JP5258607B2 - Lubricating state observation method for rolling bearings - Google Patents

Description

  The present invention generates ultrasonic waves from an ultrasonic probe attached to a bearing housing on which a rolling bearing is supported toward a bearing outer ring of the bearing, and measures a reflected wave from a boundary between the bearing outer ring and a rolling element. Thus, the present invention relates to a lubricating state observation method in a rolling bearing that observes the lubricating oil and the lubricating state existing between the bearing outer ring and the rolling element.

  Rolling bearings such as ball bearings are well known as mechanical elements that support rotating shafts. When rolling bearings are used, lubricating oil is required, but with the recent energy savings, the amount of lubricating oil supplied can be reduced in order to avoid an increase in stirring resistance due to excessive supply of lubricating oil. An efficient lubricating method by spraying lubricating oil has been studied. The increase in the agitation resistance causes heat generation of the rolling bearing during rotation, and lowers the rotational accuracy, so that it is desirable to lubricate with the minimum required amount of lubricating oil.

  However, if the amount of oil is small and the required amount of lubricating oil is not supplied to the lubricated surface, solid contact due to lack of lubricating oil will cause the lubrication condition to deteriorate rapidly, resulting in surface roughness and seizure. The nature is also great. Therefore, in a lubrication state where the amount of oil is small, a technique is required that can observe the supply state of the lubrication oil between the rolling elements and the bearing outer ring or the bearing inner ring.

  On the other hand, as a technique for evaluating a damaged state of a rolling bearing, a bearing damage evaluation method disclosed in Patent Document 1 is known. This is because ultrasonic waves are generated from an ultrasonic probe attached to a bearing housing on which the bearing is supported toward the bearing outer ring of the bearing, and a reflected wave from a boundary between the bearing housing and the bearing outer ring is measured. This is to evaluate the damage generated in the bearing. Specifically, the echo height ratio calculating step for obtaining the echo height ratio from the reflected wave received by the ultrasonic probe and the damage based on the local recess in the waveform signal of the obtained echo height ratio. Is to analyze the size of.

Japanese Patent No. 3922521

  However, the above-mentioned patent document obtains information from the boundary between the bearing housing and the bearing outer ring, and does not include information from the boundary between the bearing outer ring and the rolling element. Therefore, the supply state of the lubricating oil cannot be confirmed.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a lubrication state observation method for a rolling bearing capable of observing a shortage of lubricating oil existing between a bearing outer ring and a rolling element of the rolling bearing. That is.

In order to solve the above problems, the lubrication state observation method in the rolling bearing according to the present invention is:
By generating an ultrasonic wave from an ultrasonic probe attached to a bearing housing in which the rolling bearing is supported toward the bearing outer ring of the bearing, and measuring a reflected wave from a boundary between the bearing outer ring and the rolling element, It is intended to observe the lubricating oil and lubrication state existing between the bearing outer ring and the rolling elements,
The ultrasonic probe receives a reflected wave including a first reflected wave from a boundary between the bearing housing and the bearing outer ring and a second reflected wave from a boundary between the bearing outer ring and a rolling element; ,
The peak position (sound axis) of the first reflected wave and the second reflected wave are extracted from the reflected waves received by the ultrasonic probe, and the echo height ratio (H ₁ , H ₂ ) is extracted. An echo height ratio calculating step for obtaining a lubrication state observation method in a rolling bearing having:
In the waveform signal of the echo height ratio (H ₂ ) for the obtained second reflected wave, the local convex part of the waveform before the rolling element comes on the sound axis of the ultrasonic probe, and the rolling element is the sound. And a step of observing the lubrication state based on a time shift amount (Δt) between the peak position (of the concave portion) of the concave waveform portion after passing on the axis and the sound axis (Δt). is there.

  The operation and effect of the lubricating state observation method with this configuration will be described. In order to observe the lubrication state, an ultrasonic probe is used in the present invention. An ultrasonic probe is attached to a bearing housing in which the rolling bearing is supported, and ultrasonic waves are irradiated toward the outer ring of the bearing. The ultrasonic wave irradiated toward the outer ring is reflected at the boundary between the bearing housing and the bearing outer ring, and also reflected at the boundary between the bearing outer ring and the rolling element. Although these reflected waves are received by the ultrasonic probe, they are received with a time lag, so the reflected wave from the boundary between the bearing outer ring and the rolling element is reflected at the boundary between the bearing housing and the bearing outer ring. It is possible to receive in a state separated from the reflected wave from.

