JP2014149406A - Galvano scanner control device, and laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the ratio of eddy current loss to power consumption increases because a galvano scanner repeatedly performs the positioning at different distances, a prediction result can differ from an actual temperature in a conventional method of estimating the permanent magnet temperature at a single frequency, and hence the temperature of the permanent magnet increases to reduce the generation torque to reduce the positioning accuracy.SOLUTION: The galvano scanner control device includes: temperature estimating means 209 for estimating, using calorific power of each of a rotator and stator, the temperature of the permanent magnet before start of positioning (current time) and after the completion of the positioning; and operation amount compensating means 210 for compensating the operation amount of a galvano scanner on the basis of the estimated difference between the permanent magnet temperature at the current time and that after the completion of the positioning.

Description

  The present invention relates to a galvano scanner control device that controls a galvano mirror so as to follow a specified target value, and a laser processing apparatus that uses such a galvano scanner control device.

  For example, a printed wiring board drilling laser processing apparatus, which is an example of an apparatus having a galvanometer mirror that deflects laser light, is used for mounting a semiconductor element or the like on a printed wiring board and electrical coupling between layers using a laser light. It is a device that drills holes.

  FIG. 2 is a block diagram showing the configuration of a galvano mirror control mechanism in a conventional laser processing apparatus. Here, for example, a galvano scanner control device using terminal state control described in Non-Patent Document 1 will be taken up. When irradiating a laser beam to an arbitrary position of the workpiece, first, the host controller 201 sends the galvano scanner angle command data 101 calculated from the hole position coordinates described in the NC program to the galvano scanner controller 20. .

  In the galvano scanner control device 20, the torque command generation unit 202 generates a torque command signal 103 by multiplying the torque command coordinate sequence 102 calculated in advance and stored in the storage unit 203 by a magnification corresponding to the movement angle. The torque command coordinate sequence 102 is generally prepared in advance with a plurality of coordinate sequences having different positioning times, and the torque command coordinate sequence 102 to be used is selected according to the movement angle. Several methods for creating a torque command for a galvano scanner have been proposed. For example, there is terminal state control. The torque command signal 103 enters the digital filter 204 that simulates the mechanical vibration characteristics of the galvano scanner, and is given to the feedback loop as the target angle 104 for each control cycle. The follow-up error 105 obtained by subtracting the swing angle of the galvano scanner from the target angle 104 is subjected to control calculation processing by the compensation element 205 and then the other torque command signal 103 is added to become an operation amount 106. The manipulated variable 106 is sent to the D / A converter 206 and becomes an analog signal (galvano scanner current command value 107). The current command signal is amplified by the amplifier 60 and applied to the electric swing actuator unit of the galvano scanner 30 as the drive current 108, and the swing shaft rotates. At this time, the swing angle is detected by an angle detector (not shown) and output as a swing angle signal 109. Further, the pulse counter 207 converts the signal again into an output pulse signal 110 which is a digital signal and feeds it back. By repeating these processes, the galvanometer mirror gradually approaches the target angle. After reaching the target angle, the laser beam is irradiated and drilling is performed. In the laser processing apparatus, the positioning operation and the laser beam irradiation are repeated.

  FIG. 3 is a sectional view of a general moving magnet type galvano scanner. The galvano scanner has a magnetic circuit composed of permanent magnets 306a and 306b, coils 305a and 305b, and yokes (silicon steel plates) 304a and 304b. The stator side includes a casing 303, yokes 304a and 304b, and coils 305a and 305b. The mover includes a swing shaft 300, permanent magnets 306a and 306b, a galvanometer mirror 50, a galvanometer mirror holder 301, and a scale of an angle detector. 307. The casing 303 is kept at a constant temperature by a water cooling jacket (not shown). The permanent magnets 306a and 306b are bonded to the swing shaft 300, and a force (Lorentz force) generated by a magnet and a coil to which a current is applied is applied to the swing shaft 300, and the swing shaft 300 rotates. The swing shaft 300 is rotatably fixed to the stator side through a pair of bearings 302a and 302b, and a galvano mirror 50 is connected to one end of the swing shaft 300 through a galvano mirror holding portion 301. An angle detector scale 307 for detecting a rotation angle is attached to the other end. The angle detector includes a scale 307 and sensor units 308a and 308b.

  In recent years, with the progress of high integration of electrical products, the diameter of holes processed in a printed circuit board tends to be reduced. In order to reduce the laser spot diameter d, it is known that the original laser diameter D, the laser wavelength λ, and the focal length of the condenser lens are represented by the following equation.

