JPH05169285A - Laser scanner - Google Patents

Abstract

PURPOSE:To reduce the driving force of motor by attaching a spring at the mirror or the lens and generating the recovering force toward the balancing point. CONSTITUTION:A flat mirror plate 20 is fixed to a cooling water jacket 21 having an air conditioner in the inside with the action of a mirror supporting tool 23. A cooling water entrances 24, 25 are bored at the cavity of the cooling water jacket 21 and the cooling water goes in and out from here. The center of swing is connected to the motor with a crank mechanism, and the whole of mirror is swing around the center of swing 22 with the driving power of the motor. Two springs 27, 28 are set between a base plate 26 and the rear surface of the cooling water jacket 21 in the compressed state. Because the spring constants of two springs are same and the lengths are also same, the position is symmetrical about the center of swing, so if the swing angle of mirror theta=0, the torque of spring is become zero. If the mirror is inclined, because the stability in proportion to the inclining angle theta is generated in the spring, so the motor driving force can be minimized, and a small motor can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a laser scanner using a mirror and a lens for scanning the light of a carbon dioxide laser. In a device that performs welding, cutting, heat treatment, etc. using the powerful power of a carbon dioxide gas laser, a scanning device for rocking the laser light from side to side is provided. The reason for oscillating the laser light to the left and right is to expand the range in which the laser light is irradiated, and the laser beam is emitted at a constant amplitude at right angles to the relative traveling direction of the laser light. Rock the rock. Since the laser light is light, the laser beam can be scanned by swinging the lens or mirror.

[0002]

2. Description of the Related Art A laser processing apparatus using the light of a carbon dioxide gas laser includes a laser light source, a scanning device for scanning the laser light from side to side, and a torch nozzle. .. The scanning device is composed of two mirrors that reflect the laser light focused by the lens twice, or a oscillating lens.
In the case of a mirror, if these are M ₁ and M ₂ , they are substantially parallel to each other, and the laser light converges in the original direction even if it is reflected twice. It is the action of the condenser lens installed in front of the scanning device that converges. When the angle between the mirror normal and the axis of the laser beam is Θ, the laser beam is reflected by M ₁ and travels in the (π-2Θ) direction, and M ₂
Even if it is reflected by, it travels in the original direction. Member to be processed is fed in a direction perpendicular to the plane P including the center of the mirror -M _1, M _2. With this alone, the trajectory of the laser light that hits the processed member becomes a straight line. In order to expand the range in which the laser light acts, the laser light is scanned in a direction perpendicular to the straight line. To do this, either M ₁ or M _2
It may be rocked in a plane P including the centers of ₁ and M ₂ . For example, assume that the mirror M ₁ is swung. The optical path length from M ₁ to the workpiece is L. If the oscillation amplitude of the mirror M ₁ is φ and the angular frequency of the oscillation is Ω, the mirror M
Tilt angle from the central position of the ₁ theta is given by θ = φsin Ωt (1). Therefore, the deviation Q from the center position of the beam in the member to be processed is Q = 2Lφ sin Ωt (2). Since a large amount of laser light hits the mirror to generate heat, cooling water is made to flow to the back surface. Since there is also a mechanism for holding the mirror, it is quite heavy even though it is called a mirror. In order to move it quickly, the power of the drive motor must be increased.

Conventionally, the shaft of the mirror is oscillated by a crank mechanism. FIG. 3 shows a perspective view of this. FIG. 4 shows a side view in the axial direction. An eccentric plate 2 is attached to the tip of the motor shaft 1, and an eccentric shaft 3 is fixed at a position slightly eccentric from the motor shaft 1. A connecting rod 4 is attached to the tip of the eccentric shaft 3 via a bearing 5. A crank 6 is attached to the other end of the connecting rod 4 via a bearing 7. At the other end of the crank 6, a mirror swing shaft 8 is rotatably supported by a bearing 9. Miller swing shaft 8
The mirror M ₁ is fixed to the tip of the. This is fixed not only with the mirror but also with some heavy items such as cooling water jackets and mirror mounts. When the motor rotates, the eccentric plate 2 rotates. Since the eccentric shaft 3 also rotates, the connecting rod moves left and right and the crank 6 swings. Such a crank mechanism is already well known.
It is well known to convert rotary motion into reciprocating motion.
In addition to this, there may be many mechanisms for rotating the mirror by rotating the motor.