The echo height ratio is obtained from the received reflected wave. This is a physical quantity that is used (to standardize) to quantitatively represent the magnitude of the reflected wave. The echo height ratio (H) is, for example,
H ₁ = (1-h ₁ / h ₀ ) × 100 (Equation 1-1)
H ₂ = (1-h ₂ / h ₀ ) × 100 (Equation 1-2)
Defined by h ₁ and h ₂ are the echo heights (magnitudes of the reflected waves) of the first reflected wave and the second reflected wave, and h ₀ is the sound of the ultrasonic probe between the rolling elements. The echo height when the axis is located. Therefore, the echo height ratio H is a measure of the ease of transmission of sound waves from each boundary surface, and the presence of lubricating oil and the evaluation of the lubricating state are evaluated by H ₂ . Note that the magnification of 100 is to display%, and the present invention is not limited to this. Note that how h ₀ is set is not limited to the above.

In the waveform signal of the echo height ratio obtained as described above, the local convex part of the waveform before the rolling element comes on the sound axis of the ultrasonic probe, and after the rolling element has passed on the sound axis The inventor of the present invention has found that the lack of lubricating oil can be observed based on the amount of time deviation between the peak position of the concave portion of the corrugated portion and the sound axis. The sound axis is a coordinate axis representing the direction in which the ultrasonic probe emits ultrasonic waves, and is determined as the peak position of the echo height ratio H ₁ in the first reflected wave.

  A specific waveform signal is shown in FIG. This waveform signal is for an ultrasonic probe that emits 2 MHz ultrasonic waves. Such an ultrasonic probe has a characteristic that the ultrasonic irradiation region in the observation region is wide and the sensitivity is high with respect to a relatively thick oil film (for example, 100 μm).

  FIG. 9A shows a waveform signal of the echo height ratio, and is a waveform in a state where the lubricating oil is appropriately supplied. What is indicated by A on the left side of the sound axis y is a corrugated concave portion and a local convex portion before the rolling element comes on the sound axis. The amount of lubricating oil is large on the inlet side of the gap between the rolling elements and the bearing outer ring, and is small on the outlet side. Due to the presence of the lubricating oil on the inlet side, there is an ultrasonic wave transmitted from the bearing outer ring into the lubricating oil. Due to this, it is considered that a local convex portion A having a waveform is formed. Therefore, by observing the transition of the local convex portion A, it is considered that the lubricating state of the lubricating oil (whether it is sufficient or insufficient) can be observed. Further, as will be described later, it was confirmed that the local protrusion A gradually disappears when the lubricating oil becomes insufficient.

  Further, the supply amount of the lubricating oil is different as described above between the inlet side and the outlet side of the rolling element. Therefore, the waveform signal is not symmetric with respect to the sound axis, and a time shift amount Δt is generated between the peak position of the concave portion of the waveform portion and the sound axis y that can be confirmed by the first reflected wave. This time shift amount Δt depends on the supply amount of the lubricating oil, and it was confirmed that the time shift amount Δt decreases as the lubricating oil becomes insufficient.

  By paying attention to the characteristics of the waveform as described above, it was found that the lubricating oil and the lubrication state existing between the outer ring (inner ring) of the rolling bearing and the rolling element can be observed by the ultrasonic probe. .

In order to solve the above-mentioned problem, another lubrication state observation method in the rolling bearing according to the present invention is:
By generating an ultrasonic wave from an ultrasonic probe attached to a bearing housing in which the rolling bearing is supported toward the bearing outer ring of the bearing, and measuring a reflected wave from a boundary between the bearing outer ring and the rolling element, It is intended to observe the lubricating oil and lubrication state existing between the bearing outer ring and the rolling elements,
The ultrasonic probe receives a reflected wave including a first reflected wave from a boundary between the bearing housing and the bearing outer ring and a second reflected wave from a boundary between the bearing outer ring and a rolling element; ,
A rolling bearing having a peak position (sound axis) of the first reflected wave as a reference and an echo height ratio calculating step for extracting the second reflected wave and obtaining each echo height ratio (H ₁ , H ₂ ). A method for observing the lubrication state in
In the waveform signal of the echo height ratio (H ₂ ) for the obtained second reflected wave, the peak amount of the local convex portion of the second reflected wave located near the sound axis of the ultrasonic probe or the sound axis, And a step of observing the lubrication state based on a change in the time difference Δt between the concave peak position and the sound axis.

  The operation and effect of the lubricating state observation method with this configuration will be described. The point of obtaining the waveform signal of the echo height ratio is the same as the configuration of the above-described invention.

