JP2002364661A - Measuring method of bearing preload and spindle unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle unit capable of accurately measuring the preload of a bearing and adjusting rotational precision based on the measured preload. SOLUTION: A variation sensor 12 is attached to an inner-ring spacer 7b which is disposed between respective inner rings 5a, 5b of two rolling bearings 2a, 2b and rotates with the inner rings 5a, 5b. A vibration signal detected by the vibration sensor 12 is transmitted from a transmission antenna 29 via an electric wave R. The sent signal is received by a receiving antenna 14 provided on an outer-ring spacer 8b between outer rings 6a, 6b on the static side. The preload of the bearings 2a, 2b is determined based on the received vibration signal by a calculating circuit 19. A preload variable mechanism 21 is controlled by a hydraulic system 26 based on the determined preload for the optimization of the preload of the bearings 2a, 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle unit used for a machine tool, an industrial machine, etc.
The present invention relates to a method for measuring a preload of a bearing of a spindle unit, a spindle unit for obtaining a preload by using the method for measuring a preload, and adjusting the preload from the obtained preload.

[0002]

2. Description of the Related Art A spindle unit is used for a main shaft of a machine tool, an industrial machine, or the like, and has a structure in which a rotating shaft is supported by two rolling bearings which are arranged apart in a direction along the axis of the rotating shaft. An inner ring spacer and an outer ring spacer are arranged between the two bearings. Also, each bearing has
Preload is applied to increase the rotation accuracy of the rotating shaft. This preload is adjusted by, for example, arranging two angular ball bearings, tapered roller bearings, and the like so as to face each other, and adjusting the clearance between the respective races. Also, when the preload changes,
If high rotational accuracy is required due to changes in rotational accuracy or bearing rigidity, or high-speed rotation where preload is likely to be excessive, it is necessary to measure this preload and confirm that it is in an appropriate state. There is.

Therefore, as a method of measuring the preload of the rolling bearing of the spindle unit during operation, a load sensor such as a strain gauge is mounted on a spacer disposed between stationary wheels of two rolling bearings forming the spindle unit. , A method to measure directly from the axial load applied to the spacer, and a method to measure the vibration of the rotating spindle unit, analyze the frequency, and generate the vibration due to the spring constant of the rolling bearing and the mass on the rotating side. A method of calculating a preload of a rolling bearing by calculating a natural frequency in a radial direction or an axial direction has been used.

In order to obtain a preload from vibration, a vibration sensor for detecting vibration is attached to a stationary member, and the rotating side transmitted from the rotating shaft to the stationary member through the rotating wheel of the rolling bearing, the rolling element, and the stationary wheel. There is a method of detecting vibration on the rotating side, and a method of detecting vibration on the rotating side using a non-contact displacement meter.

In order to adjust the preload, for example, in the case of a back-to-back angular ball bearing, the stationary wheels are pressed along the axis with each other, and the spacer disposed between the stationary wheels is compressed to reduce the preload. There is a spindle unit provided with a variable preload mechanism that adjusts in the direction of rotation.

[0006]

However, in order to determine the preload of a bearing having a fixed position preload, a load sensor for detecting an axial load is incorporated in a spacer disposed between stationary wheels. By applying this method, it is possible to detect the value including the tightening load by screws and bearing nuts that press the gap between the end face of the spacer and the end face of the stationary wheel without gaps, despite the fact that you originally want to detect the preload of the bearing. Resulting in.
Therefore, it is difficult to accurately measure a change in preload.

Further, in order to obtain a preload of a bearing of a spindle unit to which a constant pressure preload provided with a constant preload during use by providing a variable preload mechanism, a load sensor is provided on a spacer disposed between stationary wheels. When the incorporated method is applied, the signal detected by the load sensor is based on the load applied by compressing and contracting to reduce the preload by the preload variable mechanism, or the load applied by expanding the spacer due to temperature change May not be determined.

