JP2004219147A - Spindle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spindle device equipped with rotation detectors that can realize high angular resolution without increasing the diameter of a tone ring and, in addition, can also detect the rotating direction of a spindle shaft. <P>SOLUTION: The rotating speed and rotating direction of the spindle shaft 11 of this spindle device 10 are detected by means of the tone ring 18 provided in an inner ring spacer 16 and two rotation detectors 30 which output signals corresponding to the recessed and projecting shape of a recessed and projecting tooth section provided on the tone ring 18 by detecting the tooth section and, at the same time, are divided from each other. In addition, the rotation detectors 30 are constituted of MR sensors 19 and sensor holders 20 provided in an outer ring spacer 17 so that the phases of the output signals of the detectors 30 may be deviated from each other by a 1/4 period. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a spindle device, and more particularly to a spindle device provided with a rotation detector that detects rotation of a spindle shaft of a machine tool, an industrial machine, or the like, such as a rotation speed and a rotation direction.
[0002]
[Prior art]
BACKGROUND ART Conventionally, there is a spindle device used for a machine tool, an industrial machine, or the like, which is provided with a detector (speed sensor) for detecting a rotation speed of a spindle shaft (for example, see Patent Document 1).
In general, a spur gear-shaped tone ring made of a magnetic material is attached to a spindle shaft, and a detection element (for example, an electromagnetic pickup coil, a Hall element, an MR sensor, etc.) disposed close to the outer periphery of the tone ring. ) Outputs a signal corresponding to a change in magnetic flux due to the uneven teeth on the outer peripheral surface of the tone ring, and detects the rotation speed based on the output signal. This method is widely used because it is hardly affected by dirt such as lubricating oil.
[0003]
On the other hand, in the case of a spindle device incorporated in a machine tool that needs to perform not only the rotation speed detection but also the angular positioning of the spindle shaft, a detector having a plurality of the detection elements built therein or a shaft end portion of the spindle shaft. A method of attaching a rotary encoder is widely used.
[0004]
[Patent Document 1]
JP-A-1-51256 (page 3, FIG. 1)
[0005]
[Problems to be solved by the invention]
By the way, as machine tools have become faster and more intelligent in recent years, spindle devices are required not only to operate at higher speeds, but also to have higher responsiveness during acceleration / deceleration and a lower rate of rotation speed fluctuation during load fluctuations. I have. For that purpose, it is necessary to increase the speed loop gain of the control device, and a rotation speed signal having a high angular resolution is required.
[0006]
However, since the tone ring module (pitch diameter / number of teeth) that can be detected by the conventional speed sensor as described above is usually about 1 to 3, the diameter of the tone ring is increased in order to achieve high angular resolution. There is a need to. For example, when the angular resolution is required to be divided into 512, it is necessary to attach a large-diameter tone ring having a diameter of at least 514 mm to the spindle shaft.
[0007]
Such a large-diameter tone ring causes not only centrifugal destruction but also a large increase in the mass of the rotating member, which may reduce the critical speed range of the spindle device and make high-speed rotation difficult. .
On the other hand, there is a speed sensor in which the module can use a fine tone ring such as 0.15, but the air gap between the tone ring and the speed sensor is as small as about 0.1 mm, and the allowable value of the mounting error is small. Therefore, it is very difficult to assemble the spindle device. Further, the output of the speed sensor may be disturbed or may not be output due to a dimensional change due to a temperature change or the like.
[0008]
Also, since the response speed of the speed sensor is about 100 kHz at the highest, the rotation speed can be detected only up to about 12000 rpm when the angular resolution is set to 512 divisions. In this case, it is not possible to cope with a high-speed spindle device exceeding 20,000 rpm required in recent machine tools.
[0009]
Furthermore, since the rotation speed sensor cannot determine the rotation direction of the spindle shaft, it is difficult to perform the positioning of the spindle shaft angle by closed-loop control when performing drilling indexing or keyway alignment when chucking a tool. .
