Sliding bearing dynamic load measuring method

Abstract

A sliding bearing dynamic load measuring method belongs to the technical field of mechanical transmission. In order to solve the problems of low accuracy and low precision of the existing dynamic load measurement of the bearing, the method comprises the following steps of: measuring a bearing load value of a calibration point by adopting a loading measurement calibration device, and fitting the bearing load value into a voltage-load calibration curve; the resistance strain gauge is arranged at the stress sensitive position of the bearing seat, and when the resistance strain gauge generates a variable resistance value due to the deformation of the bearing seat, the strain bridge outputs a voltage signal; and according to a voltage signal output by the strain bridge, a corresponding load value, namely a dynamic load measurement value, is obtained in a voltage-load calibration curve. The device is used for carrying out load measurement on the bearing.

Description

Technical Field

[0001] The present invention relates to a method for measuring the dynamic load of a sliding bearing, belonging to the technical field of mechanical transmission. Background Art

[0002] Bearings are important components in contemporary mechanical equipment. Their main function is to support rotating mechanical bodies, reduce the friction coefficient during their movement, and ensure their rotational accuracy. Sliding bearings are widely used in the transmission systems of ships and are an important part of gear transmission devices. Studying the dynamic load of sliding bearings can not only reflect the operating conditions of the shafting, but also understand the dynamic transmission error of gears, the transmission relationship from the dynamic load on the tooth surface to the dynamic load on the bearing, and the vibration mechanism of the reducer. Therefore, the research on bearing dynamic load is of great significance, and accurately measuring the dynamic load of sliding bearings is the primary task.

[0003] Currently, the methods for measuring bearing dynamic load mainly include strain measurement method and jacking method, etc. Among them, the strain measurement method is the most widely used. This method has relatively high measurement accuracy, can achieve dynamic and static measurement of bearing dynamic load, the experimental equipment and technology are relatively mature, it is easy to use and operate, and it can also measure closed structures. The equipment used in the jacking method is simple and the operation is convenient. Since it is a direct measurement of the load, the result processing process is simple. However, it cannot be carried out in some closed structures and is easily restricted by the structure and environment of the test object.

[0004] Currently, for the load measurement of bearings, the following problems exist:

[0005] 1. It is more limited to static loads and does not consider actual dynamic factors. There are few practical methods for measuring bearing dynamic loads.

[0006] 2. When using the strain measurement method to measure bearing dynamic load currently, there is a lack of theoretical guidance for the installation position of strain gauges. A reasonable pasting position will greatly improve the measurement accuracy, save test time and test costs.

[0007] 3. Currently, there are few methods for measuring bearing loads, especially the lack of high-precision measurement methods for bearing dynamic loads, which affects the in-depth study of the performance of gear transmission systems.

[0008] Therefore, there is an urgent need for a high-precision measurement method for the dynamic load of sliding bearings. Summary of the Invention

[0009] The purpose of the present invention is to solve the problems of low accuracy and low precision in the existing measurement of bearing dynamic loads, and provide a method for measuring the dynamic load of a sliding bearing.

[0010] A method for measuring the dynamic load of a sliding bearing according to the present invention includes:

[0011] Use a loading measurement and calibration device to measure the bearing load value at the calibration point and fit it into a "voltage-load" calibration curve;

[0012] Place the resistance strain gauge at the stress-sensitive position of the bearing housing. When the resistance value of the resistance strain gauge changes due to the deformation of the bearing housing, the strain bridge outputs a voltage signal;

[0013] According to the voltage signal output by the strain bridge, obtain the corresponding load value in the "voltage-load" calibration curve, which is the dynamic load measurement value.

[0014] Preferably, it further includes: using wavelet threshold denoising to filter the voltage signal output by the strain bridge.

[0015] Preferably, the using wavelet threshold denoising to filter the voltage signal output by the strain bridge specifically includes:

[0016] Select a wavelet to perform multi-layer wavelet decomposition on the signal;

[0017] Perform threshold processing on the coefficients of each decomposed layer to obtain estimated wavelet coefficients;

[0018] Perform wavelet reconstruction according to the denoised wavelet coefficients to obtain the denoised signal.

[0019] Preferably, it further includes: the voltage signal output by the strain bridge is output to a strain gauge, amplified by the strain gauge, and then output to a multi-channel acquisition card for synchronous sampling;

[0020] The sampling frequency F0 of the multi-channel acquisition card is:

[0021]

[0022] where N0 represents the number of sampling points per meshing cycle, n0 represents the rotational speed of the high-speed gear in the gear pair, and K0 represents the number of teeth of the high-speed gear.

[0023] Preferably, the specific method of placing the resistance strain gauge at the stress-sensitive position of the bearing housing includes:

[0024] Calculate the bearing oil film pressure distribution;

[0025] Apply the bearing oil film pressure distribution to the bearing housing and perform simulation to obtain the stress-sensitive position;

[0026] Machine a stress concentration mechanism at the stress-sensitive position and paste the resistance strain gauge on the stress concentration mechanism.

[0027] Preferably, the specific method of calculating the bearing oil film pressure distribution includes:

[0028] Use numerical calculation to solve the Reynolds equation to obtain the stress distribution of the sliding bearing oil film;

[0029] Solve for the resultant force on the x-axis and y-axis by numerical integration;

[0030] Set the eccentricity value, compare the resultant force on the y-axis with the tangential force of gear meshing, and iterate the magnitude of the eccentricity. When the resultant force on the y-axis is equal to the tangential force of gear meshing, obtain the corresponding eccentricity;

[0031] Compare the resultant force on the x-axis with the radial force of gear meshing, and iterate the magnitude of the offset angle. When the resultant force on the x-axis is equal to the radial force of gear meshing, obtain the corresponding offset angle.

