JP2005279562A - Method for forming micromist and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming micromist and its device which is capable of forming micromist (droplets of average grain size ≤10 μm) near the surface to be cooled according to compressed gas and permits efficient cooling in a wide range even in the case of cooling by the use of a small amount of cooling liquid. <P>SOLUTION: The micromist is formed through a pressure drop etc. upon the spray from a spraying nozzle by dissolving compression gas into liquid which is formed into mist according to ejector operation up to a saturation state, in a compression space which is constituted with an introduction pipe 4 connecting a gas-liquid mixing part 2 with the spray nozzle 3 incorporating a revolution chip 31. By virtue of a plurality of spray holes 32 and the revolution operation of a revolution chip disposed within the nozzle, gas and a small amount of liquid are uniformly sprayed through the plurality of spray holes and, thereby, a wide range of area is cooled with a small amount of liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a micromist generation method and an apparatus for atomizing a liquid that can be atomized in a micromist state.

  In recent years, interest in environmental problems has been increasing, and in order to respond to this, there is an increasing need to process a workpiece with as little chemical as possible. For example, in the machining field, the practical application of dry cutting technology is urgently needed, and in order to efficiently cool the heat generated by machining, a cooling method using heat of vaporization with a small amount of water and a large amount of air is required.

  Conventionally, when a liquid is applied in the form of a mist (fine droplets) to the surface to be processed or the object to be processed is cooled, for example, as shown in FIG. 4A, a pump A, a chemical tank B and a nozzle Using the atomizing apparatus consisting of C, the chemical solution in the chemical solution tank B was pressurized by the pump A and sent to the small-diameter nozzle C, and the chemical solution was sprayed from this nozzle to form a mist (mist). Introducing gas into this system and creating a fine liquid-gas mixture, a high-pressure gas (mainly high-pressure air) is introduced into the two-fluid nozzle using a nozzle C that mixes the liquid and gas, called a two-fluid nozzle. By doing so, the atomized gas (cooling gas) produced by the rapid expansion and diffusion of the high-pressure gas was produced.

The mist generation distribution (distribution of the particle diameter and the number of generated particles) produced by such a measure ranges from a large particle of about 70 μm to a small particle of 5 μm or less as shown in the graph of FIG. The generated mist distribution was different depending on the distance from the nozzle, including particles and having an average particle diameter of about 30 μm. Moreover, when the ratio of air quantity / liquid quantity is increased with such an atomizer and the volume ratio is set to 1000: 1, there is a problem that it is difficult to generate stable mist.
Further, in order to cool a wide surface, a method of increasing the opening diameter of the nozzle is generally used, which requires a large amount of gas, which is not preferable from the viewpoint of noise. In order to cool a wide surface, the gas amount can be optimized by enlarging with a general air blow porous nozzle, but the mist is ejected intermittently from several uneven holes.

  When the conventional atomizer with such characteristics is used for cooling using latent heat of vaporization (heat of vaporization), large particles adhere to the cooling surface, hindering the cooling efficiency and ineffective liquid. Environmental problems such as consuming large amounts of (chemicals) have been created.

In order to improve this point, a method of dropping a liquid into an air flow used for fuel supply of a combustion engine or the like is also conceivable. However, as the apparatus becomes large-scale, stable particle distribution and concentration are possible. There is a problem that a satisfactory cooling effect cannot be obtained.
In particular, since the atomizing device and the processing unit are separated from each other in a large device, the mist is increased in the pipe for transferring the mist and adheres to the piping wall, resulting in intermittent liquid injection to the processing site. In many cases, it is different from the original generated mist, and it has not been put to practical use.

  The present invention has been made in view of the above problems, and its purpose is to generate micromist (droplets having an average particle size of 10 μm or less) near the surface to be cooled by pressurized gas even when cooling with a small amount of liquid. And providing a method and apparatus for generating micromist that can efficiently cool a wide area.

