JP6747352B2 - Numerical control device and control method - Google Patents

Description

The present invention relates to a numerical control device and a control method.

The numerical controller has a servomotor and a feed shaft. The feed shaft is driven by a servo motor. The numerical controller has a feed axis acceleration increasing period and an acceleration decreasing period. The acceleration increasing period is a period during which the acceleration is increased at the start of acceleration of the feed axis. The acceleration reduction period is a period in which the acceleration is reduced at the end of acceleration of the feed axis. The numerical control method described in Patent Document 1 sets the slope of the acceleration change during the acceleration increasing period to be larger than the slope of the acceleration change during the acceleration decreasing period in order to maximize the use of the output torque of the servo motor, and also reduces the acceleration decreasing period. In the above, the acceleration reduction speed of the feed axis is switched from the first acceleration reduction speed which is the constant first inclination to the second acceleration reduction speed which is the constant second inclination which is larger than the first inclination.

Japanese Patent No. 5233592

Since the method described in Patent Document 1 makes maximum use of the output torque of the servo motor, there is a problem that overheating is likely to occur when continuous operation is performed.

An object of the present invention is to provide a numerical control device and a control method capable of suppressing overheat while effectively utilizing the output torque of a servo motor.

The numerical control device according to claim 1, which controls a machine including a servomotor and a drive shaft driven by the servomotor, increases an acceleration period during which acceleration is increased at the start of acceleration of the drive shaft, and a drive shaft of the drive shaft. In a numerical control device having an acceleration decreasing period for decreasing acceleration at the end of acceleration, temperature judgment means for judging whether or not the temperature detected by the temperature detection means for detecting the temperature of the servo motor is less than a first threshold value, and the temperature. When the determination means determines that the temperature is less than the first threshold, the slope of the acceleration change in the acceleration increasing period is set to be larger than the slope of the acceleration in the acceleration decreasing period, and the drive shaft is set in the acceleration decreasing period. Setting a first acceleration decrease speed having a constant first inclination and then switching to a second acceleration decrease speed having a constant second inclination that is larger than the first inclination. One control means and one step of setting the inclination of acceleration change in the acceleration increasing period and the inclination of acceleration change in the acceleration decreasing period to be the same when the temperature determining means determines that the temperature is equal to or higher than the first threshold value. And a second control means for executing acceleration/deceleration control. When the temperature of the servo motor is less than the first threshold value, the first control unit sets the slope of the acceleration change in the acceleration increasing period to be larger than the slope of the acceleration change in the acceleration decreasing period. The numerical control device can effectively utilize the maximum output torque of the servomotor on the low speed side, and can bring the acceleration reduction speed of the drive shaft within the acceleration reduction period close to the maximum output torque characteristic of the servomotor. Therefore, the numerical control device can effectively use the maximum output torque of the servo motor on the high speed side, and the time required for positioning the drive shaft can be shortened. The first control means further executes the two-step acceleration/deceleration control. In the two-step acceleration/deceleration control, the first acceleration decrease speed is set to the second acceleration decrease speed within the acceleration decrease period. The second acceleration decrease speed is greater than the first acceleration decrease speed. Therefore, the numerical control device can surely approximate the acceleration decrease speed to the maximum output torque characteristic of the servo motor, so that the maximum output torque on the medium-high speed rotation side of the servo motor can be effectively used. When the temperature of the servo motor is equal to or higher than the first threshold value, the second control means executes the one-step acceleration/deceleration control in order to suppress overheating of the servo motor. In the one-step acceleration/deceleration control, the slope of the acceleration change in the acceleration increasing period and the slope of the acceleration change in the acceleration decreasing period are set to be the same. Therefore, the numerical control device can set the control characteristics of the drive shaft within the range defined by the maximum output torque of the servo motor, and thus can suppress overheating of the servo motor. The numerical control device can utilize the output torque on the high-speed rotation side when the temperature of the servo motor is low, so that the machining cycle can be shortened. When the temperature of the servo motor is high, the numerical controller can automatically switch from the two-step acceleration/deceleration control to the one-step acceleration/deceleration control to suppress overheating of the servo motor, so that the servo motor can be operated for a long time. The term "acceleration" refers to a positive value when accelerating in the positive direction and a negative value when accelerating in the opposite direction. Can also be shown.

The numerical control device according to claim 2, wherein, when the temperature determination means determines that the temperature is less than the first threshold value, the torque detected by the torque detection means for detecting the torque of the servo motor is less than a second threshold value. And a third control means for executing the two-step acceleration/deceleration control, when the torque determination means determines that the torque is less than the second threshold value. If the torque determination means determines that the torque is greater than or equal to the second threshold value, the torque determination means may include fourth control means for executing the one-step acceleration/deceleration control. When the temperature of the servo motor is less than the first threshold value and the torque of the servo motor is less than the second threshold value, the numerical controller executes the two-step acceleration/deceleration control, so that the output torque on the high speed side is effectively used. The processing cycle can be shortened. Even if the temperature of the servo motor is below the first threshold, if the torque of the servo motor is above the second threshold, the numerical controller reduces the load on the servo motor, so that the numerical controller does not perform two-step acceleration/deceleration control but one-step acceleration/deceleration. Execute control. Therefore, the numerical control device can reduce the load on the servo motor, so that the failure due to the load on the servo motor can be prevented.