On the other hand, in the case where a rotary encoder is attached to a shaft end of a spindle or a detector having a plurality of built-in detection elements, the rotation direction of the spindle can be determined, so that the angle can be positioned by closed loop control.
However, in the case of a detector having a plurality of built-in detection elements, the distance between the detection elements is fixed, so that the tone ring module cannot be changed freely, and the angular resolution is determined by the size of the spindle. Would. Further, when a rotary encoder is attached to the shaft end of the spindle, the overhang of the spindle shaft from the bearing portion increases, so that not only the critical speed range decreases, but also the spindle shaft runout due to rotational imbalance increases. The problem arises.
[0010]
Accordingly, an object of the present invention is to solve the above-described problems, and a rotation detector capable of realizing a high angular resolution without increasing the diameter of a tone ring and capable of detecting the rotation direction of a spindle shaft. The object of the present invention is to provide a spindle device provided with:
[0011]
[Means for Solving the Problems]
The object of the present invention is to separate the tone ring provided on the rotating side member and the uneven tooth provided on the tone ring and output a signal corresponding to the unevenness by detecting the uneven tooth portion. And the rotation of the spindle shaft is detected by two or more rotation detectors having a detection element disposed on the stationary member so that the phase of the output signal is shifted. Is done.
[0012]
According to the spindle device having the above-described configuration, two or more rotation detectors output output signals that are out of phase with each other, so that output signals of a plurality of phases can be obtained.
Thus, for example, when the output signal of the detection element is a pulse train output, a pulse signal having an angular resolution that is multiplied by the number of teeth of the tone ring can be obtained by the multiplying circuit. If the output signal of the detection element is an analog output, each output signal is compared with an arbitrary threshold value to determine whether each output signal is larger or smaller than the threshold value, and the pulse signal is detected as a pulse train output. As in the case of using the output detection element, a pulse signal having an angular resolution that is multiplied by the number of teeth of the tone ring (the number of detection elements) can be obtained.
Furthermore, a rotation direction detection signal can be obtained by detecting the phase difference between the rise and fall of the output signals of the two rotation detectors.
[0013]
Therefore, it is possible to obtain an angular resolution greater than the number of teeth of the tooth portion of the tone ring, and it is possible to realize a high angle resolution function without increasing the diameter of the tone ring while maintaining the module of the tone ring. , The rotation direction can be detected.
[0014]
Preferably, when the number of the rotation detectors is n, the output signal corresponding to the uneven tooth portion of the tone ring is relatively １ ／ n cycle. They are arranged so as to be out of phase with each other.
Further, when the output signal of the detection element is a pulse train output, a rectangular wave having a duty ratio of about 50% (preferably ± 5% or less) is output, and when the output signal of the detection element is an analog output, a sine wave ( (A waveform distortion rate of preferably 1% or less) is preferably output.
In these cases, since the periodic error of each output signal can be reduced, the detection accuracy can be improved.
[0015]
Further, it is preferable that the tone ring and the two or more rotation detectors are disposed between front and rear bearings of the spindle device.
In this case, the shaft runout of the spindle shaft due to the reduction of the critical speed range and the rotational imbalance can be prevented, and the axial length can be suppressed, so that the spindle device can be made compact.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a spindle device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a longitudinal sectional view for explaining a spindle device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG.
[0017]
As shown in FIG. 1, the spindle device 10 of the present embodiment has a pair of front and rear bearings 13 and 14 that are axially separated from each other at two places between a spindle shaft 11 and an outer cylinder 12. And rotatably supports the spindle shaft 11.
Further, a water-cooling jacket 15 is externally fitted to the outer cylinder 12. Between the inner rings of the front and rear bearings 13 and 14, an inner ring spacer (rotating member) 16 composed of inner ring spacer divisions 16a and 16b is disposed. Between the outer rings of the front and rear bearings 13 and 14, an outer ring is provided. A spacer (stationary member) 17 is provided.
