JPS6125750A - Digital feeding system - Google Patents

Abstract

PURPOSE:To improve the reliability under malfunction by constructing such that an alarm is produced when the difference between the number of pulses for feed detection obtained from a rotary position signal corresponding with the rotary position of rotor to be fed from a servo motor and the number of frequency division pulse signals will exceed over predetermined level. CONSTITUTION:Rotary position signal (en) of rotor for controlling the polarity and the phase of the output voltage (d) of a servo amplifier 2 is produced from a brushless servo motor 11 then converted through signal processing circuit 7n into a feed detection pulse signal (in) and provided to safety addition/subtraction cunter 8. While frequency division signal (h) of feeding amount command pulse signal (b) is provided to said counter 8 such that same number of pulses with the feed detection pulse signals can be achieved. Consequently, he difference between said signals (h) and (in) is lower than predetermined level under normal operation and upon exceeding over predetermined level, it is decided to be malfunction to produce an alarm K. With such arrangement, the reliability of malfunction detecting performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital feeding device that has been improved to improve reliability in the event of a failure.

In the conventional digital feeding device, as shown in FIG. The signal output C is transmitted to the servo amplifier 2, and the servo motor 3 is rotated by the output voltage d of the servo amplifier 2. A speed generator 4 is mounted on the shaft on the anti-load side of the servo motor 3. A shaft encoder 5 and a gear-shaped metal fitting 9 are attached, and a proximity switch 10 is provided opposite the gear-shaped metal fitting 9. The generated voltage output f of the speed generator 40 is input to the servo amplifier 2, and the pulse output g of the shaft encoder 5 is input to the addition/subtraction count circuit 1 as a feedback pulse signal. In addition, the signal e generated by the proximity switch 10 facing the gear-like metal fitting 9 rotating on the shaft of the motor is waveform-shaped and pulsed by the signal processing circuit 7 to form a repeated detection pulse signal, and this pulse signal 1 is safe. It is input to the subtraction input terminal of the addition/subtraction counter 8.

In such a digital feeder, the feed amount command pulse signal has a preset number of pulses and a feedback Hals (No. 8 g).
The signal output C is outputted and the feeding operation is performed until the difference in the number of pulses fed back becomes zero.

On the other hand, the proximity switch 10 is turned on when the protruding part of the gear-like metal fitting 9 approaches, and turns off when the protruding part leaves.
By reaching F, a pulse-like signal e proportional to the amount of rotation of the servo motor 3 is generated. A pulse signal l obtained by shaping the signal e and a frequency-divided pulse signal obtained by dividing the frequency of the feed amount command pulse b are input to the safety addition/subtraction controller 8. The number of pulses in the frequency-divided pulse signal is as follows. It is subtracted one after another by the pulse of the pulse signal 1, and during normal operation, the count number of the safety addition/subtraction counter 8 becomes zero when the operation is completed. Note that a reset signal j is also input to this safety addition/subtraction counter 8.

Therefore, when the shaft encoder 5 or the servo amplifier 2 breaks down, the pulse count number of the safety addition/subtraction counter 8 becomes abnormally large, and at this time, an alarm signal k is generated that causes a corresponding action such as cutting off the main power circuit of the servo amplifier to be performed. Output. This will be explained in detail in each case. If the shaft encoder 5 fails and the feedback pulse signal g is not input to the addition/subtraction counting circuit 1, the number of pulse counts in the addition/subtraction counting circuit 1 will not decrease, so the servo motor 3 will continue to rotate without stopping. Therefore, the feed detection pulse signal 1 is continuously input to the safety addition/subtraction counter 8, and the pulse count number of the counter 8 becomes abnormally large in the negative range, and the W report signal k is output. Furthermore, when the servo motor 3 does not rotate due to a failure, the feed detection pulse signal 1 is not input to the safety addition/subtraction counter 8, but the branch pulse signals are input one after another, so the pulse count number of the counter 8 is in the positive range. It becomes abnormally large and an alarm signal k is output.

However, the above-mentioned conventional technology has the following drawbacks.

(a) Since the gear-shaped metal fitting 9 and the proximity switch 10 are required, the number of parts is large, resulting in additional costs and assembly man-hours.

(bl) Since the adjustment of the gear-shaped metal fitting 9 and the proximity switch 10 is delicate, if the adjustment is not correct, a pulse miss or chattering will occur, making it impossible to accurately detect a failure.

