Method and system for lubricating one or more rotating bearings

Abstract

According to the method of the invention, the rotating bearing (1) is supplied with lubricant progressively while it is in operation, i.e. rotating at a given rotational speed. The lubricant is supplied in a succession of successive steps, so that at each step a sub-portion of the prescribed quantity of lubricant is supplied to the bearing, each time followed by an ultrasonic measurement. A first ultrasonic measurement is performed before the first supply step, and from the second supply step, each measurement result is compared at least with the previous result to assess the bearing condition and decide, on the basis of this assessment, whether to continue the sequence or to stop the sequence. The decision to stop the sequence is taken when the lubrication of the bearing is assessed as successful lubrication, failed lubrication or over-lubrication. The invention also relates to a system for lubricating one or more bearings, whereby the method of the invention is applied to each of said bearings.

Description

Technical Field

[0001] This invention relates to the monitoring and lubrication of rotating bearings used in rotating machinery. Background Technology

[0002] Bearings equip most industrial assets and have consistently been a leading cause of damage that can affect the operation of rotating equipment. Unexpected bearing failure causes unintended production interruptions, leading to unintended losses that increase costs and involve unplanned downtime. One of the main root causes of failure is the abnormal wear and deterioration of moving parts, caused by lubrication-related problems. Bearings provide the mechanical connection that guides rotating parts while supporting and transmitting forces with minimal friction. The evolution of vibration processes, acoustic, thermal, or electrical monitoring technologies to ensure or even extend the predefined service life of equipment while keeping pace with production costs has not yet solved the real problem of lubrication management.

[0003] The main causes of bearing failure are lack of lubricant, over-renewal of lubricant due to inappropriate cycles and / or amounts, and contamination. Therefore, maintaining optimal lubrication is crucial to increase reliability and limit failures.

[0004] Empirical studies have yielded general formulas for establishing lubrication procedures. Currently, the strategy of periodically lubricating bearings is common practice. It is generally believed that 30% of the clearance in a bearing must be filled with lubricant to optimize bearing operation. Manufacturers have developed empirical methods to calculate the amount of lubricant to be periodically injected and the relubrication interval.

[0005] For example, to calculate the amount of grease needed in a bearing, the bearing's geometry and a predetermined method are required. Bearing manufacturer SKF specifies the following:

[0006] • If relubrication is performed from the side of the bearing, the replenishment amount G = 0.005 dB.

[0007] • If relubrication is performed through a hole in the center of the inner or outer ring, then G = 0.002 dB.

[0008] Where G is the amount of grease to be added when replenishing the bearing (in grams), D is the outer diameter of the bearing (in millimeters), and B is the width of the bearing (in millimeters). This formula is widely considered the best method for calculating the amount of grease.

[0009] Once the required amount of grease has been calculated, it is necessary to determine how often to apply that amount of grease. The relubrication interval is defined as the grease refill frequency. Calculations require the machine's operating conditions and additional bearing information. The preferred method for determining the grease refill frequency is as follows:

[0010]

[0011] Where T is the time interval between two grease-applying operations (in hours), N is the rotational speed (in rpm), and d is the bearing bore diameter (in millimeters). K represents a correction factor, which is a function of operating conditions. K is the product of factors determined by temperature, contamination, humidity, vibration, location, and bearing design. The values ​​of these factors are available in the literature. Sensors are typically not required.

[0012] The evaluation of the {G, T} couple for each bearing enables the definition of a lubrication schedule. The proposed formulas are the result of empirical testing conducted by bearing manufacturers. It should be noted that these estimates may vary from manufacturer to manufacturer. In the field, when several (e.g., dozens, hundreds, or even thousands) bearings are periodically greased, the associated logic is considered a significant source of error. This can be improved through modern applications focused on traceability, such as those presented in US 2019 / 257360.

[0013] However, existing lubrication methods based on empirical formulas (as given above) have not provided satisfactory levels of lubrication. Lubrication procedures are often performed "blindly," meaning that the true needs of the lubricant are not quantified and personalized, as this requires physical measurements from sensors, followed by decision-making tools. In most cases, and possibly for erroneous safety reasons, grease application is performed prematurely, leading to over-lubrication (known as over-lubrication), which in turn causes harmful thermal and mechanical stresses on rotating equipment.

[0014] To overcome these limitations, automated and centralized relubrication is increasingly being employed. Automatic lubricators typically dispense measured and / or prescribed amounts of lubricant to bearings based on defined time intervals. This type of device offers interesting advantages in situations where locations are difficult to access or where equipment is operated remotely without local maintenance personnel. Some examples of automatic lubricators are given in documents EP 0 704 654 B1 and EP 0 806 602 A1. However, these systems do not include adequate verification of the results for the supplied lubricant. Lubricant may fail to reach the rolling interface due to blockages, leaks, or excess lubricant in the housing. The physical and / or tribological properties of the lubricant may also be compromised due to oxidation, contamination by impurity particles, or simply lubricant aging. Furthermore, different operating conditions or two identical bearings in different installations may have potentially different lubricant consumption.