[0018]
At a substantially central portion of the inner race spacer 16 in the axial direction, a spur gear-shaped tone ring 18 (in this embodiment, module 1, 128 teeth) made of a magnetic material is provided. It is tightly fitted to the spindle shaft 11 so as to be sandwiched between the divided bodies 16a and 16b, and the uneven tooth portion of the tone ring 18 is detected on the inner diameter side of the corresponding outer ring spacer 17 to detect the unevenness. A rotation sensor 30 constituted by an MR sensor (detection element) 19 for outputting a corresponding signal and a sensor holder 20 are divided from each other, and two rotation detectors are arranged so that the phase of the output signal is shifted.
[0019]
The uneven shape of the tooth portion of the tone ring 18 is such that when the output signal of each MR sensor 19 is a pulse train output, a rectangular wave having a duty ratio of approximately 50% (preferably ± 5% or less) is output. In the case of an analog output, a sine wave (having a waveform distortion rate of preferably 1% or less) is preferably output because a periodic error is reduced and detection accuracy is improved. However, the uneven shape of the tooth portion in the tone ring of the present invention is not limited to this.
[0020]
It is also possible to form the inner ring spacer and the tone ring integrally by directly providing the toothed portion of the uneven shape on the outer diameter portion of the inner ring spacer. In this case, a part of the outer diameter portion of the inner ring spacer may be increased in diameter, and a spur gear-shaped tone ring may be formed in that portion. A tone ring may be formed by engraving a groove in the outer diameter portion of the cylindrical inner race spacer. It is preferable to provide the teeth directly on the inner ring spacer, because the number of parts can be reduced.
[0021]
Further, the mounting position of the tone ring 18 on the rotating side member is not particularly limited, but it is preferable that the tone ring 18 is provided at a location where overhang from the front and rear bearings 13 and 14 is as small as possible. For example, as shown in FIG. 1, by disposing the tone ring 18 between the front and rear bearings 13 and 14, it is possible to prevent the spindle shaft 11 from oscillating due to a reduction in the critical speed range and a rotational imbalance, Further, since the length in the axial direction can be suppressed, the spindle device can be made compact, which is preferable.
[0022]
Each of the MR sensors 19 is disposed together with a magnet in a hole of an arc-shaped sensor holder 20. When arranging the MR sensor 19 in the hole of the sensor holder 20, it is preferable to mold the inside of the sensor holder 20 with a silicone resin, an epoxy resin, or the like because the MR sensor 19 is not affected by lubricating oil or the like.
[0023]
It is not necessary to use the sensor holder 20 as long as the detection element is originally protected by a metal case or the like. The detection element used is not limited to the MR sensor 19, but may be any element that can detect the uneven shape of the tone ring 18, such as a Hall element or an electromagnetic pickup coil.
[0024]
In the sensor holder 20, as shown in FIG. 2, the output signals of the two MR sensors 19 are relatively shifted in phase by １ ／ cycle (the number of sensors n = 2, ｎn =＝ cycle). Thus, the outer ring spacer 17 is fixed to the inner diameter side of the outer ring spacer 17 by bolts or the like. It is preferable that at least one screw hole for fixing the sensor holder 20 provided in the outer race spacer 17 is a long hole whose longitudinal direction is set in the circumferential direction, since phase adjustment at the time of assembly is simplified.
[0025]
Further, when the shape of the sensor holder 20 is an annular shape, it is possible to fix the sensor holder 20 using the set screw only by providing at least one tapped hole in the outer ring spacer 17 and to easily adjust the phase. Is preferable.
In any case, when two rotation detectors 30 are used as in this embodiment, at least one rotation detector 30 is mounted in a manner that allows phase adjustment, thereby absorbing a mechanical phase error. Of course, even when the number of teeth of the tone ring 18 is increased or decreased (for example, 100) to change the angular resolution, the outer diameter of the tone ring 18 and the mounting position of the rotation detector 30 in the radial direction are also possible. Can be dealt with simply by changing only the module of the tone ring 18 and adjusting the output signals of the two MR sensors 19 so that their phases are relatively shifted by 1/4 cycle.
