JP4327318B2 - Variable curvature mirror - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable curvature mirror capable of changing the curvature of a reflecting surface of a mirror that reflects laser light.
[0002]
[Prior art]
For example, as a variable-curvature mirror used in a laser processing machine, as a means of changing the curvature of the reflecting surface to an arbitrary shape such as a concave surface, a flat surface, or a convex surface, PZT (piezo The element is pushed or retracted as an actuator, and a space is provided in the back of the mirror with the outer periphery fixed, and the space is changed to a positive or negative pressure region by hydraulic or pneumatic pressure by the principle of a balloon. In general, a method of changing the curvature of the mirror is generally used.
[0003]
Therefore, it is not necessary for the conventional variable curvature mirror to change the reflection surface at a high frequency. Actually, the change in the curvature of the reflection surface of the mirror is gradual, and it functions satisfactorily with a followability of about 10 Hz. It is.
[0004]
Conventionally, in the curvature variable mirror configured by the above method, the position of the condensing point where the laser light output from the laser oscillator is condensed by the condensing lens changes according to the distance from the laser oscillator, and as a result It is mainly used for the purpose of correcting the phenomenon that the positional relationship with the work material is not stable.
[0005]
Specifically, first, the curvature of the variable curvature mirror is changed in accordance with the distance from the laser oscillator, and the propagation characteristic of the laser light incident on the condenser lens is changed to change the focal length (condensation). The distance between the lens and the condensing point) is to be stable over the entire processing region. Second, the condensing diameter (spot diameter) obtained by changing the diameter of the laser light incident on the condensing lens is controlled to change according to the workpiece.
[0006]
However, these conventional techniques only use the propagation characteristics of the laser beam output from the laser oscillator and the optical change within the range of the diffraction phenomenon.
[0007]
[Problems to be solved by the invention]
However, as for the response speed of the reflection surface curvature change, the above-described method using the PZT actuator depends on the characteristics of the piezo element itself, and the limit is 20 to 50 Hz. In the system in which the curvature of the mirror is changed by liquid pressure or air pressure, since liquid or gas is used as a medium, it depends on the principle and the control device, and it cannot be expected to exceed 10 Hz.
[0008]
Furthermore, the method using PZT as an actuator is:
(1) A high voltage (500 to 600V) is required for control, but the variable curvature mirror includes a cooling water circuit, so safety is required, and there is a problem in the insulation method and maintenance. .
[0009]
{Circle around (2)} Since the PZT element has hysteresis, it is necessary to control the stroke displacement amount separately with a strain gauge or the like to control the closed loop.
[0010]
(3) A variable curvature mirror using a PZT element is expensive (1 million yen or more) due to its structural complexity.
[0011]
(4) Even if the mirror, which is a consumable item, deteriorates, the mirror cannot be replaced in the field due to the complexity of the structure, so it must be sent back to the manufacturer, which is cumbersome and takes time.
[0012]
There are problems and improvements.
[0013]
The object of the present invention is to provide a follow-up function capable of following the change in the curvature of the reflecting surface, and to change the propagation characteristics of the laser light incident on the condenser lens with high speed and response. It is possible to cause a change in the optical axis direction, that is, the vertical direction, in the state, and to create a state with a pseudo long focal depth compared to the conventional case, thereby providing improved cutting ability It is in.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a variable curvature mirror according to a first aspect of the present invention is a variable curvature mirror capable of changing the curvature of a reflecting surface of a mirror that reflects laser light, the mirror having a fixed periphery. A cylindrical push plate that has a thick central part that presses the mirror and presses the mirror, and a bottom surface that is thin on the outer periphery, and an actuator that presses the central part of the push plate. A magnetostrictive element that expands and contracts due to a change in position, an electromagnetic coil that applies a magnetic field to the magnetostrictive element, a push rod that transmits expansion and contraction of the magnetostrictive element to the push plate, and the magnetostrictive element to the magnetostrictive element via the push rod Urging means for applying an appropriate compressive load in advance in the axial direction, and a position adjuster capable of moving the magnetostrictive element in the axial direction With the door, the reflection surface when the mirror is no change in curvature by the actuator is characterized in that it is a concave shape.