[0032] Preferably, a stress concentration mechanism is machined at the stress-sensitive position, and a resistance strain gauge is pasted on the stress concentration mechanism, specifically including:

[0033] The strain gauge for measuring the radial dynamic force of the bearing is pasted at the root of the bearing seat of the gearbox housing. An annular groove is machined on the end face of the bearing seat, and the test strain gauge is pasted radially in the groove;

[0034] The strain gauge for measuring the axial dynamic force of the bearing is pasted at the radial part of the bearing seat of the gearbox housing. A radial annular groove is machined on the bearing seat, and the test strain gauge is pasted axially in the groove.

[0035] Preferably, the specific method for measuring and calibrating the bearing load value at the calibration point by using the load measurement and calibration device and fitting it into a calibration curve includes:

[0036] Use a lead screw nut loader and a pressure sensor to apply a load in the same direction at both ends of the same axis of the bearing, and the strain bridge outputs a voltage signal;

[0037] Apply multiple load steps and sequentially obtain the voltage signals output by the strain bridge;

[0038] According to the multiple load steps and the voltage signals output by the strain bridge, obtain the corresponding points of the relationship between different bearing forces and strain voltages in the same direction;

[0039] Fit a calibration curve according to the corresponding points of the relationship between bearing force and strain voltage.

[0040] Preferably, the strain bridge adopts a quarter strain bridge, and the quarter strain bridge includes a resistance strain gauge R1, a temperature compensation strain gauge R2, a resistor R3, and a resistor R4;

[0041] The resistance strain gauge R1 and the temperature compensation strain gauge R2 are connected in series on a branch of the strain bridge, and the temperature compensation strain gauge R2 serves as the adjacent arm of the resistance strain gauge R1;

[0042] The resistor R3 and the resistor R4 are connected in series on another branch of the strain bridge.

[0043] Preferably, the resistances of R1, R2, R3 and R4 are the same, and the resistance value is R for all of them;

[0044] When strain occurs, it causes a change in the resistance value of R1, and the change amount is ΔR. The output voltage e is:

[0045]

[0046] Wherein, E represents the power supply voltage of the bridge, K represents the sensitivity coefficient of the strain gauge, and ε represents the strain.

[0047] Advantages of the present invention: The present invention proposes a method for measuring the dynamic load of a sliding bearing. A force sensor is composed of a resistance strain gauge and a bearing seat of an accelerator box body. Under the test conditions of high-speed and heavy-load of a reducer, a voltage signal related to the dynamic load of the bearing is output. Through the circuit and mathematical relationship, the strain and dynamic load of the bearing seat can be obtained, realizing the high-precision synchronous measurement of the multi-directional dynamic loads of multiple sliding bearings of a gear transmission device, and providing technical support for the research on the working performance of the gear transmission system. This measurement method has high measurement accuracy and wide applicability, and can be extended to accurately determine the dynamic load of bearings of other types of gear transmission devices. Brief Description of the Drawings

[0048] Figure 1 is the principle block diagram of the method for measuring the dynamic load of the sliding bearing described in the present invention;

[0049] Figure 2 is the flow block diagram of the method for measuring the dynamic load of the sliding bearing described in the present invention;

[0050] Figure 3 is the schematic diagram of a Wheatstone strain bridge;

[0051] Figure 4 is the structural schematic diagram of the quarter strain bridge described in the present invention;

[0052] Figure 5 is the structural schematic diagram of a temperature compensation half bridge;

[0053] Figure 6 is the schematic diagram of a single screw fixing the temperature compensation block;

[0054] Figure 7 is the schematic diagram of pasting the temperature compensation strain gauge;

[0055] Figure 8 is the stress distribution diagram of the oil film of the sliding bearing of the driving wheel;

[0056] Figure 9 is the stress distribution diagram of the bearing seat of the sliding bearing of the front-end driving wheel;

[0057] Figure 10 is the schematic diagram of the strain gauge arrangement for the dynamic force test of the main and driven wheel bearings at the front end of the gear box body;

[0058] Figure 11 is the stress distribution diagram of the bearing housing of the rear-end driving pulley sliding bearing;

[0059] Figure 12 is the schematic diagram of the strain gauge arrangement for the dynamic force test of the main and driven pulley bearings at the rear end of the gear housing;

[0060] Figure 13 is the schematic diagram of the strain gauge arrangement for the axial dynamic force test of the main and driven pulley bearings of the gear housing;

[0061] Figure 14 is the schematic diagram of the strain gauge change cover;

[0062] Figure 15 is the schematic diagram of the radial loading mechanism of the driving pulley;

[0063] Figure 16 is the schematic diagram of the radial loading mechanism of the driven pulley;

[0064] Figure 17 is the schematic diagram of the axial loading mechanism of the bearing;

[0065] Figure 18 is the schematic diagram of the transfer function of the bearing;

[0066] Figure 19 is the schematic diagram of the basic steps of wavelet denoising;

[0067] Figure 20 is the schematic diagram of the wavelet decomposition process. Specific implementation manners

[0068] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0069] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0070] Next, the present invention will be further described in conjunction with the accompanying drawings and specific embodiments, but it is not limited to the present invention.