  Another specific waveform signal is shown in FIG. This waveform signal is for an ultrasonic probe that emits a 10 MHz ultrasonic wave. Such an ultrasonic probe has a characteristic that an ultrasonic irradiation region in the observation region is narrow and a relatively thin oil film (for example, 20 μm or less) can be detected with high sensitivity. Unlike the case where the waveform signal of the echo height ratio obtained is 2 MHz, the feature quantity to be noticed changes depending on the characteristics of this ultrasonic probe.

In this case, attention was paid to the peak amount ΔH of the waveform portion located in the vicinity of the sound axis y or the sound axis y determined by the peak of the first reflected wave. When the lubricating oil is properly supplied, the sound wave that reaches the outer ring is easily transmitted to the rolling element side, and the H ₂ peak is directed upward, but if the lubricating oil is insufficient or the surface becomes rough, It was confirmed that the peak amount gradually decreased because the amount of sound waves transmitted to the rolling elements decreased.

  By paying attention to the characteristics of the waveform as described above, it was found that the lubrication state of the lubricating oil existing between the bearing outer ring of the rolling bearing and the rolling element can be observed by the ultrasonic probe.

Diagram explaining the positional relationship between the ultrasound probe and the ball The figure which shows the waveform of the reflected wave (echo signal) received by the ultrasonic probe Diagram showing echo height ratio waveform signal Schematic diagram showing the outline of the observation equipment Block diagram showing the functions of the observation equipment Diagram explaining the state of the bearing used for measurement Diagram explaining the difference between ultrasound probes The figure which shows the measurement result (2MHz ultrasonic probe) The figure which shows a measurement result (10MHz ultrasonic probe) A chart summarizing the indicators for evaluating the lack of lubricating oil Diagram showing measurement results of bearing surface roughness before and after experiment Graph showing characteristics of ultrasonic probe

  A preferred embodiment of a lubrication state observation method for a rolling bearing according to the present invention will be described with reference to the drawings. A ball bearing will be described as an example of a rolling bearing.

<Principle of ultrasonic observation>
First, in the present invention, the principle for observing the lubrication state with an ultrasonic probe will be described. FIG. 1 is a diagram for explaining the positional relationship between an ultrasonic probe and a ball (corresponding to a rolling element). FIG. 2 is a waveform of a reflected wave (echo signal) received by the ultrasonic probe. FIG. 3 is a diagram showing a waveform signal of the echo height ratio of the first and second reflected waves. FIG. 4 is a schematic diagram showing an outline of the observation apparatus.

  As shown in FIG. 4, the bearing includes a bearing outer ring 1, a bearing inner ring 3, and a large number of balls 2 positioned therebetween. As shown in FIG. 1, if the inner ring 3 rotates in the direction of the arrow, the ball revolves counterclockwise while rotating clockwise as shown. A load acts between the ball 2 and the bearing outer ring 1, and a surface pressure distribution P2 is formed. A large surface pressure acts at the point where the ball 2 is located, and the surface pressure does not act at a position where the ball 2 does not exist.

  Further, the surface pressure acts also between the bearing outer ring 1 and the bearing housing 4, and the surface pressure distribution is indicated by P1. The peak position of the surface pressure is substantially the same as the surface pressure distribution P2. However, the distribution curve is gentler than the surface pressure distribution P2.

  The ultrasonic probe 5 is attached to the outside of the bearing housing 4 by an appropriate method. The sound axis y faces the direction of the rotation center of the bearing B. The ultrasonic probe 5 is irradiated to an area having a certain width around the sound axis y. The ultrasonic waves are irradiated toward the boundary between the bearing housing 4 and the bearing outer ring 1 and toward the boundary between the bearing outer ring 1 and the ball 2.

  The ultrasonic wave irradiated from the ultrasonic probe 5 first goes to the boundary between the bearing housing 4 and the bearing outer ring 1, but is partially reflected and partially transmitted through this boundary. The amount of transmitted ultrasonic waves changes depending on the size of the surface pressure distribution P1. Specifically, the greater the surface pressure distribution P 1, the easier it is to transmit, and the transmitted ultrasonic waves travel toward the boundary between the bearing outer ring 1 and the ball 2.

FIG. 1A shows a case where the sound axis y is located between the balls 2 and 2, and the surface pressure on the sound axis at this time is the smallest. Accordingly, the magnitude h ₀ of the first reflected wave at this time is the largest. This h ₀ is used as a standard value when obtaining the echo height ratio. This reflected wave is received by the ultrasonic probe 5.

