CN102528560A - Method for measuring static pre-tightening force of main shaft bearing of machine tool - Google Patents

Abstract

The invention discloses a method for measuring the static pre-tightening force of a main shaft bearing of a machine tool. The method comprises the steps of firstly, conducting loading analysis on a support bearing of a main shaft unit to obtain the radial load borne by a main shaft bearing; then, establishing a statics model of the main shaft bearing of the machine tool, and establishing the fitting relationship between the bearing pre-tightening force and the bearing static rigidity; subsequently, establishing a statics model of a main shaft of the machine tool, adopting an influence coefficient method to calculate the static rigidity of the front end of the main shaft, and establishing the relationship between the static rigidity of the main shaft bearing and the static rigidity of the main shaft; then, integrating the statics model of the main shaft and the statics model of the bearing, and calculating the static rigidity value of the front end of the main shaft under different pre-tightening forces of the bearing, thus establishing a fitting relationship database between the pre-tightening force of the bearing and the static rigidity of the main shaft; and finally, by the static rigidity of the front end of the main shaft, measured by static rigidity measuring experiments, inquiring the obtained static rigidity of the main shaft in the fitting relationship database of the pre-tightening force of the bearing and the static rigidity of the main shaft so as to obtain the static pre-tightening force of the main shaft bearing of the machine tool.

Description

The static pretightning force measuring method of a kind of machine tool mainshaft bearing

Technical field

The invention belongs to the performance test application of machine tool mainshaft bearing, relate to the static pretightning force measuring method of a kind of machine tool mainshaft bearing.

Background technology

The machine tool chief axis rolling bearing is carried out pretension, can eliminate the play of rolling bearing in making assembling process on the one hand, increase the rigidity of bearing, the running accuracy of raising main shaft; Simultaneously; Because the effect of pretightning force can reduce the skidding of bearing ball revolution, eliminates gyroscopic effect; And then improve the heating situation of bearing, prolong the service life of bearing.

The firmly beforehand means that machine tool chief axis is commonly used is the level pressure pretension; Its feature is that pretightning force is constant; Its size comprehensively confirms the requirement of pretightning force according to low-speed heavy cut and high speed light cut, but that the level pressure firmly beforehand means exists is significantly not enough: pretightning force is less than normal during low speed, and bearing rigidity is descended; A little less than the ability of anti-forced vibration of main shaft and self-excited vibration, thereby cause machining accuracy to descend; Pretightning force is bigger than normal during high speed, makes the bearing temperature rise aggravation, has restricted the high speed of main shaft.Therefore need to measure the pretightning force of main shaft, change the bearing pre-fastening size, improve the main shaft performance according to different speed sections.

At present; In the engineering except having for the not high occasion of ask for something some simple pretightning force evaluation methods; The method of confirming bearing pre-fastening generally adopts empirical method (feel method), and this method efficient is low, and operation link is complicated; And measurement result is inaccurate, therefore need be on the basis of definite method of conventional pretightning force the new static pretightning force measuring method of research.

Summary of the invention

The objective of the invention is: measure to present machine tool mainshaft bearing pretightning force is difficult, and the inaccurate present situation of measurement result, the static pretightning force measuring method of a kind of machine tool mainshaft bearing has been proposed.

For realizing above-mentioned purpose, the present invention adopts following technical scheme:

The static pretightning force measuring method of a kind of machine tool mainshaft bearing may further comprise the steps: set up the main shaft mechanical model, calculate each bearing radial force; Set up machine tool mainshaft bearing statics model, set up the pretightning force of bearing and the match relation of quiet rigidity; Set up machine tool chief axis statics model; Adopt influence coefficient method to calculate the quiet rigidity of main shaft; Bearing rigidity value through in the main shaft computation model, being provided with under the different pretightning forces is calculated the quiet rigidity value of main shaft, thereby sets up bearing pre-fastening and the quiet rigidity match of main shaft relational database; Test the quiet rigidity that records front-end of spindle through quiet stiffness measurement, be input to the quiet rigidity of the main shaft that obtains in above-mentioned bearing pre-fastening and the quiet rigidity match of the main shaft relational database, obtain the static pretightning force of main shaft bearing through inquiry.

As the preferred embodiments of the present invention, when carrying out the experiment of the quiet stiffness measurement of main shaft, capacitance displacement sensor is installed on sensor stand at front-end of spindle, transducer vertical is installed, and guarantees to be positioned on the plane vertical with main-shaft axis;

As the preferred embodiments of the present invention, said displacement sensor is mutually 90 ° main shaft displacement, to eliminate the main shaft deviation from circular from;

As the preferred embodiments of the present invention, when main shaft is carried out the quiet stiffness measurement of main shaft, front-end of spindle is loaded through hydraulic cylinder; The position of the point of application is positioned under the main shaft; Application of force process should slowly be carried out, and after reaching the maximum displacement of permission, stops immediately loading; Kept this state 1～2 minute, slowly unloading again after instrument readings to be tested is stable;

As the preferred embodiments of the present invention, when main shaft was carried out the quiet stiffness measurement of main shaft, the radial load that applies should be greater than main shaft diameter 0.8 times to maximum drag.

