JP2014222967A - Servo device and industrial machine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter capable of suppressing thermal fluctuations of a power module.SOLUTION: A servo device 2 controls a position of an object according to a predetermined sequence. A controller 10 generates a position instruction value POS_REF that instructs a position having a predetermined waveform; and also generates a mode control signal MODE synchronized with the position instruction value POS_REF. A power converter 12 including a power module 224 can switch between a first mode that is normal and a second mode that can suppress an increase in the temperature of the power module, according to the mode control signal MODE. The power converter 12 drives a motor 14 so as to match a position detection value POS_FR with the position instruction value POS_REF.

Description

  The present invention relates to a servo device.

  A servo press machine, an injection molding machine, or various stages have a servo device that positions an object based on feedback control. Such a servo device includes an AC motor that converts an electric signal into a linear motion or a rotary motion, and a power converter (inverter) for driving the AC motor.

  The power converter is mainly based on a plurality of switching elements provided for each phase of the AC motor, a controller that generates a control signal modulated according to the target torque (or rotation speed) of the AC motor, and the control signal. A driver for driving the plurality of switching elements.

JP 2007-288858 A JP 2004-48885 A

  Servo press machines, injection molding machines, or electric motors used for various stages have their generated torque dynamically fluctuating depending on the state of the load. Therefore, the current flowing through the switching element of the power conversion device that drives it also dynamically varies depending on the state of the load.

  In general, a power module such as an IGBT (Insulated Gate Bipolar Transistor) is used as a switching element in a large-capacity power conversion device.

  In the power module, thermal fluctuations occur according to the current flowing through it. Since the materials such as solder, wiring, and board in the power module have different thermal expansion coefficients, thermal stress (stress strain) is generated in accordance with the temperature variation of the power module. Thermal stress causes solder cracks and affects the reliability of the power module. Such life of the power module due to thermal stress is referred to as power cycle life.

  In order to operate the servo device without maintenance for a long time, it is necessary to extend the power cycle life, and for that purpose, it is desired to suppress the thermal fluctuation generated in the power module.

  This invention is made | formed in view of this subject, and one of the exemplary objectives of the aspect exists in provision of the power converter device which can suppress the thermal fluctuation of a power module.

  One embodiment of the present invention relates to a servo device that controls the position of an object according to a predetermined sequence. The servo device includes a motor, a power conversion device, and a controller. The power conversion device includes a power module, drives the motor so that the position detection value corresponding to the current position matches the position command value, and at least suppresses the temperature increase of the normal first mode and the power module. The possible second mode is configured to be switchable. The controller generates a position command value having a predetermined waveform. The power converter can be switched between the first mode and the second mode in a predetermined pattern synchronized with the position command value.

  In a servo device in which the waveform of the position command value is determined in advance, the current flowing through the power module changes according to a predetermined waveform in synchronization with the position command value. According to this aspect, in the open loop synchronized with the position command value, the first mode is set when the current (that is, the amount of heat generation) is small, and the second mode is set when the current is large, thereby suppressing the thermal fluctuation of the power module. it can.

  The power converter may be switched in accordance with a mode control signal that indicates the mode of the power converter.

  The motor may be a three-phase motor. The power conversion device may be configured to drive the motor by three-phase modulation in the first mode and to drive the motor by two-phase modulation in the second mode.

  In an aspect, the power conversion device may include a cooling fan for cooling the power conversion device itself. The number of rotations of the cooling fan may be different between the first mode and the second mode.

  The controller receives the input of the position command value waveform from the user, and the second step of outputting the input position command value waveform to the power converter with the mode control signal fixed to the initial value. In the second step, a third step of measuring a current waveform flowing in the power module of the power conversion device and a fourth step of generating a mode control signal pattern based on the current waveform may be executed. .

  In the fourth step, the controller may generate the mode control signal so that the first mode is set when the current waveform is smaller than a predetermined threshold value, and the second mode is set when the current waveform is larger.

  The controller receives the input of the position command value waveform from the user, and the second step of outputting the input position command value waveform to the power converter with the mode control signal fixed to the initial value. In the second step, the third step of measuring the temperature waveform of the power module of the power conversion device and the fourth step of generating the mode control signal pattern based on the temperature waveform may be executed. Good.

  In the fourth step, the controller may generate the mode control signal so that the first mode is set when the temperature waveform is smaller than a predetermined threshold value, and the second mode is set when the temperature waveform is larger.

  Another aspect of the present invention relates to an industrial machine. The industrial machine may include any one of the servo devices described above.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, the thermal fluctuation of the power module can be suppressed.

