U.S. patent application number 15/542077 was filed with the patent office on 2018-01-25 for fuel rail for gasoline direct injection.
The applicant listed for this patent is USUI CO., LTD.. Invention is credited to Koichi HAYASHI.
Application Number | 20180023157 15/542077 |
Document ID | / |
Family ID | 56416553 |
Filed Date | 2018-01-25 |
United States Patent
Application |
20180023157 |
Kind Code |
A1 |
HAYASHI; Koichi |
January 25, 2018 |
FUEL RAIL FOR GASOLINE DIRECT INJECTION
Abstract
To obtain, at low cost, a fuel rail that maintains low hardness
and good formability before being formed into a tube stock, can be
made to form a welded pipe, and has high-strength properties with
which the fuel rail can withstand a high fuel pressure even when
formed so as to be relatively thin. A fuel rail for gasoline direct
injection that is used at a fuel pressure of at least 30 MPa and is
formed from an iron-alloy welded pipe. The fuel rail comprises an
iron alloy that contains chemical components of C, Si, Mn, P, S,
Nb, and Mo. The plate thickness t and the outer diameter D of the
fuel rail have a ratio t/D of 0.2 or less. A bainitic structure can
be precipitated by brazing the fuel rail in a furnace during
manufacturing.
Inventors: |
HAYASHI; Koichi; (Sunto-gun,
Shizuoka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
USUI CO., LTD. |
Sunto-gun, Shizuoka |
|
JP |
|
|
Family ID: |
56416553 |
Appl. No.: |
15/542077 |
Filed: |
December 14, 2015 |
PCT Filed: |
December 14, 2015 |
PCT NO: |
PCT/JP2015/006215 |
371 Date: |
July 7, 2017 |
Current U.S.
Class: |
428/544 |
Current CPC
Class: |
C22C 38/04 20130101;
C22C 38/48 20130101; C21D 2211/002 20130101; C21D 9/08 20130101;
C22C 38/44 20130101; C22C 38/02 20130101; C22C 38/002 20130101;
F02M 55/04 20130101; F02M 55/025 20130101; C22C 38/12 20130101;
F02M 2200/9053 20130101 |
International
Class: |
C21D 9/08 20060101
C21D009/08; C22C 38/44 20060101 C22C038/44; F02M 55/02 20060101
F02M055/02; C22C 38/02 20060101 C22C038/02; C22C 38/00 20060101
C22C038/00; C22C 38/48 20060101 C22C038/48; C22C 38/04 20060101
C22C038/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 22, 2015 |
JP |
2015-009969 |
Claims
1. A fuel rail for gasoline direct injection at a fuel pressure of
at least 30 MPa, characterized in that it is formed from an
iron-alloy welded pipe, wherein the fuel rail comprises an iron
alloy that contains chemical components of C, Si, Mn, P, S, Nb, and
Mo, wherein the plate thickness t and the outer diameter D of the
fuel rail have a ratio t/D of 0.2 or less, and wherein a bainitic
structure can be precipitated by copper-brazing the fuel rail in a
furnace during manufacturing.
2. The fuel rail for gasoline direct injection of claim 1,
characterized in that the fuel pressure is from 30 kPa to 80 kPa.
Description
TECHNICAL FIELD
[0001] The invention relates to a fuel rail for gasoline direct
injection.
BACKGROUND ART
[0002] The fuel pressure of a conventional gasoline direct
injection system is 20 MPa or less and pressure-resistance strength
is ensured by keeping a specified thickness of the fuel rail. It is
unnecessary to use especially high-strength material in such a
region of fuel pressure and as the fuel rail is comparatively
thin-walled, it is possible to produce a welded tube. However, in
recent years, fuel pressure of gasoline direct injection system has
been further increased as indicated in patent documents 1 and 2,
and at present exceeds 30 MPa in order to improve fuel efficiency
and due to more stringent emission regulations. For that reason, it
is necessary for the fuel rail to be formed thick to withstand such
high pressure.
PRIOR ART DOCUMENTS
Patent Documents
[0003] Patent document1: JP200716668
[0004] Patent document2: JP2010007651
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0005] However, because it is difficult to fabricate a welded tube
with roll-forming which has sufficient tube thickness to withstand
the fuel pressure of 30 MPa or more, there is no other option than
to manufacture a seamless pipe but its manufacturing is of high
cost. Also, as a method other than thickening, it is conceivable to
form a thin material by strengthening the material itself, but
since the high-strength material used in the past has a large
carbon content, it is difficult to satisfy the high strength
property which is the original objective because the surface is
decarburized due to high temperature during brazing in the furnace
and the fatigue strength decreases. Further, such a material is
unsuitable for welding and it is impossible to sufficiently ensure
the quality of welding.
