Face gear oil film thickness measuring device and method

Abstract

The invention belongs to the technical field of surface gear oil film measurement, and provides a surface gear oil film thickness measuring device and method.The device comprises a fixed surface gear, a straight gear, an ultrasonic probe and a fiber bragg grating array sensor, and the fixed surface gear and the straight gear are meshed with each other and are in transmission connection through a vertical gear; the blind hole for placing the ultrasonic probe is further formed in the back of the fixed face gear and perpendicular to the meshing face, on one hand, the ultrasonic probe embedded in the blind hole can detect the thickness of an oil film on the meshing face in a close range under the condition that meshing rotation of the gear is not affected, and the precision of oil film thickness measurement can be improved; and on the other hand, the fiber grating array sensors located in the tooth grooves corresponding to the meshing surfaces can synchronously monitor the temperature and the stress on the meshing surfaces, the oil film thickness of the meshing surfaces can be measured from the synergistic angle of the temperature, the stress and the ultrasonic waves, and the oil film thickness measurement precision can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of face gear oil film measurement, and in particular relates to a face gear oil film thickness measurement device and method. Background Art

[0002] Face gears have been widely used in the torque splitting configuration scheme of helicopter main reduction transmission systems. Compared with spiral bevel gear mechanisms, they can reduce weight by about 40%, and their load-bearing capacity, vibration and noise performance are significantly improved. Due to the large workload, high speed, high heat generation and poor heat dissipation conditions, face gears often operate in a mixed lubrication state and are prone to tooth surface bonding, wear and contact fatigue losses due to poor tooth surface lubrication. Oil film thickness is an important parameter used to evaluate the lubrication performance of the friction contact area of ​​the gear tooth surface. Compared with full lubrication, when the two contact surfaces are completely separated by the lubricating oil film, some rough peaks on the mixed lubrication surface appear in direct contact. Therefore, there is a large friction force and extremely high flash temperature on the contact tooth surface. How to accurately measure the dynamic oil film thickness of face gears has become a problem that needs to be solved urgently.

[0003] Common oil film thickness measurement methods mainly include resistance method, capacitance method, ultrasonic method and optical interference method. Among them, the resistance and capacitance method has low measurement accuracy, and the traditional optical interference method has a harsh measurement environment and requires a good light-transmitting environment, which is difficult to achieve during gear meshing. Ultrasonic measurement technology uses the characteristics of ultrasonic reflection and transmission at the interface of different media. By analyzing the frequency and speed changes of the reflected wave and combining the acoustic impedance and density of the medium material, the oil film thickness can be accurately calculated, which has the advantages of non-contact and high precision.

[0004] However, since the tooth surface of the face gear pair has a unique and complex geometric shape and meshing point distribution, the traditional ultrasonic-based oil film thickness measurement device is difficult to apply to the face gear pair structure, and the oil film thickness measurement accuracy is low. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a device and method for measuring the oil film thickness of a face gear, so as to improve the accuracy of measuring the oil film thickness of the face gear.

[0006] In a first aspect, the present invention provides a face gear oil film thickness measuring device, the face gear oil film thickness measuring device comprising a fixed face gear, a spur gear, an ultrasonic probe and a fiber grating array sensor;

[0007] The tooth surface of the fixed face gear meshes with the tooth surface of the spur gear, a blind hole perpendicular to the meshing surface is provided on the fixed face gear, the opening of the blind hole is located on the back of the fixed face gear, the ultrasonic probe is embedded in the blind hole, the ultrasonic probe is tightly fitted with the inner wall of the blind hole, and there is a cavity between the ultrasonic probe and the bottom of the blind hole, the fixed face gear is fixedly arranged above the spur gear, and the fixed face gear and the spur gear are connected by a vertical gear transmission;

[0008] The fiber grating array sensor is fixedly arranged in the tooth groove corresponding to the meshing surface of the fixed face gear and the spur gear.

[0009] Optionally, the material of the fixed face gear and the spur gear is stainless steel.