  That is, in order to process a small-diameter hole, it is necessary to increase the diameter of the laser, and accordingly, it is necessary to increase the size of the galvanometer mirror or the like. A large torque is required to swing the large galvanometer mirror, and the drive current also increases. Therefore, the coil and the permanent magnet are heated by Joule heat generated in the coil, and the temperature rises. Further, the speed of drilling holes is increasing year by year to improve the processing throughput, but the larger the galvanometer mirror is moved, the greater the heat generated. As the heat is generated, the temperature of the permanent magnet rises, and the magnetic force of the permanent magnet is lowered, resulting in a decrease in torque. A decrease in the generated torque causes a decrease in controllability, and the positioning accuracy deteriorates. In order to avoid such a problem, there is a galvano scanner in which the heat generation of the coil is averaged by adjusting the processing order (Patent Document 1).

  Moreover, in the electric motor of a hybrid vehicle, there is an electric motor control device that estimates the permanent magnet temperature from the driving state such as the rotation speed of the electric motor and sets a driving limit (Patent Document 2).

JP 2003-329960 A JP 2008-199738 A

Hirata, et al .: “Nanoscale servo control of galvano scanner by terminal state control”, D. D, 119, 9, pp. 938-944, 2009

  In general, a galvano scanner that performs positioning repeatedly at different distances is different from a general electric motor that rotates at a constant rotation speed, so that the driving current does not excite vibrations generated by a galvanometer mirror during positioning. A torque command coordinate sequence is created, and the torque command is composed of a plurality of frequency components. Further, since the positioning time is very short, the drive current often includes a frequency component of 1 kHz or more. For this reason, since the ratio of eddy current loss to the power consumption (≈ calorific value) increases, the influence of the eddy current loss of the permanent magnet is simple in the conventional method of predicting the permanent magnet temperature from the magnitude of the drive current and the rotation speed of the motor. Since the frequency is considered at one frequency, when the high-speed positioning is repeated with the galvano scanner, the actual temperature may be different from the predicted result. Therefore, there has been a problem that the temperature of the permanent magnet is raised, the generated torque is lowered, and the positioning accuracy is deteriorated.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a galvano scanner control device and a laser processing device that have a short positioning time and excellent positioning accuracy.

  As a means for solving the above-mentioned problem, a torque command coordinate sequence (102) stored in the first storage unit (203) is obtained by using a galvano scanner having a feedback loop and having a rotor to which a permanent magnet is attached. In the galvano scanner control device that uses the torque command generation unit (202) to generate the torque command value (103) and positions the galvanometer mirror,

  Temperature estimation means (209) for estimating the temperature of the permanent magnet before starting positioning (current time) and at the end of positioning, using the respective calorific values of the rotor and stator, and the estimated current time and at the end of positioning It is preferable to use a galvano scanner control device comprising an operation amount compensation means (210) for compensating the operation amount of the galvano scanner based on the difference in the permanent magnet temperature.

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not have any influence on description of a claim by this.

  According to the present invention, since the galvanometer mirror can be positioned at high speed and with high accuracy, for example, processing throughput and processing accuracy can be improved.

It is a block diagram of the galvano scanner servo mechanism which comprises the galvano scanner control apparatus which concerns on this invention. It is a block diagram of the galvano scanner servo mechanism which comprises the galvano scanner control apparatus in the conventional laser processing apparatus. It is sectional drawing of the conventional general moving magnet type galvano scanner. It is a schematic diagram which shows the relationship between a frequency and an actual resistance at the time of removing a needle | mover from a galvano scanner and a galvano scanner. It is a schematic diagram showing the relationship between the frequency of a torque command coordinate sequence and a torque command frequency component. It is a figure for demonstrating the thermal model of the galvano scanner which concerns on this invention. It is a flowchart explaining the control method in the galvano scanner control device concerning the present invention. It is an example of the time waveform of the emitted-heat amount of the galvano scanner in the example of processing operation of Example 1 which concerns on this invention, and the estimated coil and permanent magnet temperature. It is an example of the time waveform of the tracking error in Example 1 which concerns on this invention. It is an example of the time waveform of the tracking error in a prior art. It is a block diagram of the galvano scanner servo mechanism which comprises the galvano scanner control apparatus of Example 2 which concerns on this invention. It is a schematic diagram showing the example of the demagnetization curve (BH curve) in a permanent magnet.

  Hereinafter, examples will be described with reference to the drawings.

  FIG. 1 is a block diagram of a galvano scanner servo mechanism constituting a galvano scanner control apparatus according to the present invention. In addition, the thing of the function equivalent to FIG. 2 attaches | subjects the same code | symbol, and abbreviate | omits the overlapping description.

