CN102528560B - 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

A kind of method for measuring static pre-tightening force of main shaft bearing of machine tool

Technical field

The performance test application that the invention belongs to machine tool mainshaft bearing, relates to a kind of method for measuring static pre-tightening force of main shaft bearing of machine tool.

Background technology

Machine tool chief axis rolling bearing is carried out to pretension, can eliminate on the one hand rolling bearing at the play of manufacturing in assembling process, increase the rigidity of bearing, the running accuracy of raising main shaft, simultaneously, due to the effect of pretightning force, can reduce the skidding of bearing ball revolution, eliminate gyroscopic effect, and then improve the heating situation of bearing, extend the service life of bearing.

The firmly beforehand means that machine tool chief axis is conventional is level pressure pretension, its feature is that pretightning force is constant, the requirement to pretightning force and comprehensively determining according to low-speed heavy cut and high speed light cut of its size, but level pressure firmly beforehand means exists significantly not enough: when low speed, pretightning force is less than normal, bearing rigidity is declined, a little less than the ability of the anti-forced vibration of main shaft and self-excited vibration, thereby cause machining accuracy to decline; When high speed, pretightning force is bigger than normal, makes bearing temperature rise aggravation, has restricted the high speed of main shaft.Therefore need to measure the pretightning force of main shaft, change bearing pre-fastening size, raising main shaft performance according to not synchronized section.

At present, in engineering except having for the not high occasion of ask for something some simple pretightning force evaluation methods, the method of determining bearing pre-fastening generally adopts empirical method (feel method), and this method efficiency is low, operation link complexity, and measurement result is inaccurate, therefore need on the basis of definite method of conventional pretightning force, study new static pretightning force measuring method.

Summary of the invention

The object of the invention is: for the more difficult measurement of current machine tool mainshaft bearing pretightning force, and the inaccurate present situation of measurement result, a kind of method for measuring static pre-tightening force of main shaft bearing of machine tool has been proposed.

For achieving the above object, the present invention is by the following technical solutions:

A kind of method for measuring static pre-tightening force of main shaft bearing of machine tool, comprises the following steps: set up 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 matching relation of quiet rigidity; Set up Machine Tool Spindle Static mechanical model, adopt influence coefficient method to calculate Spindle Static rigidity, calculate Spindle Static rigidity value by the quiet rigidity value of bearing arranging under different pretightning forces in Machine Tool Spindle Static mechanical model, thereby set up bearing pre-fastening and Spindle Static rigidity matching relational database; The quiet rigidity that records front-end of spindle by quiet stiffness measurement experiment, is input to the Spindle Static rigidity obtaining in above-mentioned bearing pre-fastening and Spindle Static rigidity matching relational database, obtains the static pretightning force of main shaft bearing by inquiry.

As the preferred embodiments of the present invention, while carrying out the experiment of Spindle Static stiffness measurement, capacitance displacement sensor is installed on sensor stand at front-end of spindle, sensor at right angle setting, and ensure to be positioned in the plane vertical with main-shaft axis;

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

As the preferred embodiments of the present invention, when main shaft is carried out to Spindle Static stiffness measurement, by hydraulic cylinder, front-end of spindle is loaded, the position of the point of application is positioned under main shaft, application of force process should slowly be carried out, and is reaching after the maximum displacement of permission, stops immediately loading, keep 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 is carried out to Spindle Static stiffness measurement, the radial load applying should be greater than 0.8 times to maximum drag of main shaft diameter.

Compared with prior art, the static pretightning force measuring method of the present invention at least has the following advantages: first the present invention applies different pretightning forces to main shaft bearing, obtain the relation of the quiet rigidity of bearing and bearing pre-fastening, then quiet this bearing rigidity is input in main shaft model, obtain the relation of the quiet rigidity of bearing and Spindle Static rigidity, like this, relation between bearing pre-fastening and Spindle Static rigidity just can obtain, finally, record by experiment the quiet rigidity of main shaft, go out again the static pretightning force of bearing according to the relational query between above-mentioned Spindle Static rigidity and bearing pre-fastening.The static pretightning force of bearing that measuring method of the present invention obtains by Spindle Static rigidity, measurement result is accurate.

