JP2006214301A - Fuel pump for cylinder direct fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel pump for a cylinder direct fuel injection device, having an excellent life at a high temperature as much as 100°C or more by using aluminum alloy in a cylinder direct fuel injection device for an automobile taking alcohol-contained gasoline as fuel. <P>SOLUTION: This fuel pump for the cylinder direct fuel injection device taking alcohol-contained gasoline as fuel is formed of aluminum or aluminum alloy, a plated layer is formed and coated on the surface of the body of the fuel pump, and the upside of the plated layer of the body of the fuel pump is treated with hydrated oxide film of aluminum (subjected to boehmite treatment), thereby restraining the occurrence of corrosion from a plating defective part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel pump used in an in-cylinder direct fuel injection system for automobiles using alcohol-containing gasoline as a fuel, and more particularly, direct in-cylinder fuel injection capable of obtaining a long life by slowing the progress of corrosion of an aluminum alloy. The present invention relates to a fuel pump for an apparatus.

In recent years, alcohol-containing gasoline has been used as a fuel for automobiles due to exhaust gas regulations (NO _X , CO _2, etc.). In addition, an in-cylinder direct fuel injection device is used for an automobile gasoline engine as an injection device for the purpose of improving fuel consumption characteristics, reducing harmful exhaust gas, and improving driving responsiveness such as acceleration. And from the viewpoint of energy saving by reducing the weight of the automobile, a product that is made lighter by applying an aluminum-based material is desired as the material of the fuel pump member of the in-cylinder direct fuel injection device.

  The fuel pump of the in-cylinder direct fuel injection device has a high temperature reaching 100 ° C. or higher and a high pressure reaching 7 to 12 MPa. Therefore, if an aluminum-based material is used as the material of the fuel pump member of the direct fuel injection device in the cylinder, the alcohol contained in the gasoline may cause corrosion, cavitation, Wear due to erosion occurs. Therefore, even if an aluminum material is used for the fuel pump of the direct fuel injection device in the cylinder, the generation of corrosion, cavitation, and further wear due to erosion can be suppressed, and their resistance to the environment is improved. A fuel pump has been proposed (see, for example, Patent Document 1).

This patent document 1 discloses that a non-electrolytic Ni-P or Ni-P system is used for a fuel pump for an in-cylinder direct fuel injection device having aluminum or an aluminum alloy in order to suppress the occurrence of corrosion, cavitation, and erosion. The plating film is formed.
JP 2004-36555 A

When an aluminum alloy is used as the material of the body of a fuel pump for an in-cylinder direct fuel injection device, the aluminum that is the material of this fuel pump usually forms a protective oxide film Al ₂ O ₃ on the outermost surface. Therefore, it exists stably in a dry room temperature air environment. However, when alcohol, moisture, acid components, etc. are mixed in gasoline, there is a possibility that corrosion of the material is accelerated. When alcohol-containing gasoline is used as a fuel for automobiles, aluminum corrodes due to the presence of alcohol.

For example, taking ethanol as an example, aluminum and ethanol are
2Al + 6C ₂ H ₅ OH → Al (OC ₂ H ₅ ) ₃ + 3H ₂
To react. This produces Al (OC ₂ H ₅ ) ₃ , which is unstable and immediately Al (OC ₂ H ₅ ) ₃ + 6H ₂ → 2Al (OH) ₃ + 6C ₂ H ₆
2Al (OH) ₃ → Al ₂ O ₃ .H ₂ O + 2H ₂ O
It will be decomposed by the reaction.

That is, the barrier layer of the protective thin oxide film Al ₂ O ₃ formed on the outermost surface by this reaction is immediately damaged by ethanol at a high temperature. Due to the damage of the barrier layer, corrosion proceeds as an aluminum base material without the barrier layer, resulting in wear. In addition, the reaction rate of this reaction increases as the temperature increases. Specifically, in a fuel passage system component that is exposed to a temperature range of 100 ° C. or higher, the corrosion reaction due to alcohol is accelerated at a stroke.

  Therefore, each part made of aluminum in the fuel flow path parts for fuel supply is composed of fuel containing various alcohols, fuel mixed with water, fuel mixed with oxidizing components, or deteriorated fuel. Durability is required in an environment that comes into contact with the inside.

