JP3221688B2 - NC machine with automatic thermal displacement correction means - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a module having a built-in structure.
More specifically, the present invention relates to an NC machine having means for correcting a displacement amount of a machine tool spindle having thermal expansion due to thermal expansion.

[0002]

2. Description of the Related Art As shown in FIG. 5, in a conventional NC machine having a spindle 1 having a motor 30 of a built-in structure, a rotor 2 of a motor 30 is directly attached to a central portion of the spindle 1, and The stator 7 of the motor 30 is attached to the inside of the case 6 that holds the motor 1. A tool 4 is attached to one end of the spindle 1 via a chuck 3, and the tool 4 processes a work 19 on a table 18. The entire case 6 of the main shaft 1 can be moved in the thrust direction of the main shaft 1 by driving a ball screw 9 screwed to a ball screw nut 8 attached to the lower surface of the case 6 by a servomotor 10. The servomotor 10 is numerically controlled through a positioning control means 15 based on a position command from a numerical control device 20. Also, a speed command of the spindle 1 is output from the numerical controller 20 and the spindle 1 is transmitted through the spindle motor control means 12.
Numerical control of the rotation speed of The stator 7 inside the main shaft case 6 has a built-in temperature detecting means 11 for detecting the temperature of the motor 30, and when the temperature exceeds a certain temperature, the protecting means 13 of the motor 30 is activated. Is designed to protect.

[0003]

SUMMARY OF THE INVENTION A module having a built-in structure
In the main shaft 1 having the motor 30, the main shaft 1 and the motor 30 are integrated and compact. However, since the rotor 2 and the stator 7 of the motor 30 are arranged around the main shaft 1, the main shaft 1 has Heat is transmitted to the main shaft 1 and the main shaft 1 thermally expands. As shown in FIG. 5, when the main shaft 1 thermally expands in the thrust direction as indicated by the broken line, the movement amount actually required is Z 'with respect to the movement amount Z set in advance when the normal motor 30 is at room temperature. And an error corresponding to ZZ 'occurs, thereby deteriorating the processing accuracy.

As described above, the heat generated by the stator 7 and the rotor 2 is transmitted to the main shaft 1 of the main shaft 1 of the built-in motor. There is a problem to make it.

[0005] The present invention takes into account such problems of the conventional NC machine tool having a main shaft of a built-in motor, and functions easily without adding a special device. In addition, automatic thermal displacement is automatically performed.
It is intended to provide a C machine tool.

[0006]

SUMMARY OF THE INVENTION The present invention provides a built-in structure.
The rotational speed of a spindle having a built-in motor and the position of the spindle
Main control means for instructing the rotation, based on the rotation speed command
Spindle motor control means for controlling the speed of the motor;
Positioning that controls the position of the spindle based on the position command
Control means and temperature detecting means for detecting the temperature of the motor
And the motor is maintained based on the detected temperature signal.
An NC machine having protection means for protecting
Input the temperature signal detected by the temperature detection means, and
Automatic heat change to correct the position command from the main control means
Position correction means, wherein the automatic thermal displacement correction means
The difference between the temperature detected by the temperature detection means and room temperature is used as the transfer function.
Converting into a temperature difference between the main shaft and the room temperature,
The temperature difference is converted into a relative thermal expansion amount of the main shaft by a conversion function.
Automatic thermal displacement correction means characterized by converting and outputting
It is an NC machine tool.

[0007]

