JP2012135118A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device capable of extending the service life of a switching element by implementing driving suited to an operating condition without increasing an operation burden.SOLUTION: The inverter device, driving a machining motor 10 under a plurality of operating conditions with a power module 20 using a PWM modulation system, includes: carrier generation means for setting a pattern of a carrier frequency of the PWM modulation system in accordance with the plurality of operating conditions.

Description

  The present invention relates to an inverter device, and more particularly to an inverter device that drives a motor for a processing machine under a plurality of operating conditions by a power module using a PWM modulation method.

  Conventionally, in a stationary inverter that drives an electric motor by performing PWM control on the main circuit element of the inverse conversion unit and obtaining an output including the vicinity of the zero frequency in the inverse conversion unit, the output frequency of the inverse conversion unit is set in advance. Determination means for determining that the output current is lower and higher than a preset set value, and switching means for switching the carrier frequency of PWM control from a normal frequency to a lower frequency when a determination output is obtained in the determination means. What was provided is known (for example, refer patent document 1).

  According to such a static inverter, when the motor speed is near zero, the switching frequency of the main circuit element is lowered, the switching loss of the main circuit element is reduced, and the life of the element is reduced when the motor speed is near zero. Can be extended.

JP 2001-275393 A

  However, in the configuration described in Patent Document 1, it is necessary to constantly monitor the carrier frequency and the output current of the inverse conversion unit and operate the determination unit, so that there is a problem that the calculation burden increases.

  Therefore, an object of the present invention is to provide an inverter device that can perform driving suitable for operating conditions without increasing the calculation burden and extend the life of the switching element.

In order to achieve the above object, an inverter device according to a first aspect of the present invention is an inverter device that drives a motor for a processing machine under a plurality of operating conditions by a power module using a PWM modulation method,
It has carrier generating means for setting a carrier frequency pattern of the PWM modulation system corresponding to the plurality of operating conditions.

  As a result, it is possible to set an appropriate carrier frequency pattern corresponding to the operating conditions. By setting the carrier frequency according to the degree of necessity of control responsiveness, it is possible to extend the life of the power module and perform appropriate control. Sex can be made compatible.

A second invention is an inverter device according to the first invention,
The carrier frequency pattern has a normal mode of a normal frequency and a low carrier frequency mode of a frequency lower than the normal mode,
The normal mode and the low carrier frequency mode can be selected according to the plurality of operating conditions.

  As a result, when the driver wants to make a selection in consideration of various situations, the driver can make a selection setting and perform flexible driving.

A third invention is an inverter device according to the second invention, wherein
The low carrier frequency mode has a plurality of modes.

  As a result, it is possible to perform appropriate driving according to operating conditions, and it is possible to achieve both a long life of the power module and appropriate controllability.

A fourth invention is an inverter device according to any one of the first to third inventions,
Temperature information detecting means for detecting temperature information related to the temperature of the power module;
The apparatus further comprises correction means for correcting the carrier frequency based on the temperature information detected by the temperature information detection means.

  Thereby, the temperature of the power module is also taken into consideration, and the carrier frequency is corrected as necessary to obtain an appropriate carrier frequency, whereby more appropriate driving can be performed.

A fifth invention is an inverter device according to the fourth invention,
The correction by the correction means is correction for changing the carrier frequency to a lower frequency side.

  As a result, the life of the power module can be extended, and when the carrier frequency can be lowered, driving with a low carrier frequency can be actively promoted.

A sixth invention is an inverter device according to any one of the first to fifth inventions,
The operating condition is a condition determined according to a process.

  As a result, the operating conditions can be determined on a process basis, and the carrier frequency can be set simply and appropriately.

7th invention is the inverter apparatus which concerns on 6th invention,
The carrier frequency pattern is characterized in that the mode is switched based on the process switching timing.

  Thereby, mode switching can be performed simply and rationally, and the life of the power module can be reliably extended.

  According to the present invention, it is possible to extend the life of the power module while maintaining appropriate controllability.