  In Patent Document 1, a fuel pump for an in-cylinder direct fuel injection device having aluminum or an aluminum alloy is formed by forming a Ni-P or Ni-P-based plating film by electroless electrolysis. Plating may not be formed on a fine defect portion such as an ingot portion of an alloy. In addition, even when a material other than a cast material such as die casting is used, the aluminum alloy of the base material may appear on the surface due to the removal of burrs, burrs, etc. after the plating process, resulting in plating defects. .

  For this reason, in Patent Document 1, an aluminum alloy as a base material appears on the surface of a fine defect part such as a cast hole part of an aluminum die cast alloy or a plating defect part from which burrs, burrs, etc. are dropped after plating, There is a problem that corrosion occurs from that portion and the life is shortened in a short time.

  An object of the present invention is to provide a fuel pump for an in-cylinder direct injection device that uses an aluminum alloy and has an excellent life even at a high temperature of 100 ° C. or higher.

  The fuel pump for in-cylinder direct fuel injection device according to the present invention is a fuel pump for in-cylinder direct fuel injection device that uses alcohol-containing gasoline as fuel. The fuel pump is made of aluminum or aluminum alloy, and the surface of the body of the fuel pump In addition to forming a coating layer on the surface of the fuel pump and performing a hydrated oxide film treatment (boehmite treatment) of aluminum on the plating layer of the body of the fuel pump, the occurrence of corrosion from the plating defect portion is suppressed.

  In the fuel pump for an in-cylinder direct fuel injection device according to the present invention, the plating layer is formed by electroless plating.

  Furthermore, the fuel pump for an in-cylinder direct fuel injection device according to the present invention is such that the hydrated oxide film treatment of aluminum is continuously performed in the same line as the electroless plating treatment.

  By constructing in this way, even under high temperatures of over 100 ° C due to electroless plating, the aluminum alloy suppresses corrosion due to alcohol, etc. contained in gasoline, and the hydrated oxide film treatment prevents defects in plating. Even when the base aluminum alloy appears on the surface, the corrosion rate of the base aluminum alloy is slowed down, a long life can be obtained, and a highly reliable fuel pump is realized. can do.

  The results of examining the alcohol corrosion resistance of the aluminum alloy subjected to the hydrated oxide film treatment are shown in FIGS.

  FIG. 1 shows the corrosion rate of the aluminum die-cast alloy ADC12 subjected to the hydrated oxide film treatment in gasoline containing 13.5% by volume of ethanol.

  In FIG. 1, the corrosion rate test of the aluminum die-cast alloy ADC12 is performed by putting gasoline containing ethanol in a sealed pressure vessel, and a test piece of 15 mm × 15 mm × 3 mm in the sealed pressure vessel containing the ethanol-containing gasoline (Lumi Die Cast Alloy ADC12). Was carried out. The temperature of the ethanol-containing gasoline contained in the sealed pressure vessel was 120 ° C., and the immersion time was 24 hours. As a result, when the hydrated oxide film is treated for 10 minutes in tap water, the effect of improving the corrosion resistance is small in tap water, but by treating the hydrated oxide film for 10 minutes in pure water, compared to the untreated product. The corrosion rate was reduced to about 1/5, and it was found that pure water is very effective.

  FIG. 2 shows the corrosion rate of the aluminum die-cast alloy ADC12 that has been pretreated for 1 minute by ultrasonic immersion in a 0.5 wt% NaOH aqueous solution and then subjected to a hydrated oxide film treatment. The immersion test conditions in the test for the alcohol corrosion resistance of the aluminum alloy subjected to the hydrated oxide film treatment in FIG. 2 are the same as the immersion test conditions in FIG. As a result, it was found that the corrosion rate decreased by performing NaOH ultrasonic immersion (pretreatment), and the corrosion hardly progressed by NaOH ultrasonic immersion + hydrated oxide film treatment for 10 minutes.

  FIG. 3 (a) shows a general electroless Ni—P plating process, and FIG. 3 (b) shows an implemented Ni—P electroless plating process.

