JP7419873B2 - Lubricant deterioration state detection device - Google Patents

Description

The present invention relates to a lubricant deterioration state detection device .

Rolling bearings are lubricated by a lubricant such as lubricating oil or grease, and when the lubricant deteriorates, temperature increases and wear occur in the rolling bearing, which can cause abnormalities such as seizure of the rolling bearing. It is known that a carbonyl compound is produced when a lubricant deteriorates, and that the state of deterioration of the lubricant can be detected by measuring this carbonyl compound. For example, Patent Document 1 proposes detecting the deterioration state of a lubricant by sucking gas generated inside a housing containing a rolling bearing and analyzing the sucked gas with a constant potential electrolysis type gas sensor. There is.

Patent No. 6421893

Potential electrolytic gas sensors lack sufficient detection sensitivity, and some lubricants may not be able to detect deterioration due to gas selectivity, so there is room for improvement. .
An object of the present invention is to improve detection sensitivity and gas selectivity in a device that detects the deterioration state of lubricant in rolling bearings.

A lubricant deterioration state detection device according to one aspect of the present invention includes a semiconductor gas sensor.
A lubricant deterioration state detection device according to another aspect of the present invention includes a housing housing a rotatable rolling bearing, a semiconductor gas sensor arranged outside the housing and detecting the concentration of a target gas, and a semiconductor gas sensor inside the housing. and a guide flow path that communicates with the housing and guides the gas in the housing to the semiconductor gas sensor, and detects the deterioration state of the lubricant of the rolling bearing according to the detection result of the semiconductor gas sensor.
A lubricant deterioration state detection method according to another aspect of the present invention detects a lubricant deterioration state by detecting target gas generated due to deterioration of a lubricant lubricating a rolling bearing with a semiconductor gas sensor. .

According to the present invention, by detecting the target gas generated from the lubricant of a rolling bearing with a semiconductor gas sensor, detection sensitivity and gas selectivity when detecting the deterioration state of the lubricant can be improved.

It is a figure showing a lubricant deterioration state detection device. This is a drive circuit for a semiconductor gas sensor. It is a figure which shows the switching of a flow path. It is a graph showing the test results of Examples. It is a graph showing test results of comparative examples. It is a figure showing a modification.

Embodiments of the present invention will be described below based on the drawings. Note that each drawing is schematic and may differ from the actual drawing. Furthermore, the following embodiments are intended to exemplify an apparatus and method for embodying the technical idea of the present invention, and the configuration is not limited to the following. That is, the technical idea of the present invention can be modified in various ways within the technical scope described in the claims.

《Embodiment》
"composition"
FIG. 1 is a diagram showing a lubricant deterioration state detection device.
The lubricant deterioration state detection device 11 includes a housing 12 , a semiconductor gas sensor 13 , and a guide channel 14 .
The housing 12 houses a rotatable rolling bearing 15. The rolling bearing 15 may be of any type, such as a ball bearing, a roller bearing, a needle bearing, a tapered roller bearing, a spherical roller bearing, or a thrust bearing. The rolling bearing 15 is lubricated with a lubricant, and for example, general-purpose grease is used as the lubricant.
The semiconductor gas sensor 13 is arranged outside the housing 12 and detects the concentration of the target gas. The target gas includes at least one of alcohol, ketone, aldehyde, and organic acid produced as the lubricant deteriorates.

The guide channel 14 communicates with the inside of the housing 12 and guides the gas inside the housing 12 to the semiconductor gas sensor 13 . Specifically, one side is connected to the housing 12 and the other side is connected to the suction port of the pump 16, and the semiconductor gas sensor 13 is provided between the housing 12 and the pump 16. A filter 17 is provided between the housing 12 and the semiconductor gas sensor 13 in the guide channel 14 . The filter 17 is, for example, a ceramic filter that removes oil mist and the like contained in the gas. As the filter 17, it is preferable to use a filter having a mesh size of about 200 mesh and capable of collecting oil mist particles having a particle size of 0.3 μm or more.

A branch point is provided in the guide channel 14 between the filter 17 and the semiconductor gas sensor 13, and a branch channel 21 branched from the branch point is open to the outside of the housing 12. A valve 22 (first flow path switching section, flow path switching section) is provided at the branch point. The valve 22 is a three-way valve that switches the gas guided to the semiconductor gas sensor 13 to either the gas inside the housing 12 or the gas outside the housing 12. A filter 23 is provided in the branch flow path 21 . The filter 23 is, for example, an activated carbon filter that removes contaminants such as dust and dust.

