Fluid nozzle

A fluid nozzle includes a nozzle chip that includes a through hole having an inlet port from which a fluid supplied to the fluid nozzle is introduced and an outlet port from which the introduced fluid is ejected; and a base metal member that supports the nozzle chip embedded in a rear portion of the base metal member. The fluid nozzle receives the fluid supplied to the rear portion from the inlet port and ejects the fluid from the outlet port. An exposed portion of the base metal member is covered with a ceramic coating so that the base metal member does not touch the fluid.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application No. 2014-012573 filed in the Japan Patent Office on Jan. 27, 2014, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fluid nozzles and particularly to a fluid nozzle including a base metal member having a rear portion covered with a ceramic coating.

2. Description of the Related Art

Water jet processing machines perform cutting or other operations using a water jet (a liquid column made of a fluid jet), which is a high-pressure fluid (for example, water or highly pure water). The water jet processing machines are characterized in that they produce a relatively small cutting width and less frequently cause seizure of a material or change the composition of a material. Thus, the water jet processing machines are used to perform operations such as to cut expensive materials or to process fine grooves.

These days, in order to minimize processing steps and the amount of materials that are to be wasted during processing, precision finished products that do not require finishing using a water jet have been increasingly demanded.

Thus, a processing apparatus that processes a material using a laser beam guided by a water jet has been developed (hereinafter such an apparatus is referred to as a “water beam processing machine” (for example, see Japanese Patent No. 5220914). The water beam processing machine is advantageous in that it can highly precisely finish products since the material is negligibly deformed by heat.

To highly precisely finish products in water jet processing, a water jet from a water-jet fluid nozzle is required to be ejected through the nozzle center so as to be parallel to the nozzle axis while the water jet keeps a stable liquid-beam diameter.

To date, a water-jet-processing fluid nozzle in which a nozzle orifice made of a diamond is embedded in a nozzle body that fixes a nozzle chip thereto (for example, see FIG. 2 of Japanese Unexamined Patent Application No. 2009-78313) is known.

In the fluid nozzle described in Japanese Unexamined Patent Application No. 2009-78313, a portion of the nozzle body that is exposed to a high-pressure fluid (high-pressure water) is made of a resin material in order that a workpiece can be prevented from being contaminated by a water jet into which metal in the nozzle body is dissolved and mixed as a result of the high-pressure water coming into contact with the nozzle body.

However, the strength of the fluid nozzle described in Japanese Unexamined Patent Application No. 2009-78313, which includes a resin portion in the nozzle body that fixes the nozzle chip thereto, may be insufficient to hold the nozzle orifice for use in highly precise finishing of products. Thus, disadvantageously, this fluid nozzle is insufficient to precisely position the nozzle orifice and firmly and stably hold the nozzle orifice.

In some cases, water hammer occurs in the nozzle body during the supply of a high-pressure water or when the supply of the high-pressure water is stopped, exerting a strong impact force on the nozzle body. In the case where the nozzle body is used in a laser beam processing machine such as the one disclosed in Japanese Patent No. 5220914, the nozzle body is required to have such rigidity and durability as to be capable of stably holding the nozzle chip since the nozzle chip and its vicinity may be damaged as a result of being exposed to a strong laser beam.

In the case where the nozzle body is damaged by the impact pressure and the laser beam, the flow of the high-pressure water around the inlet port of the nozzle chip is disturbed and becomes irregular and unstable, conceivably failing to form a stable water jet.

SUMMARY OF THE INVENTION

In view of these problems, it is an object of the present invention to provide a fluid nozzle that can form a highly precise, stable water jet and that can have improved rigidity and durability.

In view of the object, a first aspect of the present invention is a fluid nozzle that includes a nozzle chip that includes a through hole having an inlet port from which a fluid supplied to the fluid nozzle is introduced and an outlet port from which the introduced fluid is ejected; and a base metal member that supports the nozzle chip embedded in a rear portion of the base metal member, wherein the fluid nozzle receives the fluid supplied to the rear portion from the inlet port and ejects the fluid from the outlet port, and wherein an exposed portion of the base metal member is covered with a ceramic coating so that the base metal member does not come into contact with the fluid.