[0015]
Accordingly, the curvature of the reflecting surface of the mirror is changed by indirectly pushing the back surface of the mirror through the push plate that is a pressing member. At this time, the expansion and contraction of the magnetostrictive element is controlled by applying a low voltage current to the electromagnetic coil by using a magnetostrictive element as an actuator and disposing an electromagnetic coil on the outer periphery thereof. The strain response speed of the magnetostrictive element is about 2 KHz, and a sufficiently high speed response is possible as compared with a conventional curvature change mirror. In addition, since the mirror is configured to transmit the strain force of the magnetostrictive element, which is an actuator, via the push plate, which is a pressing member, the shape of the push plate can be changed as needed without replacing the mirror itself. Thus, the amount of change, curvature, and shape of the mirror reflecting surface can be changed. Further, the load from the actuator applied to the central portion is converted to an appropriate distributed load on the mirror back surface through the push plate, and the effective diameter of the curvature of the reflecting surface can be increased. Furthermore, even when effective cooling is required as the output of laser oscillators increases, the strength of the push plate can be increased by increasing the force density (output per mass) of the magnetostrictive element. And it becomes possible to supply cooling water to the push plate which is a press member as needed, and it is possible to prevent the influence by the water pressure of cooling water. Further, the expansion and contraction of the magnetostrictive element is transmitted to the push plate by the transmission member, and by applying a compressive load to the magnetostrictive element in advance, it becomes possible to ensure the linearity of the amount of strain generated from the magnetic flux generated in the electromagnetic coil. Further, the initial adjustment for detecting the contact with the push plate by the position adjustment function is facilitated. Further, the reflecting surface of the mirror is concave when the actuator is not operated, but when the actuator is operated, the curvature of the reflecting surface can be changed from concave to flat to convex .
[0016]
A variable curvature mirror according to a second aspect of the present invention is the variable curvature mirror according to the first aspect, characterized in that a water channel for cooling the electromagnetic coil and the push plate is provided .
[0017]
Therefore, since the magnetostrictive element is used, it can be driven at a low voltage, and the cooling water is supplied to the water channel to cool the electromagnetic coil and the push plate as the pressing member, and the thermal expansion of each part due to the heat generation of the electromagnetic coil. It is possible to eliminate the change in the curvature of the mirror caused by the above, and although it is indirect to the mirror, it is possible to expect a cooling effect equivalent to that of the conventional variable mirror .
[0018]
According to a third aspect of the present invention, there is provided a variable curvature mirror according to any one of the first and second aspects, wherein the amount of change in curvature of the mirror reflecting surface due to the amount of distortion of the magnetostrictive element is captured between the actuator and the push plate. The piezoelectric element is provided .
[0019]
Therefore, the piezoelectric element between the actuator and the push plate as a pressing member controls the change in the curvature of the mirror reflecting surface, in other words, it can be fed to the control in order to control the amount of distortion of the magnetostrictive element. It becomes possible. Further, since the temperature of the magnetostrictive element itself can be kept substantially constant, the influence of the thermal expansion of the magnetostrictive element itself is minimized, so that the electromagnetic coil is controlled by low voltage (20-30V) current control (0-5A). It becomes possible to control the curvature of the mirror by the amount of distortion caused by the magnetic field generated .
[0021]
A variable curvature mirror according to a fourth aspect of the present invention is the variable curvature mirror according to the first, second, or third aspect, wherein the mirror and the push plate are assembled to the main body individually or together via an insulating member. Thus, the structure is such that the space between the magnetostrictive element and the tip of the push rod located between the mirrors can be electrically insulated .
[0022]
Therefore, when the mirror and the push plate as the pressing member are assembled to the main body via the insulating member, other components including the main body are electrically insulated. Thereby, the electrical resistance value between the mirror and one part of the main body is confirmed, and the position where the push plate and the tip of the push rod come into contact can be confirmed .
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0032]
FIG. 2 shows a configuration of a laser processing machine 3 using the variable curvature mirror 1 according to the present invention. In this laser processing machine 3, the laser beam LB emitted from the laser oscillator 5 is reflected by the mirror 7 and is incident on the variable curvature mirror 1, and is reflected by the variable curvature mirror 1, so that the X axis, the Y axis, The workpiece W is irradiated through a condenser lens 13 of a laser processing head 11 that is moved relative to the workpiece W by a motor 9 such as a Z-axis.
[0033]
The laser oscillator 5 and the motor 9 are controlled by the NC device 15. Further, the variable curvature mirror 1 changes the curvature of the reflection surface 19A (see FIG. 1) in accordance with an actuator stroke signal from the controller 17 to which a machine coordinate signal is sent from the NC device 15. At this time, the pressure signal from the variable curvature mirror 1 is fed back to the controller 17.
