JP2017148792A - Liquid jet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid jet device that jets liquid, which can effectively suppress the liquid from being frozen.SOLUTION: The liquid jet device comprises: a storing portion 12 that stores liquid; a compressing portion 13 that transports the liquid from the storing portion 12 by compressing the liquid; and a jetting portion 11 that jets the compressed liquid to a space 10 to which is jetted the liquid. The liquid contains water and hydrogen peroxide less than the water, and the liquid further contains a degradation inhibitor that inhibits degradation of the hydrogen peroxide. The degradation inhibitor is composed mainly of alcohol. A surface which contacts the liquid, in at least any of the storing portion, the compressing portion and the jetting portion, is subjected to erosion resistant treatment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid ejecting apparatus that ejects liquid.

  When the liquid is chemically reacted or evaporated, the gas-liquid interface is increased in order to improve the efficiency. As one method for increasing the gas-liquid interface, so-called “jetting” for atomizing a liquid is well known.

  The liquid ejecting apparatus generally includes a storage unit that stores liquid, a pressurization unit that transports and pressurizes the liquid from the storage unit, and a atomization unit that atomizes the pressurized liquid. The atomization portion includes a cylindrical portion having a through hole formed on the tip side, and a valve body that opens and closes the through hole. The liquid pressurized by the pressurizing unit is supplied to the cylindrical unit and is discharged out of the cylindrical unit through the through hole. The discharge mode of the liquid is controlled by opening and closing the through hole by the valve body, and the amount and particle size of the droplets to be atomized are adjusted.

  Liquid ejecting apparatuses have a wide variety of uses, and various types of liquids are required. For example, in the urea SCR system described in Patent Document 1 for reducing nitrogen oxides (NOx) in exhaust gas, suppression of freezing of water contained in an aqueous urea solution is required. The urea aqueous solution achieves a certain degree of freezing suppression by the freezing point depression based on urea.

JP 2000-303826 A

  However, a sufficient freezing point depression cannot be obtained only by containing urea in the liquid, and there is a large room for freezing suppression. Further, ethylene glycol generally used as a freezing point depressant is not preferable in terms of thermophysical properties and viscosity. Further, when the liquid temperature is maintained higher than the freezing point by the heater to prevent freezing, the fuel consumption is deteriorated.

  SUMMARY An advantage of some aspects of the invention is that in a liquid ejecting apparatus that ejects liquid, freezing of the liquid is effectively suppressed.

  In order to achieve the above object, according to the first aspect of the present invention, a reservoir (12) that stores liquid, a pressurizer (13) that pressurizes and transports liquid from the reservoir, and a pressurized liquid An injection unit (11) that injects the liquid into the injection target space (10), and the liquid contains water and a smaller amount of hydrogen peroxide than water.

  Thereby, the freezing point of a liquid can be lowered | hung by using hydrogen peroxide aqueous solution as a liquid injected from an injection valve, and freezing can be suppressed effectively. The aqueous hydrogen peroxide solution has an excellent antifreeze function and is excellent in terms of thermal conductivity and viscosity.

  Further, by adding a decomposition inhibitor to the aqueous hydrogen peroxide solution, the decomposition of the hydrogen peroxide can be suppressed for a long time, and the aqueous hydrogen peroxide solution can be used stably. In particular, by using an alcohol-based decomposition inhibitor, a high decomposition inhibitory effect of hydrogen peroxide can be obtained.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

1 is an overall schematic configuration diagram of a liquid ejecting apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure of an injection valve. It is the figure which showed correlation with the freezing point of a liquid, and the density | concentration of a solute. It is a figure for demonstrating the effect of a decomposition inhibitor. It is the figure which showed the correlation with the temperature of hydrogen peroxide aqueous solution, and a decomposition rate. It is a figure which shows the decomposition rate of hydrogen peroxide at the time of making the hydrogen peroxide aqueous solution contain a different kind of decomposition inhibitor. It is a figure which shows the change of the hydrogen peroxide density | concentration at the time of heating and cooling of hydrogen peroxide aqueous solution repeatedly.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the liquid ejecting apparatus according to the present embodiment includes an ejection valve 11 that ejects liquid into an ejection target space 10. The injection target space 10 can be a combustion chamber or an exhaust pipe of an internal combustion engine. Hereinafter, the liquid ejected from the ejection valve 11 is referred to as “ejection liquid”.

