JP2006220072A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve capable of always maintain the excellent controllability of fuel injection amount by preventing the secular change of fuel injecting characteristics caused by the accumulation of deposits by suppressing the accumulation of deposits around a fuel injection hole. <P>SOLUTION: This fuel injection valve 1 is so formed that at least the inner peripheral surface 7a of the fuel injection hole 7 and the surface of the fuel injection hole 7 around its opening part (countermeasure-applied surface) are formed in a fractal structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection valve that injects fuel into a combustion chamber of an internal combustion engine. More specifically, the present invention relates to a fuel injection valve having a function of preventing deposits from being deposited around the fuel injection hole.

  In general, when an internal combustion engine is used for a long time without sufficient maintenance and inspection, solid deposits (deposits) adhere to the periphery of the fuel injection hole of the fuel injection valve. There are problems that normal fuel injection is hindered or that the state of fuel injection changes. Even if the amount of deposit does not reach the amount that completely closes the fuel injection hole, the injection amount per unit time at the time of fuel injection is reduced or injected due to partial blockage of the fuel injection hole. Since changes with time in the fuel injection characteristics such as the shape of the fuel spray and the size of the particles change, the controllability of the fuel injection valve deteriorates.

  The portion of the fuel injection valve where deposits are likely to occur is a portion where the fuel is likely to remain while the operation is stopped, or the portion where the fuel in the fuel injection hole tends to remain, and the temperature does not easily drop. It is a part. If a small amount of fuel remains or adheres to the periphery of the fuel injection hole of the fuel injection valve when the operation of the internal combustion engine is stopped, the residual fuel undergoes a chemical reaction under high temperature and changes its quality. It becomes a hard solid and sticks around the fuel injection hole. Specifically, the carbon component in which the specific hydrocarbon component in the residual fuel is decomposed and deposited by the dehydrogenation reaction, the corrosive acidic gas contained in the combustion gas remaining in the combustion chamber, or the fuel Substances generated by the chemical reaction of the specific components contained gradually accumulate as solid matter in the vicinity of the fuel injection hole, forming a deposit, reducing the cross-sectional area of the fuel injection hole, and the shape of the fuel injection hole To change. Then, the fuel flow is hindered to reduce the injection amount, or the ejection direction is changed to change the shape of the fuel spray to an abnormal shape. They all result in a decrease in the controllability of the fuel injector.

  For this reason, in order to suppress deposits deposited on the periphery of the injection hole of the fuel injection valve, a valve seat member for a fuel injection valve for an internal combustion engine provided with a water / oil repellent coating having a high deposition suppressing effect has been proposed ( Patent Document 1). The valve seat member has a water / oil repellent film made of an organosilicon compound on the surface thereof. Specifically, it is an organic silicon compound having a perfluoroalkyl group having 1 to 10 carbon atoms, which is a so-called fluorine coating.

However, in order to satisfy exhaust gas regulations that are becoming stricter, it is required to control the fuel injection amount with higher accuracy. On the other hand, in order to perform stratified combustion of fuel in the combustion chamber, it is necessary to arrange the fuel injection valve position from the side surface of the combustion chamber to the upper center. However, if the fuel injection valve is arranged at the upper center, the time required for the tip of the fuel injection valve (including the periphery of the fuel injection hole) to be exposed to high-temperature combustion gas increases. The temperature rises from around 250 ° C. to 250 ° C. to 300 ° C. For this reason, in the conventional fluorine coating, there is a possibility that the coating film is deteriorated and the fuel injection amount is changed due to deposit adhesion. Therefore, it is desired to develop a fuel injection valve having a high deposit accumulation suppressing effect at a higher temperature.
Japanese Patent Laid-Open No. 11-334881

  The present invention has been made in view of the above circumstances, and by suppressing the accumulation of deposits in the peripheral portion of the fuel injection hole, it is possible to prevent changes over time in the fuel injection characteristics caused by the deposition of deposits. It is an object of the present invention to provide a fuel injection valve capable of maintaining the controllability of the injection amount.