In the case of calculating the preload from the vibration, in the method of detecting the vibration by attaching the vibration sensor to the stationary member, the vibration on the rotating side is attenuated in the middle of the transmission path because the vibration transmission path is long. At the same time, new noise may be added, and an accurate frequency may not be measured. Further, in the method of detecting the displacement (ie, vibration) on the rotation side by bringing the non-contact displacement meter close to the member on the rotation side, the amount of displacement to be detected is small, so that accurate frequency measurement may not be possible.

Accordingly, the present invention provides a bearing preload measuring method capable of accurately measuring a preload, a spindle unit capable of obtaining a preload by applying the bearing preload measuring method, and appropriately adjusting the rotational accuracy from the obtained preload. It is an object to provide a spindle unit that performs

[0010]

SUMMARY OF THE INVENTION According to the present invention, a vibration during rotation of a rotating body supported by a bearing is detected, a natural frequency of the rotating body is obtained from the detected vibration, and the natural frequency and the vibration are calculated. The spring constant of the bearing supporting the rotating body is determined from the resulting mass and the preload of the bearing is determined from the spring constant. Is a preload measuring method for detecting the preload.

In a spindle unit having a rotating side including a rotating wheel of the bearing and a stationary side including a stationary wheel of the bearing with a rolling bearing interposed therebetween, a vibration sensor mounted on the rotating side, and the vibration sensor Propagation means for propagating the signal detected at the stationary side, the natural frequency is obtained based on the signal transmitted by this propagation means, the spring constant of the bearing from the natural frequency and the mass caused by the vibration, And a preload measuring device for obtaining the preload of the bearing from the spring constant.

Alternatively, in a spindle unit having a rotating side including a rotating wheel of the bearing and a stationary side including a stationary wheel of the bearing with a rolling bearing interposed therebetween, a vibration sensor attached to the rotating side, and the vibration sensor Propagation means for propagating the signal detected at the stationary side to the stationary side, the natural frequency of the rotating body is determined based on the signal transmitted by this propagation means, and the bearing of the bearing is determined from the natural frequency and the mass caused by the vibration. A preload measuring device that obtains a spring constant and obtains a preload of the bearing from the spring constant, and a preload variable mechanism that changes the preload of the bearing are provided, and the actual preload obtained by the preload measuring device and the target preload set in the bearing are set. The result is fed back to a variable preload mechanism to provide a spindle unit that controls the preload of the bearing.

At this time, the vibration sensor is preferably mounted on a rotating spacer disposed on the rotating side.

[0014] The propagation means includes a transmitting element provided on the rotating side and a receiving element provided on the stationary side. When both elements are antennas, the signal of the vibration sensor detected between these antennas is propagated by radio waves. Also,
When both elements are coils, the signal of the vibration sensor detected between these coils is propagated by electromagnetic induction.

The supply of power to the rotating side is performed by electromagnetic induction from a power transmitting unit coil provided on the stationary side to a power receiving unit coil provided on the rotating side, or to an armature of a generator provided on the rotating side. This can be done by the excited power.

In order to propagate the detection signal from the rotating side to the stationary side, the signal detected by the vibration sensor is modulated by a modulation circuit provided on the rotating side, and the modulated signal is transmitted from the transmitting element. The signal may be received by a receiving element, and the received signal may be demodulated by a demodulation circuit provided on the stationary side.

Further, the vibration sensor, the transmitting element, and the power receiving unit coil or the armature are mounted on a rotating side spacer provided between the two bearings, and the receiving element and the power transmitting unit coil are mounted on the stationary side. Attach to the provided stationary spacer.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. The spindle unit 1 of FIG. 1 includes a plurality of, for example, two angular ball bearings 2a, 2a.
b, a rotating shaft 3 and a housing 4. The angular ball bearings 2a and 2b are mirror-symmetrical to each other in a direction along the axis of the rotating shaft 3, that is, a back-to-back combination.
And are spaced apart from each other. And each bearing 2
The inner rings 5a and 5b, which are the rotating wheels a and 2b, are fixed to the rotating wheels together with the inner ring spacers 7a, 7b and 7c by an axial load generated by tightening the bearing nut A. In addition, the outer ring 6 which is a stationary wheel of each bearing 2a, 2b
a and 6b are fixed inside the housing 4 by a clearance fit or an interference fit. Between the inner rings 5a and 5b and on both sides in the direction along the rotating shaft 3, ring-shaped inner ring spacers 7a, 7b and 7c are arranged for positioning the inner rings 5a and 5b along the rotating shaft 3. In addition, outer ring 6
The ring-shaped outer ring spacers 8a, 8b, 8c are provided along the housing 4 between the a and 6b and on both sides in the direction along the rotating shaft 3.
Is arranged.