FC) Since there is a limit to the response speed of the proximity switch 10, the feed speed by the servo motor 3 is limited.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a digital feeding device that can reduce the number of parts and accurately detect the occurrence of a failure. The present invention that achieves this objective is as follows:
The gist is that a type of servo motor that generates a rotational position signal corresponding to the rotational position of the rotor is used, and a failure is detected using the rotational position signal of this servomotor and a frequency-divided pulse signal.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 shows an embodiment of the invention. As shown in the figure, a polarity designation signal a, a feed amount command pulse signal and a feedback pulse signal g are input to the addition/subtraction counting circuit 1, and the signal output C of this addition/subtraction counting circuit 1 is transmitted to the servo amplifier 2. , the output voltage d of this servo amplifier 2
The brushless servo motor 11 is rotated. This brushless servo motor 11 uses a permanent magnet as a rotor, and operates a semiconductor switching element (such as a thyristor) based on a rotor rotational position signal that detects the rotational position of the rotor, and supplies a rectified armature current to the stator windings. Rotates by flowing water. A speed generator 4 and a shaft encoder 5 are connected to the shaft on the anti-load side of the brushless servo motor 11, and the generated voltage output f of the speed generator 4 is input to the servo amplifier 2, and the feedback pulse of the shaft encoder 5 is The signal g is input to the addition/subtraction counting circuit 1. Further, the rotor rotational position signal en generated by the brushless servo motor 11 is input not only to the servo amplifier 2 but also to the signal processing circuit 7n. The signal processing circuit 711 performs signal processing on the rotor rotational position signal en, and generates a transmission detection pulse signal 1n corresponding to the rotational uncertainty of the brushless servo motor 11. This feed detection pulse signal in is input to the subtraction terminal of the safety addition/subtraction counter 8. On the other hand, the feed amount command pulse b is also input to the frequency dividing circuit 6, where it is frequency-divided to become a frequency-divided pulse signal, and this frequency-divided pulse signal is input to the addition terminal of the safety addition/subtraction counter 8. . A reset signal j is also input to the safety addition/subtraction counter 8 to set the pulse count number of the counter to zero. The safety addition/subtraction counter 8 outputs an alarm signal k when the pulse count exceeds a specific fixed range.

The operation of such a digital transmission device will be explained below. A feed amount command pulse signal having information on the feed rate and speed is input to the addition/subtraction count circuit 1. The addition/subtraction counting circuit 1 successively subtracts the pulse count obtained by integrating the feed amount command pulse, x, and the number of pulses of the signal S, each time a pulse of the feedback pulse signal g is input, and calculates the remaining pulse count. generates a signal output C proportional to the number. The servo amplifier 2 amplifies the power of the signal output C to obtain an output voltage d, and applies this output voltage d to the brushless servo motor 11.
In addition, the brushless servo motor 11 is driven. Furthermore, the servo amplifier 2 receives the generated voltage output f of the speed generator 4 and controls the brushless servo motor 11 to rotate at the speed commanded by the signal C. Brushless servo motor 1
1 rotates, the feedback pulse signal g of the shaft encoder 5 is input to the subtraction terminal of the addition/subtraction counting circuit 1, the pulse count number decreases, and the signal output C gradually decreases and finally becomes zero. This happens when the number of pulses of the feedback pulse signal g becomes equal to the number of pulses of the feed amount command pulse signal. At this time, the output 'it pressure d of the servo amplifier 2 also becomes zero, and the brushless The servo motor 11 stops and the feeding operation is completed. The polarity designation signal a determines the polarity of the output signal C generated by the addition/subtraction counting circuit 1, thereby transmitting the commanded direction to the brushless servo motor 11 and determining the rotation direction of the brushless servo motor. Further, the number of feed detection pulses M in and the number of frequency-divided pulses h are equal to each other for a unit feed amount.

Next, the operation of this digital feeder in the event of a failure will be explained.

