CN110705138A - Speed changer thermal model modeling method - Google Patents
Speed changer thermal model modeling method Download PDFInfo
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- CN110705138A CN110705138A CN201910786462.3A CN201910786462A CN110705138A CN 110705138 A CN110705138 A CN 110705138A CN 201910786462 A CN201910786462 A CN 201910786462A CN 110705138 A CN110705138 A CN 110705138A
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Abstract
The invention relates to the technical field of automobiles, and particularly discloses a thermal model modeling method of a transmission, which comprises the steps of establishing a finite element model of the transmission, and respectively calculating heat generation power and building respective heat generation power models for each bearing in the transmission, each meshing gear with a meshing relation, each oil stirring gear immersed in lubricating oil, each air stirring gear positioned in air, an oil pump and each hydraulic valve body; and a heat generation power model of the transmission is established accordingly. System thermal performance can be evaluated at any time during product development, particularly early in development, to identify and avoid thermal failure risks of the transmission.
Description
Technical Field
The invention relates to the technical field of automobiles, in particular to a speed changer thermal model modeling method.
Background
The transmission is a transmission mechanism used for transmitting the rotating speed and the torque of a vehicle-mounted power system, is one of automobile core assemblies, and has important influence on the reliability and the thermal performance of the whole automobile due to the thermal failure risk and the thermal characteristics of each part.
At present, means for evaluating the thermal failure risk of a transmission system mainly depend on a rack and a whole vehicle thermal balance working condition test, so that problems related to the thermal failure of the transmission cannot be predicted and forward designed at the initial stage of design, the later stage test has a longer verification period, the development progress is seriously influenced, and the verification cost is increased.
Disclosure of Invention
The invention aims to: the thermal model modeling method for the transmission can evaluate the thermal performance of the system at the initial stage of product development and identify and avoid the thermal failure risk of the transmission.
The invention provides a thermal model modeling method of a transmission, which comprises the following steps:
establishing a transmission finite element model;
carrying out stress analysis on each bearing, calculating friction torque of the bearing according to the stress of the bearing, and building a heat production power model of the bearing according to the product of the friction torque calculation result of the bearing and the input rotating speed of the bearing;
for each meshing gear class with a meshing relation in the transmission, respectively calculating the meshing heat generation power of each meshing gear class so as to establish a heat generation power model of each meshing gear class;
respectively calculating the oil resistance loss heat generation power of each oil-stirring gear immersed in lubricating oil in the transmission to establish a heat generation power model of each oil-stirring gear;
respectively calculating the windage loss heat generation power of each wind-stirring gear in the air in the transmission to establish a windage loss heat generation power model of each wind-stirring gear;
for the oil pump, calculating the heat production power of the oil pump according to the volumetric efficiency of the oil pump, the mechanical efficiency of the oil pump, the output pressure parameter of the oil pump and the output flow parameter of the oil pump so as to establish a heat production power model of the oil pump;
for each hydraulic valve body, calculating the heat generation power of the hydraulic valve body according to the pressure loss generated when the lubricating oil flows through the hydraulic valve body and the flow rate of the lubricating oil flowing through the hydraulic element so as to establish a heat generation power model of the hydraulic valve body;
and establishing a heat generation power model of the transmission according to the heat generation power model of each bearing, the heat generation power model of each meshing gear, the heat generation power model of the oil resistance loss of each oil stirring gear, the heat generation power model of the wind resistance loss of each oil stirring gear, the heat generation power model of the oil pump and the heat generation power model of each hydraulic valve body through AMEstim software.
Preferably, the transmission is divided into mass blocks through AMEsim software according to a heat generation power model of the transmission;
performing three-dimensional flow field simulation on the speed changer, extracting the characteristic speed and the volume fraction of lubricating oil on each mass block, then calculating the convection heat transfer coefficient of each mass block, and calculating the output heat transfer power of the corresponding mass block through the convection heat transfer coefficient so as to establish a heat transfer model of the speed changer;
and integrating a heat generation power model of the transmission with a heat transfer model of the transmission through AMEstim software, and calculating the real-time temperature of the mass block to obtain a thermal model of the transmission.
Preferably, the calculation formula of the heat generation power of the deep groove ball bearing is as follows:
P1＝T1×ω1；
T1＝Toil1+Tr1；
when v is1·ω1When the content of the organic acid is more than or equal to 2000,
when v is1·ω1When the frequency is less than 2000, the frequency of the electromagnetic wave is reduced,
wherein, P1For heat-generating power of deep-groove ball bearings, T1Total moment, T, of deep-groove ball bearingsoil1Viscous friction torque, T, for deep groove ball bearingsr1Is the friction torque of a deep groove ball bearing, z1Is a constant number, z1A value within the range of 0.0004 to 0.0006, p1Equivalent dynamic load for deep groove ball bearings, Fa1、Fr1Axial and radial loads, c, of deep groove ball bearings, respectivelyaFor basic rated dynamic load, y is 0.55, dm1Diameter of the shaft for mounting the deep groove ball bearing, foil1Is constant, v1Is kinematic viscosity, omega, of deep groove ball bearings1Is the angular velocity of rotation of the deep groove ball bearing.
