JPH0120721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to laser application machines such as laser processing machines and laser scalpels, and particularly to a cooling device for a condensing lens thereof.

For example, a laser processing machine, as is well known, uses a laser beam to perform cutting, drilling, welding, scribing, etc. on workpiece materials such as metal, synthetic resin, wood, glass, or ceramics. It consists of an oscillator for oscillating the laser beam, a bender and a light guide path that guide the laser beam to the vicinity of the irradiation point, and a condensing section with a built-in condenser lens that converges the laser beam from the light guide path and irradiates it onto the workpiece. It's on. In this laser processing machine, the higher the power density of the converged laser beam, the more advantageous it is in terms of processing efficiency and processing accuracy.In general, the energy of the laser beam that enters the condenser lens is a high-energy beam of several to several tens of kilowatts. It is used.

However, as the energy of such laser light increases, the possibility that the condenser lens generates heat increases. In other words, when a laser beam passes through a condensing lens, it is caused by, for example, an anti-reflection layer coated on the condensing lens, very slight absorption in the condensing lens material, or scattering due to irregularities on the condensing lens surface. Energy loss occurs and this lost energy is converted into heat. Therefore, the higher the energy of the laser beam and the longer the irradiation time, the more susceptible the condenser lens is to the effects of heat.
When thermal deformation occurs as a result of heat generation, the irradiation position of the laser beam shifts, and the refractive index changes, leading to a decrease in processing accuracy due to deviations in focal length, or the focusing efficiency of the laser beam decreases, reducing processing efficiency. This causes various problems such as a decrease in the durability of the condensing lens.

In order to solve these problems, conventionally, a cooling liquid passage for cooling the condensing lens is formed in the condensing section.
A laser processing machine is used in which the condensing lens is cooled with this cooling liquid, but this conventional equipment
The structure is complex and heavy due to the passages and piping for the coolant, and it also has the drawbacks of high cost and poor operability.

Furthermore, Japanese Patent Application Laid-open No. 102392/1983 discloses a condenser lens 2 that converges a laser beam 1, as shown in FIGS. 1 and 2.
is held in a lens holder 4 having cooling fins 3, and by cooling the cooling fins 3 with auxiliary gas that enters from the introduction pipe 5 and is ejected from the nozzle 6, the condenser lens 2 can be cooled without using cooling water. I'm trying to cool it down. The auxiliary gas injects gases such as oxygen and nitrogen toward the workpiece at a high flow rate, forcibly removing the molten material that has an extremely high absorption rate.
This aims to improve machining efficiency by always exposing a fresh surface to be machined. However, in this cooling structure, only a portion of the auxiliary gas supplied from the inlet pipe 5 comes into contact with the cooling fins, and even if the number of cooling fins is increased or fine irregularities are formed on the surface of the cooling fins, However, since a reliable cooling effect cannot be obtained, it is necessary to increase the heat capacity by using a large-diameter condensing lens, and it is still impossible to avoid an increase in size and cost.

Furthermore, when actual processing is performed using a conventional laser processing machine, the workpiece is instantly melted by the laser beam, so the melt of the workpiece and the evaporated atoms from the melt are scattered around by the auxiliary gas. This adheres to the lower surface of the condenser lens and causes contamination. This problem is also the same in laser processing machines with cooling fins as shown in Figs. This has a major practical drawback in that the condenser lens is inevitably damaged due to heat.

The present invention has been made to solve these problems, and includes a lens holder that holds a condensing lens, in which at least a part of the part in contact with the condensing lens is made of a porous material, and an auxiliary gas is characterized in that it is ejected from a nozzle after passing through the porous body and the lower surface of the condensing lens. By cooling the condensing lens directly by the auxiliary gas passing through the porous body, and then passing the auxiliary gas through the lower surface of the condensing lens,
A gas curtain made of auxiliary gas is formed on the lower surface of the condenser lens to prevent foreign matter from adhering to it.

The invention will now be described with reference to the illustrated embodiments. FIG. 3 is a longitudinal sectional view showing the basic configuration of the condensing lens cooling device of the present invention. Light guide tube 1 guiding laser light 1
1, an introduction pipe 13 for introducing an auxiliary gas 12 from an auxiliary gas supply source (not shown);
A nozzle 16 having a nozzle throat 15 is further removably screwed to the tip of the lens holder 14.