It is a block diagram which shows an industrial machine provided with the servo apparatus which concerns on embodiment. 2A and 2B are a front view and a side view of a servo press machine that is an industrial machine. It is a wave form diagram which shows operation | movement of the servo press machine of FIG. 4A to 4C are flowcharts showing a method for generating the mode control signal MODE. It is a wave form diagram which shows operation | movement of an XY stage.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected to each other in addition to the case where the member A and the member B are physically directly connected. It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  FIG. 1 is a block diagram illustrating an industrial machine 100 including a servo device 2 according to an embodiment. Examples of the industrial machine 100 include a servo press machine, an injection molding machine, and various stages (for example, an XY stage for wafer conveyance used in a semiconductor manufacturing process). The servo device 2 used in the industrial machine 100 displaces the target object once or a plurality of times according to a predetermined sequence.

  The servo device 2 includes a controller 10, a power conversion device 12, a motor 14, and a load 16.

  The motor 14 is a rotary motor or a linear motor, and transmits power to the load 16. In the present embodiment, the motor 14 is a three-phase motor. In the servo press machine or the injection molding machine, the load 16 may include a combination of a crank mechanism that converts rotational motion into linear motion and a piston. Alternatively, the load 16 may include a stage controlled by a linear motor.

  The controller 10 controls the servo device 2 as a whole. Specifically, the controller 10 generates a position command value POS_REF indicating the target position of the object. This position command value POS_REF has a waveform predetermined according to the operation sequence of the servo device 2.

  The controller 10 generates a mode control signal MODE synchronized with the position command value POS_REF. The mode control signal MODE will be described later.

  The power conversion device 12 includes a power module 222. The power converter 12 feedback-controls the motor 14 so that the position detection value POS_FB corresponding to the current position matches the position command value POS_REF. The power conversion device 12 has a mode control signal MODE from the controller 10 in at least two modes: a normal first mode and a second mode in which the temperature increase of the power module 222 can be suppressed as compared with the first mode. It can be switched according to.

  In the present embodiment, the motor 14 is a three-phase motor, and the power conversion device 12 drives the motor 14 with three-phase modulation in the first mode, and drives the motor 14 with two-phase modulation in the second mode. From this point of view, the first mode and the second mode have a relationship that the second mode has lower power consumption and the first mode has better controllability.

  The power converter 12 includes a torque command value generator 203, a pulse modulator 210, gate drive circuits 222U to 222W, and power modules 224U to 224W.

  The torque command value generation unit 203 receives the position command value POS_REF from the controller 10 and generates a torque command value S1 corresponding thereto. The configuration of the torque command value generation unit 203 is not particularly limited. For example, the torque command value generation unit 203 includes a subtracter 204 and a PI (proportional / integration) control unit 206. A position detection signal POS_FB indicating the current position (displacement amount) of the load 16 is fed back to the subtractor 204. The subtracter 204 calculates a deviation between the position command value POS_REF and the position detection value POS_FB. The PI control unit 206 receives the deviation and outputs a torque command value S1 whose value is controlled so that the deviation becomes zero. Instead of PI control, P control, PID control, or the like may be used.

  Each of the power modules 224U to 224W includes an upper arm and a lower arm, and is composed of, for example, an IGBT or an FET. The gate drive circuits 222U to 222W switch the corresponding power modules 224U to 224W according to the drive signal S2 from the pulse modulator 210, respectively.

  The pulse modulator 210 generates a drive signal S2 that is pulse-modulated according to the torque command value S1. As a result, the power converter 12 supplies power corresponding to the torque command value S1 to the motor 14.

  For example, the pulse modulator 210 generates the drive signal S2_1 by three-phase modulation in the first mode, and generates the drive signal S2_2 by two-phase modulation in the second mode.

  Two-phase modulation is inferior in terms of controllability, responsiveness, and quietness compared to three-phase modulation. However, since the switching frequency of the inverter switching element is small, switching loss is small and energy saving is excellent. Therefore, by switching the modulation method, it is possible to switch between the first mode in which controllability is prioritized and the second mode in which suppression of the heat generation amount of the power module 224 is prioritized.

  Further, the power conversion device 12 includes a cooling fan 226. The rotational speed of the cooling fan 226 is different between the first mode and the second mode. Specifically, the rotational speed of the second mode is set higher than that of the first mode. In the first mode, the rotational speed of the cooling fan 226 may be zero, that is, the cooling fan 226 may be stopped.