[0010] Optionally, the transmitting beam angle of the ultrasonic probe is controlled within 15°.

[0011] Optionally, the depth of the cavity is 3 mm.

[0012] Optionally, the distance from the bottom of the cavity to the mating surface is the wavelength of the ultrasonic wave emitted by the ultrasonic probe.

[0013] Optionally, the inner diameter of the cavity is less than 5 mm.

[0014] In a second aspect, the present invention provides a gear oil film thickness measurement method, which is applied to the above-mentioned face gear oil film thickness measurement device, and the method comprises:

[0015] Obtain the thickness of the steel layer between the meshing surface of the fixed face gear and the bottom of the cavity;

[0016] Controlling the ultrasonic probe to send ultrasonic waves, and calculating the original oil film thickness of the meshing surface of the fixed face gear and the spur gear according to the thickness of the steel layer and the frequency and speed of the reflected wave received by the ultrasonic probe;

[0017] Fiber Bragg grating array sensors are used to obtain the temperature and strain of the mating surface;

[0018] The original oil film thickness, temperature and strain are input into a pre-trained oil film thickness prediction model for predicting the oil film thickness to obtain a predicted value of the oil film thickness of the meshing surface.

[0019] Optionally, the oil film thickness prediction model is used to correct the original oil film thickness according to the temperature and strain to obtain a predicted value of the oil film thickness.

[0020] Optionally, the oil film thickness prediction model is a multi-layer perceptron model.

[0021] The beneficial effects of the present invention are:

[0022] The face gear oil film thickness measuring device provided by the present invention comprises a fixed face gear, a spur gear, an ultrasonic probe and a fiber grating array sensor, wherein the fixed face gear and the spur gear are meshed with each other and connected by a vertical gear transmission, and a blind hole for placing the ultrasonic probe is also provided on the back of the fixed face gear perpendicular to the meshing surface. On the one hand, the ultrasonic probe embedded in the blind hole can detect the oil film thickness on the meshing surface at a close distance without affecting the meshing rotation of the gears, which is beneficial to improving the accuracy of the oil film thickness measurement; on the other hand, the fiber grating array sensor located in the tooth groove corresponding to the meshing surface can also synchronously monitor the temperature and stress on the meshing surface, and can measure the oil film thickness on the meshing surface from the coordinated perspective of temperature, stress and ultrasonic wave, which is beneficial to improving the accuracy of the oil film thickness measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of a device for measuring the oil film thickness of a face gear in one embodiment of the present application;

[0024] Figure 2 This is a schematic diagram of the structure of a surface gear oil film thickness measuring device located in a vehicle differential in another embodiment of the present application;

[0025] Figure 3 This is a flow chart of a method for measuring oil film thickness of a face gear in one embodiment of the present application. DETAILED DESCRIPTION

[0026] The invention discloses a device and a method for measuring the oil film thickness of a face gear.

[0027] The face gear oil film thickness measuring device provided by the present invention is exemplarily described below.

[0028] Figure 1 FIG. 1 shows the structure of a device for measuring the oil film thickness of a face gear according to an embodiment of the present invention. Figure 1 It can be seen that the face gear oil film thickness measuring device includes a fixed face gear 101 , a spur gear 102 , an ultrasonic probe 103 and a fiber grating array sensor 104 .

[0029] The tooth surface of the fixed face gear 101 meshes with the tooth surface of the spur gear 102. The fixed face gear 101 is provided with a blind hole 1011 perpendicular to the meshing surface, the opening of the blind hole 1011 is located on the back of the fixed face gear 101, the ultrasonic probe 104 is embedded in the blind hole 1011, the ultrasonic probe 103 is tightly fitted with the inner wall of the blind hole 1011, and there is a cavity 1012 between the ultrasonic probe 103 and the bottom of the blind hole 1011, as shown in FIG. Figure 2The fixed face gear 101 is fixedly arranged above the spur gear 102, and the fixed face gear 101 and the spur gear 102 are connected by a vertical gear transmission. The fixed face gear 101 and the spur gear 102 are made of stainless steel.

