CN108133110B - Method for measuring and calculating temperature field of tool rest unit in dry cutting and hobbing process - Google Patents

Method for measuring and calculating temperature field of tool rest unit in dry cutting and hobbing process Download PDF

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CN108133110B
CN108133110B CN201711464808.5A CN201711464808A CN108133110B CN 108133110 B CN108133110 B CN 108133110B CN 201711464808 A CN201711464808 A CN 201711464808A CN 108133110 B CN108133110 B CN 108133110B
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unit
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CN108133110A (en
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唐倩
刘志涛
邹政
邓峰
宋军
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Chongqing University
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Abstract

The invention discloses a method for measuring and calculating a temperature field of a tool rest group in a dry cutting and hobbing process, which comprises the following steps of: 1) calculating the heat source intensity in the hobbing process, including calculating cutting heat generated between the hob and the workpiece due to friction and metal plastic deformation, heat generated by a spindle motor and bearing heating; 2) calculating thermal boundary conditions, including determining qualitative temperature, and calculating the convective heat transfer coefficient of the surface of the hob according to the qualitative temperature; 3) and (4) according to the calculation results of the heat source intensity and the thermal boundary conditions in the hobbing process, calculating the temperature field of the tool rest group by using finite element simulation software. The invention creatively utilizes the method for calculating the heat convection coefficient when air passes through a single tube transversely to calculate the forced heat convection coefficient between the hob and the compressed air in the dry cutting and hobbing process, and can accurately calculate the temperature field of the tool rest group in the dry cutting and hobbing process. The method provides a required theoretical basis for thermal error compensation of the hobbing machine, structural optimization of the cutter rest group and the like.

Description

Method for measuring and calculating temperature field of tool rest unit in dry cutting and hobbing process
Technical Field
The invention relates to a method for measuring and calculating a temperature field, in particular to a method for measuring and calculating a temperature field of a tool rest unit in a dry cutting and hobbing process.
Background
In the process of machining of the dry-cutting numerical control gear hobbing machine, people often ignore the heating condition of the tool rest group, firstly, because the temperature field of the tool rest group is difficult to calculate, and even if the temperature field is calculated, the error is larger; and secondly, the heat productivity of the tool rest part group is mistakenly considered to be low, so that the use is not influenced, and the tool rest part group is deformed to influence the precision.
Therefore, those skilled in the art are devoted to develop a method for measuring and calculating the temperature field of the tool holder group during the dry-cutting hobbing process with high accuracy.
Disclosure of Invention
In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a method for measuring and calculating the temperature field of the tool holder assembly during the dry-cut hobbing process with high accuracy.
In order to achieve the purpose, the invention provides a method for measuring and calculating a temperature field of a tool rest group in a dry cutting and hobbing process, which comprises the following steps of:
1) calculating the heat source intensity in the hobbing process:
a1. calculating the cutting heat generated between the hob and the workpiece due to friction and metal plastic deformation:
Q1＝Fv1
Figure BDA0001530921260000011
Q1＇＝k1Q1
wherein Q1Is the cutting thermal power, and the unit is W;
f is the main cutting force, and the value here is the hobbing tangential force, and the unit is N;
v1is the cutting speed, in m/s;
d is the outer diameter of the hob in m;
n is the rotating speed of the main shaft of the hob, and the unit is r/min;
Q1' is the cutting heat input to the tool holder under actual working conditions, and has the unit of W;
