Abstract:
A laser oscillating apparatus includes a discharger for exciting a laser medium, a blower for blowing a laser gas and a laser gas path for connecting the discharger and the blower, and a laser oscillating apparatus characterized in that the blower includes a shaft portion provided with a blade wheel portion at a front end thereof, a driving portion for rotating the shaft portion, and a partition wall portion for separating the blade wheel portion and the driving portion, and a surface of the partition wall portion is provided with a metal layer dispersing precipitated polytetrafluoroethylene (PTFE).

Description:
This application is a U.S. national phase application of PCT International Application PCT/JP2004/018271. 
   TECHNICAL FIELD 
   The present invention relates to a laser oscillating apparatus and a laser working machine using a centrifugal blower. 
   BACKGROUND ART 
     FIG. 6  shows an example of an outline constitution of a laser oscillating apparatus of a background art. The laser oscillating apparatus of the background art will be explained in reference to  FIG. 6 . 
   The laser oscillating apparatus of the background art includes electrodes  2 ,  3  at a periphery of discharge tube  1  constituted by a dielectric member of glass or the like. Electrodes  2 ,  3  are respectively connected with power sources  4 . Discharge space  5  is formed at inside of discharge tube  1  interposed by electrodes  2 ,  3 . Further, a total reflection mirror and partial reflection mirror  7  are provided. Laser beam  58  is outputted from partial reflection mirror  7 . Arrow mark  9  designates a direction in which laser gas flows. Further, heat exchangers  11 ,  12  for lowering a temperature of the laser gas, a temperature of which rises by discharge in discharge space  5  and by operation of a centrifugal blower, are provided. Laser gas is circulated by using blowing means  43 . As blowing means  43 , for example, a centrifugal blower, mentioned later, or the like is used. Laser gas flow path  10  and discharge tube  1  are connected by laser gas introducing portion  14 . 
     FIG. 7  shows an example of an outline constitution of a laser working machine in the background art. The laser working machine of the background art will be explained in reference to  FIG. 7 . 
   Laser beam  58  outputted from the laser oscillating apparatus shown in  FIG. 6  is reflected by reflecting mirror  15  and is guided to a vicinity of work  16 . Laser beam  58  is converged into a high density energy beam by condenser lens  18  provided at inside of torch  17  and irradiated to work  16  to process the work  16 . Work  16  is fixed on work table  19  and a predetermined shape is obtained by moving torch  17  relative to work  16  by X axis motor  20  or Y axis motor  21 . 
     FIG. 8  shows a structure of a periphery of a centrifugal blower in the laser oscillating apparatus. 
   Motor  22  in centrifugal blower  43  includes motor rotor  22   a  in a direction orthogonal to a gravitational force direction (arrow mark G direction), and includes motor stator  22   b  on a lower side in the gravitational force direction (arrow mark G) (that is, lower side of drawing). A front end of shaft  29  coupled with rotor  22   a  is provided with blade wheel  23  and diffuser  24 . Laser gas is sucked from suction port  25  from an upper direction in the gravitational force direction and is provided with kinetic energy by a centrifugal force by rotation of blade wheel  23 . Thereafter, the kinetic energy is converted into pressure by diffuser  24  and a gas having pressure about 1.5 times as much as that of the suction port  25  is delivered from delivery port  26 . 
   Oil  27  is contained at a portion of casing  31  containing motor  22  below centrifugal blower  43  and is used for lubricating bearing  28  and cooling rotor  22   a . When oil mist generated from oil  27  invades laser gas circulated by blade wheel  23 , a purity of laser gas is reduced to bring about a significant drawback in laser oscillation. Hence, in order to restrain oil mist from invading a laser gas circulating portion (that is, laser gas flow path  10 ), partition wall portion  50  is provided to separate motor chamber  54  and gas circulating chamber  35 . A clearance (clearance  57  as shown by  FIG. 9 ) of several 100 μm is provided between partition wall portion  50  and shaft  29  to thereby construct a constitution of not hampering rotation of the shaft. 