[0030] It should be understood that a vertical gear transmission connection generally refers to two mutually perpendicular gears, located on vertical axes, which convert torque and rotational motion into vertical transmission through a transmission shaft.

[0031] In the embodiment of the present invention, the fixed face gear 101 is fixedly arranged above the spur gear 102 and does not rotate with the spur gear 102, which is beneficial for the ultrasonic probe 103 to measure the oil film thickness. In the embodiment of the present invention, the transmitting beam angle of the ultrasonic probe is controlled within 15°.

[0032] The fiber grating array sensor 104 is used to obtain the temperature and strain of the meshing surface, and is fixedly disposed in the tooth groove corresponding to the meshing surface of the fixed face gear 101 and the spur gear 102 .

[0033] Exemplarily, in one embodiment of the present invention, the structure consisting of the fixed face gear 101 and the spur gear 102 is a part of a vehicle differential.

[0034] Figure 2 Figure 2 shows a structure of a car differential. Figure 2It can be seen that the automobile differential includes a first face gear 201, a spur gear 202, a second face gear 203 and a drive unit. The drive unit includes a drive motor 2041, a drive shaft 2042, a first spiral bevel gear 2043, a second spiral bevel gear 2044, a loading shaft 2045, a loading mechanism 2046 and a fixing rod. The gear axis of the first spiral bevel gear 2043 is provided with a first through hole. One end of the drive shaft 2042 is inserted into the first through hole and fits tightly with the inner wall of the first through hole. The other end of the drive shaft 2042 is connected to the drive motor 2041. The tooth surface of the first spiral bevel gear 2043 is meshed with the tooth surface of the second spiral bevel gear 2044. The first spiral bevel gear 2043 and the second spiral bevel gear 2044 are connected by a vertical gear transmission. The gear axis of the second spiral bevel gear 2044 is provided with a second through hole. The loading shaft 2045 is provided with a loading mechanism 2046 and a fixing rod. One end of the loading shaft 2045 passes through the second through hole and extends upward to be inserted into the third through hole opened on the gear axis of the second face gear 203. The other end of the loading shaft 2045 is connected to the loading mechanism 2046. The loading shaft 2045 is tightly fitted with the inner wall of the second through hole and the inner wall of the third through hole. The fixing rod includes a first fixing rod 2047A and a second fixing rod 2047B. The first fixing rod 2047A and the second fixing rod 2047B are vertically fixedly connected. The bottom end of the first fixing rod 2047A is fixedly connected to the root surface of the second spiral bevel gear 2044. The top end of the second fixing rod 2047B is inserted into the fourth through hole opened on the gear axis of the spur gear 202. The top end of the second fixing rod 2047B is tightly fitted with the inner wall of the fourth through hole.

[0035] The tooth surface of the second face gear 203 meshes with the tooth surface of the spur gear 202 . The second face gear 203 is fixedly disposed below the spur gear 202 , and the second face gear 203 and the spur gear 202 are also connected by vertical gear transmission.

[0036] The tooth surface of the first face gear 201 and the tooth surface of the second face gear 203 are arranged opposite to each other. Under the action of the driving unit, the second face gear 203 rotates, driving the spur gear 202 to move around the tooth surface of the first face gear 201. When the second face gear 203 is covered with lubricating oil, the tooth surface of the spur gear 202 will also be attached with lubricating oil due to the meshing of the second face gear 203 and the tooth surface of the spur gear 202. When the second face gear 203 is meshing and contacting with the spur gear 202, the oil film thickness represents the intermediate thickness that separates the two tooth surfaces and prevents them from directly frictionally contacting each other. This contact oil film is the same relative to the two tooth surfaces.

