JP2003199378A - Spindle motor controller for machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the warming up time especially when the rotor of a motor is in stationary state. <P>SOLUTION: The motor controller of a machine where thermal displacement has an effect on the machining accuracy and the positioning accuracy comprises a circuit for switching the control between a warming up mode and a normal machining mode wherein the motor is applied with a harmonic voltage having a frequency higher than the driving frequency in the warming up mode. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device.

[0002]

2. Description of the Related Art Conventionally, in a machine tool such as a grinding machine which requires high machining accuracy, when machining is started from a cold state of the machine, as the temperature of the spindle motor increases, thermal displacement occurs on the shaft, resulting in poor machining accuracy. It was For this reason, it was necessary to repeat the normal operation in advance and perform the warm-up operation until the temperature of the machine became saturated before the actual machining work was started to make the temperature constant. In recent years, a built-in motor in which a motor is embedded in a main shaft has become mainstream for downsizing of a machine, and heat generation of the motor is transmitted to a shaft, which is a major cause of thermal displacement. Therefore, for thermal displacement and energy saving, not an induction motor but an IPM (Interior permanent magnet) synchronous motor, which has a structure in which a permanent magnet is embedded in a rotor core, has begun to be used.

[0003]

In recent years, the non-machining time has been shortened by shortening the tool exchange time and the positioning time, and the warming-up time before machining hinders the efficiency of the machine. . Especially in the IPM synchronous motor,
Compared with an induction motor, there is no secondary copper loss, so the motor generated loss is small, so there is the advantage that the generated loss during processing can be made small. However, there is a problem in that the warm-up time is long because the loss generated during the warm-up operation before processing is small. The present invention has been made in view of such problems, and a first object thereof is to shorten the warm-up operation time. In addition, even if the machine cannot be moved before performing normal machining (that is, the motor cannot be rotated), warm-up operation can be performed in a short time with the rotor of the motor stationary. The second purpose is to

[0004]

In order to solve the above problems, the present invention switches between a warm-up operation mode in which the temperature is raised before machining and a normal operation mode in which normal machining is performed. Alternatively, a voltage is applied to the motor to increase copper loss and iron loss, and control is performed to accelerate the temperature rise. In the normal mode, the high frequency command is cut off and normal control is performed. According to a first aspect of the present invention, in a motor control device for a machine in which thermal displacement affects machining accuracy and positioning accuracy, a switching control circuit that switches control between a warm-up operation mode in which warm-up operation is performed and a normal mode in which normal machining is performed. In the warm-up operation mode, the spindle motor control device for machine tools is characterized in that a harmonic voltage having a frequency higher than the drive frequency is applied to the motor in a superimposed manner. According to a second aspect of the present invention, in a motor control device for a machine in which thermal displacement affects machining accuracy, positioning accuracy, etc., switching is performed to switch control between a warm-up operation mode in which warm-up operation is performed and a normal mode in which normal machining is performed. A spindle motor control device for machine tools, comprising a control circuit, wherein a harmonic current having a higher frequency than a drive frequency is superimposed and applied to a motor in a warm-up operation mode. Further, the invention according to claim 3 is a means for measuring a temperature of a motor or a machine, a means for determining a warming-up operation mode for performing warming-up operation based on the measured temperature, and a switching control circuit for switching control between the warming-up operation mode and the normal mode. 3. The spindle motor control device for a machine tool according to claim 1, further comprising: a harmonic current having a frequency higher than a drive frequency in the warm-up operation mode to be superposed on the motor. Further, the invention according to claim 4 is an IPM synchronous motor in which the motor is a structure in which a permanent magnet is embedded in a rotor iron, and the machine tool according to any one of claims 1 to 3. It is a spindle motor control device.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the warming-up operation, the voltage or current of the harmonic components is superposed in the warming-up operation to increase the iron loss and the copper loss and accelerate the temperature rise. The time can be shortened. Further, when the machine cannot be moved before the normal machining or the like, warm-up operation can be performed by applying a harmonic or direct current voltage or current. Less than,
An embodiment of the present invention will be described with reference to the drawings. The first embodiment is shown in FIG. Reference numeral 1 is a speed command given by the host controller, 2 is a speed controller for keeping the speed constant with respect to the given speed command, and 3 is a mode for switching between the normal operation mode and the warm-up operation mode provided by the host controller. Switching command, 4 is a harmonic signal generation circuit,
Reference numeral 5 is a switch which is turned on / off according to the instruction of 3, and 6 is a high frequency current instruction Icom output from the harmonic signal generating circuit.
p and 7 are current commands Iref output from the speed controller,
Reference numeral 8 is an adder for performing addition calculation, 10 is a current controller for controlling the current according to the current command, 11 is a voltage command Vref output from the current controller, and 12 is a power element of the power conversion circuit according to the voltage command Vref. A PWM generating circuit that creates a PWM signal, and 13 is a power conversion circuit that supplies a variable voltage / current of a variable frequency to the motor in accordance with a signal given from the PWM generating circuit. Reference numeral 17 is a motor driven by 13.