  In the general process of FIG. 3 (a), after the electroless Ni—P plating process is completed, the hot water washing process is performed after the rough water washing, but in the process performed in FIG. 3 (b), the electroless Ni—P plating process is performed. After the completion, the hydrated oxide film treatment is performed after washing with rough water. This general hot water washing process is performed with tap water of about 60 ° C., and the hydrated oxide film treatment used was pure water of 90 ° C. to 95 ° C.

  In a general hot water washing process performed with tap water at about 60 ° C., the effect of improving the corrosion resistance by the hydrated oxide film treatment is small, but the hydrated oxide film treatment is performed using pure water at 90 ° C. to 95 ° C. When done, it is very effective. Further, the use of pure water has an effect of preventing the occurrence of spots as compared with hot water washing with tap water.

  Also, by performing the hydrated oxide film treatment immediately after the plating process, the body to be treated is in a clean state by alkaline degreasing and pickling which are the pretreatment processes of plating, so the hydrated oxide film The process works more effectively.

Therefore, it is effective for the corrosion resistance in the alcohol-containing fuel that the hydrated oxide film treatment is continuously performed in the same line as the plating treatment step.

  This example is an example in which electroless Ni-P plating is applied to a radial plunger fuel pump.

  First, the Ni-P plating process of a radial fuel pump and the manufacturing method of a radial plunger fuel pump are demonstrated.

  FIG. 4 shows a cross-sectional shape of a pump body body made of an aluminum alloy.

  The pump body main body is provided with a fuel intake passage, a fuel discharge passage, a fuel flow passage hole, an engine main body fixing bolt hole, and the like. In order to be a fuel pump, a suction damper, a solenoid for controlling the discharge amount, and a pump mechanism (cylinder, plunger) are incorporated in the pump body main body.

  First, this pump body is manufactured. In addition, it is inferior in productivity to manufacture all of these shape processing by machining. As a manufacturing method excellent in productivity of the general shape (body material) of the pump body, there is aluminum die casting. This aluminum die casting is a casting system in which a molten alloy (aluminum alloy) is injected under pressure at a high pressure, and is excellent in mass productivity. Moreover, the manufacturing process by aluminum die casting is made of aluminum alloy ingot → melting → casting → body material → machining finishing → pump body.

  Further, the schematic shape of the pump body main body can be formed by forging. This forging is a method of forming a round bar material by a high surface pressure press, and is a manufacturing method excellent in productivity as inferior to die casting.

  In the case of die casting, plating may not be formed on fine defect portions such as a cast hole portion of an aluminum die casting alloy. However, in the case of forging, there is no fine defect portion such as a die-casting portion such as die casting, but burrs, burrs and the like may fall off together with plating described later, and the base aluminum alloy may appear on the surface. In this case, the same applies to die casting.

  In such a case, plating defects may occur, and the base aluminum alloy may appear on the surface, leading to corrosion. By performing aluminum hydrated oxide film treatment as a backup for electroless plating, the pump as a whole Long life can be achieved.

  Next, an electroless plating film is formed on the pump body body manufactured by aluminum die casting.

  The electroless plating used in this example is an electroless Ni-P plating, but it is particularly a kind if it is a plating that does not use electric energy, such as electroless Ni-B plating, electroless copper plating, electroless silver plating, etc. Don't stick to it. In this way, the type of plating does not matter, the fuel flow path has complicated and narrow parts, and it is essential that a film be formed at any of these parts, and the thickness of the plating film This is because it is necessary to form the thickness as uniform as possible. In addition, the plating method using electric energy cannot form a plating film in a complicated and narrow part of the fuel flow path due to non-uniform electrolysis distribution due to the shape effect, or it becomes non-uniform even if it can be formed. This is because it is not desirable.

  The Ni-P plating may contain a material that can be alloyed or dispersed with the plating film, such as Co or W as a metal element, SiC, BN, PTFE as an inorganic compound, or B as an inorganic substance.

  Here, in the electroless Ni—P plating, when the hypophosphite anion in the plating solution comes into contact with the eighth group metal in the periodic table under the condition, the metal serves as a catalyst to cause dehydrogenation decomposition. The generated hydrogen atoms are adsorbed on the catalytic metal surface and activated as a condensed layer, which contacts nickel cation in the plating solution to reduce nickel to metal and deposit on the catalytic metal surface (base material). .