k1the value is 1 to 10 percent for the cutting heat transfer proportion;
b1. calculating heat production of a spindle motor:
Figure BDA0001530921260000021
Figure BDA0001530921260000022
Q2＇＝k2Q2
wherein Q is2The unit is W for the heat production of the spindle motor;
n is the input power of the motor and the unit is W;
Mtthe unit is Nm for the output torque of the motor;
z is the motor rotating speed, and the unit is r/min;
eta is the motor efficiency;
d is the outer diameter of the hob in m;
Ftis the hobbing tangential force with the unit of N;
Q2' is the cutting heat input to the tool holder by the motor, and has the unit of W;
k2the proportion of heat production and heat transfer of the motor is 8-12%;
c1. calculating the heat generation of the bearing:
Q3＝1.047×10-4Mn
M＝M0+M1
in the formula, Q3Is the bearing heating value, and has the unit of W;
n is the rotating speed of the main shaft of the hob, and the unit is r/min;
m is the total friction moment of the bearing, and the unit is N mm;
M0torque, in N · mm, related to bearing type, rotational speed and lubricant properties;
M1the friction torque related to the load borne by the bearing is N mm;
wherein:
Figure BDA0001530921260000031
M1＝f1P1Dm
wherein D ismIs the bearing mean diameter in mm;
fois a coefficient related to the type of bearing and the manner of lubrication;
q is the bearing rotating speed, and the unit is r/min;
p is lubricantKinematic viscosity at working temperature in mm2/s；
f1Is a coefficient related to the type of bearing and the load to which it is subjected;
P1the unit is N for determining the calculation load of the friction torque of the bearing;
f1and P1The value determination method comprises the following steps:
single row radial ball bearing f1Value 0.0009 (P)0/C0)0.55，P1Value 3Fa-0.1Fr；
② biserial centripetal spherical ball bearing f1Value 0.0003 (P)0/C0)0.4，P1Value of 1.4YFa-0.1Fr；
③ Single-row angular contact ball bearing f1Value of 0.0013 (P)0/C0)0.33，P1Value Fa-0.1Fr；
Four double-row angular contact ball bearing f1Value of 0.001 (P)0/C0)0.33，P1Value of 1.4Fa-0.1Fr；
Radial short cylindrical roller bearing f with retainer1The value of P is 0.00025-0.00031Value Fr；
Double-row centripetal spherical roller bearing f1The value of P is 0.0004 to 0.00051Value of 1.2YFa；
Seventh tapered roller bearing1The value of P is 0.0004 to 0.00051Value 2YFa；
Spherical roller bearing f with [ phi ] thrust1The value of P is 0.0005 to 0.00061Value Fa(Frmax≤0.55Fa)；
Wherein, P0Is the bearing equivalent static load in N;
C0the unit is N for the rated static load of the bearing;
Fathe unit is N, and the axial force is borne by the bearing;
Fris a bearing standRadial force is applied, and the unit is N;
y is when Fa/FrAxial load factor > e;
wherein, if P1＜FrThen get P1＝Fr；
P0The value-taking method of (1) is as follows;
Figure BDA0001530921260000041
wherein X0Is the radial static load coefficient;
Y0axial static load coefficient;
2) calculating the thermal boundary conditions:
a2. determining a qualitative temperature:
Figure BDA0001530921260000042
wherein t is the qualitative temperature, twIs the solid surface temperature, t∞Is the fluid temperature;
b2. calculating the convective heat transfer coefficient of the surface of the hob according to the qualitative temperature
Figure BDA0001530921260000043
Nu＝CRe bPr 1/3
Figure BDA0001530921260000051
Wherein alpha is the convective heat transfer coefficient between the surface of the main shaft and the air and has the unit of W/(m)2℃)；
NuIs the Nussel number;
λ is air thermal conductivity, with the unit of W/(m.k);
l is a characteristic length, and is taken as the outer diameter of the hob, and the unit is m;
re is Reynolds number;
pr is the Plantt number;
rho is the air density in kg/m3；
v2Is the air flow rate, and the unit is m/s;
d1taking the outer diameter of the hob as the equivalent diameter, wherein the unit is m;
g is the aerodynamic viscosity in kg/(m.s) or Pa.s;
C. b is a constant, and the value taking method comprises the following steps: when Re is 0.4-4, C is 0.989, b is 0.330, when Re is 4-40, C is 0.911, b is 0.385, when Re is 40-4000, C is 0.683, b is 0.466, when Re is 4000-40000, C is 0.193, b is 0.618, when Re is 40000-400000, C is 0.0266, b is 0.805;
3) and (4) according to the calculation results of the heat source intensity and the thermal boundary conditions in the hobbing process, calculating the temperature field of the tool rest group by using finite element simulation software.