[0004]

The mirror for scanning the light of the carbon dioxide laser to the left and right is not only a reflecting mirror, but also includes a cooling water jacket and has a considerable size and weight. There is. Inertia mode about the swing axis parallel to the plane
The ment is also quite large. In the case of simply rotating the motor, the driving force required for the motor may be small because the rotation naturally continues due to the inertia when the motor starts rotating anyway at first. However, here, not only the rotational movement but the swing movement by the crank is performed. Inertial movement is completely useless. Rather,
Excessive rotational moment is required when the rotational angular velocity changes from positive to negative and from negative to positive. Therefore, if the period of the rocking motion is large, the motor must bear a considerable driving force. For example, assuming that the mirror has a size of about 8 cm × 8 cm, the thickness including the mount and the cooling water jacket is about 4 mm, and the density of the member is about 6 gcm ⁻³ , the circumference of the axis parallel to the plane is assumed. Inertial secondary moment of about 4000 gcm ² .

For example, the swing amplitude is 1 ° (φ = π /
180), the torque is represented by Id ² θ / dt ² , and the maximum torque is T _max = IφΩ ² (3). Inertial secondary moment I = 4410
Since gcm ² , φ = π / 180, and Ω = 2π × 50 sec ⁻¹ , the maximum torque T _{max is} 0.76 Nm (4), which is considerably large. In order to obtain such a large torque, a large motor is required. However,
It is needless to say that it is desirable that the motor be as small as possible because it is a motor installed in the processing machine. The maximum torque T _max can be lowered by lowering the swing amplitude or lowering the swing number. However, the amplitude .phi. Cannot be lowered so much because the scanning amplitude becomes L.phi. And this must be a certain value. Further, if the oscillation frequency is too small, it becomes impossible to scan the laser beam to uniformly heat the workpiece in the vicinity of the straight line. Therefore, Ω must be large to some extent. This is because of the swinging of the mirror. SUMMARY OF THE INVENTION It is an object of the present invention to provide a oscillating device for a mirror, which can obtain a similar amplitude φ and frequency Ω / 2π even if the drive motor for oscillating the mirror is reduced. ..

[0006]

The laser scanner of the present invention forcibly oscillates a scanning mirror for reflecting laser light and scanning left and right by a motor, and at the same time a balance position direction by a spring. It is intended to reduce the driving force of the motor by urging the motor toward. The point that a spring was attached is new. The springs are mounted symmetrically with respect to the pivot axis so that the elastic forces cancel out at the mirror equilibrium point. In this way, the spring gives a restoring force to return the mirror to the equilibrium position θ → 0. Since the force of the spring and the force of the motor are added to oscillate the mirror, the load applied to the motor is reduced. When the angular velocity dθ / dt is positive and θ is negative, both the spring force and the motor force act in the same direction and increase θ. On the contrary, when the angular velocity dθ / dt is negative and θ is positive, both the spring force and the motor force work in the direction of decreasing θ. That is, by θ = φsinΩt,
When representing the angular displacement of the mirror, when the Ωt is in the first quadrant and the third quadrant, the force of the spring and that of the motor reinforce each other.

However, when the angular velocity dθ / dt is positive and θ is also positive, the motor exerts a force in the direction of increasing θ and the spring exerts a force in the direction of decreasing θ. When dθ / dt is negative and θ is negative, the motor decreases θ and the spring decreases θ.
A force is generated in the direction of increasing. In this case, the spring is
Work to weaken the power of the ta. The motor force must be greater than the spring force. This is of course. When .theta. =. phi.sin .OMEGA.t represents the angular displacement of the mirror, when .OMEGA.t is in the second quadrant and the fourth quadrant, the force of the motor and the spring weaken each other. If so, it seems that the spring force does not supplement the motor force in the middle of the merits and demerits, but it is not so. As described above, when the motor exerts the maximum force, it is the moment when the angular velocity dθ / dt changes from positive to negative or from negative to positive. At this time, the spring force changes this conversion. This is because it can strongly assist.

[0008]

