JPS61167715A - Rolling construction of steel ball - Google Patents

Abstract

PURPOSE:To prevent the generation of exfoliation of a surface layer from a steel ball and increase its life, by forming surface roughness of the steel ball, which rolls by grease lubrication, approaching the surface roughness of a corresponding rolling surface. CONSTITUTION:A ball bearing 1 provides on a rolling surface of its inner ring 3 and outer ring 4 a steel ball 2 rolled being lubricated by grease. And surface roughness of the steel ball 2 is formed approaching the surface roughness of a corresponding rolling surface. In this way, the ball bearing, in which an oil film layer provided between a surface of the steel ball 2 and a contact surface of the inner and outer ring 3, 4 can be surely formed improving lubrication between the steel ball 2 and the inner and outer ring 3, 4 and suppressing a temperature rise of the steel ball 2, eliminates the generation of exfoliation of a surface layer enabling a life of the steel ball 2 to be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steel ball rolling structure, and particularly to a rolling structure in which the steel balls exhibit a long life under grease lubrication conditions.

[Conventional technology]

The conditions under which bearings and pole joints using steel balls are used have become increasingly diverse in recent years, such as higher temperatures, higher loads, and higher speeds. The temperature of bearings and joints increases due to internal factors of the bearings and joints, as well as temperature increases due to external factors such as the atmosphere. Especially in grease lubrication, the grease confines the heat dissipation from the steel balls, so the temperature of the bearings and joints increases. Compared to the inner and outer rings, there is less heat dissipation and the temperature rise is larger.

As mentioned above, when the temperature of the steel ball increases significantly during nine high-speed rotations, the surface layer of the steel ball is more likely to peel off than the inner and outer rings, shortening the life of the bearing and joint.

Table 1 shows an example of the life test results of the ball bearing 1 with grease lubrication shown in Fig. 1. When the area around the bearing is not air-cooled during the test, the bearing temperature is 100% as shown in sample /rL1.
℃, and peeling occurred on the surface layer of the steel ball 2.

On the other hand, in sample muds 2 to 4 that were air-cooled, the bearing temperature was around 70°C, and the short-time peeling of the steel balls 2 was suppressed, increasing the bearing life.

If we measure the X-ray half-width of the inner ring raceway and the surface of steel ball 2 after the test, we can see that the half-width of steel ball 2 is lower than that of inner ring 3 when it is not air-cooled compared to when it is air-cooled. are doing.

This X-ray half-width is thought to decrease as the temperature of the rolling surface increases, and a large decrease in the half-width of the steel ball 2 means that the temperature rise of the steel ball 2 is large.

Next, Table 2 shows the durability test results for ball joints lubricated with grease, and in the case of the joints of specimens A1 to A3, the surface layer of the steel balls easily peeled off from the inner and outer rings.

Although this test condition is a special use condition of low load and high speed, the temperature rise of the entire joint is large compared to conventional tests. The surface half-width measurement results of steel balls are shown in the same table.
In the case of specimen black 1, which is a conventional product, the reduction in half width of the steel ball is clearly large.

Table 2 Ball joint durability test results 4 # belt Equivalent to the present invention Hard Ra unit In addition, in the life test of ball bearings using oil lubrication, which is normally performed, the probability that the surface layer of the steel ball will peel off is equal to the probability that the inner and outer rings will separate. On the other hand, it is less than ξ, so the life of the steel ball is hardly a problem. In this case, as shown in Table 3, it can be said from the half width measurement results that in the case of oil lubrication, the temperature rise of the steel ball is smaller than that of the inner ring. In other words, it is estimated that heat dissipation from the rolling elements is greater with oil lubrication than with grease lubrication. Although the difference in temperature rise is small, it has a large effect on the life of the steel ball.

Note that this difference in temperature rise is so small that it cannot be detected by conventional hardness measurement or microstructure observation, and
This can only be clarified by line half-width measurements.As mentioned above, in ball bearings and constant velocity ball joints using grease lubrication, the short life of steel balls is largely related to temperature rise, and In order to extend the life of the steel ball, it is thought that this can be achieved by improving the lubrication conditions and suppressing the temperature rise of the steel ball.

