JPH07108469B2 - Laser scanner drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary scanner device for a laser processing machine that polarizes incident laser light by rotating a polarization mirror to align the laser light, The present invention relates to an improvement for reducing a static frictional force of a driving force transmitting portion in a laser scanner driving device using a piezoelectric actuator as a driving source for its rotation.

[Conventional technology]

Laser light is used in various fields such as OA equipment and video equipment, as well as semiconductor fields such as laser markers and laser trimming. When using laser light, it is necessary to align the laser light, that is, to deflect and scan the laser, and conventionally, a galvanometer type laser scanner device is often used.

In this galvanometer type device, for example, JP-A-53-1439
As shown in Japanese Patent Publication No. 10, a mirror is attached to the rotating shaft of an electric motor having a stator and a finitely rotating rotor, and the output of a capacitance type position sensor arranged around the rotating shaft is fed back in response to a command signal applied to the electric motor. By doing so, the positioning of the mirror is performed.

[Problems to be Solved by the Invention]

However, in such a conventional device, a position drift of about 600 μrad / ° C occurs with a change in environmental temperature.

Since the rotation is due to magnetic force, the response is poor, and the rise of rotation is particularly slow (3 to 4 msec).

There was a problem.

The present invention has been made in view of such circumstances, and it is possible to achieve a high-speed response with a good start-up, and the positioning accuracy can be constantly maintained at a high level regardless of temperature changes. It is intended to provide a laser scanner driving device which reduces the static friction force in the above.

[Means for Solving the Problems]

Therefore, in the present invention, a piezoelectric actuator that generates a linear displacement corresponding to an input drive signal, and a rotary shaft of the polarization mirror is coupled to an output shaft thereof, and the linear displacement of the piezoelectric actuator is converted into a rotary displacement, And a conversion amplification mechanism that amplifies the displacement, a command output unit that outputs a command signal that rotationally drives the polarization mirror, and a high-frequency generation unit that generates a high-frequency AC signal to be superimposed on the command signal,
A command signal on which the high frequency signal is superimposed is input to the piezoelectric actuator.

[Action]

With this configuration, the minute linear displacement of the piezoelectric actuator is converted into rotational displacement by the conversion mechanism and is amplified, and the polarized mirror is rotationally driven by the amplified rotation. Further, the piezoelectric actuator receives a command signal on which a high frequency alternating signal is superimposed by the high frequency generating means. Therefore, the conversion amplification mechanism for transmitting the driving force of the piezoelectric actuator constantly vibrates slightly, thereby eliminating static friction and reducing transmission torque loss.

〔Example〕

Hereinafter, the present invention will be described in detail according to embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of a laser scanner device according to the present invention.

This scanner device includes a polarization mirror 1, a ball screw 2, a piezoelectric actuator 3, a position sensor 4 and a controller as a displacement magnifying mechanism and a linear motion → rotation converting mechanism.
It is composed of 20 mag.

The piezoelectric actuator 3 is operated by a command signal from the controller 20, and generates a linear displacement (direction of arrow A) corresponding to the input command signal. The piezoelectric actuator 3 has an advantage that a large driving force and high-speed response can be obtained as compared with other actuators.

The piezoelectric actuator 3 is in contact with the flange 5. The flange 5 is formed integrally with the pole screw 2. A hole 9 is formed in the flange 5, and the guide shaft 8 is fitted in the hole 9. Therefore, as the piezoelectric actuator 3 is displaced in the A direction, the ball screw 2 also moves in the A direction. A ball screw groove 6 is formed on the shaft 7, and the ball screw 2 is fitted into the ball screw groove 6 via a large number of balls. That is, as is well known, the ball screw 2 converts a linear movement displacement of the piezoelectric actuator 3 into a rotational displacement and expands the displacement. When the piezoelectric actuator 3 is displaced in the A direction, the shaft 7 is moved accordingly. Rotate.

The shaft 7 is rotatably supported by the main body 12 of the apparatus by bearings 10 and 11, and the shaft 7 is coupled to the rotation axis 13 of the polarization mirror 1. The rotation of the polarization mirror 1 causes the laser light incident from a laser light emission source (not shown) to be polarized and scanned.

