratio of the roughness RMS (L) in axial direction to that RMS (C) in circumferential direction is set to less than 1.0, and a parameter SK for indicating the strain degree of a distribution curve of the surface roughness is set to lower than 1.6 in both axial and circumferential directions. The oil film forming rate on a rolling face can be improved by restriction for meeting the above conditions. Thus the inner peripheral face of an outer ring 2, namely the track face of a roller bearing 1, is formed into a ground and finished face 11, and does not damage an opposite track face without superfinishing process. The manufacturing cost of the roller bearing can therefore be reduced, and its life can be lengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a roller bearing, and more particularly to a roller bearing that exhibits a long life even when the raceway surface of the raceway ring is finished by grinding.

[Conventional technology]

Rolling fatigue life is generally determined by the oil film parameter (8: h
/δ). In other words, oil film parameter 8 is small (
If the oil film parameter 8 increases, the life will become shorter.

Therefore, in order to extend rolling fatigue life, conventionally, in roller bearings, the roughness of the raceway surface of the raceway ring on which the rollers are transferred has been reduced by superfinishing.

[Problem to be solved by the invention]

By the way, in machining roller bearings, finishing the raceway surface of the bearing ring by superfinishing increases the number of machining steps,
There is a problem in that processing costs are high.

In addition, if the surface A of the roller rolling element and the raceway surface of the raceway ring are both superfinished, the formation of an oil film will be insufficient, and wear and peeling damage may occur on the surface of the rolling element and the raceway surface. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a roller bearing that can have a long service life even when the raceway surface of the bearing ring is finished before polishing, and can solve the problems caused by superfinishing.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention randomly forms countless independent minute concave depressions on the surface of the rolling element, thereby improving the surface area of the rolling element surface. When roughness is determined in the axial direction and circumferential direction and expressed as a parameter RMS, the axial surface roughness RMS (L) and the circumferential surface roughness RM
Ratio with S (C) RMS (L) /RM S (C)
becomes 1.0 or less, and the surface roughness parameter S
The K value is set to be -1.6 or less in both the axial direction and the circumferential direction, and the raceway surface of the raceway ring is a ground finished surface.

[Effect]

The surface of the roller rolling element is formed into a random micro-rough surface, and the finished surface roughness parameter RMS of this micro-rough surface is set in the axial direction (L
), determined in the circumferential direction (C), and the ratio RMS (L) / RM
Since S (C) is set to 1.0 or less, and the parameter SK value is set to -1.6 or less in both the axial and circumferential directions, the oil film formation rate on the rolling surface is improved and the raceway surface of the raceway is ground. Even if the machined surface remains, there will be no damage or wear due to beilling.
Long life can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Each of FIGS. 1-3 illustrates a different construction of a roller bearing.

The roller bearing 1 shown in FIG. 1 is a needle bearing in which needle roller rolling elements 3 incorporated into an outer ring 2 are held by a cage 4, and the roller rolling elements 3 support a mating shaft 5. .

The roller bearing 1a shown in FIG. 2 is a cylindrical roller bearing in which rolling elements 3 are interposed between an inner ring 6 and an outer ring 7, and the roller rolling elements 3 are held at a constant interval by a retainer 8.

The roller bearing 1b in FIG. 3 is a tapered roller bearing in which tapered roller rolling elements 3 are interposed between an inner ring 9 and an outer ring 10.

In each of the above-mentioned roller bearings 1.1a and 1b, the rolling elements 3 are formed with micro-rough surfaces 3a in random directions, and the micro-rough surfaces 3a have a surface roughness that is parallel to the axial direction of the rolling elements 3. When each of the circumferential directions is calculated and expressed by the parameter RMS, the ratio of the axial surface roughness RM S (L) and the circumferential direction surface roughness RM S (C) is RMS (L) /RM S (
C) is set to 1.0 or less, for example, 0.7 to 1.0, and the surface roughness parameter SK value is set to -1.6 or less in both the axial direction and the circumferential direction.

The surface treatment for obtaining the rough surface conditions of the transfer surface as described above can be performed by special barrel polishing to obtain the desired finished surface. FIG. 4 shows the cross-sectional roughness shape of the micro-rough surface 3a, and as shown in the figure, it is a special surface in which concave portions are formed in the plane and no convex portions protrude from the plane.

The parameter SK value refers to the degree of skewness (SKEWNESS) of the surface roughness distribution curve, and a symmetrical distribution such as a Gaussian distribution has an SK value of 0, but the parameter SK value can be changed in both the circumferential and axial directions. The setting value of −1.6 or less is a range in which the shape and distribution of surface recesses are favorable for oil film formation depending on processing conditions.

In addition, the raceway surface of the bearing ring in each roller bearing 1.1a, 1b, that is, the inner peripheral surface of the outer ring 2 in the needle bearing in FIG. 1, the inner ring 6 in the cylindrical roller bearing in FIG. 2, and the tapered roller bearing in FIG. The outer periphery of the outer ring 7.9 and the inner circumferential surface of the outer ring 7.10 have a ground surface 11.

