U.S. patent application number 09/887110 was filed with the patent office on 2001-11-22 for fuel injection valve coated with anti-fouling perfluoropolyether fim layer and associated method, and direct injection engine using same.
This patent application is currently assigned to Hitachi Ltd.. Invention is credited to Ito, Yutaka, Kawashima, Kenichi, Sasaki, Hiroshi, Sekine, Atsushi, Shouji, Mitsuyoshi, Tanabe, Yoshiyuki.
Application Number | 20010042801 09/887110 |
Document ID | / |
Family ID | 14730049 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042801 |
Kind Code |
A1 |
Shouji, Mitsuyoshi ; et
al. |
November 22, 2001 |
Fuel injection valve coated with anti-fouling perfluoropolyether
fim layer and associated method, and direct injection engine using
same
Abstract
The invention provides for a fuel injection valve for a direct
gasoline injection engine, a direct injection engine and an
automobile using the same, which can prevent the deposits produced
during combustion of gasoline from accumulating on the surface of
the fuel injection valve, or easily remove the deposits therefrom.
A reaction-bonded layer of perfluoropolyether compounds having
alkoxy silane as its terminal group is provided on the surface of
the fuel injection valve of the invention.
Inventors: |
Shouji, Mitsuyoshi;
(Taga-gun, JP) ; Sasaki, Hiroshi; (Naka-gun,
JP) ; Kawashima, Kenichi; (Hitachinaka-shi, JP)
; Ito, Yutaka; (Takahagi-shi, JP) ; Tanabe,
Yoshiyuki; (Hitachinaka-shi, JP) ; Sekine,
Atsushi; (Mito-shi, JP) |
Correspondence
Address: |
CROWELL & MORING, L.L.P.
Intellectual Property Group
P.O. Box 14300
Washington
DC
20044-4300
US
|
Assignee: |
Hitachi Ltd.
|
Family ID: |
14730049 |
Appl. No.: |
09/887110 |
Filed: |
June 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09887110 |
Jun 25, 2001 |
|
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09300523 |
Apr 28, 1999 |
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6273348 |
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Current U.S.
Class: |
239/585.1 ;
123/305 |
Current CPC
Class: |
F02M 61/18 20130101;
F02M 61/166 20130101; F02M 69/045 20130101; B05D 5/083 20130101;
Y02T 10/12 20130101; Y02T 10/123 20130101; F02B 2075/125 20130101;
F02B 23/101 20130101; F02M 51/0678 20130101; F02M 51/0675
20130101 |
Class at
Publication: |
239/585.1 ;
123/305 |
International
Class: |
F02B 005/00; B05B
001/30; F02M 051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 1998 |
JP |
10-118177 |
Claims
What is claimed is:
1. A fuel injection valve coated with an organic layer of film on
the surface of its fuel injection port, wherein said organic film
of layer comprises a perfluoropolyether compound having a molecular
weight of 2000 to 6000 in average.
2. A fuel injection valve coated with an organic layer of film on
the surface of its fuel injection port, wherein said organic film
of layer comprises a perfluoropolyether compound as defined in the
following chemical compound 1, F--(C.sub.XF.sub.2XO).sub.n--A or
A--{(C.sub.XF.sub.2XO).sub.n}--A, (Comp. 1) wherein X is an integer
from 1 to 3 which may differ upon repetition, n is a value at which
a numeric average molecular weight of --(C.sub.XF.sub.2XO).sub.n--
becomes 2000 or more, and A is a residue.
3. A fuel injection valve coated with an organic layer of film on
the surface of its fuel injection port, wherein said organic layer
of film comprises a perfluoropolyether compound as defined in the
following chemical compound 2
F--(C.sub.XF.sub.2XO).sub.n--C.sub.2F.sub.4--B or
B--{--(C.sub.XF.sub.2XO).sub.n}--B, (Comp. 2) wherein X is an
integer from 1 to 3 which may differ upon repetition, n is a value
at which a numeric average molecular weight of
--(C.sub.XF.sub.2XO).sub.n-- becomes 2000 or more, and B is a
residue of alkoxy silane group.