Preferably, when the tool rest group uses lubricating grease, p is kinematic viscosity of the lubricating grease at working temperature, and the value is base oil viscosity with unit of mm2/s。
Preferably, foThe value determination method comprises the following steps:
firstly, taking 0.7-1 of single-row radial ball bearing oil mist lubrication, 1.5-2 of horizontal shaft oil bath lubrication or grease lubrication, and 3-4 of vertical shaft oil bath lubrication or oil spray lubrication;
using 0.7-1 of oil mist lubrication of the double-row centripetal spherical ball bearing, 1.5-2 of oil bath lubrication or grease lubrication of the transverse shaft, and 3-4 of oil bath lubrication or oil spray lubrication of the vertical shaft;
thirdly, single-row angular contact ball bearing oil mist lubrication is taken as 1, horizontal shaft oil bath lubrication or grease lubrication is taken as 2, and vertical shaft oil bath lubrication or oil spray lubrication is taken as 4;
fourthly, oil mist lubrication of the double-row angular contact ball bearing is taken out 2, oil bath lubrication or grease lubrication of the transverse shaft is taken out 4, and oil bath lubrication or oil spray lubrication of the vertical shaft is taken out 8;
oil mist lubrication of the centripetal short cylindrical roller bearing with the retainer is 1-1.5, oil bath lubrication or grease lubrication of the transverse shaft is 2-3, and oil bath lubrication or oil spray lubrication of the vertical shaft is 4-6;
sixthly, taking 2-3% of oil mist lubrication of the double-row centripetal spherical roller bearing, 4-6% of oil bath lubrication or grease lubrication of a transverse shaft and 8-12% of oil bath lubrication or oil spray lubrication of a vertical shaft;
seventhly, oil mist lubrication of the tapered roller bearing is 1.5-2, oil bath lubrication or grease lubrication of a horizontal shaft is 3-4, and oil bath lubrication or oil spray lubrication of a vertical shaft is 6-8;
the oil mist lubrication of the thrust ball bearing is 0.7-1, the oil bath lubrication or grease lubrication of the transverse shaft is 1.5-2, and the oil bath lubrication or oil spray lubrication of the vertical shaft is 3-4.
Preferably, X0And Y0The value taking method comprises the following steps: in the case of a single row or parallel combination, X is the angle of contact at 15 DEG0Value of 0.5, Y0When the value is 0.46 and the contact angle is 18 degrees, X0Value of 0.5, Y0When the value is 0.42 and the contact angle is 25 degrees, X0Value of 0.5, Y0Value of 0.38, contact angle of 30 DEG, X0Value of 0.5, Y0When the value is 0.33 and the contact angle is 40 degrees, X0Value of 0.5, Y0The value is 0.26; in the case of back-to-back or face-to-face combination, X is the angle of contact of 15 °0Value of 1, Y0When the value is 0.92 and the contact angle is 18 degrees, X0Value of 1, Y0When the value is 0.84 and the contact angle is 25 degrees, X0Value of 1, Y0When the value is 0.76 and the contact angle is 30 degrees, X0Value of 1, Y0When the value is 0.66 and the contact angle is 40 degrees, X0Value of 1, Y0The value is 0.52.
The invention has the beneficial effects that: the invention creatively utilizes the method for calculating the heat convection coefficient when air passes through a single tube transversely to calculate the forced heat convection coefficient between the hob and the compressed air in the dry cutting and hobbing process, and can accurately calculate the temperature field of the tool rest group in the dry cutting and hobbing process. The method provides a required theoretical basis for thermal error compensation of the hobbing machine, structural optimization of the cutter rest group and the like.
Drawings
Fig. 1 is a schematic structural diagram of a temperature field measurement result according to an embodiment of the present invention.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
taking a tool rest group of a numerical control dry cutting gear hobbing machine as an example, the processing parameters are shown in table 1:
TABLE 1 parameter table of knife rest set of numerical control dry cutting gear hobbing machine
Figure BDA0001530921260000071
According to the parameters of table 1, the method according to the invention calculates the following:
1) calculating the heat source intensity in the hobbing process:
