Abstract:
It is an object to provide a small-hole electrical discharge machining device to discharge the machining debris efficiently and to drill a small hole by electrical discharge machining at a high speed.

Description:
TECHNICAL FIELD 
     The present invention relates to a small-hole electrical discharge machining device for drilling a hole or holes in a relatively small or fine diameter in such a manner as flushing working fluid thereto. 
     BACKGROUND ART 
     Recently, a small-hole electrical discharge machining device is widely used for machining such a hole or holes as an initial hole for processing to thread a wire electrode of wire-cut electrical discharge machining, a hole of a component for an aircraft or an automobile and the like, because the small-hole electrical discharge machining device achieves the faster machining speed compared to a die sinking electric discharge machining device. 
     The small-hole electrical discharge machining device in such a manner as flushing the working fluid, is able to produce a small hole or holes some ten times as deep as the electrode diameter(s) at a high speed by electrical discharge machining in which an stick-shaped or pipe-shaped electrode(s) are applied and pulse voltage is applied to the portion between a tip surface of the electrode-for-machining and a segment of the workpiece opposite to the electrode to repeat pulse discharge with a electrode-for-machining cooled by supplying working fluid to a machining area of a workpiece. 
     Pressurized working fluid applied to the machining area (the machined hole) discharges machining debris generated by the electrical discharge machining, gas and the like from the entrance of the electrical discharge machined hole through an electrical discharge machining gap (the gap between a diameter of the electrode and a diameter of the hole of the workpiece). 
     Though the supply of the working fluid is needed for cooling the electrical discharge machining gap between the electrode and the workpiece and for promotion of discharge of the machining debris and gas and for the like, the supply of a great deal of the fluid to the electrical discharge gap is very difficult when machining a narrow and deep hole. Therefore, conventionally, supply pump pressure of the working fluid was increased and the pressurized fluid was attempted to supply, but it was difficult to supply and circulate the sufficient working fluid because the hole was narrow and deep. Furthermore, the machining debris has a tendency to be fused and accumulate as fused adhesive deposits at the corner portion of the opening in an entrance side of the machined hole 
     As shown in  FIG. 5 , in the prior art, the working fluid was jetted through the pipe electrode and toward the obliquely downward electrical discharge machining area by a jet nozzle of the working fluid disposed apart from the electrode. Specifically, also in the drilling electrical discharge machining, the jet from the side by employing the jet nozzle is adopted for discharge and removal of the machining debris in a periphery of the machining area. When applying the stick-shaped electrode, the working fluid is jetted with the jet nozzle disposed obliquely upward of the electrode, but at least a half of the opening in an entrance side of the machining area of the workpiece is submerged in the jetted working fluid, discharge openings of the machined chips are normally concentrated at a part in the opposite side of the jetting direction, and secondary discharge are generated frequently with such a low machining efficiency, such a machining system has a problem that the machined hole becomes ellipsoidal shape which have a long axis along with the jetting direction of the working fluid. 
     Furthermore, when the jet pressure of the working fluid is increased for the purpose of improvement of the discharge performance of the machining debris, the force vector which pushes the side of the electrode increases, the electrical discharge machining becomes unstable because the electrode is moved to the jet direction of the opening and is vibrated, and the overlap of the mechanical factor and the secondary discharge phenomenon for lack of the quantity of the working fluid causes the formation of the ellipsoidal hole. 
     In the Patent Literature 1, the small-hole electrical discharge machining device holding an upper edge portion of a thin pipe electrode with a electrode holder which can feed to a direction of Z axis and be driven rotatively, guiding a bottom portion of the pipe electrode, performing the electrical discharge machining by rotating the pipe electrode and feeding it to the direction to Z axis while jetting the working fluid into the electrical discharge machined hole from an upper edge of the pipe electrode through the inside of the pipe electrode, and separately from the above mentioned supply of the working fluid, flushing away chips adhered on a corner portion of the opening in the entrance side of the machined hole by jetting the working fluid from the jet nozzle provided at a plurality of parts obliquely upward of the electrical discharge machined hole at a pressure of at least 2 MPa or more, and preventing the generation of the fused adhesive deposits, is proposed. 
     In the Patent Literature 2, the small-hole electrical discharge machining device holding the thin pipe electrode by a hollow spindle which can feed in a direction of Z axis and be driven rotatively is proposed. In the Patent Literature 2, the electrode guide guiding the bottom portion of the pipe electrode shown in Patent Literature 1 isn&#39;t disclosed. The electrical discharge machining is performed by rotating the pipe electrode and feeding it in a direction of Z axis while supplying the working fluid into the electrical discharge machined hole in a jet flow condition from the upper edge of the pipe electrode through the inside of the pipe electrode. The machining debris are discharged from the electrical discharge machining gap between the electrode and the workpiece by applying the working fluid through the inside of the pipe electrode in a jet condition into the electrical discharge machined hole so that the working fluid passed in the pipe electrode is pulsated at a frequency of 1.5 Hz or more. 
     In Patent Literature 3 and 4, the supply system of the pressurized working fluid in which the pressurized working fluid is supplied so as to surround the stick-shaped electrode or the pipe-shaped electrode, and in case of the pipe electrode, supplying the working fluid by way of its tubular space is also applied jointly, is adopted. 
     In the Patent Literature 3, the small-hole electrical discharge machining device which performs the small-hole electrical discharge machining by holding the upper edge of the stick-shaped or the pipe-shaped electrode with the electrode holder which can feed in a Z axis direction and be driven rotatively, and guiding the bottom portion of the pipe electrode with the electrode guide, supplying the pressurized working fluid from the upper edge of the electrode to the electrode holder with the circumference of the electrode surrounded, and supplying it in a jet condition from the electrode holder to the bottom edge of the electrode holder through a guide opening trough which the electrode passes arranged on the electrode holder with the circumference of the electrode surrounded, is proposed. 
     In the Patent Literature 4, the small-hole electrical discharge machining device which performs the small-hole electrical discharge machining by holding the upper edge of the stick-shaped or the pipe electrode with the electrode holder which can feeds in a Z axis direction and be driven rotatively, and guiding the bottom portion of the pipe electrode with the electrode guide, supplying the pressurized working fluid from the upper edge of the electrode to the electrode holder with the circumference of the electrode surrounded, getting mixed high pressure gas in the pressurized working fluid which is supplied to the electrode holder with the ejector mechanism arranged in the electrode holder, supplying the pressurized working fluid including the gas to the bottom edge of the electrode through the guide opening of the electrode guide with the circumference of the electrode surrounded, securing the workpiece in the vacuum suction box, performing the electrical discharge machining with the inside of the box vacuuming by suctioning from the bottom portion of the box with a vacuum suction apparatus, is proposed. 
     CITATION LIST 
     Patent Literature 
     [PATENT LITERATURE 1] Japanese Patent Laid-Open Publications No. H05-169322 
     [PATENT LITERATURE 2] Japanese Patent Laid-Open Publications No. H05-185326 
     [PATENT LITERATURE 3] Japanese Patent Laid-Open Publications No. 2001-287119 
     [PATENT LITERATURE 4] Japanese Patent Laid-Open Publications No. 2004-1156 
     SUMMARY OF INVENTION 
     Technical Problem 
     According to the art shown in the Patent Literature 1 and 2, when performing the electrical discharge machining with the pipe electrode which diameter is 0.2 mm or less, under the influence of viscosity of the working fluid and friction of the passageway, because the pressurized working fluid supplied via the passageway in the electrode is reduced, and the amount of flow in the electrical discharge machining gap between the inner surface of the machined hole and the pipe electrode decreases, therefore the discharge of the machined chips by the pressurized working fluid becomes defective. Due to the defect, secondary discharge and/or short circuit occurs, the electrical discharge machining speed becomes late drastically, and a defect which the high speed machining of the feature of this kind of the electrical discharge machining device can&#39;t be performed. Therefore when a pressure of the working fluid is increased for the purpose of increasing the amount of jet flow of the working fluid, the machining becomes impossible because the originally straight-shaped pipe is deformed and/or deflected due to the unequal wall thickness of the tube of the pipe electrode. 