[0037] In order to accurately measure the oil film thickness on the meshing surface of the first face gear 201 and the spur gear 202, a blind hole perpendicular to the meshing surface can be provided on the first face gear 201, and the opening of the blind hole is located on the back of the first face gear 201. The ultrasonic probe is embedded in the blind hole, and the ultrasonic probe is tightly fitted to the inner wall of the blind hole. There is a cavity between the ultrasonic probe and the bottom of the blind hole, and a fiber grating array sensor is placed in the tooth groove corresponding to the meshing surface of the first face gear 201 and the spur gear 202 to obtain the temperature and stress of the meshing surface, that is, the face gear oil film thickness measuring device provided by the present application.

[0038] In order to improve the accuracy of oil film thickness measurement, in the embodiment of the present invention, the depth of the cavity is set to 3 mm, and the distance from the bottom of the cavity to the meshing surface is set to 1 / 2 of the wavelength of the ultrasonic wave emitted by the ultrasonic probe. The inner diameter of the cavity is less than 5 mm. The distance from the bottom of the cavity to the mating surface is set to be the wavelength of the ultrasonic wave emitted by the ultrasonic probe. It can reduce the interference of the steel layer thickness between the cavity bottom and the meshing surface on the sound wave propagation and improve the accuracy of oil film thickness measurement. The cavity can act as a buffer zone to improve the coupling efficiency between the ultrasonic probe and the steel layer and reduce reflection loss.

[0039] The gear oil film thickness measurement method provided by the present invention is described below.

[0040] The gear oil film thickness measurement method is applied to the above-mentioned face gear oil film thickness measurement device, such as Figure 3 As shown, the specific steps include:

[0041] Step 31, obtaining the thickness of the steel layer between the meshing surface of the fixed face gear and the bottom of the cavity.

[0042] Specifically, without introducing lubricating oil, fill the cavity of the blind hole of the fixed face gear with water, and transmit ultrasonic waves to first pass through the water layer in the groove, and then pass through the steel layer of the fixed face gear and the steel layer of the spur gear, so as to obtain the thickness of the steel layer between the meshing surface and the bottom of the cavity. A precision distribution system is used to control the amount of water to avoid excessive water injection, and water is carefully injected into the groove of the end face gear. Monitor the water injection process to ensure that cavitation is not formed, and use a boron mirror or similar inspection tool when necessary. Align the ultrasonic probe completely with the water injection area of ​​the gear, start the ultrasonic pulse emission when the gear is stationary, record the flight time data of these initial pulses and bring them into the analysis model calculation to establish a baseline measurement value of the combined thickness of the water and steel layers under static conditions.

[0043] It should be noted that, in another embodiment of the present invention, before performing step 31, a non-residual solvent suitable for the gear material is used to ensure surface cleanliness. The gear is thoroughly dried to avoid mixing of the solvent with the fluorescent material or water. In order to better fit the distribution characteristics of the meshing contact points of the face gear, a thin layer of high-contrast non-invasive fluorescent material is applied to the surface of the spur gear to identify the critical contact area on the fixed face gear during meshing operation; the gear is operated at a low speed under no-load conditions, so that the fluorescent material on the spur gear marks the actual contact track on the fixed face gear when the gear is meshed; a high-resolution imaging device (such as an ultraviolet camera) is used to capture the fluorescent track indicating the meshing contact area; the captured image is processed using image analysis software to digitize and map the precise contact area; the processed image is converted into a digital map representing the gear tooth contact area using CAD software; the digital map is analyzed to determine the center point of the contact track; this conversion should maintain the proportion and scale of the gear system to ensure the accurate arrangement of the ultrasonic probe. After obtaining the arrangement position of the ultrasonic probe, the fixed face gear is adjusted so that the meshing surface of the fixed face gear and the spur gear is located in this area.

[0044] Step 32, controlling the ultrasonic probe to send ultrasonic waves, and calculating the original oil film thickness of the meshing surface of the fixed face gear and the spur gear according to the thickness of the steel layer and the frequency and speed of the reflected wave received by the ultrasonic probe.