Brief description of the drawings

Fig. 1 is method for measuring static pre-tightening force of main shaft bearing of machine tool flow chart of the present invention;

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

Fig. 3 is 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, is (b) two bearing arrangements;

Fig. 5 is Machine Tool Spindle Static stiffness measurement experiment structural representation;

Fig. 6 is Machine Tool Spindle Static stiffness measurement experiment sensor schematic layout pattern.

Concrete implementation step

Do concrete introduction below in conjunction with a kind of embodiment of 1 to 6 pair of a kind of method for measuring static pre-tightening force of main shaft bearing of machine tool of the present invention of accompanying drawing:

1. set up main shaft mechanical model, according to main shaft practical structures, can be divided into two bearings supporting-rotor-support-foundation system and three bearing supporting-rotor-support-foundation systems, as shown in Figure 2, according to force and moment 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 bearing bearing reaction according to force and moment 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: the radially support reaction of front support bearing to main shaft, unit: ox (N)

F _y2: the radially support reaction of rear support bearing to main shaft, unit: ox (N)

A: the span between radial load and rear support bearing;

B: the span between front support bearing and rear support 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, also needs to supplement a relational expression except the equilibrium equation of force and moment.Adopt deformational overprint method to calculate.Suppose

for superfluous constraint, in the time that bearing rigidity is larger, can suppose radial load FP and the support reaction of rear support bearing to main shaft

exist respectively

fulcrum place amount of deflection

superposition value be zero:

$\left\{\begin{array}{c}{w}_{F_p}=-\frac{F_P(a^{\′}-c)b^{\′}}{6{\mathrm{EI}}_c}(c^2-b^{\′2})\\ w_{F_{y2}}=-\frac{F_{y2}{b}^{\′}(c-b^{\′})}{6{\mathrm{EI}}_c}(c^2-{(c-b^{\′})}^2-b^{\′2})\\ w_{F_p}+w_{F_{y2}}=0\end{array}\right.$

A': the span between external load and rear support bearing;

B': the span between middle spring bearing and rear support bearing;

C: the span between front support bearing and rear support bearing;

E: the elastic modelling quantity of spindle material;

I _c: the moment of inertia of shaft part between front support bearing and rear support bearing, unit: m^4;

Adhesion and torque equilibrium equation again:

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

F _y1': the support reaction of front support bearing to main shaft;

F _y2': the support reaction of middle spring bearing to main shaft;

F _y3': the support reaction of rear support bearing to 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 Internal and external cycle raceway contact angle under connected load effect, and steel ball load, load distributes with the variation of contact angle, set up on this basis the pretightning force of bearing and the matching relation of quiet rigidity.

3. set up Machine Tool Spindle Static mechanical model, adopt influence coefficient method to calculate Spindle Static rigidity.

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

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

In 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, as shown in Figure 4 (a), the rigidity of establishing i supporting is c _i, at radial load F _plower its strain of effect is δ _i, its support reaction is F _yi, as regulation F _ptowards a direction for just, F _yitowards with its contrary direction for just, when using F _yireplace i supporting (with F _y2replacing intermediate support 2 is example, and as shown in Figure 4 (b)), three-support structure is converted into two supporting structures, bearing load F _ptime, main-axis end displacement is that front end bears radial load F _ptime, main-axis end radial displacement is:

y _s ^P'=F _P(α _ss-α _2s ²/α ₂₂ ^d)

Wherein:

${\mathrm{\α}}_{2s}=\frac{(l^{\′}+a^{\′\′\′})(l^{\′}-l_1)}{c_2{l}^{\′2}}-\frac{l_1{a}^{\′\′\′}}{c_3{l}^{\′2}}-\frac{l_1{a}^{\′\′\′}(l^{\′}-l_1)(2l^{\′}-l_1)}{6{\mathrm{EIl}}^{\′}}$