4. A fuel injection valve coated with an organic layer of film on
the surface of its fuel injection port, wherein said organic layer
of film comprises forming a layer of perfluoropolyether compounds 1
or 2 on the surface thereof via a bonding acceleration layer which
is an organic polymer film or an oxide film, wherein
F--(C.sub.XF.sub.2XO).sub.n--A or A--{(C.sub.XF.sub.2XO).sub.n}--A,
(Comp. 1) F--(C.sub.XF.sub.2XO).sub.n-- -C.sub.2F.sub.4--B or
B--{--(C.sub.XF.sub.2XO).sub.n}--B, (Comp. 2) and wherein X is an
integer from 1 to 3 which may differ upon repetition, n is a value
at which a numeric average molecular weight of
--(CXF.sub.2XO).sub.n-- becomes 2000 or more, A is a residue, and B
is a residue of alkoxy silane group.
5. A fuel injection valve according to either one of claims 1-4,
wherein said layer of perfluoropolyether compound has a thickness
in a range from 1.5 nm to 30 nm.
6. A fuel injection valve having an organic film coating, which has
a thickness in a range from 1.5 nm to 30 nm, on the surface of its
fuel injection port and its vicinity.
7. A fuel injection valve having an organic film coated on the
surface of its fuel injection port, wherein said fuel injection
port has a nozzle which is capable of atomizing fuel into a
particle size of 20 .mu.m or less.
8. A fuel injection valve having an organic film coated on the
surface of its fuel injection port, wherein said fuel injection
port is 0.3-0.8 mm in diameter.
9. A fuel injection valve having an organic film coated on the
surface of its fuel injection port, wherein said fuel injection
port and a portion in the vicinity thereof comprise a kind of
ferrite stainless steel which includes 0.6-1.5 wt % of C, 1 wt % or
less of Si, 1.5 wt % or less of Mn and 15-20 wt % of Cr.
10. A fuel injection valve according to either one of claims 6-9,
wherein said organic coating of film comprises one of
perfluoropolyether compounds of the following compounds 1 and 2
which has an average molecular weight from 2000 to 6000,
F--(C.sub.XF.sub.2XO).sub.n--A or A--{(C.sub.XF.sub.2XO).sub.n}--A,
(Comp. 1) F--(C.sub.XF.sub.2XO).sub.n-- -C.sub.2F.sub.4--B or
B--{--(C.sub.XF.sub.2XO).sub.n}--B, (Comp. 2) and wherein X is an
integer from 1 to 3 which may differ upon repetition, n is a value
at which a numeric average molecular weight of
--(C.sub.XF.sub.2XO).sub.n-- becomes 2000 or more, A is a residue,
and B is a residue of alkoxy silane group.
11. A fuel injection valve according to either one of claims 6-10,
wherein a thickness of said layer is 1.5 nm to 10 nm.
12. A direct injection engine having a cylinder head with air
intake means and exhaust means provided in a combustion chamber, a
piston reciprocating in said cylinder, fuel injection means for
injecting fuel into said combustion chamber, and ignition means for
igniting atomized fuel from said fuel injection means, wherein said
fuel injection means comprises either one of fuel injection valves
according to claims 1 to 11.
13. A direct injection engine having a cylinder head with air
intake means and exhaust means provided in a combustion chamber, a
piston reciprocating in said cylinder, fuel injection means which
is provided for injecting fuel into said combustion chamber such
that fuel is atomized to have an air/fuel ratio of 45 or greater
suitable for a lean burn control, and ignition means for igniting
atomized fuel from said fuel injection means, wherein said fuel
injection means comprises an organic film coated on the surface of
its fuel injection port and a portion in the vicinity thereof.
14. A direct injection engine having a cylinder head with air
intake means and exhaust means provided in a combustion chamber, a
piston reciprocating in said cylinder, fuel injection means which
is provided for injecting fuel into said combustion chamber such
that fuel is atomized to have an air/fuel ratio of 45 or greater
suitable for a lean burn control, and ignition means for igniting
atomized fuel from said fuel injection means, wherein said port and
its vicinity in the vicinity comprise a kind of ferrite stainless
steel including 0.6-1.5 weight % of C, less than 1 weight % of Si,
less than 1.5 weight % of Mn, and 15-20 weight % of Cr, wherein
said injection port is 0.3-0.8 mm of diameter, capable of atomizing
fuel whose particle size is less than 20 .mu.m, and wherein a
thickness of said organic layer of film provided on the surface of
said injection port and its vicinity is 1.5-10 nm.