[0026]
In the present embodiment, two sensor holders 20 are overlapped in the axial direction and brought as close as possible so that the sensor wiring hole 21 of the outer cylinder 12 is formed at one place and the sensor wiring 22 is formed as one multi-core electric wire. However, when the tone ring is installed outside the outer cylinder, such as when the sensor holder is installed with a high degree of whiteness, it should be placed on the same plane in the axial direction without overlapping in the axial direction. You may set it. By doing so, the axial thickness of the tone ring can be reduced by the amount that the sensor does not overlap in the axial direction, so that the overhang amount of the spindle shaft 11 can be reduced and the weight increase of the rotation side member can be reduced.
[0027]
As shown in the figure, it is preferable to use a connector 23 or a terminal block for the electrical connection between the sensor wiring 22 and the MR sensor 19 because disassembly during assembly and maintenance of the spindle device 10 is simplified. In particular, in the spindle device 10 of the type in which the water-cooling jacket 15 is mounted on the outer cylinder 12 as in the present embodiment, when it is necessary to close the sensor wiring hole 21 with the faucet plug 24, the wiring work is performed in a recessed portion. The effect is great because it needs to be done.
[0028]
In other words, according to the spindle device 10 configured as described above, the two MR sensors 19 output output signals having different phases, respectively. In the case of pulse train output, the output is equivalent to the A and B phases of the rotary encoder. A two-phase output signal can be obtained.
Therefore, the rising edge and the falling edge of each signal are detected by the multiplying circuit of the control device 31, so that the pulse having the angular resolution of twice (two or four times) the number of teeth of the tone ring 18 is obtained. You can get a signal.
[0029]
Accordingly, when the response speed of the MR sensor 19 to be used is 100 kHz, it is possible to detect a rotation speed exceeding 45000 rpm even though the angular resolution of the tone ring 18 is 512 divisions.
That is, it is not necessary to increase the diameter of the tone ring 18 while maintaining the module of the tone ring 18, and it is possible to prevent centrifugal destruction and a large increase in the mass of the rotating side member, thereby lowering the critical speed range of the spindle device 10. A high angular resolution can be realized without the need.
[0030]
On the other hand, even when the MR sensor 19 has an analog output, each output signal is compared with an arbitrary threshold to determine whether each output signal is larger or smaller than the threshold, and is detected as a pulse train output. As in the case where the MR sensor having the pulse train output is used, a pulse signal having twice or four times the angular resolution can be obtained.
Also, assuming that the respective output signals are sin θ and cos θ,
U = sin θ
V = sin θ · cos (2/3) π + cos θ · sin (2/3) π
W = sin θ · cos (4/3) π + cos θ · sin (4/3) π
Calculates by the formula, and generates U-, V-, and W-phase three-phase sinusoidal signals whose phases are shifted by 1/3 cycle, and detects points of electrical angles 0 ° and 180 ° of each signal, thereby increasing the frequency by 6 times. A pulse signal having the following angular resolution can be obtained. If the signal is further subdivided, it can be infinitely multiplied. However, unless the output signal of the MR sensor 19 is a perfect two-phase sine wave, a cyclic error occurs. Is good.
[0031]
Further, the controller 31 detects the rising or falling phase difference (leading phase difference, lagging phase difference) of the output signals of the two MR sensors 19 irrespective of the pulse train or the analog signal, so that the rotation direction detection signal is obtained. Since it can be obtained, the rotation direction can be detected.
Further, since the two rotation detectors 30 are separated from each other, it is possible to adjust the phase at the time of assembling, and also to change the module of the tone ring 18 to adjust the phase when changing the angular resolution. Only can be dealt with. Furthermore, with a rotation detector having a plurality of built-in detection elements, only a certain module can be used, which makes it impossible to achieve an arbitrary angular resolution regardless of the size of the spindle device.