FIG. 2 shows a drive circuit for a semiconductor gas sensor.
The semiconductor gas sensor 13 includes a heater resistor 31 and a sensor resistor 32 made of a metal oxide semiconductor such as stannic oxide SnO2. The heater resistor 31 heats the metal oxide semiconductor to an operating temperature of about 200 to 500° C. by applying a heater voltage Eh. A load resistor 33 is connected in series to the sensor resistor 32, and a circuit voltage Ec is applied to the sensor resistor 32 and the load resistor 33 in order to measure the voltage Eout across the load resistor 33. Since the conductivity of the sensor resistor 32 changes depending on the concentration of the target gas, the concentration of the target gas is detected by determining the resistance of the sensor resistor 32. Specifically, as shown in the following equation, the resistance value RS of the sensor resistor 32 is calculated according to the circuit voltage Ec, the voltage Eout across the load resistor 33, and the resistance value RL of the load resistor 33.
RS={(Ec×RL)/Eout}-RL

Next, a method for detecting the deterioration state of the lubricant will be explained.
FIG. 3 is a diagram showing switching of flow paths.
(a) in the figure shows the state during sensor cleaning. Before detecting the deterioration state of the lubricant, the semiconductor gas sensor 13 is cleaned. First, the valve 22 is switched to a state of communication with the outside of the housing 12, and the pump 16 is driven. As a result, the gas outside the housing 12 is guided to the semiconductor gas sensor 13 via the branch flow path 21, and the guide flow path 14 around the semiconductor gas sensor 13 and the surface of the sensor resistor 32 in the semiconductor gas sensor 13 are cleaned. be done. Since it is necessary to replace all the gas in the guide channel 14 with gas outside the housing 12, the cleaning time Tc is determined by dividing the channel volume Vt of the guide channel 14 by the flow rate Qp per unit time in the pump 16 ( =Vt/Qp) or higher. For example, if the channel volume Vt is 200 ml and the flow rate Qp is 100 ml/min, the time Tc is 2 minutes or more, and in order to perform more thorough cleaning, the time Tc is set to about 19 minutes, which is 9.5 times Set.

(b) in the figure shows the state during gas measurement. After sensor cleaning is completed, perform gas measurement. First, the valve 22 is switched to a state of communication with the inside of the housing 12, and the pump 16 is driven. As a result, the gas in the housing 12 is guided by the guide channel 14 to the semiconductor gas sensor 13 and adheres to the surface of the sensor resistor 32, whereby the concentration of the target gas is detected. During the gas measurement time Ts, it is necessary to replace the gas in the guide channel 14 with the gas in the housing 12. Therefore, the value obtained by dividing the smaller of the channel volume Vt of the guide channel 14 and the volume Vh in which gas can enter in the housing 12 by the flow rate Qp per unit time in the pump 16 (=min[Vt, Vh ]/Qp) or higher. For example, if the channel volume Vt is 200 ml, the volume Vh inside the housing 12 is 100 ml, and the flow rate Qp is 100 ml/min, the gas measurement time Ts is 1 minute or more.
The above cleaning and gas measurement are set as one set, and this is carried out at every predetermined time Ti. The time Ti is, for example, about several tens of minutes to one day, but if the lubricant deteriorates, an abnormality occurs relatively quickly, so it is preferably within 24 hours.

《Effect》
Next, the main effects of the embodiment will be explained.
A constant potential electrolysis type gas sensor measures the concentration of a target gas by electrolyzing the target gas at a specific potential and detecting the electrolytic current generated at that time. This potentiostatic electrolytic gas sensor may not have sufficient detection sensitivity or may not be able to detect deterioration with some lubricants due to gas selectivity, so there is room for improvement. Ta. Therefore, in the lubricant deterioration state detection device 11 of the present embodiment, the semiconductor gas sensor 13 detects target gas generated due to deterioration of the lubricant lubricating the rolling bearing 15. The semiconductor gas sensor 13 has the following advantages over a constant potential electrolysis type.

First, since the semiconductor gas sensor 13 is heated to about 200 to 500° C. by the heater resistor 31, even if moisture is present, it immediately evaporates, so it is not affected by moisture. Similarly, even if oil is present, it quickly vaporizes and is discharged from the guide channel 14, which prevents oil from adhering to or accumulating on the sensor resistor 32, thereby extending its life. On the other hand, constant potential electrolytic gas sensors do not have a heater, so they may be affected by moisture, the detection accuracy may decrease due to oil adhesion or accumulation, or there is a possibility of erroneously detecting oil as a target gas. .

In addition, the semiconductor type gas sensor 13 is suitable for detecting deterioration of lubricants because the target gas types include alcohols, ketones, aldehydes, and organic acids, as well as all carbonyl compounds. Are better. On the other hand, constant potential electrolytic gas sensors cannot detect alcohols, ketones, organic acids, etc. with high accuracy.
Furthermore, since the semiconductor gas sensor 13 has high heat resistance, it can be used in high-temperature environments. On the other hand, constant potential electrolytic gas sensors do not have high heat resistance, so the temperature environments in which they can be used are limited.
Therefore, by detecting the target gas generated from the lubricant of the rolling bearing 15 using the semiconductor gas sensor 13, the detection sensitivity and gas selectivity when detecting the deterioration state of the lubricant can be improved.