  In addition, activated hydrogen atoms on the surface of the catalytic metal react with hypophosphorous acid anions in the liquid, reducing the phosphorus contained therein and alloying with nickel. The deposited nickel is used as a catalyst to continue the above-described nickel reduction plating reaction. That is, there is a feature that the plating proceeds continuously by the autocatalytic action of nickel. Thereby, if there is a gap through which the plating solution flows, a plating film is uniformly formed. Further, the thickness of the plating film is proportional to the plating time and is managed by controlling the time.

  In the formation process of the Ni-P or Ni-P plating film, it is essential that the plating film is uniformly formed on the entire surface of the body body of the fuel pump. Therefore, in the plating process, it is important that the entire surface of the body body of the fuel pump is in contact with the plating solution and that the plating solution circulates without stagnation.

  Circulating the plating solution on the entire body surface of the fuel pump without stagnation is essential for the continuous precipitation of Ni—P by autocatalysis. When the stagnation occurs, precipitation due to autocatalysis within a limited amount of plating solution ends, and subsequent deposition stops, and the increase in the thickness of the plating film stops. Therefore, the film thickness is nonuniform. In order to prevent such a situation, as a method of circulating the plating solution on the entire surface of the fuel pump body without stagnation, the plating in the plating solution of the body of the fuel pump, for example, up and down, left and right, rotational movement, and plating Fluidize the liquid.

  As described above, contact with the plating solution on the entire surface of the body of the fuel pump and retention of the plating solution can be prevented, and an excellent plating film with little uniformity and defects can be formed on the entire surface of the body of the fuel pump.

  In this example, an aluminum die-cast alloy ADC12 was used, and a 15 μm electroless Ni—P plating film was formed on the entire surface of the body body 100 of the fuel pump. Further, the P concentration of the Ni—P plating solution was about 11 wt%.

  Next, the radial plunger fuel pump of the present embodiment produced by the above manufacturing method will be described with reference to FIG. 5 (sectional view).

  The Ni—P plating is uniformly applied to the pump body main body 100 made of an aluminum material by the above-described processing. In this embodiment, an aluminum material is used as a part that comes into contact with the fuel of the fuel pump. In the pump body 100, the pressurizing chamber 112, the fuel suction passage 110, the fuel discharge passage 111, etc., methyl alcohol, ethyl alcohol, etc. It is assumed to be used in contact with gasoline containing alcohol, various gasoline additives, or deteriorated gasoline (of course, the use of gasoline-only fuel is not denied).

  A fuel suction passage 110, a suction hole 105a, a pump chamber 112a, a discharge hole 106a, and a fuel discharge passage 111 are formed in the body body 100 of the fuel pump as fuel flow paths. The intake valve 105 is provided between the fuel intake passage 110 and the intake hole 105a, and the discharge valve 106 is provided between the fuel discharge passage 111 and the discharge hole 106a. Here, both the intake valve 105 and the discharge valve 106 are check valves that limit the flow direction of fuel. The pressurizing chamber 112 includes a pump chamber 112a, a suction hole 105a, and a discharge hole 106a. That is, the pressurizing chamber 112 is formed as a region surrounded by the body body 100 of the fuel pump, the plunger 102, the suction valve 105, and the discharge valve 106. The plunger 102 is in pressure contact with the drive cam 200 via the lifter 103, and is configured to convert the swinging motion of the drive cam 200 into a reciprocating motion so that the volume of the pressurizing chamber 112 changes.

  On the other hand, the body main body 100 of the fuel pump and the suction valve holder 105b, the body main body 100 of the fuel pump and the discharge valve holder 106b are in pressure contact, and the cylinder 108 and the body main body 100 of the fuel pump are also in pressure contact via the protector 120. Yes.

  Here, the operation of the radial plunger fuel pump of this embodiment will be briefly described.