At the axial center of the inner race spacer 7b between the inner races 5a and 5b, there is formed a ring-shaped projection 9 formed in a radially outward direction. Further, a groove 10 is provided in a part of the center of the protrusion 9, and a vibration sensor 12 is attached to a bottom 11 of the groove 10. A protection ring 13 that covers the groove 10 is attached to the outer periphery of the projection 9.

An outer ring spacer 8b between the outer rings 6a, 6b
At the position facing the convex portion 9 of the inner ring spacer 7b,
A receiving antenna 14, which is an example of a receiving element, and an excitation ring 15 provided with a plurality of holes in an iron ring for giving a change in magnetic flux to an armature 30 of a generator are attached. The signal line 16 of the receiving antenna 14 passes through the outer ring spacer 8b and is connected to an arithmetic circuit 19 disposed outside the spindle unit 1 through a wiring lead-out path 18 provided in the housing 4.

Bearings 2a, 2b are provided at the ends of the housing 4.
The hydraulic preload variable mechanism 21 for adjusting the preload of the
2 attached. The variable preload mechanism 21 includes a lid 24 having a cylinder 23 formed in a ring shape, and a ring-shaped piston 2 inserted into the cylinder 23 of the lid 24.
5 is comprised. The piston 25 moves the outer race spacer 8a along the rotating shaft 3 with the hydraulic pressure supplied by the hydraulic device 26 connected to the arithmetic circuit 19.
Press in the direction of b, 8c.

As shown in FIGS. 2 and 3, in addition to the vibration sensor 12, a modulation circuit 27 for transmitting a signal detected by the vibration sensor 12 as a radio wave R is provided in the groove 10 of the inner ring spacer 7b. A transmitter 28, a transmission antenna 29, which is an example of a transmission element, and an armature 30 of a generator for supplying power thereto are mounted on the bottom 11. Armature 3
Reference numeral 0 designates a coil, an iron core, and a magnet, which rotates together with the rotating shaft 3 and receives a change in a magnetic field by a hole provided in an excitation ring 15 attached to an inner surface of an outer ring spacer 8b which moves relatively. Generate electricity by induction. Since the generated electric power is an alternating current, a rectifying circuit is provided after the armature 30 to supply the electric power as a direct current.

The arithmetic circuit 19 includes a receiver 31 to which the radio wave R received by the receiving antenna 14 is input as shown in FIG.
A demodulation circuit 32 for returning the received radio wave R to the original signal;
FFT (Fast FFT) for decomposing the frequency included in the signal
ourier transform (fast Fourier transform) unit 33 and an eigenvalue analyzing unit 34 for obtaining an eigenfrequency from the decomposed signal.
A preload calculating unit 35 for obtaining a preload from the obtained natural frequency, and a D / D converter for converting the obtained preload into an analog signal.
A conversion unit 36.

The hydraulic device 26 for supplying hydraulic pressure to the variable preload mechanism 21 includes a PID control unit 37 for performing PID (proportional-integral-derivative) control as an example of control by a compensation circuit, and a hydraulic valve 38 for adjusting the supplied hydraulic pressure. Have.

From the rotation side of the spindle unit 1 including the inner rings 5a, 5b of the ball bearings 2a, 2b, the ball bearing 2
spindle unit 1 including outer rings 6a, 6b
Propagation means for propagating the signal of the vibration sensor 12 to the stationary side includes a transmitter 28 and a transmitting antenna 29 on the rotating side, and a receiving antenna 14 and a receiver 31 on the stationary side. The vibration sensor 12, the propagation means and the arithmetic circuit 19 constitute a preload measuring device.