According to the present invention, the automatic thermal displacement compensating means is a motor.
When inputting the temperature of the data and outputting the position correction value, for example, the room temperature was previously input as a parameter, and the difference between the room temperature and the temperature of the spindle was obtained to obtain the position correction value, which was output from the main control means. The corrected position command is added to the position command, and the position of the main shaft is corrected by the positioning control means using the corrected position command as an input.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of an embodiment of an NC machining apparatus with automatic thermal displacement correcting means according to the present invention, as viewed from the front. That is, the rotor 2 of the motor 30 is mounted at the center of the main shaft 1, and the tool 4 is mounted at one end via the chuck 3. The main shaft 1 is mounted on a case 6 via bearings 5 so as to rotate together with the rotor 2, the chuck 3, and the tool 4. The stator 7 of the motor 30 is mounted inside the case 6, and a built-in motor 30 is provided. Is constituted. The case 6 is movable in the thrust direction of the main shaft 1, and a ball screw 9 screwed to a ball screw nut 8 attached to the case 6 is connected to a servo motor 10.
It is driven by. The stator 7 has a built-in temperature detecting means 11 such as a thermistor for detecting the temperature of the stator 7, that is, the temperatures of the rotor 2 and the main shaft 1. The spindle motor control means 12 receives the detected stator temperature, and when the temperature exceeds a certain temperature, protects the motor 30 by, for example, setting the drive voltage to 0 by a built-in protection means 13. . The main control means 14 is a means for sending a speed command to the main spindle motor control means 12 to control the rotation speed of the main spindle 1. The main control means 14 sends the position command to the positioning control means 15 via the position correction value adder 17. The positioning control means 15 responds to a position command from the main control means 14 and
0 based on the position feedback signal of 0
This is a means for controlling the position of the main shaft 1 by 0.

The output signal of the temperature detecting means 11 is also inputted to an automatic thermal displacement correcting means 16 built in the main control means 14. The automatic thermal displacement correcting means 16 calculates a position correction value based on the thermal displacement of the main shaft 1 based on the detected temperature of the stator 7. The position correction value due to the thermal displacement is added to the tool length correction value and input to the adder 17 as a position correction value. The adder 17 adds the position command output from the main control unit 14 and the position correction value input to the adder 17 and outputs a corrected position command to the positioning control unit 15.
Output. The work 19 to be processed is held on a table 18.

FIG. 2 is a block diagram for explaining the calculation contents of the automatic thermal displacement correcting means 16. The room temperature θr is input in advance as a parameter. The stator temperature θs is the stator temperature detected by the temperature detecting means 11 in FIG. The temperature difference Δθ between the room temperature θr and the stator temperature θs input as a parameter is the transfer function G (s) 21
Is converted into a temperature difference Δθ ′ between the spindle 1 and the room temperature θr, and is input to the validity / invalidity determination circuit 22. The validity / invalidity determination circuit 22 determines whether the absolute value of the temperature difference Δθ ′ between the main shaft 1 and the room temperature θr is larger or smaller than a certain value. 2
Send to 4. Further, a temperature difference Δθ ′ between the main shaft 1 and the room temperature θr
Is input to a certain function f (Δθ ′) 23 and converted into a relative thermal expansion amount ΔZ of the main shaft 1. The correction execution control unit 24 determines the value of the relative thermal expansion amount ΔZ of the spindle based on the valid / invalid signal, the value of ΔZ as it is in the case of the valid signal, and 0 as the value in the case of the invalid signal. This is a means for outputting a correction value.

Next, the operation of the present invention will be described.

First, it is assumed that information necessary for processing is input to the main control means 14. At this time, the parameter of the automatic thermal displacement correction means 16 is set to the room temperature θr. Next, it is assumed that the work 19 to be processed is mounted on the table 18 and the processing is started by the NC machine having the automatic thermal displacement correcting means. When the NC machine with automatic thermal displacement correction means starts operating,
The main control means 14 outputs a speed command to the spindle motor control means 12. The spindle motor control means 12 outputs a drive voltage to the stator 7 of the motor 30. Then, the rotor 2 of the motor 30 rotates, and the main shaft 1 integrated with the rotor 2 also rotates. The tool 4 attached to the main shaft 1 via the chuck 3 also rotates. Also, suppose that the temperature of the stator 7 exceeds a certain value for some reason while the motor 30 is operating. At this time, since the stator temperature detected by the temperature detecting means 11 built in the stator 7 is input to the protection means 13, the protection means 13 is controlled by the spindle motor control means 12 based on the detected stator temperature. And outputs a signal to protect the motor. The spindle motor control means 12 protects the motor 30 by, for example, setting the drive voltage output to the motor 30 to zero. Further, the main control means 14 outputs a position command to the positioning control means 15. The positioning control means 15 having received the position command controls the drive voltage of the servomotor 10 based on the position feedback signal of the servomotor 10. When the servo motor 10 is driven and the ball screw 9 rotates, the ball screw nut 8 screwed to the ball screw 9
Moves in the thrust direction of the main shaft 1. Then, since the ball screw nut 8 is attached to the case 6, the main shaft 1 and the tool 4 move similarly. At this time, the distance required for the tool 4 to move to the work 19 is defined as Z.