[0071] Embodiment 1:

[0072] Next, in conjunction with Figures 1 - 20 This embodiment will be described. The method for measuring the dynamic load of a sliding bearing described in this embodiment includes:

[0073] Use a loading measurement and calibration device to measure the bearing load value at the calibration point and fit it into a "voltage-load" calibration curve;

[0074] Place the resistance strain gauge at the stress-sensitive position of the bearing housing. When the resistance value of the resistance strain gauge changes due to the deformation of the bearing housing, the strain bridge outputs a voltage signal;

[0075] According to the voltage signal output by the strain bridge, obtain the corresponding load value in the "voltage-load" calibration curve, which is the dynamic load measurement value.

[0076] Furthermore, it also includes: using wavelet threshold denoising to filter the voltage signal output by the strain bridge.

[0077] Even further, the using wavelet threshold denoising to filter the voltage signal output by the strain bridge specifically includes:

[0078] Select a wavelet to perform multi-level wavelet decomposition on the signal;

[0079] Perform threshold processing on the coefficients of each decomposed layer to obtain estimated wavelet coefficients;

[0080] Perform wavelet reconstruction based on the denoised wavelet coefficients to obtain the denoised signal.

[0081] Even further, it also includes: the voltage signal output by the strain bridge is output to a strain gauge, amplified by the strain gauge, and then output to a multi-channel acquisition card for synchronous sampling;

[0082] The sampling frequency F0 of the multi-channel acquisition card is:

[0083]

[0084] where N0 represents the number of sampling points per meshing cycle, n0 represents the rotational speed of the high-speed gear in the gear pair, and K0 represents the number of teeth of the high-speed gear.

[0085] Even further, the specific method of placing the resistance strain gauge at the stress-sensitive position of the bearing housing includes:

[0086] Calculate the bearing oil film pressure distribution;

[0087] Apply the bearing oil film pressure distribution to the bearing housing and perform simulation to obtain the stress-sensitive position;

[0088] Machine a stress concentration mechanism at the stress-sensitive position and paste the resistance strain gauge on the stress concentration mechanism.

[0089] Even further, the specific method of calculating the bearing oil film pressure distribution includes:

[0090] The Reynolds equation is solved numerically to obtain the stress distribution of the oil film in the sliding bearing;

[0091] The resultant forces on the x-axis and y-axis are solved by numerical integration;

[0092] The eccentricity value is determined. The resultant force on the y-axis is compared with the tangential force of gear meshing, and the magnitude of the eccentricity is iterated. When the resultant force on the y-axis is equal to the tangential force of gear meshing, the corresponding eccentricity is obtained;

[0093] The resultant force on the x-axis is compared with the radial force of gear meshing, and the magnitude of the offset angle is iterated. When the resultant force on the x-axis is equal to the radial force of gear meshing, the corresponding offset angle is obtained.

[0094] Furthermore, a stress concentration mechanism is machined at the stress-sensitive position, and a resistance strain gauge is pasted on the stress concentration mechanism, specifically including:

[0095] The strain gauge for measuring the radial dynamic force of the bearing is pasted at the root of the bearing seat of the gearbox housing. An annular groove is machined on the end face of the bearing seat, and the test strain gauge is pasted radially in the groove;

[0096] The strain gauge for measuring the axial dynamic force of the bearing is pasted at the radial part of the bearing seat of the gearbox housing. A radial annular groove is machined on the bearing seat, and the test strain gauge is pasted axially in the groove.

[0097] Furthermore, the specific method for measuring and calibrating the bearing load value at the calibration point by using the load measurement and calibration device and fitting it into a calibration curve includes:

[0098] A lead screw nut loader and a pressure sensor are used to apply load in the same direction at both ends of the same shaft of the bearing, and the strain bridge outputs a voltage signal;

[0099] Multiple load steps are applied to sequentially obtain the voltage signals output by the strain bridge;

[0100] According to the multiple load steps and the voltage signals output by the strain bridge, the corresponding points of the relationship between different bearing forces and strain voltages in the same direction are obtained;

[0101] According to the corresponding points of the relationship between the bearing force and the strain voltage, a calibration curve is obtained by fitting.

[0102] Furthermore, the strain bridge adopts a quarter strain bridge, and the quarter strain bridge includes a resistance strain gauge R1, a temperature compensation strain gauge R2, a resistor R3, and a resistor R4;

[0103] The resistance strain gauge R1 and the temperature compensation strain gauge R2 are connected in series on a branch of the strain bridge, and the temperature compensation strain gauge R2 serves as the adjacent arm of the resistance strain gauge R1;

[0104] The resistor R3 and the resistor R4 are connected in series on the other branch of the strain bridge.

[0105] Further, the resistance values of R1, R2, R3 and R4 are the same, and the resistance value is R for all of them;

[0106] When strain occurs, it causes a change in the resistance value of R1, and the change amount is ΔR. The output voltage e is:

[0107]

[0108] where E represents the voltage of the bridge power supply, K represents the sensitivity coefficient of the strain gauge, and ε represents the strain.

[0109] In the present invention, a method for measuring the dynamic load of a sliding bearing is provided. This method uses a resistance strain gauge and a bearing seat of a reducer housing to form a force sensor, compares the output voltage of the strain bridge with a calibration curve previously determined and fitted by a loading measurement calibration device to obtain the load value of the sliding bearing, and removes the interference signals in the test data through wavelet analysis to meet the requirements of high-precision measurement of the dynamic load of the sliding bearing. This method has high measurement accuracy and can provide a technical basis for further understanding the dynamic transmission error of gears, the transmission relationship, interaction relationship from the tooth surface dynamic load to the bearing dynamic load, and the overall vibration mechanism of the reducer system as well as the system vibration reduction design by studying the dynamic load of the sliding bearing.