  The injection valve 11 is attached to a wall portion of the injection target space 10 and can inject the injection liquid by atomizing the injection target space 10. The jet liquid of this embodiment is a hydrogen peroxide aqueous solution containing hydrogen peroxide and water. The jet liquid will be described later in detail.

  The injection liquid supplied to the injection valve 11 is stored in the tank 12. The tank 12 is a sealed container having a predetermined capacity. The tank 12 corresponds to the “reservoir” of the present invention.

  Inside the tank 12, a pump 13 that sucks out the jet liquid stored in the tank 12 and supplies the jet liquid to the jet valve 13 is provided. A liquid supply path 14 that connects the pump 13 and the injection valve 11 is connected to the tank 12.

  By driving the pump 13, the jet liquid stored in the tank 12 is pressurized and transported to the jet valve 11. The pump 13 is an electric pump whose rotation speed (liquid supply amount) is controlled by a control signal output from a control device 15 described later. The pump 13 corresponds to the “pressurizing part” of the present invention.

  As shown in FIG. 2, the injection valve 11 includes a substantially columnar needle 110 and a substantially cylindrical nozzle body 111 that accommodates the needle 110 therein. These needle 110 and nozzle body 111 are made of metal. The needle 110 corresponds to the “valve element” of the present invention, and the nozzle body 111 corresponds to the “tubular portion” of the present invention.

  The needle 110 is slidably held on the nozzle body 111. The needle 110 is configured to reciprocate in the nozzle body 111 along the axial direction of the needle 110 and the nozzle body 111 (the vertical direction in FIG. 2, hereinafter simply referred to as the axial direction).

  The needle 110 has two tapered surfaces 110b and 110c formed at the tip. A sheet portion 110d, which is an annular ridgeline, is formed at the boundary between these two tapered surfaces 110b and 110c.

  The nozzle body 111 includes a nozzle inner space 111a through which the jet liquid supplied from the tank 12 can flow. The nozzle body 111 is provided with a plurality of injection holes 111b at the tip of the nozzle body 111, which communicate with the nozzle internal space 111a and the outside and serve as injection outlets for the injection liquid.

  The nozzle hole 111b is formed as a through hole having a circular cross-sectional shape. One end side of the nozzle hole 111b opens into the nozzle internal space 111a, and the other end side opens to the outside.

  As the needle 110 reciprocates in the axial direction, the sheet portion 110 d of the nozzle 110 contacts or separates from the inner wall surface 111 c of the nozzle body 111. Thereby, the nozzle inner space 111a is communicated or blocked, and the nozzle hole 111c is opened and closed. When the nozzle hole 111c is opened, the atomized liquid is ejected from the nozzle hole 111b.

  The control device 15 includes a known microcomputer including a CPU, ROM, RAM, and the like and peripheral circuits thereof. Then, various operations and processes are performed based on the control program stored in the ROM to control the operation of various devices connected to the output side.

  The injection valve 11 and the pump 13 described above are connected to the output side of the control device 15. A sensor group such as a pressure sensor 16 for detecting the pressure of the jet liquid flowing through the liquid supply path 14 and a temperature sensor 17 for detecting the temperature of the jet liquid flowing through the liquid supply path 14 are connected to the input side of the control device 15. Has been.

Next, the jet liquid will be described. As described above, in this embodiment, an aqueous hydrogen peroxide solution containing water (H ₂ O) and hydrogen peroxide (H ₂ O ₂ ) is used as the jet liquid. Hydrogen peroxide functions as a freezing point depressant.