a1. calculating the cutting heat generated between the hob and the workpiece due to friction and metal plastic deformation:
Q1＝Fv1
Figure BDA0001530921260000072
Q1＇＝k1Q1
wherein Q1Is the cutting thermal power, and the unit is W;
f is the main cutting force, and the value here is the hobbing tangential force, and the unit is N;
v1is the cutting speed, in m/s;
d is the outer diameter of the hob in m;
n is the rotating speed of the main shaft of the hob, and the unit is r/min;
Q1' is the cutting heat input to the tool holder under actual working conditions, and has the unit of W;
k1the value is 1% -10% for the cutting heat transfer ratio, and the value is 5% in the embodiment;
Figure BDA0001530921260000081
Q1＇＝k1Q1＝5％×1498.1＝74.905W
b1. calculating heat production of a spindle motor:
Figure BDA0001530921260000082
Figure BDA0001530921260000083
Q2＇＝k2Q2
wherein Q is2The unit is W for the heat production of the spindle motor;
n is the input power of the motor and the unit is W;
Mtthe unit is Nm for the output torque of the motor;
z is the motor rotating speed, and the unit is r/min;
eta is the motor efficiency;
d is the outer diameter of the hob in m;
Ftis the hobbing tangential force with the unit of N;
Q2' is the cutting heat input to the tool holder by the motor, and has the unit of W;
k2the proportion of heat production and heat transfer of the motor is 8-12%; the value in this example is 10%;
with the combination of the process parameters in this example, the following were calculated:
Figure BDA0001530921260000091
Figure BDA0001530921260000092
Q2＇＝k2Q2＝10％×0.264KW＝26.4W
c1. calculating the heat generation of the bearing:
Q3＝1.047×10-4Mn
M＝M0+M1
in the formula, Q3Is the bearing heating value, and has the unit of W;
n is the rotating speed of the main shaft of the hob, and the unit is r/min;
m is the total friction moment of the bearing, and the unit is N mm;
M0torque, in N · mm, related to bearing type, rotational speed and lubricant properties;
M1the friction torque related to the load borne by the bearing is N mm;
wherein:
M0reflecting the hydrodynamic losses of the lubricant, can be calculated as follows:
Figure BDA0001530921260000093
M1the friction loss reflecting the elastic hysteresis and the local differential sliding of the bearing can be calculated according to the following formula:
M1＝f1P1Dm
wherein D ismIs the bearing mean diameter: (
Figure BDA0001530921260000094
dminIs an inner diameter, DmaxOuter diameter) in mm;
fois a coefficient related to the type of bearing and the manner of lubrication;
q is the bearing rotating speed, and the unit is r/min;
p is the kinematic viscosity of the lubricant at the working temperature in mm2/s；
f1Is a coefficient related to the type of bearing and the load to which it is subjected;
P1the unit is N for determining the calculation load of the friction torque of the bearing;
wherein f isoThe values of (a) are as shown in table 2:
TABLE 2 foValue-taking meter
Figure BDA0001530921260000101
Wherein f is1And P1The value determination method of (a) is as shown in table 3:
TABLE 3f1And P1Value calculating type table
Bearing type f1 P1
Single-row radial ball bearing 0.0009(P0/C0)0.55 3Fa-0.1Fr
Double-row radial spherical ball bearing 0.0003(P0/C0)0.4 1.4YFa-0.1Fr
Single-row angular contact ball bearing 0.0013(P0/C0)0.33 Fa-0.1Fr
Double-row angular contact ball bearing 0.001(P0/C0)0.33 1.4Fa-0.1Fr
Centripetal short cylindrical roller bearing with retainer 0.00025～0.0003 Fr
Double-row radial spherical roller bearing 0.0004～0.0005 1.2YFa
Tapered roller bearing 0.0004～0.0005 2YFa
Thrust spherical roller bearing 0.0005～0.0006 Fa(Frmax≤0.55Fa)
In Table 3, P0Is the bearing equivalent static load in N;
C0the unit is N for the rated static load of the bearing;
Fathe unit is N, and the axial force is borne by the bearing;
Frthe unit is N, the radial force borne by the bearing;
y is when Fa/FrAxial load factor > e;
wherein, if P1＜FrThen get P1＝Fr；
In Table 3, the bearing equivalent static load P0Is a fictitious load, i.e. the contact between the rolling elements and the raceways which is subjected to the greatest load in the event of a bearing standstill, which fictitious load isThe maximum contact stress generated by the desired load is the same as the maximum contact stress generated under the actual load condition.
