JPH03160325A - Method for monitoring lubricating condition of rolling bearing - Google Patents

Abstract

PURPOSE:To easily monitor a lubricating condition even with respect to the bearing incorporated in machine equipment even when an oil film is thick by monitoring the lubricating state of a rolling bearing on the basis of the amplitude of the inherent vibration generated from the rolling bearing during rotation. CONSTITUTION:At first, a rolling bearing 1 is rotated in the predetermined number of rotations while load is applied to the rolling bearing 1 in the axial direction thereof and inherent vibration frequency Fn is calculated from the spring constants Ki, Ke between an inner wheel 2 and rolling bodies 4 as well as between an outer wheel 3 and the rolling bodies 4 and the mass M of the rolling bodies 4. Next, the amplitude at the vibration frequency Fn of the bearing 1 during rotation is calculated and the upper limit value of the amplitude is set. When a vibration level exceeds the upper limit value, it is judged that a lubricating condition is abnormal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in a method for monitoring the lubrication state of a rolling bearing, and particularly relates to a method for monitoring the lubrication state of a rolling bearing, in which an inner ring and a rolling element and an outer ring and a rolling element of a rolling bearing are formed in elastic contact with each other. This paper focuses on the natural frequency of a vibration system and relates to a method for monitoring the lubrication state of a rolling bearing based on the vibration amplitude at that natural frequency.

[Conventional technology]

Conventional methods for monitoring the lubrication state of rolling bearings include, for example, Japanese Patent Publication No. 58-40136 or Japanese Utility Model Publication No. 57-1982.
The one described in Japanese Patent No. 19617 is known.

In all of these conventional methods, a voltage is applied to the rolling contact portion, and the thickness of the oil film is measured as an electrical resistance value.

[Problem to be solved by the invention]

However, in such conventional methods for monitoring the lubrication condition of rolling bearings, a voltage must be applied between the inner and outer rings of the bearing in order to measure the electrical resistance of the oil film, but this method requires that a voltage be applied between the inner and outer rings of the bearing. In the case of bearings with
In many cases, measurement was impossible because the inner ring (or shaft) was not exposed, and the oil film on the bearing ran out, causing metal-to-metal contact. There is a problem in that the method cannot be measured with sufficient sensitivity unless the lubrication condition is in a very poor condition, and therefore it is not effective unless the lubrication condition is extremely poor.

This invention was made by focusing on these conventional problems, and can be easily applied to bearings incorporated in mechanical equipment, making it possible to easily monitor the lubrication state even when the oil film is thick. The purpose of this study is to provide a method for monitoring the lubrication status of rolling bearings. [Means and effects for solving the problem] Therefore, the method for monitoring the lubrication condition of a rolling bearing according to the present invention is to detect the elasticity formed between the inner ring and the rolling element and between the outer ring and the rolling element of the rolling bearing. This method determines the natural frequency of the vibration system consisting of the spring constant of the contact and the mass of the rolling elements, and monitors the lubrication state of the rolling bearing by the amplitude of this natural vibration generated by the rotating rolling bearing. When the vibration amplitude is large, it is determined that the oil film is thin, and when the vibration amplitude is small, the oil film is determined to be thick.

In addition, the natural frequency Fn of the elastic contact vibration is determined by Ki, the spring constant of the elastic contact between the inner ring and the rolling element, Ke, the spring constant of the elastic contact between the outer ring and the rolling element, and the mass of the rolling element, 1. M
When , it is given by the formula.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

First, we will explain the construction of an example of a device that implements the method of this invention. In FIG. 1, a ball bearing as an example of a rolling bearing 1 has an inner ring 2, an outer ring 3, and a plurality of balls as rolling elements 4. Then, for example, the inner ring 2 is fitted onto the spindle shaft 5, the outer ring 3 is fixed, an acceleration vibrometer 6 is attached to the outer periphery of the outer ring 3, and the detection signal of the acceleration vibrometer 6 is transferred to a frequency analyzer (FFT). Supply to 7. Next, the operation of the above embodiment will be explained. When the rolling bearing l is rotated at a predetermined rotational speed while applying a predetermined axial load, the inner ring 2
There is elastic contact between the outer ring 3 and the rolling elements 4, and between the outer ring 3 and the rolling elements 4, forming springs having spring constants Ki and Ke, respectively. . These spring constants Ki and Ke are determined by the internal design specifications and load conditions of the bearing. The inner ring 2, rolling elements 4, and outer ring 3 that are in elastic contact form an elastic contact vibration system,
If the mass of the rolling element 4 is M, its natural frequency Fn is given by: Furthermore, the lubricating oil film interposed between the inner ring 2 and the rolling elements 4 and between the outer ring 3 and the rolling elements 4 acts as a damping element for this vibration system. In other words, inner ring 2Lm Nido Muru JL
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．． Damping Ce acts between the two conductors 4, and these dampings Ci and Ce become larger values as the lubricating oil film becomes thicker, and the amplitude of the elastic contact vibration decreases. becomes smaller. In addition, the sources of vibration in this vibration system include alternating fluctuations in contact pressure due to unevenness on the surfaces of the inner ring 2, outer ring 3, and rolling elements 4, and friction phenomena due to operational slip and spin slip of the rolling elements 4. It is conceivable that the presence of an oil film has a large effect on these vibration sources, and as the thickness of the oil film increases, the vibration force decreases.