The position sensor 4 is of a non-contact type and detects a distance Δy to the flange 5, that is, an actual displacement of the piezoelectric actuator 3, and a signal Vs (= K ₁ Δy) corresponding to the detected distance Δy.
Is input to the comparator 21 of the controller 20. A signal Vc which is a target rotation angle for rotating the polarization mirror 1 is input from the command unit 22 to the comparator 21, and the comparator 21 takes these deviations ΔV (= Vc-Vs) and Is input to the control circuit 23. The control circuit 23 uses the input deviation signal ΔV as a command signal for the piezoelectric actuator 3 in the power amplifier.
Enter in 24.

On the other hand, the high frequency AC signal Z (1 to 5 KHz) from the high frequency signal generator 30 is input to the input line of the power amplifier 24, and the high frequency AC signal is superposed on the command signal ΔV from the control circuit 23. It Then, the power amplifier 24 amplifies the command signal ΔV + Z on which the high-frequency AC signal is superposed, and outputs the amplified signal K ₂ (ΔV + Z) to the piezoelectric actuator 3.
To enter.

The operation of the controller 20 will be described with reference to FIG. In the explanation using FIG. 2, the control circuit 23
The feedback signal Vs is ignored to simplify the waveform of the command signal output from the target angle signal from the command unit 22.
It is assumed that Vc is directly input to the power amplifier 24.

It is assumed that the command unit 22 outputs a DC signal Vc as shown in FIG. 2A for reciprocally scanning the polarizing mirror 1 between the target angles θa and θb. This DC signal Vc
Has a frequency of, for example, about 500 Hz, and its voltage level is 0 to 300 kg when converted to the generated force of the piezoelectric actuator 3.
Is a value in the range. FIG. 2 (b) is a high frequency signal generator
It shows the high frequency AC signal Z output from 30, and this high frequency AC signal Z has an AC frequency of about 1 to 5 KHz,
The voltage level is a pulse wave or a sin wave having an amplitude of about 10 to 70 kg when converted into the generated force of the piezoelectric actuator 3. FIG. 2 (c) shows a signal in which the high frequency signal Z is superimposed on Vc, and FIG. 2 (d) shows the output of the power amplifier 24, as shown in FIG. The command signal k ₂ (Vc + Z) on which the high frequency signal Z is superimposed (actually k ₂ (Vc + Z−Vs)) is input to the piezoelectric actuator 3.

According to the structure of this embodiment, since the piezoelectric actuator 3 is used as a drive source in order to realize a high-speed response, a large driving force and a high-speed response up to about 200 Hz can be realized, and the rotation start-up is the same. The scanner angle is 2-3 times faster than the conventional device.

Moreover, since the displacement of the piezoelectric actuator 3 is detected by the non-contact type position sensor 4, the displacement can be detected without affecting the dynamic characteristics of the scanner mechanism.
Furthermore, since this displacement is fed back to the command signal, high-speed, drift-free positioning control with good reproducibility can be achieved.

Further, in this embodiment, the high frequency signal generator 30 is provided at the input stage of the control circuit 23 so that the high frequency AC signal is superposed on the command signal so that the ball screw 2, the flange 5, the shaft 7, the bearings 10 and 11, etc. A slight vibration is generated in the driving force transmission section constituted by. For this reason, the static friction of these transmission parts is removed, the transmission torque is reduced, and the step response and the positioning accuracy can be improved. That is, the piezoelectric actuator 3
If was driven by the signal of only the DC component output from the control circuit 23, there was a disadvantage that the friction of the driving force transmission portion was large, and the rising of rotation and the positioning accuracy were not improved. Therefore, in this embodiment, by adding a high frequency signal generator, the piezoelectric actuator 3 is driven by the command signal on which the high frequency AC signal is superimposed.

3 and 4 show another embodiment of the driving force transmitting portion. Incidentally, FIG. 4 is a transverse sectional view of FIG.

This scanner device includes a mirror 1, a differential gearbox 40 as a displacement amplification mechanism, a lever 41, a piezoelectric actuator 3, a reaction force spring 42, a position sensor 4, a bracket 43, and the like.

The piezo-electric actuator 3 generates a linear displacement in the direction of arrow B in the same manner as described above, and contacts the lever 41 via the pin 44.

The lever 41 is fixed to a shaft 45 and is rotatable about the shaft 45, and an L-shaped bracket 43 is attached to the side surface of the lever 41. The shaft 45 is an input shaft (low speed shaft) of the differential gearbox 40 described later.

Further, the force of the reaction force spring 42 acts on the lever 41 via the piston 46 in the direction of arrow C, and the lever 41 receives the force of rotating counterclockwise by the displacement of the piezoelectric actuator 3, and at the same time, the spring 42 It receives a force that rotates clockwise due to the reaction force of.

