JP2005069023A - Fuel accumulator for diesel internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel accumulator for a diesel internal combustion engine not having defect such as void of brazing material at a joining part of a fuel accumulator and a branch connection body composed of a branch pipe and a branch metal joint generated and having excellent durability. <P>SOLUTION: This fuel accumulator is a cylindrical fuel accumulator of a spherical fuel accumulator for the diesel internal combustion engine having through holes provided on at least one portion of a circumference wall part of a cylindrical vessel or a circumference wall part of a spherical vessel, a branch pipe or a branch connection body composed of the branch metal joint are brazed under a condition that the same are fitting inserted. The cylindrical fuel accumulator or the spherical fuel accumulator is made of carbon steel material, and brazing is performed with using brazing material composed of 20-30 wt% of Mn, 8-25 wt% of Ni and remainder of Cu and unavoidable impurity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical fuel accumulator vessel or a spherical fuel accumulator vessel such as a high-pressure fuel manifold or a high-pressure fuel block, and in particular, a fuel accumulator for a diesel internal combustion engine that supplies high-pressure fuel exceeding 130 MPa in a diesel internal combustion engine. Concerning the container.
[0002]
[Prior art]
As shown in FIG. 1, a cylindrical fuel pressure accumulating container having a cylindrical inner peripheral wall surface is connected to a cylindrical container 11 as a cylindrical fuel container having a flow passage 11-1 as a branch connection body. The branch pipe 12 is connected directly or via a joint fitting or the like. In addition, as shown in FIG. 2, a spherical fuel accumulating container having a spherical inner peripheral wall surface is a spherical container as a spherical fuel container that forms a space 21-1 having a spherical inner peripheral wall surface at least partially. 21, the branch pipe 12 as a branch connection body is connected directly or via a joint fitting or the like (see Patent Document 1).
[0003]
As shown in FIG. 3, the connecting structure of the branched connecting body of the cylindrical fuel pressure accumulator shown in FIG. 1 includes a branch pipe in the through hole 11-2 that communicates with the flow passage provided in the peripheral wall portion of the cylindrical container 11. The connection end portion 12-1 having the same tube diameter on the 12 side is inserted and connected to each other by brazing, and as shown in FIG. In some cases, the connecting end 14-1 of the metal fitting 14 is inserted and connected to each other by brazing, and the branch pipe 12 is connected by a nut 15 via the branch joint metal fitting 14.
In addition, the connection structure of the branch connection body of the spherical fuel pressure accumulator shown in FIG. 2 is the same as the pipe diameter on the branch pipe 12 side in the through hole 21-2 communicating with the space 21-1 provided in the peripheral wall portion of the spherical container 21. The connection end portion 12-1 is inserted and connected to each other by brazing, and as shown in FIG. 5, the connection end portion 14- of the branch joint fitting 14 is inserted into the through hole 21-2. There is a structure in which 1 is inserted and joined together by brazing, and the branch pipe 12 is connected by a nut 15 via a branch joint fitting 14.
[0004]
However, in a fuel pressure storage container for a diesel internal combustion engine having such a connection structure, a rapid change in supply pressure of a high-pressure fluid over 130 MPa or more, particularly an atmospheric temperature due to heat transfer from the engine, A through-hole of a fuel pressure accumulating vessel in which the branch pipe 12 or the branch joint fitting 14 as the branch connection body is inserted and brazed due to the relative dimensional change between the mating members (the mating seat surfaces) due to ascent and descent A large stress is generated in 11-2 and 21-2, and the cracks are likely to start from the through-hole portion, which may often lead to fuel leakage and the like.
[0005]
In general, the following measures are taken as countermeasures. In order to increase the internal pressure fatigue strength of the pressure accumulating vessel main body and the end of the accumulating vessel opening of the branch connection body, for example, a low pressure steel containing less than 0.18% carbon is used in the fuel accumulating vessel main body. For example, a nickel-brass material is used to join a branch connection body consisting of a branch branch pipe or a branch joint fitting. Examples of the low carbon steel used as the material for the fuel pressure accumulating vessel main body include the old JIS STS35. Moreover, the nickel brazing material conventionally used is BNi-2 defined in JISZ3265, that is, Cr: 6.0 to 8.0 wt%, B: 2.75 to 3.50 wt%, Si: 4.0 to It is generally composed of 5.0 wt%, Fe: 2.5 to 3.5 wt%, C: 0.06 wt% or less, P: 0.02 wt% or less, and the balance Ni (see Patent Document 2). Further, in order to ensure the internal pressure fatigue strength when a high pressure is applied to the fuel pressure accumulating vessel, the material of the fuel pressure accumulating vessel main body is a material having a carbon content exceeding 0.18% and containing a large amount of Cr, such as SCM440. It is conceivable to change to high carbon steel.