Preferably, the calculation formula of the heat generation power of the tapered roller bearing is as follows:
P2＝T2×ω2；
T2＝Trad+Taxi+Toil2；
Trad＝frad×p2×dm2；
Taxi＝faxi×Fa2×dm2；
when v is2·ω2When the content of the organic acid is more than or equal to 2000,
when v is2·ω2When the frequency is less than 2000, the frequency of the electromagnetic wave is reduced,
wherein, P2For heat-generating power of deep-groove ball bearings, T2Total moment, T, of deep-groove ball bearingsradRadial friction torque, T, for tapered roller bearingsaxiAxial friction torque, T, for tapered roller bearingsoil2The viscous friction torque of the tapered roller bearing; f. ofradIs the radial friction torque coefficient, faxiIs axial friction torque coefficient, p2Equivalent dynamic load for tapered roller bearings, dm2Diameter of shaft for mounting tapered roller bearing, Fa2Axial load for tapered roller bearing, foil2Is constant, v2Is kinematic viscosity, omega, of a tapered roller bearing2Is the angular velocity of rotation of the tapered roller bearing.
Preferably, the calculation formula of the heat generation power of the needle bearing with the retainer is as follows:
P3＝T3×ω3
T3＝0.12dm3×Fr2 0.4+4.5×10-7×dm3×ν3 0.3×ω3 0.6；
wherein, P3For heat-generating power of needle bearings, T3Total moment of the needle bearing, dm3Diameter of the shaft for mounting the needle bearing, Fr2Is the radial load of the needle bearing, v3Is kinematic viscosity, omega, of needle bearings3Is the angular velocity of rotation of the needle bearing.
Preferably, the calculation formula of the meshing heat generation power of the meshing gear is as follows:
wherein, P4Heat generation power of meshing gear type, PsFor sliding friction power loss of meshing type gear, PrFor meshing gear rolling frictionLoss of wiping Power, LaFor meshing gear-like line length, FnFor normal loading of meshing gearwheels, VsFor sliding speed of meshing gearwheels, VrFor rolling speed of meshing gearwheels, Fr3Rolling friction load for meshing type gears, fsFor the coefficient of friction of the meshing type gear, l is the coordinate of the meshing node of the meshing type gear along the meshing line, b0The tooth width of the gear is the meshing gear, beta is the helical angle of the meshing gear, eh is the thickness of the oil film, FnuFor the normal load on each meshing line, ρ is the lubricant density, V is the kinematic viscosity of the lubricant, VgAnd VrThe sliding speed and the rolling speed of the meshing gear are respectively.
Preferably, the calculation formula of the heat generation power of the oil resistance loss of the oil-mixing type gear is as follows:
wherein, P5Loss of heat generation power for oil resistance of oil-mixing type gear CmOil-mixing drag torque, omega, for oil-mixing teeth4For the rotational speed of the oil-mixing teeth, rho is the density of the lubricating oil, Rp1Is the pitch radius of the oil-mixing teeth, SmTo agitate the surface area of the oil teeth immersed in the lubricating oil.
Preferably, the calculation formula of the heat generation power of the windage loss of the wind stirring gear is as follows:
wherein, P6For the wind resistance loss heat production power, omega, of the mixing gear5The rotating speed of the stirring gear is shown, and rho is the density of the oil-gas mixture; rp2Is pitch radius of the wind-mixing gear CtThe wind resistance moment of the wind stirring gear.
Preferably, the heat generation power calculation formula of the oil pump is as follows:
wherein N is1For heat production power of oil pump, etavIs the volumetric efficiency of the oil pump, etamFor mechanical efficiency of oil pumps, poFor output pressure of oil pump, QoOutputting flow for the oil pump;
the heat production power calculation formula of the hydraulic valve body is as follows:
N2the pressure loss caused by the lubricating oil flowing through the hydraulic valve body is delta p, and the flow rate of the lubricating oil flowing through the hydraulic valve body is Q.