     Furthermore, when applying the stick shaped electrode with jetting the working fluid from opening from an oblique direction toward the opening in an entrance side of the machined hole, when the diameter of the electrode is equal to or less than 0.2 mm, the discharge of the machined chips also becomes defective and the above mentioned defect also occurs similarly to in the case of the pipe-shaped electrode. 
     In the patent Literature 4, it is indicated that the art shown in the Patent Literature 3 has a problem that the electrode guide is clogged for intrusion of the contaminated fluids from the machining area into the electrode guide, and by which the long and stable movement of the electrode is inhibited, and the art shown in the Patent Literature 4 can attain the problem. According to the art shown in the Patent Literature 3, the high pressure working fluid  22   c  flowing down from the above electrode holder becomes less pressure by exposing to the atmosphere and enters in the funnel portion of the electrode guide, and the extrusion pressure by the working fluid accumulated in the funnel portion let the working fluid flow down from the electrode guide toward the electrical discharge machined hole. Since the working fluid without high jetting pressure covers the surface of the electrode thickly, flows down, and radiates to the electrical discharge machining hole so that the working fluid expands to larger area than the diameter of the hole, the pressurized working fluid isn&#39;t entered and supplied sufficiently to the electrical discharge machining gap and is also accumulated around the hole, and as the pressurized working fluid is as the wall inhibiting the discharge of the machining debris generated by the electrical discharge machining from the electrical discharge machining gap, the machining debris aren&#39;t discharged sufficiently. This caused to long machining time and inefficiency. 
     According to the art disclosed in the Patent Literature 4, because the pressurized working fluid radiated from the electrode guide toward the electrical discharge machined hole comprises high pressure gas, as the pressurized working fluid is expanded largely before reaching the machined hole, the high pressure working fluid isn&#39;t entered and supplied sufficiently to the electrical discharge machining gap, and the machining debris aren&#39;t discharged sufficiently. This caused to long machining time and inefficiency. 
     Furthermore, when machining the machined hole which depth is ten times larger than its diameter by applying the stick-shaped electrode which diameter is equal to or less than 0.15 mm, as appropriate, the jumping movement of the electrode is applied jointly to discharge the machining debris in conjunction with jetting the working fluid from the side by the opening by the nozzle, however the machining isn&#39;t performed while the machining gap is enlarged by the jump, as it causes reduction of machining efficiency, there is a need for the supply system which enables to reach the sufficient amount of the pressurized working fluid to the bottom portion of the hole even when the depth of the machined hole is deep. 
     As shown in  FIG. 5 , by the conventional system jetting the working fluid from one direction by applying the jet nozzle of the working fluid or flowing water from the upper portion of the electrode, as the diameter of the nozzle or the diameter of the flowing water is large, the discharge of the machining debris are difficult because the working fluid surrounding the electrode becomes the cover when discharging the working fluid, and the machining efficiency becomes lower. In particular, the conventional system jetting the working fluid by applying the jet nozzle of the working fluid jets in an intended direction between the workpiece and the electrode, but as the jetting force is split in vector directions between the force pressing to the side of the electrode and the force along the direction of downward movement of the electrode, and the part of the force vector along the direction of downward movement of the electrode goes in the machined hole, and affect the discharge of the machining debris. Therefore the discharge effect of the machining debris by the initial jetting force of the working fluid is greatly reduced. 
     The present invention is invented in view of the above mentioned points, and it is an object of the present invention to provide the small-hole electrical discharge machining device which enables to supply the working fluid to the electrical discharge machining area so that the machining debris is smoothly discharged from the electrical discharge machining gap by the pressurized working fluid. 
     Solution to Problem 
     In order to achieve the above mentioned object, a small-hole electrical discharge device of the present invention comprises an electrode guide guiding a lower portion of a electrode-for-machining in a Z axis direction through an interposed fluid layer of working fluid in the vicinity of a workpiece, and wherein the electrode-for-machining is a stick-shaped electrode or a pipe-shaped electrode, a high pressure working fluid acceptance chamber accepting a high pressure working fluid into a housing block securing the electrode guide in the vicinity of the workpiece, and a high pressure working fluid jet opening disposed at a lower edge of high pressure working fluid acceptance chamber and supplying a jet flow of the high pressure working fluid to a electrical discharge machining gap so that the jet flow is not expanded as much, wherein a diameter of the high pressure working fluid jet opening is regulated in such a manner that the diameter of the high pressure working fluid jet opening is slightly larger than a diameter of the electrode, and wherein the diameter of the high pressure working fluid jet opening is approximately equal to a diameter of an entrance portion of the electrical discharge machined hole produced by a electrical discharge machining. 
     The small-hole electrical discharge device of the above mentioned invention retains an upper portion of the stick-shaped or the pipe-shaped electrode-for-machining with the electrode holder, and the electrode guide guides the lower portion of the electrode-for-machining in the Z axis direction with the layer of the high pressure working fluid interposed in the vicinity of the workpiece. Additionally, the high pressure working fluid drawn in the high pressure working fluid acceptance chamber is jetted from the high pressure working fluid jet opening. Since the high pressure working fluid jet opening is regulated so that the diameter of its opening slightly larger than the diameter of the electrode-for-machining, and the high pressure working fluid is jetted so that the jet flow is not expanded as much and surrounds the circumferential surface of the electrode-for-machining, the high pressure working fluid is supplied to the electrical discharge machining gap deeply. Therefore, when the electrode-for-machining is fed relatively to the workpiece in the Z axis direction and the electrical discharge machining is performed, hereby the machining debris generated at the bottom portion of the electrical discharge machined hole are incorporated in the working fluid supplied deeply to the electrical discharge machining gap and are carried away from the electrical discharge machining gap to the entrance portion of the electrical discharge machined hole smoothly. As the jet flow which reaches the periphery of the entrance portion of the electrical discharge machined hole on the surface of the workpiece hits strongly on the working fluid including the machining debris and just flown from the electrical discharge machining gap to the periphery of the entrance portion of the electrical discharge machined hole, as the working fluid becomes misty and is scattered by the hit impact, puddle of the working fluid doesn&#39;t occur at the periphery of the entrance portion of the electrical discharge machined hole, hereby fused adhesive deposits are not formed at the edge of the entrance portion of the electrical discharge machined hole, and the machining debris generated at the bottom portion of the electrical discharge machined hole are discharged outside smoothly without the machining debris accumulated in the electrical discharge machining gap. Additionally, as the electrode-for-machining is cooled sufficiently, current supplied to the electrode-for-machining can be raised more than ever before drastically, the electrical discharge machining time can be shorten several times shorter than ever before, and the electrical discharge machining efficiency is raised drastically. Furthermore, at the time of finishing drilling, as the jet flow from the high pressure working fluid jet opening penetrates the electrical discharge machining gap, because the machining debris attached to the lower edge of the electrode-for-machining are carried away, the fused adhesive deposits are not formed at the lower edge of the electrode-for-machining. 
     Furthermore, the small-hole electrical discharge machining device comprises a shaft retaining the electrode-for-machining, a working fluid distribution chamber drawing the working fluid into the shaft and having jet opening, wherein the electrode-for-machining is passed through the working fluid distribution chamber, a fluid tank disposed above the electrode guide, accepting the pressurized working fluid and distributing the pressurized working fluid, wherein the pressurized working fluid is jetted from the jet opening of the working fluid distribution chamber and surrounds the electrode-for-machining and flows down, and wherein a passageway of the electrode-for-machining may be communicated with the fluid tank when the electrode-for-machining is a pipe-shaped electrode, and a fluid reserve tank accepting a overflowed fluid from the fluid tank through a overflowed fluid tube  52 . According to this composition, the portion of the electrode-for-machining from the electrode holder to the electrode guide can be cooled with the portion surrounded by the jet flow of the high pressure working fluid, and the high pressure working fluid can be supplied to the internal space of the electrode when the electrode-for-machining is a pipe electrode. Additionally, a great amount of the high pressure working fluid can be supplied from the working fluid pump to the electrode holder, and a great amount of the jet flow of the high pressure working fluid can jet from the electrode holder with the electrode-for-machining which is a the stick-shaped electrode or the pipe-shaped electrode surrounded, and the portion of the electrode-for-machining from the electrode holder to the fluid tank is cooled sufficiently. About the electrode-for-machining, cooling the portion to perform the electrical discharge with the workpiece apart from the lower edge of the electrode also enables to flow thigh current to the electrode-for-machining. 