FIG. 1B is a diagram showing a state where the ball 2 is approaching on the sound axis. Since the surface pressure between the bearing outer ring 1 and the bearing housing 4 gradually increases, the ultrasonic wave transmitted into the bearing outer ring 1 increases and moves toward the boundary C2 between the bearing outer ring 1 and the ball 2. The transmitted ultrasonic wave is partially reflected at the boundary C2 and partially transmitted to the ball 2 and the oil film. The magnitude h ₂ of the reflected wave at the boundary C2 depends on the lubrication state at the boundary C2.

Since the surface pressure distribution P1 exists between the ball 2 and the bearing outer ring 1 as described above, the magnitude h ₂ of the reflected wave depends on the magnitude of the pressure between the two and It also depends on the amount of lubricating oil supplied between the bearing outer rings 1. That is, since the transmitted ultrasonic wave partially passes through the lubricating oil via the boundary C2, the magnitude h ₂ of the reflected wave is also affected depending on the lubrication state. When the lubricating oil is insufficient, the transmission of ultrasonic waves into the lubricating oil is lost, and the effect is considered to appear in the received waveform.

  Incidentally, the amount of lubricating oil existing between the ball 2 and the bearing outer ring 1 is larger at the inlet side E1 into which the lubricating oil enters, as shown in FIG. Is less. Since the ball 2 rotates in the clockwise direction as shown, between the bearing outer ring 1 and the ball 2, the left side from the contact point is the inlet side E1, and the right side is the outlet side E2. Conversely, between the bearing inner ring 3 and the ball 2, the right side is the inlet side and the left side is the outlet side.

FIG. 1 (c) shows a state when the ball 2 comes directly below the sound axis. In this case, the magnitude h ₁ of the reflected wave at the boundary C ₁ is almost minimized, and the amount of ultrasonic waves toward the boundary C 2 between the bearing outer ring 1 and the ball 2 increases.

  FIG.1 (d) has shown the dry state, ie, the state in which lubricating oil does not exist. In this case, there is no ultrasonic wave that penetrates into the lubricating oil, and only transmission to the solid contact portion with the ball 2, so that the received signal waveform is also affected.

<Signal waveform>
Next, a specific example of the waveform of the reflected wave (echo signal) received by the ultrasonic probe 5 is shown in FIG. The horizontal axis represents time, and the vertical axis represents the magnitude of the reflected wave. As shown in the figure, the reflected wave is composed of a first reflected wave that is earlier in time and a second reflected wave that is later in time. The first reflected wave is a reflected wave from the boundary C <b> 1 between the bearing housing 4 and the bearing outer ring 1. The second reflected wave is a reflected wave from the boundary C <b> 2 between the bearing outer ring 1 and the ball 2. As shown in FIG. 2, since there is a temporal shift in wt between the peak position of the first reflected wave and the peak position of the second reflected wave, the second reflection is performed with reference to the peak position of the first reflected wave. The peak position of the wave can be taken out. In this way, it is possible to observe in a state having a temporal deviation, and it is possible to observe only the reflected wave from the boundary C2. The deviation amount wt is determined by the structure of the bearing and can be predicted to be within a predetermined range.

For the magnitude h ₁ of the first reflected wave and the magnitude h ₂ of the second reflected wave, the peak value (maximum value) in the waveform component is selected. Of the first reflected wave, the magnitude of the first reflected wave obtained when positioned between the acoustic axis y exactly the ball 2 and the ball 2 as shown in FIGS. 1 (a) is represented by h _0.

  Further, when evaluating the lubrication state, a physical quantity called an echo height ratio H is used instead of the magnitude of the reflected wave. The echo height ratio is expressed by the following equation.

H = (1-h / h ₀ ) × 100 (Equation 1)
Further, when the reflected wave from the boundary C1 is expressed by an echo height ratio, H ₁ = (1−h ₁ / h ₀ ) × 100 (Equation 2)
When the reflected wave from the boundary C2 is expressed by an echo height ratio,
H ₂ = (1−h ₂ / h ₀ ) × 100 (Equation 3)
As described above, the evaluation is not performed by the reflected wave (echo height) but by the standardized echo height ratio H.