Preferably, the heat transfer power of the mass block is calculated by the formula:
Φ＝Φ1+Φ2；
Φ2＝h×A2×(Tm-Tw)；
wherein λ is the thermal conductivity of the mass block, A1Is the heat conducting area, d is the center-of-mass distance of the two mass blocks, Ta、TbFor the temperature of the two mass blocks with heat conduction, h is the convective heat transfer coefficient, A2For heat convection area, TmIs the temperature of the lubricating oil, TwIs the temperature of the mass block;
the calculation formula of the real-time temperature of the mass block is as follows:
wherein phiinFor heat-generating power of mass, phioutEqual to the heat transfer power of the mass, m being the mass of the mass, CpIs the specific heat capacity of the mass.
The invention has the beneficial effects that:
the invention provides a thermal model modeling method of a transmission, which comprises the steps of establishing a finite element model of the transmission, respectively calculating heat production power of each bearing in the transmission, each meshing gear with a meshing relation, each oil stirring gear immersed in lubricating oil, each air stirring gear positioned in air, an oil pump and each hydraulic valve body, and establishing respective heat production power models; and a heat generation power model of the transmission is established accordingly. System thermal performance can be evaluated at any time during product development, particularly early in development, to identify and avoid thermal failure risks of the transmission.
Detailed Description
The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships only for the convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Where the terms "first position" and "second position" are two different positions, and where a first feature is "over", "above" and "on" a second feature, it is intended that the first feature is directly over and obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The following examples of the present invention are described in detail and are illustrative only and should not be construed as limiting the present invention.
The present embodiment provides a thermal model modeling method for a transmission, including:
s1: establishing a finite element model of the transmission; and (3) importing or automatically building a transmission model in the finite element analysis software, and building the finite element model of the transmission according to the structural size and the material characteristics of parts such as a transmission shell, a bearing, a gear and the like.
S2: and (4) carrying out stress analysis on each bearing through a finite element model so as to obtain the axial load, the radial load and the dynamic load of each bearing. And then calculating the friction torque of the bearing according to the stress of the bearing, and building a heat generation power model of the bearing according to the product of the calculation result of the friction torque of the bearing and the input rotating speed of the bearing. The axial load, the radial load and the dynamic load of the bearing can be obtained through finite element model calculation, wherein the dynamic load is divided into an equivalent dynamic load and a basic rated dynamic load.
One or more of deep groove ball bearings, tapered roller bearings, and needle roller bearings with cages are typically provided in transmissions.
For a deep groove ball bearing, the calculation formula of the heat generation power is as follows:
P1＝T1×ω1；
T1＝Toil1+Tr1；
when v is1·ω1When the content of the organic acid is more than or equal to 2000,
when v is1·ω1When the frequency is less than 2000, the frequency of the electromagnetic wave is reduced,
wherein, P1For heat-generating power of deep-groove ball bearings, T1Total moment, T, of deep-groove ball bearingsoil1Viscous friction torque, T, for deep groove ball bearingsr1Is the friction torque of a deep groove ball bearing, z1Is a constant number, z1The value is in the range of 0.0004 to 0.0006, generally speaking, the value increases with the increase of bearing capacity. p is a radical of1Equivalent dynamic load for deep groove ball bearings, Fa1、Fr1Axial and radial loads, c, of deep groove ball bearings, respectivelyaFor basic rated dynamic load, y is 0.55, dm1Diameter of the shaft for mounting the deep groove ball bearing, foil1The constants are related to the type of bearing and the lubrication method, for example, the value of 0.7 to 2 for a grease-lubricated single-row deep groove ball bearing and the value of 1.4 to 4 for a grease-lubricated double-row deep groove ball bearing. V is1Is kinematic viscosity, omega, of deep groove ball bearings1Is the angular velocity of rotation of the deep groove ball bearing. dm1、ν1And ω1May be determined by the particular type of deep groove ball bearing.
For the tapered roller bearing, the calculation formula of the heat generation power is as follows:
P2＝T2×ω2；
T2＝Trad+Taxi+Toil2；
Trad＝frad×p2×dm2；
Taxi＝faxi×Fa2×dm2；
when v is2·ω2When the content of the organic acid is more than or equal to 2000,
when v is2·ω2When the frequency is less than 2000, the frequency of the electromagnetic wave is reduced,
wherein, P2For heat-generating power of deep-groove ball bearings, T2Total moment, T, of deep-groove ball bearingsradRadial friction torque, T, for tapered roller bearingsaxiAxial friction torque, T, for tapered roller bearingsoil2The viscous friction torque of the tapered roller bearing; f. ofradIs the radial friction torque coefficient, faxiIs the axial friction torque coefficient, fradAnd faxiDependent on the specific type of bearing and all being constant, p2Equivalent dynamic load for tapered roller bearings, dm2Diameter of shaft for mounting tapered roller bearing, Fa2Axial load for tapered roller bearing, foil2Is constant, v2Is kinematic viscosity, omega, of a tapered roller bearing2Is the angular velocity of rotation of the tapered roller bearing.