  The fuel injection valve of the present invention has a hollow shape, an inner peripheral cylindrical surface that defines a fuel flow path, an inner peripheral conical surface that defines a nozzle hole, and a valve seat formed on the inner peripheral conical surface. A main body having an outer peripheral cylindrical surface opposed to the inner peripheral cylindrical surface, and an outer peripheral conical surface facing the inner peripheral conical surface. A needle valve having a taper having a tapered portion, a valve portion that can be seated on the valve seat, a valve lift mechanism that moves the needle valve in an axial direction thereof, and a nozzle body at an opening portion of the nozzle hole. In a fuel injection valve having a fuel injection hole communicating therewith, at least an inner peripheral surface of the fuel injection hole and a surface around the opening of the fuel injection hole (hereinafter collectively referred to as a deposit prevention surface. The surface of the tip surrounded by A) is the fractor Characterized in that it is formed in the structure.

  In the fuel injection valve of the present invention, since at least the deposit-preventing surface of the nozzle body is formed in a fractal structure, these surfaces have high water and oil repellency. Therefore, when the fuel injection is stopped, the fuel hardly remains in the peripheral portion of the fuel injection hole, and the remaining fuel can be easily injected and removed by injecting the fuel, so that deposit accumulation can be suppressed.

  Here, a fractal means a generic name of a figure having a non-integer dimension, and a fractal structure means a structure formed in such a figure. For example, as described in the embodiments of the invention described later, this means a structure having a complicated uneven shape.

  The fuel injection valve of the present invention also includes a fuel injection valve having a nozzle plate attached to the nozzle body and formed with a plurality of fuel injection holes facing the opening of the nozzle hole. In the fuel injection valve having such a shape, spray patterns having various shapes can be obtained by forming the plurality of fuel injection holes of the nozzle plate in various modes.

  In the fuel injection valve of the present invention, it is desirable that at least the tip of the nozzle body is stainless steel. Since stainless steel has high heat resistance and corrosion resistance, it is a suitable material for the tip of the nozzle body that is exposed to high temperatures, and it can be formed into a fractal structure on the tip of the nozzle body by ion beam processing or the like. . Therefore, in the fuel injection valve of the present invention, it is possible to suppress deposit accumulation and always maintain good controllability of the fuel injection amount.

  Further, in the fuel injection valve of the present invention, it is desirable to have an anodized aluminum film on the surface against deposits. The aluminum anodic oxide coating has fine current-carrying holes formed during anodic oxidation, and the surface thereof can have a fractal structure. Therefore, in the fuel injection valve of the present invention, it is possible to suppress deposit accumulation and always maintain good controllability of the fuel injection amount.

  Further, in the fuel injection valve of the present invention, it is desirable to have a nickel-chromium-molybdenum alloy layer on the surface against deposits. For example, the surface of the obtained alloy layer can be made into a fractal structure by alloying a mixed powder of a nickel-chromium self-fluxing alloy and molybdenum on a stainless steel surface using a laser. Therefore, in the fuel injection valve having such an alloy layer, it is possible to suppress deposit accumulation and always maintain good controllability of the fuel injection amount.

  Furthermore, in the fuel injection valve of the present invention, it is desirable to have a fluororesin coating on the surface against deposits. By forming a fluororesin film on the stainless steel surface with a fractal structure, it is possible to further improve water and oil repellency, suppress deposit accumulation, and always maintain good controllability of the fuel injection amount Is possible.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 illustrates an outline of a fuel injection valve for an internal combustion engine.

  As shown in FIG. 1, a needle valve 3 is inserted into a generally cylindrical nozzle body 2 of the fuel injection valve 1 so as to be movable in the axial direction thereof. Driven. In the case of FIG. 1, when the solenoid coil 4 a that is a part of the valve lift mechanism 4 is energized, the needle valve 3 is sucked and raised, and the conical portion 3 a at the tip of the needle valve is the inner periphery of the nozzle body 2. The nozzle hole 6 is opened away from the seat portion (valve seat) 5 formed on the conical surface. The solenoid coil 4 is connected to a control device (not shown), and an electric pulse corresponding to a period during which fuel is injected by the fuel injection valve 1 is supplied to the solenoid coil 4 by the control device.

  The liquid fuel is pressurized by a pump (not shown), then passes through the central portion of the main body 2 of the fuel injection valve 1 through a pipe, and is closed by the tip of the conical portion 3a of the needle valve 3. When the nozzle hole 6 is opened by the needle valve 3 rising and separating from the seat portion 5 when the nozzle hole 6 is opened, the fuel is sprayed through the fuel injection hole 7 communicating with the nozzle hole 6, It is injected into a combustion chamber (not shown).