In the lubricant deterioration state detection device 11, a filter 17 for removing oil mist is provided in the guide flow path 14. Thereby, after the oil mist is removed by the filter 17, the gas within the housing 12 can be guided to the semiconductor gas sensor 13. Therefore, it is possible to prevent oil from adhering to or accumulating on the sensor resistor 32, thereby extending its life.
In the lubricant deterioration state detection device 11, a valve 22 is provided in the guide flow path 14 to switch the gas guided to the semiconductor gas sensor 13 to either the gas inside the casing 12 or the gas outside the casing 12. There is. Thereby, it is possible to easily switch between performing sensor cleaning that guides gas outside the casing 12 or gas measurement that guides the gas inside the casing 12.

In the lubricant deterioration state detection method, the deterioration state of the lubricant is detected by detecting target gas generated due to deterioration of the lubricant lubricating the rolling bearing 15 with the semiconductor type gas sensor 13. Thereby, detection sensitivity and gas selectivity when detecting the deterioration state of the lubricant can be improved.
In the lubricant deterioration state detection method, the gas in the casing 12 housing the rolling bearing 15 is guided to the semiconductor gas sensor 13 through the guide channel 14, and the concentration of the target gas is detected, thereby detecting the deterioration state of the lubricant. is being detected. Thereby, the detection sensitivity when detecting the deterioration state of the lubricant can be improved.

In the lubricant deterioration state detection method, before the gas in the housing 12 is guided to the semiconductor gas sensor 13, the semiconductor gas sensor 13 is cleaned for a cleaning time Tc. That is, the valve 22 provided in the guide channel 14 switches the state of communication with the inside of the housing 12 to the state of communication with the outside of the housing 12, and the pump 16 is used to pump the gas outside the housing 12 to the semiconductor gas sensor 13. I will guide you to. As a result, even if the semiconductor gas sensor 13 is operated for a long period of time, it is possible to prevent the semiconductor gas sensor 13 from being contaminated and the detection sensitivity from decreasing, and to extend the life of the semiconductor gas sensor 13.

In the lubricant deterioration state detection method, the cleaning time Tc is set to be greater than or equal to the value obtained by dividing the channel volume Vt of the guide channel 14 by the flow rate Qp per unit time in the pump 16 (=Vt/Qp). Thereby, the gas in the guide channel 14 can be replaced and sufficient cleaning can be performed.
In the lubricant deterioration state detection method, the target gas contains at least one of alcohol, ketone, aldehyde, and organic acid, and the concentration of these gases is selectively detected. In this way, all carbonyl compounds can be detected, making it suitable for detecting deterioration of lubricants.

"Example"
Next, an example of the lubricant deterioration state detection device 11 will be described.
In the example, a rolling bearing is used that has an inner diameter of 25 mm, an outer diameter of 62 mm, and a width of 17 mm, has an inner ring that rotates, and is lubricated with grease. It was continuously rotated under the conditions that the rotational speed was 10,000 r/min, the outer ring temperature was 140° C., the radial load was 98N, and the axial load was 1470N.

As a grease, the thickener is lithium soap, the consistency is No. 2, the base oil is a mixture of polyα-olefin and diester, and the kinematic viscosity is 15.9 mm ² /s (40 ° C.). Using grease. A sampling hole with a diameter of 6.5 mm is opened in the axial direction of the housing 12, a tube with an outer diameter of 6 mm and an inner diameter of 4 mm is inserted, and the gas inside the housing 12 is sucked. A ceramic filter was installed between the sampling hole and the sensor to remove oil mist. A semiconductor gas sensor is used as the sensor, and a reducing gas removes oxygen from the surface of the metal oxide, and detects the decrease in resistance that occurs depending on the gas concentration. In addition, the outer ring temperature was measured.

The deterioration state of the lubricant in the rolling bearing was detected by operating the sensor unit at the same time as rotation started and intermittently measuring the detected gas concentration. The gas suction route was switched using a valve, and sensor cleaning for 19 minutes and gas measurement for 1 minute were repeated.
FIG. 4 is a graph showing test results of Examples.
(a) in the figure shows the outer ring temperature, and (b) in the figure shows the sensor output. The test results showed that the sensor output increased after 350 hours had passed, and when 380 hours had passed, an abnormal rise in the outer ring temperature was detected and the test machine stopped. After testing, the lubricant in the rolling bearing had deteriorated, making it difficult to rotate smoothly. Therefore, if the threshold value Eth for the sensor output is set to about 0.2 to 0.3V, for example, and the test machine is stopped when the sensor output exceeds the threshold value Eth, the outer ring temperature can be prevented from rising abnormally. In other words, the test machine can be stopped before the lubricant deteriorates. Note that since the sensor output peaks at the beginning of rotation, this period is considered a dead zone.