[0110] Design of the bearing dynamic load test system: The bearing dynamic load test system consists of a helical gear test box, a calibration loading device, a strain measurement strain gauge, a temperature compensation strain gauge, a strain measurement acquisition card, and strain measurement software.

[0111] Bearing dynamic load strain measurement technology: Based on the piezoresistive effect of resistance, the strain on the surface of the component will cause the deformation of the sensitive grid of the strain gauge in close contact, resulting in a change in the resistance value of the strain gauge. Since the strain gauge is connected in the circuit, the change in resistance value caused by the deformation of the bearing seat can be converted into the output of a voltage signal, realizing the conversion from mechanical physical quantity to electrical signal. The strain of the bearing seat can be obtained through the voltage signal and circuit and mathematical relationships, and then the load of the bearing seat can be obtained.

[0112] Bearing dynamic load test strain gauge layout and sensitivity structure design: The present invention provides a method for determining the layout of resistance strain gauges, that is, by calculating the oil film pressure distribution of the sliding bearing, applying the oil film pressure distribution to the bearing seat of the reducer housing for simulation to obtain the stress-sensitive positions, designing and machining a stress concentration structure at the stress-sensitive positions, pasting the strain gauges along these two directions at the stress concentration points respectively, and each strain gauge is respectively composed of a temperature compensation piece and two external standard resistors to form a strain bridge.

[0113] Design, process, and assemble a loading measurement and calibration device composed of a frame structure, a lead screw nut loader, and a high-precision pressure sensor respectively. It can apply loads simultaneously at both ends of the same axis in the same direction and display the load quantity, while obtaining the output voltage of the strain bridge in this direction. Through multi-load step loading, obtain the relationship points between different bearing forces and strain voltages in the same direction. By fitting, obtain a calibration curve and relationship formula considering a certain non-linear relationship between bearing forces and bearing seat stress and strain, and convert the bearing dynamic load fluctuation curve represented by the sampled voltage into force units, thereby obtaining the accurate bearing dynamic load represented by force units.

[0114] Filtering technology for bearing dynamic load curves: Interference caused by environmental factors will affect the test signals. Wavelet threshold denoising is performed on the collected test data to improve measurement accuracy, which usually includes: decomposition process, threshold processing process, and reconstruction process. The selection of the basic parameters of wavelet threshold denoising includes four aspects: selection of wavelet basis, selection of decomposition level, selection of threshold, and selection of threshold function.

[0115] The bearing dynamic force test system mainly includes a test strain bridge, an 8-channel strain gauge, an 8-channel data synchronous acquisition card, and a computer (including data storage, data processing, and graphical display). When calibrating from the output voltage of the strain bridge to the bearing load, it is also necessary to calibrate the loading device, pressure sensor, and digital display meter. Figure 1 This is the composition of the bearing dynamic force test system. The bearing dynamic force test signal is output from the strain bridge to the strain gauge, amplified by the strain signal conditioner, and then input into the multi-channel design acquisition card for synchronous sampling, stored in the computer hard disk, and after data processing and calculation, the bearing dynamic force waveform is displayed on the computer screen. Figure 2 This is the bearing dynamic force test signal flow.

[0116] Setting of the data acquisition frequency for bearing dynamic force measurement:

[0117] When measuring the bearing dynamic force, the specific calculation method for setting the data acquisition frequency of the data acquisition card is as follows:

[0118]

[0119] n0 is the rotational speed (r / min) of the high-speed gear in the gear pair, N0 is the number of sampling points per meshing cycle, K0 is the number of teeth of the high-speed gear, and F0 is the sampling frequency that the data acquisition card should set, that is, the number of samples per second. For example, if the rotational speed of the driving wheel (high-speed gear) is 5000 r / min, the number of teeth is 42, and 30 points are sampled per meshing cycle, then the sampling frequency is 105000 Hz, that is, 105 KHz.

[0120] Multi-channel synchronous sampling technology: A total of six strain bridges are used for the dynamic force test of the bearing. It is required that the dynamic forces of the bearing measured by the six strain bridges be synchronously sampled. The multi-channel high-speed and high-synchronization data acquisition card adopted in the present invention has a synchronization rate of 14 ns. According to the input rotational speed of 5000 r / min and the number of teeth of the driving wheel of 42 during the measurement of the bearing dynamic force, the asynchronization of two channels is 0.005% of one meshing cycle, which can meet the requirements of high-precision measurement.

[0121] The development history of the electrical measurement method of resistance strain gauges is long, the technology is mature and it is very widely used. When a component is compressed, it will deform and generate strain. The electrical measurement method of strain gauges can measure the strain on the surface of elastic elements. The resistance strain gauge is based on the piezoresistive effect of resistance. The strain on the surface of the component will cause the deformation of the sensitive grid of the strain gauge in close contact, resulting in a change in the resistance value of the strain gauge. Since the strain gauge is connected in the circuit, the change in resistance value caused by mechanical deformation can be converted into the output of voltage or current signal, realizing the conversion from mechanical physical quantity to electrical signal.

