JPH0658218A - Highly corrosion-resistant fuel injection device - Google Patents

Abstract

PURPOSE:To provide excellent corrosion-resistance for strongly corrosive fuel such as gasoline-alcohol mixture fuel by forming at least one of a valve and an injection port seat of a nozzle body of a specified martensite stainless steel. CONSTITUTION:A nozzle body 5 is provided with a fuel injection port 5b. A valve 4 is slid inside a guide hole formed inside the nozzle body 5. The fuel injection port 5b is opened or closed by moving the valve 4 in an axial direction. At least one of the valve 4 and an injection port seat 5a of the nozzle body 5 on which the valve 4 seats is made of martensite stainless steel for cold forging including C of 0.1 to 0.5wt.%, Cr of 12 to 18wt.%, Mo of 0.5 to 1.5wt.%, Si of 0.03 to 1.0wt.%, Mn of 0.03 to 0.75wt.%, and reminder of Fe or inevitable impurity. Durability of the seat 5a and the valve 4 to corrosion and damage can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an automobile engine or the like, and more particularly to a fuel injection device excellent in corrosion resistance to a highly corrosive fuel such as gasoline-alcohol mixed fuel and a nozzle body used therefor. And regarding valves.

[0002]

2. Description of the Related Art Conventionally, gasoline has been mainly used as a fuel in Otto type engines for automobiles. The main components of this gasoline are on-chain hydrocarbons such as aromas, olefins and paraffins, and aromatic hydrocarbons, which contain some impurities such as sulfur. On the other hand, the material of the valve of the fuel injection device or the injection hole seat portion (hereinafter simply referred to as the seat portion) of the nozzle body on which the valve is seated is SUS440C, S specified by Japanese Industrial Standards (JIS).
Martensitic stainless steels such as US420J2 have been used. A fuel injection valve for a diesel engine, in which a fuel injection control needle is made of martensitic stainless steel (SUS440A to E), is a fuel injection valve for a diesel engine.
No. 759 is disclosed.

[0003]

Since the problem of the deterioration of the global environment due to the progress of air pollution has become more serious year by year, the exhaust gas regulations for automobiles are shifting to the stricter regulation than before. For example, in the United States of America, the amount of hydrocarbons in exhaust gas has averaged from 0.25 g / mile to 0.062 g / mi in 10 years from 1994.
In 1990, the world's strictest exhaust gas regulations, which obliged car manufacturers to reduce to le, were decided, and each country is expected to follow this trend. In order to satisfy these strict regulations in the future, major technological innovations such as atomization of injected fuel, strengthening of catalyst, and adoption of gasoline-alcohol mixed fuel (hereinafter simply referred to as alcohol fuel) are essential. Has become. Of these, alcohol fuel is not only hydrocarbon but also NOx, SOx, C
Since it can reduce O, it is attracting attention as a low-pollution clean fuel for the next generation.

However, when such an alcohol fuel, particularly methanol as alcohol, is used, significant corrosion damage, which could not occur in the past, occurred in the seat portion of the nozzle body. This seat is where the valve sits, and its corrosive damage causes fuel leakage, combustion,
It causes problems such as deterioration of fuel efficiency that hinders normal operation of the engine. The inventors conducted various studies on the cause of this corrosion damage and concluded the mechanism thereof as follows.
That is, near the discharge hole of the fuel injection device, blowback gas leaking from the gap of the intake valve of the engine cylinder, blowby gas, and EGR gas depending on the engine are present, and Cl ~, NO ₃ ~, SO ₄ ²
~, HCOO ~, etc. are included. An acid is generated by the dissolution of these ions in the alcohol fuel near the seat portion. On the other hand, in the seat portion, the fine chromium oxide film having corrosion resistance is broken by the striking wear of the valve during operation, and the new surface is exposed and the corrosion resistance is lowered. Therefore, it is considered that the sheet portion is attacked and corroded by the acid.