Next, a comparative example will be explained. In the comparative example, gas measurement was performed using a constant potential electrolytic sensor under the same conditions as in the example.
FIG. 5 is a graph showing test results of comparative examples.
(a) in the figure shows the outer ring temperature, and (b) in the figure shows the sensor output. The test results showed that the sensor output did not increase before the outer ring temperature rose abnormally. In other words, the deterioration of the lubricant progressed before the sensor output increased, causing the outer ring temperature to rise abnormally.
Therefore, it was confirmed that the example was superior to the comparative example in terms of detection sensitivity when detecting the state of deterioration of the lubricant.

《Modified example》
In the embodiment, a configuration including one casing 12 has been described, but the present invention is not limited to this, and a configuration including a plurality of casings 12 may be used.
FIG. 6 is a diagram showing a modification.
Here, a configuration including two housings 12a and 12b is shown. In this case, a valve 42 (second flow path switching section) is provided to switch the gas guided to the semiconductor gas sensor 13 to the gas in one of the housings 12 of the plurality of housings 12a and 12b. Note that in each route, the guide channel 14, rolling bearing 15, and filter 17 have the same configuration, and therefore are given the same reference numerals and detailed explanations will be omitted. The valve 42 also has the function of switching the gas guided to the semiconductor gas sensor 13 to either the gas inside the housing 12 or the gas outside the housing 12 (the first flow path switching section, the flow route switching section). That is, the valve 42 is a valve that switches the gas guided to the semiconductor gas sensor 13 to any one of the gas inside the housing 12a, the gas inside the housing 12b, and the gas outside the housing 12.

When performing gas measurement on the housing 12a, the gas inside the housing 12a is guided to the semiconductor gas sensor 13 after sensor cleaning is performed. Furthermore, when performing gas measurement on the housing 12b, the gas inside the housing 12b is guided to the semiconductor gas sensor 13 after sensor cleaning is performed. In this way, even if a plurality of casings 12 are provided, by switching the flow paths using the valve 42, gas measurement in the casings 12a and 12b can be performed using one semiconductor gas sensor 13. That is, the semiconductor gas sensor 13 can be shared by a plurality of housings 12, and an increase in the number of parts and cost can be suppressed.

Note that one valve 42 has the function of switching to either the gas inside the casing 12 or the gas outside the casing 12, and the function of switching to the gas inside the casing 12 of one of the casings 12a and 12b. Although it has both functions, it is not limited to this. The above-mentioned valve 22 may be used to switch between the gas inside the casing 12 and the gas outside the casing 12, and the other valve 42 may be used to switch to either one of the casings 12a and 12b. Further, although the two casings 12a and 12b are provided, the present invention is not limited to this, and can also be applied to a configuration including three or more casings 12.

Although the embodiments have been described above with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art.

DESCRIPTION OF SYMBOLS 11... Lubricant deterioration state detection device, 12... Housing, 12a... Housing, 12b... Housing, 13... Semiconductor type gas sensor, 14... Guide channel, 15... Bearing, 16... Pump, 17... Filter, 21... Branch flow path, 22...Valve, 23...Filter, 31...Heater resistance, 32...Sensor resistance, 33...Load resistance, 42...Valve

Claims (4)

A housing housing a rotatable rolling bearing;
a semiconductor gas sensor that is placed outside the housing and detects the concentration of the target gas;
a guide flow path that communicates within the housing and guides gas within the housing to the semiconductor gas sensor;
Detecting the deterioration state of the lubricant of the rolling bearing according to the detection result of the semiconductor gas sensor ,
The guide channel is
A filter that removes oil mist contained in the gas,
a first flow path switching unit that switches the gas guided to the semiconductor gas sensor to either the gas inside the housing or the gas outside the housing;
A second flow path switching unit that switches the gas guided to the semiconductor gas sensor to the gas in one of the plurality of casings. Device. Before guiding the gas inside the casing to the semiconductor gas sensor, the first flow path switching section switches from a state of communication with the inside of the casing to a state of communication with the outside of the casing for a predetermined cleaning time. 2. The lubricant deterioration state detection device according to claim 1, wherein the semiconductor gas sensor is cleaned by guiding gas outside the housing to the semiconductor gas sensor using a pump. 3. The lubricant deterioration state detection device according to claim 2, wherein the cleaning time is set to a value equal to or greater than a value obtained by dividing the flow path volume of the guide flow path by the flow rate per unit time in the pump. The lubricant deterioration state detection device according to claim 1, wherein the target gas contains at least one of alcohol, ketone, aldehyde, and organic acid, and the concentration of these is selectively detected.

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