  In the second mode, the power module 224 is strongly cooled by increasing the number of rotations of the cooling fan 226, so that the temperature rise of the power module 224 is suppressed as compared to the first mode. On the contrary, in the first mode, the power consumption of the cooling fan 226 and thus the entire servo device 2 can be reduced by reducing the rotational speed of the cooling fan 226.

  The mode control unit 260 switches the operation mode of the power converter 12, that is, the operation mode of each of the pulse modulator 210 and the cooling fan 226, according to the mode control signal MODE from the controller 10.

  Next, the mode control signal MODE will be described.

  As described above, in the press operation in the servo press machine and the mold clamping operation of the injection molding machine, a predetermined operation sequence is executed. Therefore, the position command value POS_REF generated by the controller 10 has a predetermined waveform. Have. Even in the XY stage used in the semiconductor manufacturing process, the wafer is repeatedly transported along the same path, so that the position command value POS_REF has a predetermined waveform. The waveform of the position command value POS_REF is defined by the user of the servo device 2 according to its use.

  In such a situation, when the motor 14 is driven according to the position command value POS_REF according to a certain sequence, the heat generation amount of the power module 224 has a predetermined waveform. That is, the waveform of the position command value POS_REF for one cycle and the temperature waveform of the power module 224 can be associated with each other at 1: 1. The controller 10 instructs the first mode when the amount of heat generated by the power module 224 is relatively small, and instructs the second mode when the amount of heat generated by the power module 224 is relatively large.

  The above is the configuration of the industrial machine 100 including the servo device 2.

  Next, a specific configuration example and operation of the industrial machine 100 will be described.

  2A and 2B are a front view and a side view of a servo press machine (forging press machine) that is the industrial machine 100. FIG.

  Closed forging is a method in which an upper and lower mold and a punch are used, the upper and lower molds are clamped to confine the material in the mold space, and then the punch is pushed into the material to fill the mold space. A double-action forging press is used for the closed forging, and the upper and lower molds and the punch are pressed at different timings by a plurality of pressurizing devices.

  Forging presses include mechanical types such as a connecting rod type, a knuckle type, and a link type. As shown in FIGS. 21A and 21B, a general connecting rod press uses an eccentric shaft 801 and a connecting rod 802 that is rotatably fitted in an eccentric portion of the eccentric shaft 801, and is connected to the lower end of the connecting rod 802. The slide 803 has a structure that is swingably attached. For this reason, when the eccentric shaft 801 is rotated, the connecting rod 802 swings and the slide 803 can be moved up and down.

  Since mechanical presses such as connecting rod presses can be slid by simple rotational and linear motions, they can be operated at higher speeds and higher accuracy than hydraulic presses.

  In the forging press machine, a drive mechanism such as a servo motor is connected to the eccentric shaft 801 via a speed reducer or the like. The load 16 in FIG. 1 corresponds to the eccentric shaft 801, the connecting rod 802, the slide 803, and the speed reducer (not shown) in FIGS. 21 (a) and 21 (b).

  FIG. 3 is a waveform diagram showing the operation of the servo press machine of FIG. The position command value POS_REF indicates the rotation angle (0 to 360 °) of the eccentric shaft 801. For example, POS_REF = 0 ° (360 °) corresponds to a state in which the slide 803 is pulled up most, and POS_REF = 180 ° corresponds to a state in which the slide 803 is pushed down most.

For example, in a press machine, the controller 10 repeatedly generates a position command value POS_REF having a waveform as shown in FIG. Since the state of POS_REF = 180 ° corresponds to the press operation, the generated torque of the motor 14 is the highest. Therefore, current _I PM flowing in the power module 224 become large when POS_REF = 180 °, thus heating value of the power module 224 is at this time becomes maximum.

  Therefore, the controller 10 generates the mode control signal MODE in an open loop in synchronization with the position command value POS_REF. Specifically, the amount of heat generated by the power module 224 is determined according to the position command value POS_REF at each time, and the mode for each time (in other words, the value of the position command value) is determined according to the amount of heat generated. It is done. In the example of FIG. 3, the second mode is set in the state φ2 during the press operation, and the first mode is set in the other state φ1.

The above is the operation of the servo press.
According to the servo device 2 according to the embodiment, the heat generation of the power module 224 is performed by open loop control based on the position command value without detecting the temperature of the power module 224 or the current flowing through the power module 224 during the operation. Control the amount.
In feedback control (closed loop control) with temperature and current detection as disclosed in the prior art, a response delay due to the feedback loop occurs. Due to this delay in response, the power module 224 operates in the first mode during the period in which it should originally operate in the second mode. As a result, the power module 224 rises to an unintended temperature. There is a possibility of operating in two modes, thereby degrading the control characteristics.