That is, the lever 41 converts the linear displacement Δx of the piezoelectric actuator 3 into a rotational displacement Δθ. This rotational displacement Δθ is expressed by the following relational expression, where L is the distance from the center of the shaft 45 to the center line of the piezoelectric actuator 3.

Δθ = Δx / L The non-contact type position sensor 4 measures the distance Δx to the bracket 43 attached to the lever 41, and outputs the signal Vs (= k ₁ Δx) corresponding to the detected distance Δx to the controller. Input to 20 comparator circuits 21 (FIG. 1).

Next, the differential gearbox 40 amplifies a minute rotational displacement of the lever 41, and as shown in FIG. 5, is composed of an inner ring shaft 50, an intermediate ring spline 51 and an outer ring spline 52. The inner ring shaft 50 is composed of an elliptical cam 53 and a ball bearing 54 fixed to the outer periphery thereof. The intermediate wheel spline 51 is a thin-walled cylindrical elastic body made of metal, and teeth (the number of teeth Z ₁ ) are formed on the outer circumference thereof. Outer ring spline 52
Is a ring-shaped rigid body, and teeth (the number of teeth Z ₂ ) having the same pitch as the intermediate wheel spline 51 are formed on the inner periphery thereof. The relationship between the number of teeth on the outer ring spline 52 and the number of teeth on the intermediate ring spline 51 is Z ₂ =
Z ₁ + n, and there are n tooth number differences between them.

The principle of the differential gearbox 40 will be briefly described in the case of deceleration. The inner ring shaft with the outer ring spline 52 fixed.
When 50 is turned, the intermediate wheel spline 51 is elastically deformed, and the meshing position between the intermediate wheel spline 51 and the outer ring spline 52 moves sequentially. Since the intermediate ring spline 51 has n fewer teeth than the outer ring spline 52, when the inner ring shaft 50 makes one rotation, the intermediate ring spline 51 is in the direction opposite to the rotation direction of the inner ring shaft 50 by the angle corresponding to the number of teeth n. Rotate to. That is, when the outer ring spline 52 is fixed, the inner ring shaft 50 is used as the input shaft, and the intermediate wheel spline 51 is used as the output shaft, the reduction ratio i = − (Z ₁ −
Z ₂ ) / Z ₁ = −n / Z ₁ deceleration can be achieved.

In the case of speed-up, it is the reverse of the above, and as shown in FIG. 6, the outer ring spline 52 is fixed, the intermediate wheel spline 51 is used as the input shaft, and the inner ring shaft 50 is used as the output shaft. The speed ratio i = −Z ₁ / n can be increased.

The differential gearbox 40 shown in FIG. 3 has the same speed increasing structure as that shown in FIG. 6, in which the outer ring spline 52 is fixed and the intermediate wheel spline 51 is connected to the low speed input shaft 45. The inner ring shaft 50 is connected to the high speed output shaft 47. Therefore, when the lever 41 is rotationally displaced by Δθ, this rotational displacement Δθ is transmitted to the differential speed increaser 40 via the low speed input shaft 45,
The high-speed output shaft 47 of the differential gearbox 40 is amplified and rotated by θ = (Δθ × Z ₁ / n) in the direction opposite to the rotational displacement Δθ. According to this differential gearbox 40, a large speedup rate of about 100 times can be easily obtained.

The polarization mirror 1 is attached to the high-speed output shaft 47 of the differential speed increaser 40, and the rotation of the polarization mirror 1 causes the laser light incident from a laser generation source (not shown) to be polarized and scanned.

The scanner device shown in FIGS. 3 and 4 is also driven by the same controller 20 as in the previous embodiment. That is, the high-frequency AC signal from the high-frequency generator 30 is superimposed on the signal output from the control circuit 23, and the piezoelectric actuator 3 shown in FIG. 3 is driven by the command signal on which the high-frequency AC signal is superimposed. Therefore, as in the previous embodiment, a slight vibration is generated in the driving force transmission part composed of the lever 41, the piston 46, the shafts 41, 47, the differential speed increaser 40, etc., thereby eliminating the static friction of these transmission parts. Will be done. In this embodiment, since the linear motion displacement of the piezoelectric actuator 3 is converted into the rotational displacement and amplified by the lever 41 and the differential gearbox 40, the amplification is larger than that of the ball screw 2 of the previous embodiment. It has the advantage that the rate (about 100 times) can be easily obtained.

