JPS61109648A - Position detector for numeric control machine tool - Google Patents

Abstract

PURPOSE:To improve the reliability and safety by constructing such that the projection and notch of first and second disc rotatable integrally with the movable section rotary shaft are detected simultaneously thus to operate/output a position detecting signal. CONSTITUTION:Discs 2, 3 will rotate together with a spindle 1 to detect a projection 2a and a notch 3a through proximity switches 4, 5. In other word, upon arriving of the projection 2a or notch 3a immediately above the spindle 1, detection signals 1, 0 are fed through an amplifier 6a and an inverter 6b to AND gate 6c. AND gate 6c will obtained the theoretical sum from said signals to produce position signal D3 as 1. With such arrangement, the position is detected through the other disc upon malfunction of one disc, resulting in improvement of the reliability and safety.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detector for a numerically controlled machine tool for supplying position information of each part of the machine as an electrical signal to a control device of a shaft feed drive system.

(Conventional technology) Numerical control (hereinafter abbreviated as NC) machine tool control is
In order to control the shaft feed drive system, this can be achieved appropriately by installing a spindle rotation function, tool selection function, index table, coolant device, and other mechanisms that operate in response to commands from the NC device. . Control signals for these machines can only be input to the NC device when the detectors in each part are operating normally, and the performance of these detectors must be ensured in order to operate the NC machine tool safely. It won't happen.

However, in order to check the position of the magazine, spindle orientation, index table, etc. of NC machine tools, only non-contact position detectors such as proximity switches and photoelectric switches are usually used. Even when an electrical signal is correctly output from the NC device, if the wiring is disconnected or a power failure occurs, for example, an incorrect signal will be supplied to the NC device.

(Problem to be Solved by the Invention) In other words, in the case of a conventional position detector, not only when it fails, but even when it is functioning normally, when there is a disconnection or power failure, an incorrect position signal is sent to the NC. Non-contact type detectors have the problem of being prone to bending, as increasing the protrusion of the detection disc may cause bending, especially on a spindle that rotates at high speed and is supplied to the device. ing. There is no cheap and reliable means to avoid this, and therefore, in order to prevent the destruction of expensive NC machine tools or to ensure safety, it is necessary to prevent incorrect commands from being issued from the NC device. It is only at this point that the NC machine tool itself is stopped, for example, or a signal system is provided to prevent the NC machine tool from running out of control using other limit switches or the like.

The present invention improves the reliability of the position detector itself, and
The object of the present invention is to provide a position detector for an NC machine tool that allows the machine tool to be operated more safely than ever before.

(Means for Solving the Problems) The position detector of the present invention has a first position detector that rotates together with a rotating shaft of a movable part of a numerically controlled machine tool. A second disc and a protrusion formed on the peripheral edge of the first disc.

A notch formed on the peripheral edge of the second disk, and these $1.
It is comprised of a pair of detectors that simultaneously detect the protrusion and the notch near the periphery of the second disk, and a logic circuit that receives the detection signals of these detectors and obtains a position detection signal.

(Function) Therefore, position detection is possible even when either one of the detection signals of a pair of detectors becomes abnormal, and when both detection signals cannot be obtained, abnormality detection is performed by the logic circuit. This prevents the position detection signal from being output.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of a position detector used, for example, in the main spindle orientation of a machining center. are installed so that they rotate together.

Reference numeral 4 denotes a proximity switch such as a non-contact position detector, such as a magnetic sensor. The device is configured to output a signal (“i”).

Further, a proximity switch 5 similar to 4 is located vertically above the main axis l near the periphery of the disk 3, and outputs a negative pulse signal ("O") by detecting the notch 3a. It is composed of

The proximity switches 4.5 are both connected to the logic circuit 6 so as to input their detected pulses.

This logic circuit 6 is connected to the positive pulse signal of the proximity switch 4 (
Amplification@6m that directly amplifies the signal “1”), and an inverter 6 that inverts the negative pulse signal (60”) of the proximity switch 5.
b and amplification! 6 & an AND circuit 6c which makes the output of the inverter 6b two-man power.

FIG. 2(a) shows operating waveforms of each part of the logic circuit 6.

When the main shaft 1 is rotating, at a certain time T, when the protrusion 2& and the notch 3a of the disk 2.3 come vertically above the main shaft 1,
The proximity switches 4.5 are simultaneously l” and “0” respectively.
The AND circuit 6C outputs the detection signal of Dl and 5.
The position detection signal D8 becomes l'' by taking the logic circuit sum . It is done.

In FIG. 2(b), the proximity switch 4 has failed.

The operating waveform is shown when the detection signal RI reaches the "1" level due to imperial succession.

Similarly to the figure (a), when the detection signal of the proximity switch 5 becomes '0' at time T, the output D5 of the AND circuit 6c becomes '1'.
'', and the position of the main shaft l can be detected.

Furthermore, FIG. 2(C) shows the operating waveform when the proximity switch 5 fails and its detection signal D2 continues to be at the "0" level. When the detection signal D1 of the switch 4 becomes "1", the AND circuit 6
The output D5 of c becomes "1", and the position of the spindle can be detected.

FIG. 2(d) shows that if, for example, any signal line of the proximity switch 4.5 is disconnected and the detection signals D1 and D2 become 1'' by mistake, the two-man power of the AND circuit 6C becomes D1w.
m″l″, l) 2 m″O″, indicating that no erroneous detection signal is generated.

In this way, a pair of proximity switches 4.5 each have a first
．． Since the protrusion 2a and notch 3a of the second circle @2 and 3 are detected to generate the 1 position detection signal, a position detection signal can be obtained even if one of the detection signals becomes abnormal. It's possible! Abnormality detection is performed when a detection signal on the '-v4 side cannot be obtained. t, the proximity switch 4.5 or the digit 1 of the circle gi2.3 is shifted, and the detection signal D
Even when the pulses 1- and D2 do not occur simultaneously, the 1-position detection signal Dg is no longer output.

(Effects of the Invention) As detailed above, the present invention uses a disk with a protrusion and a disk with a notch at the same time to obtain a position detection signal of a rotating shaft of a movable part such as a main shaft. It is possible to provide position detection St with a simple configuration and high affinity, and it is possible to further enhance the safety of numerically controlled machine tools at low cost and in a simple manner.

[Brief explanation of the drawing]

FIG. 1 is a professional diagram showing the configuration of an embodiment of the present invention.
FIGS. 2(a) to 2(d) are waveform diagrams illustrating the operation of the same embodiment. l... Main axis, 2.3... 1st. Second disk, 4.5
...'IL connection switch, 6...logic circuit.

Claims (1)

[Claims] The first part rotates together with the rotating shaft of the movable part of the numerically controlled machine tool.
, a second disc, a protrusion formed on the periphery of the first disc, a notch formed on the periphery of the second disc, and the above-mentioned at the same time near the periphery of the first and second discs, respectively. 1. A position detector for a numerically controlled machine tool, comprising a pair of detectors for detecting a protrusion and a notch, and a logic circuit into which detection signals from these detectors are input to obtain a position detection signal.