The lens holder 14 includes an outer cylinder 17 that is screwed onto the light guide tube 11, an annular porous ring 19 that directly holds the condensing lens 18, and an annular porous ring 19 that is connected to the outer cylinder 1.
It is composed of a presser ring 20 that is fixed to 1,
An annular gas passage 21 communicating with the introduction pipe 13 is formed in the outer cylinder 17 . The annular gas passage 21 communicates with an annular chamber 22 that accommodates the annular porous ring 19 through a plurality of communication holes 23 in the optical axis direction, and the auxiliary gas 12 is supplied from the annular gas passage 21 and the communication holes 23 through the annular porous ring. 19.

The annular porous ring 19 has a convex portion 24 that holds the lower surface (laser light emitting surface) of the condenser lens 18 . The convex portion 24 may be annular or may be divided into a plurality of parts in the circumferential direction. gas injection layer). Upper surface of condensing lens 18 (laser light incident surface)
is in contact with a position regulating surface 25 provided integrally with the outer cylinder 17. This position regulating surface 25 is the condensing lens 18
It has the function of regulating the position of the auxiliary gas 12 and at the same time preventing the auxiliary gas 12 from flowing to the upper surface side of the condensing lens 18.

The annular porous ring 19 is formed using a material with excellent heat resistance and air permeability. For example, it can be composed of a sintered body of metal materials such as aluminum, brass, stainless steel, tungsten, and molybdenum, and it can also be made of sintered bodies of metal materials such as aluminum, brass, stainless steel, tungsten, and molybdenum. A solid body, a synthetic resin filter, etc. can be used. Note that 10 indicates a workpiece.

Therefore, in the present device having the above configuration, the auxiliary gas 12 is introduced into the lens holder 14 from the introduction pipe 13.
enters the annular porous ring 19 from the annular gas passage 21 through the communication hole 23. Since the upper surface of the condensing lens 18 is closed by the position regulating surface 25 as described above, the auxiliary gas 12 does not flow out to the upper surface of the condensing lens 18, and the auxiliary gas that has passed through the annular porous ring 19 does not flow out. All of the gas 12 is injected onto the lower surface of the condenser lens 18 from the gas injection layer d formed by the convex portion 24 . In this process, the annular porous ring 19
A part of the auxiliary gas 12 passing through the interior directly contacts the condensing lens 18 to cool it, and the auxiliary gas 12 that does not directly contact the condensing lens 18 also exchanges heat with the annular porous ring 19 to indirectly cool it. The condensing lens 18 is cooled down.

Furthermore, after cooling the condenser lens 18 in this manner, the auxiliary gas 12 injected from the gas injection layer d expands adiabatically and forms a gas curtain on the lower surface of the condenser lens 18 . For this reason, the condenser lens 18 is further cooled by this gas curtain, and this gas curtain also prevents foreign matter from adhering to the lower surface of the condenser lens 18, thereby preventing deformation of the condenser lens 18 due to heat generation and The energy loss of the laser beam in step 18 can be minimized, thereby maintaining processing accuracy and preventing damage to the condensing lens 18. Furthermore, the diameter of the expensive condensing lens 18 can be reduced to the diameter of the laser beam 1. It is possible to make the diameter as small as that of .

4 and 5 show other embodiments of the present invention. In this embodiment, the injection direction of the auxiliary gas 12 from the gas injection layer d is regulated by a presser ring 20, and the presser ring 20 has a protrusion 26 that closes the gas injection layer d, and a notch 27 that opens the gas injection layer d. are formed at approximately 180° each. The rest of the structure is the same as the embodiment shown in FIG. 3, and the same parts are given the same reference numerals.

According to this embodiment, the auxiliary gas 12 is ejected in one direction from the notch 27 toward the protrusion 26, making the gas curtain stronger and preventing foreign matter from adhering to the lower surface of the condenser lens 18. This can be more completely prevented and the transmittance and light-gathering ability of the condenser lens 18 can be kept constant. Of course, the angle and positional relationship between the protrusion 26 and the notch 27 are not limited to those in the embodiment, and can be modified as appropriate.