For radial bearings, the equivalent static load P0It can be calculated by the following formula, and the maximum value of the calculation results is taken as the final result. P0The value-taking method of (1) is as follows;
Figure BDA0001530921260000111
wherein X0Is the radial static load coefficient;
Y0axial static load coefficient;
X0and Y0The values of (d) are shown in table 4:
TABLE 4 static load factor X0And Y0Value-taking table
Figure BDA0001530921260000112
In this embodiment, the tool rest portion selects 9 single-row angular contact ball bearings altogether, 4 of them are installed on the bracket, 4 are installed at the tool rest main shaft front end, 1 is installed at the tool rest main shaft tail end, the bearing model and the parameter of selecting are as table 5:
TABLE 5 bearing model and parameter table
Figure BDA0001530921260000121
According to the above parameters and calculation method, the calculation results of the heating power of each bearing set of the tool rest set in this embodiment are shown in table 6:
table 6 heating power of each bearing set of tool rest set in this embodiment
Bearing setPosition of Calorific value (W)
Bracket holder 24
Front end of main shaft of tool rest 52.92
End of main shaft of knife rest 7.76
2) Calculating the thermal boundary conditions:
a2. determining a qualitative temperature:
Figure BDA0001530921260000122
wherein t is the qualitative temperature, twIs the solid surface temperature, t∞Is the fluid temperature;
in this example, the measured qualitative temperature t was 33 ℃, the air flow rate v2 was 3.335m/s, and the pressure P was 0.4 MPa.
b2. The thermal boundary conditions only consider the convective heat transfer coefficient of air. The convection heat transfer on the surface of the knife rest group is divided into forced convection heat transfer and natural convection heat transfer. The heat convection between the outer surface of the knife rest and other static parts and air is natural heat convection, and according to experience, the natural heat convection coefficient is 10W/(m)2Deg.c). In the hobbing process, the main shaft of the tool rest rotates at a certain rotating speed, and compressed air skips over the surface of the hob at a constant speed, which is similar to the situation that air sweeps across a single tube, and the convection heat exchange is called forced convection heat exchange. According to the method for calculating the convective heat transfer coefficient of the air transverse single tube, the convective heat transfer coefficient of the surface of the hob can be calculated by the following formula: namely, the convective heat transfer coefficient of the surface of the hob is calculated according to the qualitative temperature
Figure BDA0001530921260000131
Nu＝CRe bPr 1/3
Figure BDA0001530921260000132
Wherein alpha is the convective heat transfer coefficient between the surface of the main shaft and the air and has the unit of W/(m)2℃)；
NuIs the Nussel number;
λ is air thermal conductivity, with the unit of W/(m.k);
l is a characteristic length, and is taken as the outer diameter of the hob, and the unit is m;
re is Reynolds number;
pr is the Plantt number;
rho is the air density in kg/m3；
v2Is the air flow rate, and the unit is m/s;
d1taking the outer diameter of the hob as the equivalent diameter, wherein the unit is m;
g is the aerodynamic viscosity in kg/(m.s) or Pa.s;
C. b is constant, and the value taking method is shown in the table 7:
TABLE 7C and b value taking tables
Re C n
0.4～4 0.989 0.330
4～40 0.911 0.385
40～4000 0.683 0.466
4000～40000 0.193 0.618
40000～400000 0.0266 0.805
The physical characteristic parameters of the air are shown in a table 8:
TABLE 8 thermal physical property parameter table of dry air under standard atmospheric pressure
Figure BDA0001530921260000141
In the above table parameters, only air density is related to pressure. The air density was about 4.558kg/m when the pressure P was 0.4MPa, as determined by a table lookup3Therefore, it is
Figure BDA0001530921260000142
Because 40000 is more than Re, C takes a value of 0.0266, b takes a value of 0.805,
Nu＝CRe bPr 1/3＝0.0266Re 0.805Pr 1/3
Figure BDA0001530921260000143
3) calculating the thermal boundary conditions: and (4) according to the calculation results of the heat source intensity and the thermal boundary conditions in the hobbing process, calculating the temperature field of the tool rest group by using finite element simulation software. The temperature of the hob 1 is 47.916 ℃ schematically, the temperature of the hob 2 is 41.192 ℃ schematically, the temperature of the bracket top 3 is 32.235 ℃ schematically, the temperature of the bracket end cover 4 is 30.003 ℃ schematically, the temperature of the back plate 5 is 26.575 ℃ schematically, the temperature of the bracket bottom 6 is 29.711 ℃ schematically, the temperature of the motor cover bottom 7 is 26.847 ℃ schematically, the temperature of the motor cover 8 is 29.767 ℃ schematically, the temperature of the motor cover 9 is 26.371 ℃ schematically, and the temperature of the motor cover 10 is 26.646 ℃ schematically.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims (3)