However, in the case of high carbon steel such as SCM440, the wetting and spreading of the nickel brazing material such as BNi-2 as defined in JISZ3265 is poor, and therefore the brazed portion is enlarged in FIG. As shown, defects such as voids 31 are likely to occur in the brazing material 30 at the junction of the fuel accumulator vessels 11, 21 and the branch pipe 12 or the branch joint fitting 14. When a high internal pressure is applied to the fuel pressure accumulating container in a state where the void 31 or the like has occurred in the brazing material 30, the stress concentrates on the void 31 in the vicinity where the maximum stress is generated, and the brazing material 30 is cracked. As a result, durability is impaired and fuel leakage or the like is caused.
Further, the nickel brazing material containing chromium such as BNi-2 is combined with carbon in the steel of the fuel pressure accumulating vessel to deposit chromium carbide to form an embrittled portion, so that the same as described above. When a high internal pressure is applied, cracks occur in the chromium carbide portion deposited in the brazing material or in the vicinity of the interface, and the durability is impaired.
[0006]
[Patent Document 1] Japanese Patent Application No. 2002-342820 [Patent Document 2] JP 2000-218389 A
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems of the prior art, and defects such as voids do not occur in the brazing material of the junction of the fuel accumulator vessel and the branch connection body consisting of the branch pipe and the branch joint fitting. An object of the present invention is to provide a fuel pressure storage container for a diesel internal combustion engine made of high carbon steel such as SCM440, which does not contain chromium carbide and does not precipitate chromium and has sufficient durability.
[0008]
[Means for Solving the Problems]
A fuel pressure storage container for a diesel internal combustion engine according to the present invention is in a fuel container having a cylindrical or spherical inner peripheral curved wall surface, and is a peripheral wall portion or a spherical container extending in the axial direction of the cylindrical container communicating with the internal flow passage. A diesel internal combustion engine in which a through hole at at least one location is provided in the peripheral wall portion of the cylinder, and a branch connection body made of a branch branch pipe or a branch joint fitting is inserted into the through hole and brazed to each other to be connected. In the cylindrical fuel accumulator vessel or the spherical fuel accumulator vessel for engines, the cylindrical fuel accumulator vessel or the spherical fuel accumulator vessel is made of a high carbon steel material containing 0.18 wt% or more of carbon, and Mn: 20 to 30 wt%, It is characterized by being brazed using a brazing material comprising Ni: 8 to 25 wt%, the balance Cu and unavoidable impurities.
[0009]
That is, the present invention uses a high-carbon steel (containing carbon of 0.18 wt% or more) such as SCM440 instead of the conventional low-carbon steel as the material of the fuel pressure accumulator main body, and further uses SCM440 or the like as a brazing material. Fuel accumulator vessel having high internal pressure fatigue strength by using a brazing material composed of Mn: 20 to 30 wt%, Ni: 8 to 25 wt%, balance Cu and unavoidable impurities even in high carbon steel and having good wetting and spreading of the brazing material In addition to obtaining a main body, a brazed joint having sufficient durability is obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the material of the fuel pressure accumulating vessel main body is made of a high carbon steel material containing 0.18 wt% or more of carbon, which is sufficient to withstand a high injection pressure of 130 MPa when the carbon content is less than 0.18 wt%. This is because a high fatigue strength cannot be obtained.
[0011]
In addition, the brazing material used in the present invention is limited to the brazing material composed of Mn: 20 to 30 wt%, Ni: 8 to 25 wt%, the balance Cu and unavoidable impurities, for the reason described below.
That is, the reason why the main material of the brazing material is Cu is to improve the wetting and spreading of the brazing material even in the case of high carbon steel.