[0122] In actual measurement, in most cases, the obtained signal is converted into a voltage value, and the strain needs to be obtained from the voltage value through circuits and mathematical relationships. In most measurement cases, the strain caused by the deformation of the measured object is quite small, so the resulting change in resistance is also quite tiny. However, it is difficult to accurately measure such a small change in resistance. To address this problem, a Wheatstone bridge circuit is usually used to detect the voltage, as shown in Figure 3 .

[0123] If R1 = R2 = R3 = R4 or R1 × R2 = R3 × R4, according to circuit knowledge, no matter how large the input voltage is, the output voltage is always 0. This state is called the balanced state. If the resistance of a certain path changes, an output voltage corresponding to the resistance change will be generated.

[0124] As Figure 4 shown is a quarter-bridge circuit, where R1 is the measuring strain gauge, which is pasted on the surface of the material whose strain needs to be measured, and R2, R3, and R4 are external precision standard resistors with the same resistance value as R1. When strain occurs, it causes a change in the resistance value of the strain gauge R1, and the change amount is ΔR. Then the calculation formula for the output voltage is:

[0125]

[0126] That is:

[0127]

[0128] Among them, ε is the strain, E is the supply voltage of the bridge, and K is the sensitivity coefficient of the strain gauge, which has been calibrated when the strain gauge leaves the factory. Within a certain measurement range, K is a constant, that is, the output voltage has a linear relationship with the change in the resistance value ΔR of the strain gauge. Therefore, if the output voltage of the bridge is obtained, the magnitude of the strain can be calculated. In the present invention, the dynamic force of the sliding bearing acts on the housing, causing corresponding dynamic stress and strain in the housing structure. If the test strain gauge is pasted on the housing part near the bearing and having a certain force sensitivity, the dynamic voltage e(t) output by the strain bridge depends on the dynamic force F(t) of the bearing, and there is a certain non-linear relationship between the two. The non-linear function relationship H(e) can be obtained through a specially designed calibration method, and the dynamic force of the bearing can be obtained by measuring the output voltage e(t) of the strain bridge:

[0129] F(t) = H(e)·e(t)

[0130] When the test strain gauge R1 is used, it needs to be firmly pasted on the housing structure of the metal material. Through the bridge ( Figure 4 ), the change in the output voltage of the bridge caused by the change in the resistance value of the test strain gauge under the action of the dynamic force of the bearing is measured to obtain the dynamic force of the bearing. The resistance value of the strain gauge will also change slightly due to the influence of the environment and temperature, thus affecting the accuracy of the measurement of the dynamic force of the bearing. The reasons are as follows: one is that the strain gauge itself has a resistance temperature coefficient, and the other is that the temperature expansion coefficients of the strain gauge material and the metal material are different. Both of these will cause the resistance value of the test strain gauge to change due to temperature changes, resulting in measurement errors. Therefore, appropriate temperature compensation measures must be adopted.

[0131] Generally, the commonly used temperature compensation method is to use a strain gauge R2 that is exactly the same as the measurement strain gauge R1 as the adjacent arm of R1 in the bridge. See Figure 5 . R3 and R4 are still external precision standard resistors. R2 is pasted on the temperature compensation block. The temperature compensation block has the same material composition as the measured structure and is fixed near the measured point, with the same temperature as the measured point, but should not have any deformation and strain. In this way, R2 has the same temperature change effect as R1, that is, the same resistance value change caused by the same temperature, but R2 should not have other resistance value changes caused by deformation. Since R1 and R2 are adjacent arms in the bridge, the bridge outputs caused by the same resistance value change generated by temperature will cancel each other out, playing a temperature compensation role. In addition, R2 does not have additional resistance value changes that will affect the bridge output.

[0132] The requirements for the temperature compensation block are that it has the same material composition as the structure to be measured, the same temperature as the measured point, and does not bear any deformation and strain. In the present invention, a rectangular metal block about 20 mm in length, which is processed from the same material as the gear box, is used as the temperature compensation block. After the surfaces of the box body and the temperature compensation block are processed, they are closely attached to ensure temperature conduction. It is fixed at the same temperature near the measuring point on the box body with a single screw. Using a single screw for fastening is to ensure temperature conduction while preventing any deformation of the box body from being transmitted to the temperature compensation block, which may affect the measurement accuracy, as Figure 6 and Figure 7 shown.

[0133] In a pair of gear transmissions, there is a relationship of action and reaction between the driving gear and the driven gear. Figure 8 The figure shown is a schematic diagram of the end face radial force reflected by the line of sight from the input end of the driving gear of the measured helical gear pair (referred to as the front end in this application). In the figure, n1 and n2 are the rotational speed directions of the driving and driven gears respectively, and F r1 , F r2 are the normal forces on the tooth surfaces of the driving and driven gears, acting on the lower left of the driving gear shaft and the upper right of the driven gear shaft respectively, and the angle with the vertical direction is the end face pressure angle of the gear pair.

[0134] The installation position of the resistance strain gauge should be near the line of engagement. However, due to the influence of the gear box structure, etc., there will be a slight deviation in the position of the actual maximum stress. In order to achieve the purpose of high-precision measurement and reduce the test time and cost, the present invention proposes a method for accurately determining the layout of the resistance strain gauge by combining calculation and simulation.