  In FIG. 1, the fuel injection hole 7 has a substantially fan-shaped cross section, and the opening 7c facing the nozzle hole 6 and the injection-side opening 7d are formed in a slit shape.

  In the fuel injection valve 1 having such a configuration, the present invention relates to the surface of the peripheral portion of the fuel injection hole 7, particularly the surface of the inner peripheral surface 7a of the fuel injection hole 7 and the periphery of the opening portion 7b of the fuel injection hole 7 (hereinafter, 2) is formed in a surface structure F having a complicated uneven shape as illustrated in FIG. 2, that is, a fractal structure.

  Note that the fuel injection valve of the present invention includes a fuel injection valve having a shape as shown in FIG. That is, the fuel injection valve has a nozzle plate 8 that is attached to the nozzle body 2 with a socket 9 at the tip of the nozzle body 2 and has a plurality of fuel injection holes 7 facing the openings of the nozzle holes 6. In the fuel injection valve of this embodiment, the inner peripheral surface 7a of the fuel injection hole 7, the periphery 7b of the downstream opening (the lower surface side of the nozzle plate 8) of the fuel injection hole 7, and the inner peripheral surface of the central hole 9a of the socket 9 are provided. This is a deposit-proof surface.

  Fractal means a generic name for figures having non-integer dimensions, and fractal structure means a structure formed in such figures. For example, it means a structure having a so-called self-similarity in which a structure obtained by reducing itself by a fraction is a part of itself. When a fractal figure is composed of b figures obtained by reducing itself to 1 / a, the dimension (similarity dimension) of the figure is given by logb / loga. For example, if the surface F shown in FIG. 2 is drawn with a = 3 and b = 4, log4 / log3 = 1.26...

  On the surface F formed in such a fractal structure, the liquid L such as fuel has a large contact angle θ with the solid S as shown in FIG. 3, so that the fractalized surface F has super water and oil repellency characteristics. Have The contact angle θ can be expressed by the following equation.

cos θ = (α2−α1) / α3 (1)
In the equation (1), α1, α2 and α3 indicate three forces acting on the contact point P between the liquid L and the solid S, as shown in FIG. 3, and α1 is the interfacial tension between the solid S and the liquid L. Α2 is the interfacial tension between the solid S and the gas G, and α3 is the interfacial tension between the gas G and the liquid L. Note that the contact point P corresponds to each of the points p1, p2,... In contact with the liquid L in FIG.

  In the fuel injection valve having the deposit countermeasure surface as described above, the first embodiment of the present invention is a fuel injection valve in which the tip of the nozzle body including at least the deposit countermeasure surface is formed of stainless steel. The countermeasure surface has a fractal structure as shown in FIG. Such a fractal structure can be formed, for example, by focused ion beam processing that irradiates a stainless steel surface with a Ga ion beam focused to 0.1 μmφ.

  The second embodiment of the present invention is a fuel injection valve having an aluminum anodic oxide coating on a deposit prevention surface around a fuel injection hole formed of stainless steel. Since the aluminum anodized film forms a fractal structure having current-carrying holes, deposition of deposits can be suppressed.

  Such an anodized film of aluminum is, for example, first coated with aluminum by a method such as spraying or vapor deposition on the surface against deposit, and then anodized on the surface of the stainless steel by anodizing the aluminum. A film can be formed.

  Further, the third embodiment of the present invention is a fuel injection valve having a nickel-chromium-molybdenum alloy layer on a deposit-preventing surface around a fuel injection hole formed of stainless steel. For example, a nickel-chromium-molybdenum alloy layer can be formed on the surface against deposits by alloying a mixed powder of a nickel-chromium self-fluxing alloy and molybdenum on a stainless steel surface using a carbon dioxide laser. Since the surface of the alloy layer obtained in this way forms a fractal structure, deposit accumulation can be suppressed.