The brushless servo motor 11 outputs a rotor rotational position signal en used to control the polarity and phase of the output voltage d of the servo amplifier 2, and this rotor rotational position signal en is shown in FIGS. 3 As shown in Figure (C)
This consists of three signals en-1, en-2, and en-3. The rotor rotational position signal en is output from the signal processing circuit 7n.
The signal is pulsed and converted into a feed detection pulse signal i1 as shown in FIG. 3(d). Note that a specific example of the signal processing circuit 7n will be described later. The safety addition/subtraction counter 8 receives a feed detection pulse signal in which is proportional to the rotation amount of the brushless servo motor 110, and a feed amount command pulse signal so that the number of pulses for a unit feed amount is the same as the number of pulses of the feed detection pulse signal 1n. A frequency-divided pulse signal is input. Therefore, during normal operation, the pulse count number of the safety addition/subtraction counter 8 is below a certain value determined by the characteristics of the feeding device, and the pulse count number becomes zero when feeding is completed.

However, in the event of a failure, the pulse count number of the safety addition/subtraction counter 8 becomes abnormally large. To explain using a specific example, if the shaft encoder 5 fails and the feedback pulse signal g is not output, and the brushless servo motor 11 does not stop because of this, the feed detection pulse signal in continues to be output one after another. As a result, the pulse count number of the safety addition/subtraction counter 8 becomes abnormally large in the negative range. In addition, if the addition/subtraction count circuit 1, servo amplifier 2, or brushless servo motor 1 is broken and the brushless servo motor 11 is not driven, the feed amount detection pulse signal in is not input, but the frequency division pulse signal Since the pulses are inputted one after another for each feed command, the pulse count number of the safety addition/subtraction counter 8 becomes abnormally large in the positive range. As described above, when the difference between the number of pulses of the feed detection pulse signal 1n and the number of pulses of the frequency-divided pulse signal exceeds a certain number and the number of pulse counts becomes abnormally large, the safety addition/subtraction counter 8 outputs the alarm signal k. When the alarm signal k is output, the main power of the servo amplifier 2 is cut off,
Other accident response actions are activated.

A specific example of the signal processing circuit 7n is shown in FIG.

In FIG. 4, 71 is a buffer amplifier, 72 is an inverter, 73 is a differential circuit, 74 is an amplifier with hysteresis, 75 is an AND gate, 76 is an OR gate, and D is a diode. This signal processing circuit 7n differentiates the rotor rotational position signal en and amplifies it with a hysteresis amplifier 74 to form a feed detection pulse signal in having a predetermined pulse width.

As specifically explained above in conjunction with the embodiments, according to the present invention, a servo motor of the type that generates a rotational position signal corresponding to the rotational position of the rotor is used, and the rotational position signal of this servomotor is used to detect failures. Detection is made so that it is not necessary to use the gear-like metal fittings and proximity switch that were conventionally used. Therefore, it is possible to eliminate all of the drawbacks that have occurred with the use of gear-shaped metal fittings and proximity switches, such as an increase in the number of parts and poor precision. In other words, according to the present invention, it is possible to reduce the number of parts, respond even when the motor feed speed is high, and accurately detect failures.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional digital sending device, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a waveform diagram showing the output waveform of the signal processing circuit, and Fig. 4 is a signal FIG. 2 is a circuit diagram showing a specific example of a processing circuit. In the drawing, 1 is an addition/subtraction counting circuit, 2-digit servo amplifier, 3 is a servo motor, 4-digit speed generator, 5 is a shaft encoder, 6 is a frequency dividing circuit, 7.7n is a signal processing circuit, 8 is a safety addition/subtraction counter, 9 is a gear-like metal fitting, 10 is a proximity switch, 1 is a brushless servo motor, b is a feed amount command pulse signal, a feed back feedback pulse signal, 11 is a frequency division pulse signal, i and in are feed detection pulse signals, k is a Alarm signal, en is rotor rotational position fIf, signal.

Claims (1)

[Claims] A servo motor of the type that generates a rotational position signal corresponding to the rotational position of the rotor, a servo amplifier that drives this servo motor, and a pulse input of a feed amount command pulse signal that commands the feed amount to count up and calculate the actual value. an addition/subtraction count circuit that counts down in response to a pulse input of a feedback pulse signal corresponding to the feed amount and operates the servo amplifier from when a feed amount command pulse signal is input until the pulse count reaches zero;
A feed detection pulse signal obtained by processing the rotor rotational position signal into pulses, and a frequency-divided pulse obtained by dividing the feed amount command pulse signal so that the number of pulses for a unit feed amount is the same as the number of pulses of the feed detection pulse signal. A digital feeder comprising: a safety addition/subtraction counter which outputs an alarm signal when a signal is input and the difference between the number of pulses of the feed detection pulse signal and the number of pulses of the frequency-divided pulse signal exceeds a certain number. .