In this manner, the automatic thermal displacement correcting means N
When operating the C machine tool, the stator 7 of the motor 30
Temperature rises. Then, the temperatures of the rotor 2 and the main shaft 1 approaching the stator 7 also increase, and the main shaft 1 expands as shown by a broken line in FIG. Therefore, the position of the tool 4 attached to one end of the spindle 1 also changes, so that the tool 4
The actual distance required to move to work 19 is Z '
It is.

At this time, the stator temperature θs detected by the temperature detecting means 11 built in the stator 7 of the motor 30
Is input to the automatic thermal displacement correction means 16. Then, the automatic thermal displacement correcting means 16 calculates the detected stator temperature θs
Is calculated from the initially set parameter room temperature θr, and a position correction value based on the calculated thermal displacement is output. A tool length correction value is added to the position correction value due to the thermal displacement to obtain a position correction value, which is input to the adder 17. Adder 1
Numeral 7 corrects the position command by adding the position command output from the main control means 14 and the position correction value. Next, the positioning control means 15 controls the drive voltage of the servomotor 10 based on the corrected position command. Then, the servo motor 10 rotates the ball screw 9, and the ball screw 9 moves the ball screw nut 8. Then, since the ball screw nut 8 is attached to the case 6, the spindle 1 attached to the case 6 and the tool 4 attached to the spindle 1 also move. Thus, tool 4
Moves by the corrected distance Z '.

Next, the operation of the automatic thermal displacement correction means 16 will be described with reference to FIG.
It will be explained by. Automatic thermal displacement correction means 1 as described above
The room temperature θr is input in advance to 6 as a parameter. When the motor 30 operates, the stator temperature .theta.s detected by the temperature detecting means 11 is input to the automatic thermal displacement correcting means 16, and the temperature difference .DELTA..theta. =. Theta.s-.theta.r between the stator temperature .theta.s and the parameter room temperature .theta.r is calculated.

Next, a temperature difference Δ between the temperature of the main shaft and the room temperature θr is passed through a transfer function 21 G (s) with Δθ as an input.
Find θ ′.

Generally, G (s) is (ΔT is a time constant).

This Δθ ′ is input to the validity / invalidity determination circuit 22 to determine whether the absolute value of Δθ ′ is larger or smaller than a certain value. Send to control unit 24. This is because, in a small case, it may be better not to make correction in terms of control delay and the like.

Further, Δθ ′ is converted to a certain function f (Δθ ′) 23
To calculate the relative thermal expansion amount ΔZ of the main shaft. Usually, f (Δθ ′) is represented by ΔZ = f (Δθ ′) = k · Δθ ′ (∵k is a time constant). (ΔZ ≒ Z−Z ′) Next, based on the above-mentioned valid / invalid signal, the correction execution control unit 24 calculates the value of ΔZ as it is in the case of a valid signal and the value of 0 in the case of an invalid signal by thermal displacement. Output as a position correction value.

When the valid / invalid determination circuit 22 outputs a valid signal, the adder 17 adds the tool length to the position command output from the main control means 14 and the position correction value based on the thermal displacement output from the correction execution control unit 24. By adding the position correction value obtained by adding the correction value (see FIG. 1), the error between the movement amount Z at the room temperature θr and the movement amount Z ′ at the stator temperature θs of the spindle 1 is eliminated. The corrected position command that has been corrected
5 is output.

The positioning control means 15 outputs a drive signal to the servomotor 10 based on the corrected position command,
The servomotor 10 corrects the error of the thermal displacement of the moving amount of the tool 4 attached to one end of the main shaft 1 by the case 6 and thus drives the servomotor 10 correctly.

Further, the position correction value may not be added to the tool length correction value but may be added to another correction value, for example, a work coordinate system shift value.

The transfer function G of the automatic thermal displacement correction means 16
(S) and the function f (Δθ ′) for converting the temperature difference Δθ ′ into the relative thermal expansion amount ΔZ of the main shaft may be other than those of the embodiment.

A method is also conceivable in which the valid / invalid determination circuit 22 is eliminated and the position is corrected even in the case of a small temperature difference.