  The present invention includes a second storage unit 208 for storing the amount of heat generated by the coil and the permanent magnet, which is calculated when generating the torque coordinate sequence, and a permanent magnet for estimating the temperature rise of the permanent magnet from the amount of generated heat. A temperature estimation unit 209 and an operation amount compensation unit 210 that compensates the operation amount based on the calculated permanent magnet temperature are provided.

First, a method for calculating the heat generation amount of the coil and the permanent magnet will be described with reference to FIGS. FIG. 4 shows the relationship between the frequency and the actual resistance when a single frequency sine wave is input to the galvano scanner, and is shown together with the measurement result when the mover is removed from the galvano scanner. Although the difference in the measurement results in FIG. 4 is considered to be a loss due to the rotor, it is known from the numerical analysis results that the majority of the loss due to the rotor is the eddy current loss of the permanent magnet in the galvano scanner. . Further, it has been found that the loss on the stator side is mainly due to the copper loss and skin effect of the coil, resulting in a loss in the coil. That is, the frequency f1 in the drawing, the heating value is the loss of the galvanometer scanner, Ra according in Figure _f1: may be distributed to the coil and the permanent magnet in a ratio of Rb _f1.

  FIG. 5 shows the relationship between the frequency and the magnitude of the frequency component when the torque command coordinate sequence is subjected to frequency analysis. Although this embodiment shows a case where a torque command is generated by terminal state control, it can be seen that the torque command coordinate sequence has almost no frequency component in the vicinity of the resonance frequencies f2 and f3 of the structure so as to avoid excitation of structural vibration. . On the other hand, there is a point that the frequency component becomes large at the frequency between f2 and f3.

と表せ、注目する周波数領域ｆｓ〜ｆｅにおけるコイルの発熱量Ｑｃは、

となる。
同様に、ガルバノスキャナの周波数ｆ_１における永久磁石の発熱量Ｑｍ_ｆ１は、図４における周波数ｆ１での実抵抗Ｒｂ_ｆ１と、図５における周波数ｆ１でのトルク指令ゲインＧ_ｆ１より、

と表せ、注目する周波数領域ｆｓ〜ｆｅにおける永久磁石の発熱量Ｑｍは、

となる。よって、式３と式５の結果よりコイルおよび永久磁石の発熱量が求められる。算出された発熱量は、位置決め動作開始前に記憶部２０３に記憶されたトルク指令座標列に対応付けて，第二記憶部２０８に記憶される。 Now, the heat generation amount _{Qc f1} of the coil at the frequency f1 of the galvano scanner, the real resistance _{Ra f1} at the frequency f1 in FIG. 4, from the torque command gain _{G f1} at the frequency f1 in FIG. 5,

The amount of heat generated Qc of the coil in the frequency range fs to fe to be noted is

It becomes.
Similarly, the calorific value _{Qm f1} of the permanent magnets at the frequency _{f 1} of the galvano scanner, the real resistance _{Rb f1} at the frequency f1 in FIG. 4, from the torque command gain _{G f1} at the frequency f1 in FIG. 5,

The calorific value Qm of the permanent magnet in the frequency range of interest fs to fe is

It becomes. Therefore, the calorific values of the coil and the permanent magnet are obtained from the results of Expression 3 and Expression 5. The calculated calorific value is stored in the second storage unit 208 in association with the torque command coordinate sequence stored in the storage unit 203 before starting the positioning operation.

  Next, a method for estimating the permanent magnet temperature will be described. In this embodiment, the lumped constant model shown in FIG. 6 is used to estimate the permanent magnet temperature. In FIG. 6, θm, θc, and Tk are the temperatures of the permanent magnet, the coil, and the casing, respectively, Cm and Cc are the heat capacities of the permanent magnet and the coil, and Kmc and Kck are the heat between the permanent magnet and the coil and between the coil and the casing. Conductivity. The results of measuring the heat capacity and thermal conductivity are shown in Table 1. Note that the thermal conductivity is a lumped parameter model, so there is no length dimension.

なお、θｍ、θｃはそれぞれ時間に対する温度変化量を表す。また、ケーシングが十分に冷却され続け、ケーシング温度Ｔｋが一定である場合を仮定する。 Now, when the relationship between the calorific value, the heat capacity, and the thermal conductivity is arranged, the following equation is established.

Note that θm and θc each represent a temperature change amount with respect to time. Further, it is assumed that the casing continues to be sufficiently cooled and the casing temperature Tk is constant.

  Now, the temperature of the coil and the permanent magnet at a time advanced by a minute time Δ from the current time t can be approximately predicted by the following equation when the minute time Δ is sufficiently small.