     Preferably, in the above mentioned embodiment, the working fluid in the fluid reserve tank is split so as to be the pressurized working fluid and the high pressure working fluid, and is circulated by a working fluid pump. 
     According to this composition, the pressurized working fluid and the high pressure working fluid can be supplied by pumping up the working fluid reserved in the fluid reserve tank with only one pump, and the pressure of the pressurized working fluid and the pressure of the high pressure working fluid may be set up after bifurcation, the pressure setting control of the working fluid and the control of the amount of flow are easily, and the circulation system of the working fluid can be simplify. 
     Preferably, in the above mentioned embodiment, the small-hole electrical discharge machining device further comprises a pressure setting measure setting fluid pressure of the high pressure working fluid drawn in the high pressure working fluid acceptance chamber so as to be equal to or more than 3 MPa, and setting pressure of jet flow in such a condition as surrounding the electrode-for-machining between the electrode guide and a lower edge of the electrode so as to be equal to or more than 3 MPa. 
     According to this composition, as the fluid pressure of the high pressure working fluid is 3 MPa or more, even in the machining step in which the electrical discharge machined hole becomes deep, the high pressure working fluid can be supplied to the electrical discharge machining gap between the inner surface of the electrical discharge machined hole and the electrode-for-machining smoothly, the machining debris generated at the bottom of the electrical discharge machined hole can be carried out. Therefore, even if the electrical discharge machined hole is deep and small, it can be machined in a short time. 
     Preferably, in the above mentioned embodiment, the high pressure working fluid acceptance chamber is a hollow portion of the electrode guide, and the high pressure working fluid is fed to the hollow portion through a fluid passageway arranged in the housing block holding the electrode guide with the lower edge of the electrode guide exposing, and wherein the high pressure working fluid jet opening is arranged at a lower edge of the high pressure working fluid acceptance chamber of the hollow portion of the electrode guide. According to this composition, a great amount of the high pressure working fluid can be drawn in the hollow portion of the electrode guide, the jet flow of the high pressure working fluid which is jetted from the high pressure working fluid jet opening at the lower edge of the tubular space is supplied from the high pressure working fluid jet opening having a diameter approximately equal to the diameter of the entrance portion of the electrical discharge machined hole to the electrical machining gap so that the jet flow is not expanded as much with the electrode-for-machining surrounded at the portion from the high pressure working fluid jet opening to the lower edge of the electrode. Therefore, even the electrical discharge machined hole is deep and small, it can be machined in a short time. 
     Preferably, in the above mentioned embodiment, the high pressure working fluid acceptance chamber is disposed in the housing block holding the electrode guide and is extended along the circumference of the electrode guide to the lower edge of the electrode guide, and wherein the high pressure working fluid jet opening is arranged in the vicinity of the lower side of the electrode guide of the high pressure working fluid acceptance chamber concentrically. According to this composition, a great amount of the high pressure working fluid can be drawn in the space of the circumference of the electrode guide, the jet flow of the high pressure working fluid jetted from the high pressure working fluid jet opening at the lower edge of the high pressure working fluid acceptance chamber is supplied to the electrical discharge machining gap so that the jet flow jetted from the high pressure working fluid jet opening which has the diameter approximately equal to the diameter of the entrance portion of the electrical discharge machined hole and the jet flow isn&#39;t expanded as much. Therefore, even if the electrical discharge machined hole is deep and small, it can be machined in a short time. 
     Preferably, in the above mentioned embodiment, the small-hole electrical discharge machining device further comprises an air nozzle jetting air or inactive gas for blowing away misty scattered working fluid and/or a liquefaction segment including machining debris generated before and/or after machining, and a jetted working fluid recovery equipment for recovering the scattered working fluid and/or the liquefaction segment blown away. 
     According to this embodiment, the misty spattered working fluid and the liquefied segment including the machining debris is not interrupted, the working fluid including the machining debris is discharged from the electrical discharge machining gap smoothly, and it prevents forming the fused adhesive deposit at the edge of the entrance portion of the electrical discharge machined hole. 
     Advantageous Effects of Invention 
     According to the present invention, it enables to provide the small-hole electrical discharge machining device in which high pressure working fluid can be supplied at close range to the workpiece, to a electrical discharge machining gap deeply and in large amounts along the circumference of the electrode, by reducing the supply to the periphery of the entrance potion of the electrical discharge machined hole on the surface of the workpiece, by which the machining debris generated by the electrical discharge machining at the bottom portion of the electrical discharge machined hole can be discharged smoothly from the electrical discharge machining gap. Therefore, even when drilling a hole or holes having a comparatively small or fine diameter under atmospheric working conditions by electrical discharge machining at high speed, the machining debris can be discharged from the electrical discharge machining gap smoothly, and it enables to perform the stable electrical discharge machining at extremely high speed and to shorten the machining time significantly, by which it enables to improve the work efficiency and to reduce costs significantly for machining of the comparatively small hole on mass production line. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING 
         FIG. 1  A view illustrated compositions of one embodiment of the small-hole electrical discharge machining device of first embodiment of the present invention. 
         FIG. 2  An enlarged cross-sectional view of the main section of the small-hole electrical discharge machining device illustrated in  FIG. 1 . 
         FIG. 3  An enlarged cross-sectional view of the main section of the small-hole electrical discharge machining device illustrated in  FIG. 1 . 
         FIG. 4  An enlarged cross-sectional view of the main section showing jetting condition of the working fluid of the small-hole electrical discharge machining device illustrated in  FIG. 1 . 
         FIG. 5  An enlarged cross-sectional view of the main section showing jetting condition by the jet opening of working fluid at the electrical discharge machining for drilling. 
         FIG. 6  An enlarged cross-sectional view of the guide applied to the small-hole electrical discharge machining device of this invention as the working fluid jet guide and the electrode guide for the small-hole electrical discharge machining device. 
         FIG. 7  Perspective views of five embodiments of the electrode guides adopted in the small-hole electrical discharge machining device illustrated in  FIG. 1 . 
         FIG. 8  An enlarged cross-sectional view of a main section of the small-hole electrical discharge machining device of second embodiment of the present invention. 
         FIG. 9  A cross-sectional view showing the flow of the high pressure working fluid in the main section of the small-hole electrical discharge machining device illustrated in  FIG. 8 . 
         FIG. 10  A transverse cross sectional view of the electrode guide at the A-A section of the main section of the small-hole electrical discharge machining device illustrated in  FIG. 8 . 
         FIG. 11  Perspective views of two embodiments of the electrode guides adopted in the small-hole electrical discharge machining device illustrated in  FIG. 8 . 
         FIG. 12  A graph showing data on appropriate distance of the distance between the electrode guide and the workpiece under machining condition at low machining speed. 
         FIG. 13  A graph showing an experimental result relating to performance changes against working fluid jet pressure changes. 
         FIG. 14  A graph showing an experimental result relating to machining performance changes against working fluid pressure changes. 
         FIG. 15  A graph compared between the conventional normal machine and the prototype machine of the present invention. 
         FIG. 16  A graph showing a relationship between changes of electrode-guide GAP (one side μm) and machining performance relating to electrical discharge machining with the device of the present invention. 
