JPS5841983B2 - Contact detection device for tool and workpiece - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting contact between a conductive tool and a workpiece that are in relative motion, and its purpose is to
The goal is to detect the contact of an object with high precision and stability.

In a conventional contact detection device, a coil connected to an AC power source is attached around a tool, and when the tool and workpiece come into contact, an induced current flow path is formed and the impedance of the coil changes, causing the current flowing through the coil and A change occurs in the voltage, and the electrical signal of this current change or voltage change is compared with a predetermined setting signal to detect the presence or absence of contact.

A specific example of this will be explained with reference to FIGS. 1 and 2 a"-c.

FIG. 1 shows a processing machine 10 equipped with a tool 1 and a workpiece 2 that perform relative motion, and FIG. 2a shows a circuit configuration for contact detection.

An AC power source 14 is connected to a coil 12 wound around an iron core 11 via a resistor 13, and an induced current flow path 15 is formed by contact between the tool 1 and the workpiece 2.

16 is the overall resistance of the induced current flow path 15, and 17 is a detection section connected between the coil 12 and the AC power source 14.

FIG. 2 is a block diagram showing details of the detection unit 17,
Figure 2C shows the signal status of each part, and in the figure, 2
0 is a full-wave rectifier to which the voltage A across the resistor 13 is input and rectifies this voltage A as shown in FIG. Ru.

Reference numeral 22 denotes a level comparator, which compares the signal C with the setting signal 2 from the level setter 23, and generates a contact detection signal when the tool 1 and the workpiece 2 come into contact and the signal C exceeds the setting signal 2. It is designed to output e.

However, there has been a drawback that the voltage A for detecting contact fluctuates greatly due to fluctuations in power supply voltage, temperature drift, etc., making it difficult to set the level of the setting signal 2, and making it impossible to stably and accurately detect contact.

In addition, in the induction coil type contact detection device as described above, when the tool 1 and the workpiece 2 come into contact with each other, the induced current flow path 15
When a current flows through the coil 12, not only does the current flowing through the coil 12 increase, but the phase of the current waveform also changes.If this phase change is also detected, contact detection can be performed with higher sensitivity. However, it was not possible to detect any phase change in this current waveform, and highly sensitive contact detection was not possible.

In order to eliminate such conventional drawbacks, the present invention creates a reference waveform from an AC voltage output from an AC power source, which has the same effective value and phase as the detected waveform when the tool and workpiece do not contact each other, and The present invention is characterized in that contact between the two objects is detected based on a difference between the detected waveform and either the high value or the phase of the ζ value.

Examples of the present invention will be described below.

FIG. 1 shows a tool 1 attached to the spindle of the spindle head 3.
In contrast, an example of a processing machine is shown in which a table 5 on which a workpiece 2 is placed moves back and forth on a bed 4, and a coil 12 is wound around an iron core 11 and attached to the end face of the spindle head 3.

This coil 12 generates an alternating current (when the iron is excited, it generates an annular closed magnetic flux that passes through the center of the coil winding, and since this magnetic flux surrounds the tool 1, it is directed in the axial direction of the tool 1. induces an induced current.

When the tool 1 and the workpiece 2 come into contact, a closed-loop induced current flow path 15 is formed in the processing machine body 10 through the tool 1 made of conductive material, the workpiece 2, the spindle head 3, the bed 4, the table 5, etc. Further, unless the tool 1 and the workpiece 2 are in contact with each other, the closed-loop induced current flow path 15 is not formed.

Therefore, as the induced current flow path 15 is opened and closed depending on the presence or absence of contact between the tool 1 and the workpiece 2, the coil 12
impedance changes.

Due to this change in impedance, the current flowing through the coil 12 changes, and electrical signals such as voltage change accordingly.

A circuit for detecting a change in the electrical signal caused by the contact between the tool and the workpiece is shown in FIGS. 3a and 3b.
Figure 3 a, b? Components having the same configuration and function as those in FIGS. 2a and 2b are given the same reference numerals.

In FIG. 3a, 30 is a first circuit for obtaining a reference voltage waveform, in which a resistor 32 is connected in series with a variable resistor 31, and this series circuit is connected in parallel with an AC power source 14, and the tool 1 and workpiece 2 are When the variable resistor 31 is in a non-contact state, the variable resistor 31 is adjusted to make the effective value of the voltage waveform VA between one end of the variable resistor 31 and the voltage outlet equal to the effective value of the voltage waveform VB across the resistor 13. That's what I do.

Note that the variable resistor 31 may be replaced with a coil having the same specifications as the coil 12.

In this case, the phase of the AC waveform output from the first circuit 30 almost matches the phase of the voltage waveform generated across the current detection resistor 13 when the tool 1 and the workpiece 2 are not in contact. Therefore, the second circuit 34 described later becomes unnecessary.

FIG. 3 is a block diagram of the detection section and the second circuit for obtaining the reference voltage, and FIG. 3C shows the signal state thereof.

33 is a noise filter, 34 is a second filter for obtaining a reference voltage waveform.
A variable resistor 35 is connected to this circuit 34, and when the tool 1 and the workpiece 2 are not in contact with each other, the variable resistor 3
5 is adjusted to delay the phase of the voltage waveform VA with respect to the voltage waveform B, which has a phase lag because it includes the coil 12, so that their phases match.