[0015] Existing automatic lubrication devices equipped with pressure and / or temperature sensors are described in US 2012 / 145482 and EP 0 399 323 E1. The pressure sensors are intended to detect blockages or leaks along the grease lines. As previously described, these devices inject a predetermined amount (typically a constant amount) of grease at predefined intervals, regardless of actual demand. Other devices equipped with vibration sensors, tachometers, and / or other sensors are described in US10197044 A1, US9353908, and FR 3009057, where parameters extracted from analysis (i.e., vibration analysis) are intended to detect the lubrication condition of bearings in operation. These systems are based on vibration measurements typically performed at low frequencies [10 Hz, 1000 Hz]. The scalar results of this vibration measurement (often given in velocity units (typically RMS velocity)) consist of a combination of several vibration modes. These features are inherently more energetic than those affecting bearing friction, thus masking the evolution of the lubrication condition and its potential consequences. Therefore, these systems often fail to detect specific bearing lubrication-related problems. DE 102013100988 and US 2003 / 0047386 disclose other lubricator systems that quantify the lubricant film thickness during operation based on ultrasonic echo resonance methods or on changes in the electrical properties of the lubricant. Due to the high variability of applications, this method requires complex setups, calibration procedures (which assume values ​​as targets to achieve satisfactory optimal lubricant conditions), and potential modifications, which may limit the scalability of the overall lubrication system.

[0016] More successful lubrication monitoring systems (such as auxiliary lubrication systems) are based on ultrasonic measurements. Handheld ultrasonic lubrication condition monitors are well known in the art, and the applicant has developed a series of such devices. These devices include piezoelectric transducers (e.g., in the range of 20 kHz–100 kHz (ultrasonic domain)) mounted on a resonant structure. When the piezoelectric transducer is mounted in contact with a rotating bearing to measure the vibrational or acoustic response generated by the bearing, it exhibits high sensitivity in the relevant ultrasonic domain suitable for lubrication. Excitation at the resonant frequency enables the detection of high-frequency phenomena related to lubrication conditions, such as rolling friction and defect impacts. A real-time auditory rendering derived from heterodyne transformation is typically provided as a subjective and passive decision-making tool, where the user retains the decision to add an unknown amount of lubricant. To improve objectivity and repeatability, signal processing chains implemented in the aforementioned handheld devices and used to process (i.e., acquire and filter) the signals generated by the transducers are also well known in the prior art. These processing methods are primarily configured to extract multiple scalar parameters related to a specific bearing condition from the ultrasonic signal. Filters are applied to improve sensitivity based on the transducer's response. The most important indicator is the root mean square (RMS) of the ultrasound signal, expressed in decibels (dB).

[0017] For N samples x that are regularly spaced out in time (i.e., acquired) k The time signal x(t) is constructed, and its RMS value is defined according to the initial settings and the embedded electronic device:

[0018] Convert to

[0019] 1 μV is used as a reference. Summary of the Invention

[0020] The object of this invention is to provide a solution to the aforementioned problems. This object is achieved by the method and system according to the appended claims. According to the method of the invention, a lubricant is supplied to a rotating bearing progressively while it is operating, i.e., rotating at a given rotational speed. The lubricant is supplied in a series of consecutive steps, such that a predetermined amount of lubricant is supplied to the bearing in each step, followed by ultrasonic measurement. A first ultrasonic measurement is performed before the first supply step, and starting from the second supply step, each measurement result is compared at least with the previous result to assess the bearing condition and, based on this assessment, to determine whether to continue the sequence or stop the sequence. According to a preferred embodiment, the sequence is stopped when the lubrication of the bearing is assessed as successful lubrication, unsuccessful lubrication, or over-lubrication. In other words, the invention provides a method for monitoring and self-regulating (i.e., self-adjusting) lubrication supply (expressed as the amount of lubricant to be injected). The invention also relates to a system for lubricating one or more bearings, thereby applying the method of the invention to each of said bearings.

[0021] The present invention specifically relates to a method for monitoring and lubricating at least one rotating bearing of a machine, the method being carried out by progressively supplying lubricant to the bearing in one or more consecutive supply steps, wherein:

[0022] - Determine the specified lubrication dosage (G),

[0023] - Prior to the first supply step, an ultrasonic signal is measured using a transducer installed to connect to the bearing, and an initial value (M0) of a scalar index representing the (initial) lubrication condition of the bearing is extracted from the signal. This measurement and value extraction are repeated after each subsequent lubricant supply step, wherein each measurement is performed after a stabilization period following supply, the duration of which allows for full operation of the supplied lubricant.

[0024] - The amount of lubricant supplied in these successive steps (gn) is less than the specified lubricant dosage (G).

[0025] -Evaluate each value (Mn) of the scalar index relative to the initial value (M0) starting from the second extracted value (M1) and relative to one or more of the previously extracted values ​​(M1, M2, ..., Mn-1) starting from the third measurement.

[0026] - The decision to stop or continue the lubrication sequence is based on each of these assessments.

[0027] Preferably, the decision on whether to stop or continue the lubrication sequence is an automatic decision.

[0028] According to one embodiment, a predetermined lubrication dose (G) is used as a default value to initialize the method. According to another embodiment, the predetermined lubrication dose (G) can be adjusted sequentially based on ultrasonic measurements performed between each step. The predetermined lubrication dose can be increased or decreased based on successive measurements. For example, over time, the rotating bearing may require a higher amount of lubricant due to abnormal friction levels revealed by ultrasonic measurements (e.g., caused by abnormal use, abnormal completion, or leakage through seals or pipes). The predetermined lubrication dose can then be increased to ensure a higher amount of lubricant is supplied to the rotating bearing, wherein the lubricant is supplied according to the invention.