In such a configuration, the nozzle chip is held by the base metal member. Thus, the nozzle chip is thus firmly held and has a high rigidity and long-term durability. In addition, since the exposed portion of the base metal member is covered with the ceramic coating, the supplied fluid does not touch the base metal member. This configuration thus can prevent metal contained in the base metal member from dissolving into the fluid, whereby a workpiece can be prevented from being contaminated by metal dissolved from the base metal member.

The inventors of the application have newly observed, through experiments, that the high pressure of a fluid causes a phenomenon in which metal dissolved into the fluid precipitates in the form of a crystal around the inlet port of the nozzle chip (the phenomenon is referred to as pressure induced crystallization).

Here, pressure induced crystallization is a phenomenon in which crystals precipitate when a mixture is pressurized at a high pressure of several thousand atmospheres and the pressure induced crystallization is used in various fields such as a chemical industrial field as a method of crystallization. The pressure induced crystallization causes metal (crystallized metal) that has adhered to the nozzle chip to gradually grow into crystal. Thus, a phenomenon can be observed in which the flow of the fluid introduced into the inlet port receives irregular resistance and a water jet ejected through the outlet port is deviated. Thus, the pressure induced crystallization has to be effectively prevented.

According to the present invention, a highly precise stable water jet can be formed while the water jet is prevented from being deviated or inclined by the crystallized metal caused by dissolved metal because the supplied fluid does not touch the base metal member having an exposed portion covered with a ceramic coating and thus metal does not dissolve into the supplied fluid from the base metal member.

A second aspect of the present invention is the fluid nozzle according to the first aspect, wherein the ceramic coating covers an area including a boundary portion in the rear portion in which the base metal member and the nozzle chip are in contact with each other and extending up to a peripheral portion of the nozzle chip.

In such a configuration, coating an area including the boundary portion at which the base metal member and the nozzle chip are in contact with each other can prevent the fluid from accessing the base metal member through the boundary portion, whereby metal contained in the base metal member can be more reliably prevented from dissolving into the fluid.

A third aspect of the present invention is the fluid nozzle according to the first or second aspect, wherein the ceramic coating is a titanium nitride coating or a titanium aluminium nitride coating.

Such a configuration enables formation of a stable ceramic coating at an appropriate portion.

A fourth aspect of the present invention is the fluid nozzle according to any one of the first to third aspects, wherein the base metal member includes a base portion and a sintered metal portion embedded in the base portion, wherein the sintered metal portion has an annular shape so as to surround a circumferential portion of the nozzle chip, and wherein the nozzle chip is fixed to the base portion by sintering the sintered metal portion.

Such a configuration allows the nozzle chip to be stably and firmly joined with the base portion by sintering the sintered metal, whereby a highly precise, stable water jet can be obtained using the nozzle chip having a high holding power and a high rigidity.

A fifth aspect of the present invention is the fluid nozzle according to the fourth aspect, wherein the sintered metal portion is made of nickel or an alloy containing nickel as a main component, and wherein the nozzle chip is made of a mineral crystal having a Mohs hardness of 9 or higher.

In such a configuration, the material of the nozzle chip can be preferably selected from mineral crystal materials having a Mohs hardness of 9 or higher and having an excellent strength and durability such as, diamond, sapphire, corundum, or cubic boron nitride, since nickel or an alloy containing nickel as a main component is easily joined to and fused with a crystalline material such as diamond or sapphire by sintering.

Thus, a highly precise, stable water jet can be obtained using the nozzle chip having improved rigidity and durability.

The fluid nozzle according to an aspect of the present invention having the above-described configuration can form a highly precise, stable water jet and can have improved rigidity and durability.

In other words, by preventing metal contained in the base metal member from dissolving into the supplied fluid, the flow of the fluid can be prevented from being disturbed due to the dissolved metal having adhered to the surface of the nozzle chip as a result of pressure induced crystallization. Thus, the fluid nozzle according to an aspect of the present invention can keep the surface of the nozzle chip in normal condition, so that the flow of the fluid at the circumferential portion of the inlet port becomes stable and the water jet is prevented from being deviated. Thus, a highly precise, stable water jet can be obtained.

The fluid nozzle according to an aspect of the present invention can have higher heat durability (heat resistance) and higher mechanical strength by using a base metal member to hold the nozzle chip. Thus, besides having a function of preventing metal from adhering to the nozzle chip, the fluid nozzle can have improved rigidity and durability and form a stable water jet. The fluid nozzle according to an aspect of the present invention is thus preferably usable in, besides a water jet processing machine, a water beam processing machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Referring toFIGS. 1A and 1B, a fluid nozzle10according to a first embodiment of the present invention is described. For convenience of illustration, throughout the drawings to be referred to, the dimensions such as the sizes of components, the diameter of a nozzle, or the thickness of a ceramic coating are not particularly limited and thus illustrated in an exaggerated manner.