The upper limit value may be determined so that the position correction value does not become extremely large, and if it exceeds the upper limit value, the correction may be performed using the upper limit correction value.

The cooling effect of the cutting oil or the like may be added to the temperature difference Δθ 'as a correction factor. That is, FIG.
Is a part of a block diagram of the automatic thermal displacement correcting means 16 for correcting the effect of the cooling action by cutting oil or the like. The transfer function G1 (s) 25 is the transfer function G (s) 2 of the above embodiment.
Same as 1. A correction function f (n) 26 for the cooling effect of the cutting oil or the like is generated to the temperature difference Δθ ′ which is the output of the transfer function G1 (s) 25, and the correction function f (n) 26 is input to the transfer function G2 (s) 27 and the output Δθ1 is added. Δθ2 is input to the validity / invalidity determination circuit 22.

A temperature detecting means may be provided in the room so that the room temperature can be detected separately, and the room temperature may be detected. At this time, as shown in FIG. 4, a part of the block diagram of the operation of the automatic thermal displacement correcting means 16 is changed, and the detected room temperature θg is calculated by using the transfer function G3 (s) 28 as the temperature of the workpiece or the like and the parameter θr. , And is output as a correction value ΔZ1 in the thrust direction of the main shaft by a certain function f (Δθ2) 29. The output correction value ΔZ1 is added to the spindle expansion amount ΔZ to become ΔZ2, which is input to the correction execution control unit 24.

In order to determine the temperature of the main shaft, the temperature of the main shaft, for example, may be directly detected instead of the temperature of the stator.

The parameters initially input to the automatic thermal displacement correcting means 16 may be other than room temperature, such as the temperature of the main body of the NC machine, or a certain fixed value.

Further, the NC with automatic thermal displacement correcting means of the present invention
The machine tool may be realized by software using a microcomputer in addition to the dedicated hardware circuit having the above functions.

[0032]

As described above, the NC machining apparatus with the automatic thermal displacement correcting means according to the present invention inputs the temperature signal detected by the temperature detecting means and corrects the position command from the main control means based on the input. The automatic thermal displacement correction means prevents the spindle from expanding due to the heat generated by the motor, causing an error in the amount of movement, thereby preventing the machining accuracy from deteriorating. It is not necessary to add a special device. Easy to operate at low cost,
The processing accuracy is stable and the correction is performed automatically, so that it has an advantage that it is effective for unmanned operation.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an embodiment of an NC machining apparatus with automatic thermal displacement correcting means according to the present invention.

FIG. 2 is a block diagram of calculation contents of an automatic thermal displacement correcting means of the embodiment.

FIG. 3 is a block diagram of a part of calculation contents of an automatic thermal displacement correcting means according to another embodiment.

FIG. 4 is a block diagram showing a part of the calculation contents of an automatic thermal displacement correcting means according to another embodiment.

FIG. 5 shows an N type having a main shaft of a conventional built-in motor structure.
It is a schematic sectional drawing of C machine tool.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 spindle 11 temperature detection means 12 spindle motor control means 13 protection means 14 main control means 15 positioning control means 16 automatic thermal displacement correction means 30 motor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-169213 (JP, A) JP-A-63-6604 (JP, A) JP-A-63-126010 (JP, A) JP-A-4- 30941 (JP, A) JP-A-4-8452 (JP, A) JP-A-3-26404 (JP, U) JP-A-60-127848 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23Q 15/00-15/28 G05B 19/18-19/46

Claims (1)

(57) [Claims] 1. A main control means for instructing a rotation speed of a spindle having a motor having a built-in structure and a position of the spindle, and a spindle motor for controlling the speed of the motor based on the rotation speed command. Control means, positioning control means for controlling the position of the spindle based on the position command, temperature detecting means for detecting the temperature of the motor, and protection of the motor based on the detected temperature signal. in NC machine tool and a protective means for said type the detected temperature signals by the temperature detection means, an automatic thermal displacement correcting means for correcting the position command from the main control unit on the basis of it, the automatic thermal displacement The correction means detects the temperature detected by the temperature detection means.
The difference between the measured temperature and room temperature is determined by the transfer function using the main shaft and the
Converts the temperature difference to room temperature, and further converts the temperature difference
The number is converted to the relative thermal expansion of the spindle and output.
An NC machine with automatic thermal displacement correction means.