[0135] First, the Reynolds equation is solved by numerical calculation to obtain the stress distribution of the sliding bearing oil film as shown in Figure 8 , and then the resultant forces on the x-axis and y-axis are solved by numerical integration; a value of eccentricity is determined. The resultant force on the y-axis is compared with the tangential force of gear meshing and the magnitude of the eccentricity is iterated. When the two forces are equal, the eccentricity can be determined; then the resultant force on the x-axis is compared with the radial force of gear meshing and the magnitude of the misalignment angle is iterated. When the two forces are equal, the misalignment angle can be determined. After obtaining the relevant parameters and stress distribution of the sliding bearing oil film, the stress of the sliding bearing oil film can be applied to the sliding bearing in contact with the oil film, and the stress distribution of the sliding bearing housing can be obtained as shown in Figure 9 , and the stress concentration part is selected as the bonding position of the resistance strain gauge.

[0136] The dynamic force test strain gauges for the front bearings of the driving and driven gears of the gear box body are respectively pasted on the lower left of the driving gear shaft and the upper right of the driven gear shaft, and are pasted on the root end face of the box body bearing seat. The corresponding temperature compensation blocks and temperature compensation strain gauges are distributed near the test strain gauges, as shown in Figure 10 .

[0137] Figure 12The figure shows a schematic diagram of the end face radial acting force reflected by the sight line from the output end of the driven wheel of the bevel gear pair to be measured (referred to as the rear end in this application). In the figure, n1 and n2 are the rotational speed directions of the driving and driven wheels respectively, and F r1 and F r2 are the normal forces on the tooth surfaces of the driving and driven wheels respectively, acting on the lower right of the driving wheel shaft and the upper left of the driven wheel shaft respectively, and the angle with the vertical direction is the end face pressure angle of the gear pair. Figure 11 is the stress distribution of the bearing housing of the sliding bearing of the driving wheel at the rear end. The dynamic force test strain gauges of the main and driven wheel rear end bearings of the gear housing are respectively pasted on the lower right of the driving wheel shaft and the upper left of the driven wheel shaft, and on the root end face of the housing bearing seat. The corresponding temperature compensation blocks and temperature compensation strain gauges are distributed near the test strain gauges. See Figure 12 .

[0138] Figure 13 The figure shows a schematic diagram of the axial acting force of the bevel gear pair to be measured. In the figure, F x1 and F x2 are the axial forces of the driving and driven wheels respectively, which are a pair of action and reaction forces, acting on the sliding bearings that can bear the axial force respectively, and are transmitted to the housing structure through the sliding bearings. The dynamic force test strain gauges of the housing bearings' axial direction are respectively pasted on the radial positions of the bearing seats of the sliding bearings that can bear the axial force. The corresponding temperature compensation blocks and temperature compensation strain gauges are distributed near the test strain gauges. See Figure 13 .

[0139] As shown in Figure 10 and Figure 12 , the dynamic force test strain gauges of the bearing's radial direction are pasted on the root of the housing bearing seat of the gear housing. A ring-shaped groove is machined at this part of the bearing seat end face, and the test strain gauges are pasted along the radial direction in the groove according to the illustrated positions. This groove design is to generate a certain stress concentration under the action of the bearing's radial force to improve the sensitivity of strain measurement.

[0140] As shown in Figure 13 , the dynamic force test strain gauges of the bearing's axial direction are pasted on the radial part of the housing bearing seat of the gear housing. A radial ring-shaped groove is machined at this part of the bearing seat, and the test strain gauges are pasted along the axial direction in the groove according to the illustrated positions. This groove design is to generate a certain stress concentration under the action of the bearing's axial force to improve the sensitivity of strain measurement.

[0141] Both the test strain gauges and the temperature compensation gauges use special glue and are firmly pasted on the surface of the gear housing after surface cleaning. In order to avoid damage to the strain gauges during the modification, movement, and transportation of the gearbox, another protective glue needs to be covered on the surface of the strain gauges. Since the change glue is flexible, the strain gauges will still be damaged when coming into contact or collision with metal corners and edges. Therefore, an invention designs a metal sheet protection device, as shown in Figure 14As shown, to protect the strain gauge from damage during the test.

[0142] To measure the dynamic force of the bearing, it is necessary to first measure the output voltage e(t) of the strain bridge, and then calculate the dynamic force of the bearing through the transfer function H(e) between the output voltage e(t) of the strain bridge and the dynamic force F(t) of the bearing. Since the dynamic force of the bearing is generated by the dynamic meshing force of the gear being transmitted to the shaft, bearing, and housing, and the relationship between the shaft and the bearing is a contact relationship, and the size of the contact area is related to the transmitted load, the transfer function H(e) is a non-linear function. Moreover, this function is related to the housing structure characteristics, strain gauge characteristics, strain gauge wiring, and strain gauge characteristics. Therefore, it is necessary to obtain the transfer function H(e) under actual test conditions through the calibration of the overall measurement system. The accuracy of the transfer function of the actual test system directly determines the accuracy of the bearing dynamic force test, so it is very important in this test technology.

[0143] The principle of the bearing radial static load loading mechanism is as Figure 15 、 Figure 16 shown, Figure 15 is the loading mechanism for the two support bearings of the driving wheel, Figure 16 is the loading mechanism for the two support bearings of the driven wheel. The loading mechanism adopts a screw-nut pair mechanism. The axis of the screw-nut pair makes an angle with the vertical direction equal to the end face pressure angle of the gear pair. A high-precision pressure sensor and a thrust bearing are installed at the contact end of the screw and the gear shaft to perform stepped loading according to the pre-determined load levels and load magnitudes, and to facilitate the rotational feeding loading of the screw.

[0144] The driven wheel loading mechanism and the driving wheel loading mechanism adopt the same mechanism to save equipment processing costs and workload. The only difference is that when loading, the gearbox is placed and fixed upside down. See Figure 16 At this time, stepped loading can be conveniently achieved in the same way as for the driving wheel.