The present invention provides, as means for solving the above-mentioned problems, a micromist generation method and an apparatus therefor described in each claim.
According to a first aspect of the present invention, there is provided a method for generating micromist, wherein a liquid is sucked by a negative pressure when a pressurized gas for generating mist is ejected, and the mist ejected from an air-fuel mixture outlet as a gas-liquid mixture is introduced into an introduction pipe. It is guided, transported, and swirled in a swirling space in the spray nozzle, and then ejected as micromist from a plurality of spray holes. In this way, by providing the introduction pipe, it is possible to secure a time for the fine particles misted under the pressurized gas to dissolve the pressurized gas in the liquid, and to enhance the expansion effect of the pressurized gas dissolved inside during the injection. In addition to increasing the particle size, the liquid can be uniformly dispersed by swirling the mist, and a wide range of cooling can be performed with a small amount of liquid and gas.

The method for generating micromist according to claim 2 stipulates that the average particle size of the micromist is 10 μm or less, whereby cooling can be performed by effectively using the latent heat of vaporization of fine particles, and a small amount of liquid can be used. Cooling efficiency can be increased. According to a third aspect of the present invention, the amount of mist to be jetted can be arbitrarily adjusted by an adjustment valve provided in the liquid supply system, whereby the mist particle size distribution and concentration can be adjusted. The optimum supply conditions can be obtained and stable supply is possible.
According to the fourth aspect of the present invention, the gas flow rate of the pressurized gas is adjusted by adjusting the gas pressure, whereby the gas / liquid mixing balance is adjusted.

The micro mist generating apparatus according to claim 5 introduces a liquid stored in a liquid tank and a pressurized gas for generating mist, and a gas-liquid mixing unit that ejects the mist of the gas-liquid mixture, and this gas-liquid It has an introduction pipe that conveys the mist of the mixture to the injection nozzle, and an injection nozzle that injects the mist of the conveyed gas-liquid mixture as a micro mist from a plurality of injection holes. A swivel tip is provided. Thereby, the same effect as the micro mist generation method of claim 1 can be obtained.
According to a sixth aspect of the present invention, there is provided the liquid mist generating apparatus further comprising an adjustment valve for adjusting a mist amount of the gas-liquid mixture in a liquid supply system that connects the liquid tank and the gas-liquid mixing unit. The distribution and concentration of the diameter can be arbitrarily adjusted, and it is possible to obtain an optimum supply condition and to supply stably.

According to a seventh aspect of the present invention, the pressurized gas for generating mist is branched and introduced into the liquid tank, so that the gas and the liquid are supplied to the gas-liquid mixing section at the same pressure. Therefore, the amount of the liquid can be controlled by reducing the pressure so that the gas pressure slightly decreases in the portion by the ejector action in the gas-liquid mixing portion.
The micro mist generator according to claim 8 is such that the introduction tube is formed of polytetrafluoroethylene (PTFE) (trade name: Teflon), whereby the surface of the introduction tube can be made smooth. The droplets that have increased in size during the mist conveyance can be sent to the ejection nozzle without stagnation.

The micro mist generator according to claim 9 is provided with a flexible protective tube so as to surround the introduction tube, and thus the gas-liquid mixing unit is made flexible by making the protective tube flexible. Even if this part is fixed to the apparatus, the injection nozzle can be installed at an appropriate angle on the processing part, and the cooling of the processing part can be optimized.
The micro mist generating device of claim 10 is one in which the diameter φ of the injection hole of the injection nozzle is defined to be about 0.8 to 1.0 mm, whereby the mist transmitted through the side wall of the injection nozzle becomes a large particle. It is possible to prevent the liquid from jumping out from the edge surface of the injection hole and becoming an invalid liquid.

  Hereinafter, a micro mist generation method and apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view and a front view showing the overall configuration of the micromist generator of the present invention. The micro mist generating apparatus of the present invention stores a liquid coolant, a micro mist generating nozzle 1 composed of a gas-liquid mixing unit 2, an injection nozzle 3 incorporating a swivel tip 31, and an introduction pipe 4 connecting them, and a coolant. The liquid tank 5 is composed of a piping system that connects them systematically.