In order to solve such problems and provide a highly reliable fuel injection device, the material of the seat portion must be changed to a material having higher corrosion resistance than the conventional one. However, since the hardness of the surface of the sheet portion must be about HRC52 to 60, hardness cannot be secured with austenitic and ferritic stainless steels, which have higher corrosion resistance than conventional martensitic stainless steels, and the application is not possible. is there. Precipitation hardening type stainless steel such as SUS630 also has high corrosion resistance, but its hardness is limited to about HRC40, and this level of hardness causes severe wear, and therefore cannot be applied. Further, although ceramics can secure corrosion resistance and hardness, they are weak against impacts, leaving a concern as a sheet member. The surface treatment on the seat portion is good if the precision of the parts can be secured, but if not so, it is difficult to adopt it to the fuel injection device which requires precision. In addition, there is a risk that the surface treatment layer will be worn and completely lost. The above problems also apply to the valve seated on the seat.

An object of the present invention is to develop a new martensitic stainless steel having excellent corrosion resistance in order to improve the corrosion resistance of the seat and the valve, thereby improving the durability of the seat and the valve against corrosion damage. An object is to provide an excellent and highly reliable fuel injection device.

[0007]

To achieve the above object, the present invention comprises a nozzle body having a fuel injection hole and a valve that slides in a guide hole formed in the nozzle body. Is a fuel injection device that opens and closes the fuel injection hole by moving in the axial direction of the nozzle body, wherein at least one of the valve and at least the injection hole seat portion of the nozzle body on which the valve is seated has a weight ratio. C; 0.1
.About.0.5%, Cr; 12 to 18%, Mo; 0.5 to 1.
5%, Si; 0.03 to 1.0%, Mn; 0.03 to
The high corrosion resistant fuel injection device is characterized in that it is 0.75%, and the balance is martensitic stainless steel for cold forging, which comprises Fe and unavoidable impurities. Here, in terms of weight ratio, Cu: 0.03 to 0.6%, Ni: 0.03 to
0.6%, V: 0.03 to 0.5% is preferable. Of the unavoidable impurities, P: 0.03% or less,
S: 0.01% or less is preferable. Also, the fuel is particularly good for those that are gasoline-alcohol mixed fuels.

The present invention further includes a valve that slides in a guide hole formed in a nozzle body having a fuel injection hole, and the valve moves in the axial direction of the nozzle body to open and close the fuel injection hole. In the nozzle body of the fuel injection device, at least the injection hole seat portion of the nozzle body on which the valve is seated has a weight ratio of C: 0.1 to 0.5%, C
r; 12-18%, Mo; 0.5-1.5%, Si;
0.03 to 1.0%, Mn; 0.03 to 0.75%, and the rest is a martensitic stainless steel for cold forging composed of Fe and unavoidable impurities, which is a nozzle body. . Here, Cu; 0.0 in terms of weight ratio
3 to 0.6%, Ni; 0.03 to 0.6%, V; 0.0
What further contains 3 to 0.5% is preferable. Among the unavoidable impurities, P: 0.03% or less and S: 0.01% or less are preferable.

The present invention further includes a valve that slides in a guide hole formed in a nozzle body having a fuel injection hole, and the valve moves in the axial direction of the nozzle body to open or close the fuel injection hole. Of a fuel injection device, wherein the valve is C: 0.1 to 0.5% by weight, Cr: 12 to
18%, Mo; 0.5 to 1.5%, Si; 0.03 to
1.0%, Mn; 0.03 to 0.75%, and the rest is a martensitic stainless steel for cold forging composed of Fe and unavoidable impurities. Here, in terms of weight ratio, Cu; 0.03 to 0.6%, Ni;
It is preferable that the composition further contains 0.03 to 0.6% and V; 0.03 to 0.5%. Of the inevitable impurities, P: 0.0
3% or less, S; 0.01% or less is preferable.

[0010]

[Operation] By using the above-mentioned martensitic stainless steel for cold forging as a material for the seat portion and the valve,
Since the seat portion and the valve are excellent in durability against corrosion damage even when alcohol fuel is used, fuel leakage and combustion, deterioration of fuel consumption, etc. that hinder normal operation of the engine do not occur. Therefore, a highly reliable fuel injection device can be provided.

Next, the reasons for limiting the components of the martensitic stainless steel for cold forging used in the fuel injection device of the present invention will be described. C is a solid solution strengthening element, and it is necessary to add at least 0.1% or more in order to secure hardness as a martensite structure by heat treatment. However, if it exceeds 0.5, not only the corrosion resistance of the matrix is impaired because the amount of chromium carbide formed increases, but
Cold forgeability also deteriorates. Therefore, the upper limit is set to 0.5%.