It is the block diagram which showed an example of the inverter apparatus which concerns on the Example of this invention. It is the figure which showed an example of the temperature detection means attached to the power module. It is the figure which showed the example of the change of the operating condition of the injection motor and the mold opening / closing motor in injection molding processing, and the setting change of a carrier frequency. FIG. 3A is a diagram showing an example of the carrier frequency of the injection motor. FIG. 3B is a diagram showing an example of the process of the injection unit. FIG. 3C is a diagram illustrating an example of the mold opening / closing unit. FIG. 3D is a diagram showing an example of the carrier frequency of the mold opening / closing motor.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram illustrating an example of an inverter device according to an embodiment of the present invention. In FIG. 1, the inverter apparatus according to the present embodiment includes a power module 20, a temperature detection means 30, a smoothing capacitor 40, a converter unit 50, a three-phase AC power supply 60, a carrier generation means 70, and a carrier frequency setting. A means 80, a controller 90, and a PWM (Pulse Width Modulation) signal generating means 100 are provided. Further, the carrier generating means 70 includes a correcting means 71 inside. In FIG. 1, a motor 10 to be driven is shown as a related component.

  A power module 20 is connected to the motor 10, and the motor 10 is driven by switching driving of the power module 20. Further, the power module 20 is connected to the PWM signal generating means 100, and the power module 20 is switching driven by the PWM signal output from the PWM signal generating means 100. The power module 20 is connected to the smoothing capacitor 40 in the previous stage and the converter unit 50 in the previous stage of the smoothing capacitor 40, and the converter unit 50 is connected to the three-phase AC power source 60. The PWM signal generating means 100 is connected to the carrier generating means 70 so as to be supplied with the carrier, and is connected to the controller 90 so as to be supplied with a voltage command signal. The carrier generation means 70 is connected to a carrier frequency setting means 80.

  The motor 10 is a motor 10 for a processing machine, and various motors for processing machines can be used. For example, a motor used for an injection molding machine or a motor used for other processing machines may be used. A three-phase induction motor is generally used as the motor.

  The power module 20 is a drive unit that switches the motor 10. For the power module 20, a semiconductor element may be used, and for example, an IGBT (Insulator Gate Bipolar Transistor), a power MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor), or the like may be used. In FIG. 1, the power module 20 is shown as a single transistor for the sake of space, but in reality, a plurality of power modules 20 may be provided, for example, two transistors are provided in each of three phases. It may be. The power module 20 functions as an inverter unit that converts direct current into alternating current.

  A smoothing capacitor 40 and a converter unit 50 are provided before the power module 20 that functions as an inverter unit, and are connected to a three-phase AC power source 60. The converter unit 50 rectifies and converts the three-phase AC voltage supplied from the three-phase AC power source 60 into a DC voltage. Therefore, the converter unit 50 includes a diode. The smoothing capacitor 40 smoothes the converted DC voltage and supplies it to the power module 20 that is an inverter unit. The power module 20 that is an inverter unit sequentially switches the DC voltage smoothed by the smoothing capacitor 20 and outputs a variable voltage and a variable frequency.

  The temperature detection unit 30 is a unit that detects temperature information related to the temperature of the power module 20 and detects the temperature of the power module 20, and may be provided as necessary. Here, the information related to the temperature is information that is related to the temperature change of the power module 20 such as the temperature and current of the power module 20 and the number of rotations of the motor 10 and can detect the temperature of the power module 20. means. From these pieces of information, the temperature of the power module 20 can be estimated, and the temperature of the power module 20 can be detected directly or indirectly.

  FIG. 2 is a diagram showing an example of the temperature detection means 30 attached to the power module 20. In FIG. 2, temperature detection means 30 is provided in the immediate vicinity of the power module 20. For example, the temperature detection unit 30 may be provided in the vicinity of the power module such as the side surface of the case of the power module 20 or the heat sink 21. The temperature detecting means 30 is not essential and may be provided as necessary.