Furthermore, FIG. 6 shows an example in which the annular porous ring 19 is constructed from a combination. That is, the annular porous ring 19 in this embodiment is the metal sintered filter 19
It has a three-layer structure with a synthetic resin filter 19b placed between the metal sintered filter 19a and the metal sintered filter 19a.
For example, the filter a has a mesh size of 5 to 50 microns, and the synthetic resin filter 19b has a mesh size of 0.05 to 0.5 microns. According to this coupling structure, impurities in the auxiliary gas 12 can be removed by the synthetic resin filter with a particularly fine mesh, and fresh auxiliary gas 1 can always be delivered from the gas injection layer d.
2 can be adiabatically expanded and ejected. The annular porous ring 19 is to be replaced in a timely manner if it becomes clogged.

In the above embodiment, the annular porous ring 19 is in contact with the entire circumference of the condenser lens 18, and according to this example, it is possible to obtain a higher cooling effect. It is possible to obtain a certain cooling effect even if only the part in contact with the condenser lens 18 is made of a porous material. There is no need to hold it in a porous body. Furthermore, although the above embodiments apply the present invention to a laser processing machine, the present invention can also be applied to laser scalpels and other laser application machines.

As described above, in the present invention, at least a part of the lens holder of the condensing lens of a laser processing machine is made of a porous body, and an auxiliary gas is passed through the porous body to cool the condensing lens. The auxiliary gas that has passed through the mass is ejected from the bottom surface of the condenser lens to form a gas curtain on the bottom surface of the condenser lens, which simultaneously cools the condenser lens and prevents foreign matter from adhering to the bottom surface of the condenser lens. can be achieved. Therefore, damage to the condensing lens due to heat generation,
In addition to preventing the adhesion of molten material or its evaporated atoms, and keeping the transmittance or light-gathering ability of the condensing lens constant, the diameter of the condensing lens is made to be about the same as the beam diameter of the laser beam. It has the excellent effect of being able to be made small in diameter.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of the main parts showing an example of a condensing lens cooling device of a conventional laser processing machine, Fig. 2 is a cross-sectional view taken along the - line in Fig. 1, and Fig. 3 is a condensing lens cooling device of the present invention. FIG. 4 is a longitudinal cross-sectional view showing an embodiment of the lens cooling device, FIG. 4 is a vertical cross-sectional view of a main part showing another embodiment of the present invention, and FIG. 5 is an example of a presser ring used in the embodiment of FIG. 4. The perspective view and FIG. 6 are longitudinal sectional views of essential parts showing still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Laser light, 11...Light guide tube, 12...Auxiliary gas, 13...Introduction tube, 14...Lens holder, 17...Outer cylinder, 18...Condensing lens, 19...
... Annular porous ring, 20 ... Presser ring, 24 ... Convex part, 26 ... Protrusion part, 27 ... Notch part. d...Auxiliary gas injection layer.

Claims (1)

[Claims] 1. A condenser lens that focuses the laser beam onto the workpiece and a nozzle that injects auxiliary gas toward the workpiece are provided at the tip of the light guide tube that guides the laser beam. In the laser application device, at least a portion of the lens holder holding the condenser lens in contact with the condenser lens is made of a porous body, and the auxiliary gas is supplied to the porous body and the condenser lens. A condensing lens cooling device for a laser application machine, characterized in that the condensing lens is ejected from the nozzle after passing through the lower surface. 2. In claim 1, the lens holder has an outer cylinder fixed to the light guide tube, a convex portion for holding the lower surface of the condenser lens, and an annular porous body inserted into the outer cylinder. A condensing lens cooling device for a laser application machine, comprising a ring and a holding ring that fixes the annular porous ring to the outer cylinder. 3 In claim 2, the presser ring is:
A condensing lens cooling device for a laser application machine having a notch and a protrusion that controls the size of an auxiliary gas injection layer formed by a convex portion of an annular porous ring. 4. In any one of claims 1 to 3, the porous body is a sintered body of metal such as aluminum, brass, stainless steel, tungsten, etc.
A condensing lens cooling device for a laser application machine consisting of one or a combination of glass beads, ceramic sintered bodies, or synthetic resin filters.