[0034]
FIG. 1 shows the above-described variable curvature mirror 1 according to the present invention. In this variable curvature mirror 1, the peripheral edge of the circular mirror 19 is sandwiched between mirror insulating rings 21A and 21B as an example of an insulating member. The mirror insulating rings 21 </ b> A and 21 </ b> B are fixed by being pressed by an attachment plate 25 and a mirror presser plate 27 with bolts 23. Therefore, the mirror 19 is attached to the attachment plate 25 in an electrically insulated state.
[0035]
The attachment plate 25 is biased toward the mirror block 29 by a plurality of attachment retracting springs 33 elastically mounted between the stripper bolts 31 screwed into a plurality of locations of the mirror block 29. Adjustment bolts 35 and fixing bolts 37 are provided at a plurality of locations on the attachment plate 25 so that the distance from the mirror block 29 can be adjusted.
[0036]
A space 39 is provided at the center of the attachment plate 25, and a push plate 43 as an example of a cylindrical pressing member with a flange 41 in contact with the back 19 </ b> B of the mirror 19 is provided in the space 39. Yes. Here, the side surface (contact surface) of the push plate 43 in contact with the back portion 19B of the mirror 19 is a flat surface, and the thickness of the central portion 19C is smaller than the thickness of the outer peripheral portion 19D. It has a shape.
[0037]
Further, in the push plate 43, in order to prevent stress from concentrating on the center portion of the mirror 19, the central portion 43C of the surface in contact with the back surface 19B of the mirror 19 is thick and the outer peripheral portion 43B is thin. ing. The side surface opposite to the mirror 19 of the central portion 43C of the push plate 43 is flat.
[0038]
The flange 41 of the push plate 43 is attached to the attachment plate 25 with a plurality of bolts 49 via push plate insulating rings 45 and 47 as insulating members. Therefore, the push plate 43 is attached to the attachment plate 25 in an electrically insulated state.
[0039]
An actuator 51 that pushes the push plate 43 downward in FIG. 1 is provided on the rear surface of the push plate 43 described above. In this actuator 51, an example of a push rod 59 as a transmission member having a T-shaped cross section for pushing the central portion 43 </ b> C of the push plate 43 inside an actuator case 57 constituted by the actuator housing 53 and the actuator fixing plate 55. Is provided to be movable up and down in FIG.
[0040]
The front end of the push rod 59 is provided in contact with the rear surface of the central portion 43C of the push plate 43. Between the upper surface of the flange 61 of the push rod 59 and the lower surface of the actuator fixing plate 55, for example, terbium is provided. A magnetostrictive element 63 made of an alloy of (Tb), dysprosium (Dy), and iron (Fe) by a powder metallurgy method is provided in contact therewith. The magnetostrictive element 63 is sliced to a thickness of 2 mm or less and then bonded to form a rod shape. In this way, heat generation is prevented by increasing the electric resistance value and reducing eddy current loss.
[0041]
A cylindrical electromagnetic coil 65 is provided around the magnetostrictive element 63. Note that a lead wire 67 is connected to the electromagnetic coil 65, and an electric signal is sent from the outside.
[0042]
Further, a magnetostrictive element preload spring 71 as a biasing means is provided between the lower surface of the flange 61 of the push rod 59 and the bottom 69 of the actuator housing 53, and biases the push rod 59 upward in FIG. By doing so, a compressive load is applied to the magnetostrictive element 63 in advance.
[0043]
A cooling water jacket 75 having a cooling water passage 73 is provided outside the actuator case 57 described above. The cooling water tube 77 provided through the cooling water jacket 75 cools the cooling water jacket 73. Supply water. The cooling water jacket 75 is attached to the attachment plate 25 together with the push plate insulating rings 45 and 47 and the push plate 43 by the bolt 49 described above.
[0044]
The actuator case 57 is attached to the cooling water jacket 75 by an actuator adjusting bolt 79, and the position of the actuator case 57 is supported by an actuator adjusting bolt 81 so that the push rod 59 can be adjusted. The pressing pressure can be adjusted.
[0045]
Alternatively, the piezoelectric element 83 is sandwiched between the push plate 43 and the push rod 59 to detect and feed back the contact pressure, thereby correcting the stroke of the magnetostrictive element 63 and controlling the curvature of the mirror 19. .