  The gas-liquid mixing part 2 has a gas introduction part 21 and an ejector part 22, and a gas outlet 23 is formed at the boundary between them. The gas introduction portion 21 is connected to the gas supply piping system 6, and a pressurized gas for generating mist (for example, about 0.4 Mpa) is introduced and injected from the gas injection port 23 to the ejector portion 22. A coolant injection port 24 is formed in the peripheral wall of the ejector portion 22, and is connected to the coolant supply piping system 7 connected to the liquid tank 5. Therefore, in this ejector portion 22, the coolant is sucked from the coolant injection port 24 due to the negative pressure of the pressurized gas when being injected from the gas injection port 23, and as a mist of the gas-liquid mixture, the ejector portion 22 It is sent to the introduction pipe 4 from the air-fuel mixture injection port 25 which is the tip opening.

The mist of the gas-liquid mixture introduced into the introduction pipe 4 is conveyed to the introduction pipe 4 and sent to the injection nozzle 3. The introduction pipe 4 needs to have a smooth inner wall surface in order to send droplets that have increased in size during mist conveyance to the injection nozzle 3 without staying. Preferably, polytetrafluoroethylene (PTFE) (PTFE) ( (Trade name: Teflon). Note that the inner surface of the introduction tube 4 may be smoothed by a coating film, a film, or the like. Moreover, since the introduction pipe 4 may be used by being bent, it is made of a soft material.
The introduction tube 4 is provided with a flexible protective tube 41 so as to surround the entire length of the introduction tube 4. The protective tube 41 is preferably a stainless steel (SUS) spiral tube so that the bent shape can be maintained.

  The spray nozzle 3 is provided with a swirl space, and a swirl tip 31 is disposed here. When the mist sent from the introduction pipe 4 collides, the swirl tip 31 disperses the mist in the radial direction and creates a swirl flow. A plurality of injection holes 32 are formed in the tip surface of the injection nozzle 3 in an annular shape at regular intervals in the circumferential direction. The number of the injection holes 32 is, for example, 6 to 8 (eight in FIG. 1), and the hole diameter φ is preferably about 0.8 to 1.0 mm. The inner surface structure of the injection nozzle 3 is preferably formed in a shape along the stream line of mist, and the inner surface is polished by sandblasting or the like to remove burrs.

  The liquid tank 5 in which the cooling liquid is stored has a pressure resistant structure capable of withstanding a pressure of approximately 1.0 MPa, so that the pressurized gas is branched into the tank from the gas supply piping system 6. It has become. Accordingly, the gas and liquid having the same pressure are introduced into the gas-liquid mixing unit 2. The gas supply piping system 6 for pressurized gas for generating mist is provided with an ON / OFF valve 61, and the cooling fluid supply piping system 7 for supplying the cooling fluid is cooled in addition to the ON / OFF valve 71. A liquid adjustment valve 72 is provided. By adjusting the adjustment valve 72, the amount of mist generated can be arbitrarily adjusted.

  The operation of the micromist generator of the present invention having the above-described configuration will be described below. In order to generate micro mist (droplets having an average particle diameter of 10 μm or less), a coolant from the liquid tank 5 and a pressurized gas for generating mist are introduced into the gas-liquid mixing unit 2. That is, the ejector portion 22 of the gas-liquid mixing unit sucks the cooling liquid from the cooling liquid injection port 24 through the cooling liquid supply piping system 7 by the negative pressure when the pressurized gas is injected from the gas injection port 23, and mixes the gas and liquid. It is injected into the introduction pipe 4 from the mixture injection port 25 as a body mist. The particle distribution of the mist at this time is a large particle mist similar to that generated by the conventional two-fluid nozzle.

  The mist of the gas-liquid mixture injected into the introduction pipe 4 is introduced into the injection nozzle 3 having the swivel tip 31 built therein, and swirls in the swirling space provided in the injection nozzle 3 by the swiveling action of the swivel tip 31. And it ejects as a micro mist from the some injection hole 32 provided in the front end surface of the injection nozzle 3. FIG.

  During the period from the generation of the mist to the ejection to the outside, in the configuration of the present invention, the pressurized gas is dissolved until the fine particles misted under pressure are saturated in the liquid. Due to the expansion effect of this, the action of tearing the liquid is generated even with a slight pressure reduction, and the liquid is micro-misted by the action of lowering the pressure by injection. The micromist particle distribution (particle diameter and particle number distribution) generated by the above operation is a graph distribution as shown in FIG. 2, and the average particle diameter of the mist is about 8 μm, which is the target of the present invention. It is injected as micro mist.