[0029] According to an embodiment, the scalar index is the root mean square (RMS) of the signal.

[0030] According to an embodiment, the sequence continues when the extracted RMS value is significantly lower than the previously extracted value. In this context, "significantly lower" or "significantly higher" preferably means that the RMS is at least 1 dB lower or higher. In this context, "substantially the same as the previous value" preferably means that the RMS is in the range of -1 dB to +1 dB compared to the previous value (including or excluding these values).

[0031] According to an embodiment, the sequence continues when the extracted value is substantially the same as the previously extracted value, unless the value extracted remains unchanged over a given number of consecutive measurements and value extractions, in which case the sequence is stopped and the lubrication condition is considered successful.

[0032] According to an embodiment, the sequence is stopped when the extracted value is higher than the initial value (M0) to avoid over-lubrication. Over-lubrication, or an over-lubricated state, typically occurs during the first few steps of the sequence. Therefore, the amount of lubricant delivered to at least one rotating bearing at the moment over-lubrication is detected is typically less than a predetermined lubrication dose (G).

[0033] According to an embodiment, after a previous value that is significantly lower than the previous value, when the extracted value is significantly higher than the previous value, the sequence is stopped due to successful lubrication.

[0034] According to an embodiment, after a previous value is substantially the same as the value preceding that previous value, the sequence is stopped due to a failed lubrication condition when the extracted value is significantly higher than the previous value.

[0035] According to an embodiment, the method further includes: performing an intermediate measurement of the ultrasonic signal during a stabilization time after the first lubricant supply step and before the first extraction of the scalar index value (M1), and extracting the value of the scalar index (M') from the intermediate signal, wherein if the value M' is significantly lower than the initial value (M0) and the first extracted value (M1) is significantly higher than the intermediate extracted value (M'), the sequence is stopped due to suspected bearing failure.

[0036] According to an embodiment, the scalar or additional scalar indicator is kurtosis.

[0037] The method may further include: determining a supplementary interval (T), wherein the method according to the invention is performed multiple times at intervals equal to or shorter than the supplementary interval. Preferably, the supplementary interval (T) is an optimal supplementary interval.

[0038] According to an embodiment, a supplementary interval is updated between subsequent applications of the lubrication method according to the invention, wherein the update is based on the results of the steps of the lubrication method.

[0039] According to an embodiment, when it is determined that a higher total amount of lubricant than the specified amount (G) is needed before stopping the lubrication sequence, a shorter replenishment interval is applied.

[0040] According to the embodiments, the method is fully automatic.

[0041] The present invention also relates to a system for supplying lubricant to at least one rotating bearing, the system comprising:

[0042] - A lubricant supply reservoir, which is equipped with a flow control device for controlling the flow rate of lubricant from the reservoir.

[0043] - At least one pipe for supplying lubricant from a reservoir to at least one rotating bearing.

[0044] - At least one transducer, the at least one transducer being adapted to measure ultrasonic signals when the transducer is mounted in connection with a rotating bearing.

[0045] - A signal processing unit, which is connected to at least one transducer and to a flow control device, and is configured to...

[0046] ο Calculate and store the values ​​of scalar indices representing the lubrication condition of the bearing.

[0047] The flow from the reservoir to the bearing is actuated or stopped according to the method of the invention based on an assessment of this value.

[0048] It transmits information about lubrication status and / or bearing status to the system's users.

[0049] Advantageously, the system includes at least one rotary bearing. Advantageously, the system of the present invention includes a sensor comprising at least one transducer. Preferably, the transducer designates the sensitive element of the sensor. Advantageously, the sensor is adapted to measure ultrasonic signals. Preferably, the sensor is mounted to be connected to the rotary bearing.

[0050] Advantageously, the system is a system for self-regulating (i.e., self-adjusting) lubricant supply to at least one rotating bearing. Preferably, the system is capable of self-regulating lubricant supply to at least one rotating bearing. Advantageously, the system is capable of performing the method of the invention.

[0051] Advantageously, the signal processing unit (6) is further configured to acquire, filter, and process the ultrasonic signal within a defined frequency range. Preferably, the ultrasonic signal is acquired, filtered, and processed before calculating and storing the value of a scalar index representing the lubrication condition of the bearing.

[0052] Preferably, the flow rate from the reservoir to the bearing is adjusted to a continuous amount (gn) of lubricant based on the ultrasonic value.

[0053] Preferably, the transmitted information includes data and status of lubrication conditions and / or bearing conditions. Preferably, the information is transmitted to the software system and / or the system user.

[0054] The system of this invention can operate without human assistance while maintaining the traceability of automated decision-making. The use of relevant scalar indicators allows for the substitution of human decision-making. The use of relevant scalar indicators further allows the system to appropriately self-regulate the amount of lubricant supplied to at least one rotating bearing. To this end, the system includes a regulating loop that includes a two-way interactive exchange between lubricant flow control and ultrasonic results.