The molecular structure “HO—OH” of hydrogen peroxide is such that the distance of the bond chain from one O atom to the other O atom in the OH group is such that the molecular structure “HO—CH ₂ ” of a general ethylene glycol as a freezing point depressant It is shorter than the distance corresponding to the bond chain between OH groups in “—CH ₂ —OH”.

  Since the arrangement of water molecules is destroyed by hydrogen peroxide having such a molecular structure, the hydrogen peroxide aqueous solution can have the same antifreeze function as the ethylene glycol aqueous solution. The aqueous hydrogen peroxide solution has a thermal conductivity and viscosity equivalent to that of water, and is superior to the aqueous ethylene glycol solution in terms of thermal conductivity and viscosity.

  Here, the freezing point of the aqueous hydrogen peroxide solution will be described. As shown in FIG. 3, in the aqueous ethylene glycol solution, the ethylene glycol concentration needs to be 50 wt% or more in order to obtain the target freezing point of −34 ° C. In contrast, the aqueous hydrogen peroxide solution is equivalent to the ethylene glycol aqueous solution by setting the hydrogen peroxide degree (that is, the ratio of hydrogen peroxide to the total amount of water and hydrogen peroxide) to 30 wt% or more. Freezing point is obtained.

  In order to sufficiently reduce the freezing point of the aqueous hydrogen peroxide solution and suppress freezing, it is desirable that the hydrogen peroxide concentration be 15 wt% or more. In addition, it is desirable that the concentration of hydrogen peroxide, which is a freezing point depressant in the hydrogen peroxide solution, be as low as possible, and even if the concentration of hydrogen peroxide is increased more than necessary, the effect of lowering the freezing point is reduced, so It is desirable that the hydrogen concentration be 50 wt% or less.

  By the way, hydrogen peroxide has an unstable bond and is easily decomposed into water and oxygen. That is, the aqueous hydrogen peroxide solution is less stable than the aqueous ethylene glycol solution or water. For this reason, in order to use an aqueous hydrogen peroxide solution as a jet liquid, it is necessary to ensure the decomposition stability of hydrogen peroxide.

  In this embodiment, the hydrogen peroxide solution contains a decomposition inhibitor for suppressing the decomposition reaction of hydrogen peroxide. As the decomposition inhibitor, for example, an OH radical scavenger such as a chelate, Ta ion, or organic acid can be used. These decomposition inhibitors function as a negative catalyst that slows the decomposition rate of hydrogen peroxide. Any of the decomposition inhibitors such as chelates, Ta ions, and organic acids may be used alone or in combination of two or more.

  As shown in FIG. 4, activation energy (that is, energy barrier) required for the decomposition reaction of hydrogen peroxide is increased by a negative catalyst such as a chelate, Ta ion, or organic acid, and the decomposition rate is made substantially zero. Can do. That is, the decomposition of hydrogen peroxide can be suppressed by adding a decomposition inhibitor to the hydrogen peroxide solution.

  The higher the concentration of the decomposition inhibitor in the aqueous hydrogen peroxide solution, the higher the effect of suppressing the decomposition of hydrogen peroxide. However, if the decomposition inhibitor concentration is too high, the proportion of water in the aqueous hydrogen peroxide solution is lowered. Therefore, it is desirable that the concentration of the decomposition inhibitor is as low as possible.

  In the present embodiment, the decomposition inhibitor concentration (the ratio of the decomposition inhibitor relative to the sum of the amount of water and the amount of hydrogen peroxide) is set to 1/10 or less of the hydrogen peroxide concentration of the hydrogen peroxide solution. Yes. Further, since the decomposition inhibitor itself decreases due to decomposition, it is desirable to set the concentration of the decomposition inhibitor to which a decrease is added in advance. For example, when the hydrogen peroxide concentration is 50 wt% or less, the decomposition inhibitor concentration may be 6 wt% or less obtained by adding 1 wt% as a decrease to 5 wt% which is 1/10 of the hydrogen peroxide concentration. desirable.

  Moreover, piping etc. which the hydrogen peroxide aqueous solution as a jet liquid contacts are often comprised from metals, such as aluminum. When a metal such as aluminum is contained in the hydrogen peroxide solution, the energy barrier is lowered and the decomposition rate of hydrogen peroxide is increased. Furthermore, the decomposition reaction is accelerated as the temperature of the aqueous hydrogen peroxide solution increases.