<Example of observed waveform>
FIG. 3 shows the actually observed echo height ratio. The upper side (b) is the second echo height ratio H ₂ due to the second reflected wave, and the lower side (b) is the f first echo height ratio H ₁ due to the first reflected wave. In the case of the first echo height ratio, just below the sound axis, the amount of transmitted ultrasonic waves increases, so h ₁ decreases. If h ₁ is 0, H ₁ = 1. Further, in the case shown in FIG. 1A, since h ₁ ≈h ₀ , H ₁ = 0. Therefore, as shown in the figure, a waveform is obtained such that the echo height ratio H ₁ is maximized immediately below the sound axis.

FIG. 3A is a diagram showing a waveform signal of the echo height ratio due to the second reflected wave, where the solid line indicates an appropriate supply of lubricant, and the broken line indicates a state where the lubricant is insufficient or in a dry state. The signal waveform in is shown. The waveform of the second echo height ratio H ₂ will be described later. Incidentally, although the influence of the lubrication state does not appear in the first echo height ratio H ₁ , the change in the lubrication state appears remarkably with respect to the second echo height ratio H ₂ .

<Configuration of observation device>
Next, the configuration of an observation apparatus for observing the lubrication state based on the echo height ratio will be described with reference to FIG. The bearing B used is a single row deep groove ball bearing (6212). The bearing outer ring 1, the ball 2, and the bearing inner ring 3 are configured. The inner diameter of the bearing inner ring 3 is 60 mm, and the outer diameter of the bearing outer ring 1 is 110 mm. The outer periphery of the bearing outer ring 1 is held so as to be sandwiched by a pair of bearing housings 4 in the vertical direction. A preload of W = 40 kN was applied to the bearing B in the vertical direction.

  An ultrasonic probe 5 was attached to the upper part of the bearing housing 4 and directly above the rotation center of the bearing B. The sound axis of the ultrasonic probe 5 is in the vertical direction and is directed toward the rotation center of the bearing B. As the ultrasonic probe 5, those having ultrasonic waves of 2 MHz and 10 MHz were used. The ultrasonic probe 5 can transmit ultrasonic waves and receive reflected waves that have been reflected back.

  The ultrasonic probe 5 is connected to an ultrasonic flaw detector 6, and this ultrasonic flaw detector 6 performs driving of the ultrasonic probe 5, signal processing, display / analysis of received reflected waves, and the like. Can do. Further, it has a function of digitally processing the received analog signal and transmitting it to the personal computer 7.

  The ultrasonic flaw detector 6 is further connected to a personal computer 7 (computer), and can receive a digitally processed signal from the ultrasonic flaw detector 6 and perform waveform analysis, display of the analyzed waveform, and the like. it can. A general-purpose computer can be used as the personal computer 7, and dedicated software for waveform analysis is installed.

<Functional blocks of observation equipment>
Next, functions of the observation apparatus shown in FIG. 4 will be described with reference to a block diagram. This function is realized by the ultrasonic flaw detector 6 and the personal computer 7, and software for observation is also used.

The reflected wave signal receiving means 10 receives the reflected wave signal received by the ultrasonic probe 5. The reference reflected wave peak value detection means 11 detects the magnitude h ₀ of the reference reflected wave from the received reflected wave signal. The first reflected wave peak value detection means 12 detects the peak value h ₁ from the first reflected wave (the reflected wave from the boundary C1 between the bearing housing 4 and the bearing outer ring 1) among the received reflected waves. The second reflected wave peak value detecting means 13 detects the peak value h ₂ from the second reflected wave (the reflected wave from the boundary C2 between the bearing outer ring 1 and the ball 2) among the received reflected waves. As described above, the peak position of the second reflected wave can be recognized using the peak position of the first reflected wave as a reference.

The first echo height ratio calculating means 14 calculates the first echo height ratio based on the obtained h ₀ and h ₁ . The second echo height ratio calculating means 15 calculates a second echo height ratio based on the obtained h ₀ and h ₂ .

  The local convex part detection means 17 detects the local convex part contained in the waveform signal of the second echo height ratio. The Δt calculating means 18 calculates Δt from the difference between the concave waveform signal having the second echo height ratio and the peak position of the first reflected wave. The ΔH calculator 19 calculates ΔH from the waveform signal of the second echo height ratio. These local protrusions, Δt, and ΔH will be described later. These calculations can be performed by extracting the feature quantity of the waveform.

  It is also possible to set a threshold value in advance and perform automatic determination such as whether or not a shortage of lubricating oil is starting to occur. For example, when the magnitude of Δt or ΔH exceeds a preset threshold value, it can be determined that the lubricating oil is insufficient. Further, the shape of the local convex portion can be extracted, and the lubrication state can be evaluated from the reduction amount of the convex portion.