The fluid nozzle10includes a nozzle chip12in which a through hole121is formed, a base metal member11that supports the nozzle chip12embedded therein, and a ceramic coating13that covers an exposed portion11eof the base metal member11that is exposed to a high-pressure fluid (for example, water or pure water, referred to as “a high-pressure water Q”, below). The through hole121serves as a nozzle hole through which the high-pressure water Q is supplied.

The fluid nozzle10ejects the supplied high-pressure water Q from the through hole121, serving as a nozzle hole, to form a water jet WJ (liquid column jet).

In the following description of the fluid nozzle10, for convenience of illustration, a portion of the fluid nozzle10on the downstream side in the direction in which the water jet WJ is ejected is referred to as a front portion of the fluid nozzle10and a portion of the fluid nozzle10on the upstream side in the direction in which the water jet WJ is ejected is referred to as a rear portion of the fluid nozzle10.

The base metal member11has a recess (insertion portion)11bin a rear portion11afor holding the nozzle chip12and a clearance hole11cthat allows the water jet WJ to pass therethrough. The base metal member11is made of a metal material that has a sufficiently high strength to firmly fix the nozzle chip12. For example, in the case where the base metal member11is formed of a sintered metal, the base metal member11and the nozzle chip12can be integrated together by sintering so as to be highly precisely positioned with respect to each other by being firmly fixed to each other.

Forming the base metal member11using a sintered metal is particularly preferable because, when the base metal member11is made of nickel (Ni) or a nickel chrome alloy containing nickel (Ni) as a main component, the nozzle chip12can be made of a mineral crystal having a Mohs hardness of 9 or higher such as diamond, corundum, or cubic boron nitride, whereby the nozzle chip12can have improved heat resistance and durability.

Since the nozzle chip12is embedded in and held by the base metal member11having higher rigidity than resin or other materials, the nozzle chip12has sufficiently high strength against the flow of the supplied high-pressure water Q, the impact pressure (water hammer) that occurs as a result of impact, or other forces such as a tight fastening force that occurs when the nozzle chip12is fixed to or inserted into the base metal member11.

The nozzle chip12having this configuration is not subjected to damages such as detachment or corrosion and thus can bear long term use.

The fluid nozzle10according to the embodiment of the present invention can thus preferably be used in a nozzle unit30(seeFIG. 2) of a water jet processing machine and a nozzle unit40(seeFIG. 3) of a water beam processing machine, which are described below.

In this embodiment, the nozzle chip12is embedded in the base metal member11while being held in the rear portion11aof the base metal member11in such a manner that the nozzle chip12is flush with the rear end surface on the rear portion11aso as not to disturb the flow of the high-pressure water Q. However, the configuration is not limited to this. As long as the nozzle chip12does not disturb the flow of the high-pressure water Q, the nozzle chip12may be disposed in other ways in accordance with the form of introducing the high-pressure water Q, for example, the nozzle chip12may be buried under the rear end surface or may protrude from the rear end surface.

The through hole121formed in the nozzle chip12includes an inlet port121a, from which the high-pressure water Q is introduced, and an outlet port121bfrom which the introduced high-pressure water Q is ejected in the form of a water jet WJ.

The nozzle chip12is made of a material having high abrasion resistance and strength with which the material is not deformed by the pressure from the high-pressure water Q. Examples usable as the material for the nozzle chip12include diamond, corundum, cubic boron nitride, topaz, quartz, and other crystalline materials. Desirably, a mineral monocrystal having a Mobs hardness of 9 or higher is used as a material of the nozzle chip12. The use of the mineral having a Mohs hardness of 9 or higher allows formation of a highly precise through hole121, whereby a highly precise water jet WJ can be formed. In addition, the use of a monocrystal material having a high hardness improves the abrasion resistance, whereby the life of the nozzle10can be extended. The nozzle chip12is mounted on the base metal member11in such a manner that the through hole121and the clearance hole11cformed in the base metal member11are coaxial with each other.