In other words, the mechanism by which the oil film thickness affects elastic contact vibration is thought to be a combination of both damping and excitation forces, but the oil film thickness and the amplitude of elastic contact vibration are closely related, and the oil film thickness If this is small, the damping ratio will be small and the excitation force will be large, and the amplitude of the elastic contact vibration will be large. Therefore, by measuring the amplitude of this elastic contact vibration, it is possible to monitor the oil film thickness, that is, the lubrication state of the bearing. As a specific example, the outer diameter is 62m+, the inner diameter is 30mm, and the width is 1mm.
When a 6mm ball bearing 6206 (JIS designation number) is loaded with an axial load of 20kgf, the natural frequency Fn is (
From equation 1), it is approximately 30KHz. This ball bearing is heated using: ■ Kerosene oil (viscosity is 1.3 cst at 40°C), ■ #8 machine oil (same <8 cst), ■ #68 turbine oil (same <68
cst) with 3 different lubricating oils, 4000 rpm+
The amplitude of vibration acceleration versus frequency when rotating at
An acceleration vibration spectrum showing the relationship G) is shown in FIG.

As is clear from this figure, several peaks appear in the rolling bearing, among which the peak around 30Kl{z is due to elastic contact vibration between the rolling elements 4 and the inner ring 2 and outer ring 3. It can be seen that the amplitude of the vibration acceleration of this peak changes more greatly depending on the viscosity of the lubricating oil, that is, the thickness of the oil film, than the other peaks.

The reason for this is that, as described above, the damping effect of the damping ratios Ci and Ce of the oil film is directly involved in the vibration system of the elastic contact vibration.

Therefore, an upper limit value is set for the vibration amplitude of this natural frequency, and if the vibration level exceeds this upper limit value, the lubrication state is determined to be abnormal and an alarm is sounded.
Stop the operation of the equipment.

〔Effect of the invention〕

As explained above, according to the method for monitoring the lubrication state of a rolling bearing according to the present invention, the spring constant of the elastic contact formed between the inner ring and the rolling element and between the outer ring and the rolling element of the rolling bearing, The natural frequency of the vibration system consisting of the mass of the rolling elements is determined, and the lubrication state of the rolling bearing is monitored by the amplitude of the natural vibration generated by the rolling bearing during rotation. It can be easily applied to bearings, and since it takes advantage of the fact that the amplitude of vibration changes depending on the thickness of the oil film, it is possible to monitor the quality of the lubrication state even when an oil film is formed on the bearing. , the ability to predict abnormalities in bearings (early detection ability) is extremely high, and the effect of being able to select an appropriate lubricant can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a cutaway front view of essential parts showing an example of a device implementing the method for monitoring the lubrication condition of a rolling bearing according to the present invention, Fig. 2 is a schematic diagram showing an elastic contact vibration system of a rolling bearing, and Fig. 3 is a frequency It is a graph which shows the relationship between and vibration amplitude. l...Rolling bearing, 2...Inner ring, 3...Outer ring, 4
...Rolling element, 5... Spindle shaft, 6... Acceleration vibrometer, 7... Frequency analyzer, Ki, Ke... Spring constant of elastic contact vibration, M... Mass of rolling element , Fn...
・Natural frequency.

Claims (2)

[Claims] (1) Determine the natural frequency of the vibration system consisting of the spring constant of the elastic contact formed between the inner ring and the rolling element and between the outer ring and the rolling element of the rolling bearing, and the mass of the rolling element, A method for monitoring the lubrication state of a rolling bearing, which monitors the lubrication state of the rolling bearing based on the vibration amplitude of the natural vibration generated by the rolling bearing during rotation. (2) The spring constant of the elastic contact between the inner ring and the rolling elements is Ki
, where Ke is the spring constant of the elastic contact between the outer ring and the rolling element, and M is the mass of the rolling element, the natural frequency Fn can be found as follows: Fn=1/2π√{(Ki+Ke)/M} The method for monitoring the lubrication state of a rolling bearing according to claim 1, characterized in that: