Transmission active lubrication control method based on oil film thickness

Abstract

The invention discloses a transmission active lubrication control method based on oil film thickness. The transmission active lubrication control method comprises the following steps: S1, reading vehicle speed, transmission input torque and transmission initial temperature information; s2, calculating theoretical values of the minimum oil film thickness under different working conditions; the empirical value of the minimum oil film thickness is determined; s3, the lubricating oil temperature Ti and the dynamic target optimization temperature T0 at different vehicle speeds are determined; s4, the lubricating oil temperature Ti at the current vehicle speed is compared with the dynamic target optimization temperature T0, if the lubricating oil temperature Ti is larger than the dynamic target optimization temperature T0, the active lubricating control system cools the lubricating oil, and otherwise, the active lubricating system is closed; and S5, whether the difference value change rate of the lubricating oil temperature Ti and the dynamic target optimization temperature T0 is smaller than a threshold value or not is judged, if the difference value change rate is larger than or equal to the threshold value, the lubricating oil flow and the rotating speed of a cooling fan are adjusted, and otherwise, the active lubricating system stops working. The working temperature of the transmission can be effectively controlled, the working reliability of the transmission is improved, and the service life of the transmission is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of transmissions, and in particular to an active lubrication control method for a transmission based on oil film thickness. Background Art

[0002] As an important part of the transmission system, the transmission can reduce the speed and increase the torque. However, with the continuous increase in the maximum speed of the power source, higher requirements are placed on the lubrication performance of the transmission, and the lubrication and cooling issues of the transmission cannot be ignored.

[0003] At present, transmissions generally use splash lubrication, which is a passive gear lubrication and cooling method. The heat dissipation capacity of the transmission under this lubrication method is limited. Under high speed and high torque conditions, the transmission oil temperature is prone to be too high, resulting in reduced lubricating oil viscosity and reduced lubricating oil film thickness in local areas of the gear meshing tooth surface. Mixed lubrication occurs, causing tooth surface bonding or even fatigue fracture.

[0004] In order to achieve a good heat dissipation effect of the transmission, if a large flow jet lubrication is directly used to minimize the transmission temperature, the viscosity of the lubricating oil will increase, the heat generated by gear meshing, bearing friction and gear oil stirring loss during the operation of the transmission will increase, and the energy consumption of the entire system will also increase sharply. Therefore, a lubrication control method that can comprehensively consider the influencing factors of the transmission operation and select an accurate target optimization temperature is urgently needed. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides an active lubrication control method for a transmission based on oil film thickness, which fully takes into account the factor that the oil temperature of the transmission is too high under some severe working conditions, resulting in a decrease in the oil film thickness on the gear meshing tooth surface. The control method can effectively control the operating temperature of the transmission and improve the operating reliability and service life of the transmission.

[0006] In order to achieve the above object, the present invention provides a transmission active lubrication control method based on oil film thickness, comprising the following steps:

[0007] S1: Read vehicle speed, transmission input torque and transmission initial temperature information;

[0008] S2: Different operating conditions are divided according to different vehicle speeds, transmission input torques and transmission initial temperatures, and the oil film thickness under different operating conditions is calculated; based on the elastohydrodynamic lubrication theory, the empirical value of the minimum oil film thickness is determined;

[0009] S3: According to the oil film thickness at different vehicle speeds obtained in step S2, determine the lubricating oil temperature T corresponding to the vehicle speed i; According to the empirical value of the minimum oil film thickness determined in step S2, determine the dynamic target optimization temperature T0 corresponding to the vehicle speed;

[0010] S4: Compare the lubricating oil temperature T at the current vehicle speed i With the dynamic target optimization temperature T0, if the lubricating oil temperature T i If the lubricating oil temperature T is greater than the dynamic target optimization temperature T0, the radiator pump flow and fan speed are increased; if the lubricating oil temperature T i If it is less than or equal to the dynamic target optimization temperature T0, the active lubrication system is shut down;

[0011] S5: Determine the lubricating oil temperature T i Whether the difference change rate with the dynamic target optimization temperature T0 is less than the threshold. If the difference change rate is greater than or equal to the threshold, the lubrication flow and cooling fan speed are adjusted in time. If the difference change rate is less than the threshold or the vehicle stops, the active lubrication system stops working.

[0012] Further, according to the transmission active lubrication control method based on oil film thickness according to claim 1, it is characterized in that: in the step S2, the calculation formula of the film thickness of the elastohydrodynamic lubrication is:

[0013]

[0014] Among them, h(x) is the oil film thickness; h0 is the gap between the two contacting rigid bodies; x is the horizontal coordinate; R is the equivalent radius of curvature; v(x) is the elastic displacement of each point on the contact surface along the vertical direction.

[0015] Furthermore, in step S2, according to the elastohydrodynamic lubrication theory, when the fluid film becomes thinner than 0.1 μm, it begins to enter the mixed lubrication state, and the empirical value of the minimum oil film thickness is determined to be 0.1 μm. The transmission lubricating oil temperature corresponding to the empirical value of the minimum oil film thickness is the safe operating temperature.

[0016] Furthermore, in step S5, the lubricating oil temperature T i The threshold value of the rate of change of the difference from the dynamic target optimization temperature T0 is 1%.

[0017] Beneficial effects of the present invention:

[0018] Based on the elastohydrodynamic lubrication theory and the viscosity-temperature characteristics of lubricating oil, the present invention analyzes the oil film thickness of the meshing tooth surface under different working conditions, determines the dynamic target optimization temperature scheme, and thus proposes an active lubrication control method for a transmission based on oil film thickness. The method fully considers the factor that the oil temperature of the transmission is too high under some severe working conditions, resulting in a decrease in the oil film thickness on the meshing tooth surface of the gear, and can effectively control the operating temperature of the transmission, thereby improving the operating reliability and service life of the transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flow chart of a transmission active lubrication control method based on oil film thickness.

[0020] Figure 2 This is a comparison chart of the results of an active lubrication control method for a transmission based on oil film thickness according to the present invention.

[0021] Figure 3 The invention discloses a line contact elastohydrodynamic lubrication model based on oil film thickness.

[0022] Figure 4 This is a diagram showing the variation of the oil film thickness with the initial temperature in the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The invention discloses a transmission active lubrication control method based on oil film thickness.

[0025] Reference Figure 1 , a transmission active lubrication control method based on oil film thickness, comprising the following steps:

[0026] S1: Use the vehicle speed sensor to read the vehicle speed information, calculate the torque information of the transmission at the current vehicle speed, and use the temperature sensor to read the initial temperature information of the transmission.

[0027] Among them, the vehicle's driving force is calculated as follows:

[0028]

[0029] Among them, F out is the driving force of the vehicle; m is the mass of the vehicle; g is the acceleration of gravity; f is the rolling resistance coefficient; α1 is the ramp angle; δ is the rotational mass conversion coefficient; a is the vehicle acceleration; C D is the air resistance coefficient; A is the frontal area of ​​the vehicle; v is the driving speed.

[0030] The transmission input torque is calculated as follows:

[0031]

[0032] T in is the transmission input torque; i0 is the total transmission ratio of the two-stage transmission; i gis the main transmission or wheel side transmission ratio; η T is the mechanical transmission efficiency.

[0033] S2: Use SolidWorks and Romax to build transmission case and transmission gear pair models respectively, and import the transmission case model into Romax to couple it with the transmission gear pair model; in Romax software, divide different working conditions according to different vehicle speeds, transmission input torques and transmission initial temperatures, and obtain the oil film thickness under different working conditions through simulation calculations of the above three parameters; according to the elastohydrodynamic lubrication theory, when the fluid film becomes thinner than 0.1μm, it begins to enter the mixed lubrication state, and the empirical value of the minimum oil film thickness is determined to be 0.1μm, which can ensure lubrication reliability.

[0034] Among them, refer to Figure 3 , the calculation formula for the film thickness of line contact elastohydrodynamic lubrication is:

[0035]

[0036] Among them, h(x) is the thickness of the oil film; h0 is the gap between the two contacting rigid bodies; x is the horizontal coordinate; R is the equivalent radius of curvature; v(x) is the elastic displacement of each point on the contact surface along the vertical direction, and the equation is:

[0037]

[0038] Where s is an additional coordinate on the x-axis, indicating the distance between any line load p(s)ds and the origin of the coordinate system; p(s) is the load distribution function; c is a constant to be determined; x in and x out are the starting and ending coordinates of the load p(s), and the equation is:

[0039]

[0040] where b is the half-width of the Hertz contact.

[0041] S3: According to the oil film thickness at different vehicle speeds obtained in step S2, determine the lubricating oil temperature T corresponding to the vehicle speed i In order to ensure that the transmission gears do not have mixed lubrication, the safe operating temperature at different vehicle speeds is used as the target optimization temperature T0; and the safe operating temperature of the lubricating oil at different vehicle speeds is based on the minimum oil film thickness empirical value of 0.1μm in step S2, which is input into the transmission motion model in Romax and obtained by simulation calculation.

[0042] S4: Compare the current lubricating oil temperature T i and the dynamic target optimization temperature T0 at the corresponding vehicle speed. If the lubricating oil temperature T iIf the lubricating oil temperature T is greater than the dynamic target optimization temperature T0, the radiator pump flow and fan speed are increased. i If the temperature is less than or equal to the dynamic target optimization temperature T0, the active lubrication system is shut down. This method can effectively increase the heat exchange rate between the lubricating oil and the air, reduce the lubricating oil temperature, and improve the reliability of the transmission operation.

[0043] S5: Determine the lubricating oil temperature T i Whether the difference change rate with the dynamic target optimization temperature T0 is less than the threshold. After multiple tests and analyses, the lubricating oil temperature T i The threshold value of the difference change rate with the dynamic target optimization temperature T0 is 1%, which can effectively control the working temperature of the transmission, ensure the reliable operation of the transmission and reduce the calculation cost. i If the difference change rate with the dynamic target optimization temperature T0 is greater than or equal to 1%, the lubrication flow and cooling fan speed are adjusted in time. If the difference change rate is less than the threshold or the vehicle stops, the active lubrication system stops working. Figure 2 , (a) is the oil temperature of the splash lubrication transmission and the dynamic target optimized oil temperature, (b) is the oil temperature of the active lubrication transmission and the dynamic target optimized oil temperature.

[0044] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A transmission active lubrication control method based on oil film thickness, characterized in that: The following steps are involved: S1: Read vehicle speed, transmission input torque and transmission initial temperature information; S2: Different operating conditions are divided according to different vehicle speeds, transmission input torques and transmission initial temperatures, and the oil film thickness under different operating conditions is calculated; based on the elastohydrodynamic lubrication theory, the empirical value of the minimum oil film thickness is determined; S3: According to the oil film thickness at different vehicle speeds obtained in step S2, determine the lubricating oil temperature T corresponding to the vehicle speed i ; According to the empirical value of the minimum oil film thickness determined in step S2, determine the dynamic target optimization temperature T0 corresponding to the vehicle speed; S4: Compare the lubricating oil temperature T at the current vehicle speed i With the dynamic target optimization temperature T0, if the lubricating oil temperature T i If the lubricating oil temperature T is greater than the dynamic target optimization temperature T0, the radiator pump flow and fan speed are increased; if the lubricating oil temperature T i If it is less than or equal to the dynamic target optimization temperature T0, the active lubrication system is shut down; S5: Determine the lubricating oil temperature T i Whether the difference change rate with the dynamic target optimization temperature T0 is less than the threshold. If the difference change rate is greater than or equal to the threshold, the lubrication flow and cooling fan speed are adjusted in time. If the difference change rate is less than the threshold or the vehicle stops, the active lubrication system stops working.

2. The transmission active lubrication control method based on oil film thickness according to claim 1, characterized in that: In step S2, the film thickness of the elastohydrodynamic lubrication is calculated as follows: Among them, h(x) is the oil film thickness; h0 is the gap between the two contacting rigid bodies; x is the horizontal coordinate; R is the equivalent radius of curvature; v(x) is the elastic displacement of each point on the contact surface along the vertical direction.

3. The transmission active lubrication control method based on oil film thickness according to claim 1, characterized in that: In step S2, according to the elastohydrodynamic lubrication theory, when the fluid film becomes thinner than 0.1 μm, it begins to enter the mixed lubrication state, and the empirical value of the minimum oil film thickness is determined to be 0.1 μm. The transmission lubricating oil temperature corresponding to the empirical value of the minimum oil film thickness is the safe operating temperature.

4. The transmission active lubrication control method based on oil film thickness according to claim 1, characterized in that: In step S5, the lubricating oil temperature T i The threshold value of the rate of change of the difference from the dynamic target optimization temperature T0 is 1%.

Images