[0055] According to an embodiment, the system is configured to operate automatically. Attached Figure Description

[0056] Figure 1a and Figure 1b A system for supplying lubricant to bearings and performing ultrasonic measurements of the bearing's lubrication condition is demonstrated.

[0057] Figure 2 It is a general image of the shape of the Stribeck curve for non-conformal contact, representing different lubrication states of the bearing.

[0058] Figure 3 This is a flowchart of the initial sequence of the method of the present invention according to an embodiment of the method.

[0059] Figures 4a to 4d It is based on Figure 3 Examples of converting multiple possible sequences of the flowchart into measured RMS values ​​in dBμV.

[0060] Figure 5a and Figure 5b yes Figure 3 The flowchart follows the diagram.

[0061] Figures 6a to 6e It is based on Figure 5a Examples of measured RMS values ​​in multiple possible sequences of the flowchart.

[0062] Figures 7a to 7d It is based on Figure 5b Examples of measured RMS values ​​in multiple possible sequences of the flowchart.

[0063] Figure 8a and Figure 8b This is a general flowchart of the nth step in a series of method steps applicable to this invention. Detailed Implementation

[0064] According to a preferred embodiment, the method of the present invention is repeatedly performed during active service periods of a machine comprising one or more rotating bearings, the method being applied to each of said bearings. For a bearing having a given size and rotating at a given speed, the interval T between required lubricant replenishments can be calculated according to existing methods, preferably by formula (1) given above. Similarly, the prescribed amount G of lubricant to be supplied at each replenishment is calculated in a manner known as and mentioned above. However, instead of supplying sufficient G, the method of the present invention provides a stepwise supply of sub-parts of G, which is monitored by continuous ultrasonic measurements configured to determine the effect of each sub-part on the bearing condition. Thus, the method of the present invention allows for self-adjustment of the actual required amount of lubricant according to the prescribed amount (G) of lubricant.

[0065] The method of the present invention preferably utilizes the "intelligent" automatic lubrication system according to the present invention (e.g., Figure 1a and Figure 1b (As shown) it is executed automatically. Figure 1a A rotary bearing 1 is schematically shown supporting a rotatable shaft 2 of a machine 3. A system 4 is configured to supply lubricant (e.g., grease of a given viscosity) to the bearing and is used to perform and evaluate ultrasonic measurements. Figure 1bThe components of system 4 are shown: a piezoelectric transducer 5 suitable for performing ultrasonic measurements, a signal processing unit 6, and a lubricant supply reservoir 7, which is provided with a flow control mechanism 8 for regulating the flow rate from the reservoir 7 through the supply pipe 9 into the bearing. The signal processing unit 6 is configured to extract one or more scalar indicators (e.g., RMS values) representing the lubrication condition of the bearing from the ultrasonic signal generated by the transducer 5. The electronic signal processing components present in the processing unit 6 can be consistent with known designs, such as those implemented in handheld ultrasonic lubrication monitors as part of the prior art. Furthermore, the signal processing unit 6 is configured to evaluate measurements and control the supply step sequence according to the method of the invention. Unit 6 is also configured to transmit data about the bearing and / or lubrication condition to the user of the system, for example, by displaying messages on a screen (not shown). The system according to the invention can be configured to lubricate several bearings placed at different locations on one or more machines. A single processing unit can be configured to monitor the lubrication condition of multiple bearings and control the lubricant flow rate from a single reservoir to multiple bearing locations. The flow control mechanism may include a pump for directing the lubricant flow to the bearing locations. The system may include multiple transducers, some or all of which may be permanently mounted in the bearing location.

[0066] Unlike existing methods that require target lubricant values ​​over specified periods, the method of this invention uses algorithmic convergence. Algorithmic convergence produces a supplementary process that is executed incrementally through a self-regulating loop. Therefore, the amount of lubricant supplied to the rotating bearing is determined by direct measurement to establish the optimal amount of lubricant, whereas existing methods often rely on indirect measurements (such as lubricant film thickness) or human decision-making.

[0067] The lubricant supply sequence according to the present invention is equivalent to a decision tree algorithm rooted in the Stribek curve, well-known in the field of tribology. A schematic diagram of the general appearance of the Stribek curve for conformal contact is shown in... Figure 2 The Stribek curve for conformal contact has a similar general shape, and the present invention is applicable to bearings in which conformal or non-conformal contact occurs. The curve shows the coefficient of friction as a dimensionless lubrication-related scalar parameter (i.e., a scalar parameter that increases when more lubricant is present on the contact surfaces, preferably at the interface between the contact surfaces in a bearing). This can be, for example, a specific dimensionless film thickness (λ), which expresses the ratio between the thickness of the lubricant film between the contact surfaces within the bearing and the roughness of the contact surfaces. The coefficient of friction is a function of the frictional forces affecting the bearing (e.g., the frictional forces between the balls of a ball bearing and the rolling surfaces of the inner and outer rings of the bearing). The Stribek curve is characterized by being composed of... Figure 2 The numbers I, II, III, and IV indicate the appearance of the four operating areas:

[0068] I: Boundary lubrication: Solid surfaces are in direct contact, and the load is mainly supported by the surface roughness (metal-to-metal contact), resulting in high friction. This region is typical for bearings with severe underlubrication.