  The display means 7a (monitor) displays the received waveform signal, the calculated echo height ratio waveform signal, and the like on the monitor screen. Moreover, the detection result of a local convex part and the calculation result of (DELTA) t and (DELTA) H can also be displayed.

<Experimental conditions>
Next, experimental conditions will be described. First, FIG. 5 is a diagram illustrating the state of the bearing used for measurement.

  FIG. 5 (a) shows a state in which the bearing is received, and an oil film as a rust preventive agent is formed on the surfaces of the bearing outer ring 1 and the bearing inner ring 3. Next, ultrasonic cleaning with acetone is performed twice with respect to the received bearing. Thereby, it can be set as a dry state bearing as shown in (b). Further, a lubricant is sprayed on the dry bearing. The lubricant used was a mineral oil based synthetic lubricant (CRC5-56), and the spray amount was 0.5 cc. Although the amount of spraying was small compared with normal use conditions, it was set to a small amount in order to confirm the experimental results early.

  Next, the ultrasonic probe will be described. The ultrasonic probes used were those that irradiate 2 MHz ultrasonic waves and 10 MHz ultrasonic waves, respectively. Each characteristic will be described.

  FIG. 11 is a graph showing characteristics in the case of irradiating pulsed ultrasonic waves with an ultrasonic probe. The vertical axis of the graph represents the echo height h, and the horizontal axis represents the ratio between the film thickness L and the wavelength λ. As can be seen from this figure, the range in which the change in the echo height h is detected with respect to the change in the film thickness ratio is limited. If L / λ ≦ 0.1, the change in the film thickness Can be detected with high accuracy. Therefore, it can be seen that the detectable range changes depending on the size of λ (the wavelength of the ultrasonic wave).

  From the above, the ultrasonic probe of 2 MHz has a characteristic that the wavelength of the ultrasonic wave is long and a relatively thick oil film can be detected as compared with the 10 MHz probe. For example, it is possible to detect even an oil film of 100 to 200 μm. That is, it is possible to detect a change in film thickness in a situation where a certain amount of oil film is present (a location far away from Hertz contact). Therefore, as shown in FIG. 1, it is possible to easily observe the transition of the lubricating oil to the insufficient state on the inlet side E1.

  Further, as shown in FIG. 6A, the ultrasonic irradiation region is relatively wide. Compared to the EHL (elastohydrodynamic lubrication) region between the ball 2 and the bearing outer ring 1, the ultrasonic irradiation region is considerably widened. Specifically, the EHL region is about φ0.3 mm, and the irradiation region is about φ7 to 10 mm.

The waveform signals of the first reflected wave and the second reflected wave are displayed together. Since the irradiation area is relatively wide, there are areas where the two reflected wave signals partially interfere with each other, but the level is separable and there is no problem. Therefore, the peak values h ₁ and h ₂ can be extracted individually.

  The ultrasonic probe of 10 MHz has a characteristic that the wavelength of the ultrasonic wave is relatively short and it is difficult to detect a thick film, but it is easy to detect a thin film. That is, it is suitable for observation of lack of lubricating oil and a solid contact state in the thin film portion near the EHL region. For example, a change in the lubrication state of a thin film of about 20 μm can be detected. Further, the range of the irradiation area is relatively narrow.

  As shown in FIG. 6B, the ultrasonic irradiation region is set to be slightly larger than the EHL region. In addition, since the vibration of the vibrator is easily attenuated, the waveform signals of the first reflected wave and the second reflected wave are received in a clearly separated state.

<Observation result (2 MHz)>
Next, experimental results obtained under the above experimental conditions will be described in order. FIG. 7 shows an observation result when the above-described lubricating oil (mineral oil 0.5 cc) is sprayed on the bearing using a 2 MHz ultrasonic probe. (A) shows the measurement result in the initial stage of operation. The upper row is the second echo height ratio H ₂ , the lower row is the first echo height ratio H ₁ , and the unit of the vertical axis is%. The horizontal axis represents the time axis. (B) is after 50 minutes and (c) is after 100 minutes.

As can be seen from these three graphs, with respect to the first echo height ratio H _1, there is a peak value of the waveform on the sound axis, and no significant change is seen over time. On the other hand, the second echo height ratio H ₂ has a characteristic in the waveform itself, and also changes with the passage of time. The inventor of the present application has found that this change indicates that the supply state of the lubricating oil changes, that is, the lubricating oil gradually becomes deficient and eventually becomes dry. is there.