[0145] The principle of the bearing axial static load loading mechanism is as Figure 17 shown. The loading mechanism adopts a screw-nut pair mechanism. The axis of the screw-nut pair is collinear with the axial direction of the gear shaft. A high-precision pressure sensor and a thrust bearing are installed at the contact end of the screw and the end face of the gear shaft to perform stepped loading according to the pre-determined load levels and load magnitudes, and to facilitate the rotational feeding loading of the screw.

[0146] When performing stepped loading according to the pre-determined load levels and load magnitudes, each time a radial load or axial load is applied, the strain bridge for measuring the radial force of the bearing or the strain bridge for measuring the axial force will display the corresponding output voltage value. Each radial load value or axial load value can be converted into the radial load value or axial load value of each bearing according to the bearing support position and the loading position, and at the same time, record the output voltage value of the strain bridge corresponding to the bearing radial load or axial load, as Figure 18As shown. For each loading of each bearing, a point in a two-dimensional coordinate system with the bearing load as the abscissa and the output voltage of the strain bridge as the ordinate can be obtained. After multiple staged loadings, by fitting the sequence of points in the coordinate system, the conversion function H(e) between the output voltage of the strain bridge and the bearing force can be obtained. Since the relationship between the shaft and the bearing is a contact relationship, this function has a certain degree of non-linearity.

[0147] Two bearings are installed on each of the driving wheel shaft and the driven wheel shaft, so a total of four radial force test strain bridges are installed; one axial force test strain bridge is installed on each of the driving wheel shaft and the driven wheel shaft, so a total of six strain bridges are installed in the gearbox bearing dynamic force test system. Since there are slight differences in the strain gauge pasting position, pasting structure, and the performance of the strain gauge and the strain indicator for each strain bridge, six different non-linear conversion functions H i (e), i = 1, …, 6 can be obtained through calibration to improve the accuracy of bearing dynamic force testing.

[0148] The above calibration method covers the entire bearing dynamic force test system from the strain bridge, leads, strain indicator, data acquisition card to the signal acquisition, processing, and calculation software, improves the test accuracy, and can quantitatively estimate the test accuracy of the test system. The method for estimating the test accuracy is as follows: After fitting the bearing dynamic force conversion function, the deviation of all load / strain bridge output point sets from the fitting curve can be calculated and analyzed, which is the test accuracy of the above test system.

[0149] During the signal measurement process, the environmental noise of the test bench, mechanical noise, the influence of the small gaps and additional deformations of the system under dynamic conditions, etc. will all affect the signal test and reduce the measurement accuracy. Therefore, the present invention will adopt advanced wavelet technology to preprocess the dynamic test signals to achieve the purpose of improving the test accuracy.

[0150] Wavelet transform is a time-scale (time-frequency) analysis method for signals. It has the characteristics of multi-resolution analysis, and has the ability to characterize the local features of signals in both the time and frequency domains. It is a time-frequency localization analysis method with a fixed window size but a changeable shape, and both the time window and the frequency window can be changed. Wavelet transform has a lower time resolution and a higher frequency resolution in the low-frequency part, and a higher time resolution and a lower frequency resolution in the high-frequency part.

[0151] Fourier transform decomposes a signal into a superposition of a series of sine and cosine functions with different frequencies. Similarly, wavelet transform decomposes a signal into a superposition of a series of wavelet functions (or fitting of wavelet functions with different scales and times), and these wavelet functions are all obtained by translating and scaling a mother wavelet.

[0152] The wavelet transform is to perform an inner product of a function called the basic wavelet, after being displaced by τ, with the signal x(t) to be analyzed at different scales α, that is:

[0153]

[0154] In the formula, α > 0, which is called the scale factor and is used to stretch the basic wavelet function. τ reflects the displacement and its value can be positive or negative. Both α and τ are continuous variables, so it is also called the continuous wavelet transform.

[0155] The wavelet transform has strong decorrelation of data. It can make the energy of the signal concentrate in some large wavelet coefficients in the wavelet domain, while the energy of the noise is distributed throughout the wavelet domain. Therefore, after wavelet decomposition, the amplitude of the wavelet coefficients of the signal is greater than that of the noise coefficients. It can be considered that the wavelet coefficients with relatively large amplitudes are generally dominated by the signal, while the coefficients with relatively small amplitudes are largely noise. Thus, by using the threshold method, most of the noise coefficients are reduced to 0, that is, the coefficients smaller than the threshold are removed as interference noise, and then wavelet reconstruction is performed to achieve noise reduction.

[0156] The essence of wavelet threshold denoising is the process of suppressing the useless part and enhancing the useful part in the signal. The process of wavelet threshold denoising is as follows:

[0157] The decomposition process, that is, selecting a wavelet to perform n-layer wavelet decomposition on the signal;

[0158] The threshold processing process, that is, performing threshold processing on the coefficients of each decomposed layer to obtain the estimated wavelet coefficients;

[0159] The reconstruction process, performing wavelet reconstruction based on the denoised wavelet coefficients to obtain the denoised signal.

[0160] The basic steps of wavelet denoising are as Figure 19 shown. Wavelet decomposition is to decompose the original signal X into the high-frequency component cd1 and the low-frequency component ca1, and then repeat the above operations on the new low-frequency component ca1. As shown below Figure 20 shown, wavelet decomposition: X → ca3, cd3, cd2, cd1; wavelet reconstruction: ca3, cd3, cd2, cd1 → X. Where ca is the low-frequency information and the approximate component, and cd is the high-frequency information and the detail component.