         FIG. 17  A graph compared the progress statuses of electrical discharge machining with the conventional device and the device of the present invention. 
         FIG. 18  A graph showing changes of wear-out ratio against changes of machining depth by the electrical discharge machining device and changes of machining speed. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Following, the small-hole electrical discharge machining device of one embodiment of the present invention is explained by reference to the drawings. 
     [First Embodiment] 
       FIG. 1  is a view of an entire composition of a first embodiment of a small-hole discharge machining device,  FIG. 2  is an enlarged cross-sectional view of main section, and  FIG. 3  is a further enlarged cross-sectional view of the main section. 
     The small-hole electrical discharge machining device  1  of this present embodiment comprises a rotating shaft  8  arranged movably in a Z axis direction and rotatably and accepts and holds an upper portion of an electrode holder  10 , the electrode holder  10  which upper portion is accepted and held by the rotating shaft  8  and holds an upper edge of an electrode-for-machining  11  which is a stick-shaped electrode or a pipe-shaped electrode as a chuck unit, an electrode guide  13  guiding a lower edge of the electrode  11  through a fluid layer of working fluid in the Z axis direction, a high pressure distribution chamber  8   a  arranged in the rotating shaft  8  and drawn pressurized working fluid from a working fluid pump  21  through a rotating joint  5 , a fluid tank  15  arranged above a housing block  17  accepting and holding the electrode guide  13  and accepts the working fluid jetting from a jet opening  8   b  at a lower edge of the pressurized working fluid distribution chamber  8   a  and flowing down along and surrounding the electrode-for-machining  11 , a high pressure fluid acceptance chamber  9  in housing block  17  being communicated with the fluid tank  15  and accepting the high pressure working fluid  22   c  from the working fluid pump  21 , and a high pressure working fluid jet opening  9   a  arranged at an lower edge of the high pressure working fluid acceptance chamber  9  and supplying jet flow of the high pressure working fluid  22   c  to an electrical discharge machining gap so that the jet flow of the high pressure working fluid having a diameter which is approximately equal to a diameter  35   a  of an entrance portion of the electrical discharge machined hole arranged in a workpiece  14  by the small-hole electrical discharge machining doesn&#39;t become expanded as much. Herein as the rotating shaft is used as a shaft in the present embodiment, which is not bound by it, the shaft may be a non-rotating shaft. 
     The small-hole electrical discharge machining device  1  of this embodiment comprises, as a circulation system of the working fluid, a working fluid pump  21 , a pressure adjustment valve  46  for pipe jet, a pressure adjustment valve  45  for the working fluid jet guide, a fluid reserve tank  40 . The small-hole electrical discharge machining device  1  of this embodiment also comprises, as a power-supply control system, a control unit  44 , a servo unit  39 , a pulsed power supply  36  for machining, NC equipment  42 , and a motor driver  43 . 
     The electrode holder  10  is held by the rotating shaft  8  at a head section  25 . The head section  25  is held on a protruded portion of an upper edge of a column  24  of a frame, which is composed of a base platform  23  and a column  24  vertically arranged on the base platform  23 . 
     The head section  25  includes L-shaped frame composed of Z axis plate  26  secured to the column  24  and a guide fixed plate  12  having an edge secured to a lower edge of the Z axis plate  26 , a rail  27  arranged on the Z axis plate  26 , a slide  28  engaged to the rail  27  and guided to the Z axis direction (Vertical direction), and a lifting table  7  of which proximal edge is secured to the slide  28  and extended in a horizontal direction, the lifting table  7  is movable in the Z axis direction (Vertical direction). 
     The head section  25  comprises a driving measure which moves the lifting table  7  in the Z direction at an upper edge of the Z axis plate  26 . Namely, a feed screw axis  34  is attached rotatably and immovably in an axial direction to a mounting plate  29  having one edge secured to the upper edge of the Z axis plate  26  with its one edge and extending horizontally, and the feed screw axis  34  is screwed with a outrunner secured in an penetrating opening formed in the lifting table  7 . Additionally, a servo motor  3  is arranged and a rotation of the servo motor  3  is transmitted to the feed screw  34  through a pulley  31  attached to a output axis  33  of the servo motor  3 , a belt  32 , a pulley  30  attached to the feed screw  34 . Therefore, the lifting table  7  is guided along the rail  27  and moved in the Z axis direction by the servo motor  3  rotating the feed screw  34 . The electrode holder  10  arranged at a lower edge of the lifting table  7  and holds the upper edge of the electrode  11  when inserting an upper edge of the electrode-for-machining  11  into the electrode holder  10  upwardly, and the electrode-for-machining  11  is rotated by the motor  4  arranged on the lifting table  7 . 
     The workpiece  14  is positioned and secured on the X-Y movable table equipment  62  arranged on the base platform  23 . The X-Y moving table  62  has a X-axis motor MX and a Y-axis motor MY actuated by driving signals from the motor driver  43  generated in conformity with signals from the NC equipment  43 , the workpiece  14  is moved to position in the X-Y plane perpendicular to the direction of Z axis, and a position for drilling of the workpiece  14  can be located opposite to the electrode-for-machining  11  accurately. 
     When the electrode-for-machining  11  is in the vicinity of the entrance surface of workpiece  14  by descending the electrode  11  in the Z axis direction toward the surface, voltage depression of a pulse for machining occurs and an original point for machining is set. When the electrode-for-machining  11  and the workpiece  14  are positioned precisely, the electrical discharge machining can start, and when the electrode-for-machining  11  and the workpiece  14  are not positioned precisely, the electrical discharge machining starts after the positioning in X-Y plane. 
     When the electrode-for-machining  11  is a pipe electrode, the pressurized working fluid  22   b  drawn in the pressurized working fluid distribution chamber  8   a  supplies directly to the bottom portion of the electrical discharge machined hole  14   a  from a lower edge of the electrode  11  through a pipe hollow passageway. A lower portion of the pressurized working fluid distribution chamber  8   a  is a jet opening  8   b  in the vicinity of an electrode holding surface of the electrode holder  10 , and the jet opening  8   b  is bored in a longitudinal direction, even if the electrode-for-machining  11  is either the pipe electrode or the stick-shaped electrode, the jet opening  8   b  makes a concentrated flow of the pressurized working fluid having a relatively large diameter at its lower edge, and the flow surrounds and cools the electrode-for-machining  11  down to the electrode guide  13 . The flow of the pressurized working fluid  22   b  is accepted in the fluid tank  15 . 
     The fluid tank  15  is supported by an upper surface of a protruded edge of the guide fixed plate  12 , and accepts the working fluid surrounding the electrode-for-machining  11  and flowing down and jetted from the pressurized working fluid distribution chamber  8   a . The fluid tank  15  is fluid communicated with the fluid reserve tank  40  arranged underneath by an overflowed fluid hose  52 , and the working fluid overflows to the fluid reserve tank  40 . Even if the fluid tank  15  has a requisite volume, and a large amount of the pressurized working fluid is drawn to the pressurized working fluid distribution chamber  8   a  and a large amount of the pressurized working fluid is also accepted to the fluid tank  1 , the fluid surface level is kept constant by flowing down the overflowed fluid from the fluid tank  15  to the fluid reserve tank  40 . 
     If an upper portion of the electrode-for-machining  11  than an upper guiding piece  13   c  is in a gas atmosphere, the electrode-for-machining  11  is burnt out when the electrode is applied much electrical current. Furthermore, because a jet of the high pressure working fluid  22  occurs from and above the clearance between the upper guiding piece  13   c  and the electrode, when a distance between the electrode holder  10  and the upper guiding piece  13   c  is relatively long, the electrode is vibrated and inflected. Therefore, as the fluid tank  15  is arranged, the high pressure working fluid  22   c  in the fluid tank  15  absorbs the jetting force of the working fluid over the guide in an upward direction, and as the fluid tank  15  is in an overflow manner, the stable electrical discharge machining can be performed at high speed by applying much electrical current to the electrode-for-machining  11  even in a gas atmosphere. 