7 (d) is an enlarged view showing the feature of the second echo height ratio of H ₂ waveforms. With respect to the sound axis y, the local protrusion A is seen on the earlier side in time. This is the first feature. This early side can be said to have captured the supply state of the lubricating oil at the inlet side E1. When lubricating oil is present on the inlet side E1, ultrasonic waves are transmitted through the boundary C2 into the lubricating oil. This permeation amount varies depending on the amount of lubricating oil.

  As can be seen by comparing the graphs of FIGS. 7A, 7B, and 7C, the local convex portion A becomes smaller as time passes, and finally the local convex portion A disappears. At this time, it is considered that the lubricating oil is considerably insufficient or the lubricating oil is not present.

  In addition, the waveform portion located on the side later in time than the sound axis y has a peak position of the concave portion (a place where the minimum value is taken), but this peak position is not on the sound axis and the deviation amount Δt It is only shifted. This deviation can be presumed to be because the amount of lubricating oil is different between the inlet side E1 and the outlet side E2, that is, the lubricating oil exists asymmetrically with respect to the sound axis y.

As can be seen by comparing the graphs of FIGS. 7A, 7B, and 7C, the above Δt becomes smaller with time, and finally Δt = 0, that is, the peak position is on the sound axis. It is estimated to be. As shown in FIG. 7C, it is considered that the waveform signal itself having the second echo height ratio H ₂ is asymmetric to symmetric (substantially symmetric) when coming on the sound axis. In this state, the lubricating oil is considerably insufficient or in a dry state without the lubricating oil, and the lubrication state of the inlet side E1 and the outlet side E2 is symmetric with respect to the sound axis y (the inlet side E1 is also the outlet side). E2 also has no lubricating oil), and the waveform itself is thought to approach symmetry.

<Observation result (10 MHz)>
FIG. 8 shows an observation result when the above-described lubricating oil (mineral oil 0.5 cc) is sprayed on the bearing using a 10 MHz ultrasonic probe. (A) shows the measurement result in the initial stage of operation. The upper row is the second echo height ratio, the lower row is the first echo height ratio, and the unit of the vertical axis is%. The horizontal axis represents the time axis. (B) is after 30 minutes and (c) is after 180 minutes.

As can be seen from these three graphs, as for the first echo height ratio H _1, there is a peak value of the waveform on the sound axis as in the case of the ultrasonic probe of 2 MHz, and as time passes, There is no noticeable change. On the other hand, the second echo height ratio H ₂ has a characteristic in the waveform itself, and also changes with the passage of time. This change is considered to indicate that the supply state of the lubricating oil changes, that is, the lubricating oil gradually becomes deficient and finally becomes dry.

As can be seen by comparing the graphs of FIGS. 8A, 8B, and 8C, the peak amount ΔH of the convex waveform located on the sound axis y (or in the vicinity of the sound axis) gradually decreases with time. It was observed to go down. Although the waveform is different from that in FIG. 7, this is because, in the case of a 10 MHz ultrasonic probe, only the change in the portion where the irradiation area is relatively narrow and the oil film is thin is captured significantly. In the thick film portion, as shown in FIG. 11, H ₂ is almost the same as that in the dry state, and the change in H ₂ there is not remarkable, so the difference in the supply amount of lubricating oil between the inlet side E1 and the outlet side E2 There is no waveform asymmetry due to.

Therefore, the change in the vicinity of the EHL region where the irradiation of ultrasonic waves is dominated by the thin film is noticeable. That is, in the initial state, there is lubricating oil, and the amount of sound waves transmitted to the thin film and the ball 2 increases near the sound axis (near the EHL region), and ΔH appears high, but when the lubricating oil gradually becomes insufficient Because there is no lubricating oil near the contact area and only transmission of sound waves from the solid contact area in the dry state can be expected, the amount of transmission from the bearing outer ring to the ball side decreases, and the peak of H ₂ on the sound axis The value drops. In addition, because of surface roughness due to solid contact, the peak value of H ₂ is further reduced. Therefore, it can be considered that this peak amount ΔH can evaluate the lack of lubricating oil and the rough surface state of the ball 2 and the bearing outer ring 1.

<Summary of evaluation indicators>
Next, FIG. 9 collectively shows an evaluation index for lack of lubricating oil and surface roughness from the waveform signal of the second echo height ratio.
(1) When a 2 MHz ultrasonic probe is used, evaluation can be performed based on the size of the local convex portion A of the waveform and the symmetry (Δt) of the waveform.
(2) When a 10 MHz ultrasonic probe is used, evaluation can be performed based on the peak amount ΔH on the sound axis.