The drive shaft of the numerical controller according to claim 3 is preferably a main shaft of the machine that is rotatable by mounting a tap tool. Generally, heat generation during acceleration/deceleration is larger in the main shaft than in the feed shaft that sends out the main shaft. The feed shaft is an example of a drive shaft. Since the tapping operation repeats acceleration and deceleration of the spindle, the heat generation of the servomotor for driving the spindle increases when the number of machining is large. The present invention provides a numerical control device capable of accelerating and decelerating a rotating spindle by mounting a tap tool, and has the configuration of claim 1 or 2, so that the effect of claim 1 or 2 is obtained during tap operation. be able to.

The control method according to claim 4, wherein a machine including a servomotor and a drive shaft driven by the servomotor is controlled, and an acceleration increasing period during which acceleration is increased at the start of acceleration of the drive shaft, and acceleration of the drive shaft. In a control method of a numerical controller having an acceleration decreasing period for decreasing the acceleration at the end, a temperature judging step of judging whether or not the temperature detected by the temperature detecting means for detecting the temperature of the servo motor is equal to or higher than a first threshold value, When it is determined that the temperature is less than the first threshold value in the temperature determination step, the slope of the acceleration change in the acceleration increasing period is set to be larger than the slope of the acceleration in the acceleration decreasing period, and the temperature is reduced in the acceleration decreasing period. The two-step acceleration/deceleration control is performed in which the acceleration decrease speed of the drive axis is set to the first acceleration decrease speed of the constant first inclination, and then the second acceleration decrease speed of the constant second inclination larger than the first inclination is switched. When the temperature is determined to be equal to or higher than the first threshold value in the first control step and the temperature determination step, the slope of the acceleration change in the acceleration increasing period and the slope of the acceleration change in the acceleration decreasing period are set to be the same. And a second control step for executing one-step acceleration/deceleration control. The numerical control device can obtain the effect described in claim 1 by performing each of the above steps.

The inventions of claims 1 to 3 described above can be arbitrarily combined. For example, all or part of claim 1 may not be provided, and at least one of the other claims 2 or 3 may be provided. However, in particular, it is preferable that the configuration of claim 1 is provided, and that at least one configuration of claim 2 or 3 is combined. Moreover, you may extract and combine the arbitrary components of Claim 1 to 3. The applicant of the present application intends to obtain a patent right for such a configuration.

FIG. 3 is a block diagram showing an electrical configuration of the numerical control device 20 and the machine tool 10. The chart which shows the acceleration change in two-step acceleration/deceleration control of a spindle motor. The chart which shows the acceleration change in one-step acceleration/deceleration control of a spindle motor. The flowchart of tap acceleration/deceleration control processing. Explanatory drawing of the caution threshold value and warning threshold value of the temperature and load torque of a spindle motor, respectively.

Hereinafter, embodiments of the present invention will be described. The numerical controller 20 shown in FIG. 1 controls the axial movement of the machine tool 10 to perform cutting of a work material (not shown) held on the upper surface of a table (not shown). The left-right direction, the front-back direction, and the up-down direction of the machine tool 10 are the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively.

The configuration of the machine tool 10 will be described with reference to FIG. The machine tool 10 performs machining (for example, drilling or tapping) by moving a tool mounted on a spindle extending in the Z-axis direction in the X-axis direction, the Y-axis direction, or the Z-axis direction with respect to a work material held on a table upper surface. It is a vertical machine tool that performs machining, side surface machining, turning, etc.). The machine tool 10 is provided with a spindle mechanism, a spindle moving mechanism, a tool changing device, etc., which are not shown. The spindle mechanism includes a spindle motor 12 and rotates a spindle equipped with a tool. The spindle moving mechanism further includes a Z-axis motor 11, an X-axis motor 13, and a Y-axis motor 14, and moves the spindle in each of the XYZ axial directions relative to a work material supported on the upper surface of a table (not shown). To do. The tool changing device is equipped with a magazine motor 15, drives a tool magazine (not shown) that stores a plurality of tools, and replaces the tool mounted on the spindle with another tool. The Z-axis motor 11, the spindle motor 12, the X-axis motor 13, the Y-axis motor 14, and the magazine motor 15 are servo motors.