     As shown in  FIG. 6 , the electrode guide  13  is formed so as to be a hollow body, and the high pressure working fluid acceptance chamber  9  is the hollow portion of the electrode guide  13  in this embodiment. The passageway  12   a  is arranged in the guide fixed plate  12  as a high pressure working fluid drawing passage so as to draw the high pressure working fluid  22   c  into the high pressure working fluid acceptance chamber  9  which is the hollow portion, a fluid passageway  17   a  is arranged in the housing block  17  secured on a bottom surface of the protruded edge of the guide fixed plate  12 , a penetrated passageway  13   a  is arranged and is communicated with the high pressure working fluid acceptance chamber  9  which is communicated with the fluid passageway  17   a  and is the hollow portion in a middle of the side of the electrode guide  13 . Additionally, as a lower guide piece  13   b  having the high pressure working fluid jet opening  9   a  is arranged at a lower edge of the high pressure working fluid acceptance chamber  9  which is the hollow portion of the electrode guide  13 , as shown in the FIG. 3 , the housing block is accepted the electrode guide  13  with the lower edge of the electrode guide  13  exposed. That is to say, a head cover  17   b  is exposed the lower edge portion of the electrode guide  13 . Herein, the penetrated passageway  13   a  is a circular, rectangle, or elliptical cross-section, and has not only a role drawing the pressurized high pressure working fluid  22   c , but also a role as an outlet for removal and discharge of the electrode  11  broken in the electrode guide  13  and/or the machining debris, and the penetrated passageway  13   a  is preferred to form as large as possible within the range which the mechanical strength of the electrode  13  permits. 
     As shown in  FIG. 6 , the high pressure working fluid acceptance chamber  9  is formed in several times larger diameter than the diameter of the electrode, and the lower guide piece  13   b  and the upper guide piece  13   c  are secured concentrically to the hollow portion, as the lower edge and the upper edge are squeezed. In this embodiment, the lower guide piece  13   b  holding the high pressure working fluid jet opening  9   a  is passed the electrode  11  therethrough, is arranged in a slightly larger diameter than the diameter of the electrode so that a clearance equal to or less than e.g. 2 μm is arranged around the electrode-for-machining  11 , has an upper edge surface formed in a funnel shape, has a function guiding the electrode-for-machining  11  in the Z axis direction in such a manner that a fluid layer of the high pressure working fluid  22   c  is interposed in the fine clearance, and jets the high pressure working fluid  22   c  in the hollow portion in a downward direction with such a guiding function by the fluid layer so as to be a fine filmy jet flow surrounding the electrode-for-machining  11 . Therefore, since the clearance between the opening of the lower guide piece  13   b  passed the electrode-for-machining  11  through and the electrode-for-machining  11  is the high pressure working fluid jet opening  9   a , and the diameter of the high pressure working fluid jet opening  9   a  is regulated so as to be slightly larger diameter than the diameter of the electrode-for-machining  11 , the small-hole electrical discharge machining device has a radiation guide function which is supplied the jet flow of the high pressure working fluid  22   c  having a diameter approximately equal to a diameter  35   a  of the entrance portion of the electrical discharge machined hole by the small-hole electrical discharge machining is supplied to the electrical discharge machining gap so that the jet flow is not expanded as much. 
     The upper guide piece  13   c  is passed the electrode-for-machining  11  through, is formed in a slightly larger diameter than the diameter of the electrode so that a clearance is arranged around the electrode-for-machining  11 , has an upper edge surface arranged in a funnel shape, has a function guiding the electrode-for-machining  11  in the Z axis direction in such a manner that a fluid layer of the high pressure working fluid  22   c  is interposed in the fine clearance. An inner diameter of the upper guide piece  13   c  may as well be somewhat larger than an inner diameter of the lower guide piece  13   b.    
     As shown in  FIG. 1 , the working fluid  22  in the fluid reserve tank  40  is pumped up by the working fluid pump  21  and is circulated so that the working fluid  22  bifurcates the pressurized working fluid  22   b  supplied to the pressurized working fluid distribution chamber  8   a  and the high pressure working fluid  22   c  supplied to the high pressure working fluid acceptance chamber  9 . That is to say, the working fluid  22   a  supplied from the working fluid pump  21  is controlled its pressure to be the pressurized working fluid  22   b  by the pressure adjustment valve  46  for pipe jet, the pressurized working fluid  22   b  is drawn in the pressurized working fluid distribution chamber  8   a  in the electrode holder  10 , the bifurcated flow of the working fluid  22   a  supplied from the working fluid pump  21  is controlled its pressure by the pressure adjustment valve  45  for the working fluid jet guide to be high pressure working fluid  22   c  so that its pressure becomes higher than the fluid pressure of the pressurized working fluid  22   b , the high pressure working fluid  22   c  is drawn to the high pressure working fluid acceptance chamber  9  which is the hollow portion of the electrode guide  13 . It is largely effective for supplying the high pressure working fluid  22   c  to the electrical discharge machining gap  35   b  deeply and discharging the machining debris that the fluid pressure of the high pressure working fluid  22   c  is equal to or more than 3 MPa, and the fluid pressure of the jet flow in such a condition that the high pressure working fluid  22   c  surrounds the electrode  11  from the electrode guide  13  to the lower edge of the electrode is equal to or more than 3 MPa. Therefore, the pressure adjustment valve  45  for the working fluid jet guide is set at the pressure equal to or more than 3 Mpa. 
     When the pressure of the high pressure working fluid  22   c  is equal to or more than 3 Mpa, the working fluid jet which passes through the electrode-for-machining  11  in the lower guide piece  13   b  gives momentum which turns the working fluid into a spray to the high pressure working fluid  22   c , when the working fluid jet hits on a surface of a metallic material and the like within 10 mm in the jet direction. The fluid tank  15  is disposed above the upper guide piece  13   c , into which the high pressure working fluid flows. The level of working fluid in the fluid tank  15  changes corresponding to the fluid pressure of the high pressure working fluid  22   c , and is set so that a portion of the electrode-for-machining  11  from the electrode holder  10  to the upper guide piece  13   c  is submerged. Therefore, the small-hole electrical discharge machining device has a function preventing from electrode vibration and electrode inflection occurs when the electrode moving vertically for machining, and cooling the portion of the electrode from the electrode holder  10  to the upper guide piece  13   c . In the above mentioned method for electrode cooling, the electrical discharge machining device can triplicate current in the electrode-for-machining  11  to set the machining pulse in comparison with the conventional one, and can perform the drilling electrical discharge machining at high speed. 
     The pressurized working fluid distribution camber  8   a  arranged in the electrode holder  10  jets the pressurized working fluid  22   b  supplied from the working fluid pump  21  toward the electrode guide  13  with the electrode  11  retained by the electrode holder  10  surrounded, and the pressurized working fluid is supplied to the inner space of the electrode when the electrode-for-machining  11  is the pipe-shaped electrode. 
     The high pressure acceptance chamber  9  arranged in the electrode guide  13  is accepted the pressurized working fluid of the jet flow which reaches the electrode guide  13  so that the electrode-for-machining  11  is surrounded from the electrode holder  10  to the electrode guide  13  by the jet flow, accepts the high pressure working fluid  22   c  of higher pressure than the pressurized working fluid through a high pressure working fluid supply channel  51 , and makes the high pressure working fluid  22   c  into jet flow which surrounds the portion of the electrode-for-machining  11  from the electrode guide  13  to the lower edge of the electrode. The high pressure working fluid acceptance chamber  9  has the high pressure working fluid jet opening  9   a  which has a diameter approximately equal to the diameter  35   a  of the entrance portion of the electrical discharge machined hole arranged by the small-hole electrical discharge machining, and has function which the jet flow of the high pressure working fluid  22   c  jetted from the high pressure working fluid jet opening  9   a  supplied to the electrical discharge machining gap  35   b  so that the jet flow is not expanded as much. 
     The small-hole electrical discharge machining device comprises air nozzle  16  which jets air or inert gas to blow away the misty scattered working fluid and the liquefaction segment generated before and after machining including the machining debris, a jetted working fluid recovery equipment  20  for recovering the scattered working fluid and the liquefaction segment blown away by the air nozzle  16 . The jetted working fluid recovery equipment  20  for recovering the scattered working fluid is secured on the lower surface of the guide fixed plate  12 , and the air nozzle is secured in a similar way. The small-hole electrical discharge machining device comprises a pressurized air supply equipment  47  (e.g. air compressor), an air blow volume adjustment valve  48 , an air suction flow volume adjustment valve  49 , a vacuum generator  50 , in order to jet the air or the inert gas from the air nozzle  16  and suctioning negative pressure suction with the jetted working fluid recovery equipment  20 . In the event inert gas is jetted from the air nozzle  16 , an air cylinder not shown in the drawings is provided. Moisture trapped by the vacuum generator  50  flows down to the fluid reserve tank  40 . The pressurized air supply equipment  47  is controlled by control signals from a decision processing measure  44   c  of a control unit  44 . 