[0045] Specifically, the ultrasonic wave emitted at this time will pass through the water layer, the fixed face gear steel layer (steel layer thickness), the lubricating oil film, and the spur gear steel layer at once. According to the obtained steel layer thickness, the lubricating oil film thickness can be calculated. For example, the original oil film thickness of the meshing surface can be obtained by using the known water layer thickness and steel layer thickness and subtracting the propagation time of the ultrasonic wave in each layer.

[0046] Step 33, using a fiber grating array sensor to obtain the temperature and strain of the meshing surface.

[0047] Specifically, for strain measurement, the range is ±5000με, the accuracy is ±1με, and the sensitivity coefficient is 1-2pm / με. For temperature measurement, the range is -55-200°C, the accuracy is ±1°C, and the sensitivity coefficient is 10-15pm / °C.

[0048] It is worth mentioning that the fiber grating array sensor can be arranged by surface pasting or external fixing, and it occupies a small space. Compared with the traditional embedded thermocouple measurement method, it can avoid the influence of processing on the working state of gear meshing and is more in line with the actual working conditions; and the arrangement position can be to the top gap, and the measurement data obtained is closer to the core area of ​​meshing. It is conducive to improving the accuracy of oil film thickness measurement.

[0049] Step 34 , inputting the original oil film thickness, temperature and strain into a pre-trained oil film thickness prediction model for predicting the oil film thickness, and obtaining a predicted value of the oil film thickness of the meshing surface.

[0050] The above oil film thickness prediction model is a multi-layer perceptron model. The oil film thickness prediction model is used to correct the original oil film thickness according to temperature and strain to obtain the predicted value of the oil film thickness.

[0051] The pre-training process of the oil film thickness prediction model is explained below.

[0052] Exemplarily, multiple groups of training data are first collected, each group of training data consists of temperature, strain and oil film thickness measurement values; then, a multilayer perceptron model is used as a prediction model, and the multiple groups of training data are respectively input into the multilayer perceptron model, and the mean square error is used as the loss function to optimize the model parameters of the multilayer perceptron model until the difference between the prediction result of the multilayer perceptron model and the oil film thickness measurement value is less than a preset difference threshold, thereby obtaining a pre-trained oil film thickness prediction model.

[0053] At this time, the collected original oil film thickness, temperature and strain are input into the pre-trained oil film thickness prediction model to obtain an accurate oil film thickness prediction value.

[0054] It is worth mentioning that the traditional oil film thickness measurement system usually only focuses on the oil film thickness data, fails to comprehensively consider the impact of temperature and strain on the oil film thickness measurement, and is difficult to fully reflect the lubrication status of the tooth surface. The present invention obtains oil film thickness data in real time through an ultrasonic oil film thickness measurement device, and uses a fiber grating array sensor to monitor the temperature and strain of the tooth surface in real time, which can provide more comprehensive and accurate measurement data. Through multi-parameter collaborative measurement and comprehensive analysis, a comprehensive lubrication characteristic analysis is provided, the lubrication status of the tooth surface under different working conditions is evaluated, and reliable data support is provided for the optimization design and fault prevention of the gear transmission system.

[0055] In another embodiment of the present application, the face gear oil film thickness measurement method provided by the present invention is compared with the traditional capacitance resistance method. The results show that the capacitance resistance method usually measures the oil film thickness with an accuracy of 1 micron, while the face gear oil film thickness measurement method provided by the present invention has an accuracy of up to 0.01 micron when the static plane is used as the object. For the face gear dynamic meshing measurement environment, the face gear oil film thickness measurement method provided by the present invention has an accuracy of up to 0.1 micron.

[0056] It should be noted that temperature and stress are parameters that directly reflect the instantaneous lubrication state, and are also key factors that directly affect the oil film thickness. For example, at the same speed, different temperatures and stresses will also lead to different oil film thicknesses. Therefore, if the temperature and stress data are not captured at the same time, and only the oil film thickness is captured correspondingly under different operating parameters, its analytical significance will be greatly reduced. Based on ultrasonic probes and fiber grating array sensors, the data of these three at multiple points on the tooth surface can be captured simultaneously, which can better grasp the corresponding relationship and change law between the tooth surface oil film and the lubrication state, and facilitate the analysis of the minimum oil film thickness and meshing danger area from multiple scales of time and position, which can be used as input parameters for optimization design and fault warning in the future.