  Returning to FIG. The carrier generating means 70 is means for generating a carrier by setting a carrier frequency. In the inverter device according to the present embodiment, the carrier generating means 70 sets the carrier frequency according to the operating conditions. In a processing machine, the operating conditions are often different depending on the processing process, so the operating conditions are determined according to the processing process. Like the carrier frequency change P shown in the carrier generating means 70, the carrier frequency f is set to the normal mode of the normal frequency fn and the low carrier frequency mode of the low carrier frequency f1 depending on the process. There is a case. In FIG. 1, in the process A and the process C, the normal mode is set, but in the process B, the low carrier frequency mode is set. For example, in the injection molding process, in the pressure holding process for keeping the pressure constant after the injection process, the mold clamping process for pressing the mold, etc., the rotation of the motor 10 itself is slow, but the torque is continuously applied at the same position. The load itself is a high process. In such a process, high control responsiveness is not required, which is an operating condition that requires the motor 10 to operate at a low speed. In such a case, if the carrier frequency f continues to be maintained at the normal frequency fn, the power module 20 generates heat when it is switched at high speed, and is strongly subjected to thermal stress. It will lead to a long life. Therefore, in the inverter device according to the present embodiment, the setting of the carrier frequency f is changed in accordance with the required change in the operation condition, paying attention to the difference in the operation condition due to the difference in the process. The carrier generating means 70 automatically sets an appropriate carrier frequency based on such a plurality of operating conditions.

  In the carrier frequency waveform Q corresponding to the carrier frequency change P, the carrier period of the waveform corresponding to the process B is longer than that in the process A and the process C. Thereby, the switching cycle of the power module 20 can be lengthened to reduce the number of times of switching per unit time, and the consumption of the power module 20 can be reduced. In this way, the carrier frequency is changed according to the operating conditions, and under the operating conditions that do not require high-speed switching, the carrier frequency is decreased to reduce the switching of the power module 20 and maintain appropriate controllability. However, the life of the power module 20 can be extended.

  In the present embodiment, the carrier frequency is switched based on the change of the operating condition due to the process switching, not the detection of the output current or the like. This is unnecessary, and appropriate switching control can be performed with a simple configuration.

  The carrier generating unit 70 may include a correcting unit 71 as necessary. The correction unit 71 is a unit that corrects the carrier frequency that is once set in accordance with the operating conditions in accordance with the temperature of the power module 20 detected by the temperature detection unit 30. For example, even in the process where the carrier frequency is set to the normal frequency fn, the normal frequency fn is not always appropriate, and the process / situation where high control responsiveness is required and the frequency are reduced. However, there are processes and situations that are not a big problem. For example, even in the step where the carrier frequency is set to the normal frequency fn, if the temperature detecting unit 30 detects that the power module 20 is at a high temperature equal to or higher than a predetermined temperature, the carrier frequency fn is decreased. It is preferable to perform correction. In such a case, the correction unit 71 performs correction control for reducing the carrier frequency within a range where no problem occurs in controllability even if the carrier frequency is reduced. That is, control is performed to lower the carrier frequency and lower the switching frequency of the power module 20 under a process / situation where no problem occurs even if the carrier frequency is lowered. As a result, appropriate drive control can be performed in consideration of the temperature state of the power module 20 as long as the controllability is not affected. It should be noted that the carrier frequency reduction width by the correction means 71 may be the same as that of the low carrier frequency f1, or may be corrected by reducing the reduction width, and may be set appropriately according to the application. it can.

  The carrier frequency setting means 80 is a means for the operator of the processing machine to set the carrier frequency. As described above, in the inverter device according to the present embodiment, the carrier generating means 70 automatically sets an appropriate carrier frequency based on the driving conditions, but the driver sets the carrier frequency according to the driving situation. It is configured so that it can be set manually. The carrier frequency setting means 80 may be configured as various means as long as the driver can set the carrier frequency. For example, the carrier frequency setting means 80 may be displayed as a menu screen on the display. For example, if each process and a carrier frequency option that can be set are displayed, the driver can easily set the carrier frequency for each process only by selecting a menu.