  According to the servo device 2 according to the embodiment, it is possible to control the heat generation amount of the power module 224 without being affected by the response delay of the feedback loop, and to suppress the thermal fluctuation. Thereby, the power cycle life of the power module 224 can be extended, and the servo device 2 can be operated without maintenance for a long time.

  Next, a method for generating the mode control signal MODE by the controller 10 will be described. 4A to 4C are flowcharts showing a method for generating the mode control signal MODE.

(First generation method)
FIG. 4A shows a first generation method of the mode control signal MODE.
The controller 10 receives an input of a waveform of the position command value POS_REF from the user (S100).
Subsequently, in a state where the mode control signal MODE is fixed to the initial value (first mode), the waveform of the input position command value POS_REF is output to the power conversion device 12, and the servo device 2 is temporarily operated (S102). .
Then, to measure the current waveform _{I PM} flowing in the power module 224 of the power converter 12 at this time (S104).
Then, based on the current waveform _{I PM,} to determine the pattern of the mode control signal MODE (S106). For example, the controller 10 compares the current waveform I _PM with a predetermined threshold value I _TH and sets the first mode when I _PM <I _TH and sets the second mode when I _PM > I _TH .

(Second generation method)
FIG. 4B shows a second generation method of the mode control signal MODE.
The controller 10 receives an input of a waveform of the position command value POS_REF from the user (S200).
Subsequently, in a state where the mode control signal MODE is fixed to the initial value (first mode), the waveform of the input position command value POS_REF is output to the power converter 12, and the power converter 12 is operated (S202).
Subsequently, at this time, the temperature T _PM of the power module 224 of the power converter 12 is measured (S204).
And based on the temperature of the waveform _{T PM,} to determine the pattern of the mode control signal MODE (S206). For example, the controller 10 compares the temperature waveform T _PM with a predetermined threshold value T _TH and sets the first mode when T _PM <T _TH and sets the second mode when T _PM > T _TH .

(Third generation method)
FIG. 4C shows a third generation method of the mode control signal MODE.
The controller 10 receives an input of a waveform of the position command value POS_REF from the user (S300).

Controller 10, from the waveform of the position command value POS_REF, to calculate the waveform of the current _{I PM} flowing in the power module 224. Characteristics of the motor 14, if the structure of the load 16 is known, it is possible to calculate the current _{I PM} from the waveform of the position command value POS_REF (S302).

The controller 10, based on the calculated current waveform _{I PM,} to determine the pattern of the mode control signal MODE (S304). For example, the controller 10 compares the current waveform I _PM with a predetermined threshold value I _TH and sets the first mode when I _PM <I _TH and sets the second mode when I _PM > I _TH .

Alternatively, the controller 10 determines three parameters of a reduction rate k, a current threshold value I _TH2 , and a load threshold value Load _TH , and sequentially calculates the load Load _i in each cycle i according to equations (1) and (2). The first mode may be set when Load _i <Load _TH , and the second mode may be set when Load _i > Load _TH .
When I _PM > I _TH2 , Load _{i + 1} = Load _i + (I _PM −I _TH2 ) ² (1)
When I _PM <I _TH2 , Load _{i + 1} = Load _i −k (I _PM −I _TH2 ) ² (2)
Note that equation (1) describes the overheating state and equation (2) describes the cooling state, but even if (I _PM −I _TH2 ) is the same value, the temperature change width may differ between overheating and cooling. is assumed. Therefore, in a system where the cooling efficiency is equal to the superheat efficiency, the reduction rate k is set to 1, and in a system where the cooling efficiency is lower than the superheat efficiency, the value is set to an appropriate value (<k), so that the system is overheated and cooled. It becomes possible to describe the process more accurately.

  According to the servo device 2 according to the embodiment, when the user inputs the waveform of the position command value POS_REF, the controller 10 can automatically generate the mode control signal MODE according to the waveform.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way. Hereinafter, such modifications will be described.

(Modification 1)
In the embodiments, the case where the modulation mode control and the cooling fan rotation speed control are used in combination in the first mode and the second mode has been described, but only one of them may be used. That is, the rotation speed of the cooling fan may be fixed regardless of the mode. Alternatively, the modulation method may be fixed regardless of the mode.