[0069] II: Mixed Lubrication: Some roughness contacts appear; the load is supported by both the roughness and the viscous lubricant, resulting in significant frictional variability. This region characterizes the behavior when lubricant is supplied to an under-lubricated bearing: as lubricant is added (from left to right along the curve), the roughness is gradually covered by the lubricant, and the coefficient of friction decreases rapidly with increasing lubricant film thickness.

[0070] III: Fluid lubrication of elastohydrodynamic (EHD) films, characterized by their optimal state.

[0071] IV: Fluid lubrication under hydrodynamic conditions (full film-HD).

[0072] Regions III and IV are characterized by negligible roughness in the contact area; the load is primarily supported by the lubricant due to lift, pressure, and the physical properties of the lubricant. The coefficient of friction is low in the EHD region but gradually increases in the HD region according to the film thickness / roughness ratio. The EHD region is considered the ideal operating condition for the bearing. Figure 2 The graph shown is merely an example of a Stribek curve. The details can vary for each bearing. For instance, the rate of change of the coefficient of friction in the EHD and HD regions can differ. Figure 2 The curve shown.

[0073] The relubrication interval T is calculated as described in the previous paragraph and depends on empirically determined factors such as temperature, humidity, and bearing contamination. The replenishment amount G is also determined based on empirical formulas. However, the actual lubricant requirements of a bearing can never be accurately estimated by these two empirical values ​​T and G in all cases, but may be affected by factors that vary over time or are typical for the specific construction details of the machinery in which the bearing is installed. For this reason, in some cases, supplying G at intervals T may result in insufficient or excessive lubrication of the bearing, or may prevent the detection of a faulty bearing.

[0074] This invention addresses this problem by supplying the lubricant in a gradual manner, rather than a one-time, full-volume supply of G, preferably with a self-adjusting amount of lubricant, accompanied by ultrasonic measurements to verify the effectiveness of continuous lubricant addition. Several ultrasonic-based scalars (particularly RMS) represent the frictional behavior of the bearing, as expressed by the Strickelbeck curve. Therefore, the inventors have discovered that, for bearings assuming correct operation and requiring lubrication replenishment, the method of this invention allows for the supply of lubricant from left to right, following the Strickelbeck curve, until a point is reached where the bearing is operating in the EHD state or in a lower region of the HD state. Furthermore, specific embodiments of this method allow for the detection of suspected bearing failure, lubrication failure, or over-lubrication by detecting behavior that deviates unacceptably from the Strickelbeck curve. The method of this invention does not require precise knowledge of the Strickelbeck curve of the bearing to which the method is applied, but rather applies decision logic based on general trends observable in any Strickelbeck curve (e.g., a downward trend in region II, followed by an upward trend in regions III and IV). When overlubrication is detected, the prescribed lubrication dose (G) can be automatically adjusted (in this case, reduced) to avoid overlubrication in the next sequence. Alternatively or additionally, when overlubrication is detected, the initial time interval (T) can be automatically increased.

[0075] Preferred embodiments of the decision tree algorithm according to the present invention are described in detail below. However, the following description does not limit the scope of this patent application. Figure 3 A flowchart is shown, which illustrates the use of Figure 1a and Figure 1b The illustrated facility performs the initial steps of the method according to a preferred embodiment on a rotating bearing. For the bearing in question, parameters T and G are determined. The start time of the sequence does not exceed T seconds after the bearing has been previously replenished with lubricant. The sequence can begin T seconds after the last replenishment (e.g., at a ratio of 0.5T or 0.7T). This can be determined when defining the initial settings for the application method. The ratio of T can also be varied during the bearing's lifespan as a result of the sequence applied according to the invention. Additionally, the initial settings for the application method can be adjusted using the system's data storage.

[0076] The sequence begins with an initial ultrasonic measurement, which yields an RMS value M0 measured in voltage units and expressed in dB (μV, where the reference voltage V0 is 1μV). M0 is stored in a memory incorporated into or connected to the processing unit 6. Then, a lubricant amount g1 equal to 0.25g is supplied to the bearing via the supply pipe 9 by controlling the flow control mechanism 8. Preferably, the settling time is determined based on experience and scientific data, such that after this settling time, it is assumed that the added lubricant has fully acclimated within the bearing. The settling time can be calculated based on the bearing speed parameters, defined as follows: (in mm / min), where d and D are the inner and outer diameters of the bearing (in mm), and ω is the rotational speed of the bearing (in rpm):

[0077] <![CDATA[n ω (mm / min)]]> Settling time (s) ＝＜46000 18 ∈]4600,52000] 16 ∈]52000,58000] 14 ∈]58000,64000] 12 ∈]64000,70000] 10 ∈]70000,76000] 8 >76000 7

[0078] During the settling time, i.e., before reaching a stable operating state, an intermediate RMS value M' is measured. Preferably, the value M' is determined by calculating the RMS values ​​refreshed at short intervals (e.g., 250 ms) throughout the settling time. At the end of the settling time, the minimum value of the acquired RMS values ​​is stored in memory to be used as the value M' in the decision tree algorithm.