  The carrier frequency can be set by the driver, for example, so that the driver can turn on / off the low carrier frequency mode, and further select the strength of the low carrier frequency mode as necessary. It is preferable to do. Such switching of the low carrier frequency mode by the driver can be performed for each process. Further, the selection of the strength of the low carrier frequency mode may be performed for each process. For example, in the case of the carrier generating means 70, even when the normal mode is set, it is possible to set the low carrier frequency mode by determining that the driver needs attention from the degree of deterioration of the parts. is there. In addition, even in the low carrier frequency mode, if the switching frequency can be set, it is possible to set a more appropriate carrier frequency when the driver knows the degree of component deterioration and process operation status. It can be performed. As described above, when the driver wants to change the carrier frequency setting by looking at the process status or the like, if the carrier frequency setting means 80 can set the carrier frequency, the load on the power module 20 can be reduced. In consideration of the above, it is possible to perform processing with a very high degree of flexibility.

  The controller 90 is a means for giving a voltage command to the PWM signal generating means 100. In FIG. 1, an example of a voltage command is shown as a voltage command signal R. With this voltage command, the duty ratio of the PWM signal is determined.

  The PWM signal generation means 100 is means for generating a PWM signal and supplying it to the power module 20 to drive the power module 20. The PWM signal generating means 100 generates a PWM signal S by PWM modulation based on the voltage command signal R and the carrier signal Q. At this time, the carrier frequency is reflected, and in the region of the low carrier frequency f1, a PWM signal with a long drive interval of the motor 10 is output. Then, by outputting the PWM signal S to the power module 20 according to the output command from the controller 90, the power module 20 drives the motor 10 according to the PWM signal. When the motor 10 requires high responsiveness, the power module 20 is also driven at high speed switching. On the other hand, when the motor 10 is sufficient for low speed rotation, the power module 20 is driven at low speed switching, and the power module 20 is unnecessary. Consumption can be reduced.

  Next, a specific example of changing the carrier frequency will be described with reference to FIG. FIG. 3 is a diagram showing an example of changes in the operating conditions of the injection motor and the mold opening / closing motor and changes in the carrier frequency setting in the injection molding process. FIG. 3A is a diagram showing an example of the carrier frequency of the injection motor, and FIG. 3B is a diagram showing an example of the steps of the injection unit. FIG. 3C is a diagram showing an example of the mold opening / closing unit, and FIG. 3D is a diagram showing an example of the carrier frequency of the mold opening / closing motor. The horizontal axis indicates time t, and the vertical axis indicates carrier frequency f. Further, the carrier frequency f is shown in a relationship of f1 <f2 <f3 <fn.

  First, in the resting state from time t0, both the injection motor and the mold opening / closing motor maintain the low carrier frequency f1 with the mold opened. After the carrier frequency of the mold opening / closing motor increases at time t1 and reaches the normal frequency fn, the mold closing process starts at time t2. During this time, until the time t3, the carrier frequency of the mold opening / closing motor is kept at the normal frequency fn, and the carrier frequency of the injection motor is kept at the low carrier frequency f1. Until time t4, the carrier frequency of the mold opening / closing motor decreases to the low carrier frequency f3, and the carrier frequency of the injection motor increases to the normal frequency fn.

  At time t4, the injection unit enters the injection process, and the mold opening / closing unit enters the mold clamping process. In the injection process of the injection unit, the carrier frequency of the injection motor is kept at the normal frequency fn. In the mold opening / closing motor of the mold opening / closing unit, the carrier frequency f3 is maintained at a low carrier frequency f3, which is one step lower than the normal frequency fn.

  When the injection process ends at time t5, the carrier frequency of the injection motor decreases from the normal frequency fn to the low carrier frequency f2. In the mold opening / closing motor, the one-step frequency is further lowered to a low carrier frequency f2.

  From time t6, the injection unit enters the pressure holding process, but in the pressure holding process, the injection motor does not require high responsiveness and falls to the low carrier frequency f2. In the mold opening / closing unit, the mold clamping process is maintained, and the mold opening / closing motor is maintained at the low carrier frequency f2.