A simplified view of the spring-supported mirror is shown in FIG. There are two springs S ₁ and S ₂ ,
It is assumed that this exerts elastic force on the mirror on both sides of the fulcrum O. Of course, there is data and a crank mechanism, and the point at which the mirror swings does not change. Spring S ₁ , S
_{The fact that} there is ₂ does not mean that it swings freely. The spring deflection is s ₁ and s ₂ , and the spring constant is k. The point of action of the spring on the mirror is R
₁ and R _2, and the distance from the midpoint O is 1/2. Spring S
_The counterclockwise moment due to ₁ is -ks ₁ l / 2, and the counterclockwise moment due to spring S ₂ is ks ₂ l /
2, so mirror as Total - respect, mode of _{k (s 2 -s 1) l} / 2 (5) - would be to add placements. Letting the force of the oscillating motion given by the motor be -Hsin Ωt, the following equation of motion holds. Id ² θ / dt ² + k (s ₂ −s ₁ ) 1/2 = −H sinΩt (6) However, θ is a small angle, so the springs S ₁ and S ₂
The difference between the displacements s ₁ and s ₂ of is proportional to θ and can be written as (s ₁ −s ₂ ) = − lθ (7). Then, the equation of motion becomes Id ² θ / dt ² + kl ² θ / 2 = −H sinΩt (8). Since at steady state is ^{θ = φsinΩt, φ (IΩ 2} -kl 2/2) = is a H (9), motor - drive force H is the spring S ₁ by data, S
It is a formula showing that it is decreased by the existence of ₂ . Without a spring, the maximum torque H of the motor is φ
Is a Iomega ^2, since use of the spring of spring constant k, the maximum torque H is than this φkl only ^2/2 is the smaller. (8) is a familiar equation of forced vibration, but the condition that the motion of the mirror is θ = φsinΩt is determined, not that H is fixed and the mirror moves freely. φ is mechanically determined, and Ω is determined by the rotation speed of the motor. Ω ₀ = (kl ² / 2I) ^1/2 (10) is the angular frequency of the natural vibration due to the spring and the mirror, but when Ω is brought close to Ω ₀ , the maximum torque H required for the motor is It gets smaller.

[0009]

1 is a schematic diagram of a laser scanner according to the present invention. The light from the carbon dioxide gas laser is condensed by the lens 11 and strikes the swing mirror M ₁ . It is reflected here and enters the fixed mirror M ₂ . The laser light reflected again here is guided to the outside through the opening of the torch nozzle 12 and is applied to the workpiece 13. Since the light is focused by the lens 11, the beam is dot-shaped on the workpiece 13. The workpiece 13 is sent in the x direction. The irradiation point of the laser beam moves in the -x direction, but since the first mirror M ₁ oscillates in the yz plane, it actually advances in the -x direction while scanning in the y direction. .. That is, the x and y coordinates of the beam convergence point on the workpiece 13 are x = vt (11) and y = 2LφsinΩt (12). L is the optical path length from the mirror M ₁ to the workpiece 13. If t is erased, the formula that gives the irradiation line 14 becomes y = 2Lφ sin (Ωx) / v (13), and while repeating scanning with an amplitude of 2Lφ and a pitch of 2πv / Ω on the xy plane (workpiece plane). , It can be seen that the beam spot moves. Mira -M _1, M ₂ is the fact Ke - located in the managing, moreover, these are adapted to pass the cooling water there is a cooling water jacket. For simplicity, illustration of these mechanisms is omitted.

FIG. 2 is an enlarged view of only the swing mirror M ₁ . The flat mirror plate 20 is fixed to the cooling water jacket 21 having a cavity inside by the action of the mirror support 23. The swing center 22 passes through the back surface of the mirror plate 20 in a direction parallel to the surface. Cooling water inlets / outlets 24 and 25 are formed in the cavity of the cooling water jacket 21 so that cooling water can enter / exit from there. The swing center is connected to the motor by a crank mechanism as shown in FIG. Due to the power of the motor, the entire mirror swings 22
Rock around. There is a base 26 fixed to the back of the mirror plate 20. Base 26 and cooling water jacket 21
Two springs 27 and 28 are provided between the back surface and the back surface of the. It is mounted in a compressed state. Since the spring constants of the two springs are the same and the lengths thereof are also the same, they are located symmetrically with respect to the swing center 22. Therefore, if the swing angle θ of the mirror is zero, the spring torques cancel each other out. Becomes When the mirror tilts, the spring generates a restoring force proportional to the tilt angle θ, and thus a restoring torque proportional to θ acts on the mirror. An example is given to specifically explain that the motor torque can be reduced by the action of the spring. Mirror board 20, cooling water jacket 2
1. The secondary inertial moment I around the center of swing of the mirror support 23 and the like is set to 4410 gcm ² , and the swing angle φ =
Assuming 1 ° (π / 180 radian), the frequency is 50 Hz
Then, the maximum torque when there is no spring is IφΩ ² = 0.76Nm (14) from (9). This is as described above. Assuming that the distance 1 of the action point of the spring is 51.2 mm and the spring constant of the spring is k = 1.7 kgf / mm, k = 1.7 × 9.
Since it is 8 × 10 ³ kg / sec ² , φ = π / 180
As a result, φkl ² /2=0.38 Nm (15). The maximum torque is IφΩ ² −φkl ² /2=0.38Nm (16), which is half that in the case without a spring. Make the spring stronger and the spring constant k = 2.5 kgf /
mm, the maximum torque is further reduced to 0.2 Nm
Becomes When the spring constant is 3.4kg weight / mm, the maximum torque is calculated on ^{IφΩ 2 -φkl 2/2 = 0Nm} (17) , and the drive motor - other forces will be referred to may very small. This is because the natural frequency of the spring and mirror system is 50 Hz.