[0046]
The water channel 73 flows between the cooling water jacket 75 and the actuator case 57 to cool the magnetostrictive element 63 and the electromagnetic coil 65, and also supplies cooling water to the space 85 on the rear side of the push plate 43. The mirror 19 is cooled via the push plate 43. Here, even if the cooling water is supplied to the space 85 of the push plate 43, the push plate 43 has such rigidity that it does not deform, and the mirror 19 is not deformed by the cooling water.
[0047]
With the above configuration, a signal from the NC device 15 is converted into an actuator operation signal by the controller 17, and an electric signal is sent from the lead wire 67 to the electromagnetic coil 65. As a result, a magnetic field is generated, and the magnetostrictive element 63 extends in the axial direction. However, since the upper end surface of the magnetostrictive element 63 is pressed by the actuator fixing plate 55, it extends downward and pushes the push plate 43 downward. As a result, the reflecting surface 19A of the mirror 19 having a concave shape in which the thickness of the central portion is smaller than the thickness of the outer peripheral portion in advance changes the curved surface, and the shape changes from concave to flat to convex.
[0048]
At this time, since the magnetostrictive element 63 is previously loaded in the axial direction by the magnetostrictive element compression load spring 71, the hysteresis of the stroke with respect to the change of the magnetic field is minimized due to the characteristics.
[0049]
On the other hand, the heat generated by the electromagnetic coil 65 is cooled by the cooling water. The cooling water flows from the cooling water tube 77 through the water passage 73 between the cooling water jacket 75, the actuator housing 53 and the actuator fixing plate 55, and further pushed. It is also supplied between the plate 43 and the cooling water jacket 75. Thereby, the electromagnetic coil 65, the push plate 43, and the mirror 19 are cooled.
[0050]
The physical contact between the magnetostrictive element 63 and the push rod 59, the push rod 59 and the push plate 43, and the push plate 43 and the mirror 19 is confirmed by electrical continuity and adjusted by the actuator adjustment bolts 79 and 81. Alternatively, the initial value commanded to the electromagnetic coil 65 can be adjusted and set by the controller 17. Alternatively, as described above, the piezoelectric element 83 is sandwiched between the push plate 43 and the push rod 59 to detect and feed back the contact pressure, thereby correcting the stroke of the magnetostrictive element 63 to control the curvature of the mirror 19. It may be.
[0051]
From the above results, by using the magnetostrictive element 63 as an actuator part, it is possible to realize high responsiveness of the change in curvature of the reflecting surface of the mirror 19 at a low cost. Further, since the magnetostrictive element 63 has a large stroke with respect to its length, the variable curvature mirror 1 can be made compact, and the usability can be increased.
[0052]
Further, since the back surface of the mirror 19 itself is not pushed directly, but the back surface is pushed through the push plate 43 by the magnetostrictive element 63, the mirror 19 can be easily replaced.
[0053]
In addition, since a compressive load is applied in advance to the magnetostrictive element 63 by a spring, the hysteresis with respect to the stroke displacement of the magnetostrictive element 63 can be minimized, and the change in curvature can be controlled with high accuracy.
[0054]
The present invention is not limited to the embodiment of the invention described above, and can be implemented in other modes by making appropriate modifications. That is, in the above-described embodiment of the present invention, the case where the variable curvature mirror 1 according to the present invention is applied to the laser processing machine 3 has been described, but the present invention is not limited to this and can be applied to various types.
[0055]
【The invention's effect】
As described above, in the variable curvature mirror according to the first aspect of the present invention, the mirror is reflected by pushing the mirror through the cylindrical push plate whose bottom surface is the contact surface with the actuator portion having a thick central portion and a thin outer peripheral portion. Change the curvature of the surface. At this time, since the magnetostrictive element and the electromagnetic coil are used as the actuator section, the expansion and contraction of the magnetostrictive element can be controlled at high speed and with high accuracy by controlling with the electromagnetic coil at a low voltage. Further, since the stroke with respect to the length of the magnetostrictive element is large, the actuator portion can be made compact and the cost can be reduced. In addition, since the mirror is in contact with the actuator section via a push plate that is a pressing member, it can be easily replaced by removing only the mirror when replacing the mirror after initial adjustment. can do. In addition, since the push plate , which is a pressing member, has a thick central portion and a thin outer peripheral portion, the push plate can maintain rigidity enough to prevent deformation due to the cooling water pressure when the cooling water is supplied to the push plate . Further, when the central portion is pushed by the actuator portion, it is possible to avoid a state in which only the central portion changes and the outer peripheral portion does not change. In addition, the expansion and contraction of the magnetostrictive element is transmitted to the push plate by the push rod which is a transmission member, and it is possible to ensure the linearity of the strain amount generated from the magnetic flux generated in the electromagnetic coil by applying a compressive load to the magnetostrictive element in advance. can do. Further, the initial adjustment for detecting the contact with the push plate by the position adjusting function can be facilitated. In addition, the reflecting surface of the mirror has a concave shape when the actuator is not operated. However, when the actuator is operated, the reflecting surface can be changed from a concave surface to a flat surface to a convex surface.
