CN106872309A - Method for measuring viscosity of micro sliding block surface contact lubricating oil - Google Patents

Abstract

The invention belongs to the technical field of viscosity measurement of lubricating oil, and relates to a method for measuring the viscosity of lubricating oil in contact with the surface of a miniature slider, which is mainly carried out according to the following steps: (1) cleaning of the sample; Flat glass disc; (3), fixed contact sub-inclination angle α is a constant value; (4), balance and application of load; (5), draw lubricating oil viscosity η with the change curve figure of outlet oil film thickness h; The present invention utilizes The method of controlling a single variable measures the oil film thickness of several lubricating oils with known viscosities, and finds out the functional relationship between film thickness and viscosity. This invention can indirectly obtain the viscosity of lubricating oil while measuring the thickness of the oil film. There is no need to use a viscometer to measure the viscosity, which saves working time and provides convenience for guiding the research of lubricating oil. Its principle is simple and reliable, easy to operate, and has high measurement accuracy. It can be applied to the measurement of the viscosity of different types of lubricating oils and is environmentally friendly. ,Market prospects.

Description

A Method for Measuring the Viscosity of Lubricating Oil Contacted by Miniature Sliding Blocks

Technical field:

The invention belongs to the technical field of lubricating oil viscosity measurement, and relates to a method for measuring the viscosity of lubricating oil, in particular to a method for measuring the viscosity of lubricating oil in contact with the surface of a miniature slider. Indirect measurement of lubricating oil viscosity.

Background technique:

The viscosity of lubricating oil is one of the most important physical properties in hydrodynamic lubrication. It is not only an important index for evaluating oil products, but also one of the important factors involved in studying various properties of lubricating oil. At present, there are many methods for measuring the viscosity of lubricating oil in experiments, and the commonly used methods are as follows:

1. Capillary method

Measurement principle: According to the Hagen-Poiseuille law, the time required for a certain volume of liquid to pass through a given capillary under a certain pressure gradient is proportional to the viscosity of the laminar flow liquid. Therefore, by measuring the liquid flow rate and the pressure difference generated by the liquid flowing through the capillary. Find the viscosity of the liquid;

Measurement method: The method used in the experiment is to calculate η by measuring the time for a certain volume of lubricating oil to flow through the capillary. The flow Q through the thin tube is thus get Among them: the volume flowing through the capillary in Vt; R-the radius of the capillary; L-the length of the capillary; P-the pressure difference at both ends of the capillary. This is the Posseler formula, but it is based on the ideal formula and must be corrected. Finally: Among them: m-kinetic energy correction coefficient; n-terminal correction coefficient, its value is between 0 and 1.2; ρ-is the fluid density.

The advantage of this method is that the capillary viscometer is easy to manufacture, low in price, simple in temperature control, convenient in experimental operation, high in measurement accuracy, and capable of absolute measurement of viscosity, so the capillary method is an attractive measurement method, but the method The capillary in the method is easily blocked by small particles, so the requirement for sample purity is high, and because the sample is easy to react with the capillary, it is not suitable for use at high temperature.

2. Rotation method

Rotary viscometers are mainly divided into two types in terms of structure: single-cylinder rotary viscometers and double-cylinder rotary viscometers. Double-cylinder rotary viscometers have two cylinders, which can be divided into inner cylinders There are two types: rotary type and outer cylinder rotary type.

Working principle: The single-cylinder rotary viscometer has only one cylinder, and a miniature synchronous motor drives the upper and lower discs to rotate together with the cylinder. Due to the viscous force of the fluid, the cylinder and the cylinder The rotation of the rigidly connected lower plate will lag behind the upper plate, so that the elastic element will be twisted. By measuring this twist, the viscous moment M on the small cylinder can be obtained, and then the viscosity of the fluid can be calculated according to the Max formula: In the formula: η—liquid dynamic viscosity, Pa s; H—measuring the height of the small cylinder immersed in the liquid to be measured; R _f —the radius of the small cylinder; R _a the radius of the liquid container to be measured; M—viscous moment ; Ω—the rotational angular velocity of the small cylinder.

When measuring with an inner cylinder rotary viscometer, the outer cylinder is a container for the liquid to be measured, which is fixed, and the inner cylinder is a hollow cylinder immersed in the fluid to be measured and rotated, coaxial with the outer cylinder. The shell of the miniature synchronous motor used for driving is installed in a suspended type, and the inner cylinder is driven to rotate at a certain speed through the rotating shaft. body deflection, the motor casing is connected with two metal hairsprings installed one positive and the other reversely installed, when the casing deflects, the hairspring will be twisted, and when the torque of the hairspring and the viscous resistance torque reach a balance, it will be connected with the motor casing The pointer will indicate a certain value on the dial. This value is proportional to the viscous resistance experienced by the drum. Therefore, the scale reading is multiplied by a specific coefficient F (that is, the drum factor), which is expressed as the value of the viscosity coefficient.

When measuring the external cylinder rotary viscometer, both the inner and outer cylinders are immersed in the measured fluid, and the motor drives the outer cylinder to rotate at a certain speed. Due to the viscosity of the measured fluid between the two cylinders, the inner cylinder The deflection occurs due to the action of the hysteresis force, and the restoring moment generated by the torsion of the wire connected to the inner cylinder is opposite to the direction of the viscous moment. When the restoring moment and the viscous moment of the tensioning wire are balanced, the deflection angle θ The size is proportional to the viscosity coefficient η that causes the viscous moment. From this, the functional relationship [η=f(θ)] between the viscosity coefficient η and the deflection angle θ is derived, and the value of the viscosity coefficient η can be calculated by measuring the deflection angle θ of the inner cylinder.

The advantage of this method is that the single-cylinder rotary viscometer has a simple structure and is easy to install, so it is suitable for on-line measurement of fluid viscosity. At the same time, the single-cylinder rotary viscometer has high measurement accuracy, fast response speed, and low It is an ideal online viscometer, which is convenient for monitoring and controlling the product viscosity at any time during the production process. The inner cylinder rotary viscometer is the most common rotary viscometer. From its structure and operation mode, it is mainly used for off-line measurement of fluid viscosity, such as measuring the viscosity value of sampled fluid in the laboratory. The external cylinder rotary viscometer is the same as the single-circle rotary viscometer, and it is very troublesome to read directly and calculate manually.

3. Vibration measurement

There are many measurement methods of vibration method, such as torsional vibration type, vibrating plate type, etc. The commonly used one is torsional vibration type measurement, including damping vibration type and forced vibration type.

Measuring principle: The attenuation vibration method is based on the torsional vibration of the object immersed in lubricating oil. Due to the viscous force exerted by the lubricating oil, the torsional amplitude will attenuate. After measuring the amplitude attenuation and attenuation period, the liquid viscosity can be calculated through the corresponding formula. The measurement principle of the forced vibration type is to supplement the energy lost by the vibrating object due to the viscosity from the outside, so that the vibrating object maintains a constant vibration frequency and amplitude, and the viscosity value is calculated from the relationship between the added energy and the viscosity of the lubricating oil.

The advantage of this method is that the vibration method is often used in the viscosity measurement of low-viscosity liquids, so this method is mainly suitable for the viscosity measurement of most melts. The advantages of the vibration method are that the vibration period and attenuation measurement are convenient, the sample consumption is small, and the temperature control is convenient, but There is no generally accepted formula for calculating ideal viscosity.

4. Drop ball method

Measuring principle: The sphere or cylinder falls in the measured liquid, and the viscosity is measured by measuring the time it takes for the falling body to pass through two fixed points, or the sphere can be rolled through an inclined plane.

The advantage of this method is that the falling ball method can measure the absolute viscosity in principle. Since the viscosity coefficients of different liquids vary greatly, and the viscosity coefficient of the same liquid varies greatly with different temperatures, the small ball should also be considered. The scale ratio of diameter to volume must meet the requirements of the experiment, therefore, the diameter range of the small balls that meet the experimental conditions will also vary. Due to the adoption of manual stop watch timing and due to the impact of people's visual persistence effect, the speed of the ball falling will be as slow as possible. Viscometers using the same principle include rolling falling ball viscometer, cylindrical falling viscometer and falling continuous viscometer.

Therefore, a method for measuring the viscosity of lubricating oil in contact with the surface of a miniature slider is designed and prepared. This method is based on the miniature slider bearing lubricating oil film measuring instrument and its slider adjustment method (patent number ZL200810249672.0) designed and developed by Qingdao University of Technology. Based on the experimental equipment, it can set and adjust the inclination α between the working plane of the micro-slider and the transparent optical disc, which provides the experimental hardware basis for the surface contact lubricant viscosity measurement method.

Invention content:

The purpose of the present invention is to overcome the shortcomings of the prior art, and seek to design a new method for measuring the viscosity of lubricating oil in contact with the surface of a miniature slider. Form a low-pressure fluid dynamic pressure lubricating oil film, and use optical interference technology to measure the thickness of the lubricating oil film. According to the theory of hydrodynamic pressure lubrication, the higher the viscosity of the lubricating oil, the greater the thickness of the oil film. By measuring the thickness of the oil film of part of the lubricating oil, find the film The functional relationship between thickness and viscosity, and then indirectly obtain the viscosity of lubricating oil at any film thickness.

In order to achieve the above object, the method for measuring the viscosity of lubricating oil in contact with the surface of the miniature slider of the present invention is completed in a miniature slider bearing lubricating oil film measuring instrument, and its main structure includes: a slider fixing unit, a glass disk rotating unit, Interference system, loading device and rack chassis; the main components of the slider fixing unit include micro-sliders, the main components of the glass disc rotation unit include glass discs, the main components of the light interference system are coaxial lighting equipment and the Microscope, the main components of the loading device are the loading lever and the adjusting screw; the surface contact lubrication pair is composed of an optically transparent glass disc and a miniature slider, the slider is fixed above the glass disc, and the slider is used as the upper surface of the lubrication pair. Surface high-precision reflective treatment, the glass disc is the lower surface, the glass disc rotates, the slider is stationary, the inclination angle between the slider and the surface of the glass disc can be changed by the tilt angle adjustment device, the number of light interference fringes and the inclination angle of the fringes can reflect The inclination angle between the micro-slider and the glass plate can be adjusted by adjusting the adjusting screw at different positions to change the number and inclination angle of interference fringes, thereby achieving the purpose of changing the size and direction of the inclination angle, and maintaining the inclination angle during the rotation of the glass plate. The size and direction of the inclination angle do not change, so as to ensure the stability of the experiment; the load is applied to the two planes by the loading device, and when the glass disk rotates at a certain angular speed, the lubricating oil is sucked into the two planes to form a lubricating oil film, and the thickness of the oil film is determined by Measured by the optical interferometry system under the glass disk, the system uses multi-beam interferometry to calculate the thickness of the oil film. After multiple projections and reflections, the coherent light beam forms light and dark interference fringes corresponding to the contact area, and the thickness of the oil film in the contact area is inferred from the intensity and polarity of the interference fringes. The specific measurement method is carried out as follows:

(1) Cleaning of the sample:

Before the start of the test, the micro-slider (L-length, B-width) and the glass disc are cleaned to prevent the adsorption of fine particles from causing inaccurate measurement of the lubricating oil film thickness. The specific process steps are to first clean the micro-slider Use hand sanitizer to remove oil stains and other impurities on the surface, and in special cases where the oil stains are not easy to remove, use acetone, petroleum ether or other strong organic solvents to clean; Ultrasonic cleaning in water and ethanol for 3-5 minutes, and finally dry the cleaned micro-slides and glass discs with high-pressure nitrogen or compressed air;

(2), install the micro-slider, install and level the glass plate:

First install the miniature slider on the miniature slider bearing lubricating oil film measuring instrument, and then install the glass plate. When installing the glass plate, turn the 8 positioning screws on its surface in turn until they are slightly tightened. During installation, the glass plate should be prevented from being damaged and damaged. To avoid contamination of the surface of the glass disc, the surface contact pair is composed of a micro-slider and a glass disc. Add the lubricating oil to be tested on the glass disc to determine the dynamic viscosity η and refractive index n of the lubricating oil to be tested, where the dynamic viscosity η of the lubricating oil is Measured by a viscometer, the refractive index n of the lubricating oil to be tested is determined by an Abbe refractometer; then, use a dial gauge to level the glass disc so that the runout of the end face is within 3 μm;

(3) The inclination angle α of the fixed contact pair is a constant value:

The red light with a wavelength of λ enters the microscope through the coaxial lighting device and irradiates on the wedge-shaped gap formed by the micro-slider and the glass disc to form an interference image. The number N of interference image fringes is determined by adjusting 8 adjustment screws, and the inclination angle is calculated by the formula Determine the inclination angle α between the micro-slider and the glass plate at this time; fine-tune the 8 positioning screws on the pressure ring to control the dynamic balance of the inclination angle so that the inclination angle does not change during the rotation process, where α is the micro-slider Inclination angle, rad; λ is the wavelength of the light source, m; N is the number of stripes; n is the refractive index of the lubricating medium; B is the width of the micro-slider, m;