The spindle unit 1 configured as described above generates electric power in the armature 30 when the rotating shaft 3 rotates. Then, the vibration of the rotating shaft 3 is measured by the vibration sensor 12 provided on the inner race spacer 7b using the electric power. The measured signal is modulated by the modulation circuit 27 and transmitted by the transmitter 28 as a radio wave R from the transmission antenna 29 provided on the inner ring spacer 7b. The transmitted radio wave R is received by the receiver 31 from the reception antenna 14 provided at a position facing the transmission antenna 29, and is demodulated to the original signal by the demodulation circuit 32.

The method of propagating a signal is such that, instead of the transmitting antenna 29, a rotating coil as a transmitting element formed by winding a signal line around the outer peripheral surface of the inner ring spacer 7b, and the receiving antenna 14 instead of the receiving antenna 14. A stationary coil as a receiving element formed by winding a signal line is provided on the inner surface of the outer ring spacer 8b corresponding to the position of the outer periphery of the rotating coil, and a signal is transmitted from the rotating coil to the stationary coil by electromagnetic induction. It may be a method.

The signal of the vibration sensor 12 propagated to the stationary side is decomposed for each frequency component by the FFT unit 33 of the arithmetic circuit 19, and the eigenvalue analysis unit 34 obtains a natural frequency.
This natural frequency is determined by the mass of the rotating body including the rotating shaft 3,
This is a value determined by the spring constant of the bearings 2a and 2b supporting this rotating body.

Accordingly, if m: mass on the rotation side f _n : natural frequency ω _n : angular velocity of natural frequency ω _n = 2πf _n , the spring constant K of the bearing is _expressed by the following equation: K = ω _n ² × m You can ask.

If the names (model numbers) of the bearings 2a and 2b at this time are known, the internal design specifications of the bearings 2a and 2b can be known. Bearing 2 from the amount of deformation of the contact part between the moving body and the track)
The spring constants of a and 2b can be obtained by calculation. Therefore, the relationship between the preload and the spring constants of the bearings 2a and 2b is obtained in advance by calculation, and by providing this relational expression in the preload calculation unit 35, the preload can be obtained based on the spring constant K of the bearings 2a and 2b. .

Therefore, the preload calculator 35 calculates a preload based on the natural frequency obtained by the natural analyzer 34. The obtained preload is converted into an analog signal by the D / A converter 36 and output to the hydraulic device 26.

The hydraulic device 26 operates based on the input preload based on the input preload.
The opening and closing of the hydraulic valve 38 is controlled by the ID control unit 37 to adjust the pressing force of the piston 25 of the variable preload mechanism 21. At this time,
Bearings 2a, 2b of the spindle unit 1 of the present embodiment
Are arranged in a back-to-back combination, the hydraulic pressure rises, the piston 25 is pushed, and the outer rings 5a, 5b and the outer ring spacers 8a, 8b, 8c of the bearings 2a, 2b are compressed along the housing 4. The preload decreases, the hydraulic pressure decreases, and the outer races 5a, 5b and the outer race spacers 8a, 8b, 8c are reduced.
Extends along the housing, the preload increases. Since the natural frequency of the rotating body of the spindle unit 1 changes as the preload changes, it is possible to optimize the preload again and adjust the rotational accuracy by repeating the preload adjustment based on the change. it can.

That is, the spindle unit 1 can measure a change in the preload of the bearing during operation and can control the spindle unit 1 so that it always has an optimal preload state. In addition, since the spindle unit 1 detects the natural frequency of the rotating body by directly attaching the vibration sensor 12 to the inner ring spacer 7b on the rotating side, the stationary unit can measure the vibration on the stationary side, and can rotate by the non-contact displacement meter. Compared with the method of measuring the vibration on the side, the detection signal is less attenuated and noise is less, and the signal is clear. Therefore, an accurate preload can be obtained, and by adjusting the preload based on the preload, the spindle unit 1 can be adjusted.
The rotation accuracy can be improved, and the rotation speed can be increased.

The natural frequency obtained in the present embodiment is:
The natural frequency in either the radial direction or the axial direction may be used, but it is better to obtain the natural frequency in the axial direction because noise is reduced.