1. A method for measuring and calculating a temperature field of a tool rest group in a dry cutting and hobbing process is characterized by comprising the following steps of: the method comprises the following steps:
1) calculating the heat source intensity in the hobbing process:
a1. calculating the cutting heat generated between the hob and the workpiece due to friction and metal plastic deformation:
Q1＝Fv1
Figure FDA0003023658780000011
Q1＇＝k1Q1
wherein Q1Is the cutting thermal power, and the unit is W;
f is the main cutting force, and the value here is the hobbing tangential force, and the unit is N;
v1is the cutting speed, in m/s;
d is the outer diameter of the hob in m;
n is the rotating speed of the main shaft of the hob, and the unit is r/min;
Q1' is the cutting heat input to the tool holder under actual working conditions, and has the unit of W;
k1the value is 1 to 10 percent for the cutting heat transfer proportion;
b1. calculating heat production of a spindle motor:
Figure FDA0003023658780000012
Figure FDA0003023658780000013
Q2＇＝k2Q2
wherein Q is2The unit is W for the heat production of the spindle motor;
n is the input power of the motor and the unit is W;
Mtthe unit is Nm for the output torque of the motor;
z is the motor rotating speed, and the unit is r/min;
eta is the motor efficiency;
d is the outer diameter of the hob in m;
Ftis the hobbing tangential force with the unit of N;
Q2' is the cutting heat input to the tool holder by the motor, and has the unit of W;
k2the proportion of heat production and heat transfer of the motor is 8-12%;
c1. calculating the heat generation of the bearing:
Q3＝1.047×10-4Mn
M＝M0+M1
in the formula, Q3Is the bearing heating value, and has the unit of W;
n is the rotating speed of the main shaft of the hob, and the unit is r/min;
m is the total friction moment of the bearing, and the unit is N mm;
M0torque, in N · mm, related to bearing type, rotational speed and lubricant properties; m1The friction torque related to the load borne by the bearing is N mm;
wherein:
Figure FDA0003023658780000021
M1＝f1P1Dm
wherein D ismIs the bearing mean diameter in mm;
fois a coefficient related to the type of bearing and the manner of lubrication;
q is the bearing rotating speed, and the unit is r/min;
p is the kinematic viscosity of the lubricant at the working temperature in mm2/s；
f1Is a coefficient related to the type of bearing and the load to which it is subjected;
P1the unit is N for determining the calculation load of the friction torque of the bearing;
f1and P1The value determination method comprises the following steps:
single row radial ball bearing f1Value 0.0009 (P)0/C0)0.55，P1Value 3Fa-0.1Fr；
② biserial centripetal spherical ball bearing f1Value 0.0003 (P)0/C0)0.4，P1Value of 1.4YFa-0.1Fr；
③ Single-row angular contact ball bearing f1Value of 0.0013 (P)0/C0)0.33，P1Value Fa-0.1Fr；
Four double-row angular contact ball bearing f1Value of 0.001 (P)0/C0)0.33，P1Value of 1.4Fa-0.1Fr；
Radial short cylindrical roller bearing f with retainer1The value of P is 0.00025-0.00031Value Fr；
Double-row centripetal spherical roller bearing f1The value of P is 0.0004 to 0.00051Value of 1.2YFa；
Seventh tapered roller bearing1The value of P is 0.0004 to 0.00051Value 2YFa；
Spherical roller bearing f with [ phi ] thrust1The value of P is 0.0005 to 0.00061Value Fa(Frmax≤0.55Fa) (ii) a Wherein, P0Is the bearing equivalent static load in N;
C0the unit is N for the rated static load of the bearing;
Fathe unit is N, and the axial force is borne by the bearing;
Frthe unit is N, the radial force borne by the bearing;
y is when Fa/FrWhen the axial load coefficient is larger than e, the e is a judgment coefficient and can be found in a bearing manual;
wherein, if P1＜FrThen get P1＝Fr；
P0The value-taking method of (1) is as follows;
Figure FDA0003023658780000031
wherein X0Is the radial static load coefficient;
Y0axial static load coefficient;
2) calculating the thermal boundary conditions:
a2. determining a qualitative temperature:
Figure FDA0003023658780000041
wherein t isQualitative temperature, twIs the solid surface temperature, t∞Is the fluid temperature;
b2. calculating the convective heat transfer coefficient of the surface of the hob according to the qualitative temperature