(4), load balance and application:

The self-weight of the entire load can be balanced by adjusting the spring. Generally, it is considered that the balance of the self-weight is completed when the interference image is present or absent, and then the load w required by the experiment is applied, and the load applied during the experiment is fixed;

(5), draw the curve graph that the lubricating oil viscosity η at the outlet changes with the oil film thickness h:

The interference image formed in the above step (3) is enlarged and projected onto the CCD (image controller) through the microscope, and the enlarged interference image is displayed on the computer screen through the processing of the CCD and the image acquisition card; the enlarged interference image is processed and converted into light intensity Curve, the interference order is obtained from the light intensity curve, and the lubricating oil film thickness h at the outlet is calculated by using the relationship between the interference order and the lubricating oil film thickness; the included angle α=α ₁ of the contact pair, the speed u _d =u ₁ , under the condition of load w=w ₁ , measure the oil film thickness of several lubricating oils with known viscosities, and then use origin or other function drawing software to draw the viscosity η with oil film The change curve of the thickness h, and then draw the fitting curve, and finally calculate the viscosity calculation formula according to the above-mentioned known data relationship:

η ₀ =10 ^χ

χ=2.15062·logh+1.71367.

Further, the glass disc is a K9 glass disc, and the glass disc is plated with chrome film and silicon dioxide film (Cr+SiO ₂ ) on one side of the working surface to obtain clear interference fringes while controlling the reflectivity at 18 -22% or so to ensure the contrast of interference fringes, the surface roughness R _a is 4nm.

Further, the size of the micro-slider used is 4×4mm, the working surface of the micro-slider is a high-reflectivity precision polishing surface, the surface roughness is _Ra = 8-10nm, and the test is carried out in a controlled environment. The temperature is controlled at 20±0.5°C, and the humidity is controlled at 30±5%.

Compared with the prior art, the present invention uses the method of controlling a single variable, fixes the rotation speed u _d of the glass disc, the inclination angle α of the slider, and the applied load w, and measures the oil film thickness of several lubricating oils with known viscosities. The theory of dynamic pressure lubrication, the higher the viscosity, the greater the thickness of the oil film, find out the functional relationship between film thickness and viscosity, so that as long as it is within the range that can be measured, the lubrication under any film thickness can be known according to the obtained formula oil viscosity. This method can indirectly obtain the viscosity of the lubricating oil while measuring the thickness of the oil film. It does not need to use a viscometer to measure the viscosity of the lubricating oil, which saves workload and time, and provides convenience for guiding the research of lubricating oil. The principle is simple and reliable. The operation is convenient, the measurement accuracy is high, it can be applied to the measurement of the viscosity of different types of lubricating oils, the application environment is friendly, and the market prospect is broad.

Description of drawings:

Fig. 1 is a schematic diagram of the main body principle of the experimental device used in the present invention.

Fig. 2 is a curve diagram of the variation of lubricating oil viscosity with the oil film thickness h at the outlet under the conditions of rotation speed _ud of the fixed glass disk, slider inclination α, and applied load w in the present invention.

detailed description:

The present invention will be further described below through the embodiments and in conjunction with the accompanying drawings.

Example:

This embodiment is completed in a miniature slider bearing lubricating oil film measuring instrument, and its main structure includes a miniature slider 1, a glass disc 2, a loading lever 3, an adjustment screw 4, a beam splitter 5, a load 6, an inlet and 7, and an outlet 8 ; The glass disc 2 is used to contact the miniature slider 1 to form a surface contact pair, adjust the 8 adjusting screws 4 and the 8 positioning screws on the pressure ring to control the dynamic balance of the inclination angle, so that the inclination angle does not change during the rotation, and the load lever 3 is a part of the loading unit in the miniature slider bearing lubricating oil film measurement test bench, which is used to apply the load on the lubricated working surface, and balance the self-weight of the entire load by adjusting the spring. In this embodiment, the size of the miniature slider is 4×4mm, the applied load w=4N, the number of stripes is controlled at 10 stripes, the speed is taken as u _d =15.39mm/s, the dynamic viscosity η and refraction of the lubricating oil to be measured The rate n has been determined in advance before the experiment. The characteristics of the lubricating oil used in the measurement are shown in Table 1, and the viscosity of the lubricating oil under different oil film thicknesses is determined through experiments; the specific measurement method is carried out as follows:

(1) Cleaning of the sample:

Clean the micro-slider 1 and the glass disc 2 before the start of the test to prevent the inaccurate measurement of the lubricating oil film thickness caused by the adsorption of fine particles. The specific process steps are to first remove the slider 1 and the glass disc 2 with hand sanitizer In special cases where oil stains and other impurities on the surface are difficult to remove, use acetone, petroleum ether or other strong organic solvents to clean; then put the cleaned micro slide 1 and glass disc 2 into absolute ethanol for ultrasonic cleaning 3-5 minutes, finally use high-pressure nitrogen or compressed air to dry the cleaned micro-slide 1 and glass disc 2;

(2) Install the micro-slider, install and level the glass plate:

First install the miniature slider 1 on the lubricating oil film measuring instrument of the miniature slider 1 bearing, and then install the glass plate 2. When installing the glass plate 2, turn the 8 positioning screws on its surface in turn until slightly tightened. During installation, the glass plate should be prevented from 2 and prevent the surface of the glass plate 2 from being polluted. The surface contact pair is composed of a micro-slider 1 and a glass disc 2, and the lubricating oil to be tested is added to the glass disc 2. The dynamic viscosity and refractive index n of the lubricating oil to be tested are shown in Table 1. The dynamic viscosity η is measured by a viscometer, and the refractive index The ratio n is measured by an Abbe refractometer; then, use a dial gauge to level the glass disc 2 so that the runout of the end face is within 3 μm;

(3) The inclination angle α of the fixed contact pair is a constant value:

The red light with a wavelength of λ=650nm enters the microscope through the coaxial lighting device at the bottom of the glass disc 2 and irradiates on the wedge-shaped gap formed by the micro-slider 1 and the glass disc 2 to form an interference image; the number of interference fringes is adjusted by adjusting 8 adjustment screws. N is kept at 10, calculated by the inclination formula Determine the angle α=1:1781 of the contact pair at this time, where the refractive index n is 1.447; fine-tune the 8 positioning screws on the pressure ring to control the dynamic balance of the inclination angle, so that the inclination angle does not change during the rotation;

(4), load balance and application:

The self-weight of the entire loading is balanced by the loading lever 3 and the adjustment spring in the loading unit. When the interference fringes are present or absent, the self-weight balance is completed, and then the load w=4N is applied, and the load 6 applied during the experiment is fixed. ;

(5), drawing the change curve of lubricating oil viscosity η with the oil film thickness h at the outlet:

The interference image formed in the above step (3) is enlarged and projected onto the CCD (image controller) through the microscope, and the enlarged interference image is displayed on the computer screen through the processing of the CCD and the image acquisition card; the enlarged interference image is processed and converted into light intensity Curve, the interference order is obtained from the light intensity curve, and the lubricating oil film thickness h at the outlet is calculated using the relationship between the interference order and the lubricating oil film thickness;

Under the conditions of contact angle α=1:1781, speed u _d =15.39mm/s, and load w=4N, the oil film thickness of several lubricating oils with known viscosity is measured, and the specific values are shown in the following 1 :

Table 1M series lubricating oil characteristics (22°C)

5 pairs of data points of the experimental data M1, M2, M3, M4, M6 lubricating oil in the above table 1 are drawn with origin or other function drawing software to draw the change curve of the viscosity η with the thickness of the oil film h, and then draw the fitting curve, As shown in Figure 2, thus obtain the calculation formula (1) of viscosity:

η ₀ =10 ^χ

χ＝2.15062·logh+1.71367 (1)

Bringing the film thickness of M5 lubricating oil into the fitting function, η=151.645mPa·s, the error with the actual measured value is 3%, and the error is within the allowable range.

In order to verify the reliability of the fitting function, the characteristics of the P series lubricating oil were measured, as shown in Table 2, the theoretical viscosity η ₀ was calculated using the obtained formula (1), and the error between the measured viscosity and the theoretical viscosity was proved to be very small , within the allowable range, it proves the reliability of using the fitting function to calculate the corresponding viscosity under any film thickness.

Table 2 Characteristics of P series lubricating oil (22°C)

For the measured curve, any value can be obtained by interpolation method, as shown in Figure 2, the theoretical film thickness-viscosity curve and the experimental film thickness-viscosity curve have a good consistency in trend, and the error is within 4%. We can conclude that it is feasible to obtain the viscosity of lubricating oil indirectly by measuring the film thickness of lubricating oil.