The machine tool 10 further includes an operation panel 16. The operation panel 16 includes an input unit 17 and a display unit 18. The input unit 17 is a device for performing various inputs, instructions, settings and the like. The display unit 18 is a device that displays various screens. The operation panel 16 is connected to the input/output unit 25 of the numerical controller 20. The Z-axis motor 11 includes an encoder 11A. The spindle motor 12 includes an encoder 12A. The X-axis motor 13 includes an encoder 13A. The Y-axis motor 14 includes an encoder 14A. The magazine motor 15 includes an encoder 15A. The encoders 11A to 15A are connected to drive circuits 26 to 30 of the numerical control device 20, which will be described later. The machine tool 10 includes a temperature sensor 40. The temperature sensor 40 is attached to the spindle motor 12 and constantly measures the temperature of the spindle motor 12.

The electrical configuration of the numerical controller 20 will be described. The numerical control device 20 includes a CPU 21, a ROM 22, a RAM 23, a storage device 24, an input/output unit 25, drive circuits 26 to 30, and the like. The CPU 21 centrally controls the numerical control device 20. The ROM 22 stores various programs such as a tap acceleration/deceleration control program. The tap acceleration/deceleration control program is a program for executing tap acceleration/deceleration control processing (see FIG. 4) described later. The RAM 23 stores various data during execution of various processes, for example, various flags such as a one-step acceleration/deceleration flag described later. The storage device 24 is a non-volatile memory and stores various data in addition to an NC program for processing, for example. The input/output unit 25 is connected to the operation panel 16. The drive circuits 26 to 30 are servo amplifiers. The drive circuit 26 is connected to the Z-axis motor 11 and the encoder 11A. The drive circuit 27 is connected to the spindle motor 12 and the encoder 12A. The drive circuit 28 is connected to the X-axis motor 13 and the encoder 13A. The drive circuit 29 is connected to the Y-axis motor 14 and the encoder 14A. The drive circuit 30 is connected to the magazine motor 15 and the encoder 15A. In the following description, the Z-axis motor 11, the main-axis motor 12, the X-axis motor 13, the Y-axis motor 14, and the magazine motor 15 are generically referred to as the motors 11 to 15, respectively.

The CPU 21 reads an NC program for processing a work material, and drives a control command for moving each drive axis such as a feed axis (X axis, Y axis, Z axis), a main axis, and a magazine axis to a target position. Send to circuits 26-30. The drive circuits 26 to 30 output drive currents (pulses) to the corresponding motors 11 to 15 according to the control commands (drive signals) received from the CPU 21, respectively. The drive circuits 26 to 30 receive feedback signals (position and speed signals) from the encoders 11A to 15A and perform position control and speed control of the motors 11 to 15. The drive circuits 26 to 30 may be FPGA circuits, for example.

An outline of the drive shaft acceleration/deceleration control applied to the tap operation will be described. The tapping operation is an operation of making a screw by rotating the spindle in the forward direction and making a cut while descending, and then reversing at the bottom of the hole and ascending while the tapping tool is attached to the spindle of the machine tool 10. The former process is tapping and the latter process is tapping back. In the tapping operation, the CPU 21 drives the Z-axis motor 11 while driving the spindle motor 12 to move up and down the spindle. Therefore, the drive axes during the tap operation are the main axis and the Z axis. The Z axis is a feed axis that feeds the main axis. Since the numerical controller 20 effectively uses the output torque of the spindle motor 12 and the Z-axis motor 11 on the high-speed rotation side, the two-step acceleration/deceleration control is basically applied to the tap operation.

As will be described later, the two-step acceleration/deceleration control maximizes the output torque of the servo motor. For example, in the case of a tap cycle in which tap operations are continuously performed, a large load is applied to the Z-axis motor 11 and the spindle motor 12. Since the spindle receives the load directly from the tool that comes into contact with the work material, the heat generated during acceleration/deceleration is generated by the spindle more than the servomotor (Z-axis motor 11, X-axis motor 13, Y-axis motor 14) of the feed axis that sends out the spindle. The motor 12 is larger. In particular, since the tapping operation repeats acceleration and deceleration, the heat generation of the spindle motor 12 increases when the number of machining is large. When the temperature of the servo motor rises, overheat easily occurs. The numerical controller 20 constantly monitors the temperature of the spindle motor 12 in order to suppress overheating of the spindle motor 12. When the temperature of the spindle motor 12 is lower than a caution threshold value, which will be described later, the numerical control device 20 executes the tap operation by the two-step acceleration/deceleration control. When the temperature of the spindle motor 12 is equal to or higher than the caution threshold value, the numerical controller 20 switches to the single-stage acceleration/deceleration control and executes the tap operation in order to reduce the load on the spindle motor 12.

The two-step acceleration/deceleration control of the tap operation will be described with reference to FIG. The CPU 21 determines the respective acceleration patterns of the spindle motor 12 and the Z-axis motor 11 up to the target reaching position based on the tap command generated by interpreting the NC program, for example. The CPU 21 calculates the acceleration based on the determined acceleration pattern and the parameters input by the operator. The CPU 21 transmits the position command obtained from the calculated acceleration command to the drive circuit 27 of the spindle motor 12 and the drive circuit 26 of the Z-axis motor 11.