For the needle bearing with the retainer, the calculation formula of the heat generation power is as follows:
P3＝T3×ω3
T3＝0.12dm3×Fr2 0.4+4.5×10-7×dm3×ν3 0.3×ω3 0.6；
wherein, P3For heat-generating power of needle bearings, T3Total moment of the needle bearing, dm3Diameter of the shaft for mounting the needle bearing, Fr2Is the radial load of the needle bearing, v3Is kinematic viscosity, omega, of needle bearings3Is the angular velocity of rotation of the needle bearing.
S3: for each meshing gear class with meshing relation in the transmission, meshing heat generation power of each meshing gear class is calculated respectively to establish a heat generation power model of each meshing gear class.
The calculation formula of the meshing heat generation power of the meshing gear is as follows:
wherein, P4Heat generation power of meshing gear type, PsFor sliding friction power loss of meshing type gear, PrFor rolling friction power loss of meshing type gears, LaFor meshing gear-like line length, FnFor normal loading of meshing gearwheels, VsFor sliding speed of meshing gearwheels, VrFor rolling speed of meshing gearwheels, Fr3The rolling friction load of the meshing gear can be obtained by carrying out stress analysis on the three-dimensional model by using finite elements. f. ofsIs the coefficient of friction of the meshing type gear, which is related to the type of gear, l is the coordinate of the meshing node of the meshing type gear along the meshing line, b0The tooth width of the gear is the meshing gear, beta is the helical angle of the meshing gear, eh is the thickness of the oil film, FnuFor the normal load on each meshing line, ρ is the lubricant density, V is the kinematic viscosity of the lubricant, VgAnd VrThe sliding speed and the rolling speed of the meshing gear are respectively.
S4: and respectively calculating the heat generation power of the oil resistance loss of each oil-stirring gear for each oil-stirring gear immersed in the lubricating oil in the transmission so as to establish a heat generation power model of each oil-stirring gear.
The calculation formula of the oil resistance loss heat production power of the oil stirring type gear is as follows:
wherein, P5Loss of heat generation power for oil resistance of oil-mixing type gear CmOil-mixing drag torque, omega, for oil-mixing teeth4For the rotational speed of the oil-mixing teeth, rho is the density of the lubricating oil, Rp1Is the pitch radius of the oil-mixing teeth, SmTo agitate the surface area of the oil teeth immersed in the lubricating oil.
S5: and respectively calculating the wind resistance loss heat generation power of each wind stirring gear in the air in the speed changer so as to establish a wind resistance loss heat generation power model of each wind stirring gear.
The calculation formula of the windage loss heat production power of the stirring type gear is as follows:
wherein, P6For the wind resistance loss heat production power, omega, of the mixing gear5The rotating speed of the stirring gear is shown, and rho is the density of the oil-gas mixture; rp2Is pitch radius of the wind-mixing gear CtThe wind resistance moment of the wind stirring gear can be obtained by carrying out finite element simulation through a three-dimensional model.
It will be appreciated that if for one of the gears, the gear is engaged with the other gear while being partially immersed in the lubricating oil and partially in the air, the power of heat generation of the gear is the sum of the respective powers calculated in steps S3 to S5. That is, for a particular one of the gears, it satisfies at least one of S3 through S5, and its actual heat generation power is the sum of the powers of the respective cases satisfied.
S6: for the oil pump, the heat production power of the oil pump is calculated according to the volume efficiency of the oil pump, the mechanical efficiency of the oil pump, the output pressure parameter of the oil pump and the output flow parameter of the oil pump, so as to establish a heat production power model of the oil pump.
The heat production power calculation formula of the oil pump is as follows:
wherein N is1For heat production power of oil pump, etavIs the volumetric efficiency of the oil pump, etamFor mechanical efficiency of oil pumps, poFor output pressure of oil pump, QoAnd outputting the flow for the oil pump.
S7: and for each hydraulic valve body, calculating the heat generation power of the hydraulic valve body according to the pressure loss generated by the lubricating oil flowing through the hydraulic valve body and the flow rate of the lubricating oil flowing through the hydraulic element so as to establish a heat generation power model of the hydraulic valve body.
The heat production power calculation formula of the hydraulic valve body is as follows:
N2the pressure loss caused by the lubricating oil flowing through the hydraulic valve body is delta p, and the flow rate of the lubricating oil flowing through the hydraulic valve body is Q.
It should be noted that, in the present embodiment, S3 to S7 are not in sequence. That is, the respective steps of S3 to S7 may be arbitrarily sequenced with each other.