[0079] Then, at the instant after the settling time has elapsed or shortly thereafter, another RMS value M1 is measured, representing the lubrication condition of the stabilized bearing after adding g1. Then, the following differential scalar is calculated and stored:

[0080] Δ1=M0-M1

[0081] Δ'=M0-M'

[0082] Moreover, according to Figure 3 The flowchart is evaluated as follows:

[0083] If Δ'>3 & Δ'-Δ1>3, the bearing condition is assessed as faulty. This corresponds to a situation where M' is more than 3dB below M0 and M1 is more than 3dB below M1, meaning the RMS value drops by more than 3dB and then rises again by more than 3dB during the stabilization interval. In this case, the sequence is stopped and the bearing is inspected.

[0084] If Δ1 < -1, the bearing condition is rated as "over-lubricated": M1 is more than 1 dB higher than M0. Since the normal Stribeck tendency is downward with a thicker lubricant film, an upward tendency indicates that no additional grease is needed and the process should be stopped. After this, it is preferable to inspect the bearing.

[0085] If the condition is not assessed as "over-lubricated," the next verification step is to check if the condition "-1 ≤ Δ1 < 1" is met. If not, this means Δ1 ≥ 1, i.e., M1 is at least 1 dB lower than M0. In this case, the lubrication condition is considered improved, and another amount of lubricant can be added. If the condition "-1 ≤ Δ1 < 1" is met, this means that M1 is within the range of minus or plus 1 dB relative to M0, i.e., the lubrication condition has not significantly changed. The state is recorded as "no change," and the sequence continues until further lubricant is added.

[0086] Refer again Figure 3 The flowchart shows that after supplying g1, if the result is "improved lubrication" or "no change", an amount g2 equal to 0.15G is supplied to the bearing. After supplying g2, a stabilization interval is allowed to pass, and then another ultrasonic measurement M2 is acquired and stored. The subsequent evaluation of this ultrasonic measurement is as follows:

[0087] If Δ2(=M0-M2)<0, the bearing condition is rated as "over-lubricated". In other words, after the first value M1 is more than 1 dB lower than M0 or approximately equal to M0, when the RMS value M2 is higher than the initial RMS value M0, the bearing is rated as over-lubricated, the sequence is stopped, and preferably a bearing inspection is subsequently performed. This sequence is in Figure 4a It is displayed in the middle.

[0088] If the bearing is not over-lubricated, verify the following condition: "Δ2 - Δ1 < -1". If this condition is met, the lubrication condition is rated as "lubrication successful", and the sequence is stopped. In other words, after M1 is approximately equal to M0 or at least 1 dB below it, the lubrication condition is considered satisfactory when M2 (below M0) is more than 1 dB above M1. Record the condition "lubrication successful" and stop the sequence. This sequence is in Figure 4b It is displayed in the middle.

[0089] If "Δ2 - Δ1 < -1" is not satisfied, then the condition "-1 ≤ Δ2 - Δ1 < 1" is verified. If the latter condition is satisfied, i.e., M2 equals M1 or is within 1 dB above or below it, then the situation is again described as "no change," and further supply steps are performed. This sequence is in Figure 4c The process is shown in the diagram. If the condition -1 ≤ Δ2 - Δ1 < 1 is not met, i.e., M2 is more than 1 dB lower than M1, the lubrication condition is rated as "improved," and the sequence continues, in which g3 (=0.1G) is further supplied and M3 is obtained. This sequence is shown in the diagram. Figure 4d As shown in the diagram. Following subsequent lubricant supplies starting from g3, the evaluation differs depending on the results of previous steps, as explained below. For example, three consecutive instances of "no change" in the status will result in the procedure being stopped.

[0090] Figure 5a and Figure 5b The subsequent steps of the sequence are shown. The supply g3 = 0.1G, and a settling time is allowed to pass. Then, another RMS value M3 is obtained, and it is now evaluated based on the results of the previous steps. Figure 5a A flowchart is shown, which is applicable when g3 is added after the state "no change" following g2.

[0091] First, the condition "Δ3(=M0-M3)<0" is evaluated, i.e., is M3 higher than M0? If the answer is yes, the lubrication condition is rated as "over-lubricated," and the sequence is stopped, preferably followed by a bearing inspection. An example of this sequence is... Figure 6a The following is an example. If the answer is no, further verification is needed regarding the condition "Δ3-Δ2<-1", i.e., is M3 more than 1 dB higher than M2? If this is the case, i.e., the "no change" after g2 is immediately followed by an increase of more than 1 dB after g3, then the bearing lubrication condition is rated as "lubrication failure". An example of this sequence is shown in... Figure 6b The sequence is stopped, and the bearing is inspected. Qualitatively, this means that there is "no change" after the second supply g2, followed by a rise of more than 1 dB after the third supply, while M3 remains below M0, indicating abnormal bearing behavior. The rise in RMS suggests that the bearing may be operating too deep into the HD region IV of the Stricker curve at this point.

[0092] If "Δ3-Δ2<-1" is not true, then additional verification is performed regarding the condition "Δ3-Δ1<-1.5", i.e., is M3 (less than 1 dB below M0 and more than 1 dB above M2) more than 1.5 dB above M1? If so, the lubrication condition is rated as "failure", and the sequence is stopped. In other words, if "no change" after g2 is followed by an increase of more than 1.5 dB compared to M1, then the lubrication condition is "failure". An example of this sequence is in Figure 6c As shown in the image.