15. An automobile having a direct injection engine according to
either one of claims 1-14.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a novel fuel injection
valve for a direct injection engine, and in particular, it relates
to a fuel injection valve and a direct injection type engine using
the same for an automobile.
DESCRIPTION OF RELATED ART
[0002] A gasoline direct injection engine is comprised of a
cylinder block, a piston having a piston ring, which is inserted in
the cylinder block, and a cylinder head which is in the upper
portion of the cylinder block. A combustion chamber is formed in a
space surrounded by an internal wall of the cylinder block, an
upper surface of the piston and a bottom surface of the cylinder
head. Substantially in the center portion of the cylinder head,
there is mounted an ignition plug. An air-intake valve and an
exhaust valve are provided near the ignition plug. In addition, a
fuel injection valve 1 is provided for directly injecting fuel into
the combustion chamber. Atomized fuel injected from the fuel
injection valve 1 impinges on a concave surface at the top of the
piston to be reflected and guided toward the vicinity of the
ignition plug which is substantially in the center portion of the
cylinder head, whereby realizing a stratified lean burn combustion
is realized.
[0003] The fuel injection valve of the gasoline direct injection
engine, which is installed within the engine cylinder, is exposed
to a high temperature combustion gas. In this condition, deposits
produced by combustion of gasoline tend easily to accumulate on the
tip of the fuel injection valve, thereby distorting a fuel
atomization pattern specified to take place within the engine
cylinder, consequently resulting in a decrease of its fuel flow
rate, and deterioration of a fuel-air mixture, thereby causing its
combustion to become very unstable. A cause of the deposits is
considered to be due to accumulation of soot produced in the
combustion chamber, and a gumlike substance produced by thermal
decomposition of gasoline. In particular, when the temperature in
the circumference of the fuel injection valve is higher than
160.degree. C., the deposits are reported to be easily accumulated.
Several methods have been tried for cleaning such deposits by
mixing additives into gasoline or by reducing the coarseness of the
surface of the fuel injection valve (Jidosha-gijyutsu-kai;
symposium preprint 976 (1997-10)). Further, many attempts have been
made to drop the temperature of the tip end of the injection valve
as disclosed in JPA Laid-Open No. 9-264232. However, it has been
difficult by any of these attempts effectively to reduce the
deposits. JPA Laid-Open No.9-264232 discloses that the surface of
the fuel injection valve is made oleophobic so as to be able easily
to remove the deposits, and prevent the decrease of fuel flow.
According to this method, a fluoroalkyl compound is reaction-bonded
on the surface of the fuel injection valve so as to make its
surface oleophobic. Still further, according to JPA Laid-Open No.
7-246365, it is disclosed that the surface of the fuel injection
valve is treated by a sol-gel method using a mixture solution of a
metal alkoxide and a fluoroalkyl group substituted metal alkoxide
which is prepared by substituting a part of alkoxyl group with a
fluoroalkyl group, thereby making the surface of the fuel injection
valve oleophobic such that the deposits can be easily removed and
the decrease in the fuel flow can be prevented. This method
includes such one whereby a mixture solution of a fluoroalkyl group
substituted metal alkoxid compound and a metal alkoxide is
reaction-bonded on the surface of the fuel injection valve so as to
make its surface oleophobic, and such ones to form various films as
disclosed in JUP Nos.55-116875 and 56-25067. However, these methods
are accompanied with a problem to be solved that when the
temperature at the tip end of the fuel injection valve exceeds a
point at which 90% of the fuel used evaporates, accumulation of
deposits progresses on the fuel injection valve so as to reduce the
area of opening of the fuel injection valve's port, thereby
decreasing the flow rate of the fuel.