     The pulsed power supply  36  for machining is electrically connected to the rotating shaft  8  by the conducting brush  6  through an output line  37  so that the electrode  11  is an anode and the workplace  14  is a cathode, and is electrically connected to the workpiece  14  thorough an output line  38 , thereby pulse voltage for machining is applied to the electrical discharge machining gap  35   b  located between a lower edge surface of the electrode-for-machining  11  and a portion opposite to the electrode lower edge surface of the workplace  14 . Herein, the electrode-for-machining  11  may be connected so as to reverse their polarities depending on their materials. 
     During the electrical discharge machining, the working fluid is jetted, the electrode-for-machining  11  is moved in the Z axis direction to the workpiece  14  by servo unit  39 , and the electrical discharge machining gap  35   b  is kept an appropriate gap. The servo unit  39  has a servo circuit and a servo driver and inputs the pulse outputted from the pulsed power supply  36  for machining on the basis of signals from the NC equipment  42 , and the servomotor  3  is controlled and driven. The displacement of the lifting table  7  moved up and down by rotary drive of the servo motor  3  is detected as the amount of pulse by a rotary encoder  2 , the amount of pulse is inputted to an electrode movement position measuring means in the control unit  44 , and the movement position of the electrode is constantly detected and the data is inputted or is compared to a memory processing and a comparing processing measure  44   b.    
     The control unit  44  comprises an electrode movement position measuring means  44   a , a memory processing and a comparing processing measure  44   b  using a microcomputer, and the decision processing measure  44   c  using a microcomputer. 
     The electrode movement position measuring means  44   a  detects the displacement (the displacement of the electrode) of the lifting table  7  which is moved up and down by the servo motor  3  with the rotary encoder  2 , and inputs the amount of outputting pulse corresponding to the displacement, thereby the present position of the lower edge of the electrode performing the electrical discharge machining is constantly detected, and a signal of position is outputted to the memory processing and the comparing processing measure  44   b.    
     The memory processing and a comparing processing measure  44   b  comprises a measure for comparing an initial position the working fluid jet which passes through the inside of the pipe-shaped electrode, a measure for comparing an jet starting position of the high pressure working fluid  22   c  from the high pressure working fluid opening  9   a , a measure for comparing a machining terminating position, a measure for comparing a jet stop position for the working fluid from the electrode, and a measure for comparing a jet stop position for the high pressure working fluid  22   c  from the high pressure working fluid opening  9   a , thereby necessary control signals are outputted to the decision processing measure  44   c  when the thresholds set up in each of the measures are equal to the signals from the electrode movement position measuring means  44   a.    
     The decision processing measure  44   c  comprises a shaft feeding and machining control measure, a pressurized air supply time control measure, a measure to decide the increase or decrease of a working fluid pump pressure, a pressure adjustment valve control measure of the pressurized working fluid, and a pressure adjustment valve control measure of the high pressure working fluid  22   c , thereby control signals are outputted to each of the working fluid circulation system, the pressurized air supply system and the power source control system. That is to say, the decision processing measure  44   c  outputs a actuation and/or stop signal for working pump  21 , pressure setting up signal for the pressure adjustment valve  46  for the pipe jet and the pressure adjustment valve  45  for the working fluid jet guide, valve opening and/or closing signal, an actuation and/or stop signal for the pressurized air supply equipment  47 , Z axis direction displacement indication signal for the servo unit  39 , a control signal for the pulsed power supply  36 , and a control signal for NC equipment  42 . The decision processing measure  44   c  is applied necessary pulse voltage to the electrical discharge machining gap  35   b , outputs a servo control signal sv in order to control the electrical discharge machining gap so as to be a necessary optimal value. The signal F indicating the status of the electrical discharge machining gap  35   b  is given from the pulsed power supply  36  to the control unit  44 , the servo control signal sv is given to the servo motor  3 , thereby a feed amount of the electrode-for-machining  11  in the Z axis direction is controlled. The pulse voltage for machining is applied from the pulsed power supply  36  to the electrical discharge machining gap  35   b  located between the electrode-for-machining  11  and the workpiece  14  through the output line  37 , 38 . 
     During machining, the electrode-for-machining  11  is rotated by the electrode rotating motor  4 , and is moved in the Z axis direction by the servo motor  3 , during all that time, the tip portion of the electrode is guided by the electrode guide  13  and is retained the accurate position against the workpiece  14 . 
     When the electrode-for-machining  11  descends in the Z axis direction to and is in the vicinity of the entrance surface of the workpiece  14 , a voltage drop of the pulse for machining occurs and the original point for machining is set. Then, in NC electrical discharge machining equipment, the machining area is shifted and the electrical discharge machining can be started, or the electrical discharge machining can be directly started. 
     The sigh  55  is a sealing member, as which O-ring is used. The sigh  56  is the bowl-shaped block, and the  59  is a plug cap. 
     The above mentioned small-hole electrical discharge machining device retains the upper portion of the stick-shaped or the pipe-shaped electrode-for-machining with the electrode holder, and guides the lower portion of the electrode-for-machining in the Z axis direction in the vicinity of the workpiece  14  with the electrode guide with the layer of the high pressure working fluid  22   c  interposed. Then the high pressure working fluid  22   c  drawn in the high pressure working fluid acceptance chamber  9  is jetted from the high pressure working fluid jet opening  9   a . The high pressure working fluid jet opening  9   a  is regulated in a slightly larger diameter than the diameter of the electrode-for-machining, and prevents the jet flow from expanding as much, and jets the high pressure working fluid  22   c  in such a manner that the jet flow surrounds the circumference of the electrode-for-machining, the high pressure working fluid  22   c  is supplied to the electrical discharge machining gap  35   b  deeply. Therefore, the small-hole electrical machining is performed by relatively feeding the electrode-for-machining in the Z axis direction with the electrode-for-machining rotated, hereby the machining debris which occurs at the bottom portion of the electrical discharge machined hole is taken up by the working fluid supplied the electrical discharge machining gap  35   b  deeply and is carried away to the entrance portion of the electrical discharge machined hole smoothly. Since the jet flow which reaches from the high pressure working fluid jet opening  9   a  to the periphery of the entrance portion of the electrical discharge machined hole on the surface of the workpiece, hits strongly the working fluid including the machining debris just flown out of the electrical discharge machining gap  35   b  to the periphery of the entrance portion of the electrical discharge machined hole, is scattered in misty condition on hit impact, because a puddle of the working fluid isn&#39;t arranged in the periphery of the entrance portion of the electrical discharge machined hole and the fused adhesive deposit isn&#39;t arranged at the edge of the entrance portion of the electrical discharge machined hole, the machining debris generated at the bottom portion of the electrical discharge machined hole doesn&#39;t accumulate in the electrical discharge machining gap  35   b  and is removed smoothly. Additionally, since the electrode-for-machining is cooled sufficiently, because the current supplied to the electrode-for-machining can be substantially larger than ever before, the electrical discharge machining time is shorten and is several times shorter than ever before and the electrical discharge machining efficiency is improved substantially. Furthermore, because at the point of finishing drilling, the jet flow from the high pressure working fluid jet opening  9   a  penetrates through the electrical discharge machining gap, the machining debris adhered at the side of the electrode is flushed away and the fused adhesive deposit isn&#39;t arranged at the lower edge of the electrode-for-machining. 
     As shown in  FIG. 4 , because the high pressure working fluid  22   c  is jetted from the clearance between the electrode-for-machining  11  and the lower guide piece  13   b  of the electrode guide  13  (one side is equal to or less than 0.01 mm in the experience) along the circumference of the electrode and with the electrode surrounded, the high pressure working fluid  22   c  becomes the fluid flow directly getting into the machined hole. Furthermore, the discharge of the machining debris can be performed effectively because the range which is covered the periphery of the entrance portion of the machined hole with the high pressure working fluid  22   c  jetted from the lower guide piece  13   b  is small in the machining debris discharged, and the machining efficiency becomes good. 
     The working fluid jet from the lower guide piece  13   b  of the electrode guide  13  is to jet the working fluid  22  pressurized at the pressure equal to or more than at least 3 MPa to the entrance portion of the electrical discharge machining gap  35   b  arranged when the electrode-for-machining  11  is either the stick-shaped electrode and the pipe-shaped electrode, along the electrode outer surface so that the electrode surface is surrounded by the jet flow approximately parallel to the electrode moving direction in thickness approximately equal to or less than the expanding width of the electrical discharge machining. 