S8: and establishing a heat generation power model of the transmission according to the heat generation power model of each bearing, the heat generation power model of each meshing gear, the heat generation power model of the oil resistance loss of each oil stirring gear, the heat generation power model of the wind resistance loss of each oil stirring gear, the heat generation power model of the oil pump and the heat generation power model of each hydraulic valve body through AMEstim software.
In the embodiment, by establishing a finite element model of the transmission, heat generation power is respectively calculated for each bearing in the transmission, each meshing gear with a meshing relation, each oil stirring gear immersed in lubricating oil, each air stirring gear positioned in air, an oil pump and each hydraulic valve body, and respective heat generation power models are established; and a heat generation power model of the transmission is established accordingly. System thermal performance can be evaluated at any time during product development, particularly early in development, to identify and avoid thermal failure risks of the transmission.
S9: and establishing a heat transfer model of the transmission through AMEstim software according to a heat generation power model of the transmission.
And performing three-dimensional flow field simulation on the speed changer, extracting the characteristic speed and the volume fraction of lubricating oil on each mass block, then calculating the convection heat transfer coefficient of each mass block, and calculating the output heat transfer power of the corresponding mass block through the convection heat transfer coefficient so as to establish a heat transfer model of the speed changer.
It should be noted that the division of the mass in the transmission is based on the separate division of the structure whose temperature is to be calculated. For example, if the temperature of a gear is desired, the gear may be divided into separate masses. The calculation method of the convective heat transfer coefficient of the mass blocks corresponding to different types is different, and is specifically as follows.
1) The calculation methods for the heat convection between the tooth surface of the gear and the lubricating oil are classified into the following two methods.
A. The heat exchange coefficient of the oil stirring type gear or the gear lubricated by oil injection is calculated by adopting the following formula.
When 0 is less than or equal to psi is less than or equal to 0.68,
when 0.68 < psi < 1.5,
wherein the content of the first and second substances,
wherein k is the heat conductivity coefficient of the lubricating oil; rho is the density of the lubricating oil; c is the specific heat capacity of the lubricating oil; h is the tooth height; m is a modulus; z is a radical of2Is the number of teeth; omega6Is the gear rotation angular velocity; tau is from gear leaving sump (or jet) to engagingTime (calculated from the gear oil immersion depth and the meshing position); l is the tooth width; a is the convection heat transfer area, i.e., the area of the gear immersed in the lubricating oil, and psi is the boundary amount.
B. The heat transfer coefficient of the rotating gear without oil stirring/oil injection lubrication is calculated by the following formula.
Wherein k is the heat conductivity coefficient of the lubricating oil; d is the reference circle diameter of the gear; omega7Is the gear rotation angular velocity; v is the kinematic viscosity of the lubricating oil; eta is the dynamic viscosity of the lubricating oil; cpIs the specific heat capacity of the lubricating oil. It should be noted that the convective heat transfer coefficient of the rotating circumferential surface of the rotating shaft can also be calculated by using the above formula.
2) And calculating the convective heat transfer coefficient of the side surface of the rotating element by adopting the following formula.
A. Laminar flow (Re is less than or equal to 2 x 10)5)：
B. At transition flow (2X 10)5＜Re＜2.5×105)：
C. When the fluid is turbulent (Re is more than or equal to 2.5 multiplied by 10)5)
Wherein Re is used to characterize a dimensionless number of fluid flow conditions; k is the thermal conductivity of the lubricating oil; omega8Is the rotational angular velocity of the rotating element; v is the kinematic viscosity of the lubricating oil(ii) a Eta is the dynamic viscosity of the lubricating oil; cpIs the specific heat capacity of the lubricating oil; m is a constant and is used for defining the distribution of the temperature of the gear along the radial direction, and m is 2; r iscIs the pitch circle radius of the gear.
3) The following two cases are mainly considered for the calculation of the convective heat transfer coefficient between the bearing and the lubricating oil.
A. The convective heat transfer coefficient between the bearing inner/outer ring and the retainer and the lubricating oil is calculated by the following formula.