[0056]
The curvature variable mirror according the second aspect of the present invention, by supplying cooling water to the water passage can cool the push plate is an electromagnetic coil and the pressing member, the mirror is also indirect but cooling the entire surface Can do. As a result, it is possible to prevent an increase in the heat absorption rate due to the deterioration of the mirror over time. At this time, since the pressure of the cooling water is not directly applied to the mirror, an error in the curvature change due to the cooling water can be prevented. Further, since the temperature of the magnetostrictive element can be kept substantially constant, the influence of the stroke change due to the thermal expansion of the magnetostrictive element itself can be minimized .
[0057]
In the curvature variable mirror according to the third aspect of the invention, since the change in the curvature of the mirror reflecting surface is controlled by the piezoelectric element between the actuator and the push plate that is the pressing member, in other words, the amount of distortion of the magnetostrictive element is more accurate. You can feed pack to control to control with .
[0058]
In the variable curvature mirror according to the fourth aspect of the present invention, the mirror and the push plate as the pressing member are assembled to the main body via the insulating member, so that other parts including the main body are electrically insulated. Thereby, the electrical resistance value between the mirror and one part of the main body can be confirmed, and it is possible to confirm the position where the push plate as the pressing member and the tip of the push rod as the transmission member are in contact. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a variable curvature mirror according to the present invention.
FIG. 2 is a configuration diagram showing a case where a curvature variable mirror according to the present invention is applied to a laser processing machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Curvature variable mirror 17 Controller 19 Mirror 19A Reflecting surface 21A, 21B Mirror insulation ring (insulation member)
25 Attachment plate (plate)
27 Mirror presser plate (plate)
29 Mirror block 43 Push plate (pressing member)
43B Outer peripheral part 43C Central part 45, 47 Push plate insulating ring (insulating member)
59 Push rod (transmission member)
63 Magnetostrictive element (actuator part)
65 Electromagnetic coil (actuator part)
71 Magnetostrictive element compression load spring (biasing means)
73 Waterway 83 Piezoelectric element LB Ray

Claims (4)

A variable curvature mirror capable of changing the curvature of the reflecting surface of the mirror that reflects the laser light, and the central portion that presses the mirror in contact with the back surface of the mirror that is fixed to the periphery is thick and the outer peripheral portion is thin. A cylindrical push plate having a bottom surface as a contact surface; an actuator that presses the center of the push plate; and a magnetostrictive element that expands and contracts due to a change in the magnetic field; and an electromagnetic coil that applies a magnetic field to the magnetostrictive element ; A push rod that transmits expansion and contraction of the magnetostrictive element to the push plate, and an urging means that applies an appropriate compressive load in advance to the magnetostrictive element in the axial direction of the magnetostrictive element via the push rod, and A position adjusting mechanism capable of moving the magnetostrictive element in the axial direction, and the mirror has no change in curvature due to the actuator. Curvature variable mirror, wherein the reflecting surface in state is a concave shape. 2. The variable curvature mirror according to claim 1, further comprising a water channel for cooling the electromagnetic coil and the push plate . The variable curvature mirror according to claim 1 or 2, wherein a piezoelectric element is provided between the actuator and the push plate for capturing a curvature change amount of a mirror reflecting surface due to a strain amount of the magnetostrictive element. Variable curvature mirror . 4. The variable curvature mirror according to claim 1, wherein the mirror and the push plate are assembled to the main body individually or together via an insulating member, thereby being positioned between the magnetostrictive element and the mirror. The variable curvature mirror characterized by having a structure capable of being electrically insulated from a tip of the push rod .

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