[0093] If "Δ3-Δ1<-1.5" is not true, meaning M3 is no more than 1.5 dB higher than M1 and no more than 1 dB higher than M2, then the condition "-1≤Δ3-Δ2<1" is evaluated. If this condition is true, meaning M3 is equal to M2 or within 1 dB above or below it, then the lubrication condition is evaluated as "no change". However, in this third stage, additional verification is performed to determine if this "no change" is the third consecutive "no change" condition already evaluated. If so, the bearing condition is found to be stable and acceptable, i.e., "lubrication successful" is entered, and the sequence is stopped. An example of this sequence is shown in... Figure 6dAs shown in the diagram. At this point, it can be assumed that the bearing has entered the EHD region, and that this EHD region exhibits a very low rate of change in the coefficient of friction. If not, that is, when M3 is more than 1 dB lower than M2 after "no change" following g2, the lubrication condition is rated as "improved," and another amount of g4 is supplied. This sequence is in... Figure 6e It is displayed in the middle.

[0094] Figure 5b A flowchart is shown, which is applicable when g3 is added after the "lubrication improved" condition.

[0095] First, and as Figure 5a As shown in the chart, the condition "Δ3(=M0-M3)<0" is evaluated, i.e., is M3 higher than M0? If the answer is yes, the bearing is considered over-lubricated, and the sequence is stopped, preferably followed by a bearing inspection. This sequence is in Figure 7a The following is an example of this sequence. If the answer is no, further verification is performed regarding the condition "Δ3-Δ2<-1", i.e., is M3 more than 1 dB higher than M2? If this is the case, i.e., if the "lubrication improved" condition after g2 (M2 is more than 1 dB lower than M1) is followed by an increase of more than 1 dB (M3 is more than 1 dB higher than M2), then the lubrication condition is rated as "lubrication successful", and the sequence is stopped. An example of this sequence is shown in [link to example]. Figure 7b This is shown in the diagram. Qualitatively, this means the bearing has entered an EHD state, which is determined by the initial downward trend followed by an upward trend in the previous step.

[0096] If "Δ3-Δ2<-1" is not true, i.e., M3 is no more than 1 dB higher than M2, then the condition "-1≤Δ3-Δ2<1" is evaluated. If this condition is true, i.e., M3 is equal to M2 or within 1 dB above or below it, then the lubrication condition is evaluated as "no change". Considering the fact that the previous condition was "lubrication improved", "no change" is not a third consecutive "no change" condition. In this case, further supply step g4 is performed. An example of this sequence is in Figure 7c As shown in the diagram. If not, that is, when M3 is more than 1 dB lower than M2 after "lubrication is improved" following g2, the lubrication condition is rated as "improved," and another amount of g4 is supplied. An example of this sequence is shown in... Figure 7d As shown in the image.

[0097] Can Figure 5a and Figure 5b The sequence shown is generalized to obtain Figure 8a and Figure 8b The flowcharts shown describe the evaluation of measurement Mn based on the results of measurement Mn-1 (n≥3).

[0098] Decision tree algorithms always converge to a given final state, i.e., "lubrication successful," "lubrication failed," or "over-lubrication." (See details...) Figures 4a to 4d , Figures 6a to 6e and Figures 7a to 7d The graphs clearly show that when n≥3, successful lubrication is associated with the stabilization of RMS after three consecutive supplies, or with a significant increase in RMS after a previous significant decrease. These conditions reflect the Stricker curves when the bearing is in EHD (Extended High Distance) or when the bearing enters EHD after a downward trend in RMS under mixed lubrication conditions, respectively. The graphs indicating lubrication failure are associated with an increase in RMS after a previous stabilization, indicating that the bearing is entering the HD region, which is undesirable for optimal bearing operation.

[0099] Therefore, compared to supplying a full amount of G, supplying lubricant gradually allows for a more detailed assessment of bearing condition, making lubrication failures more effectively detectable.

[0100] As described above, the algorithm is merely one example of a possible decision tree algorithm, and many details may vary with respect to the above sequence. For example, sub-parts g1, g2, etc., may represent higher or lower percentages of quantity G, or the supply may differ as a function of n in a predefined manner.

[0101] It is not necessary to include all verification steps. For example, the additional verification for Δn - Δn - 2 < -1.5 can be omitted. Similarly, the intermediate measurement M' can be omitted.

[0102] Before initiating the sequence or the remainder of the sequence, additional verification of the absolute levels of M0, and preferably M1 as well, can be performed. If M0 or M1 exceeds a specific safety range near a predefined absolute level, an alarm can be issued.

[0103] When n≥3, the lubrication dosages g1 = 0.25G, g2 = 0.15G, and gn = 0.1G represent a preferred sequence suitable for most lubricants (such as greases supplied to rolling bearings). However, other G ratios can be applied within the scope of this invention. In most cases, the method converges to a "lubrication successful" or "failure / overlubrication" state before the sum of the supplied amounts reaches G. However, it is also possible that the sum of the supplied amounts exceeds G, indicating that the estimate of G is too conservative. According to an embodiment, when it is determined that the method has not converged when n≥9, the supplemental interval T is shortened.

[0104] In addition to RMS, other lubrication-related scalar indicators, such as x, can be used in the method of this invention to enhance decision-making. K Kurtosis, which is defined as:

[0105]

[0106] The precise criteria used to assess this scalar indicator at each step can be different from those used for RMS assessment.