FIG. 2 is a chart showing an acceleration pattern and a speed pattern of the two-step acceleration/deceleration control of the spindle motor 12 in the tap operation. The operation of the spindle motor 12 at the start of tapping is as follows: the acceleration increasing period T1 at the beginning of acceleration, the first constant acceleration period T2 where the acceleration is constant, the first acceleration decreasing period T3 when the acceleration is reduced in accordance with the end of acceleration, and the end of acceleration. The second acceleration reduction period T4 is divided into four periods.

In the acceleration increasing period T1, the target acceleration is set to A1 calculated by the equation (1) based on the speed V2 input by the worker, and the acceleration increasing speed a1 (a1=A1/T1) is kept constant. The speed V2 is the rotation speed after the second constant acceleration period T2. The acceleration A1 and the speed V2 are set so that the maximum output torque of the spindle motor 12 or a torque near it is used.
・A1=2×V2/(T1+2×T2) (1)

During the first constant acceleration period T2, the acceleration A1 is maintained, and after the lapse of T2, the rotation speed of the spindle motor 12 is controlled to be the speed V2 input by the operator. During this constant acceleration period T2, the acceleration A1 corresponding to the maximum output torque of the spindle motor 12 or a torque near it is maintained, so that the maximum output torque can be effectively used and the rotation time can be shortened.

In the first acceleration decrease period T3, the target acceleration is controlled to be A2, and the first acceleration decrease speed a2 (a2=(A2-A1)/T3) is constant. The target acceleration A2 is calculated using equation (2) based on the velocities V1 and V2 input by the operator.
A2=(2*(V1-V2)-A1*T3)/(T3+T4)...(2)

In the second acceleration decrease period T4, the second acceleration decrease speed a3 (a3=−A2/T4), which is larger than the first acceleration decrease speed a2, is set, and after the end of the second acceleration decrease period T4, The rotation speed of the spindle motor 12 is maintained at the speed V1 input by the operator. The inclination of acceleration change (acceleration increasing speed a1) in the acceleration increasing period T1 is set to be larger than the inclination of acceleration change (acceleration decreasing speed a2, a3) in the acceleration decreasing periods T3 and T4. The first acceleration decrease speed a2 is an acceleration decrease speed with a constant first inclination, and the second acceleration decrease speed a3 is an acceleration decrease speed with a constant second inclination that is larger than the first inclination.

On the other hand, the operation of the spindle motor 12 at the end of tap machining is as follows: the third acceleration reduction period T5 at the beginning of deceleration, the fourth acceleration reduction period T6 in which the acceleration is reduced in accordance with the end of deceleration, and the second constant acceleration period T7 where the acceleration is constant. , The acceleration increase period T8 before the end of deceleration is divided into four periods. A3 and A4 are negative values, and A3<A4 and V3<V1.

In the third acceleration reduction period T5, the target acceleration is set to A3 and A4 calculated by the equations (3) and (4) based on the rotation speeds V1 and V3 input by the worker, and the acceleration reduction speed a4 (a4= Keep A4/T5) constant.
・A3=-2×V3/(2×T7+T8) (3)
・A4=(2×(V3-V1)−A3×T6)/(T5+T6) (4)

In the fourth acceleration reduction period T6, the target acceleration is set to A3, and the acceleration reduction speed a5 (a5=(A3-A4)/T6) is set constant. In the second constant acceleration period T7, the acceleration A3 is maintained, and the rotation speed of the spindle motor 12 is controlled to be the target speed V3 input by the operator. In the acceleration increasing period T8, the acceleration decreasing speed a6 (a6=A3/T8) is kept constant. Note that the acceleration pattern and speed pattern for tapping back performed after tapping are patterns in which the positive and negative signs of the acceleration pattern and speed pattern for tapping are reversed, and therefore a description thereof is omitted.

The one-step acceleration/deceleration control of the tap operation will be described with reference to FIG. FIG. 3 is a chart showing an acceleration pattern and a speed pattern of the one-step acceleration/deceleration control of the spindle motor 12 in the tap operation. Since the one-step acceleration/deceleration control of the tap operation is the same as the general acceleration/deceleration control, it will be briefly described. The operation of the spindle motor 12 at the start of tapping is divided into three periods, that is, an acceleration increasing period T11 at the beginning of acceleration, a first constant acceleration period T12 where the acceleration is constant, and an acceleration decreasing period T13 in which the acceleration is reduced at the end of acceleration. .. The operation of the spindle motor 12 at the end of tapping is divided into three periods, that is, an acceleration increasing period T14 at the beginning of deceleration, a second constant acceleration period T15 where the acceleration is constant, and an acceleration decreasing period T16 before deceleration. Time constant of the acceleration increasing speed in the acceleration increasing period T11, time constant of the acceleration decreasing speed in the acceleration decreasing period T13, time constant of the acceleration increasing speed in the acceleration increasing period T14, and time constant of the acceleration decreasing speed in the acceleration decreasing period T16. Set the same as. The acceleration pattern of the spindle motor 12 is set within the range of the maximum output torque characteristic determined by the rating of the spindle motor 12. In the one-step acceleration/deceleration control, the output torque that can be used on the high-speed rotation side of the spindle motor 12 is smaller than in the two-step acceleration/deceleration control. Therefore, the one-step acceleration/deceleration control can reduce the load on the spindle motor 12 as compared with the two-step acceleration/deceleration control. The acceleration pattern and speed pattern for tapping back performed after tapping are patterns in which the positive and negative signs of the acceleration pattern and speed pattern for tapping are reversed, and a description thereof will be omitted. Since the Z-axis motor 11 is driven synchronously with the spindle motor 12, the acceleration pattern of the Z-axis motor 11 is the same as the acceleration pattern of the spindle motor 12.