The numerical value of the specification which is the Example of the micro mist generator of this invention is as follows.
Pressurized gas pressure 0.4 Mpa, pressurized gas flow rate 100-200 L / min,
Coolant flow rate 1-5cc / min, liquid tank (5) pressure resistance 1.0Mpa,
The diameter of the gas injection port (23) is 2 mm, the diameter of the cooling liquid injection port (24) is 0.6 mm,
Inner diameter of introduction pipe (4) 4 mm, length of protection pipe (41) <300 mm
Number of injection holes (32) 6-8, injection hole (32) hole diameter φ 0.8-1.0 mm
Based on the above specifications, micromist having an average particle diameter of about 8 μm is achieved, but the numerical values of these specifications are only one example of the present invention.

  In general, in order to utilize the cooling by the mist for the cooling of a wide area, it is necessary to increase the area of the injection hole with the increase of the flow rate of the pressurized gas. However, when the hole diameter of the nozzle is simply increased, the mist transmitted along the inner wall of the nozzle jumps out as a large particle from the edge surface of the injection hole and becomes an ineffective liquid. Empirically, the mist from the injection hole having a hole diameter of about 1 mm is less likely to have such a phenomenon. This is thought to be due to the loss of the relative velocity with the liquid due to the influence of the gas injection flow rate.

  Therefore, in the injection nozzle of one embodiment of the present invention, the injection amount is ensured by setting the hole diameter φ of the injection hole to 0.8 mm and increasing the number of holes. In this case, there is how to uniformly disperse the liquid in each injection hole. Therefore, in the present invention, a swirl flow is created by the swirl tip, and the liquid is rotated in the spray nozzle to perform uniform dispersion. Furthermore, the introduction pipe is provided to ensure the time for dissolving the gas in the liquid, and the expansion effect at the time of injection is enhanced to increase the formation of fine particles (micro mist).

  FIG. 3 is a diagram showing a specific example in which the micro mist generator of the present invention is applied to cooling of a cutting tool for dry cutting. Cutting is performed while removing the processing heat generated when the workpiece W is cut by the blade K by the high pressure air blow including the micro mist M generated by the micro mist generator of the present invention. In the micro mist generating nozzle, the introduction tube 4 (protection tube 41) is bent so that the generated micro mist M is accurately sprayed onto the processing portion. In this way, the processing heat at the interface between the workpiece W and the cutting tool K generated by cutting the workpiece W is cooled by a cooling gas (micro mist M) in which a large amount of air and a small amount of cooling liquid are mixed. It can be efficiently cooled by the heat of vaporization. Due to this cooling effect, the tool life could be improved by double that of dry cutting and 1.4 times that of wet cutting.

Moreover, in the specific example shown in FIG. 3, the liquid tank 5 of the cooling liquid is installed in a place away from the processing part of the processing machine and cooled by the micro mist generating nozzle 1 provided in the vicinity of the processing part. It is possible to solve the intermittent spray phenomenon due to the increase in the particle size during the mist conveyance and the lack of cooling which are problems in the apparatus.
Further, since the micro mist M is generated by converting a super-saturated mist (a mist in which pressurized gas is dissolved to a saturated state by pressurization) into a micro mist by an expansion effect at the time of injection, the mist is generated in the introduction pipe 4. Since stable micro mist can be obtained even when the particle size is increased, the introduction pipe 4 of the micro mist generating nozzle 1 can be bent in accordance with the posture of the processed portion as shown in FIG. 3, and cooling can be optimized. It becomes. In the embodiment of the present invention, for this purpose, the mist introducing portion has a double structure, the introduction tube 4 for introducing the mist employs a PTFE tube having a smooth inner wall, and the protective tube 41 is made of SUS that maintains a bent shape. The spiral tube is adopted. By configuring the micro mist device of the present invention in such a configuration, even if the part of the gas-liquid mixing unit 2 is fixed to the device, the injection nozzle 3 can be installed at an appropriate angle on the processing part, and the composite Stable and highly efficient cooling can be realized by a synergistic effect with a wide injection area by the individual injection holes 32.