Note that the present invention can be appropriately modified from the above-described embodiment, and the mechanism for converting the linear displacement into the rotational displacement and amplifying it is not limited to the one shown in the embodiment, and any other well-known Technology may be used.

Moreover, the configuration for detecting the displacement of the position sensor 4 is not limited to the embodiment, and any other configuration may be adopted as long as it detects the displacement of the piezoelectric actuator 3. Further, the structure for increasing the speed of the differential amplifier 40 shown in FIG. 3 is not limited to that shown in FIG.
Is fixed, the outer ring spline 52 is input and the intermediate wheel spline 51 is output, and various modifications can be made, and the present invention is not limited to the embodiment.

〔The invention's effect〕

As described above, according to the present invention, since the linear displacement of the piezoelectric actuator is converted into rotational displacement and enlarged to drive the polarization mirror in rotation, a high-speed response with good rising can be achieved and positioning accuracy can be improved. It can be kept constant regardless of the temperature, and more accurate laser processing can be achieved. Further, in the present invention, since the high frequency AC signal is superimposed on the command signal input to the piezoelectric actuator, the frictional force of the driving force transmission mechanism is reduced, which reduces the transmission torque loss and improves the step response. However, the positioning accuracy can be improved. Therefore, the productivity as a laser processing machine and the processing target can be expanded.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of the present invention, FIG. 2 is a time chart for explaining an operation example of the embodiment, and FIG.
FIG. 4 is a vertical cross-sectional view showing the structure of a mechanical portion of another embodiment of the present invention, FIG. 4 is a cross-sectional view thereof, FIG. It is a figure which shows an example of the drive mode of a differential gearbox. 1 ... Polarizing mirror, 2 ... Ball screw, 3 ... Piezoelectric actuator, 4 ... Optical contact type position sensor, 10, 11 ... Bearing, 20 ... Controller, 23 ... Control circuit, 30 ... High frequency generator, 40 ... Differential acceleration Machine, 41 ... Lever, 42 ... Reaction spring, 43
…bracket.

Claims (7)

[Claims] 1. A laser scanner driving device for polarizing and scanning a laser beam by rotationally driving a polarization mirror, wherein a piezoelectric actuator that generates a linear displacement corresponding to an input electric signal and an output shaft of the polarization mirror is rotated. A shaft is coupled, a conversion amplification mechanism that converts a linear displacement of the piezoelectric actuator into a rotational displacement and amplifies the displacement, a control unit that outputs a command signal that rotationally drives the polarization mirror, and the command signal A laser scanner driving device comprising: a high-frequency generating unit that generates a high-frequency AC signal to be superimposed, and a command signal on which the high-frequency signal is superimposed is input to a piezoelectric actuator. 2. The laser scanner driving device according to claim 1, wherein the conversion amplification mechanism is a ball screw. 3. The laser scanner according to claim 1, wherein the conversion amplification mechanism includes a member that converts a linear displacement of the piezoelectric actuator into a rotational displacement, and a displacement amplification mechanism that amplifies the rotational displacement of the member. Drive. 4. The displacement amplifying mechanism comprises a first shaft having an elliptical cam and a ball bearing attached to the outer periphery of the cam, and the ball bearing of the first shaft contacts the inner peripheral surface. A second shaft made of an elastic body having teeth formed on the outer peripheral surface thereof, and a tooth having a number of teeth different from the number of teeth formed on the second shaft, and a tooth meshing with the tooth of the second shaft 4. The laser scanner driving device according to claim 3, wherein is a differential amplifier having a rigid third shaft formed on the inner peripheral surface. 5. A third shaft of the differential gearbox is fixed,
The laser scanner driving device according to claim 4, wherein the second shaft serves as an input shaft and the first shaft serves as an output shaft. 6. A lever member pivotally supported such that the force of the piezoelectric actuator acts in the forward direction and the force of a predetermined elastic body acts in the reverse direction.
The laser scanner driving device described. 7. The control means includes a detecting means for detecting a displacement corresponding to a displacement of the piezoelectric actuator, a target value generating means for generating a signal corresponding to a target rotation angle of the polarizing mirror, and the target value generating means. The laser scanner driving device according to claim 1, further comprising: a means for obtaining a deviation between the output of the means and the output of the detecting means, and outputting the deviation as the command signal.