Cr is a basic component of stainless steel, and it is necessary to add at least 12% or more in order to secure corrosion resistance. However, if it exceeds 18%, an austenite structure is formed and the hardness decreases, so the source was set to%.

Mo is an element that improves the corrosion resistance to chloride solutions and sulfuric acid, and it is necessary to add at least 0.5% or more to obtain the effect. However, 1.5%
If it exceeds the value, the hardness is lowered and the cold forgeability is deteriorated.
The upper limit was 1.5%.

When Si is added in an amount of 0.03% or more, it has the effect of refining the carbides and preventing the formation of reticulated carbides that cause a decrease in strength. However, if it exceeds 1.0%, the cold forgeability is impaired, so the upper limit was made 1.0%.

Mn is an accompanying element, and has the effect of improving mechanical cutting property by forming MnS by combining with S in addition to increasing strength and toughness, but if it exceeds 0.75%, cold forgeability, Since the corrosion resistance is impaired, the content was made 0.03 to 0.75%.

When Cu, Ni and V are added together with Cr and Mo, the corrosion resistance is further improved. To obtain that effect, it is necessary to add 0.03% or more of each, but C
If u and Ni are added in an amount of more than 0.6% and V is more than 0.5%, the improvement effect becomes small, and conversely the cold forgeability is impaired. .About.0.6% and V was 0.03 to 0.5%. If P and S are more than 0.03% and 0.01%, respectively, the corrosion resistance is deteriorated, so it is necessary to suppress the concentration to less than this.

[0017]

EXAMPLES The present invention will be described below based on examples. FIG. 2 is a sectional view of a vehicle fuel injection device to which the present invention is applied. A spring 3 is incorporated between the adjuster 1 and the plunger rod 2. Normally, the contact surface 4a of the ball valve 4 joined to the tip of the plunger rod 2 by this spring force has its contact surface 4a on the seat surface 5a of the nozzle body 5.
Since it is pressed against the fuel injection hole 5b to close the fuel injection hole 5b, the fuel pressurized and supplied from the fuel supply hole 8a is
Is not jetted from. However, when a current flows through the coil 6, a magnetic force against the spring force is generated inside the coil, and the plunger rod 2 is attracted toward the adjuster 1, so that the ball valve 4 separates from the seat surface 5a of the nozzle body 5. Fuel is injected. Such a separation-seating operation of the valve 4 is ½ of the engine speed, that is, 100 rpm if the engine speed is 2000 rpm.
This operation is performed 0 times.

By the way, as a material for the seat surface 5a of the ball valve 4 and the nozzle body 5, from the viewpoint of prevention of beating wear due to the above operation and corrosion due to alteration of fuel, conventionally, martens such as SUS440C and SUS420J2 are used. Site-based stainless steel has been used. This martensitic stainless steel has a hardness of HRC52-6.
Since about 0 can be secured and it has a certain degree of corrosion resistance, there was no possibility that the seat portion would be corroded and damaged when gasoline was used as a fuel.

However, even with such a martensitic stainless steel having a certain degree of corrosion resistance, when the fuel is changed from gasoline to alcohol fuel which is a low-pollution clean fuel, the sheet portion is significantly corroded and damaged. It has become clear that a phenomenon that has never existed before occurs. Such corrosion damage is a factor that impedes normal operation of the engine, such as fuel leakage when the valve is seated, combustion accompanying this, and deterioration of fuel consumption, and must be avoided.

The inventors conducted various experiments in order to investigate the cause of the above-mentioned corrosion damage. First, as alcohol fuel, methanol 85 vol%, gasoline 15 vol%
M85 of composition is used, and blow-by gas, EGR
Add 100ppm each of hydrochloric acid, nitric acid and sulfuric acid detected in exhaust gas such as gas, and add SUS440C,
SUS420J2 was immersed at room temperature for 48 hours to perform a corrosion test. The test piece used had its surface polished immediately before the corrosion test. As a result, as shown in FIG. 3, it was revealed that the corrosiveness of M85 was much stronger than that of gasoline. Therefore, when the exhaust gas containing hydrochloric acid, nitric acid, and sulfuric acid dissolves in the fuel near the injection hole, M
It is considered that in the case of 85, since the corrosiveness is stronger than that of gasoline, the seat portion is corroded and damaged.