  FIG. 10 shows an actual measurement of the surface roughness of the bearing used in the experiment. (A) is a measurement of the surface roughness of the outer ring, inner ring and ball before the experiment, and (b) is a measurement of the surface roughness in the same manner after the experiment. After the experiment, the surface roughness was considerably large, and it was confirmed that surface roughness occurred due to lack of lubricating oil. From this, it can be said that it was proved that the change in surface roughness appeared in the waveform signal of the second echo height ratio.

<Another embodiment>
In the present embodiment, the type of rolling bearing has been described by taking a single-row deep groove ball bearing as an example, but the present invention is not limited to this.

1 Bearing outer ring 2 Ball 3 Bearing inner ring 4 Bearing housing 5 Ultrasonic probe Δt Deviation amount ΔH Peak amount h, h ₁ , h ₂ Reflected wave size (echo height)
y acoustic axis A locally convex portions C1, C2 boundary E1 inlet side E2 outlet H, H _1, H ₂ echo height ratio P1, P2 surface pressure distribution

Claims (2)

By generating an ultrasonic wave from an ultrasonic probe attached to a bearing housing in which the rolling bearing is supported toward the bearing outer ring of the bearing, and measuring a reflected wave from a boundary between the bearing outer ring and the rolling element, It is intended to observe the lubricating oil and lubrication state existing between the bearing outer ring and the rolling elements,
The ultrasonic probe receives a reflected wave including a first reflected wave from a boundary between the bearing housing and the bearing outer ring and a second reflected wave from a boundary between the bearing outer ring and a rolling element; ,
An echo height ratio for obtaining each echo height ratio (H ₁ , H ₂ ) by extracting a reference first reflected wave and a second reflected wave from the reflected waves received by the ultrasonic probe. A lubrication state observation method for a rolling bearing having a calculation step,
The peak position of the echo height ratio (H ₁ ) of the first reflected wave is determined as the sound axis of the ultrasonic probe,
Echo height ratio measurement time for the second reflected wave obtained echo height ratio representing the distribution of (H ₂₎ in the waveform signal (H _2), rolling elements the acoustic axis of the ultrasonic probe The echo height ratio (H ₂ ) when the local convex portion of the waveform before coming up and the peak position of the concave waveform portion after the rolling element passes over the sound axis and the rolling element on the sound axis And a step of observing the lubrication state based on an amount of time deviation (Δt) with respect to the time position . A method for observing a lubrication state in a rolling bearing.
However, the echo height ratio (H ₁ , H ₂ ) is defined by the following equation.
H ₁ = (1−h ₁ / h ₀ ) × 100
H ₂ = (1−h ₂ / h ₀ ) × 100
h ₁ and h ₂ are the echo heights of the first and second reflected waves,
h ₀ is the echo height when the sound axis is located between the rolling elements. By generating an ultrasonic wave from an ultrasonic probe attached to a bearing housing in which the rolling bearing is supported toward the bearing outer ring of the bearing, and measuring a reflected wave from a boundary between the bearing outer ring and the rolling element, It is intended to observe the lubricating oil and lubrication state existing between the bearing outer ring and the rolling elements,
The ultrasonic probe receives a reflected wave including a first reflected wave from a boundary between the bearing housing and the bearing outer ring and a second reflected wave from a boundary between the bearing outer ring and a rolling element; ,
An echo height ratio for obtaining each echo height ratio (H ₁ , H ₂ ) by extracting a reference first reflected wave and a second reflected wave from the reflected waves received by the ultrasonic probe. A lubrication state observation method for a rolling bearing having a calculation step,
The peak position of the echo height ratio (H ₁ ) of the first reflected wave is determined as the sound axis of the ultrasonic probe,
Echo when the waveform signals of an echo height ratio measurement time for the second reflected wave obtained echo height ratio representing the distribution of _{(H 2) (H 2)} , which rolling elements are on the acoustic axis based on the change in the height ratio peak amount of time position or convex waveform portion located near the (H ₂₎ (ΔH), and having the steps of: observing the lubrication rolling bearing Lubricating state observation method in
However, the echo height ratio (H ₁ , H ₂ ) is defined by the following equation.
H ₁ = (1−h ₁ / h ₀ ) × 100
H ₂ = (1−h ₂ / h ₀ ) × 100
h ₁ and h ₂ are the echo heights of the first and second reflected waves,
h ₀ is the echo height when the sound axis is located between the rolling elements.

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