[0006] This invention aims at solving the problem mentioned above,
and therefore, at obtaining, at low cost, a fuel rail that
maintains low hardness and good formability before being formed
into a tube stock, so that it can be made to form a welded pipe by
roll forming, and has high-strength properties with which the fuel
rail can withstand a high fuel pressure even when formed into a
relatively thin thickness.
Means for Solving the Problem
[0007] It is therefore an object of the present invention to solve
the problems as described above and it is an object of the present
invention to provide a fuel rail for gasoline direct injection at a
fuel pressure of 30 MPa or more which is formed from an iron-alloy
welded pipe wherein the fuel rail comprises an iron alloy that
contains chemical components of C, Si, Mn, P, S, Nb, and Mo,
wherein the plate thickness t and the outer diameter D of the fuel
rail have a ratio of t/D of 0.2 or less, and wherein a bainitic
structure can be precipitated by brazing it in a furnace during
manufacturing. Note that, in-furnace brazing processing of the
invention means a process of rising the temperature to 1000.degree.
C. or more in a furnace and then cooling down gradually from that
temperature to room temperature.
[0008] The fuel pressure may be 30 MPa.about.80 MPa.
Effects of the Invention
[0009] The invention comprises an iron alloy that includes chemical
components of C, Si, Mn, P, S, Nb, and Mo as mentioned above and
forms ferrite structure or ferrite-pearlite structure before being
formed into a tube stock. For that reason, low hardness can be
maintained in this state and the quality of welding can be
satisfactorily held so that it is possible to easily process a fuel
rail.
[0010] In addition, a bainitic structure is precipitated by
performing an in-furnace brazing processing in the manufacturing
process. As a result, the material composed of this bainitic
structure has high strength to ensure high pressure resistance
compared to conventional materials. The entire shape can be formed
to have a thin wall and to be light-weighted and the welded pipe
can be formed by roll-forming at low cost, and thus the invention
provides a product allowed to be used at a fuel pressure of 30 MPa
or more due to characteristics such as high strength and high
pressure resistance.
Modes for Carrying Out the Invention
[0011] A fuel rail for gasoline direct injection of the Examples of
this invention is described below. First, among the iron alloy
materials constituting this example, the chemical components
excluding iron and impurities and the compounding ratio to all the
components are shown in Table 1 below.
TABLE-US-00001 TABLE 1 C(%) Si(%) Mn(%) P(%) S(%) Nb(%) Mo(%) Ni(%)
Cr(%) Example 1 0.20 0.21 1.63 0.010 0.002 0.026 0.38 -- -- Example
2 0.18 0.20 1.25 0.015 0.002 0.025 0.25 -- -- Comparative 0.02 0.33
1.33 0.036 0.022 -- -- 9.89 18.35 Example 1
[0012] Examples 1 and 2 of the invention include C, Si, Mn, P, S,
Nb, and Mo, as shown above. The production method of Examples 1 and
2 is as follows. Examples 1 and 2 are iron alloys comprising the
chemical components shown in Table 1 above, in addition to iron and
the other impurities. This material was then formed into a welded
pipe with its both ends closed by parts, and sockets and fixtures
were installed in the pipe, respectively. Next, the completed
assembly is subjected to copper-brazing in a furnace at temperature
of 1000.degree. C. or more, annealed, and then, shipped as a
product after passing through the process of die matching, leak
checking, or the like.
[0013] The fuel rails of Examples 1 and 2 were copper-brazed in a
furnace as mentioned above, and during this copper brazing process,
the temperature in a furnace raised to 1000.degree. C. or more, and
after that, cooled down slowly. Physical properties of the iron
alloy of Examples 1 and 2 made of the materials as described above
change due to the copper-brazing in the furnace. In order to
examine changes in physical properties before and after the
copper-brazing in the furnace, physical property testing was
conducted based on the JIS standard.
[0014] Specifically, JIS5 test pieces (test piece thickness 1.6 mm,
formed width 25 mm, and formed length 350 mm) of the materials of
Examples 1 and 2 were formed at first and then tensile testing and
structure observation were conducted by using these test pieces.
The results of the tensile testing and structure observations are
shown in Table 2 below. Note that, "Before" and "After" mean the
state before the tube stock being formed, and the state after the
tube stock being copper-brazed in a furnace, respectively.