  Although the pressure holding process ends at time t7, the injection motor continues to be in a state that does not require high responsiveness, and the low carrier frequency f2 is maintained as it is. On the other hand, in the mold opening / closing unit, the mold clamping process continues, but the mold opening / closing motor further changes to the low carrier frequency f1 until time t8. This is because the clamping process is continued from time t4, so that the clamping force does not decrease even if the mold clamping process is gradually shifted to the lower frequency side.

  From time t8, the injection unit enters the weighing process, but the injection motor maintains the low carrier frequency f2. In the mold opening / closing unit, the mold clamping process continues, but the mold opening / closing motor maintains the low carrier frequency f1.

  At time t9, the light weight process of the injection unit and the mold clamping process of the mold opening / closing unit are completed. Here, the injection motor starts to decrease and reaches the low carrier frequency f1 at time t10, and the mold opening / closing motor starts to increase and reaches the normal frequency fn at time t10.

  At time t10, since the injection unit has completed a series of steps, the injection motor has a low carrier frequency f1. On the other hand, the mold opening / closing unit starts the mold opening process, and the mold opening / closing motor normally has the carrier frequency fn.

  The mold opening process ends at time t11, and the carrier frequency of the mold opening / closing motor starts to decrease. At time t12, the mold opening / closing motor becomes the low carrier frequency f2. Then, from time t12, the ejecting process is performed in the state of the low carrier frequency f2, and the series of processes for the mold opening / closing unit is also completed.

  In this way, by changing the carrier frequency of the PWM modulation method according to the operating conditions required by the process, it is possible to appropriately control the driving of the processing process while reducing the consumption of the power module 20. Further, as shown in FIG. 3, by setting the low carrier frequencies f1 to f3 in a plurality of stages, it is possible to reduce more appropriate control and the switching load of the power module 20.

  In addition, the setting for each process of the low carrier frequencies f1 to f3 in FIG. 3 may be able to use both the automatic setting of the carrier frequencies f1 to f3 by the carrier generating means 70 and the manual setting by the driver. Also, in the example shown in FIG. 3, the carrier frequency for each set operating condition may be corrected as appropriate based on the temperature information detected by the temperature detecting means 30.

  Thus, according to the inverter device according to the present embodiment, flexible and appropriate drive control is possible, and the life of the power module 20 can be extended while performing appropriate control.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  The present invention can be used for all devices that are driven by a servo motor, such as an injection molding machine, a stacker, etc., and that have operating conditions that generate a large torque at a low speed.

DESCRIPTION OF SYMBOLS 10 Motor 20 Power module 30 Temperature detection means 40 Smoothing capacitor 50 Converter part 60 Three-phase alternating current power supply 70 Carrier generation means 71 Correction means 80 Carrier frequency setting means 90 Controller 100 PWM signal generation means

Claims (7)

An inverter device that drives a motor for a processing machine under a plurality of operating conditions by a power module using a PWM modulation method,
An inverter device comprising carrier generation means for setting a carrier frequency pattern of the PWM modulation method corresponding to the plurality of operating conditions. The carrier frequency pattern has a normal mode of a normal frequency and a low carrier frequency mode of a frequency lower than the normal mode,
The inverter device according to claim 1, wherein the normal mode and the low carrier frequency mode can be selected according to the plurality of operating conditions.   The inverter apparatus according to claim 2, wherein the low carrier frequency mode has a multi-stage mode. Temperature information detecting means for detecting temperature information related to the temperature of the power module;
4. The inverter device according to claim 1, further comprising a correcting unit that corrects the carrier frequency based on temperature information detected by the temperature information detecting unit. 5.   The inverter apparatus according to claim 4, wherein the correction by the correction unit is correction for changing the carrier frequency to a low frequency side.   The inverter device according to claim 1, wherein the operating condition is a condition determined according to a process.   The inverter device according to claim 6, wherein the carrier frequency pattern is switched in mode based on a process switching timing.

Images