The reason why Mn is limited to 20 to 30 wt% is that the brazing filler metal itself has a low strength if it is less than 20 wt%, whereas the brazing filler metal becomes brittle and the fatigue strength is low if it exceeds 30 wt%.
The reason why Ni is limited to 8 to 25 wt% is that when the content is less than 8 wt%, the strength of the brazing material itself is weak, whereas when it exceeds 25 wt%, the wettability is deteriorated and voids are easily generated.
Further, the reason why chromium is not contained as a brazing filler metal component is that brittle chromium carbide is not deposited even if carbon diffuses into the brazing filler metal from the fuel pressure accumulating vessel main body having a large amount of carbon.
[0012]
【Example】
Examples of the present invention will be described below together with comparative examples.
Example 1
Wetting and spreading test of copper manganese nickel brazing material of the present invention:
Discs (diameter 31 mm x thickness) from each parent material made of SCM440 (C: 0.39 wt%), SCM445 (C: 0.46 wt%), former JIS G3455 STS35 (C: 0.08 to 0.18 wt%) 5 mm) is prepared and washed, and 0.1 gf of brazing material (Mn: 25 wt%, Ni: 10 wt%, remaining Cu) is supplied to each plane and passed through a continuous furnace (set temperature 1100 ° C.) in a hydrogen atmosphere. Thereafter, the area of the brazing material that melted and spread on each disk was measured. The area of the brazing material was measured with a contour obtained by capturing an image with a CCD camera through an actual microscope.
As a result, the material is SCM440, SCM445, the area of the braze to the surface area 755Mm ² of each disc of the old JIS STS35 were respectively ^{730mm 2, 706mm 2, 110mm 2} .
[0013]
Comparative Example 1
Wet spread test of conventional BNi-2 brazing material (nickel brazing material):
As in Example 1, the material is a disk from each parent material of SCM440 (C: 0.39 wt%), SCM445 (C: 0.46 wt%), and old JIS STS35 (C: 0.18 to 0.2 wt%). (Diameter 31mm x Thickness 5mm) After creating and washing, 0.1gf of BNi-2 brazing material is supplied to each plane and passed through a continuous furnace (set temperature 1100 ° C), then melted on each disk Then, the area of the brazing material spread was measured. The area of the brazing material was measured with a contour obtained by capturing an image with a CCD camera through an actual microscope.
As a result, the material is SCM440, SCM445, the area of the braze to the surface area 755Mm ² of each disc of the old JIS STS35 were respectively ^{171mm 2, 167mm 2, 150mm 2} .
[0014]
Example 2
A cylindrical fuel accumulator main body shown in FIG. 1 having a material SCM440, an outer diameter φ26 mm, an inner diameter φ9 mm, and a wall thickness t8.5 mm is provided with a material ST52, a branch branch pipe having an outer diameter φ6.3 mm, an inner diameter φ3 mm, and a wall thickness t1.65 mm. The brazing material of Example 1 (Mn: 25 wt%, Ni: 10 wt%, remaining Cu) was joined under the following conditions. In addition, the connection structure of the branch branch pipe of the cylindrical fuel pressure accumulating vessel in this embodiment was the same as that shown in FIG.
<Brazing conditions>
Using a brazing material in which copper manganese nickel brazing material was linear, brazing was performed in a continuous furnace at a brazing operation temperature of 1100 ° C. in a hydrogen gas atmosphere.
The cylindrical fuel pressure accumulator obtained by brazing in this manner was subjected to an internal pressure fatigue test in which the pressure fluctuation of 20 to 200 MPa was repeated with the fluid in the container and repeated 10 million times. No cracks were observed at the junction between the accumulator body and the branch branch pipe, indicating excellent strength. This is presumably because no defects such as voids occurred in the brazing material at the joint, and there was no precipitation of chromium carbide.