  Here, Qc and Qm are the calorific values of the coil and permanent magnet for a minute time Δ. The shortest possible permanent magnet temperature prediction cycle (= minute time Δ) is the control cycle of the galvano control device (generally about several tens of microseconds). Since the constant is sufficiently longer than a single positioning time (several hundred μs to several milliseconds), the positioning time can be used as the minute time Δ. Therefore, in this embodiment, the positioning time is used as the minute time Δ, and when the angular position command data is received, the current time and the temperature prediction at the end of positioning are performed. Therefore, since the positioning time changes according to the movement angle command, the minute time Δ in this embodiment is not constant. Further, the temperature of the coil and the permanent magnet at the time of starting the first positioning operation is assumed to be the same as the casing temperature, and thereafter, the prediction result is sequentially updated using Expression 7. The temperature estimation at the current time is calculated assuming that the state of zero heat generation continues from the final positioning completion time.

  Next, a flowchart of the positioning operation in the present embodiment is shown in FIG. This method is different from the conventional method in that there are a flow (STEP 4 and 5) for predicting the permanent magnet temperature after the end of positioning and a flow (STEP 6) for setting an operation amount compensation value. When the angle command data 101 is received from the host control system 201 by the galvano scanner control device of the present embodiment shown in FIG. 1 (STEP 1), the torque command generation unit 202 stores a plurality of torque command coordinate sequences stored in the storage unit 203. A coordinate sequence for positioning is selected from 102 according to the movement angle, and a torque command signal 103 is created by multiplying the magnification according to the movement angle. The positioning time is determined by the selected coordinate sequence (STEPs 2 and 3). Next, the permanent magnet temperature estimation unit 209 calculates the current time and the permanent magnet temperature at the end of positioning from the heat capacity and thermal conductivity of the coil and permanent magnet stored in the second storage unit, and the amount of heat generated in the torque coordinate sequence. Predict (STEP 3 and 4). Based on the difference between the predicted current time and the permanent magnet temperature at the end of positioning, the reduction rate of the generated torque accompanying the increase in the permanent magnet temperature is predicted, and the reciprocal of the reduction rate is set as the enlargement rate 111 in the operation amount compensation unit. (STEP 6). In this example, 0.12% / W was used as a coefficient of the rate of decrease in torque generated with a temperature increase in a general neodymium magnet.

  The torque command signal 103 enters the digital filter 204 and is given to the feedback loop as the target angle 104 for each control cycle. The follow-up error 105 obtained by subtracting the swing angle of the galvano scanner from the target angle 104 is subjected to control calculation processing by the compensation element 205 and then the other torque command signal 103 is added to become an operation amount 106. The manipulated variable 106 is a corrected manipulated variable 112 that takes into account the decrease in torque generated by the permanent magnet temperature rise in the manipulated variable compensation unit 210, and this corrected manipulated variable 112 is sent to the D / A converter 206 and becomes the current command signal 107. (STEP7). The following operations are as described in the background art.

  FIG. 8 shows an example of the heat generation amount of the galvano scanner, the time waveform of the estimated coil and permanent magnet temperature, and the time waveform of the torque compensation amount (enlargement ratio) in the processing operation example when this embodiment is used. From the figure, the permanent magnet temperature has a much longer time constant than the coil temperature. This is because in the case of a moving magnet type galvano scanner, the permanent magnet is provided on the mover, and there is a gap with poor thermal conductivity between the permanent magnet and the coil or cooling jacket. For this reason, for example, the conventional method in which the coil temperature and the permanent magnet temperature are regarded as the same deteriorates the estimation accuracy. However, the present invention makes it possible to estimate the permanent magnet temperature with high accuracy and sufficiently obtain a compensation effect for the torque drop due to heat generation. It is done. In addition, the temperature is estimated by calculating the amount of heat generated by the coil and permanent magnet based on the power consumption of the galvano scanner, so the positioning time changes in a short time because the movement angle varies, and the drive current has multiple frequency components. Highly accurate estimation is possible even with the permanent magnet temperature during operation of the galvano scanner configured.

  Next, the effect of this invention is demonstrated using FIG. 9, FIG. FIG. 9 shows a time waveform of the deviation obtained by subtracting the swing angle from the target angle according to the present embodiment at times t0, t1, and t2 in FIG. 8, and FIG. 10 is a time waveform of the deviation in the conventional method. is there. As can be seen from the figure, a large overshoot has occurred in the follow-up waveform due to a decrease in the torque generated with the heat generation of the permanent magnet over time, but the overshoot can be suppressed by applying the present invention.