Next, we will introduce a conventional roller bearing in which the surface of the inner ring and rolling elements are superfinished, and the surface of the inner ring is ground and finished, and the surface of the roller rolling elements is formed into a micro-rough surface with indentations in random directions. The results of a life test conducted using the roller bearing of the present invention will be explained.

The surface of the inner ring for super finishing is 0.4pmRmax.
Hereinafter, the micro roughness in random directions is 2 pmRmax, and the grinding finished surface of the inner ring is 2 to 41 INRsaχ.

As shown in Fig. 5, the needle bearing used in the life test had an outer diameter Dr = 33 m, an inner diameter dr -28 m, a diameter D-5 of the rolling elements 3, a length L = 13 m, and 14 rolling elements. This is a bearing with a cage using.

The test equipment used was a radial load tester 21 as shown schematically in Figure 6, with test bearings A mounted on both sides of the rotating shaft 22, and the test was conducted by applying rotation and load. It is.

Moreover, the test conditions are as follows.

Roller surface pressure 2.8GP.

Rotation speed 305Orpm Lubricant
Turbine Oil Figure 7 shows the results of a rolling element life test conducted on each test bearing under the above conditions.

As is clear from the above test results, the 10% failure probability was 130 hours for the conventional roller bearing, while the roller bearing of the present invention had a significantly longer life of 280 hours.

In general, there is a relationship between oil film parameters and oil film formation rate as shown in Figure 8, and it is said that the larger the oil film parameter is, the better from the perspective of life expectancy. It cannot be explained by just that.

6ml of oil film formation on the finished surface of the rolling element and peeling resistance were evaluated using a 2-cylindrical tester under zero and free rolling conditions using the above-described test bearing of the present invention and conventional test bearing. I conducted a test. Identification of oil film formation was performed using a direct current method.

Test conditions Maximum contact surface pressure: 227 kg4/am" Circumferential speed: 4.2 m/sec (2000 rpm) Lubricant: Turbine oil (10 cst under test conditions) Number of repeated loads: 4.8 x 10' (4 hr) The oil film formation rate in this test is: As shown in FIG. 9 and FIG. 1O, the oil film formation rate on the finished surface of the test bearing of the present invention was improved by about 20% at the start of operation compared to the conventional test bearing.

Furthermore, it was confirmed that an oil film was almost completely formed when the number of repeated loads was 1.2XlO'.

Furthermore, on the finished surface of conventional test bearings, many occurrences and progressions of peeling with a length of about 0.11 were observed;
No damage was observed on the finished surface of the test bearing of the present invention.

〔effect〕

As described above, according to the present invention, the surface of the rolling element is formed into a random micro-rough surface, and the roughness of the micro-rough surface in the axial direction and circumferential direction is suppressed within a certain range, and Since the raceway surface of the ring has a ground surface, it is effective in forming an oil film on the rolling surface, and even if the mating raceway surface is a ground surface, it can have a long life and prevent wear and peeling damage on the mating raceway surface. There is an effect that there is no.

In addition, since a long life can be obtained whether the raceway surface of the bearing ring is made with a ground finish or a long-life surface, super-finishing is no longer necessary when machining the bearing ring of a roller bearing, reducing machining man-hours and costs. reduction becomes possible.

[Brief explanation of the drawing]

Each of FIGS. 1 to 3 is a sectional view showing different structures of the roller bearing according to the present invention, FIG. 4 is an enlarged sectional view showing the cross-sectional roughness shape of the surface of the rolling element, and FIG. 5 is a life test. A cross-sectional view of the needle bearing used in the test, Figure 6 is a schematic diagram of the test equipment,
Figure 7 is a graph showing the results of the life test, Figure 8 is a relationship diagram showing oil film parameters and oil film formation rate, and Figures 9 and 10 are graphs showing oil film formation rates of conventional roller bearings and the present invention. be. 1.1a, 1b...Roller bearings, 2.7.10.
...Outer ring, 3...Roller rolling element, 3a...Micro-rough surface, 6.9...Inner ring, 11...
Grinding finished surface.

Claims (1)

[Claims] (1) In a roller bearing consisting of roller rolling elements and a bearing ring,
When a countless number of independent minute concave depressions are randomly formed on the surface of a roller rolling element, and the surface roughness of the rolling element surface is determined in both the axial direction and the circumferential direction and expressed by the parameter RMS, the axial The ratio RMS(L)/RMS(C) of the directional surface roughness RMS(L) and the circumferential surface roughness RMS(C) is 1.
0 or less, and the surface roughness parameter SK value is -1.6 or less in both the axial direction and the circumferential direction, and the raceway surface of the raceway ring is a ground finished surface. rolling roller bearing.