The above is only an embodiment of the present invention, and is not intended to limit the present invention in other forms. Any skilled person who is familiar with this field may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes. . However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the present invention, as long as they do not depart from the content of the solution of the present invention.

Claims (3)

1. A method for measuring the viscosity of a miniature slider surface contact lubricating oil, the method is completed in a miniature slider bearing lubricating oil film measuring instrument, and it is characterized in that the specific measurement method is carried out as follows: (1) Cleaning of the sample: Clean the micro-slider and glass disc before the start of the test to prevent the inaccurate measurement of lubricating oil film thickness caused by the adsorption of fine particles. For impurities such as oil stains, in special cases where oil stains are not easy to remove, use acetone, petroleum ether or other strong organic solvents to clean; then put the cleaned micro-slides and glass discs into absolute ethanol for ultrasonic cleaning for 3-5 minutes , and finally dry the cleaned micro-slides and glass discs with high-pressure nitrogen or compressed air; (2), install the micro-slider, install and level the glass plate: First install the miniature slider on the miniature slider bearing lubricating oil film measuring instrument, and then install the glass plate. When installing the glass plate, turn the 8 positioning screws on its surface in turn until they are slightly tightened. During installation, the glass plate should be prevented from being damaged and damaged. To avoid contamination of the surface of the glass disc, the surface contact pair is composed of a micro-slider and a glass disc. Add the lubricating oil to be tested on the glass disc to determine the dynamic viscosity η and refractive index n of the lubricating oil to be tested, where the dynamic viscosity η of the lubricating oil is Measured by a viscometer, the refractive index n of the lubricating oil to be tested is determined by an Abbe refractometer; then, use a dial gauge to level the glass disc so that the runout of the end face is within 3 μm; (3) The inclination angle α of the fixed contact pair is a constant value: The red light with a wavelength of λ enters the microscope through the coaxial lighting device and irradiates on the wedge-shaped gap formed by the micro-slider and the glass disc to form an interference image. The number N of interference image fringes is determined by adjusting 8 adjustment screws, and the inclination angle is calculated by the formula Determine the inclination angle α between the micro-slider and the glass plate at this time; fine-tune the 8 positioning screws on the pressure ring to control the dynamic balance of the inclination angle so that the inclination angle does not change during the rotation process, where α is the micro-slider Inclination angle, rad; λ is the wavelength of the light source, m; N is the number of fringes; n is the refractive index of the lubricating medium; B is the width of the micro-slider, m; (4), load balance and application: By adjusting the spring, the self-weight of the entire load can be balanced. When the interference image is absent or not, the self-weight balance is completed, and then the load w required by the experiment is applied, and the load applied during the experiment is fixed; (5), draw the curve graph that the lubricating oil viscosity η at the outlet changes with the oil film thickness h: The interference image formed in the above step (3) is enlarged and projected onto the image controller through the microscope, and the enlarged interference image is displayed on the computer screen through the processing of the image controller and the image acquisition card; the enlarged interference image is processed and converted into a light intensity curve , the interference order is obtained from the light intensity curve, and the lubricating oil film thickness h at the outlet is calculated by using the relationship between the interference order and the lubricating oil film thickness; at the contact angle α=α ₁ , the speed u _d =u ₁ , Under the condition of load w=w ₁ , measure the oil film thickness of five kinds of lubricating oils with known viscosity; use the data points of the viscosity and oil film thickness of the measured lubricating oil to draw the change curve of viscosity η with oil film thickness h, Then draw the fitting curve, and finally calculate the viscosity calculation formula according to the above-mentioned known data relationship: η ₀ =10 ^χ χ=2.15062·log h+1.71367. 2. the measuring method of miniature slide block surface contact lubricating oil viscosity according to claim 1, it is characterized in that described glass disc is K9 glass disc, and glass disc is plated with chromium film and silica film ( Cr+SiO ₂ ), to obtain clear interference fringes, and the reflectivity of the working surface of the glass disk is 18-22%, to ensure the contrast of the interference fringes, and the surface roughness _Ra of the glass disk is 4nm. 3. the method for measuring the viscosity of the contact lubricating oil on the surface of the miniature slider according to claim 1, characterized in that the size of the miniature slider is 4 × 4mm, and the working surface of the miniature slider has a roughness of _Ra =8～10nm , The test temperature is controlled at 20±0.5°C, and the humidity is controlled at 30±5%.