The tap acceleration/deceleration control process will be described with reference to FIGS. 4 and 5. Every time the control command generated by interpreting the NC program is the tap command, the CPU 21 reads the tap acceleration/deceleration control program stored in the storage device 24 and executes this processing. The tap command is a control command for executing one cycle of tap operation.

As shown in FIG. 4, the CPU 21 initializes the one-step acceleration/deceleration flag to 0 (S1). The one-step acceleration/deceleration flag is stored in, for example, the RAM 23, and is 1 when the above-described one-step acceleration/deceleration control is executed, and is not executed. Remember 0. The temperature sensor 40 monitors the temperature of the spindle motor 12 when the machine tool 10 is started, for example. The CPU 21 determines whether the temperature of the spindle motor 12 is lower than the caution threshold value (S2). As shown in FIG. 5, in the present embodiment, since the temperature of the spindle motor 12 is monitored, a caution threshold value and a warning threshold value are set as the monitoring temperature. The caution threshold does not have to be stopped immediately, for example, but it is preferable to set the temperature at which the temperature of the spindle motor 12 is further increased and a defect may occur if the machining is continued. The warning threshold may be set to a temperature at which machining should be stopped promptly, and may be determined based on the rating of the spindle motor 12, for example. Further, in this embodiment, after setting the warning threshold, it is preferable to set the caution threshold lower than the warning threshold.

If the temperature of the spindle motor 12 is below the caution threshold (S2: YES), there is no problem with the temperature of the spindle motor 12, so the CPU 21 determines whether the load torque of the spindle motor 12 is below the caution threshold (S5). Even if there is no problem in the temperature of the spindle motor 12, excessive torque may be generated in the spindle motor 12. Particularly in the case of the tapping operation, since the hole formed in the work is tapped while the spindle equipped with the tool is rotated, a relatively large load is applied to the spindle motor 12 as compared with the Z axis which is the feed axis. Therefore, in this embodiment, in addition to the temperature of the spindle motor 12, the load torque of the spindle motor 12 is also monitored. As shown in FIG. 5, in the present embodiment, similarly to the temperature of the spindle motor 12, a caution threshold value and a warning threshold value are set as the monitoring torque. The load torque of the spindle motor 12 may be detected by the drive circuit 27, for example. For example, the caution threshold does not have to be a problem even if the machining is not stopped immediately. However, it is preferable to set the torque value at which the spindle motor 12 is likely to malfunction if the machining is continued. The warning threshold value may be set to a torque value that needs to stop machining promptly, and may be determined based on the rating of the spindle motor 12, for example.

When the load torque of the spindle motor 12 is less than the caution threshold value (S5: YES), the load torque of the spindle motor 12 is not a problem, so the CPU 21 determines whether the one-step acceleration/deceleration flag stored in the RAM 23 is 1 (S8). When the one-step acceleration/deceleration flag is 0 (S8: NO), the CPU 21 executes the tap operation by the two-step acceleration/deceleration control (S9). As described above, in the two-step acceleration/deceleration control, in order to maintain the acceleration A1 corresponding to the maximum output torque of the spindle motor 12 or the torque in the vicinity thereof during the first constant acceleration period T2, the two-step acceleration/deceleration control is It is possible to effectively use the maximum output torque and shorten the rotation time. After the tap operation ends, the CPU 21 ends the present process.

When the temperature of the spindle motor 12 is equal to or higher than the caution threshold value (S2: NO), the CPU 21 determines whether the temperature of the spindle motor 12 is lower than the warning threshold value (S3). When the temperature of the spindle motor 12 is lower than the warning threshold value (S3: YES), the machining does not have to be stopped immediately, but when the tap operation is performed by the two-step acceleration/deceleration control, the temperature of the spindle motor 12 rises rapidly. Therefore, the CPU 21 sets the one-step acceleration/deceleration flag to 1 (S4). If the torque load of the spindle motor 12 is less than the caution threshold value (S5: YES), the CPU 21 proceeds to S5 and the one-step acceleration/deceleration flag stored in the RAM 23 is 1 (S8: YES). A tap operation is executed (S10). As described above, the output torque that can be used on the high speed side of the spindle motor 12 in the one-step acceleration/deceleration control is smaller than that in the two-step acceleration/deceleration control (see the constant acceleration period T12 in FIG. 3 ). Therefore, the one-step acceleration/deceleration control can perform the tap operation while reducing the load on the spindle motor 12 as compared with the two-step acceleration/deceleration control. After the tap operation ends, the CPU 21 ends the present process.

