JPH046495B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring synchronization accuracy of synchronously rotating rotary axes of NC machine tools.

The synchronization accuracy of the rotation of the hob shaft and table shaft of a hobbing machine, which is a type of gear cutting machine tool for machining transmission gears for passenger cars or reduction gears for construction machinery, is extremely important in terms of machining accuracy. However, a method for easily measuring this synchronization accuracy has not yet been established. For this reason, the current situation is that the synchronization accuracy must be specifically estimated after processing from the processed workpiece, or it must be measured by an expert using a high-grade specialized measuring instrument.

Currently, when using a measuring instrument to measure the synchronization accuracy of a hobbing machine, the usual method is to attach an optical encoder to the hob shaft and table shaft via a special jig. Rotate these axes,
This measures the phase lead/lag of the output pulses from both encoders. This method requires skill and man-hours to attach the encoder, and requires work to attach and detach the encoder every time a measurement is made. Furthermore, there was a drawback that errors and reproducibility of measurement data for each measurement due to inaccuracy in centering were problematic.

The present invention was made in view of the difficulty in measurement, and uses signals from a rotation control device that is always installed on the drive shaft of today's NC hobbing machines to connect the hob shaft and table shaft. The purpose of this paper is to provide a method for measuring the synchronization accuracy of rotary axes of NC machine tools that require synchronized rotation.

The method for measuring the synchronization accuracy of synchronously rotating rotating axes of NC machine tools according to the present invention achieves the above object.
Using the output signal of the position detector that outputs the feedback signal of the rotation control device installed on each of the two synchronously rotating axes of the NC machine tool, the output signal of each position detector is divided into a common signal by a frequency divider. This method is characterized in that the synchronization accuracy of the two axes is measured by converting the rotation into frequency pulses and comparing the phases of these two frequency pulses using a rotation accuracy measuring device.

It is very important to investigate the synchronization accuracy of the rotation of the hob shaft and table shaft of a hobbing machine. Also
It is equally important for NC hobbing machines. Particularly at production sites, it is important to know in a short time whether each control device and the mechanical elements used are correctly installed and functioning normally. The NC hobbing machine is equipped with a position detector (encoder, resolver, etc.) that outputs a feedback signal to feedback control the rotation of the drive unit of each axis of the hobbing machine. By using this feedback signal for measurement as well, there is an advantage that there is no need to install a separate expensive encoder, and that synchronization accuracy can be easily measured on site. The use of encoders or resolvers permanently mounted on each drive shaft also guarantees the reproducibility of the measurement data for each gear cutter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for measuring the synchronization accuracy of synchronously rotating rotating shafts of a machine tool according to the present invention will be described with reference to the drawings of an embodiment.

FIG. 1 shows an example of an NC hobbing machine to which the present invention can be applied. In FIG. 1, 1 is a hob shaft, 2 is a table shaft, and 3 is a workpiece. In the present invention, signals from a servo converter attached to a hob shaft drive motor and a table shaft drive motor are used. Figures 2 and 3 show side views of the drive motor and servo converter. show. In Figures 2 and 3, 4
is a motor for driving a hob shaft or table shaft, and may be an AC motor or a DC motor. A tacho generator 5 for speed information feedback and an optical encoder or resolver 6 for position information feedback, which are servo converters, are attached to the shaft end of the motor 4 on the opposite side from the load. In addition, FIG. 3 shows that the arrangement relationship between the optical encoder or resolver 6 and the motor 4 is second.
This is an example different from the one shown in the figure.

FIG. 4 shows a circuit configuration diagram of a synchronous accuracy measuring circuit that implements the synchronous accuracy measuring method of synchronously rotating rotary axes of an NC machine tool according to the present invention. In FIG. 4, 6 ₁ and 6 ₂ are optical encoders attached to the drive motor 4 of the hob shaft 1 and the table shaft 2, and 6 ₃ is a resolver. 7 and 8 are frequency dividers,
9 and 10 are differential amplifiers, 11 is a phase difference generator, 1
2 is a crystal oscillator, 13 is an arithmetic unit, 14 is an arithmetic unit,
15 is a memory, and 16 is a D/A converter. Further, 17 is a command pulse generator in the NC device, 18 is a phase discriminator, 19 is a D/A converter, 20 is a motor drive amplifier, and 21 is a pulse converter.