Generally, the lubrication state is determined by the surface roughness of the object in contact with σ1. σ
2 and oil film thickness. It is thought that it can be organized using oil film parameters.

There is a relationship between the oil film parameter, 1 = h0/r town - (1) and life as shown in Figure 4.

That is, if A is 3 or more, lubrication is in an ideal state and the life does not increase any further. Furthermore, if 'A is 2 or less, the life can vary greatly depending on the value of A.

However, even if the lubrication conditions are predicted to be good in advance, it is impossible to measure the oil film thickness during the test, and the temperature at the contact point of the placed object cannot be accurately evaluated. The problem is that it cannot be calculated, and with grease lubrication, which requires little heat dissipation from the steel ball, unexpected heat generation occurs at the contact point, and the decrease in oil film thickness causes a shorter life than expected. It is considered that

Furthermore, the hardness of steel balls decreases as the temperature rises, and this decrease in hardness also causes a short life. Note that the hardness decrease here refers to the hardness during the test, and there is no hardness decrease when the steel ball temperature reaches room temperature after the test is completed.

For example, as can be seen by measuring the half-width, this temperature rise occurs only within the very surface layer (10 μm) of the steel ball, and can be countered by improving the lubrication performance and suppressing the temperature rise. becomes.

[Problem that the invention seeks to solve]

By the way, the lifespan of both objects that come into rolling contact with each other is usually the longest when their mutual surface roughness is small.

When there is a difference in surface roughness between the two objects, it is said that the object with the smaller surface roughness will have a shorter lifespan.

Therefore, conventionally, in order to improve the lubricity of the two objects that come into contact with each other during rolling and extend their life, the roughness of the rolling surfaces of the inner and outer rings has been made close to that of a steel ball, which has a small surface roughness.

That is, steel balls with small surface roughness can be manufactured due to processing technology, and therefore the rolling surfaces of the inner and outer rings are made close to the surface roughness of the steel balls.

However, reducing the raceway surface roughness of the inner and outer rings to approximate the surface roughness of a steel ball significantly increases processing costs.

In addition, as mentioned above, especially in the case of high-speed rotation, in ball bearings and ball joints where the heat dissipation of the steel balls is low due to grease lubrication, a temperature rise occurs in the steel balls, causing the current surface of the inner and outer ring rolling surfaces to rise. There is a problem in that roughness shortens the life of the steel ball.

This invention was made to solve the above-mentioned problems, and by improving the lubricity of the rolling surfaces and suppressing the temperature rise of the steel balls, it is possible to improve the lubricity of the rolling surfaces and suppress the temperature rise of the steel balls. The purpose is to provide a steel ball rolling structure that can extend the life of the steel ball.

[Means for solving problems]

In order to solve the above-mentioned problems, this invention consists of a rolling surface and a steel ball that is lubricated with grease and rotates.
The surface roughness of the steel ball is made close to that of the mating rolling surface.

[Effect]
q Steel balls are interposed between the rolling surfaces of the inner and outer rings and are lubricated with grease.

The surface roughness of the steel ball is roughened so that it approaches that of the rolling surfaces of the inner and outer rings, and this roughening has an oil-retaining effect on the surface of the steel ball and the rolling surfaces of the inner and outer rings This function forms an oil film between the rolling surfaces to improve lubricity, suppress the temperature rise of the steel ball, and increase its lifespan.

〔Example〕

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

The steel ball of this invention is used in the ball bearing and constant velocity ball joint shown in FIG. 1, and is lubricated with grease sealed between the inner and outer rings 3 and 4.

The surface roughness of the above-mentioned steel balls approaches the roughness of the rolling surfaces of the inner and outer rings, and is roughened to a level beyond conventional wisdom.

The specific surface roughness of the steel ball differs depending on the conditions of the inner and outer rings, that is, in the case of a ball bearing and a constant velocity ball joint, but based on the experimental results, the lower limit value can be set as follows in any case. be done.

0,05 μmRa (a, (a2 σ1 = Surface roughness of the steel ball μm σ2 = Roughness of the inner and outer rolling surfaces μm The surface roughness σ of the suitable steel ball is o, o o sμmRa, and the What is the specific rolling surface roughness?