${\mathrm{\&alpha;}}_{22}=\frac{1}{c_1}{\left(\frac{l^{\&prime;}-l_1}{l^{\&prime;}}\right)}^2+\frac{1}{c_2}+\frac{1}{c_2}{\left(\frac{l_1}{l^{\&prime;}}\right)}^2+\frac{{{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HDA0000123821320000021.png,HDA0000123821320000031.png"\; state="\{\{state\}\}">l</figure-callout>}}_1}^2{(l^{\&prime;}-l_1)}^2}{3{\mathrm{EIl}}^{\&prime;}}$

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

In formula:

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

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

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

4. calculate Spindle Static rigidity value by the bearing rigidity value arranging under different pretightning forces in main shaft computation model, thereby set up bearing pre-fastening and Spindle Static rigidity matching relational database.

5. adopt quiet stiffness measurement experiment to carry out the experiment of Spindle Static stiffness measurement to main shaft, obtain the quiet rigidity of main shaft, the Spindle Static rigidity obtaining is input in the data base querying software of computer, obtain the pretightning force of main shaft bearing by inquiry.Refer to shown in Fig. 5: under main shaft 1 front end, hydraulic cylinder 2 is installed, capacitance displacement sensor 3 is installed on sensor stand, for measuring front-end of spindle displacement signal, sensor at right angle setting, and ensure to be positioned in the plane vertical with main-shaft axis.Displacement transducer 3 is measured main shaft displacement (as shown in Figure 6) in 90 ° mutually, to eliminate main shaft deviation from circular from.By hydraulic cylinder 2, main shaft 1 front end is loaded, the position of the point of application is positioned under main shaft, and application of force process should slowly be carried out, reaching after the maximum displacement of permission, stop immediately loading, keep this state 1～2 minute, slowly unloading again after instrument readings to be tested is stable.The radial load applying should be greater than 0.8 times to maximum drag of main shaft diameter.Capacitance displacement sensor 3 records front-end of spindle radial displacement, gathers displacement data by signals collecting instrument 4, is input to signal processing instrument 5 and processes, and obtains displacement data and defines and obtain quiet rigidity according to Spindle Static rigidity at computer 6.

Machine bearing pretightning force measuring method based on quiet rigidity of the present invention, adopts following critical piece:

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

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

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

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

The foregoing is only one embodiment of the present invention, it not whole or unique embodiment, the conversion of any equivalence that those of ordinary skill in the art take technical solution of the present invention by reading description of the present invention, is claim of the present invention and contains.

Claims (5)

1. a method for measuring static pre-tightening force of main shaft bearing of machine tool, comprises the following steps:

1) set up 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 matching relation of quiet rigidity;

3) set up Machine Tool Spindle Static mechanical model, adopt influence coefficient method to calculate Spindle Static rigidity, calculate Spindle Static rigidity value by the quiet rigidity value of bearing arranging under different pretightning forces in Machine Tool Spindle Static mechanical model, thereby set up bearing pre-fastening and Spindle Static rigidity matching relational database;

4) test by quiet stiffness measurement the quiet rigidity that records front-end of spindle, the Spindle Static rigidity obtaining is input in above-mentioned bearing pre-fastening and Spindle Static rigidity matching relational database, obtain the static pretightning force of main shaft bearing by inquiry.

2. a kind of method for measuring static pre-tightening force of main shaft bearing of machine tool according to claim 1, it is characterized in that: while carrying out the experiment of Spindle Static stiffness measurement, capacitance displacement sensor is installed on sensor stand at front-end of spindle, sensor at right angle setting, and ensure to be positioned in the plane vertical with main-shaft axis.

3. a kind of method for measuring static pre-tightening force of main shaft bearing of machine tool according to claim 2, is characterized in that: the main shaft displacement in 90 ° mutually of described displacement sensor, and to eliminate main shaft deviation from circular from.

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

5. a kind of method for measuring static pre-tightening force of main shaft bearing of machine tool according to claim 1, is characterized in that: when main shaft is carried out to Spindle Static stiffness measurement, the radial load applying should be greater than 0.8 times to maximum drag of main shaft diameter.

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