When Ta < 41:
when 41 < Ta < 100:
when Ta > 100:
wherein v and k are respectively the kinematic viscosity and the thermal conductivity of the lubricating oil; epsilon is a clearance between the inner/outer ring raceway and the inner/outer cylindrical surface of the retainer; eta is the dynamic viscosity of the lubricating oil; r and omega are respectively radius and angular velocity, when the inner ring of the bearing rotates and the outer ring is fixed and the convection heat exchange between the inner ring and the inner cylinder of the retainer is calculated, R takes the radius of the raceway of the inner ring, omega9Taking the relative angular velocity between the inner ring and the retainer; when calculating the convective heat transfer of the fluid between the cylindrical surface of the retainer and the outer ring, R is the bearing pitch radius omega9Taking the angular speed of the retainer; when the outer ring of the bearing rotates and the inner ring is fixed, and the convective heat transfer between the inner ring and the inner cylinder of the retainer is calculated, R is the bearing pitch circle radius omega9Taking the angular velocity of the holder; when calculating the cylindrical surface and the outer ring of the retainerWhen the fluid is subjected to heat convection, R is taken as the inner radius omega of the outer ring of the bearing9And taking the relative angular speed between the outer ring and the retainer.
B. The convective heat transfer coefficient between the rolling body of the bearing and the lubricating oil is calculated by adopting the following formula.
Wherein k is the heat conductivity coefficient of the lubricating oil; v is the kinematic viscosity of the lubricating oil; eta is the dynamic viscosity of the lubricating oil; cpIs the specific heat capacity of the lubricating oil; d is the diameter of the rolling body; v is the linear velocity of the rolling body; mu.sb、μwThe kinematic viscosity is respectively at the wall surface temperature of the rolling body and the oil temperature.
4) The convective heat transfer coefficient between the outer wall of the transmission shell and the air is calculated by adopting the following formula.
A. For a vertical plate:
B. for the horizontal plate:
wherein η is aerodynamic viscosity; k is the air thermal conductivity coefficient; cp1Is the air specific heat capacity; beta is the air thermal expansion coefficient; delta t is the temperature difference between the outer wall surface of the shell and the air; lcIs a vertical plate surfaceFeature height (taking maximum height); laThe characteristic length of the horizontal plate surface is (the side length of a square, the average value of two sides of a rectangle, the diameter of a disc is 0.9 times, and the short side of a long strip) is taken.
5) The convective heat transfer coefficient between the inner wall of the transmission and the lubricating oil is calculated by adopting the following formula.
A. When Re is less than or equal to 5X 105Time of flight
B. When 5 is multiplied by 105＜Re＜107Time of flight
In the formula, k, v, eta, CpThe heat conductivity coefficient, kinematic viscosity, dynamic viscosity and specific heat capacity of the lubricating oil are respectively; v is the characteristic speed of the fluid on the inner wall surface of the shell; l is the characteristic length, the maximum plate height is taken for the vertical plate surface, the side length is taken for the horizontal plate surface and the square, the average value of the two sides is taken for the rectangle, the diameter of the disc is 0.9 times, and the short side is taken for the long strip.
6) The convective heat transfer coefficient between the wall surface of the inner oil duct of the transmission and the lubricating oil is calculated by adopting the following formula.
A. When Re is less than or equal to 2300
When in useWhen the temperature of the water is higher than the set temperature,
wherein Pr is 0.5-17000;
when in use
When the temperature of the water is higher than the set temperature,
B. when 2300 < Re < 10000;
C. when 10000 is less than or equal to Re < 120000;
wherein the content of the first and second substances,
k is the thermal conductivity of the lubricating oil; l is the length of the tube; deIs the equivalent diameter of the oil pipe, de4f/U, where f is the cross-sectional area of the tube channel and U is the wetted perimeter of the tube channel; v is the characteristic speed along the axial direction of the oil pipe; eta is the dynamic viscosity of the lubricating oil; etaf、ηwThe dynamic viscosity at the average temperature of the lubricating oil and the average temperature of the wall surface; v is the kinematic viscosity of the lubricating oil; cpThe specific heat capacity of the lubricating oil is; the characteristic parameters of the oil in Re and Pr are taken as the characteristic parameters at the average fluid temperature.
It should be noted that in the calculation of the convective heat transfer coefficient, attention needs to be paid to the influence of the volume fraction of the lubricating oil on the surface of the mass block, the volume fraction of the lubricating oil is the proportion of the lubricating oil in the oil-gas mixture, and can be obtained through three-dimensional flow field simulation, the volume fraction of the lubricating oil influences the characteristic parameters of the oil-gas mixture, such as density, kinematic viscosity, dynamic viscosity, thermal conductivity, specific heat capacity, and the like, taking the density of the oil-gas mixture as an example, the density of the oil-gas mixture is lubricating oil volume fraction plus (1-lubricating oil volume fraction) air density.