  FIG. 5 shows the result of an accelerated test in which a hydrogen peroxide solution having a hydrogen peroxide concentration of 30 wt% is heated at 100 ° C. In FIG. 5, an alternate long and short dash line indicates an aqueous hydrogen peroxide solution that does not contain aluminum and a decomposition inhibitor, a broken line indicates an aqueous hydrogen peroxide solution that contains aluminum and does not contain a decomposition inhibitor, and a solid line indicates aluminum and 2 shows an aqueous hydrogen peroxide solution containing a decomposition inhibitor. As a decomposition inhibitor, 4 wt% of chelate was contained.

  As shown by the broken line and the dashed line in FIG. 5, in the hydrogen peroxide aqueous solution that does not contain the decomposition inhibitor, the decomposition rate of hydrogen peroxide is significantly increased by containing aluminum. On the other hand, in the hydrogen peroxide aqueous solution containing the decomposition inhibitor, the decomposition rate was suppressed to 1/20 compared with the hydrogen peroxide aqueous solution containing aluminum and not containing the decomposition inhibitor. Thus, by including a decomposition inhibitor in the aqueous hydrogen peroxide solution, high decomposition stability can be obtained even if a metal such as aluminum is contained.

  FIG. 6 shows the results of a test in which different types of decomposition inhibitors are contained in an aqueous hydrogen peroxide solution having a hydrogen peroxide concentration of 30 wt% and heated at 100 ° C. for 5 hours. In FIG. 6, A shows a hydrogen peroxide aqueous solution containing no decomposition inhibitor, and B to E show hydrogen peroxide aqueous solutions containing 6 wt% of the decomposition inhibitor. B contains the first phosphate decomposition inhibitor (trade name “PH540”, Kirest Co., Ltd.), and C contains the second phosphate decomposition inhibitor (trade name “PH212”, Kirest Co., Ltd.) D contains a third phosphoric acid-based decomposition inhibitor (trade name “Kiresbit D”, Kirest Corporation), and E represents an alcohol-based degradation inhibitor (trade name “Kiresbit C-4”, Kirest Corporation). Contains.

  As shown in FIG. 6, the aqueous hydrogen peroxide solution containing no decomposition inhibitor has a decomposition rate of 24%, whereas the aqueous hydrogen peroxide solution containing the decomposition inhibitor is greatly reduced in decomposition rate. In particular, the aqueous hydrogen peroxide solution containing an alcohol-based decomposition inhibitor had a decomposition rate of 0.1%.

  That is, when the alcohol-based decomposition inhibitor is used, the decomposition rate of hydrogen peroxide is lowest, and the decomposition of hydrogen peroxide can be effectively suppressed. The alcohol-based decomposition inhibitor used in the present embodiment contains at least one of phenoxydiethylene glycol represented by the following chemical formula 1 and dipropylene glycol represented by the following chemical formula 2 as a main component.

  FIG. 7 shows the change in the hydrogen peroxide concentration when the aqueous hydrogen peroxide solution is repeatedly heated at 100 ° C. for 10 hours and cooled at room temperature for 10 hours. FIG. 7 shows an aqueous hydrogen peroxide solution containing an alcohol-based decomposition inhibitor (trade name “Kiresbit C-4”, Kirest Co., Ltd.) and an aqueous hydrogen peroxide solution not containing a decomposition inhibitor.

  As shown in FIG. 7, the aqueous hydrogen peroxide solution containing the decomposition inhibitor shows a tendency to decrease the hydrogen peroxide concentration for each subsequent heating, but the hydrogen peroxide solution does not contain the decomposition inhibitor. Compared to an aqueous solution, the decrease in the hydrogen peroxide concentration can be suppressed for a long time.