Compared with prior art; The static pretightning force measuring method of the present invention has the following advantages at least: the present invention at first applies different pretightning forces to main shaft bearing, obtains the relation of quiet rigidity of bearing and bearing pre-fastening, then the quiet rigidity of this bearing is input in the main shaft model; Obtain the relation of quiet rigidity of bearing and the quiet rigidity of main shaft; Like this, the relation between the quiet rigidity of bearing pre-fastening and main shaft just can obtain, and is last; Record the quiet rigidity of main shaft through experiment, the static pretightning force that goes out bearing according to the relational query between quiet rigidity of above-mentioned main shaft and the bearing pre-fastening again gets final product.The static pretightning force of bearing that measuring method of the present invention obtains through the quiet rigidity of main shaft, measurement result is accurate.

Description of drawings

Fig. 1 is the static pretightning force measuring method of a machine tool mainshaft bearing of the present invention flow chart;

Fig. 2 is a main shaft mechanics illustraton of model, and wherein, Fig. 2 (a) is a two bearings support rotor system, and Fig. 2 (b) is three bearings rotor-support-foundation systems;

Fig. 3 is a two bearings supports main shaft axle head deformation pattern;

Fig. 4 is three bearings main-axis end deformation patterns, wherein, (a) is three bearing arrangements, (b) is two bearing arrangements;

Fig. 5 is the quiet stiffness measurement experiment of a machine tool chief axis structural representation;

Fig. 6 is the quiet stiffness measurement experiment sensor of a machine tool chief axis schematic layout pattern.

The practical implementation step

A kind of embodiment below in conjunction with the static pretightning force measuring method of a kind of machine tool mainshaft bearing of 1 to 6 couple of the present invention of accompanying drawing is done concrete the introduction:

1. set up the main shaft mechanical model,, can be divided into two bearings supporting-rotor-support-foundation system and three bearing supporting-rotor-support-foundation systems according to the main shaft practical structures, as shown in Figure 2, according to power and torque equilibrium equation, adopt numerical computation method to calculate each bearing radial force.For the two bearings supporting-rotor-support-foundation system shown in Fig. 2 (a), can obtain the bearing bearing reaction according to power and torque equilibrium equation:

$\left\{\begin{array}{c}{F}_P-F_{y1}-F_{y2}=0\\ F_P(a-b)-F_{y2}b=0\end{array}\right.$

F _P: the radial load size of main shaft, unit: ox (N);

F _Y1: preceding spring bearing is to the radially support reaction of main shaft, unit: ox (N)

F _Y2: the back spring bearing is to the radially support reaction of main shaft, unit: ox (N)

A: the span between radial load and the back spring bearing;

B: the span between preceding spring bearing and the back spring bearing;

For three bearing supporting-rotor-support-foundation systems shown in Fig. 2 (b), owing to there are three bearing positions, stressed problem belongs to indeterminate, except the equilibrium equation of power and moment, also need replenish a relational expression.Adopt the distortion addition method to calculate.Suppose Fy ₂Be superfluous constraint, when bearing rigidity is big, can suppose radial load FP and the support reaction Fy of back spring bearing main shaft ₂Respectively at Fy ₂Fulcrum place amount of deflection

Superposition be zero:

$\left\{\begin{array}{c}{w}_{\mathrm{Fp}}=-\frac{F_P(a^{\&prime;}-c)b^{\&prime;}}{6{\mathrm{EI}}_c}(c^2-b^{\&prime;2})\\ w_{{\mathrm{<figure-callout\; id="2"\; label="Fy"\; filenames="HDA0000123821320000022.png,HDA0000123821320000031.png"\; state="\{\{state\}\}">Fy</figure-callout>}}_2}=-\frac{F_{y2}{b}^{\&prime;}(c-b^{\&prime;})}{6{\mathrm{EI}}_c}(c^2-{(c-b^{\&prime;})}^2-b^{\&prime;2})\\ w_{\mathrm{Fp}}+{\mathrm{<figure-callout\; id="2"\; label="w\; Fy"\; filenames="HDA0000123821320000022.png,HDA0000123821320000031.png"\; state="\{\{state\}\}">w</figure-callout>}}_{{\mathrm{Fy}}_{}}=0\end{array}\right.$