The ceramic coating13is disposed so as to cover at least the exposed portion11eon the rear portion11aof the base metal member11that is exposed to the high-pressure water Q.

Specifically, the ceramic coating13covers at least the exposed portion11eon the rear portion11aof the base metal member11that is exposed to the high-pressure water Q in the state where the nozzle chip12is embedded in the rear portion11aof the base metal member11. Desirably, the ceramic coating13covers an area including a boundary portion11dbetween the base metal member11and the nozzle chip12and extending up to a peripheral portion of the nozzle chip12. However, it is preferable that the ceramic coating13do not cover the circumferential portion (near an edge portion) of the inlet port121aso as not to affect the flow of the high-pressure water Q.

Examples usable as the ceramic coating13include TiN (titanium nitride), TiAlN (titanium aluminium nitride), and other ceramic coatings. The TiN or TiAlN coating is made by physical vapor deposition (PVD). Here, the circumferential portion of the inlet port121ais masked with a preformed coating containing TiO2 (titanium oxide). The deposition coating is not formed on the portion masked with the TiO2 coating and thus is not formed on the circumferential portion of the inlet port121a. As illustrated inFIG. 1B, the ceramic coating13does not adhere to the circumferential portion of the inlet port121aand thus the circumferential portion of the inlet port121aof the nozzle chip12is exposed.

The configuration in which the circumferential portion of the inlet port121aof the nozzle chip12is exposed allows the highly precisely processed nozzle chip having rigidity and durability to perform its intrinsic performance, whereby the flow of the fluid can be kept stable and a highly precise, stable water jet WJ can be formed.

Specifically, as illustrated inFIG. 1A, the flow of the high-pressure water Q is narrowed at the inlet port121aof the fluid nozzle10so as to form a water jet WJ that passes through the through hole121without touching the circumferential wall of the through hole121. Thus, the configuration and the form of the inlet port121aand its vicinity are important and the surface roughness, the dimensional accuracy, and other properties have to be highly precisely managed. The fluid nozzle10according to the embodiment is designed to allow the highly precisely processed nozzle chip12having rigidity and durability to perform its own performance by not providing the ceramic coating13around the inlet port121a.

The ceramic coating can be formed not by physical vapor deposition but by chemical vapor deposition (CVD) or other deposition. The method for keeping a portion around the inlet port121aout of a ceramic coating can be appropriately selected from various different coating methods.

The method for keeping a portion out of the ceramic coating (masking method) is not particularly limited and may be appropriately selected from various known methods in consideration of various factors such as the method for forming a coating, the type of a coating that is formed, or the material of the base metal member11.

Referring now toFIGS. 2 and 3, the cases where the fluid nozzle10according to the first embodiment of the present invention is used in a nozzle unit30(seeFIG. 2) of a water jet processing machine and in a nozzle unit40(seeFIG. 3) of a water beam processing machine are described.FIG. 2is a vertical section of a nozzle unit30of a water jet processing machine in which the fluid nozzle10is used andFIG. 3is a vertical section of a nozzle unit40of a water beam processing machine in which the fluid nozzle10is used.

Use in Water Jet Processing Machine

As illustrated inFIG. 2, the nozzle unit30of the water jet processing machine includes a fluid nozzle10that ejects a high-pressure water Q supplied from a high-pressure pump HP, a nozzle holder31that holds the fluid nozzle10, and a seal member32that prevents leakage of the high-pressure water Q.

The nozzle holder31includes a pipe-shaped body31aand a nozzle fixing member31bdisposed in the body31a.

The body31ahas a recess (insertion portion) in a front end portion (a lower portion in the drawing) in which the nozzle fixing member31bis disposed. On the circumferential portion of the recess, triangular threads31care formed. The triangular threads31callow the nozzle fixing member31bto be screwed into the body31a.

The nozzle fixing member31bholds the fluid nozzle10to fix the fluid nozzle10to the body31a.

The nozzle fixing member31bhas a recess (insertion portion) in a rear portion (a top portion in the drawing) into which the fluid nozzle10is embedded and the fluid nozzle10is inserted and fitted into the recess. A rear portion (a top portion in the drawing) of the nozzle fixing member31bis inserted and fitted into the insertion portion of the body31a.

The outer circumferential portion of the fluid nozzle10having such a configuration is fitted into the body31awith the nozzle fixing member31binterposed therebetween, whereby the fluid nozzle10is fixed to the nozzle holder31at a high dimensional accuracy.