First, the measurement principle will be described in the case of an NC gear cutting machine in which both the hob shaft 1 and table shaft 2 use optical encoders. Feedback signals output from encoders 6 ₁ and 6 ₂ are input, and these are input to 7 and 8 so that the pulse frequencies match.
input to the frequency divider. Frequency dividers 7 and 8 convert these inputs into pulse signals a and b of the same period, and after amplification by differential amplifiers 9 and 10, respectively, a phase difference signal generator 11 converts the two pulse signals into phase difference pulse signals C.
Convert to Here, the frequency division ratios of the frequency dividers 7 and 8 will be explained. The hob rotation speed is n, the work table rotation speed is N, the number of workpiece teeth is Z, the number of hob openings (number of threads)
In the case of a spur gear, there is a relationship of N=n.g/Z. Furthermore, it is assumed that the encoders 6 ₁ and 6 ₂ are directly connected to the hob and the work table, respectively, and the number of pulses of the encoder 6 ₁ on the hob side is p (pulses/rev.) per one revolution of the hob, and the number of pulses of the encoder 6 1 on the hob side is p (pulses/rev.) per rotation of the hob, and the encoder 6 1 on the work table side is, for example, 6 Let the number of pulses of ₂ be P (pulses/rev.) per revolution of the work table.
At this time, the frequency division ratio of the frequency divider 7 on the hob side is 1/A,
The frequency division ratio 1/B of the frequency divider 8 on the work table side is:
Each value N, n, P, so that the ratio below is an integer ratio
It can be obtained by selecting p, A, and B.

N・P・A: n・p・B The phase difference signal generator 11 inputs the pulse signals a and b obtained by frequency-dividing and amplifying the output signals of both the encoders 6 ₁ and 6 ₂ as described above. It outputs a phase difference pulse signal c, which is a high level pulse from the rise of pulse signal a from one differential amplifier 9 to the rise of pulse signal b from the other differential amplifier 10. Output a signal. This pulse signal is a phase difference pulse signal c, and the high level period is nothing but the phase difference θ.

The high level period θ of this phase difference pulse signal c
Since the phase difference becomes θ/t _i from the period t _i of the pulse signal b, the calculation units 13 and 14 perform calculation processing to measure the phase difference signal amount.

First, the arithmetic unit 13 calculates the reciprocal 1/ _{t i of} the period t i of the pulse signal b of the encoder 6 ₂ after frequency division using the signals from the differential amplifier 10 and the crystal oscillator 12 .

That is, the arithmetic unit 13 inputs the pulse signal b from the differential amplifier 10 and the clock pulse generated by the crystal oscillator 12, counts the rising time of the pulse signal b using the clock pulse, and calculates the reciprocal of the period t _i by 1/ Find t _i . This process is performed every cycle of pulse signal b. Therefore, for example, even if the period of pulse signal b changes, that is, even if the rotational speed of the hob and work table changes, there will be a time delay of one period.
It is possible to track and perform measurement calculations using t _i . In addition,
In reality, t _i is obtained by changing the clock pulse frequency of the crystal oscillator 12 in proportion to the frequency 1/ _{t i} of the pulse signal b. Output a signal.

The arithmetic unit 14 calculates the amount of phase difference by calculating 1/t _i ×θ, and the output pulse of the arithmetic unit 13 is used only while the phase difference pulse signal c output by the phase difference signal generator 11 is at a high level. By counting the number, the calculation 1/t _i ×θ is performed. As a result, the amount of phase difference signal that is maximum when θ is 360° and becomes 0 when θ is 0° can be measured as a numerical value.

The calculation result 1/t _i ×θ of the calculation unit 14 is temporarily stored in the memory 15, and converted into an analog quantity by the D/A converter 16 and output. This analog output is proportional to the rotational phase difference (angle) between the hob shaft 1 and the table shaft 2.

Next, the measurement principle will be described for the case where one or both of 6 ₁ and 6 ₂ is a resolver. Resolver 6 ₃
The output cannot be directly input to the rotational accuracy measuring device surrounded by the dotted line after the frequency dividers 7 and 8. However
The phase signal (error output for control) between the feedback signal from the resolver ₆₃ and the command pulse from the command pulse generator 17 calculated by the phase discriminator 18 inside the NC device (inside the dotted line box at the bottom of Figure 4) is D/
The signal is converted into an analog signal by the A converter 10, amplified by the drive amplifier 20, and used to drive the motor. In the present invention, the above phase difference signal obtained from the feedback signal from the resolver ₆₃ of the NC device is code-converted by the pulse converter 21, and then converted to the frequency divider 8.
is inputting to. Furthermore, the encoder 6 ₁ is connected to the frequency divider 7.
Assume that the signal is input. These input signals are input to the rotational accuracy measuring device via frequency dividers 7 and 8, and an output proportional to the rotational phase difference is obtained as in the case of an encoder.