A ': the span between external load and the back spring bearing;

B ': the span between middle spring bearing and the back spring bearing;

C: the span between preceding spring bearing and the back spring bearing;

E: the elastic modelling quantity of spindle material;

I _c: the moment of inertia of shaft part between preceding spring bearing and the back spring bearing, unit: m^4;

Adhesion and torque equilibrium equation again:

$\left\{\begin{array}{c}{F}_P-{F_{y1}}^{\&prime;}-{F_{y2}}^{\&prime;}-{F_{y3}}^{\&prime;}=0\\ {F_{y1}}^{\&prime;}c+{F_{y2}}^{\&prime;}{b}^{\&prime;}-F_P{a}^{\&prime;}=0\end{array}\right.$

F _Y1': preceding spring bearing is to the support reaction of main shaft;

F _Y2': middle spring bearing is to the support reaction of main shaft;

F _Y3': the back spring bearing is to the support reaction of main shaft;

Just can obtain each bearing bearing reaction.

2. set up machine tool mainshaft bearing statics model; This model has been considered the variation of the inside and outside down figure raceway of connected load effect contact angle; And steel ball load, load distributes with the variation of contact angle, and the pretightning force of setting up bearing on this basis concerns with the match of quiet rigidity.

3. set up machine tool chief axis statics model, adopt influence coefficient method to calculate the quiet rigidity of main shaft.

For two bearings supporting-rotor-support-foundation system, as shown in Figure 3, front end bears radial load F _PThe time, the main-axis end radial displacement is:

$y_s^P=F_P[\frac{a^{\&prime;\&prime;3}}{3{\mathrm{EI}}_a}+\frac{{\mathrm{la}}^{\&prime;\&prime;3}}{3{\mathrm{EI}}_l}+\frac{1}{c_1}{(1+\frac{a^{\&prime;\&prime;}}{l})}^2+\frac{1}{c_2}{\left(\frac{a^{\&prime;}}{l}\right)}^2]$

In the formula:

---main-axis end radial displacement;

A ", l---main shaft overhang length and bearing stride/m;

I _a, I _l---the moment of inertia/m^4 of part between the part that overhangs, supporting;

c ₁, c ₂---the radial rigidity/Nm-1 of forward and backward supporting;

For three bearing supporting-rotor-support-foundation systems, shown in Fig. 4 (a), the rigidity of establishing i supporting is c _i, at radial load F _PEffect its strain down is δ _i, its support reaction is F _Yi, like regulation F _PTowards a certain direction for just, F _YiTowards with its opposite direction for just, when using F _YiReplace i supporting (with F _Y2Replacing intermediate support 2 is example, shown in Fig. 4 (b)), then three-support structure is converted into two supporting structures, then bearing load F _PThe time, the main-axis end displacement is that front end bears radial load F _PThe time, the main-axis end radial displacement is:

y _s ^P?′＝F _P(α _ss-α _2s ²/α ₂₂ ^d)

Wherein:

${\mathrm{\&alpha;}}_{2s}=\frac{(l^{\&prime;}+a^{\&prime;\&prime;\&prime;})(l^{\&prime;}-l_1)}{c_2{l}^{\&prime;2}}-\frac{l_1{a}^{\&prime;\&prime;\&prime;}}{c_3{l}^{\&prime;2}}-\frac{l_1{a}^{\&prime;\&prime;\&prime;}(l^{\&prime;}-l_1)(2l^{\&prime;}-l_1)}{6\mathrm{EI}{l}^{\&prime;}}$

${\mathrm{\&alpha;}}_{22}=\frac{1}{c_1}{\left(\frac{l^{\&prime;}-l_1}{l^{\&prime;}}\right)}^2+\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA0000123821320000022.png,HDA0000123821320000031.png"\; state="\{\{state\}\}">c</figure-callout>}}_2}+\frac{1}{c_3}{\left(\frac{l_1}{l^{\&prime;}}\right)}^2+\frac{{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HDA0000123821320000013.png,HDA0000123821320000022.png"\; state="\{\{state\}\}">l</figure-callout>}}_1}^2{(l^{\&prime;}-l_1)}^2}{3\mathrm{EI}{l}^{\&prime;}}$

${\mathrm{\&alpha;}}_{\mathrm{ss}}=\frac{a^{\&prime;3}}{3{\mathrm{EI}}_a}+\frac{l^{\&prime;}{a}^{\&prime;2}}{3\mathrm{EI}}+\frac{1}{c_1}{(1+\frac{a^{\&prime;}}{l^{\&prime;}})}^2+\frac{1}{c_3}{\left(\frac{a^{\&prime;}}{l^{\&prime;}}\right)}^2$

In the formula:

A ' ", l ', l ₁---the main shaft length that overhangs, the 1st, 3 bearing bearing stride, the 1st, 2 bearing bearing stride/m;

I _a, I---overhang the part, the supporting between the part the moment of inertia/m^4;

c ₁, c ₂, c ₃---the radial rigidity/Nm-1 of block bearing;

4. calculate the quiet rigidity value of main shaft through the bearing rigidity value that in the main shaft computation model, is provided with under the different pretightning forces, thereby set up bearing pre-fastening and the quiet rigidity match of main shaft relational database.