  Furthermore, the fourth embodiment of the present invention is a fuel injection valve having a fluororesin coating on a deposit-preventing surface around a fuel injection hole formed of stainless steel. As shown in FIG. 4A, such a fluororesin coating can be obtained by forming a thin fluororesin coating 14 along the fractal structure on the surface 12f of the stainless steel 12 on which the fractal structure is formed. Further, as shown in FIG. 4B, a relatively thick fluororesin coating 14 may be formed on the surface of the stainless steel 12, and the surface of the fluororesin coating 14 may be fractalized. The fluororesin coating 14 exhibits good water / oil repellency even with only the coating, but super water / oil repellency can be obtained by using a fractal structure on the surface. Moreover, the surface can also be made into a fractal structure using plating.

  FIG. 5 is an example of a graph showing a change in the fuel flow rate per unit time depending on the tip temperature of the fuel injection valve (injector). A solid line (A) represents a change in the flow rate of the conventional fuel injection valve having a fluorine coating on the deposit countermeasure surface, and a broken line (A) represents a change in the flow rate of the fuel injection valve of the present invention. In the prior art (a), although the fluororesin film is applied, the oil repellency at high temperature is lowered. Therefore, when the tip temperature of the injector exceeds 160 ° C., deposits are deposited and the fuel flow rate is drastically lowered. However, in the fuel injection valve of the present invention having a fractal structure on the deposit countermeasure surface, the fractal structure exhibits super oil repellency, so that deposit accumulation can be suppressed, and even if the injector tip temperature exceeds 250 ° C. It is possible to maintain the flow rate stably. Therefore, it is possible to always maintain good controllability of the fuel injection amount.

  In the fuel injection valve according to the present invention, the inner peripheral surface of the fuel injection hole for injecting the fuel and the peripheral surface of the fuel injection hole (the deposit-preventing surface) are formed in a fractal structure. It is less likely to remain in the periphery, and deposit accumulation can be suppressed. Therefore, the fuel injection valve of the present invention is suitable as a fuel injection valve disposed in the upper center of the combustion chamber, particularly in an in-cylinder injection engine in which the periphery of the fuel injection hole becomes high.

It is principal part sectional drawing which shows an example of a structure of a fuel injection valve. (A) has a fuel injection hole in the nozzle body front-end | tip, (b) has a fuel injection hole in a nozzle plate, and is explanatory drawing of the front-end | tip part. It is explanatory drawing explaining a fractal structure. It is explanatory drawing explaining the contact angle of the liquid in the fractal surface. It is a cross-sectional schematic diagram of the fluororesin film formed on the stainless steel surface. (A) is a stainless steel surface having a fractal structure with a fluororesin coating formed thereon, and (b) is a surface of the fluorine history coating having a fractal structure. It is a graph which shows the change of the fuel flow volume by the front-end | tip temperature of a fuel injection valve.

Explanation of symbols

1: Fuel injection valve 2: Nozzle body 3: Needle valve 6: Nozzle hole 7: Fuel injection hole 8: Nozzle plate 12: Stainless steel (base material) 14: Fluororesin coating A: Deposit countermeasure part F: Fractal structure surface G: Gas L: Liquid S: Solid

Claims (5)

A nozzle body having a hollow shape and having an inner peripheral cylindrical surface defining a fuel flow path, an inner peripheral conical surface defining a nozzle hole, and a valve seat formed on the inner peripheral conical surface; A main body having an outer peripheral cylindrical surface opposed to the inner peripheral cylindrical surface, and a tapered portion having an outer peripheral conical surface facing the inner peripheral conical surface; A needle valve having a valve portion that can be seated on the valve seat, a valve lift mechanism that moves the needle valve in an axial direction thereof, and a fuel injection hole that communicates with the nozzle hole at a tip portion of the nozzle body. In the fuel injection valve provided,
A fuel injection valve characterized in that at least an inner peripheral surface of the fuel injection hole and a surface around the opening of the fuel injection hole are formed in a fractal structure.   The fuel injection valve according to claim 1, wherein at least a tip portion of the nozzle body is stainless steel.   3. The fuel injection valve according to claim 2, wherein an anodic oxide coating of aluminum is provided on an inner peripheral surface of the fuel injection hole and a surface around an opening of the fuel injection hole.   3. The fuel injection valve according to claim 2, wherein a nickel-chromium-molybdenum alloy layer is provided on an inner peripheral surface of the fuel injection hole and a surface around an opening of the fuel injection hole.   3. The fuel injection valve according to claim 2, wherein a fluororesin coating is provided on an inner peripheral surface of the fuel injection hole and on a surface around the opening of the fuel injection hole.

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