(Modification 2)
Depending on the mode, the modulation frequency (carrier frequency) may be controlled instead of or in addition to controlling the modulation method. When the modulation frequency is lowered, the control characteristic is lowered, but the power consumption is reduced. Therefore, by setting the frequency of the second mode to be lower than the modulation frequency of the first mode, the same effect as in the embodiment can be obtained.

(Modification 3)
Alternatively, in addition to the first mode and the second mode, another mode may be prepared and three or more modes may be switched.

(Modification 4)
In the embodiment, the servo press machine has been described for the operation of the industrial machine 100, but the present invention is not limited thereto. For example, in the case of an injection molding machine, mode control may be performed similarly to the servo press machine.

(Modification 5)
As described above, the industrial machine 100 may be a stage. FIG. 5 is a waveform diagram showing the operation of the XY stage. The position command value POS_REF indicates the coordinates of the stage in the X direction.

  In the case of the XY stage, a large current flows through the power module when the stage is accelerated or decelerated. Therefore, the mode may be switched according to the timing of acceleration and deceleration. Even in the case of the stage, the mode control signal MODE can be generated in accordance with the flowcharts of FIGS.

(Modification 6)
In the embodiment, the case has been described in which the controller 10 generates a position command value (position control) and a mode control signal (mode control), but the present invention is not limited to this. For example, the mode control unit 260 of the power converter 12 may receive the position command value POS_REF, generate the mode control signal MODE based on the position command value POS_REF, and switch the mode. In this case, the mode control unit 260 may include a table that associates the position command value POS_REF with the mode control signal MODE, or may include a calculation unit that calculates the mode control signal MODE from the position command value POS_REF.

2 ... Servo device, 10 ... Controller, 12 ... Power converter, 14 ... Motor, 16 ... Load, 4 ... Controller, 202 ... Controller, 203 ... Torque command value generation unit, 204 ... Subtractor, 206 ... PI control unit, DESCRIPTION OF SYMBOLS 210 ... Pulse modulator, 220 ... Inverter, 222 ... Gate drive circuit, 224 ... Power module, 226 ... Cooling fan, 260 ... Mode control part, 100 ... Industrial machine.

Claims (10)

A servo device for controlling the position of an object according to a predetermined sequence,
A motor,
A controller that generates a position command value having a predetermined waveform;
The power module is included, and the motor is driven so that the position detection value corresponding to the current position matches the position command value, and at least the normal first mode and the temperature increase of the power module can be suppressed. A power converter capable of switching between two modes and switching between a first mode and a second mode in a predetermined pattern synchronized with a position command value;
A servo device comprising:   The servo apparatus according to claim 1, wherein the power converter is switched according to a mode control signal that indicates a mode of the power converter. The motor is a three-phase motor;
The power converter is configured to drive a motor by three-phase modulation in the first mode and to drive a motor by two-phase modulation in the second mode. The servo device described. The power conversion device includes a cooling fan for cooling the power conversion device itself,
4. The servo device according to claim 1, wherein the number of rotations of the cooling fan differs between the first mode and the second mode. 5. The controller is
A first step of receiving an input of a waveform of the position command value from a user;
A second step of outputting a waveform of the input position command value to the power conversion device in a state in which a mode control signal instructing a mode of the power conversion device is fixed to an initial value;
In the second step, a third step of measuring a current waveform flowing in the power module of the power converter,
A fourth step of generating a pattern of the mode control signal based on the current waveform;
The servo device according to claim 1, wherein the servo device is executed.   In the fourth step, the controller generates the mode control signal so that the first mode is set when the current waveform is smaller than a predetermined threshold value, and the second mode is set when the current waveform is larger. The servo device according to claim 5. The controller is
A first step of receiving an input of a waveform of the position command value from a user;
A second step of outputting a waveform of the input position command value to the power conversion device in a state in which a mode control signal instructing a mode of the power conversion device is fixed to an initial value;
In the second step, a third step of measuring a temperature waveform of the power module of the power converter,
A fourth step of generating a mode control signal pattern based on the temperature waveform;
The servo device according to claim 1, wherein the servo device is executed.   In the fourth step, the controller generates the mode control signal so that the first mode is set when the temperature waveform is smaller than a predetermined threshold value, and the second mode is set when the temperature waveform is larger. The servo device according to claim 7. The controller is
A first step of receiving an input of a waveform of the position command value from a user;
A second step of calculating a current waveform that will flow through the power module when the servo device is operated based on the position command value;
A third step of generating a mode control signal pattern for instructing a mode of the power converter based on the current waveform;
The servo device according to claim 1, wherein the servo device is executed.   An industrial machine comprising the servo device according to claim 1.

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