5. adopt quiet stiffness measurement experiment that main shaft is carried out the quiet stiffness measurement experiment of main shaft, obtain the quiet rigidity of main shaft, be input to the quiet rigidity of the main shaft that obtains in the data base querying software of computer, obtain the pretightning force of main shaft bearing through inquiry.See also shown in Figure 5: hydraulic cylinder 2 is installed under main shaft 1 front end, capacitance displacement sensor 3 is installed on sensor stand, be used to measure the front-end of spindle displacement signal, transducer vertical is installed, and guarantees to be positioned on the plane vertical with main-shaft axis.Displacement transducer 3 is measured the main shaft displacement (as shown in Figure 6) that is mutually 90 °, to eliminate the main shaft deviation from circular from.Load through 2 pairs of main shaft 1 front ends of hydraulic cylinder, the position of the point of application is positioned under the main shaft, and application of force process should slowly be carried out; After reaching the maximum displacement of permission; Stop immediately loading, kept this state 1～2 minute, slowly unloading again after instrument readings to be tested is stable.The radial load that applies should be greater than main shaft diameter 0.8 times to maximum drag.Capacitance displacement sensor 3 records the front-end of spindle radial displacement, gathers displacement datas through signals collecting instrument 4, be input to signal processing instrument 5 and handle, computer 6 obtain displacement data and according to main shaft quiet rigidity definition obtain quiet rigidity.

Lathe bearing pre-fastening measuring method based on quiet rigidity of the present invention, adopt following critical piece:

1) hydraulic cylinder: RD-41 type high-precision hydraulic cylinder

2) capacitance displacement sensor: AS-500 U.S. MTI company

3) data collecting instrument: PAK MKII hardware system Germany MUELLER BBM company

4) digital treating meter: PAK measuring system Germany MUELLER BBM company

The above is merely one embodiment of the present invention; It or not whole or unique embodiment; The conversion of any equivalence that those of ordinary skills take technical scheme of the present invention through reading specification of the present invention is claim of the present invention and contains.

Claims (5)

1. the static pretightning force measuring method of a machine tool mainshaft bearing may further comprise the steps:

1) sets up the main shaft mechanical model, calculate each bearing radial force;

2) set up machine tool mainshaft bearing statics model, set up the pretightning force of bearing and the match relation of quiet rigidity;

3) set up machine tool chief axis statics model; Adopt influence coefficient method to calculate the quiet rigidity of main shaft; Bearing rigidity value through in the main shaft computation model, being provided with under the different pretightning forces is calculated the quiet rigidity value of main shaft, thereby sets up bearing pre-fastening and the quiet rigidity match of main shaft relational database;

4) test the quiet rigidity that records front-end of spindle through quiet stiffness measurement, be input to the quiet rigidity of the main shaft that obtains in above-mentioned bearing pre-fastening and the quiet rigidity match of the main shaft relational database, obtain the static pretightning force of main shaft bearing through inquiry.

2. the static pretightning force measuring method of a kind of machine tool mainshaft bearing according to claim 1; It is characterized in that: when carrying out the experiment of the quiet stiffness measurement of main shaft; Capacitance displacement sensor is installed on sensor stand at front-end of spindle; Transducer vertical is installed, and guarantees to be positioned on the plane vertical with main-shaft axis.

3. the static pretightning force measuring method of a kind of machine tool mainshaft bearing according to claim 2, it is characterized in that: said displacement sensor is mutually 90 ° main shaft displacement, to eliminate the main shaft deviation from circular from.

4. the static pretightning force measuring method of a kind of machine tool mainshaft bearing according to claim 1 is characterized in that: when main shaft is carried out the quiet stiffness measurement of main shaft, through hydraulic cylinder front-end of spindle is loaded; The position of the point of application is positioned under the main shaft; Application of force process should slowly be carried out, and after reaching the maximum displacement of permission, stops immediately loading; Kept this state 1～2 minute, slowly unloading again after instrument readings to be tested is stable.

5. the static pretightning force measuring method of a kind of machine tool mainshaft bearing according to claim 1 is characterized in that: when main shaft was carried out the quiet stiffness measurement of main shaft, the radial load that applies should be greater than main shaft diameter 0.8 times to maximum drag.

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