The vibration sensor 12 is provided in the groove 10 of the inner ring spacer.
At the same time, another sensor such as a temperature sensor may be attached, and the sensor information may be extracted by transmitting the signal in the same manner as the signal of the vibration sensor 12. If a temperature sensor is attached together with the vibration sensor 12, the temperature rise of the rotating shaft 3 due to the rotation can be accurately measured. Therefore, if this temperature value is used for adjusting the preload, the preload of the bearing can be controlled in consideration of the influence of thermal expansion and thermal contraction of the spindle unit 1 due to a temperature change.

Further, by continuously detecting the vibration and temperature during the operation of the spindle unit 1 and estimating the change of the preload from the values, more accurate control of the preload of the bearing of the spindle unit can be performed. From the detected shaft temperature, the rotating shaft 3
By estimating the amount of thermal expansion in the axial direction, and using that value to correct the relative feed amount to the workpiece, the dimensional accuracy of the workpiece can be improved.

Next, a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
The spindle unit 1 shown in the block diagram of FIG.
Instead of the transmitting antenna 29 of the embodiment, a transmitting coil 41 as a transmitting element is provided on the inner ring spacer 7b, and the receiving antenna 1
A receiving coil 42 as a receiving element is provided in the outer ring spacer 8b instead of the receiving coil 42. The power supply to the rotating side is performed by the power receiving unit coil 43 attached to the inner ring spacer 7b, the power transmitting unit coil 44 attached to the outer ring spacer 8b, and the current for generating a magnetic field in the power transmitting unit coil 44. Power supply circuit 45
And done by

In the spindle unit 1 configured as described above, the signal detected by the vibration sensor 12 of the inner ring spacer 7b is transmitted to the transmission coil 41 via the modulation circuit 27 and the transmitter 28.
Are received by the receiving coil 42 of the outer ring spacer 8 b by electromagnetic induction by the magnetic field H, and are processed by the arithmetic circuit 19. Further, the vibration sensor 1 attached to the inner ring spacer 7a on the rotating side
2. The power to the modulation circuit 27 and the transmitter 28 is supplied to the outer ring spacer 8
b of the power transmitting unit coil 44 of the inner ring spacer 7b by electromagnetic induction to generate a magnetic field.
Is supplied by exciting and generating power.

The transmitting coil 41 and the power receiving unit coil 43
If both are used as the rotating side coil, and the receiving coil 42 and the power transmitting unit coil 44 are also used as the stationary side coil, the device may be simplified.

In each of the embodiments, the outer wheel side is the stationary wheel side, and the inner wheel side is the rotating wheel side. However, the outer wheel side may be the rotating wheel side, and the inner wheel side may be the stationary wheel side. In this case, the vibration sensor 12 is attached to the outer ring spacer on the rotating wheel side.

[0041]

According to the bearing preload measuring method of the present invention,
Since vibration is detected by the vibration sensor provided on the rotating side, a clear signal with little attenuation and noise can be detected, and an accurate bearing preload can be obtained. Further, based on the preload obtained by the preload measuring method, the preload variable mechanism of the spindle unit is controlled to make the preload of the bearing an optimum preload, so that the rotation accuracy is high and the rotation speed is high. It can be a spindle unit.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a spindle unit according to a first embodiment of the present invention.

FIG. 2 is a view showing an inner ring spacer of the spindle unit of FIG. 1;

FIG. 3 is a sectional view of an inner ring spacer and an outer ring spacer along F3-F3 in FIG. 1;

FIG. 4 is a block diagram showing a signal system of the spindle unit of FIG. 1;

FIG. 5 is a block diagram showing a signal system of a spindle unit according to a second embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Spindle unit 2a, 2b ... Bearing 5a, 5b ... Inner ring (rotating wheel) 6a, 6b ... Outer ring (stationary wheel) 7b ... Inner ring spacer 8b ... Outer ring spacer 12 ... Vibration sensor 14 ... Reception antenna (Receiving element) 15 ... Excitation ring 21 ... Preload variable mechanism 27 ... Modulating circuit 28 ... Demodulating circuit 29 ... Transmitting antenna (transmitting element) 30 ... Armature 41 ... Transmitting coil 41 ... Receiving coil 43 ... Receiving coil 44 ... Transmitting unit Coil R: Radio wave H: Magnetic field