If the temperature of the spindle motor 12 is equal to or higher than the warning threshold value (S3: NO), the spindle motor 12 is in an overheated state, so the CPU 21 outputs an alarm and immediately stops the machining (S12), and ends this processing. Therefore, the CPU 21 can prevent the spindle motor 12 from overheating.

Even when the temperature of the spindle motor 12 is lower than the caution threshold value (S2: YES), the load of the spindle motor 12 is large especially in the tap operation, so that the load torque of the spindle motor 12 may be large. When the load torque of the spindle motor 12 is equal to or higher than the caution threshold value (S5: NO), the CPU 21 determines whether the load torque of the spindle motor 12 is less than the warning threshold value (S6). When it is less than the warning threshold value (S6: YES), the CPU 21 sets the one-step acceleration/deceleration flag to 1 (S7). Since the one-step acceleration/deceleration flag is 1 (S8: YES), the CPU 21 executes the tap operation by the one-step acceleration/deceleration control (S10). As described above, the output torque that can be used on the high-speed rotation side of the spindle motor 12 is smaller in the one-step acceleration/deceleration control than in the two-step acceleration/deceleration control. Therefore, the one-step acceleration/deceleration control can perform the tap operation while reducing the load on the spindle motor 12 as compared with the two-step acceleration/deceleration control. After the tap operation ends, the CPU 21 ends the present process.

Even if the temperature of the spindle motor 12 is below the caution threshold (S2: YES), but the load torque of the spindle motor 12 is equal to or higher than the warning threshold (S5: NO, S6: NO), excessive torque is generated in the spindle motor 12. Therefore, the CPU 21 outputs an alarm and immediately stops the processing (S12), and ends this processing. Therefore, the CPU 21 can prevent a failure of the spindle motor 12 due to an excessive torque load.

For example, when the temperature of the spindle motor 12 is within the range of the caution threshold value or more and less than the warning threshold value, the tap operation is continuously performed in the one-step acceleration/deceleration control, and then the temperature of the spindle motor 12 drops below the caution threshold value. If the load torque of the spindle motor is less than the caution threshold value (S2:YES) (S5:YES), the one-step acceleration/deceleration flag is 0 (S8:NO). The tap operation can be performed by switching to control (S9). Therefore, the numerical controller 20 can switch between the two-step acceleration/deceleration control and the one-step lower acceleration/deceleration control based on the temperature of the spindle motor 12.

As described above, the CPU 21 monitors the load state of the spindle motor 12 in two stages, the temperature of the spindle motor 12 and the load torque. As shown in FIG. 5, as a first determination, the CPU 21 determines which of the three temperature ranges the temperature of the spindle motor 12 is divided into by two threshold values. When the temperature of the spindle motor 12 is within the range of the caution threshold value or more and the warning threshold value or less, the CPU 21 determines the one-step acceleration/deceleration control. When the temperature of the spindle motor 12 is equal to or higher than the warning threshold value, the CPU 21 immediately stops the machining. When the temperature of the spindle motor 12 is lower than the caution threshold value, as a second determination, it is determined to which of the three torque ranges the load torque of the spindle motor 12 belongs to is divided into two threshold values. When the load torque of the spindle motor 12 is within the range of the caution threshold value or more and the warning threshold value or less, the CPU 21 determines the one-step acceleration/deceleration control. When the load torque of the spindle motor 12 is equal to or higher than the warning threshold value, the CPU 21 immediately stops the machining. When the load torque of the spindle motor 12 is less than the caution threshold, the CPU 21 determines the two-step acceleration/deceleration control.

Since the temperature of the spindle motor 12 rises in a stack as the spindle motor 12 continuously operates, the CPU 21 can detect a temperature change associated with the continuous operation of the spindle motor 12. On the other hand, since the load torque changes instantaneously according to the load of the spindle motor 12, it is possible to detect the instantaneous load of the spindle motor 12, but the load torque alone can accumulate the load that accompanies the continuous operation of the spindle motor 12. Cannot be detected. Therefore, the CPU 21 determines the temperature of the spindle motor 12 as the first determination, and only when the temperature of the spindle motor 12 is less than the caution threshold value, the CPU 21 confirms whether excessive torque is generated in the spindle motor 12. As the second determination, the load torque of the spindle motor 12 is determined. Therefore, the CPU 21 can accurately detect the load state of the spindle motor 12.