  According to the present embodiment described above, by using an aqueous hydrogen peroxide solution as the jet liquid ejected from the jet valve 11, the freezing point of the jet liquid can be lowered and freezing can be effectively suppressed. The aqueous hydrogen peroxide solution has an excellent antifreeze function and is excellent in terms of thermal conductivity and viscosity.

  Moreover, in this embodiment, the decomposition inhibitor is contained in the hydrogen peroxide aqueous solution used as the jet liquid. Thereby, decomposition | disassembly of the hydrogen peroxide contained in hydrogen peroxide aqueous solution can be suppressed over a long time, and hydrogen peroxide aqueous solution can be used stably as a jet liquid. In particular, by using an alcohol-based decomposition inhibitor, a high decomposition inhibitory effect of hydrogen peroxide can be obtained.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows without departing from the spirit of the present invention. Further, the means disclosed in each of the above embodiments may be appropriately combined within a practicable range.

  For example, in the above embodiment, the surface of the injection valve 11, the tank 12, the pump 13, the liquid supply path 14, etc. that contacts the injection liquid may be subjected to corrosion resistance treatment. When the jet liquid is used at a high temperature and high pressure, the portion in contact with the jet liquid is likely to corrode, and thus it is desirable to perform the corrosion resistance treatment in this way. For example, in the case of the injection valve 11, the outer surface of the needle 110 and the inner wall surface of the nozzle body 111 may be subjected to corrosion resistance treatment. The corrosion resistance treatment can be performed by chemical conversion treatment or plating treatment, for example.

  The surface composition formed by the chemical conversion treatment can be, for example, alumite. If the base material is aluminum, alumite may be formed on the surface, and if the base material is a metal other than aluminum, an aluminum layer may be provided on the surface and alumite may be formed on the surface of the aluminum layer. Moreover, the surface composition formed by the plating process can be, for example, nickel.

10 Injection target space 11 Injection valve 110 Needle (valve element)
111 Nozzle body (cylinder part)
12 tanks (reservoir)
13 Pump (pressurizing part)
14 Liquid supply path

Claims (11)

A reservoir (12) for storing liquid;
A pressurizing unit (13) for pressurizing and transporting the liquid from the storage unit;
An injection unit (11) for injecting the pressurized liquid into the injection target space (10),
The liquid ejecting apparatus, wherein the liquid includes water and a smaller amount of hydrogen peroxide than the water.   2. The liquid ejecting apparatus according to claim 1, wherein the liquid has a ratio of the hydrogen peroxide of 15 wt% or more with respect to a total amount of the water and the hydrogen peroxide.   The liquid ejecting apparatus according to claim 1, wherein the liquid includes a decomposition inhibitor that suppresses decomposition of the hydrogen peroxide.   The liquid ejecting apparatus according to claim 3, wherein the decomposition inhibitor includes alcohol as a main component. 5. The liquid ejecting apparatus according to claim 4, wherein the alcohol is at least one of a substance represented by the following chemical formula 1 and a substance represented by the following chemical formula 2.

  6. The liquid ejecting apparatus according to claim 3, wherein a ratio of the decomposition inhibiting material to a total of the amount of water and the amount of hydrogen peroxide is 6 wt% or less.   The liquid ejecting apparatus according to any one of claims 1 to 6, wherein a surface in contact with the liquid is subjected to a corrosion resistance process in at least one of the storage unit, the pressurizing unit, and the ejecting unit.   The liquid ejecting apparatus according to claim 7, wherein the corrosion resistance treatment is at least one of a chemical conversion treatment and a plating treatment.   The liquid ejecting apparatus according to claim 8, wherein a surface composition formed by the chemical conversion treatment is alumite.   The liquid ejecting apparatus according to claim 8, wherein a surface composition formed by the plating process is nickel. The injection portion includes a cylindrical portion (111) having a through hole (111c) formed at a tip thereof, and a valve body (110) that opens and closes the through hole,
The cylindrical portion and the valve body are made of metal,
11. The liquid ejecting apparatus according to claim 7, wherein surfaces of the cylindrical portion and the valve body that are in contact with the liquid are subjected to the corrosion resistance treatment.

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