The body31aand the nozzle fixing member31bof the nozzle holder31are made of a metal that is less likely to be dissolved into the high-pressure water Q and that has a corrosion resistance. Desirably, a titanium (Ti) alloy is used, but a precipitation hardening or austenitic stainless steel is also usable.

The seal member32is an O-ring and is disposed between the rear portion11a(an upper portion of the drawing) of the fluid nozzle10and a bottom portion (an upper portion of the drawing) of the recess of the body31a. The seal member32is made of natural rubber, ethylene propylene diene monomer (EPDM) rubber, nitrile butadiene rubber (NBR), or other synthetic rubber. In the case where workpieces (not illustrated) are components (such as electronic components) that can be easily harmed by contamination of impurities, the use of a seal member made of EPDM rubber is desirable.

Pure water is used as the high-pressure water Q and the high-pressure water Q is supplied from the high-pressure pump HP through the nozzle holder31to the rear portion11aof the fluid nozzle10. The nozzle chip12reduces the flow of the high-pressure water Q supplied, with pressure, to the rear portion11aof the fluid nozzle10by introducing the high-pressure water Q from the inlet port121aand ejects the high-pressure water Q from the outlet port121bin the form of a water jet WJ. The ejected water jet WJ impacts against a workpiece (not illustrated) so as to process the workpiece in accordance with the momentum of the water jet WJ. The processing point is a point at which the water jet WJ comes into contact with (impacts against) the workpiece.

Thus, for a particularly precise processing, the water jet WJ is required to be ejected so as to be coaxial with a nozzle fixing axis. When the water jet WJ is coaxial with the nozzle fixing axis, water jet processing can be highly precisely performed by precisely controlling the nozzle fixing axis using a multi-axis robot or a numerical control device.

Use in Water Beam Processing Machine

As illustrated inFIG. 3, a nozzle unit40of a water beam processing machine includes a fluid nozzle10A, a nozzle holder41, a high-pressure pump HP that produces a high-pressure water Q, a flow-adjusting chamber42in which the turbulence of the high-pressure water Q supplied from the high-pressure pump HP is reduced, a liquid oscillating chamber44, which guides a liquid that flows thereinto from the flow-adjusting chamber42to an entrance of the nozzle opening, a laser oscillator45, a focusing lens46that focuses a laser beam L output from the laser oscillator45, a window47that allows the laser beam L to pass therethrough, and a seal member48that prevents leakage of the high-pressure water Q.

The fluid nozzle10A is different from the fluid nozzle10illustrated inFIG. 1in terms that the fluid nozzle10A has a ceramic coating13A that covers an area extending from the rear end surface to a portion of the outer circumferential surface of the fluid nozzle10A, whereas the fluid nozzle10has a ceramic coating13that covers the rear end surface of the fluid nozzle10.

The ceramic coating13A of the fluid nozzle10A is the same as the ceramic coating13of the fluid nozzle10illustrated inFIG. 1in terms that the ceramic coating13A covers the exposed portion11eof the base metal member11so as to prevent the base metal member11from being exposed to a high-pressure water Q. Other configuration of the ceramic coating13A is similar to that of the ceramic coating13A and is thus not redundantly described.

The nozzle holder41includes a pipe-shaped body41aand a nozzle fixing member41bdisposed inside the body41a. The nozzle holder41has a similar configuration as the nozzle holder31of the nozzle unit30illustrated inFIG. 2and is thus not described in detail.

The flow-adjusting chamber42is an annular space having a substantially rectangular cross section. The flow-adjusting chamber42is disposed above the liquid oscillating chamber44in the nozzle holder41. A circular-tray-shaped space is formed below the flow-adjusting chamber42. Only a sector of the circular-tray-shaped space having a center angle of approximately 90° is left empty and the remaining portion of the circular-tray-shaped space is filled with an oscillating-chamber-inlet-path adjusting member49. Thus, a substantially horizontal, sector-shaped flat space having a center angle of approximately 90° expands from the center of the nozzle holder41and a thin space having an arc shape when viewed in plan rises vertically from the circumferential arcuate portion of the sector-shaped flat space. This inner space formed by cutting the circular tray into a sector having a center angle of approximately 90° serves as an oscillating-chamber inlet path43. The oscillating-chamber inlet path43connects the flow-adjusting chamber42and the cylindrical liquid oscillating chamber44together.