  In this embodiment, in order to reduce the calculation cost, the positioning time determined for each movement angle command is a minute time Δ. However, if the minute time Δ is a control period, the permanent magnet temperature is estimated for each control period. Therefore, the estimation accuracy can be increased.

  FIG. 11 is a block diagram of the galvano scanner control apparatus according to the second embodiment. The torque command generation unit 202 receives the estimated permanent magnet temperature from the permanent magnet temperature estimation unit 209 and the second storage unit 208 from the permanent magnet temperature. The difference is that the torque command limit value 113 is input. In addition, the thing of the function equivalent to FIG. 1 attaches | subjects the same code | symbol, and abbreviate | omits the overlapping description. When the angle command data 101 is received from the host control system 201 by the galvano scanner control device of the present embodiment shown in FIG. 11, the torque command generation unit 202 receives the predicted permanent magnet temperature and the second storage unit from the permanent magnet temperature estimation unit 209. The torque command coordinates for determining the positioning time after obtaining the torque command limit value 113 for the permanent magnet temperature from 208 and positioning in the corresponding positioning time from the torque command coordinate sequence designed in advance and stored in the storage unit 203 A column 102 is selected, and a torque command signal 103 is created by multiplying the coordinate column by a magnification corresponding to the moving angle. Subsequent operations are the same as those in the first embodiment.

  Next, a method for setting the torque command limit value will be described. The reason why a limit value is provided for the magnitude of the torque command is to avoid irreversible thermal demagnetization of the permanent magnet. FIG. 12 shows examples of demagnetization curves (BH curves) at permanent magnet temperatures of 20 ° C. and 160 ° C. When the permanent magnet temperature is 20 ° C., when the external magnetic field H generated by the coil is applied opposite to the magnetization direction of the permanent magnet, the magnetic flux density produced by the coil and the permanent magnet decreases monotonously. On the other hand, in the case of 160 ° C., there is a point a at which the magnetic flux density suddenly decreases, and the permanent magnet that has passed the point a does not recover to the initial magnetization even if it is cooled by an external magnetic field or cooled. If irreversible thermal demagnetization occurs in the permanent magnet used for the rotor, the initial performance of the galvano scanner cannot be exhibited. Therefore, it is desirable to drive the galvano scanner under conditions that do not cause irreversible thermal demagnetization.

  Therefore, in this embodiment, a torque command value serving as a drive current for forming the maximum external magnetic field that does not reach the temperature and nick point in the permanent magnet temperature range at the time of driving is provided as a torque command limit value, and this is stored in the second storage unit. 208 is stored. Then, by making a comparison when the positioning time is determined by the torque command generator 202, it is possible to avoid the occurrence of irreversible heat demagnetization. In addition, when the permanent magnet is at a high temperature, the conventional method stops the positioning operation regardless of the movement angle. However, according to this embodiment, since the drive current is continuously suppressed, the decrease in throughput is minimized. Can be suppressed.

20 Galvano Scanner Control Device 101 Angle Command Data 102 Torque Command Coordinate Sequence 103 Torque Command Signal 104 Target Angle 105 Tracking Error 106 Operation Amount 107 Current Command Signal 108 Drive Current 109 Far Angle Signal 110 Output Pulse Signal 111 Enlargement Ratio 112 Correction Operation Amount 30 Galvano scanner 301 Galvano mirror holding part 302a, 302b Bearing 303 Casing 304a, 304b Yoke 305a, 305c Coil 306a, 306b Permanent magnet 307 Scale 308a, 308b Angle detector (sensor part)
50 Galvano mirror 60 amplifier

Claims (4)

Using a galvano scanner having a feedback loop and having a rotor with a permanent magnet attached, a torque command creation unit creates a torque command value using a torque command coordinate sequence stored in the first storage unit, In the galvano scanner controller that positions the mirror,
Temperature estimation means for estimating the temperature of the permanent magnet before starting positioning (current time) and at the end of positioning, using the respective calorific values of the rotor and stator;
A galvano scanner control device comprising operation amount compensation means for compensating an operation amount of a galvano scanner based on a difference between an estimated current time and a permanent magnet temperature at the end of positioning.   The galvano scanner according to claim 1, wherein the amount of heat generated by each of the rotor and the stator is estimated from a torque command coordinate sequence stored in the storage unit and frequency components of eddy current losses generated in a permanent magnet. Control device.   3. The galvano scanner control device according to claim 1, wherein the torque command generator changes the positioning time from the permanent magnet temperature at the end of positioning estimated by the temperature estimation means and the torque command limit value. A galvano scanner control device.   A laser processing apparatus comprising the galvano scanner control device according to claim 1.

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