As described above, the numerical controller 20 of this embodiment controls the operation of the machine tool 10. The machine tool 10 includes various motors 11 to 15 and drive shafts driven by the various motors 11 to 15. The various motors 11 to 15 are servo motors. The CPU 21 of the numerical controller 20 has an acceleration increasing period and an acceleration decreasing period in the acceleration control of the drive axis. The acceleration increasing period is a period in which the acceleration is increased at the start of acceleration of the drive shaft. The acceleration reduction period is a period in which the acceleration is reduced in two steps at the end of acceleration of the drive shaft. The temperature sensor 40 detects the temperature of the spindle motor 12. During the tap operation, the CPU 21 determines whether the temperature of the spindle motor 12 is lower than the caution threshold value. During the tap operation, the CPU 21 drives the spindle motor 12 and the Z-axis motor 11 simultaneously. When the temperature of the spindle motor 12 is less than the caution threshold value, the CPU 21 executes the two-step acceleration/deceleration control for the acceleration/deceleration control of the spindle motor 12 and the Z-axis motor 11.

In the two-step acceleration/deceleration control, the inclination of the acceleration change in the acceleration increasing period T1 is set to be larger than the inclination of the acceleration in the acceleration decreasing periods T3 and T4, and the acceleration decreasing speed of the spindle motor 12 is constant during the first acceleration decreasing period T3. After the first acceleration decreasing speed a2 of the first inclination is set, the control is switched to the second acceleration decreasing speed a3 of the second inclination which is larger than the first inclination in the second acceleration decreasing period T4. When the temperature of the spindle motor 12 is equal to or higher than the caution threshold value, the CPU 21 executes one-step acceleration/deceleration control for the acceleration/deceleration control of the spindle motor 12 and the Z-axis motor 11. The one-step acceleration/deceleration control is control in which the slope of the acceleration change in the acceleration increasing period and the slope of the acceleration change in the acceleration decreasing period are set to be the same.

Therefore, the numerical control device 20 can use the output torque on the high speed side when the temperature of the spindle motor 12 is low, so that the machining cycle can be shortened. When the temperature of the spindle motor 12 is high, the numerical controller 20 can automatically switch to the one-step acceleration/deceleration control to suppress overheating of the spindle motor 12 and the Z-axis motor 11, so that the spindle motor 12 and the Z-axis motor 11 can be operated for a long time. I can drive.

Particularly in the above embodiment, the drive circuit 27 of the spindle motor 12 detects the load torque of the spindle motor 12. When the CPU 21 determines that the temperature detected by the temperature sensor 40 is lower than the caution threshold, the CPU 21 determines whether the load torque detected by the drive circuit 27 is equal to or higher than the caution threshold of the load torque. When the load torque of the spindle motor 12 is less than the caution threshold value, the CPU 21 executes the two-step acceleration/deceleration control. When the load torque of the spindle motor 12 is equal to or higher than the caution threshold value, the CPU 21 executes one-step acceleration/deceleration control in order to reduce the load applied to the spindle motor 12. Therefore, the numerical controller 20 can reduce the load on the spindle motor 12 and the Z-axis motor 11, so that the spindle motor 12 and the Z-axis motor 11 can be operated for a long time.

In the above description, the machine tool 10 is an example of the machine of the present invention. The temperature sensor 40 is an example of the temperature detecting means of the present invention. The CPU 21 that executes the process of S2 in FIG. 4 is an example of the temperature determination means of the present invention. The first acceleration decrease speed a2 is an example of the first acceleration decrease speed of the present invention. The second acceleration decrease speed a3 is an example of the second acceleration decrease speed of the present invention. S2: YES, the CPU 21 that executes the processes of S9 is an example of the first control means of the present invention. The CPU 21 that executes the processes of S2: NO, S4, S8: YES, and S10 is an example of the second control means of the present invention. The temperature caution threshold value is an example of the first threshold value of the present invention. The caution threshold value of the load torque is an example of the second threshold value of the present invention. The CPU 21 that executes the processing of S5 is an example of the torque determination means of the present invention. S5: YES, the CPU 21 that executes the processes of S9 is an example of the third control means of the present invention. CPU21 which performs the process of S5:NO, S7, S8:YES, and S10 is an example of the 4th control means of this invention. The process of S2 is an example of the temperature determination process of the present invention. Each processing of S1, S2: YES, S8: NO, S9 is an example of the first control step of the present invention. Each processing of S2:NO, S4, S8:YES, and S10 is an example of the second control step of the present invention.

Needless to say, the present invention is not limited to the above-described embodiment and various modifications can be made. In the above embodiment, the temperature of the spindle motor 12 is monitored, and when the temperature of the spindle motor 12 becomes equal to or higher than the caution threshold value during tap operation, the two-step acceleration/deceleration control is switched to the one-step acceleration/deceleration control. The numerical controller 20 may switch between the two-step acceleration/deceleration control and the one-step acceleration/deceleration control for the acceleration/deceleration of the feed shaft based on the temperature of the spindle motor 12 even in operations other than the tap operation.