The high-pressure water Q supplied from the high-pressure pump HP flows into the flow-adjusting chamber42, passes through the oscillating-chamber inlet path43, and then flows into the liquid oscillating chamber44from only one direction. The high-pressure water Q is ejected from the liquid oscillating chamber44through a through hole121formed at the center of the fluid nozzle10A in the form of a water jet WJ into which a laser beam L is guided.

The laser beam L output from the laser oscillator45is focused by the focusing lens46, passes through the window47, is converged at a position slightly above the inlet port121a, and is guided into the water jet WJ. The laser beam L guided into the water jet WJ is incident on a workpiece (not illustrated) and processes the workpiece with its energy.

In order to lower the ratio at which the laser beam L is absorbed by the high-pressure water Q, the nozzle unit40used in the water beam processing machine is required to eject a high-pressure water Q having a lowest possible conductivity. Thus, a material such as a Ti alloy or a precipitation hardening stainless steel is used for a portion made of metal, such as the nozzle holder41, that comes into contact with the high-pressure water Q.

Now, operation effects of the fluid nozzle10according to the first embodiment of the present invention (and the fluid nozzle10A, which has the same effects) are described in comparison with a fluid nozzle50(FIGS. 4A to 6) according to a comparative example that does not include a ceramic coating.FIGS. 4A and 4Billustrate the configuration of the fluid nozzle50according to the comparative example that does not include a ceramic coating, whereFIG. 4Ais a vertical section of the fluid nozzle50andFIG. 4Bis a plan view of the fluid nozzle50.FIGS. 5A and 5Billustrate operation effects of the fluid nozzle50according to the comparative example that does not include a ceramic coating, whereFIG. 5Ais a vertical cross section of the fluid nozzle50andFIG. 5Bis a plan view of the fluid nozzle50.

As illustrated inFIGS. 1A and 1B, the fluid nozzle10according to the first embodiment of the present invention is different from the fluid nozzle50according to the comparative example illustrated inFIGS. 4A and 4Bin terms that the fluid nozzle10includes a ceramic coating13that is disposed so as to cover an area including a rear portion11aof the base metal member11, a boundary portion11dat which the base metal member11and the nozzle chip12are in contact with each other, and the peripheral portion of the nozzle chip12, whereas the fluid nozzle50does not include a ceramic coating. Components of the fluid nozzle50according to the comparative example illustrated inFIGS. 4A to 5Bthat are the same as those of the fluid nozzle10illustrated inFIGS. 1A and 1Bare thus denoted by the same reference symbols and are not described in detail.

In the fluid nozzle10according to the first embodiment, the exposed portion11e(a portion that comes into contact with the high-pressure water Q) of the base metal member11is covered by the ceramic coating13. Thus, the base metal member11does not come into contact with the high-pressure water Q and metal ions are not dissolved into the high-pressure water Q from the base metal member11. Consequently, precipitation of metal from the high-pressure water Q (adherence of metal) to the nozzle chip12can be avoided. Since crystallized metal does not adhere to a portion around the inlet port121aof the nozzle chip12, the flow of water around the inlet port121ais not disturbed and thus the water jet WJ is highly precisely ejected along the nozzle center axis.

On the other hand, in the fluid nozzle50according to the comparative example illustrated inFIG. 4that does not include a ceramic coating, a rear portion of the base metal member11of the fluid nozzle50is exposed and thus the exposed portion11eof the base metal member11comes into contact with the high-pressure water Q.

Thus, in a nozzle unit80of a water beam processing machine including the fluid nozzle50according to the comparative example, metal (metal ions) contained in the base metal member11dissolves into the high-pressure water Q since the base metal member11is exposed to the high-pressure water Q supplied to the fluid nozzle50.

The high pressure of the high-pressure water Q conceivably induces a phenomenon that the metal (dissolved metal) that has dissolved into the high-pressure water Q precipitates in the form of crystal around the inlet port121aof the nozzle chip12(the phenomenon is referred to as pressure induced crystallization).

Specifically, as illustrated inFIGS. 5A and 5B, since metal of the base metal member11dissolves into the high-pressure water Q, the dissolution of metal causes formation of groove-shaped recesses52on the rear end surface of the base metal member11. Crystallized metal51having various shapes deposited due to the pressure induced crystallization adheres to the surface of the nozzle chip12so as to protrude from the surface.