General bearing: a, = Q, Q 5 , umRa (0
, 2μmRm@x) Super large ball bearing: 62 #0.
75.1mR21 (3μmRmax) Constant velocity ball joy 71-: Ra! Q, 75 (3μmRmax
) where Ra is the centerline average roughness and Rmax is the maximum height.

It is clear that the parameter A decreases, which is expected to be disadvantageous to the lubrication state, but σ2 is gradual. Further, the increase until σ1 becomes equal to σ2 is about 70% of when σ1=O.

Figure 3 shows the decrease in half-width of an object with a surface roughness of σ1 after the transfer test when σ1 is varied with σ constant, but within the experimental range σ, = Q, 4 pm.
It can be seen that as σ1 increases, the half width decrease decreases until σ1 increases. This phenomenon is considered to be a result of the increased retention of lubricant on the contact surface as the surface roughness increases. From Fig. 2, it is expected that the oil film parameter A will decrease with an increase in σ1, but the oil film thickness ho (see equation (1)) will increase due to the oil retention effect of the lubricating oil due to this increase in surface roughness. It is estimated that A is increased. As mentioned above, if σ is made equal to σ, the oil film parameter will increase as a result. As can be seen from FIG. 2, a large decrease in the surface roughness a2 of the mating rolling surface is small, so it is thought that the lubricant retention effect due to the increase in σ1 has a large influence on the oil film parameters.

In other words, it can be said that the present invention is more effective as the roughness of the mating rolling surface increases.

Of course, it is expected that the absolute value of the half-width reduction due to a change in σ1 in Figure 3 will change depending on the test conditions such as the type of lubricant, the amount of lubricant, and the rotational speed, but the behavior shows almost the same tendency. it is conceivable that. Under ideal lubrication conditions (A > 3 in Figure 4) for the bearing to exhibit its original life performance value, it is thought that the reduction in rolling surface half width after a certain time test is within 0.3. According to this standard, the value of σ1 from Figure 3 is 0.2 μmRmax (Q, Q 5
μmRa ) or more is required.

The steel ball rolling structure of the present invention has the above-mentioned configuration, and in a constant velocity ball joint, the surface roughness of the steel balls incorporated between the inner and outer rings is made close to the rolling motion roughness of the inner and outer rings, and the joint is was tested under the same conditions as in Table 2.

In Table 2, specimens &, 4 and 5 were the examples, and the life of the steel balls was significantly increased. The measurement results of the half-width of the steel ball surface are also shown in the same table, and it can be seen that the greater the surface roughness of the steel ball, the smaller the half-width, which clearly improves the lubrication state.

〔effect〕

As described above, according to the present invention, the steel ball is composed of a rolling surface and a steel ball that is lubricated with grease and rolls on the rolling surface, and the surface roughness of the steel ball is made close to that of the mating rolling surface. It is possible to reliably form an oil film layer between the contact surfaces of the surface and the inner and outer rings, improving the lubricity between the steel balls and the inner and outer rings, and by suppressing the temperature rise of the steel balls, the system eliminates the occurrence of peeling of the surface layer. , it is possible to achieve a longer service life of the steel ball.

It also prevents the hardness of the steel balls from decreasing due to temperature rise, which makes it possible to extend the life of the steel balls.Furthermore, the life of the steel balls can be made equal to the lifespan of the inner and outer rings, which can be used for ball bearings and constant velocity balls. This can contribute to the long life of the joint.

[Brief explanation of the drawings] Figure 1 is a cross-sectional view of the ball bearing, Figure 2 is the change in coefficients related to the surface roughness of the steel ball and oil film parameters, and Figure 3 is the surface roughness and rolling behavior after the test. Graph showing the relationship between the half width of the surface, 4th
The figure is a graph showing the relationship between oil film parameters and service life. 1 is a ball bearing, 2 is a steel ball, 3 is an inner ring, and 4 is an outer ring. Figure 1 Figure 3 Figure 2 Figure 6, (Rmax) Figure 4

Claims (1)

[Claims] A steel ball rolling structure consisting of a rolling surface and a steel ball that is lubricated with grease and rolling, and is characterized in that the surface roughness of the steel ball is close to that of the mating rolling surface.