The numerical controller 20 may monitor the temperature of, for example, the servomotor (Z-axis motor 11, X-axis motor 13, Y-axis motor 14) of the feed axis that sends out the main axis. The numerical controller 20 may switch between the two-step acceleration/deceleration control and the one-step acceleration/deceleration control for the acceleration/deceleration of the feed axis, based on the temperature of the servomotor of the feed axis.

In the above embodiment, the first determination for determining the temperature of the spindle motor 12 is performed, and when the temperature of the spindle motor 12 is less than the caution threshold value, the second determination for determining the load torque of the spindle motor 12 is performed. The second determination may be omitted. That is, when the temperature of the spindle motor 12 is lower than the caution threshold value, the CPU 21 may perform the two-step acceleration/deceleration control.

Although the drive circuits 26 to 30 of the above embodiment are provided in the numerical control device 20, they may be provided in the machine tool 1.

The machine tool 10 of the above-described embodiment is a vertical machine tool whose main axis extends in the Z-axis direction, but the present invention can also be applied to a horizontal machine tool whose main axis extends in the horizontal direction.

In the present embodiment, instead of the CPU 21, a microcomputer, ASIC (Application Specific Integrated Circuits), FPGA (Field Programmable Gate Array) or the like may be used as a processor. The movement control process may be distributed by a plurality of processors. The ROM 22 and the storage device 24 that store the program may be configured by another non-transitory storage medium such as an HDD and/or a storage device. The non-transitory storage medium may be any storage medium that can retain information regardless of the period in which the information is stored. Non-transitory storage media may not include transitory storage media (eg, transmitted signals). The tap acceleration/deceleration control program may be downloaded from a server connected to a network (not shown) (that is, transmitted as a transmission signal) and stored in a storage device such as a flash memory. In this case, the program may be stored in a non-temporary storage medium such as an HDD provided in the server.

10 Machine tool 11 Z-axis motor 12 Spindle motor 20 Numerical control device 21 CPU
27 Drive circuit 40 Temperature sensor

Claims (4)

A machine equipped with a servo motor and a drive shaft driven by the servo motor is controlled, and an acceleration increasing period in which the acceleration is increased at the start of acceleration of the drive shaft and an acceleration decrease period in which the acceleration is decreased at the end of acceleration of the drive shaft. In a numerical control device having a period,
Temperature determining means for determining whether the temperature detected by the temperature detecting means for detecting the temperature of the servo motor is less than a first threshold value,
When the temperature determination unit determines that the temperature is less than the first threshold value, the slope of the acceleration change in the acceleration increasing period is set to be larger than the slope of the acceleration in the acceleration decreasing period, and the temperature is decreased in the acceleration decreasing period. The two-step acceleration/deceleration control is performed in which the acceleration decrease speed of the drive axis is set to the first acceleration decrease speed of the constant first inclination, and then the second acceleration decrease speed of the constant second inclination larger than the first inclination is switched. First control means for
When the temperature determination means determines that the temperature is equal to or higher than the first threshold value, a one-step acceleration/deceleration control is performed to set the slope of acceleration change during the acceleration increase period and the slope of acceleration change during the acceleration decrease period to be the same. And a second control means for controlling the numerical control device. When the temperature determination means determines that the temperature is less than the first threshold value, the torque detection means that detects the torque of the servo motor includes a torque determination means that determines whether the torque is less than a second threshold value,
The first control means,
When the torque determination means determines that the torque is less than the second threshold value, third control means for executing the two-step acceleration/deceleration control,
The numerical control device according to claim 1, further comprising a fourth control unit that executes the one-step acceleration/deceleration control when the torque determination unit determines that the torque is equal to or more than the second threshold value. The numerical control device according to claim 1, wherein the drive shaft is a main shaft of the machine that is rotatable by mounting a tap tool. A machine equipped with a servo motor and a drive shaft driven by the servo motor is controlled, and an acceleration increasing period in which the acceleration is increased at the start of acceleration of the drive shaft and an acceleration decrease period in which the acceleration is decreased at the end of acceleration of the drive shaft. In a control method of a numerical controller having a period,
A temperature determining step of determining whether or not the temperature detected by the temperature detecting means for detecting the temperature of the servo motor is equal to or higher than a first threshold value;
When it is determined that the temperature is less than the first threshold value in the temperature determination step, the slope of the acceleration change in the acceleration increasing period is set to be larger than the slope of the acceleration in the acceleration decreasing period, and the temperature is reduced in the acceleration decreasing period. The two-step acceleration/deceleration control is performed in which the acceleration decrease speed of the drive axis is set to the first acceleration decrease speed of the constant first inclination, and then the second acceleration decrease speed of the constant second inclination larger than the first inclination is switched. A first control step to
When it is determined that the temperature is equal to or higher than the first threshold value in the temperature determination step, the one-step acceleration/deceleration control is performed to set the slope of the acceleration change in the acceleration increasing period and the slope of the acceleration change in the acceleration decreasing period to be the same. And a second control step for performing the control method.

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