The crystallized metal51is a crystal of metal formed as a result of the dissolved and deposited metal growing into a shape of a snow crystal (or cedar leaves) so as to extend outward from an edge portion of the inlet port121a. The crystallized metal51is not observed on the wall surface (circumferential surface) of the through hole121.

The inventors believe that the mechanism by which the crystallized metal51adheres to the surface of the nozzle chip12occurs because, metal ions in the base metal member11made of a sintered metal dissolve into the high-pressure water Q and the dissolved metal ions adhere to the surface of the nozzle chip12. Specifically, the base metal member11is made of metal that is easily joined to and fused with the nozzle chip12by sintering and the high-pressure water Q inside the liquid oscillating chamber44is compressed by high pressure. Thus, by receiving the pressure, the dissolved portion of the sintered metal precipitates and adheres to the nozzle chip12with which the dissolved metal is compatible (to and with which the dissolved metal is easily joined and fused and thus to which the dissolved metal easily adheres).

As illustrated inFIG. 6, after the crystallized metal51adheres to the surface of the nozzle chip12, the water jet WJ ejected from the fluid nozzle50inclines away from the axis of the fluid nozzle50. In the fluid nozzle50having the above-described configuration, the flow of a fluid is conceivably narrowed by receiving irregular resistance around the inlet port121aand directed in an inclined direction so as to be formed into an unstable water jet WJ. As described above, a portion around the inlet port121ahas an important function of forming a jet. Thus, adherence of the crystallized metal51to a portion around the inlet port121ais considered to largely affect the inclination of the water jet WJ.

During processing using the nozzle unit80included in a water beam processing machine, the laser beam L propagates through the water jet WJ. Thus, the process point of a workpiece (not illustrated) is a point at which the water jet WJ comes into contact with the workpiece. Since the water jet WJ deviates from the center axis of the nozzle, that is, the line extended from the center axis of the nozzle unit80, the process point deviates from the extended line. Such deviation hinders production of highly precise products even when the nozzle unit80is precisely moved by a numerically controlled apparatus. Particularly, such deviation affects critically adversely when the nozzle unit80and the workpiece three-dimensionally change their positions.

Second Embodiment

Referring toFIGS. 7A and 7B, a fluid nozzle20according to a second embodiment of the present invention is described. The fluid nozzle20is different from the fluid nozzle10according to the first embodiment in terms that the base metal member21includes a base portion211and a sintered metal portion212embedded in the base portion211.

Thus, the fluid nozzle20is different from the fluid nozzle10according to the first embodiment in terms that the ceramic coating23covers an area including the exposed portion21eon the rear portion21aof the base metal member21that is exposed to the high-pressure water Q, the base portion211, the sintered metal portion212, a boundary portion212dbetween the sintered metal portion212and the nozzle chip12, and extending up to a peripheral portion of the nozzle chip. However, other components of the fluid nozzle20are the same as those of the fluid nozzle10and thus are denoted by the same reference symbols and not described in detail.

The base portion211of the base metal member21is a member that supports the nozzle chip12and the sintered metal portion212. The base portion211has a recess211bin the rear portion21afor holding the nozzle chip12and the sintered metal portion212.

The sintered metal portion212is formed in an annular shape so as to cover the circumference of the nozzle chip12. The nozzle chip12is fixed to the base portion211by sintering the sintered metal portion212. The sintered metal portion212is a member that supports the nozzle chip12and has a recess212bthat holds the nozzle chip12. The sintered metal portion212is made of a metal that is easily joined to the base portion211and the nozzle chip12by sintering, which is the same material as that of the base metal member11of the fluid nozzle10according to the first embodiment.

In the fluid nozzle20according to the second embodiment, the base portion211that makes up a large proportion to the entire base metal member21can be made of a metal that is less likely to dissolve into pure water and that is more strong and more easily workable. Examples of the materials of the base portion211include a Ti alloy and a precipitation hardening stainless steel. Thus, the nozzle20can have higher dimensional accuracy and longer durability and reduce the amount of metal dissolved into pure water compared to the case of the fluid nozzle10according to the first embodiment. Consequently, the fluid nozzle20can form a more highly stable water jet WJ while the amount of metal adhering to the nozzle chip12is reduced further than the fluid nozzle10according to the first embodiment.