When it is necessary for the operator to raise the temperature before processing, the operator turns on the mode switching signal 3 through a host controller such as an NC controller to put SW1 in a connected state. As the speed command, the same speed command as the conventional machining program is given. Current command (Iref) of 7 obtained from speed controller when SW1 is turned on (connection state)
6 high-frequency current command (Icomp) output from the high-frequency generator circuit 4 is added by the adder 8 and given to the current controller. The high-frequency signal generating circuit 4 generates a high-frequency signal that cannot be followed by the motor from the table, or generates a signal such as a SIN waveform or a square wave that repeats positive and negative by calling or calculation. The current controller 10 has a current command including the harmonics added in 8 (Ir
ef + Icomp), and 10 current controllers calculate the required voltage accordingly and pass 11 Vref to 12 PWM generation circuits, and finally 13 power conversion circuits included harmonics to the motor. Output current. In the warm-up operation mode, when a current containing harmonics flows into the motor for a certain period of time, the motor 14 generates the harmonics in addition to the heat generated by normal operation.
The iron loss and copper loss of the motor increase and the motor temperature rises faster. When the temperature rises to a predetermined temperature, the mode selector switch SW1 is switched to the normal mode via the host controller, the high frequency signal (Icomp) is disconnected, and the normal control is resumed.

Next, a second embodiment is shown in FIG. The same names as those in FIG. 1 are denoted by the same reference numerals, and duplicated description will be omitted. Figure 1
2, the harmonic signal is added to the current command, but in FIG. 2, the harmonic signal is added to the voltage command. The difference from FIG. 1 is the embodiment in which the changeover switch (SW1) is connected to the voltage command (Vref) output from the current controller, and the high frequency command is also added with the voltage-converted harmonic voltage command (Vcomp). As for switching, SW1 is operated by a mode switching command from the host controller, as in FIG. 1, and is turned on (connected) in the warm mode and turned off (disconnected) in the normal mode.

Next, a third embodiment is shown in FIG. 3 is different from FIG. 2 in that FIG. 3 receives a temperature detection signal 15 from a temperature detector such as a thermal attached to a motor or a machine instead of receiving a mode switching command from a host controller, and the detected temperature is constant. When it is lower than the value of, the warm-up mode is determined, and when it is higher, the warm-up mode determination means 16 is a determination circuit for determining the normal mode. Further, although the harmonic voltage command is superimposed in FIG. 3, the case of superimposing the harmonic current command can be considered in the same manner. Furthermore, although an example in which the harmonic command is created using the harmonic generation circuit and the adder is shown, it is also possible to add a harmonic component to the basic command by using a table or the like by software. The harmonic signal output from the harmonic generation circuit has a frequency that does not allow the motor to rotate or follow, so the motor does not rotate. Especially when the present invention is applied to the IPM motor, the warm-up operation time can be shortened.

[0009]

As described above, according to the present invention,
In the warm-up operation, by superposing the harmonic voltage or current, the iron loss and the copper loss of the motor can be increased and the temperature rise of the motor can be promoted, so that the warm-up operation time can be shortened. Further, when the machine cannot be moved before performing the normal machining or the like, warm-up operation can be performed with the rotor of the motor being stationary by applying a harmonic voltage or current.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention in which a harmonic current command is superimposed.

FIG. 2 is a configuration diagram of a second embodiment of the present invention in which a harmonic voltage command is superimposed.

FIG. 3 is a configuration diagram of a third embodiment of the present invention in which a harmonic voltage command is superimposed.

[Explanation of symbols]

1 Speed command 2 speed controller 3 Mode switching command 4 Harmonic signal generation circuit 5 switches 6 High frequency current command 7 Current command 8 adder 10 Current controller 11 Voltage command 12 PWM generation circuit 13 Power conversion circuit 14 Harmonic voltage command 15 Temperature detection signal 16 Warm-up mode determination circuit 17 motor Iref Current command calculated by speed controller Icomp High frequency current command Vref Voltage command calculated by current controller Vcomp High frequency voltage command SW1 mode selector switch

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H001 AA02 AB11 AC02 AD05 AE02                 5H576 AA17 DD07 EE11 FF01 GG02                       GG04 GG07

Claims (4)

[Claims] 1. A motor control device for a machine in which thermal displacement affects machining accuracy, positioning accuracy, etc., comprising a switching control circuit for switching control between a warm-up operation mode for performing warm-up operation and a normal mode for performing normal machining, A spindle motor control device for machine tools, characterized in that, in the warm-up operation mode, a harmonic voltage having a higher frequency than the drive frequency is superimposed and applied to the motor. 2. A motor control device for a machine in which thermal displacement affects machining accuracy, positioning accuracy, etc., comprising a switching control circuit for switching control between a warm-up operation mode for performing warm-up operation and a normal mode for performing normal machining, A spindle motor control device for machine tools, characterized in that, in the warm-up operation mode, a harmonic current having a higher frequency than the drive frequency is superimposed and applied to the motor. 3. A warm-up operation comprising means for measuring the temperature of a motor or machine, means for determining a warm-up operation mode for performing warm-up operation based on the measured temperature, and a switching control circuit for switching control between the warm-up operation mode and the normal mode. 3. In the mode, a harmonic current having a frequency higher than the driving frequency is superimposed and given to the motor.
Spindle motor control device for machine tool described. 4. The spindle motor controller for a machine tool according to claim 1, wherein the motor is an IPM synchronous motor having a structure in which a permanent magnet is embedded in a rotor iron.