The heat transfer power of the mass block is calculated by the formula:
Φ＝Φ1+Φ2；
Φ2＝h×A2×(Tm-Tw)；
wherein λ is the thermal conductivity of the mass block, determined by the properties of the mass block, A1Is the heat conducting area, d is the center-of-mass distance of the two mass blocks, Ta、TbFor the temperature of the two mass blocks with heat conduction, h is the convective heat transfer coefficient, A2For heat convection area, TmIs the temperature of the lubricating oil, TwIs the temperature of the mass block;
s10: and integrating a heat generation power model of the transmission with a heat transfer model of the transmission through AMEstim software, and calculating the real-time temperature of the mass block to obtain a thermal model of the transmission.
The calculation formula of the real-time temperature of the mass block is as follows:
wherein phiinFor the heat-generating power of the masses, e.g. with a bearing in the transmission as a straight mass, phiinEqual to the heat generating power of the bearing. PhioutEqual to the heat transfer power of the mass, m being the mass of the mass, CpIs the specific heat capacity of the mass.
By establishing a thermal model of the transmission, the temperature rise speed of each mass block divided in the transmission can be calculated, and the final temperature of each mass block after the test is completed can be simulated by combining the test duration and the environment temperature. The method is particularly suitable for evaluating and predicting the thermal performance of the system in the early stage of development of the transmission.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A method of modeling a thermal model of a transmission, comprising:
establishing a finite element model of the transmission;
carrying out stress analysis on each bearing, calculating friction torque of the bearing according to the stress of the bearing, and building a heat production power model of the bearing according to the product of the friction torque calculation result of the bearing and the input rotating speed of the bearing;
for each meshing gear class with a meshing relation in the transmission, respectively calculating the meshing heat generation power of each meshing gear class so as to establish a heat generation power model of each meshing gear class;
respectively calculating the oil resistance loss heat generation power of each oil-stirring gear immersed in lubricating oil in the transmission to establish a heat generation power model of each oil-stirring gear;
respectively calculating the windage loss heat generation power of each wind-stirring gear in the air in the transmission to establish a windage loss heat generation power model of each wind-stirring gear;
for the oil pump, calculating the heat production power of the oil pump according to the volumetric efficiency of the oil pump, the mechanical efficiency of the oil pump, the output pressure parameter of the oil pump and the output flow parameter of the oil pump so as to establish a heat production power model of the oil pump;
for each hydraulic valve body, calculating the heat generation power of the hydraulic valve body according to the pressure loss generated when the lubricating oil flows through the hydraulic valve body and the flow rate of the lubricating oil flowing through the hydraulic element so as to establish a heat generation power model of the hydraulic valve body;
and establishing a heat generation power model of the transmission according to the heat generation power model of each bearing, the heat generation power model of each meshing gear, the heat generation power model of the oil resistance loss of each oil stirring gear, the heat generation power model of the wind resistance loss of each oil stirring gear, the heat generation power model of the oil pump and the heat generation power model of each hydraulic valve body through AMEstim software.
2. The transmission thermal model modeling method of claim 1, wherein the transmission is mass partitioned by AMEstim software according to a transmission heat production power model;
performing three-dimensional flow field simulation on the speed changer, extracting the characteristic speed and the volume fraction of lubricating oil on each mass block, then calculating the convection heat transfer coefficient of each mass block, and calculating the output heat transfer power of the corresponding mass block through the convection heat transfer coefficient so as to establish a heat transfer model of the speed changer;
and integrating a heat generation power model of the transmission with a heat transfer model of the transmission through AMEstim software, and calculating the real-time temperature of the mass block to obtain a thermal model of the transmission.
3. The thermal model modeling method of transmission of claim 1, wherein the heat generation power calculation formula of deep groove ball bearing is:
P1＝T1×ω1；
T1＝Toil1+Tr1；
when v is1·ω1When the content of the organic acid is more than or equal to 2000,when v is1·ω1When the frequency is less than 2000, the frequency of the electromagnetic wave is reduced,
wherein, P1For heat-generating power of deep-groove ball bearings, T1Total moment, T, of deep-groove ball bearingsoil1Viscous friction torque, T, for deep groove ball bearingsr1Is the friction torque of a deep groove ball bearing, z1Is a constant number, z1A value within the range of 0.0004 to 0.0006, p1Equivalent dynamic load for deep groove ball bearings, Fa1、Fr1Axial and radial loads, c, of deep groove ball bearings, respectivelyaFor basic rated dynamic load, y is 0.55, dm1Diameter of the shaft for mounting the deep groove ball bearing, foil1Is constant, v1Is kinematic viscosity, omega, of deep groove ball bearings1Is the angular velocity of rotation of the deep groove ball bearing.