TABLE-US-00002 TABLE 2 Tensile 0.2 Prof Extension Strength Stress
Coefficient Hardness (MPa) (MPa) (%) (HV) Structure Examples Before
After Before After Before After Before After Before After 1 675 722
434 499 23.2 23.4 225 238 Ferrite Bainite Ferrite- Pearlit 2 568
628 361 434 26.6 16.0 190 211 Ferrite Bainite Ferrite- Pearlit
[0015] As shown in Table 2, the values of tensile strength, 0.2%
proof stress, and hardness after the copper-brazing in the furnace
were larger than those values before being formed into the tube
stock. Precipitation of bainite occurred in both Example 1 and
Example 2 after copper-brazing in a furnace, according to structure
observation of the tube. By contrast, the structure before being
formed into a tube stock was either Ferrite or Ferrite-Pearlite
only, and no bainite structure was found.
[0016] It was confirmed from this result that the fuel rail of
Examples 1 and 2 containing chemical components of C, Si, Mn, P, S,
Nb, and Mo formed a bainite structure due to the process of
copper-brazing in the furnace, and high strength and high hardness
properties could be obtained compared with the state before being
formed into a tube stock. Further, it was confirmed that as the
state before being formed into a tube stock had the same ferrite or
ferrite-pearlite structure as the conventional one have, and the
quality of welding can be satisfactorily maintained and the
material was superior in good formability.
[0017] In addition, tensile testing and structure observation were
conducted based on the JIS standard, about the materials used in
Example 1 and 2, and the materials used in conventional fuel rails,
for confirming the difference in the materials' physical properties
between those of Examples 1 and 2 and the conventional fuel rail
containing different chemical components compared to Examples 1 and
2. Among the iron alloy materials constituting Comparative Example
1, the chemical components excluding iron and impurities and the
compounding ratio to all the components are shown in Table 1 below.
As shown in Table 1, Comparative Example 1 does not include Nb and
Mo, and its chemical components are different from that of Examples
1 and 2, and also include Ni and Cr which are not included in the
materials of Examples 1 and 2. Note that, JIS5 test pieces (test
piece thickness 1.6 mm, formed width 25 mm, and formed length 350
mm) are used in Comparative Example 1, just like Examples 1 and 2.
The results are shown in Table 3 below.
TABLE-US-00003 TABLE 3 Tensile Strength (MPa) Hardness (HV)
Structure Example 1 722 238 Bainite Example 2 628 211 Bainite
Comparative Example 520 150 Austenite 1
[0018] As it turned out, Examples 1 and 2 exhibit higher values
with regard to both tensile strength and hardness compared to
Comparative Example 1. Also, when the structure observations were
conducted, Examples 1 and 2 precipitated a bainitic structure while
Comparative Example 1 exhibits an austenite structure, showing no
precipitation of a bainitic structure. Thus, higher strength and
higher hardness of Examples 1 and 2 were confirmed in comparison
with the conventional materials.
[0019] Further, as an example, the fuel rail made of a material of
Examples 1 and 2 mentioned above can be formed into a product
having the sizes shown in Table 4. Note that, D and t in Table 4
means outside diameters and thicknesses of the fuel rail,
respectively. And a in Table 4 is mainly used under fuel pressure
around 30 MPa, and when formed from the materials of Examples 1 and
2, its outer diameter D is 11 mm, the wall thickness t is 2.0 mm
and it can be formed to be thin with t/D of 0.2 or less. On the
other hand, in the case of a conventional product formed from the
material of Comparative Example 1, since the outer diameter must be
15 mm and the wall thickness 4.0 mm in order to be usable under the
fuel pressure around 30 MPa, t/D is higher than 0.2 and must be
formed to be much thicker than that formed by the materials of
Examples 1 and 2.
[0020] In addition, b in Table 4 is mainly used under the fuel
pressure of around 80 MPa, and when formed from the materials of
Examples 1 and 2, its outer diameter is 13 mm and its wall
thickness is 2.3 mm, T/D can be formed to be as thin as 0.2 or
less. In contrast, in the case of using the material of Comparative
Example 1, since the outer diameter is 20 mm and the wall thickness
is 5.8 mm in order to be used under the fuel pressure around 80
MPa, t/D is higher than 0.2, In this case as well, it must be
formed to be much thicker than that formed by the materials of
Examples 1 and 2.
TABLE-US-00004 TABLE 4 Examples 1 and 2 Comparative Example 1 a D =
11 mm, t = 2.0 mm t/D = 0.18 D = 15m, t/D = 0.27 t = 4.0 mm b D =
13 mm, t = 2.3 mm t/D = 0.18 D = 20 mm, t/D = 0.29 t = 5.8 mm
[0021] From the above results, it can be seen that a fuel rail made
of a material of Examples 1 and 2 can be formed to have a thin wall
and to be light-weighted compared with a conventional material, and
it can be made to form a welded pipe by roll forming, gaining high
strength and high pressure resistance. Thus, it is possible to
obtain a product at a low price and in an easy manner that can cope
with high a fuel pressure of 30 MPa.about.80 MPa.
* * * * *