[0161] Although the present invention has been described herein with reference to particular embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that numerous modifications may be made to the exemplary embodiments, and that other arrangements may be designed, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in ways different from those described in the original claims. It should also be understood that the features described in connection with separate embodiments may be used in other described embodiments.

Claims

1. A method for measuring dynamic load of a sliding bearing, characterized in that: It includes: The bearing load value at the calibration point is measured using a loading measurement calibration device and fitted into a "voltage-load" calibration curve; The resistance strain gauge is placed at the stress-sensitive position of the bearing seat. When the resistance value of the resistance strain gauge changes due to the deformation of the bearing seat, the strain bridge outputs a voltage signal. According to the voltage signal output by the strain bridge, the corresponding load value is obtained in the "voltage-load" calibration curve, which is the dynamic load measurement value.

2. A method for measuring dynamic load of a sliding bearing according to claim 1, characterized in that: It also includes: using wavelet threshold denoising to filter the voltage signal output by the strain bridge.

3. A method for measuring dynamic load of a sliding bearing according to claim 2, characterized in that: The wavelet threshold denoising is used to filter the voltage signal output by the strain bridge, specifically including: Select a wavelet to perform multi-layer wavelet decomposition on the signal; Perform threshold processing on the decomposed coefficients of each layer to obtain the estimated wavelet coefficients; The denoised signal is obtained by performing wavelet reconstruction based on the denoised wavelet coefficients.

4. A method for measuring dynamic load of a sliding bearing according to claim 1, characterized in that: It also includes: the voltage signal output by the strain bridge is output to the strain gauge, and after being amplified by the strain gauge, it is output to a multi-channel acquisition card for synchronous sampling; The sampling frequency F0 of the multi-channel acquisition card is: Among them, N0 represents the number of sampling points in each meshing cycle, n0 represents the speed of the high-speed gear in the gear pair, and K0 represents the number of teeth of the high-speed gear.

5. A method for measuring dynamic load of a sliding bearing according to claim 1, characterized in that: Specific methods for placing resistance strain gauges at stress-sensitive locations of bearing seats include: Calculate and obtain the bearing oil film pressure distribution; Apply the bearing oil film pressure distribution to the bearing seat and perform simulation to obtain the stress sensitive position; A stress concentration mechanism is processed at a stress sensitive position, and a resistance strain gauge is pasted on the stress concentration mechanism.

6. A method for measuring dynamic load of a sliding bearing according to claim 5, characterized in that: The specific method for calculating and obtaining the bearing oil film pressure distribution includes: The Reynolds equation is solved by numerical calculation to obtain the stress distribution of the oil film in the sliding bearing. Solve the resultant forces on the x-axis and y-axis by numerical integration; The eccentricity value is proposed, the y-axis resultant force is compared with the gear meshing tangential force, and the eccentricity is iterated. When the y-axis resultant force is equal to the gear meshing tangential force, the corresponding eccentricity is obtained; The x-axis resultant force is compared with the gear meshing radial force, and the size of the offset angle is iterated. When the x-axis resultant force is equal to the gear meshing radial force, the corresponding offset angle is obtained.

7. A method for measuring dynamic load of a sliding bearing according to claim 5, characterized in that: Processing a stress concentration mechanism at a stress sensitive position and pasting a resistance strain gauge on the stress concentration mechanism specifically includes: The strain gauge for testing radial dynamic force of the bearing is pasted on the root of the bearing seat of the gearbox body. An annular groove is machined on the end face of the bearing seat, and the test strain gauge is pasted in the groove along the radial direction; The bearing axial dynamic force test strain gauge is pasted on the radial part of the gear box bearing seat. A radial annular groove is machined on the bearing seat, and the test strain gauge is pasted in the groove along the axial direction.

8. A method for measuring dynamic load of a sliding bearing according to claim 1, characterized in that: The specific method of using the loading measurement calibration device to measure the bearing load value of the calibration point and fitting it into a calibration curve includes: Using a screw nut loader and a pressure sensor, loads are applied in the same direction at both ends of the same axis of the bearing, and the strain bridge outputs a voltage signal; Load multiple load steps and obtain the voltage signal output by the strain bridge in sequence; According to the multiple load steps and the output voltage signal of the strain bridge, the corresponding points of the relationship between the bearing force and the strain voltage in different directions are obtained; According to the corresponding points of the relationship between bearing force and strain voltage, the calibration curve is obtained by fitting.

9. A method for measuring dynamic load of a sliding bearing according to claim 1, characterized in that: The strain bridge adopts a quarter strain bridge, and the quarter strain bridge includes a resistance strain gauge R1, a temperature compensation strain gauge R2, a resistor R3 and a resistor R4; The resistance strain gauge R1 and the temperature compensation strain gauge R2 are connected in series on a branch of the strain bridge, and the temperature compensation strain gauge R2 serves as the adjacent arm of the resistance strain gauge R1; Resistors R3 and R4 are connected in series on another branch of the strain bridge.

10. A method for measuring dynamic load of a sliding bearing according to claim 9, characterized in that: The resistance values ​​of R1, R2, R3 and R4 are the same, which is R; When strain occurs, the resistance of R1 changes by ΔR, and the output voltage e is: Where E is the bridge power supply voltage, K is the sensitivity coefficient of the strain gauge, and ε is the strain.

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