The reason why only the seat portion is corroded and not corroded except the seat portion is that the contact surface 4a and the seat surface 5a in the seat portion are struck by the seating-separating operation of the ball valve 4. It is thought that this is because the dense chromium oxide film covering the surface of the film was broken and the corrosion resistance of that part was reduced. In order to confirm this, SUS440C and SUS420J2 whose surfaces were not polished were immersed in M85 containing 100 ppm each of hydrochloric acid, nitric acid and sulfuric acid at room temperature for 48 hours immediately before the corrosion test, and the corrosion test was performed. The result is shown in FIG. 4 in comparison with the result of FIG. The test piece whose surface was not polished showed a smaller corrosion weight loss than the polished test piece, demonstrating the correctness of the above estimation.

In order to prevent the corrosive damage of the sheet portion in such a situation, the inventors have developed a martensitic stainless steel having a higher corrosion resistance as a sheet material and a hardness equal to or higher than that of conventional materials. First, we considered the material composition. Here, SUS440C, which is a 17Cr steel, has a high carbon concentration of about 1%, and thus a large amount of chromium carbide is formed. As a result, chromium is consumed by the chromium carbide, so the effective chromium concentration in the matrix portion is low, and corrosion resistance is high. Was considered to have decreased. Further, SUS420J2, which is 13Cr steel, has a low carbon concentration of about 0.3% and is unlikely to form chromium carbide, but it is considered that the corrosion resistance is lowered because the chromium concentration is low in the first place.

Therefore, considering plastic workability, it is considered that addition of Mo or the like is effective in the low C medium Cr steel, and a material as an example of the present invention was manufactured for each of them. Table 1 shows the compositions of the materials of Examples (Nos. 1 to 8) and the comparative material (the material disclosed in JP-A-59-211759) having a C content outside the range of the present invention.

[0024]

[Table 1]

The following heat treatments were performed on each trial material and comparative material. First, an ingot of a trial material was swaged into a rod shape having a diameter of 10 to 20 mm, which was annealed at 900 ° C. for 1 hour and 700 ° C. for 3 hours (this may be repeated if necessary).
As a result, the stress is removed, and the carbide is spheroidized to facilitate processing. Then, the nozzle body is cut into a length and plastically worked to form a fuel injection hole or a seat surface.
After heating at 0 to 1100 ° C. for 1 hour, N ₂ gas was blown to cool to room temperature and quenching was performed. Then, it was tempered at 160 ° C. and its hardness was examined. The results are shown in Table 2.

[0026]

[Table 2]

From these results, the hardness of any material is HRC5.
It was 2 or more, and it was revealed that there is no problem in application in terms of hardness. Next, hydrochloric acid, nitric acid, and sulfuric acid 10 each
Corrosion tests were conducted by immersing the respective trial materials and comparative materials in M85 added with 0 ppm at room temperature for 48 hours. The result of comparison with the conventional materials SUS440C and SUS420J2 is shown in FIG. From this result, the prototype material (No
1-8) The corrosion weight loss is 0.80~1.6 × 10 ~ ⁴ g /
cm ² , which was confirmed to have a remarkable effect as compared with the conventional material and the comparative material. Further, in the durability test of the fuel injection device in which the seat portion was made of the prototype material, no corrosion occurred and no fuel leakage occurred.

From the above results, when the present invention is applied, corrosion damage of the seat portion can be prevented, and a fuel injection device with high durability and reliability can be obtained. Although the valve has a ball shape in this embodiment, it does not have to have a ball shape and may have a needle shape, for example.

[0029]

According to the present invention, since the seat portion and the valve do not corrode even with a highly corrosive fuel such as gasoline-alcohol mixed fuel, fuel leakage from the seat portion occurs. do not do. Therefore, problems such as deterioration of combustion and deterioration of fuel efficiency that hinder normal operation of the engine do not occur.