     In the area  35   c  to which the jetted high pressure working fluid  22   c  directly hits on the upper surface of the workpiece  14 , the working fluid becomes thin wall of the fluid flow to be misty, the jetted working fluid is supplied to the electrical discharge machining gap from the portion in which the machining gap of the diameter  35   a  of the entrance portion of the electrical discharge machined hole is non-uniformly expanded, is fed to the entrance portion of the electrical discharge machining gap  35   b  with the machined chips before the workpiece is penetrated by the electrode. At this time, at the entrance portion of the electrical discharge machining gap, the working fluid with the machining debris to be discharged collides against the high pressure working fluid  22   c  jetted from the electrode guide  13 . However, according to the observation in the experimental example, the small-hole electrical discharge machining device of the present embodiment discharges extremely effectively the peripheral fluid layer compared to what the nozzle which has ever applied is set on. Therefore, the machining speed is improved substantially. 
       FIG. 7 ( a ) to ( e )  shows cross-sectional views of five embodiments of the electrode guides  13  adopted in the small-hole discharge machining device  1 . As mentioned above by using the  FIG. 6 , every electrode guides  13  shown in (a) to (e) of the  FIG. 7  plays not only the role of being flown the high pressure working fluid  22   c  into the high pressure working fluid acceptance chamber  9  in which the electrode-for-machining  11  is inserted through the lower guide piece  13   b  and the upper guide piece  13   c  fit at the lower edge and the upper edge of the high pressure working fluid acceptance chamber  9  penetrating axially, but also the role as the removal and discharge aperture of residues like the broken electrode-for-machining  11  in the high pressure working fluid acceptance chamber  9 , the machined chips and/or the like. The high pressure working fluid acceptance chamber  9  comprises the penetrated passageway  13   a  for drawing the high pressure working fluid  22   c . Therefore, the penetrated passageway  13   a  is preferred to be as large as possible within the range which the mechanical strength of the electrode  13  permits. Therefore, in the electrode guide  13  shown in the  FIG. 7 ( a ) , the penetrated passageway  13   a  is arranged to open so as to be a vertically long oval opening, and in the electrode guide  13  shown in the  FIG. 7 ( b ) , the penetrated passageway  13   a  is arranged to open so as to be a vertically long rectangular opening, in the electrode guide  13  shown in the  FIG. 7 ( c ) , the vertically middle portion is removed in a U shape from the side, is semicircular remained in the transverse section and is connected to upper and lower portion. In the electrode guide  13  shown in the  FIG. 7 ( d ), ( e ) , the high pressure working fluid flows in contact with the outer surface of the lower portion than the penetrated passageway  13   a  and cools the electrode guide  13 . Furthermore, these shapes are applicable to electrode guides  13 A in the after-mentioned second embodiment. The size of the penetrated passageway is equal to or more than 4 mm vertically. Therefore, when super steel ally material is applied to the electrode-for-machining  11 , the removal of the electrode-for-machining  11  broken in a discrete length like 2 mm, 4 mm, 8 mm and the like in the high pressure working fluid acceptance chamber  9  by external stress is performed well. 
     [Second Embodiment] 
       FIG. 8  is a cross-sectional view of the main section according to the second embodiment of the small-hole electrical discharge machining device of the present invention.  FIG. 9  is a cross-sectional view shown a flow of the high pressure working fluid in the main section. In this embodiment, the housing block  17 A contains the electrode guide  13 A in a hermetically sealed condition. In this embodiment, the high pressure working fluid acceptance chamber  9 A is arranged with the portion of the electrode guide  13 A from the side to the lower edge in the housing block  17 A surrounded. A head cover  17   c  seals the electrode guide  13 A and has the high pressure working fluid jet opening  9   a . The high pressure working fluid  22   c  is drawn along the electrode guide  13 A and reaches its lower edge. The high pressure working fluid jet opening  9   a  is arranged in the vicinity of the lower side of the lower guide piece  13   b  concentrically. The jet function of the high pressure working fluid  22   c  of the high pressure working fluid jet opening  9   a  in this embodiment is entirely similar to the jet function in the first embodiment. Additionally, as the other components are entirely similar to them in the first embodiment, the components in the part illustrated in the drawings are attached same signs as the signs of the corresponding components in the drawings relating to the first embodiment, and the explanations about them are omitted. 
       FIG. 10  is a cross-sectional view in an A-A section in  FIG. 8 , shows three different constitutions relating to the shapes of grooves arranged on the circumferential surface in order to flow the working fluid. The groove holds the high pressure working fluid acceptance chamber  9 A. 
       FIG. 11( a )  shows the electrode guide  13 A applied to the second embodiment of the small-hole electrical discharge machining device. The electrode guide  13  in this example has a plurality of grooves which are straight in a longitudinal direction and are apposed in a circumferential direction as the working fluid passageway on the circumferential surface, and sends the working fluid  22  to the jet opening linearly. When being applied the straight grooves, because the disturbance of the fluid flow is stabilized as a fluid sending direction is similar to the electrode moving direction, it enables to drilling in such a condition that the distance from the high pressure working fluid jet opening  9   a  to the workpiece  14  is relatively long. 
     Furthermore,  FIG. 11( b )  shows the other example of the electrode guide  13 A. As this example of the electrode guide  13 A has helical grooves on the circumferential surface of the guide, the rotating flows are given for the machining debris discharge, and the machining is stabilized even if the rotating speed of the electrode relatively low. In the electrode guide  13  of this example, the helical grooves are arranged at the angle of 45 degree. However the angles of the helical grooves are not limited to 45 degree, in accordance with the distance between the electrode guide  13 A to the workpiece  14  and/or the electrode rotating speed, the electrode guide  13 A having the appropriate groove angles is selected in compliance with the situation at that time. Herein, the number of the straight and helical groove or grooves may be one or more than one. 
     EXPERIMENTAL EXAMPLE 1 
     When the pipe-shaped electrode was attached to the small-hole electrical discharge machining device shown in the embodiment, and the electrical discharge machining was performed to the work piece of which the material is SUS304 and the machining thickness is 1 mm, thes diameter of the machined hole became 0.075 mm and the machining time was approximately 4 second. In this data, the amount of fluid of the working fluid is 20.7 g/rain, and the amount is eighty times as much as the amount of fluid 0.254 ml/min of the jet of the working fluid  22  when applied the pipe-shaped electrode of which diameter  35   d  is 0.1 mm shown in  FIG. 4 . Though the diameters of hole and the machining thicknesses are different, the machining speed improves to be 25 times faster than ever before by comprising the electrode guide  13 . Since the environment applying the working fluid jet guide is kept so that the machining debris are discharged stably. Therefore, the space between the electrode guide and the workpiece  14  isn&#39;t submerged. 
     EXPERIMENTAL EXAMPLE 2 
     When the pipe-shaped electrode was attached to the small-hole electrical discharge machining device shown in the embodiment, and the electrical discharge machining was performed to the work piece of which the material is SUS304 and the machining thickness is 1 mm, when the diameter of the electrode  35   d  shown in  FIG. 4  is 0.055 mm and the inner diameter of the lower guide piece  13   b  is 0.063 mm, the high pressure working fluid  22   c  jetted from the lower guide piece  13   b  is expanded radially in the diameter 0.065 mm and reaches the workpiece  14  at a distance 0.3 mm, and the diameter of the jetted working fluid  22  on the upper surface of the workpiece is 0.082 mm as measured. At that time, the diameter of the machined hole is 0.079 mm. During the electrical discharge machining, the working fluid reaches the upper surface of the workpiece  14  directly through the electrical discharge machining gap  35   b . The width in a radial direction of the electrical discharge machining gap  35   b  is calculated by ((the radial diameter  35   f  of the jetted working fluid on the upper surface of the workpiece)−(the diameter  35   e  of the entrance portion of the electrical discharge machined hole))/2=0.0015 mm, the above mentioned jetted working fluid becomes misty at the area  35   c.    
     Consequently, the electrical discharge machining proceeds in such a condition that the wall of the working fluid preventing the removal of the machining debris and the puddle of the working fluid doesn&#39;t occur. In the machining, the electrical discharge machining time is 3.7 second when the material of the workpiece  14  is SUS304 and the machining thickness is 1.0 mm. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Scheme 1 
               