[0015]
Example 3
The same material SCM440 as in Example 1, outer diameter φ26 mm, inner diameter φ9 mm, and wall thickness t8.5 mm cylindrical fuel accumulator body shown in FIG. 1 is made of the former material JIS STS35, screw wall outer diameter φ14 mm, straight portion outer diameter φ6. .3 mm, inner diameter φ3 mm, wall thickness t1.65 mm branch joint fitting using the brazing material of Example 1 (Mn: 25 wt%, Ni: 10 wt%, balance Cu), and the same brazing conditions as in Example 2 And joined. In addition, the connection structure of the branch joint metal fitting of the cylindrical fuel accumulator vessel in the present embodiment was the same as that shown in FIG.
About the cylindrical fuel pressure accumulator obtained by brazing in this way, as a result of carrying out an internal pressure fatigue test under the same conditions as in Example 2, also in the present example, at the joint between the fuel pressure accumulator body and the branch joint fitting The occurrence of cracks was not confirmed at all, and the strength was excellent. Therefore, it is presumed that in this case as well, no defects such as voids occurred in the brazing material at the joint, and no chromium carbide was deposited.
[0016]
Comparative Example 2
The same material SCM440 as in Example 1, outer diameter φ26 mm, inner diameter φ9 mm, wall thickness t8.5 mm cylindrical fuel accumulator main body shown in FIG. 1, branch branch pipe used in Example 2 and branch used in Example 3 Example 2 of the cylindrical fuel pressure accumulator obtained by joining the joint metal fitting under the same brazing conditions as in Example 2 using the conventional BNi-2 brazing material (nickel brazing material) of Comparative Example 1 above. As a result of carrying out the internal pressure fatigue test under the same conditions as in Example 1, each joint portion of the branch branch pipe and the branch joint fitting was damaged after 850,000 times. This is because defects such as voids occur in the brazing material at the joint, stress concentrates on the voids in the vicinity where the maximum stress occurs, and chromium carbide precipitates in the brazing material or near the interface, causing cracks in the brazing material. This is presumably due to the fact that the durability was impaired due to the occurrence of
[0017]
In addition, although only the Example applied to the cylindrical fuel pressure accumulator was shown here, the same excellent effect can be obtained even if the present invention is applied to the spherical fuel pressure accumulator shown in FIGS. Not too long.
[0018]
【The invention's effect】
As described above, the fuel pressure storage container for a diesel internal combustion engine according to the present invention can provide a fuel pressure storage container main body having high internal pressure fatigue strength and a brazed joint having sufficient durability. The fuel injection pressure in the engine can be increased to improve the combustion conditions, and the safety is also excellent.
[Brief description of the drawings]
FIG. 1 is a partially broken explanatory view showing an embodiment of a cylindrical fuel pressure accumulating container as an object of the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a spherical fuel accumulator vessel that is an object of the present invention.
FIG. 3 is a cross-sectional view showing a connecting portion by a branch pipe of the cylindrical fuel pressure accumulating container shown in FIG. 1;
4 is a cross-sectional view showing a connection portion by a branch joint fitting of the cylindrical fuel pressure accumulator shown in FIG. 1. FIG.
5 is a cross-sectional view showing a connection portion by a branch joint fitting of the spherical fuel pressure accumulator shown in FIG. 2;
FIG. 6 is an enlarged partial cross-sectional view showing a part of a brazed joint portion between a fuel accumulator vessel and a branch connector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Cylindrical container 11-1 Flow path 11-2, 21-2 Through-hole 12 Branch pipe 12-1 Connection end part 14 Branch joint metal fitting 14-1 Connection end part 15 Nut 21 Spherical container 21-1 Space 30 Brazing material 31 void

Claims (1)

In a fuel container having a cylindrical or spherical inner circumferential curved wall surface, a through-hole at at least one location is formed in the circumferential wall portion extending in the axial direction of the cylindrical container leading to the internal flow passage or the circumferential wall portion of the spherical container. In a cylindrical fuel pressure storage container or a spherical fuel pressure storage container for a diesel internal combustion engine, which is provided and configured to be connected by brazing each other with a branch connection body made of a branch branch pipe or a branch joint fitting inserted into the through hole. The cylindrical fuel storage container or the spherical fuel storage container is made of a high carbon steel material containing 0.18 wt% or more of carbon, and Mn: 20 to 30 wt%, Ni: 8 to 25 wt%, remaining Cu and inevitable impurities A fuel pressure storage container for a diesel internal combustion engine, wherein the branch connector is brazed using a brazing material made of

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