JPH0631577A - Tool slide device - Google Patents

Abstract

PURPOSE:To prevent the contact of a sensor target with a displacement sensor and the strain deformation of a diaphragm by suppressing the large inclination of the sensor target for detecting the position of a tool when a large load is applied on the cutting edge of a tool, as for a tool feeding device consisting of a voice coil type linear motor and a piezoelectric actuator. CONSTITUTION:A tool 20 is held through a diaphragm 18 at the top edge of a ram 16 which is advance/retreat-driven in the axis line direction by a linear motor, and a piezoelectric actuator 30 which advances and retreats the tool 20 is built in at the top edge part of the ram 16, and a sensor target 22a is installed integrally with the diaphragm 18, and two displacement sensors 22a and 23b for detecting the inclination quantity of the sensor target 22a are arranged at two positions nipping the center point on the too edge surface of the ram 16. The difference of the output signals of two displacement sensors is compared by an upper limit comparator 42 or a lower limit comparator 43, and when the difference exceeds a set value, the linear motor 10 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool feeding device for a machine tool for creating a work in a non-round shape.

[0002]

2. Description of the Related Art A voice coil type linear motor (VCM) having an advancing / retreating drive member for advancing / retreating in an axial direction is used as a tool feeding device of a machine tool for creating a workpiece in a non-round shape.
A ram connected to the advancing / retreating drive member by the same axis, a tool held at the tip of the ram via a diaphragm, and a tool built in at the tip of the ram to move the tool forward / backward through the diaphragm. Piezoelectric actuator (PZ
T), a sensor target which is concentric with the tool and is provided integrally with the diaphragm, and is arranged at two positions facing the sensor target on the tip end surface of the ram and sandwiching the center point of the sensor target. A tool feeding device including two displacement sensors that detect the tool advancing / retreating position of a sensor target is known.

The above-mentioned tool feeding device moves the ram and the tool forward and backward respectively according to the signals input to the linear motor and the piezoelectric actuator based on the non-roundness profile data and the position of the tool forward and backward from the displacement sensor. ,
The operations of these two are combined to control the tip position of the tool in the radial direction of the tool in accordance with the non-roundness profile data to create a non-roundness shape.

[0004]

SUMMARY OF THE INVENTION In the above tool feeding device, when cutting is performed in a state where the depth of the tool is cut into the workpiece or the rotation of the workpiece swings, the cutting edge causes the cutting edge of the tool to move. A large load may be applied, the sensor target may be greatly tilted, the sensor target may hit the displacement sensor, and the diaphragm may be distorted.

An object of the present invention is to provide a tool feeding device which solves the above-mentioned conventional problems by determining that a large load is applied to a tool when the inclination of the sensor target exceeds a certain angle and stopping the drive of the linear motor. Is to provide.

[0006]

SUMMARY OF THE INVENTION A feature of the present invention that achieves the above object is to provide a ram that is axially moved forward and backward by a linear motor, and a tool that is held at the tip of the ram via a diaphragm. A piezoelectric actuator built in the tip of the ram for moving the tool forward and backward, a sensor target concentric with the tool and integrally provided with the diaphragm, a tip surface of the ram facing the sensor target, and Two displacement sensors arranged at two positions sandwiching the center point of the sensor target to detect the amount of inclination of the sensor target, and an upper limit setting value or a lower limit setting value in which the difference between the output signals of the two displacement sensors is preset. The difference between the output signals of the upper limit comparator or the lower limit comparator to be compared with the output signals of the two displacement sensors compared by the upper limit comparator or the lower limit comparator is the upper limit or the lower limit comparator. In which the linear motor or the piezoelectric actuator and a numerical control device for driving stop when it exceeds the limit set value.

[0007]

With the above construction, the difference between the output signals of the two displacement sensors for feedback of the piezoelectric actuator is obtained, and when the difference exceeds the preset upper or lower limit set value, the linear motor is operated by the command of the numerical controller. Drive stop control is performed to free the linear motor so that the cutting resistance causes the tool to escape from the workpiece, and a large tilting motion of the sensor target is suppressed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 10 is a voice coil type linear motor (VCM). The linear motor 10 includes a center pole 11 in a motor housing and a center pole 1
A magnet 12 is provided with an advancing / retreating drive member 13 that is loosely fitted to the outer peripheral surface of No. 1 so as to be advancing / retreating in the axial direction. The advancing / retreating drive member 13 is a coil assembly having a coil 14 on the outer peripheral surface thereof, and the magnet 12 is fixedly installed in the motor housing so as to face the coil 14.