The voltage waveform VB and the voltage waveform VA1 after passing through the second circuit 34 for slow phase are input to a comparator 36.
The output VB-VA is input to the peak detection circuit 3γ.

This peak detection circuit 37 detects and holds the highest value of the AC voltage waveform.

22 is a level comparator, which compares the input X from the peak detection circuit 31 with the setting signal 2 from the level setter 23, and when the tool 1 and the workpiece 2 come into contact, the output of the peak detection circuit 37 is A contact detection signal vZ is output when vX exceeds a set signal 2.

Next, the operation of the above embodiment will be explained.

The AC power supply 14 generates a detection voltage waveform VB across the resistor 13c.

When the tool 1 and the workpiece 2 are not in contact, the variable resistor 31 is adjusted to obtain a voltage waveform V equal to the effective value of the detected voltage waveform VB.
A and the variable resistor 35 are adjusted to form a voltage waveform A1 having the same phase as the detected voltage waveform VB.

In this way, a reference voltage waveform vA1 having the same voltage (effective value) and phase as the detected voltage waveform VB is formed and prepared.

When tool 1 and workpiece 2 do not contact, VB and VAl
have the same voltage waveform and the output from the comparator 36 becomes O■ and no output is produced.

When the tool 1 and the workpiece 2 come into contact, the resistance between them becomes small, and a large induced current flows in the induced current flow path 15. This causes the current flowing in the coil 12 to increase, and at the same time, the current that increases at this time increases. Since is only the effective current, the phase of the current also changes.

Therefore, the detected voltage waveform VB increases rapidly and (
The phase also changes, and as a result, a difference occurs in both the effective value and the phase between the detected voltage waveform VB and the reference voltage waveform VA1, and an output VB-VA1 corresponding to the difference is output from the comparator 36. Ru.

The output from the comparator 36 is output from the peak detection circuit 3.
70 is input, and the level comparator 22G determines that the output VX from the circuit 37 exceeds the setting signal 2, and the contact signal 2Z is output.

As described above, in the present invention, between the contact detection coil and the AC power supply that excites it (a detection circuit that detects the alternating current flowing through the contact detection coil and outputs an AC waveform in accordance with the alternating current flowing through the contact detection coil) At the same time, level adjustment and phase shift are performed on the AC voltage output from the AC power supply in parallel with the AC power supply, so that the same effective AC waveform as the AC waveform output from the detection circuit when the tool is not in contact with the workpiece is obtained. A reference waveform generation circuit that outputs a reference waveform with the same value and phase is connected, and the reference waveform output from this reference waveform generation circuit and the detected waveform are compared to determine the difference in effective value or phase between the two. Since the configuration is equipped with a discrimination circuit that determines when a Since it is also possible to detect phase changes in the excitation current that occur in the current, it has the advantage of greatly improving detection sensitivity compared to systems that detect only level changes.

Further, in the present invention, since no short-circuit current flows on the processing machine when the tool does not contact the workpiece, there is an advantage that power consumption can be reduced and there is no risk of adversely affecting the guide surface.

[Brief explanation of drawings]

Fig. 1 shows a processing machine that performs contact detection, Fig. 2 shows a conventional example, in which a shows the circuit configuration of contact detection, b shows a block diagram of the detection section, and C shows the signal state. FIG. 3 shows an embodiment of the present invention, in which a shows the circuit configuration for contact detection;
b is a block diagram of the detection unit, and C is a diagram showing signal states. 1...Tool, 2...Work, 10...
... Processing machine, 12 ... Coil, 14 ...
... AC power supply, 22 ... Level comparator, 30
...First circuit for obtaining a reference waveform, 34...
・Second circuit for obtaining the reference waveform, 36... comparator,
VAl...Reference voltage waveform, VB...Detection voltage waveform.

Claims (1)

[Scope of Claims] 1. A processing machine is provided with a tool and a workpiece that are relatively close to each other or separated from each other, and an AC power source is connected to a coil that is provided close to the tool and surrounds the spindle axis. An induced current is caused to flow through the processing machine when a tool and a workpiece come into contact, and an alternating current flowing through the coil is detected between the coil and an alternating current power source, and a detected waveform corresponding to this alternating current is output. A reference waveform generation unit includes a detection circuit that performs level adjustment and phase shift on the output waveform of the AC power source to generate a reference waveform having the same effective value and phase as the detected waveform when the tool and workpiece are not in contact. A circuit is connected to the AC power source in parallel with a series circuit formed by the detection circuit and the coil, and the outputs of the detection circuit and the reference waveform generation circuit are compared to determine whether the detected waveform and the reference waveform are the same. A contact detection device for a tool and a workpiece, characterized in that a comparison circuit is provided for determining contact between the tool and the workpiece based on a difference in effective value or phase between the two. 2. The reference waveform generation circuit includes a voltage dividing circuit including a pair of resistors connected in series connected in parallel to a series circuit formed by the detection circuit and the coil with respect to the AC power source, and a voltage dividing circuit including a pair of resistors connected in series. 2. The tool-work contact detection device according to claim 1, comprising a phase shift circuit that shifts the phase of an alternating current signal output from the circuit. 3. The reference waveform generation circuit is characterized in that it is constituted by a series circuit formed by the detection circuit and the coil with respect to the AC power source, and a series circuit comprising a resistor and a coil connected in parallel. Claim 1
Contact detection device for tool and workpiece as described in Section 2.