4. The thermal model modeling method for transmission of claim 1, wherein the heat generation power calculation formula for the tapered roller bearing is:
P2＝T2×ω2；
T2＝Trad+Taxi+Toil2；
Trad＝frad×p2×dm2；
Taxi＝faxi×Fa2×dm2；
when v is2·ω2When the content of the organic acid is more than or equal to 2000,
when v is2·ω2When the frequency is less than 2000, the frequency of the electromagnetic wave is reduced,
wherein, P2For heat-generating power of deep-groove ball bearings, T2Total moment, T, of deep-groove ball bearingsradRadial friction torque, T, for tapered roller bearingsaxiAxial friction torque, T, for tapered roller bearingsoil2The viscous friction torque of the tapered roller bearing; f. ofradIs radial frictionCoefficient of moment, faxiIs axial friction torque coefficient, p2Equivalent dynamic load for tapered roller bearings, dm2Diameter of shaft for mounting tapered roller bearing, Fa2Axial load for tapered roller bearing, foil2Is constant, v2Is kinematic viscosity, omega, of a tapered roller bearing2Is the angular velocity of rotation of the tapered roller bearing.
5. The thermal model modeling method for transmission of claim 1, wherein the heat generation power calculation formula for needle bearings with cages is:
P3＝T3×ω3
T3＝0.12dm3×Fr2 0.4+4.5×10-7×dm3×ν3 0.3×ω3 0.6；
wherein, P3For heat-generating power of needle bearings, T3Total moment of the needle bearing, dm3Diameter of the shaft for mounting the needle bearing, Fr2Is the radial load of the needle bearing, v3Is kinematic viscosity, omega, of needle bearings3Is the angular velocity of rotation of the needle bearing.
6. The transmission thermal model modeling method of claim 1, wherein the engaged heat generation power calculation formula for the engaged gear-like is:
wherein, P4Heat generation of meshing gearsPower, PsFor sliding friction power loss of meshing type gear, PrFor rolling friction power loss of meshing type gears, LaFor meshing gear-like line length, FnFor normal loading of meshing gearwheels, VsFor sliding speed of meshing gearwheels, VrFor rolling speed of meshing gearwheels, Fr3Rolling friction load for meshing type gears, fsFor the coefficient of friction of the meshing type gear, l is the coordinate of the meshing node of the meshing type gear along the meshing line, b0The tooth width of the gear is the meshing gear, beta is the helical angle of the meshing gear, eh is the thickness of the oil film, FnuFor the normal load on each meshing line, ρ is the lubricant density, V is the kinematic viscosity of the lubricant, VgAnd VrThe sliding speed and the rolling speed of the meshing gear are respectively.
7. The method for modeling the thermal model of the transmission of claim 1, wherein the formula for calculating the heat-generating power of the oil resistance loss of the Stirling oil-type gear is as follows:
wherein, P5Loss of heat generation power for oil resistance of oil-mixing type gear CmOil-mixing drag torque, omega, for oil-mixing teeth4For the rotational speed of the oil-mixing teeth, rho is the density of the lubricating oil, Rp1Is the pitch radius of the oil-mixing teeth, SmTo agitate the surface area of the oil teeth immersed in the lubricating oil.
8. The thermal model modeling method for the transmission of claim 1, wherein the windage loss heat generation power calculation formula for the windage-like gear is:
wherein, P6For the wind resistance loss heat production power, omega, of the mixing gear5For stirring gearsRotating speed, wherein rho is the density of the oil-gas mixture; rp2Is pitch radius of the wind-mixing gear CtThe wind resistance moment of the wind stirring gear.
9. The thermal model modeling method for the transmission of claim 1, wherein the heat generation power calculation formula for the oil pump is:
wherein N is1For heat production power of oil pump, etavIs the volumetric efficiency of the oil pump, etamFor mechanical efficiency of oil pumps, poFor output pressure of oil pump, QoOutputting flow for the oil pump;
the heat production power calculation formula of the hydraulic valve body is as follows:
N2the pressure loss caused by the lubricating oil flowing through the hydraulic valve body is delta p, and the flow rate of the lubricating oil flowing through the hydraulic valve body is Q.
10. The thermal model modeling method for transmission of claim 2, wherein the mass heat transfer power calculation formula is:
Φ＝Φ1+Φ2；
Φ2＝h×A2×(Tm-Tw)；
wherein λ is the thermal conductivity of the mass block, A1Is the heat conducting area, d is the center-of-mass distance of the two mass blocks, Ta、TbFor the temperature of the two mass blocks with heat conduction, h is the convective heat transfer coefficient, A2For heat transfer area by convection，TmIs the temperature of the lubricating oil, TwIs the temperature of the mass block;
the calculation formula of the real-time temperature of the mass block is as follows:
wherein phiinFor heat-generating power of mass, phioutEqual to the heat transfer power of the mass, m being the mass of the mass, CpIs the specific heat capacity of the mass.
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