JPH03189415A - Ball bearing for tension pulley or the like - Google Patents

Abstract

PURPOSE:To offer an advantage for forming an oil film on the surface of a rolling element and prevent the occurrence of an abnormal sound in a cold condition by randomly forming an infinite number of fine recesses on the surface of the rolling element and keeping the surface roughness parameter SK value thereof at -1 or less and the average area of the fine recesses at 80mum<2> or less. CONSTITUTION:A rolling element 14 built into a ball bearing 11, is so formed as to have a fine rough surface 14 with randomly formed fine recesses. The aforesaid rough surface 4a is set to a surface roughness parameter SK value of -1 or less, and the average area of fine recesses is set to 80mum<2> or less to reduce the deterioration of the sound level of the ball bearing 11. The section of the rough surface 14a is so formed as to have a recess on a flat surface without any projection from the flat surface. In the ball bearing 11 formed in accordance with the aforesaid condition, the fine roughness acts as a lubricant stagnation position and as a bucket for replenishing a contact part with the lubricant. Consequently, a stable oil film can be obtained, thereby preventing the occurrence of an abnormal sound in a cold condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ball bearing used in a tension pulley or the like, and more particularly to a ball bearing that can prevent abnormal noise phenomena that occur in cold weather.

[Conventional technology]

For example, as shown in FIGS. 8 and 9, a tension pulley 1 for an engine timing belt in an automobile is
Swing shaft 3 using single row deep groove ball bearing 2 or double row ball bearing
The belt 5 is supported so as to be rotatable, and an auto-tensioner 4 applies a rotational force in the direction of tensioning the belt 5.

The ball bearing 2 is designed to reduce angular runout due to mechanical requirements, but is otherwise the same as a normal ball bearing, and uses grease lubrication.

In particular, in the case of the single-row deep groove ball bearing 2, although the outer ring 2a is pressed by the belt 5, there is a large degree of freedom in the moment load direction and the axial direction.

By the way, in cold weather, the supply of lubricant to the bearing raceway becomes unstable, and the outer ring automatically vibrates due to stick-slip due to fluctuations in the rolling friction coefficient, resulting in what is commonly called abnormal cold noise.

Is this abnormal sound caused by the ball bearing, 1rfI? In addition to fI agents,
It is caused by a combination of many factors such as engine natural vibration, rotational vibration, belt tension, etc., but as mentioned earlier, in ball bearings in particular, it is largely caused by stain slip due to minute changes in the rolling friction coefficient of the rolling contact part. That's right.

Fluctuations in the rolling friction coefficient are due to fluctuations in the lubrication state of the rolling contact area, and if a stable lubrication state and oil film are always maintained, the friction coefficient will fluctuate little.

[Problem to be solved by the invention]

However, in conventional ball bearings, the surfaces of the rolling elements are finished with a super-finished surface, which results in poor oil retention and poor oil film formation ability, making the supply of lubricant to the contact parts unstable, such as in cold weather. When this happens, there is a problem in that abnormal noise occurs when cold, as described above.

Therefore, the object of this invention is to create a tension pulley that can always provide a stable lubrication state and oil film on the rolling contact parts even in cold weather, reduce fluctuations in the rolling friction coefficient, and prevent abnormal noises when cold. The aim is to promote the production of ball bearings.

[Means to solve the problem]

In order to solve the above problem, this generation randomly forms countless independent minute concave depressions on the surface of the rolling element, and the parameter SK value of the surface roughness of the rolling element surface is -11! is -1.0 or less, and the average area of minute depressions is 8
This configuration adopts a configuration in which the value is 0μ■2 or less.

[Effect]

A countless number of independent minute depressions are randomly formed on the surface of the rolling element, and the surface roughness of the rolling element is adjusted so that the parameter SK value is -1.
, 0 or less, and the average area of the minute depressions is 80 μml or less, so the minute depressions act as a bucket for replenishing the l'I'I lubricant pool and contact area,
A stable oil film can be formed at the contact area with the rolling element, and even when the supply of lubricant to the contact area tends to be unstable, such as in cold weather, the presence of the lubricant can prevent abnormal noise from occurring.

(Embodiments) Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 7 of the accompanying drawings.

As shown in FIG. 1, a ball bearing 11 used in a tension pulley for a timing held in an automobile engine has a structure in which a large number of steel ball rolling elements 14 are incorporated between an outer ring 12 and an inner ring 13.

The surface of the steel ball rolling element 14 is formed into a micro-rough surface 14a in which countless independent micro-gate-shaped depressions are randomly provided, and the micro-rough surface 14a has a surface roughness parameter SK value of - 1.0 or less, the average area of the minute depressions is 80 μIIz or less to reduce the deterioration of the acoustic level of the ball bearing, the average equivalent circular diameter is 10 μm or less, and the area ratio of the minute depressions is 10 to 40%.