As described above, the method and apparatus for generating micromist of the present invention can efficiently and efficiently cool and process a workpiece with a small amount of cooling liquid. In addition, the fine particle effect of micro mist that has not been available in the past makes it possible to introduce the generated mist into a minute space that has been difficult to cool in the past, and a flexible supply system can be used for difficult cooling needs. Therefore, a reliable cooling action can be performed without being affected by the installation space.
Furthermore, in the micro mist generation method of the present invention, the particle size distribution and concentration can be arbitrarily adjusted by a mist amount adjustment valve (coolant adjustment valve) provided in the micro mist generation nozzle. And a stable supply can be performed.

  In the above description, the micro mist generator according to the present invention is used as an example for removing the processing heat during cutting. However, the chemical liquid is finely applied, such as chemical application or surface treatment (cleaning / etching). The micromist generator of the present invention can be applied to any application as long as the system is supplied with gas.

It is the sectional side view and front view which show the whole structure of the micro mist generator of embodiment of this invention. It is a graph which shows the particle distribution of the micro mist obtained by the micro mist generator of this invention. It is a figure which shows the specific example which used the micro mist generator of this invention for the removal of process heat. It is a figure explaining the conventional (a) atomizer and (b) generated mist distribution.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Micro mist generating nozzle 2 ... Gas-liquid mixing part 21 ... Gas introduction part 22 ... Ejector part 23 ... Gas injection port 24 ... Coolant injection port 25 ... Mixture injection port 3 ... Injection nozzle 31 ... Swirling tip 32 ... Injection hole 4 ... Introducing pipe 41 ... Protective pipe 5 ... Liquid tank 6 ... Pressurized gas supply piping system 7 ... Coolant supply piping system 72 ... Coolant adjustment valve M ... Micro mist K ... Cutting tool W ... Workpiece

Claims (10)

In the micro mist generation method of atomizing and releasing liquid into a micro mist state,
The liquid is sucked by the negative pressure generated when the pressurized gas for mist generation introduced into the gas-liquid mixing section is ejected, and the mist ejected from the gas-gas mixture outlet as a gas-liquid mixture is guided to the introduction pipe and conveyed Then, the micro mist generation method is characterized in that the micro mist is sprayed from a plurality of spray holes of the spray nozzle after swirling in a swirl space provided in the spray nozzle.   2. The method of generating micro mist according to claim 1, wherein the micro mist comprises liquid fine particles having an average particle size of 10 [mu] m or less.   3. The method of generating micro mist according to claim 1, wherein the amount of mist to be ejected can be arbitrarily adjusted by an adjustment valve provided in a liquid supply system.   4. The method of generating micromist according to claim 1, wherein the gas flow rate of the pressurized gas is adjusted by adjusting a gas pressure. A micromist generator that atomizes and discharges liquid into a micromist state.
A gas-liquid mixing unit into which a liquid stored in a liquid tank and a pressurized gas for generating mist are introduced, wherein the liquid is sucked by a negative pressure when the pressurized gas is injected, and a gas-liquid mixture The gas-liquid mixing section that injects from the air-fuel mixture injection port as a mist of
An introduction pipe for conveying the mist of the gas-liquid mixture ejected from the gas mixture ejection port to the ejection nozzle;
An injection nozzle that injects the mist of the conveyed gas-liquid mixture as micromist from a plurality of injection holes;
Comprising
The micro mist generator according to claim 1, wherein the spray nozzle has a built-in turning tip for turning the mist of the introduced gas-liquid mixture.   6. The liquid supply system connecting the liquid tank and the gas-liquid mixing unit is further provided with an adjustment valve for adjusting the mist amount of the gas-liquid mixture. Micro mist generator.   The micromist generator according to claim 5 or 6, wherein the pressurized gas is branched and introduced into the liquid tank.   The micro mist generator according to any one of claims 5 to 7, wherein the introduction tube is made of polytetrafluoroethylene.   The micro mist generator according to claim 5, wherein a flexible protective tube is provided so as to surround the introduction tube.   The micro mist generating device according to any one of claims 5 to 9, wherein a diameter φ of an injection hole of the injection nozzle is about 0.8 to 1.0 mm.

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