   As described above, the clearance of several 100 μm is present at partition wall portion  50  and therefore, oil mist invades gas circulating chamber  35  from motor chamber  54  by passing the clearance by vacuum diffusion. In order to prevent this, by always exhausting a constant amount of gas from motor chamber  54  by using vacuum pump  32 , a pressure of motor chamber  54  is constituted by a pressure lower than that of gas circulating chamber  35 . A path reaching vacuum pump  32  from motor chamber  54  is provided with electromagnetic valve  33 , which is opened and closed as needed. 
     FIG. 9  shows a detailed structure of partition wall portion  50 . Clearance  57  of several 100 μm is provided between shaft  29  and metal seal  36  and a constant amount of laser gas always flows to clearance  57 . By the always flowing laser gas, invasion of oil mist from motor chamber  54  to gas circulating chamber  35  can be prevented. 
   Laser gas flowing through clearance  57  between shaft  29  and metal seal  36  is exhausted to outside as it is by vacuum pump  32  and therefore, it is necessary to supply an exhausted amount of laser gas to gas circulating chamber  35  by other route. This constitutes a consumption amount per unit time of laser gas in the laser oscillating apparatus and the laser working machine to share a large weight in running cost. 
   Therefore, it is a serious problem in view of reducing running cost how to reduce the consumption amount of laser gas per unit time. It is necessary to narrow clearance  57  in order to reduce the laser gas consumption amount. However, generally, laser gas passing through the clearance  57  includes sputtering particles by laser gas discharge and small unavoidable particles which are generated in a component assembling step. When clearance  57  is narrowed to about several 10 μm, there is a possibility of deteriorating reliability by clogging clearance  57  with the particles. 
   In the case of the background art of JP-A-10-184593, it is only disclosed to simply specify a shape and a dimension of metal seal  36  with regard to clearance  57  and it is not pointed out to prevent clogging of foreign matters as a problem. 
   Further, although JP-A-2004-207467 discloses an example of using a PTFE material at a partition wall portion and forming a minimum clearance by wearing PTFE by forcibly bringing the PTFE material and a rotating shaft into contact with each other, a high accuracy is difficult to ensure by the method. 
   DISCLOSURE OF THE INVENTION 
   A laser oscillating apparatus of the invention is an apparatus including discharging means for exciting a laser medium, blowing means for blowing a laser gas, and a laser gas path for connecting the discharging means and the blowing means, and is a laser oscillating apparatus characterized in that the blowing means is blowing means including a shaft portion provided with a blade wheel portion at a front end thereof, a driving portion for rotating the shaft portion and a partition wall portion for separating the blade wheel portion and the driving portion, and a surface of the partition wall portion is provided with a metal layer dispersing precipitated polytetrafluoroethylene (PTFE). 
   By the constitution, a highly reliable laser oscillating apparatus and a highly reliable laser working machine capable of reducing running cost by restraining a gas consumption amount and capable of being used stably over a long period of time can be realized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an outline constitution view of a laser oscillating apparatus according to an embodiment of the invention. 
       FIG. 2  is a view of a structure of a centrifugal blower portion of the laser oscillating apparatus according to the embodiment. 
       FIG. 3  is a view of a structure of a partition wall portion of the laser oscillating apparatus according to the embodiment. 
       FIG. 4  is a diagram showing volume content, dynamic friction coefficient and exfoliation performance of polytetrafluoroethylene included in nickel plating according to the embodiment. 
       FIG. 5  is an outline constitution view of a laser working machine according to the embodiment. 
       FIG. 6  is an outline constitution view of a laser oscillating apparatus of a background art. 
       FIG. 7  is an outline constitution view of a laser working machine according to a background art. 
       FIG. 8  is a view of a structure of a centrifugal blower portion of the laser oscillating apparatus of the background art. 