[Brief description of drawings]

FIG. 1: M8 with 100 ppm each of hydrochloric acid, nitric acid, and sulfuric acid
It is the figure which showed the corrosion weight loss of each material after the corrosion test in 5.

FIG. 2 is a vertical sectional view of a fuel injection device showing an embodiment of the present invention.

FIG. 3: M8 added with 100 ppm each of hydrochloric acid, nitric acid, and sulfuric acid
It is the figure which showed the corrosion weight loss of each material after the corrosion test in 5.

FIG. 4 is a diagram showing the effect of a chromium oxide film on corrosion weight loss.

[Explanation of symbols]

 1 Adjuster 2 Plunger rod 3 Spring 4 Ball valve 4a Contact surface 5 Nozzle body 5a Seat surface 6 Coil 8 Yoke 9 O-ring 10 O-ring 11 Swirler 12 Ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Innovator Shin Onose 2520 Takaba, Katsuta-shi, Ibaraki Hitachi, Ltd. Automotive Equipment Division (72) Inventor Toshio Furuhashi 2520 Takata, Katsuta-shi, Ibaraki Hitachi, Ltd. (72) Yoshiyuki Tanabe, Inventor Yoshiyuki Tanabe 2520, Takaba, Katsuta-shi, Ibaraki Hitachi, Ltd., Automotive Equipment Division

Claims (10)

[Claims] 1. A nozzle body having a fuel injection hole, and a valve that slides in a guide hole formed in the nozzle body, wherein the valve is moved in the axial direction of the nozzle body to allow the fuel injection hole to move. A fuel injection device for opening and closing the valve, wherein at least one of the valve and at least the injection hole seat portion of the nozzle body on which the valve is seated is C; 0.1
.About.0.5%, Cr; 12 to 18%, Mo; 0.5 to 1.
5%, Si; 0.03 to 1.0%, Mn; 0.03 to
A high corrosion resistant fuel injection device, characterized in that it is 0.75% and the balance is martensitic stainless steel for cold forging consisting of Fe and unavoidable impurities. 2. The high corrosion resistant fuel injection device according to claim 1, wherein Cu: 0.03 to 0.6% by weight and N in weight ratio.
i: 0.03-0.6%, V: 0.03-0.5%, The high corrosion-resistant fuel injection device characterized by the above-mentioned. 3. The high corrosion resistant fuel injection device according to claim 1, wherein P: 0.03% or less and S: 0.01% or less among the unavoidable impurities. Injection device. 4. The highly corrosion resistant fuel injection device according to any one of claims 1 to 3, wherein the fuel is a gasoline-alcohol mixed fuel. 5. A fuel injection device comprising a valve that slides in a guide hole formed in a nozzle body having a fuel injection hole, and the valve moves in the axial direction of the nozzle body to open and close the fuel injection hole. At least the injection hole seat portion of the nozzle body on which the valve is seated,
C: 0.1-0.5% by weight, Cr: 12-18
%, Mo; 0.5 to 1.5%, Si; 0.03 to 1.0
%, Mn; 0.03 to 0.75%, and the remainder being martensitic stainless steel for cold forging consisting of Fe and unavoidable impurities. 6. The nozzle body according to claim 5, wherein Cu; 0.03 to 0.6%, Ni;
0.03 to 0.6%, V; 0.03 to 0.5% further included in the nozzle body. 7. The nozzle body according to claim 5, wherein P is 0.03% or less of inevitable impurities,
S: 0.01% or less, a nozzle body. 8. A fuel injection system comprising a valve that slides in a guide hole formed in a nozzle body having a fuel injection hole, and the valve moves in the axial direction of the nozzle body to open and close the fuel injection hole. A valve of the apparatus, wherein the valve is C; 0.1-0.5%, Cr; 12-18%, Mo;
0.5-1.5%, Si; 0.03-1.0%, Mn;
A valve characterized by being 0.03 to 0.75% and the remainder being martensitic stainless steel for cold forging which comprises Fe and unavoidable impurities. 9. The valve according to claim 8, wherein Cu: 0.03 to 0.6% and Ni: 0.03 to 0.
6%, V; valve further comprising 0.03-0.5%. 10. The valve according to claim 8 or 9, wherein
Of the unavoidable impurities, P: 0.03% or less, S: 0.0
A valve characterized by being 1% or less.