[0107] As described above, the method of the present invention is particularly suitable for application in a fully automated manner using the intelligent automated lubrication system according to the present invention. This can be as follows: Figure 2 The system demonstrated includes a processing unit 6 configured to automatically execute the steps of a method, namely, running a decision tree algorithm and performing replenishment in a stepwise manner until a state of "over-lubrication," "lubrication success," or "lubrication failure" is reached. In the first and third cases, the system can generate signals or messages to inspect or repair the bearings. The system is configured to perform multiple replenishments at predefined intervals (e.g., T seconds or less). The system can also automatically recalculate the T interval based on the results of the decision tree algorithm. The system may include multiple transducers permanently mounted to contact multiple bearings.

[0108] Although the invention has been shown and described in detail in the accompanying drawings and the foregoing description, such showing and description is to be regarded as illustrative or exemplary rather than restrictive. Other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in practicing the claimed invention from a study of the drawings, this disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a / an" or "an" do not exclude a plural. The mere fact that specific measures are recited in mutually different dependent claims does not indicate that combinations of these measures cannot be used advantageously. No reference numerals in the claims should be construed as limiting the scope.

Claims

1. A method for monitoring and lubricating at least one rotating bearing (1) of a machine (3), the method being carried out by supplying lubricant to the bearing progressively in one or several successive supply steps, and wherein: - a prescribed amount of lubricant (G) is determined, - before the first supply step, an ultrasonic signal is measured by a transducer mounted in connection with the rotating bearing, and from the ultrasonic signal an initial value (M0) of a scalar indicator representative of the lubrication condition of the bearing is extracted, and said measurement and value extraction are repeated after each subsequent lubricant supply step, wherein each measurement is performed after a post-supply stabilization period the length of which is such that it allows the supplied lubricant to operate fully, - the amount of lubricant (gn) supplied in the successive supply steps is less than the prescribed amount of lubricant (G), - each value (Mn) of the scalar indicator is evaluated relative to the initial value (M0) starting from the second extracted value (M1) and relative to one or more of the previously extracted values (M1, M2,..., Mn-1) starting from the third measurement, - based on each of the evaluations it is decided whether to stop or continue the lubrication sequence.

2. The method of claim 1, wherein, The scalar indicator is the root mean square (RMS) of the ultrasonic signal.

3. The method of claim 2, wherein, The sequence is continued when the extracted value is significantly lower than the previously extracted value.

4. The method of claim 2, wherein, The sequence is continued when the extracted value is substantially the same as the previously extracted value, unless the extracted value remains unchanged in a given number of successive measurements and value extractions, in which case the sequence is stopped and the lubrication condition is considered successful.

5. The method of claim 2, wherein, The sequence is stopped due to excessive lubrication when the extracted value is higher than the initial value (M0) or at least a given amount higher than the initial value.

6. The method of claim 2, wherein, The sequence is stopped due to a successful lubrication condition when the extracted value is significantly higher than the previously extracted value after the previously extracted value was significantly lower than the immediately preceding one.

7. The method of claim 2, wherein, The sequence is stopped due to a failed lubrication condition when the extracted value is significantly higher than the previously extracted value after the previously extracted value was substantially the same as the immediately preceding one.

8. The method according to claim 2, further comprising an intermediate measurement of the ultrasonic signal during a stabilization time after the first lubricant supply step and before the second time of extracting the value (Ml) of the scalar indicator, and comprising an intermediate extracted value (M') of the scalar indicator from the intermediate measured signal, and wherein, The sequence is stopped due to a suspected bearing failure if the intermediate extracted value (M') is significantly lower than the initial value (M0) and the second extracted value (M1) is significantly higher than the intermediate extracted value (M').

9. The method of claim 1, wherein, The scalar indicator or an additional scalar indicator is the kurtosis.

10. The method according to any of the preceding claims, further comprising determining a refill interval (T), and wherein, Said method is performed several times at intervals equal to or shorter than the replenishment interval.

11. The method of claim 10, wherein, The replenishment interval is updated between successive applications of said method, and wherein the update is based on the results of the steps of the method.

12. The method of claim 11, wherein, A shorter replenishment interval is applied when it is determined that a higher total amount of lubricant than the prescribed amount of lubricant (G) is required before stopping the lubrication sequence.

13. The method of claim 1, wherein, The method is fully automatic.

14. A system for supplying lubricant to at least one rotating bearing, the system comprising: - at least one rotating bearing (1), - a lubricant supply reservoir (7) provided with flow control means (8) for controlling the flow of lubricant out of the lubricant supply reservoir, - at least one tube (9) for feeding the lubricant from the reservoir towards the at least one rotating bearing (1), - at least one transducer (5) suitable for measuring ultrasonic signals when the transducer is mounted in connection with the rotating bearing, - a signal processing unit (6) coupled to the at least one transducer and to the flow control device, and configured to - calculate and store a value of a scalar indicator representative of the lubrication condition of the bearing, - actuate or stop the flow from the reservoir to the bearing according to the evaluation of the value according to the method of any one of claims 1 to 13, - transmit information to a user of the system about the lubrication condition and / or the bearing condition.

15. The system of claim 14, wherein, The system is configured to operate automatically.

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