       FIG. 9  is a view of a structure of a partition wall portion of the laser oscillating apparatus and the laser working machine of the background art. 
   

   DETAILED DESCRIPTION 
   An embodiment of the invention will be explained in reference to the drawings. 
   (Embodiment) 
     FIG. 1  shows an example of an outline constitution of laser oscillating apparatus  101  according to the embodiment and a detailed explanation will be given thereof in reference to  FIG. 1  as follows. 
   Laser oscillating apparatus  101  includes discharge tube  1  made by a dielectric member and electrodes  2 ,  3  provided at a periphery of discharge tube  1 . Electrodes  2 ,  3  are respectively connected to power source  4 . A region interposed between electrodes  2 ,  3  is discharge space  5  at inside of discharge tube  1 . Further, total reflection mirror  6  and partial reflection mirror  7  are provided and laser beam  8  is emitted from partial reflection mirror  7 . Arrow mark  9  designates a direction in which laser gas flows. 
   Further, heat exchangers  11  and  12  for lowering a temperature of laser gas, a temperature of which rises by discharge in discharge space  5  and driving a centrifugal blower, are provided and as blowing means  13  for circulating laser gas, for example, a centrifugal blower or the like, mentioned later, is used. Laser gas flow path  10  and discharge tube  1  are connected by laser gas introducing portion  14 . 
   Next,  FIG. 2  shows a structure of a periphery of a centrifugal blower in the laser oscillating apparatus. 
   Motor  22  provided by centrifugal blower  13  in a gravitational force direction (arrow mark G direction) is constituted by motor stator  22   b  and motor rotor  22   a . Motor  22  includes rotor  22   a  in a direction orthogonal to the gravitational force direction (arrow mark G direction) and includes motor stator  22   b  on a lower side in the gravitational force direction (arrow mark G direction) (that is, lower side of drawing). A front end of shaft  29  coupled with rotor  22   a  is provided with blade wheel  23  and diffuser  24 . Laser gas  110  is sucked from suction port  25  from an upper direction in the gravitational force direction and is provided with kinetic energy by a centrifugal force by rotation of blade wheel  23 . Thereafter, the kinetic energy is converted into pressure by diffuser  24  and the gas having a pressure about 1.5 times as much as that of suction port  25  is delivered from delivery port  26 . 
   Oil  27  is contained at a portion of casing  31  containing motor  22  at a lower portion of centrifugal blower  13 , and is used for lubricating bearing  28  and cooling rotor  22   a . When oil mist generated by oil  27  invades inside of laser gas  110  circulated by blade wheel  23 , a purity of laser gas  110  is reduced to bring about a significant drawback in laser oscillation. Therefore, partition wall portion  30  is provided in order to restrain oil mist from invading a laser gas circulating portion (laser gas flow path  10 ) and separates motor chamber  34  and gas circulating chamber  35 . As shown by  FIG. 3 , partition wall portion  30  is constituted by metal seal  36  and shaft  29  at a vicinity of metal seal  36 . Clearance  37  is provided between metal seal  29  and shaft  29  and is constructed by a constitution of not hampering rotation of the shaft. 
   As shown by  FIG. 3 , clearance  37  is included in partition wall portion  30  and therefore, normally, oil mist passes through the clearance and invades gas circulating chamber  35  from motor chamber  34  by vacuum diffusion. As a countermeasure thereagainst, there is constructed a constitution in which a constant amount of gas is always exhausted from motor chamber  34  by vacuum pump  32  and a pressure of motor chamber  34  is lower than that of gas circulating chamber  35  and electromagnetic valve  33  provided between motor chamber  34  and vacuum pump  32  are opened and closed as needed. 
   The constant amount of laser gas always flows at clearance  37  between shaft  29  and metal seal  36 . That is, since laser gas always flows through clearance  37 , oil mist can be prevented from invading gas circulating chamber  35  from motor chamber  34 . 