             
          
           
               
                   
                   
                   
                 Diameter 
                 Machining 
                 Machining 
                 wear-out 
                 Diameter 
                 Fluid 
               
               
                   
                   
                 Diameter 
                 of guide 
                 time 
                 speed 
                 ratio 
                 of hole (mm) 
                 Pressure 
               
               
                   
                 Electrode 
                 of electrode 
                 φ 
                 sec 
                 mm/min 
                 % 
                 φmm 
                 Mpa 
               
               
                   
                   
               
             
          
           
               
                 Data 1 of the 
                 Tangsten 
                 0.06 
                 0.05 
                 2.6 
                 23.0 
                 72 
                 0.083 
                 20 
               
               
                 present invention 
               
               
                 Data 2 of the 
                 Tangsten 
                 0.06 
                 0.05 
                 3.7 
                 16.2 
                 45.5 
                 0.079 
                 18 
               
               
                 present invention 
               
               
                 Data of the other 
                 Tangsten 
                 0.06 
                   
                 21 
                 2.23 
                 30 
                 0.076 
               
               
                 company&#39;s product 
               
               
                   
               
               
                 WORKPIECE: Data of teh present invention SUS304 (t = 1 mm), Data of the other company&#39;s product SCM420 (t = 0.8 mm) 
               
             
          
         
       
     
     In the data compared to the machining efficiency, the machining speed of the small-hole electrical discharge machining device of the embodiments are approximately 7 times faster than the machining speed of the other company&#39;s one. If the machining condition is altered, the hole is expanded in a diameter of 0.007 mm, but can machine at ten times faster speed. 
     The working fluid  22  which is pressurized and jetted from the electrode guide  13  applied for the machining time is 1.7 cc, i.e. a extremely little amount of the working fluid  22  used. 
     A graph shown in  FIG. 12  is the data to show an adequate distance between the electrode guide  13  and the workpiece  14  under the machining condition at a low machining speed, the standard distance is 0.3 mm in the working fluid jetting. During the electrical discharge machining, as the misty working fluid  22  has a tendency to becoming liquid around the machining area if the machining time is long, the working fluid  22  jetted from the electrode guide  13  and the electro discharge machining debris discharged by the jet machining is blown away from the entrance portion of the electrical discharge machining gap  35   b  by air jetted from the air nozzle  16  attached in the vicinity of the electrode guide  13 , the jetted working fluid recovery equipment  20  recovers the liquid and misty working fluid  22  including the electrical discharge machining debris, wherein the jetted working fluid recovery equipment  20  is arranged at the portion beyond the electrode guide  13  arranged in an air jetting direction of the air nozzle  16 , hereby what prevents discharging the working fluid  22  including the machining debris which should be discharged is a extremely little, and it enables to perform the stable electrical discharge machining at high speed, and to attach and to remove the workpiece  13  and the like easily under a gas atmosphere. 
     EXPERIMENTAL EXAMPLE 4 
       FIG. 13  is a graph showing the experimental result relating to the performance change against the working fluid jet pressure.  FIG. 14  is a graph showing the experimental result relating to the machining performance change against the working fluid jet pressure. This experiment is that each changes of the electrode mortality ratio, the working speed and the diameter of the entrance of the machined hole is measured with altering the working fluid jet pressure (the amount of flow). In this experiment, the workpiece  14  of SUS304 and 1.0 mm in a thickness is penetrated by the electrode of 0.005 mm in a diameter. At this time, cooling the electrode above the electrode guide  13  and jetting air to the electrical machining gap are also applied. According to the experimental result, the machining performance in such a condition that the working fluid jetting pressure is around 3 MPa. For details, when the working fluid jet pressure is up to 3 MPa, the effect of the machining debris discharge by the jet flow from the electrode guide at the electrical discharge is poor, and when the working fluid jet pressure is more than 3 MPa, the wear-out ratio of the electrode stops increasing, and the machining debris are discharged effectively. When the working fluid jet pressure is more than 12 MPa, it is measured that the electrode wear-out ratio, the machining speed and the diameter of the entrance of machined hole are drastically altered. The cause that electrode wear-out ratio and the diameter of entrance of machined hole become small when the working fluid jet pressure is 12 MPa is supposed that the mechanical stress by the movement of electrode during machining is reduced because the working fluid works as lubricating liquid when the working fluid  22  passes through the guiding surface of the upper guide piece  13   c  and the lower guide piece  13   b  opposite to the electrode-for-machining  11 , the friction of the slide bearing is reduced by the working fluid flow between the electrode-for-machining  11  and the upper guide piece  13   c  and between the electrode-for-machining  11  and the lower guide piece  13   b . Hereby, it is supposed that the machining performance changes by increasing the number of the electrode rotating even if the working fluid jet pressure is low. Therefore, it is confirmed by the experiments by the inventors of the present invention that applying the electrode cooling for the electrode above the electrode guide  13  and the air jet to the electrical discharge machining gap jointly and being the fluid pressure of the high pressure working fluid  22   c  at a pressure of at least 3 MPa are effective for drilling the hole in relatively small or fine diameter at high speed. It is also confirmed that the small-hole electrical discharge machining can be performed when the fluid pressure of the high pressure working fluid  22   c  is at 20 MPa or more 
       FIG. 15  is a graph for comparison between the conventional normal machine and the prototype machine of the present invention. The drilling electrical discharge machining is performed for the workpiece of SUS304 and 1.0 mm thickness with the electrode in a diameter of 0.055 mm, and the machining speed, the electrode wear-out ratio, the hole diameter and the GAP are compared. As shown in the graph, the working speed becomes dramatically fast, the electrode wear-out is reduced and the gap becomes small. 
       FIG. 16  is a graph shows the relationship between the changes of electrode-guide GAP (one side, μm) and the machining performance relating to the electrical discharge machining with the device of the present invention. 
       FIG. 17  is a graph for comparison the progress statuses of the electrical discharge machining of the conventional device and the device of the present invention. The drilling electrical discharge machining is performed for the workpiece of SUS304 and 20 mm thickness with the stick-shaped electrode in brass of φ1 mm, and the progress statuses are measured until it penetrated. The conventional device takes 49 seconds for penetration, while the device of the present invention takes 5 second for penetration. 
       FIG. 18  is a graph showing changes of the wear-out ratio against changes of the machining depth of the electrical discharge machining device and changes of the machining speed. 
     [The Other Embodiment] 
     The present invention isn&#39;t limited to the above mentioned embodiments, the technical scope interpreted based upon the statements in the scope of the claims includes a various sorts of embodiments changed their design without departing from the scope of the invention. 
     REFERENCE SIGN LIST 
     
         
           8  rotating shaft 
           8   a  pressurized working fluid distribution chamber 
           8   b  jet opening 
           9 , 9 A pressurized working fluid acceptance chamber 
           9   a  pressurized working fluid jet opening 
           10  electrode holder 
           11  electrode-for-machining 
           13  electrode guide 
           14  workpiece 
           15  fluid tank 
           16  air nozzle 
           17 , 17 A housing block 
           17   a  fluid passageway 
           20  jetted working fluid recovery equipment 
           21  working fluid pump 
           22   b  pressurized working fluid 
           22   c  high pressure working fluid 
           35   a  diameter of the entrance portion of electrical discharge machined hole 
           35   b  electrical discharge machining gap 
           40  fluid reserve tank