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) G08C 17/02 G08C 19/00 C 19/00 17/00 BFterm (reference) 2F073 AA35 AB12 BB02 BC02 BC10 CC01 EE12 FF02 FF03 GG01 GG04 2G024 AC02 BA08 CA11 DA03 EA11 3J012 AB04 AB07 BB03 BB05 CB05 FB10 3J101 AA02 AA42 AA54 AA62 AA81 BA71 BA77 FA01 FA24 FA26 FA41 GA31

Claims (12)

[Claims] An object of the present invention is to detect vibration during rotation of a rotating body supported by a bearing, determine a natural frequency based on the detected vibration, and obtain a spring of the bearing from the natural frequency and a mass caused by the vibration. A method for measuring a constant, and obtaining a preload of the bearing from the spring constant, wherein the vibration is detected by a vibration sensor provided on a rotating side including a rotating wheel of the bearing. Measuring method. 2. A spindle unit having a rotating side including a rotating ring of the bearing and a stationary side including a stationary ring of the bearing, with a vibration sensor attached to the rotating side; Propagation means for transmitting a signal detected by the vibration sensor to a stationary side,
Preload measurement for obtaining a natural frequency based on a signal transmitted by the propagation means, obtaining a spring constant of the bearing from the natural frequency and a mass caused by the vibration, and obtaining a preload of the bearing from the spring constant. A spindle unit comprising a device. 3. A spindle unit having a rotating side including a rotating wheel of the bearing, and a stationary side including a stationary wheel of the bearing, with a vibration sensor attached to the rotating side; Propagation means for transmitting a signal detected by the vibration sensor to a stationary side,
Preload measurement for obtaining a natural frequency based on a signal transmitted by the propagation means, obtaining a spring constant of the bearing from the natural frequency and a mass caused by the vibration, and obtaining a preload of the bearing from the spring constant. Device, comprising a preload variable mechanism for changing the preload of the bearing, comparing the measured preload determined by the preload measurement device with a target preload preset for the bearing, and the result is sent to the preload variable mechanism. A spindle unit for controlling the preload of the bearing by feedback. 4. The spindle unit according to claim 2, wherein the rotating side includes a rotating spacer, and the vibration sensor is attached to the rotating spacer. 5. The apparatus according to claim 2, wherein said propagation means includes a transmitting element provided on said rotating side and a receiving element provided on said stationary side. A spindle unit according to the item. 6. The spindle unit according to claim 5, wherein both the transmitting and receiving elements are antennas, and the signal of the vibration sensor is propagated between them by radio waves. 7. The spindle unit according to claim 5, wherein both the transmitting and receiving elements are coils, and a signal of the vibration sensor is propagated between the coils by electromagnetic induction. 8. The power supply to the rotating side is performed by electromagnetic induction from a power transmitting unit coil provided on the stationary side to a power receiving unit coil provided on the rotating side. The spindle unit according to claim 7. 9. The power supply to the rotating section uses power excited by an armature of a generator provided on the rotating side. Item 2. The spindle unit according to item 1. 10. A signal detected by the vibration sensor is modulated by a modulation circuit provided on the rotation side, the modulated signal is transmitted from the transmitting element, and the transmitted signal is received by the receiving element. 10. The spindle unit according to claim 5, wherein the received signal is demodulated by a demodulation circuit provided on the stationary side. 11. The vibration sensor, the transmitting element, and the power receiving unit coil or the armature are disposed between rotating wheels of at least two bearings provided between the rotating side and the stationary side. The spindle unit according to any one of claims 5 to 10, wherein the spindle unit is attached to the rotating side spacer. 12. The stationary element according to claim 1, wherein the receiving element and the power transmitting unit coil are mounted on the stationary side spacer between at least two stationary wheels of a bearing provided between the rotating side and the stationary side. 5. The device according to claim 5, wherein the device is attached.
The spindle unit according to any one of 0.