Reference numeral 15 is a guide body, which is installed in front of the linear motor 10. A ram 16 having an angular axis is guided to the guide body 15 by a hydrostatic bearing 17 so as to be movable back and forth on the same axis as the forward / backward drive member 13 of the linear motor 10, and the rear end thereof is the linear motor 10.
Is connected to the advancing / retreating drive member 13.

As shown in FIG. 2, a diaphragm 18 is fixedly mounted on the tip of the ram 16 via a spacer 21, and a tool 20 is held on the diaphragm 18 via a tool holder 19. .

Further, a piezoelectric actuator 30 (PZT) is built in the tip of the ram 16. Between the piezoelectric actuator 30 and the diaphragm 18, an actuating member 22 for driving the cutting tool 20 to move forward and backward through the diaphragm 18 by the piezoelectric actuator 30 is interposed.

A flange-shaped sensor target 22a is formed on the operating member 22, and the operating member 22 is connected to the diaphragm 1 via the sensor target 22a.
8 is integrally attached to the piezoelectric actuator 30 and is always in contact with the piezoelectric actuator 30 by the urging force of the diaphragm 18.
The force pressing the actuating member 22 against the piezoelectric actuator 30 can be freely changed by changing the spacer 21.

The ram 16 and the piezoelectric actuator 3 described above
0 and the cutting tool 20 are all arranged on the same axis 0 as the advancing / retreating drive member 13.

On the tip surface of the ram 16, two displacement sensors 23 are arranged at the center point of the sensor target 22a, that is, in two equal positions across the axis 0 of the ram 16.
a and 2b (gap sensors) are provided and face the surface of the sensor target 22a formed on the actuating member 22.

Reference numeral 24 denotes a forward / backward movement amount sensor of the ram 16, which has a gauge 25 fixedly mounted on the ram 16 side.
The reading head 26 of the gauge 25 is fixed to the 5 side.

The linear motor 10 is connected to a power source 47 via a relay circuit 48 and a VCM drive circuit 49. Further, the VCM drive circuit 49 is configured to operate the ram 16
The forward / backward movement amount sensor 24 is connected via the deviation circuit 50.

Reference numeral 40 is a numerical controller. The numerical control device 40 is connected to the relay circuit 48 and the deviation circuit 50, and is also connected to a spindle drive circuit 51 connected to a spindle 52 that rotates a workpiece W.
0 and the operation of the spindle 52 are controlled.

The numerical controller 40 includes the piezoelectric actuator 30, the deviation circuit 45, and the PZT drive circuit 4.
6 and controls the operation of the piezoelectric actuator 30.

In the deviation circuit 45 of the control system path of the piezoelectric actuator 30, the two displacement sensors 23a and 23a are provided.
A first arithmetic circuit 53 for averaging the respective signals a and b of b to obtain the actual forward / backward position c of the bite 20 is connected.

Further, the two displacement sensors 23a, 2
And a second arithmetic circuit 54 for obtaining the inclination amount d of the sensor target 22a from the difference between the respective signals a and b of 3b.
The second arithmetic circuit 54 includes an upper limit comparator 42 that compares the inclination amount d of the sensor target 22a with an upper limit set value 41.
And a lower limit comparator 43 which compares the lower limit set value 44 with the numerical control device 40.

Since the present invention has the above-described structure, the piezoelectric actuator 30 is actually used based on the non-roundness profile data composed of the high frequency components stored in the command value memory of the piezoelectric actuator 30 in the numerical controller 40.
Is performed, and a trial cutting operation for actually operating the linear motor 10 is performed based on the non-roundness profile data composed of low-frequency components stored in the command value memory of the linear motor 10, and the response value obtained at this time is A command value is created so as to be the same as the target value, and this command value is stored in the command value memory.

Then, the synchronizing signal output based on the rotation of the spindle 52 that rotates the workpiece W outputs a command value based on high-frequency, short-stroke data stored in the command value memory, and the piezoelectric actuator 30. Bite 2 fed back from the displacement sensors 23a, 23b of
The piezoelectric actuator 30 is controlled by outputting a position deviation signal which is a deviation from the signal of the position c of 0 in the forward / backward direction.

A synchronizing signal based on the rotation of the main shaft 52 outputs a command value based on low frequency and large stroke data stored in the command value memory, and is fed back from the forward / backward movement amount sensor 24 of the linear motor 10. The linear deviation motor 10 is controlled by outputting a position deviation signal which is a deviation from the position signal.

The piezoelectric actuator 30 and the linear motor 10 are controlled by their respective command values, and their operations are combined to control the blade edge position of the cutting tool 20 in the radial direction in accordance with the non-round profile data. , Cutting non-round shape.