According to the present invention, the synchronization accuracy of the rotation of the hob axis and table axis can be similarly measured even if the position detector installed on the synchronous rotating axis of an NC machine tool is not only an optical encoder but also a resolver. I can do it.

In the synchronization accuracy measurement method according to the present invention, if the position detectors attached to the hob shaft and table shaft drive motor are both optical encoders,
After being converted into pulses of the same frequency by the frequency dividers 7 and 8, the rotation accuracy can be directly measured using a conventional rotational accuracy measuring device surrounded by a dotted line in FIG. FIG. 5 shows signals a and b obtained by dividing the output signals of the optical encoders 6 ₁ and 6 ₂ by the frequency dividers 7 and 8 so that the frequencies of both pulses match. After amplification by the differential amplifiers 9 and 10, the phase difference signal generator 1
1, a phase difference signal c shown in FIG. 5 is obtained. Based on the phase difference signal c and the pulse period of the signals a and b, digital calculation is performed using the crystal oscillator 12, arithmetic unit 13, and arithmetic unit 14, and the result is stored in the memory 15.
to be memorized. This stored data is proportional to the phase difference (angle), and is output by the D/A converter 16 as an analog quantity d proportional to the pulse width of the signal c shown in FIG.

If the position detector is a resolver, the resolver's feedback signal is a signal whose phase is shifted by the angle of the resolver's rotor, so it cannot be directly input to the frequency divider like an optical encoder signal. Therefore, we focused on the fact that in the NC device, the phase discriminator 18 generates a phase difference signal between the resolver feedback signal and the command signal, and this signal is used. As shown in Figure 6, this phase difference signal has a constant frequency (several hundred Hz), and its pulse width changes as shown in A, B, and C depending on the discrepancy between the resolver rotation angle and the command value. It is something. That is, the falling timing of this pulse indicates the actual rotational position of the resolver when the resolver is apparently rotating at a constant rate. Therefore, the pulse converter 21 converts the polarity of this phase difference signal, offsets it, amplifies it, or attenuates it, and converts it into the signal shown in FIG. 6, that is, a signal having rotational deviation information at the rising edge, like the encoder output. . FIG. 7 shows a circuit of the pulse converter 21 that converts the phase difference signal of the resolver of ±11 V into an inverted signal of +5 V TTL level (the signal shown in FIG. 6). By inputting this signal to a frequency divider, processing is performed in exactly the same way as in the case of an optical encoder.

The measurement of the synchronization accuracy of the synchronously rotating rotary axes of an NC machine tool according to the present invention is a simple method of measuring the rotational synchronization accuracy by also using the feedback signal of the position detection device for drive control of the NC machine tool. Yes, there is no need for high-end specialized measuring equipment, and it is no longer necessary to ask an expert to take measurements.

In the present invention, whether the position detection device is an encoder or a resolver, these outputs are converted into pulses of the same frequency by a frequency divider, and the phase difference between these is input to a conventional rotation accuracy measuring device. This makes it possible to measure the

According to the present invention, the synchronization accuracy of the rotation of two axes of an NC hobbing machine etc. can be easily and accurately measured.
It can be widely applied to test research of NC machine tools that involve synchronous rotation such as NC hobs, and performance tests on actual machines.

[Brief explanation of drawings]

Fig. 1 is a side view of an example of an NC hobbing machine to which the present invention can be applied, Figs. 2 and 3 are side views of a drive motor and a servo converter, and Fig. 4 is an NC hobbing machine according to the present invention.
Figures 5, 6, and 6 are block diagrams of a synchronous accuracy measurement circuit that implements a method for measuring synchronous accuracy of synchronously rotating rotary axes of machine tools, showing waveforms of the main parts of the circuit shown in Figure 4. 7 are circuit diagrams of the pulse converter. In the drawing, 1 is the hob shaft, 2 is the table shaft, 6 ₁ ,
6 ₂ is an encoder, 6 ₃ is a resolver, 7 and 8 are frequency dividers, 17 and 18 are a command pulse generator and phase separator in the NC device, and 21 is a pulse converter.

Claims (1)

[Claims] 1 Using the output signals of position detectors that output feedback signals for drive control, which are loaded on each synchronously rotating rotating shaft of an NC machine tool, the output signals of each position detector are shared by a frequency divider. convert it into a pulse with a frequency of
A method for measuring the synchronization accuracy of synchronously rotating rotary axes of an NC machine tool, the method comprising measuring the synchronization accuracy of the two axes.