Figure FDA0003023658780000042
Nu＝CRe bPr 1/3
Figure FDA0003023658780000043
Wherein alpha is the convective heat transfer coefficient between the surface of the main shaft and the air and has the unit of W/(m)2℃)；
NuIs the Nussel number;
λ is air thermal conductivity, with the unit of W/(m.k);
l is a characteristic length, and is taken as the outer diameter of the hob, and the unit is m;
re is Reynolds number;
pr is the Plantt number;
rho is the air density in kg/m3；
v2Is the air flow rate, and the unit is m/s;
d1taking the outer diameter of the hob as the equivalent diameter, wherein the unit is m;
g is the aerodynamic viscosity in kg/(m.s) or Pa.s;
C. b is a constant, and the value taking method comprises the following steps: when Re is 0.4-4, C is 0.989, b is 0.330, when Re is 4-40, C is 0.911, b is 0.385, when Re is 40-4000, C is 0.683, b is 0.466, when Re is 4000-40000, C is 0.193, b is 0.618, when Re is 40000-400000, C is 0.0266, b is 0.805;
3) according to the calculation results of the heat source intensity and the thermal boundary conditions in the hobbing process, the temperature field of the tool rest group can be calculated by utilizing finite element simulation software;
fothe value determination method comprises the following steps:
firstly, taking 0.7-1 of single-row radial ball bearing oil mist lubrication, 1.5-2 of horizontal shaft oil bath lubrication or grease lubrication, and 3-4 of vertical shaft oil bath lubrication or oil spray lubrication;
using 0.7-1 of oil mist lubrication of the double-row centripetal spherical ball bearing, 1.5-2 of oil bath lubrication or grease lubrication of the transverse shaft, and 3-4 of oil bath lubrication or oil spray lubrication of the vertical shaft;
thirdly, single-row angular contact ball bearing oil mist lubrication is taken as 1, horizontal shaft oil bath lubrication or grease lubrication is taken as 2, and vertical shaft oil bath lubrication or oil spray lubrication is taken as 4;
fourthly, oil mist lubrication of the double-row angular contact ball bearing is taken out 2, oil bath lubrication or grease lubrication of the transverse shaft is taken out 4, and oil bath lubrication or oil spray lubrication of the vertical shaft is taken out 8;
oil mist lubrication of the centripetal short cylindrical roller bearing with the retainer is 1-1.5, oil bath lubrication or grease lubrication of the transverse shaft is 2-3, and oil bath lubrication or oil spray lubrication of the vertical shaft is 4-6;
sixthly, taking 2-3% of oil mist lubrication of the double-row centripetal spherical roller bearing, 4-6% of oil bath lubrication or grease lubrication of a transverse shaft and 8-12% of oil bath lubrication or oil spray lubrication of a vertical shaft;
seventhly, oil mist lubrication of the tapered roller bearing is 1.5-2, oil bath lubrication or grease lubrication of a horizontal shaft is 3-4, and oil bath lubrication or oil spray lubrication of a vertical shaft is 6-8;
the oil mist lubrication of the thrust ball bearing is 0.7-1, the oil bath lubrication or grease lubrication of the transverse shaft is 1.5-2, and the oil bath lubrication or oil spray lubrication of the vertical shaft is 3-4.
2. The method for measuring and calculating the temperature field of the tool rest group in the dry-cutting hobbing process according to claim 1, characterized in that: when the tool rest group uses lubricating grease, p is the kinematic viscosity of the lubricating grease at the working temperature, the value is the viscosity of base oil, and the unit is mm2/s。
3. The method for measuring and calculating the temperature field of the tool rest group in the dry-cutting hobbing process according to claim 1, characterized in that: x0And Y0The value taking method comprises the following steps: in the case of a single row or parallel combination, X is the angle of contact at 15 DEG0Value of 0.5, Y0When the value is 0.46 and the contact angle is 18 degrees, X0Value of 0.5, Y0When the value is 0.42 and the contact angle is 25 degrees, X0Value of 0.5, Y0Value of 0.38, contact angle of 30 DEG, X0Value of 0.5, Y0When the value is 0.33 and the contact angle is 40 degrees, X0Value of 0.5, Y0The value is 0.26; in the case of back-to-back or face-to-face combination, X is the angle of contact of 15 °0Value of 1, Y0When the value is 0.92 and the contact angle is 18 degrees, X0Value of 1, Y0When the value is 0.84 and the contact angle is 25 degrees, X0Value of 1, Y0When the value is 0.76 and the contact angle is 30 degrees, X0Value of 1, Y0When the value is 0.66 and the contact angle is 40 degrees, X0Value of 1, Y0The value is 0.52.
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