   Normally, shaft  29  is made of stainless steel and metal seal  36  is constituted by a copper containing material. In contrast thereto, according to the embodiment, surfaces of shaft  29  and metal seal  36  are coated by coating  38  of nickel plating including polytetrafluoroethylene (PTFE) particles. Further, nickel plating including PTFE particles refers to nickel Teflon plating by electroless plating for example and PTFE particles are uniformly dispersed and precipitated in a skin film plated by nickel. (“Teflon” is a registered trade mark of PTFE by DuPont Corporation) 
   Since the surface of metal seal  36  and the surface of shaft  29  are coated by nickel plating including PTFE particles, in contrast to a normal metal surface which is not subjected to the above-described coating processing, the surfaces are very excellent in a sliding property. Therefore, even when a foreign material invades clearance  37 , a possibility of bringing about a drawback of clogging the clearance when the foreign material invades or the like can be reduced. Further, the surface subjected to nickel Teflon plating by electroless plating is provided with excellent water repellency. Therefore, there is also achieved an effect of reducing adherence of a particularly wet foreign material to the surface of coating  38  in clearance  37 . 
   According to the embodiment, clearance  37  can be made to be infinitely smaller than several 100 μm of the background art in a range permitted by a machining accuracy. Therefore, an amount of laser gas passing through clearance  37  can be reduced and a significant reduction in running cost can be achieved by restraining a laser gas consumption amount per unit time. Specifically, clearance  37  can be reduced to 20 μm. Even in this case, high speed rotation (700 Hz) of shaft  29  can be permitted. 
   As described above, in the present embodiment, resin is included in the metal material by 15% or more and 60% or less. Therefore, a dimensional accuracy can be ensured by the metal material and the sliding property can be ensured by the resin material. That is, the dimensional accuracy and the sliding property can be made to be compatible with each other. Particularly, a constitution of including PTFE, which has high sliding property among resins, in electroless plating whose major component is nickel is excellent in obtaining compatibility of the dimensional accuracy and the sliding property. Further, when a gas is generated from the resin material or the metal material used in the process, the generated gas is mixed into laser gas to deteriorate a laser characteristic. Nickel and PTFE are preferably in view of reducing occurrence of such a problem. 
     FIG. 4  shows volume content, a dynamic friction coefficient and an exfoliation performance of PTFE included in nickel plating. It is found that when the volume content of PTFE is less than 15%, the dynamic friction coefficient is increased and a sufficient sliding performance cannot be ensured. On the other hand, when the volume content of PTFE is larger than 60%, separation of PTFE particles from the plated metal is brought about and coating per se cannot be ensured. Therefore, it is preferable that the volume content of PTFE is equal to or larger than 15% and equal to or smaller than 60%. 
     FIG. 5  shows an example of an outline constitution of a laser working machine according to the embodiment. The laser working machine will be explained in reference to  FIG. 5 . 
   Laser beam  8  outputted from the laser oscillating apparatus explained in reference to  FIG. 1  is reflected by reflecting mirror  15  and is guided to a vicinity of work  16 . Laser beam  8  is converged into a high density energy beam by condenser lens  18  provided at inside of torch  17  and is irradiated to work  16  to process work  16 . Work  16  is fixed on work table  19  and torch  17  in which X axis motor  20  or Y axis motor  21  is controlled by a numerical control apparatus (not illustrated) is moved relative to work  16  to thereby process the work in a predetermined shape. Further, a predetermined shape may be processed by controlling to drive work table  19  by a numerical control apparatus. 
   Further, a predetermined shape may be worked by controlling to drive both of torch  17  and work table  19  by a numerical control apparatus. 
   INDUSTRIAL APPLICABILITY 
   The laser oscillating apparatus and the laser working machine of the invention can provide a highly reliable laser oscillating apparatus and a highly reliable laser working machine which can reduce running cost particularly by restraining a gas consumption amount and can stably be used over a long period of time and are industrially useful.