[0032]
By using these signals, not only when a servo motor is used as a motor but also when an induction motor is used, a rotary encoder can be mounted by using an inverter device having a vector control or an orientation control function. Although it is possible to position the spindle axis by a closed loop without any problem, the overhang from the bearing portion is not increased by the rotary encoder, so that the runout of the spindle shaft 11 due to the rotational imbalance can be reduced.
[0033]
Note that the configurations of the rotating side member, the stationary side member, the tone ring, the detecting element, the spindle shaft, and the like according to the spindle device of the present invention are not limited to the configuration of the above-described embodiment, but are based on the gist of the present invention. Needless to say, various forms can be adopted.
[0034]
For example, in the spindle device 10 of the above-described embodiment, the case where two MR sensors 19 as detection elements are arranged is taken as an example. However, if the number of detection elements is increased to three or four, the angular resolution becomes tone. In the case of pulse train output, the number of teeth of the ring 18 is increased to 6 times and 8 times, and in the case of analog output, the cycle error at the time of high multiplication becomes smaller.
Further, in the above embodiment, the spindle device 10 having no motor is used. However, it goes without saying that the present invention can be applied to a built-in type spindle device having a motor built in the spindle device.
[0035]
【The invention's effect】
As described above, according to the spindle device of the present invention described above, since two or more rotation detectors output output signals having different phases, it is possible to obtain multi-phase output signals.
Thus, for example, when the output signal of the detection element is a pulse train output, a pulse signal having an angular resolution that is multiplied by the number of teeth of the tone ring can be obtained by the multiplying circuit. Further, when the output signal of the detection element is an analog output, each output signal is compared with an arbitrary threshold to determine whether each output signal is larger or smaller than the threshold, and by detecting it as a pulse train output, As in the case of using the pulse train output detection element, a pulse signal having an angular resolution that is multiplied by the number of teeth of the tone ring (the number of detection elements) can be obtained.
[0036]
Furthermore, a rotation direction detection signal can be obtained by detecting the phase difference between the rise and fall of the output signals of the two rotation detectors.
Therefore, since it is possible to obtain an angular resolution equal to or greater than the number of teeth of the tooth portion of the tone ring, it is possible to realize a high angle resolution function without increasing the diameter of the tone ring while maintaining the module of the tone ring. , The rotation direction can be detected.
[0037]
Therefore, it is not necessary to increase the diameter of the tone ring while maintaining the module of the tone ring, and it is possible to prevent centrifugal destruction and a significant increase in the mass of the rotating side member. Resolution can be realized.
Also, since the rotation direction of the spindle shaft can be detected, the spindle shaft angle can be positioned by closed-loop control without attaching a rotary encoder, but the rotary encoder does not increase overhang from the bearing. In addition, the runout of the spindle shaft due to the rotational imbalance can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view for explaining a spindle device according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along the line II-II in FIG.
[Explanation of symbols]
Reference Signs List 10 Spindle device 11 Spindle shaft 12 Outer cylinders 13, 14 Rolling bearing 16 Inner ring spacer (rotary side member)
17 Outer ring spacer (static side member)
18 Tone ring 19 MR sensor (detection element)
30 rotation detector 31 controller

Claims (3)

The tone ring disposed on the rotating side member and the uneven tooth portion provided on the tone ring are detected and output a signal corresponding to the unevenness, and are separated from each other, and the phase of the output signal is A spindle device, wherein rotation of a spindle shaft is detected by two or more rotation detectors having detection elements disposed on a stationary member so as to be shifted. When the number of the rotation detectors is n, the output signals corresponding to the uneven tooth portions of the tone ring are relatively out of phase with each other by a period of 1 / 2n. The spindle device according to claim 1, wherein the spindle device is arranged as follows. The spindle device according to claim 1, wherein the tone ring and the two or more rotation detectors are disposed between front and rear bearings of the spindle device.

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