[0057] It can be seen from the above content that the face gear oil film thickness measuring device provided by the present invention includes a fixed face gear, a spur gear, an ultrasonic probe and a fiber grating array sensor, wherein the fixed face gear and the spur gear are meshed with each other and connected by a vertical gear transmission, and a blind hole for placing the ultrasonic probe is also opened on the back of the fixed face gear perpendicular to the meshing surface. On the one hand, the ultrasonic probe embedded in the blind hole can detect the oil film thickness on the meshing surface at a close distance without affecting the meshing rotation of the gears, which is beneficial to improving the accuracy of the oil film thickness measurement; on the other hand, the fiber grating array sensor located in the tooth groove corresponding to the meshing surface can also synchronously monitor the temperature and stress on the meshing surface, and can measure the oil film thickness of the meshing surface from the coordinated perspective of temperature, stress and ultrasonic wave, which is beneficial to improving the accuracy of the oil film thickness measurement.

[0058] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0059] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A device for measuring the oil film thickness of a face gear, characterized in that: Includes fixed face gears, spur gears, ultrasonic probes, and fiber grating array sensors; The tooth surface of the fixed face gear meshes with the tooth surface of the spur gear, the fixed face gear is provided with a blind hole perpendicular to the meshing surface, the opening of the blind hole is located on the back of the fixed face gear, the ultrasonic probe is embedded in the blind hole, the ultrasonic probe is tightly fitted with the inner wall of the blind hole, and there is a cavity between the ultrasonic probe and the bottom of the blind hole, the fixed face gear is fixedly arranged above the spur gear, and the fixed face gear and the spur gear are connected by a vertical gear transmission; The fiber grating array sensor is fixedly arranged in a tooth groove corresponding to the meshing surface of the fixed face gear and the spur gear.

2. The face gear oil film thickness measuring device according to claim 1, characterized in that: The fixed face gear and the spur gear are made of stainless steel.

3. The face gear oil film thickness measuring device according to claim 1, characterized in that: The transmitting beam angle of the ultrasonic probe is controlled within 15°.

4. The face gear oil film thickness measuring device according to claim 1, characterized in that: The depth of the cavity is 3 mm.

5. The face gear oil film thickness measuring device according to claim 1, characterized in that: The fiber grating array sensor does not come into contact with the gears of the spur gear.

6. The face gear oil film thickness measuring device according to claim 1, characterized in that: The distance from the bottom of the cavity to the meshing surface is the wavelength of the ultrasonic wave emitted by the ultrasonic probe.

7. The face gear oil film thickness measuring device according to claim 1, characterized in that: The inner diameter of the cavity is less than 5 mm.

8. A method for measuring gear oil film thickness, characterized in that: Applied to the face gear oil film thickness measuring device according to any one of claims 1 to 7, the method comprises: Obtain the thickness of the steel layer between the meshing surface of the fixed face gear and the bottom of the cavity; Controlling the ultrasonic probe to send ultrasonic waves, and calculating the original oil film thickness of the meshing surface of the fixed face gear and the spur gear according to the thickness of the steel layer and the frequency and speed of the reflected wave received by the ultrasonic probe; Using a fiber grating array sensor to obtain the temperature and strain of the meshing surface; The original oil film thickness, the temperature and the strain are input into a pre-trained oil film thickness prediction model for predicting oil film thickness to obtain a predicted value of the oil film thickness of the meshing surface.

9. The gear oil film thickness measurement method according to claim 8, characterized in that: The oil film thickness prediction model is used to correct the original oil film thickness according to the temperature and the strain to obtain the predicted value of the oil film thickness.

10. The gear oil film thickness measurement method according to claim 8, characterized in that: The oil film thickness prediction model is a multi-layer perceptron model.

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