Therefore, in the present invention, the two displacement sensors 2
The second arithmetic circuit 54 calculates the inclination amount d of the sensor target 22a from the respective signals a and b fed back from 3a and 23b by the difference between the two signals a and b, and the inclination amount d is set to the upper limit by the upper limit comparator 42. The value 41 or the lower limit comparator 43 is compared with the lower limit set value 44.

As a result of comparison by the upper limit comparator 42 or the lower limit comparator 43, when the inclination amount d is equal to or more than the upper limit setting value 41 or less than or equal to the lower limit setting value 44, the inclination amount d of the sensor target 22a exceeds the allowable angle, When it is determined that the large load is applied to 20, the abnormal signal is transmitted to the numerical control device 40.

Based on this, the numerical controller 40 sends a relay off signal to the relay circuit 48 to turn off the power supply to the VCM drive circuit 49 to turn off the servo of the linear motor 10 and put the linear motor 10 into a free state. As a result, the cutting tool causes the cutting tool 20 to escape from the workpiece W, the inclination of the sensor target 22a is returned to the normal posture by the diaphragm 18, and the sensor target 22a is prevented from contacting the displacement sensors 23a and 23b.

The numerical controller 40 also sends a control signal for stopping the drive of the spindle 52 to the spindle drive circuit 51 at the same time as the drive stop control of the linear motor 10 to stop the rotation of the workpiece W.

The above embodiment has been described with respect to the example in which the upper limit comparator 42 and the lower limit comparator 43 are provided, but as another modification, the absolute value of the difference between the signals a and b is calculated by the second arithmetic circuit. If it can be calculated, only the upper limit comparator 42 is provided and the absolute value of the difference between the signals a and b can be compared with the upper limit set value.

Further, in the above-mentioned example, the VCM drive circuit 4
Although the example of turning off the power to 9 has been described, the power to the PZT drive circuit 46 may be turned off to allow the cutting tool 20 to escape from the workpiece W by elastic return of the diaphragm 18.

[0031]

As described above, according to the present invention, a ram that is axially driven forward and backward by a linear motor, a tool held at the tip of the ram via a diaphragm, and a tool built in the tip of the ram. A piezoelectric actuator that moves back and forth, a sensor target that is concentric with the tool and that is integrally provided with the diaphragm, and a tip end surface of the ram that faces the sensor target, and is located at two positions sandwiching the center point of the sensor target. Two displacement sensors arranged to detect the amount of inclination of the sensor target, an upper limit comparator or a lower limit comparator for comparing the difference between the output signals of the two displacement sensors with a preset upper limit or lower limit set value, and this upper limit When the difference between the output signals of the two displacement sensors compared by the comparator or the lower limit comparator exceeds the upper limit setting value or the lower limit setting value, the linear mode With a numerical control device that stops driving, when a large load is applied to the cutting edge of the tool due to cutting resistance, this is immediately detected and the servo of the linear motor is dropped or the voltage is supplied to the piezoelectric actuator. Since the tool is stopped and the tool is released from the workpiece, a large inclination of the sensor target is suppressed, and damage to the displacement sensor and strain deformation of the diaphragm can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view of the device of the present invention.

FIG. 2 is an enlarged view of an arrow A portion of FIG.

[Explanation of symbols]

 10 linear motor 11 center pole 13 advancing / retreating driving member 15 guide body 16 ram 18 diaphragm 20 bytes 22a sensor target 23a displacement sensor 23b displacement sensor 30 piezoelectric actuator 40 numerical control device 42 upper limit comparator 43 lower limit comparator 46 PZT drive circuit 47 power supply 48 relay Circuit 49 VCM drive circuit 51 Spindle drive circuit 52 Spindle 53 First arithmetic circuit 54 Second arithmetic circuit

Claims (1)

[Claims] 1. A ram that is driven to move back and forth in the axial direction by a linear motor, a tool held at the tip of the ram via a diaphragm, a piezoelectric actuator built in the tip of the ram for moving the tool forward and backward, A sensor target which is concentric with the tool and is provided integrally with the diaphragm, and an inclination amount of the sensor target which is arranged at two positions facing the sensor target on the tip surface of the ram and sandwiching the center point of the sensor target. To detect 2
Two displacement sensors, an upper limit comparator or a lower limit comparator for comparing the difference between the output signals of the two displacement sensors with a preset upper limit or lower limit set value, and two displacements compared by the upper limit comparator or the lower limit comparator A tool feeding device, comprising: a numerical control device that stops driving the linear motor or the piezoelectric actuator when a difference between output signals of the sensors exceeds an upper limit setting value or a lower limit setting value.