  Fuel gasoline is supplied via the suction valve 105 and introduced into the pressurizing chamber 112. Here, the suction valve 105 depends on the operation of the solenoid 300. When the solenoid 300 is in the OFF (non-energized) state, a biasing force is applied in the direction to open the suction valve 105, and when the solenoid 300 is in the ON (energized) state. Is a free valve that opens and closes the intake valve 105 in synchronization with the reciprocating motion of the plunger 102. When the suction valve 105 is closed during the compression process of the plunger 102, the internal pressure of the pressurizing chamber 112 rises, the discharge valve 106 is automatically opened, and the fuel is pumped to the fuel discharge passage.

  In addition, the actual machine durability test of the fuel pump according to the present embodiment was performed. As fuel, gasoline with 22% ethanol added was used, and the test was performed at a rotational speed of 3500 r / min and a discharge pressure of 12 MPa.

  As a result, the fuel pump operated without any abnormality, and a stable value of gasoline discharge flow rate was obtained. Moreover, after the test, it was disassembled and the result of inspection of each part in the fuel chamber showed that no corrosion or wear due to corrosion was observed in any part, and it was in a steady state.

  On the other hand, the pump body was scratched to the extent that the Ni-P plating layer was damaged, and tested under the same conditions as the durability test. At this time, scratches were added before and after the hydrated oxide film treatment. As a result, corrosion occurred only in the scratches added after the hydrated oxide film treatment. That is, if the Ni—P plating is complete, excellent durability is exhibited, but the base aluminum alloy appears on the surface in the plating defect portion, and the base material is corroded in that portion. Therefore, even if a plating defect occurs, it has become clear that corrosion can be prevented by the hydrated oxide film treatment.

  As described above, in this embodiment, the aluminum die-cast alloy ADC12 is used as the body material of the fuel pump, and the electroless Ni-P plating film is formed in the fuel flow path. Therefore, a sufficient life can be obtained even in an environment where alcohol-containing fuel is used. Could be satisfied.

  As mentioned above, according to the present Example, since the electroless Ni-P plating film was formed in the fuel flow path of the fuel pump and the hydrated oxide film treatment was performed, the occurrence of corrosion could be suppressed.

  In addition, since the hydrated oxide film treatment (the damaged part after the hydrated oxide film treatment) is corroded, the use of the hydrated oxide film treatment is important for the life of the fuel pump. It can be said that it is effective for improvement.

  Anticorrosion technology can be used as aluminum or aluminum alloy exposed to corrosive environment. In particular, the present invention can be applied to parts having difficulty in anodizing and electroplating, such as parts having an inner diameter portion of piping parts and minute diameter holes.

It is a figure which shows the corrosion rate test result (effect of a process solution and process temperature) of the aluminum die-casting alloy ADC12 which performed the hydrated oxide film process. It is a figure which shows the corrosion rate test result (the presence or absence of pre-processing, the influence of processing time) of the aluminum die-casting alloy ADC12 which performed the hydrated oxide film process. It is a figure which shows the process of electroless Ni-P plating. It is sectional drawing of the body main body of the fuel pump in the Example of this invention. It is a partial cross section figure of the fuel pump in the Example of this invention.

Explanation of symbols

100 ……………… Pump body body 102 ……………… Plunger 103 ……………… Lifter 105 ……………… Suction valve 105a …………… Suction hole 105b …………… Suction Valve holder 106 ……………… Discharge valve 106a …………… Discharge hole 106b …………… Discharge valve holder 108 ……………… Cylinder 110 ……………… Fuel intake passage 111 ……… ……… Fuel discharge passage 112 ……………… Pressure chamber 112a ……………… Pump chamber 120 ……………… Protector 200 ……………… Drive cam 300 ……………… Solenoid

Claims (3)

In a fuel pump for in-cylinder direct fuel injection systems using alcohol-containing gasoline as fuel,
The fuel pump is formed of aluminum or an aluminum alloy, a coating layer is formed on the surface of the fuel pump body, and a hydrated oxide film treatment of aluminum is performed on the plating layer of the fuel pump body. A fuel pump for an in-cylinder direct fuel injection device characterized by being formed.   The plating layer according to claim 1 is a fuel pump for an in-cylinder direct fuel injection device formed by electroless plating.   The fuel pump for an in-cylinder direct fuel injection device according to claim 2, wherein the aluminum hydrated oxide film treatment is continuously performed in the same line as the plating treatment.

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