From the above, the advantages of the present invention are apparent. Although the springs are parallel springs in FIG. 2, the springs may be arranged so as to form an isosceles trapezoidal leg as shown in FIG. In this case, assuming that the spring inclination with respect to the parallel lines is ψ, cos ψ enters as a correction term. Instead of (9), φ (IΩ ² −kl ² cos ψ / 2) = H (18). By doing so, the restoring force of the spring can be freely changed by changing ψ. In FIG. 6, two equal length bars 31 are provided by the pin 30.
One end of 32 is supported. The other ends of the bars 31, 32 are connected to the springs S ₁ , S ₂ by pins 33, 34. The springs S ₁ and S ₂ are connected to a part of the cooling water jacket 21 of the mirror M ₁ by pins 35 and 36. Since these pins are tightened, this shape can be maintained. The positions of the springs S ₁ and S ₂ shown by the solid lines have a small ψ, and the spring restoring force (kcos ψ) is large. This is an arrangement at the time of 50 Hz (Ω = 2π × 50 sec ⁻¹ ), for example. To reduce the driving frequency, ψ may be increased. The driving frequency is 10 Hz (Ω = 2π) at the position indicated by the thin line.
The position is × 10 sec ⁻¹ ). To change this, loosen the screw of the pin, rotate the springs S ₁ and S _2, and tighten the pin again. What has been described so far is a scanning device using a mirror. Of course, the present invention can be applied to a laser scanner using a lens. Figure 7
Shows this. The laser light enters the lens at a right angle.
The lens swings left and right by the crank mechanism. When swinging to the right, the laser light bends to the right, and when swinging to the left, the laser light bends to the left. Attach a spring to this lens. Since the restoring force of the spring supplements the force of the motor,
Ta power is saved.

[0012]

In the beam scanning device using the mirror and the lens of the laser processing device, the spring is provided to generate the restoring force, so that the motor driving force is further reduced. This allows the use of smaller motors. Since it is a small motor, the cost is low and it is easier to install in a narrow casing.
The degree of freedom in design can be increased.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a laser scanner of the present invention.

FIG. 2 is a sectional view of only an oscillating mirror.

FIG. 3 is a perspective view of a known crank mechanism for rocking a mirror.

FIG. 4 is a side view of a crank mechanism.

FIG. 5 is a principle view of the present invention showing a structure in which a parallel spring is attached to a mirror to give a restoring force.

FIG. 6 is a principle view of the present invention showing a spring in which a spring is attached to a mirror so as to hit a leg of an isosceles trapezoid to give a restoring force.

FIG. 7 is a perspective view showing a scanning device in which the present invention is applied to a scanning device that swings a lens to the left and right.

[Explanation of symbols]

1 Motor Shaft 2 Eccentric Plate 3 Eccentric Shaft 4 Connecting Rod 5 Bearing 6 Crank 7 Bearing 8 Miller Swing Shaft 9 Bearing M ₁ Swing Miller M ₂ Miller 11 Lens 12 Torch Nozzle 13 Workpiece

Claims (2)

[Claims] 1. A mirror for reflecting the light of a carbon dioxide gas laser,
Alternatively, it includes a transparent lens, one of the mirrors, a crank mechanism for rocking the lens, and a motor for driving the crank mechanism, and the laser light is generated by rocking the mirror or the lens. A laser scanner which scans left and right, wherein a spring for generating a restoring force toward an equilibrium point is attached to a mirror or a lens to reduce the driving force of the motor. 2. A mirror for reflecting the light of a carbon dioxide laser.
And a crank mechanism for swinging one of the mirrors, and a motor for driving the crank mechanism, and the laser light is scanned left and right by swinging the mirror. -In the scanner, two or more springs that generate a restoring force toward the equilibrium point are attached to the mirror, and the effective spring constant is changed by changing the angle ψ between the spring direction and the mirror normal. In this way, when the swinging angular frequency Ω of the mirror by the motor is changed, it is possible to adjust the canceling amount of the inertial torque of the mirror by changing the mounting angle ψ of the spring, and to restore the spring. A laser scanner characterized in that the driving force of the motor is reduced by force.