The surface treatment for obtaining the rough surface condition of the rolling surface as described above can be performed by special barrel polishing to obtain the desired finished surface. FIG. 2 shows the cross-sectional roughness shape of the micro-rough surface 14a, 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 skewness (SKEWNESS) of the surface roughness distribution curve.A symmetric distribution such as a Gaussian distribution has an SK value of 0, but the parameter SK value is -
The set value of 1.0 or less is a range in which the shape and distribution of the surface recesses are favorable for oil film formation depending on the processing conditions.

The raceway surfaces of the outer ring 12 and inner ring 13 in the ball bearing 11 are preferably superfinished, but may be ground.

Next, we will introduce a conventional ball bearing in which the surfaces of the inner and outer rings and the surface of the steel ball rolling elements are super-finished, and the surfaces of the inner and outer rings are super-finished and the surface of the steel ball rolling elements has indentations in random directions. established,
The results of a life test conducted using the bearing of the present invention formed on a micro-n-plane will be explained.

The surfaces of the super-finished inner and outer rings and steel ball rolling elements are 0°2 μm.
Below Reaax, micro bill face in random direction is 2μw
+Rnax.

The test equipment used was a radial load tester 21 as schematically shown in FIG. 3, in which the test bearing A was attached to the rotating shaft 22 and a load was applied to perform the test.

Moreover, the test conditions are as follows.

Radial load: 500 gP Rotation speed: 350 rpm Lubricant Turbine oil Figure 4 shows the results of the rolling element life test conducted on each test bearing under the above conditions.

As is clear from the above test results, the 10% probability of failure was 45 hours for conventional ball bearings, while the ball bearing of the present invention had a significantly longer life of 125 hours.

In general, there is a relationship between the oil film parameter and the oil film formation rate as shown in Figure 5, 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.

Confirmation of oil film formation on the finished surface of the steel ball rolling element and peeling resistance were conducted using a two-cylindrical testing machine under free rolling conditions with the test bearing steel balls of the present invention and the conventional test bearing steel balls. Accelerated beer testing was conducted using cylindrical specimens with the same finished surface. The status of oil film formation was confirmed using a direct current method.

Test conditions Maximum contact pressure: 227Kgf/■2 Circumferential speed: 4, 2 m/sec
(2000 rpm) Lubricant Turbine oil (10 cst under test conditions) 4,8 x 10' (4 hr) Number of repeated loads The oil film formation rate in this test is as shown in Figures 6 and 7, and the present invention The oil film formation rate on the finished surface of the test bearing was improved by about 20% at the start of operation compared to the conventional test bearing.

Furthermore, it was confirmed that the finished surface specimen of the present invention almost completely formed an oil film when the number of repeated loads was 1.2XIO'.

Furthermore, on the finished surface of conventional test bearings, many occurrences and progress of bealling with a length of about 0.1 stroke were observed.
No damage was observed in the two aspects of the work of the present invention.

As mentioned above, compared to the normal rolling bearing ring with a super-finished surface and steel ball rolling elements, the ball bearing of this invention has a super-finished bearing ring and micro-indentations in the steel ball rolling elements. The depressions act as a place for lubricant to accumulate and supply to the contact parts, making it possible to obtain a stable oil film thickness, even when the supply of lubricant to the contact parts is unstable, such as in cold weather. , sufficient lubricant exists or can be supplied to form an oil film, and abnormal noises can be prevented from occurring when cold.

〔effect〕

According to this invention, the surface of the rolling elements in a ball bearing is formed into a random micro-rough surface, and the roughness of this micro-rough surface is kept within a certain range, thereby reducing the oil film on the rolling surface. This is advantageous for formation, provides a stable supply of lubricant to the contact parts even in cold weather, and reduces fluctuations in the coefficient of rolling friction.
It is possible to prevent abnormal cold noise from occurring in ball bearings such as tension pulleys.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a ball bearing according to the present invention, Fig. 2 is an enlarged sectional view showing the surface roughness shape of a steel ball rolling element, Fig. 3 is a schematic diagram of a life test device, and Fig. 4 is a life test. 5 is a relationship diagram showing the oil film parameters and oil film formation rate. FIGS. 6 and 7 are graphs showing the oil film formation rate of conventional ball bearings and the present invention. FIG. 8 is a graph showing the oil film formation rate of ball bearings. FIG. 9 is a front view of the same, and FIG. 9 is a longitudinal sectional side view of the same. 11...Ball bearing, 12...Outer ring, 13...Inner ring, 14...
・Rolling element, 14a...Micro-rough surface. 1) Figure 1 Figure 3 Figure 2 Figure 4 Hours

Claims (1)

[Claims] (1) Countless independent minute concave-shaped depressions are randomly formed on the surface of the rolling element, the surface roughness parameter SK value of the rolling element surface is -1.0 or less, and the average area of the minute depressions is 80 μm^ Ball bearings such as tension pulleys designed to be 2 or less.