SUMMARY OF THE INVENTION
[0004] The cause of the production of the deposits is considered,
as described in JPA Laid-Open No.9-264232, to be that high residual
components in the fuel tend to remain on the surface of the fuel
injection valve, and its residual as a core causes subsequent
dehydrogenation and polymerization reactions. The prior art method
of reaction-bonding the fluoroalkyl compound on the surface of the
fuel injection valve so as to be able easily to peel off the
deposits is involved with the problem that when the temperature at
the tip end of the fuel injection valve is raised as high as to
increase the production of the deposits, its effect is reduced.
[0005] Further, the method disclosed in JPA Laid-Open No.7-246365
whereby the mixture of the metal alkoxide and the fluoroalkyl group
substituted metal alkoxide was baked on the surface of the fuel
injection valve so as to render the surface of the injection valve
oleophobic thereby improving its deposit peel-off capability, is
associated with a problem that when the temperature at the tip end
of the injection valve is raised and the production of the deposits
increases accordingly, its overall effect is reduced. This cause is
considered, as discussed in JPA Laid-Open No.10-159687, to be that
the provision of the oleophobic property was insufficient to
realize its designed function. Still further, it is necessary for
this oleophobic property to exist stably in conditions of a high
fuel pressure, high combustion pressure, and high surface
temperatures of 150 to 200.degree. C. on the surface of the
injection valve.
[0006] In order to solve the problems associated with the prior
art, it is contemplated effective to coat the surface of the fuel
injection valve with a fluorine film having a low surface energy,
or to reaction-bond a thick film thereon using a fluorine compound
having a long chain according to the invention. By provision of
such coating or film, the deposits thereon can be cleaned out
easily by the fuel of gasoline thereby advantageously preventing
adhesion of the deposits thereon. If this object of the invention
is realized, a stable combustion pattern designated for a highly
reliable gasoline direct injection engine can be achieved. In order
to accomplish the object of the invention, there are the following
problems to be solved.
[0007] A material suitable for this object must be able to exist
stably on the surface of the fuel injection valve under conditions
of 5-12 MPa of fuel pressures, and 150-200.degree. C. of
temperatures on the surface of the fuel injection valve, and in
addition, must be able to provide a low surface energy with the
oleophobic property. Here, the stability (to exist stably) refers
to that the material must be nonflammable even if in an environment
exposed to the combustion of gasoline for a long time, therefore
requiring a high oxidation stability, thermal stability, and
gasoline stability, as well as a high adhesion to the surface of
the fuel injection valve. Thereby, these problems must have been
solved.
[0008] The object of the invention is to provide for a fuel
injection valve for use in a gasoline direct injection engine, a
gasoline direct injection engine and an automobile using the same,
which can prevent the deposit produced in the combustion of
gasoline to settle on the surface of the injection valve thereof,
or which can easily remove the deposits attached thereon.
[0009] According to the feature of the invention, a fuel injection
valve suitable for use in a gasoline direct injection engine is
provided, which can prevent adhesion of the deposit produced in the
combustion of gasoline on the surface of the injection valve,
and/or easily remove the deposit adhered thereto.
[0010] A material of a deposit-resistant film on the surface of the
fuel injection valve suitable for use in a gasoline direct
injection engine must be such one which can stably exist on the
surface of the injection valve which is exposed to an environment
of 5-12 MPa of fuel pressure, 150-200.degree. C. of temperatures on
the surface of the valve under combustion of gasoline, and in
addition, which can provide a low surface energy as well as a
strong adhesion to the injection valve under such environment.
[0011] A surface modifying reagent for forming the
deposit-resistant film in order for the same to be used in the
aforementioned environment, must be essentially nonflammable
thereby limiting its materials to be used. An organic compound
which can withstand the above-mentioned environment is preferably a
perfluoro compound. This compound is most preferable as a material
which can provide for a low surface energy, and is also preferable
in the terms of oxidation stability, thermal stability and gasoline
resistant stability as well. However, because of its low surface
energy, the perfluoro compound has a weak adhesion with a
substrate. Hence, it becomes necessary to provide for a compound
which has a group to combine with the terminal of the perfluoro
compound which bonds with the substrate by reaction. Further, the
length of molecular chain in the fluoroalkyl compound used in the
prior art is as small as 1 nm or less, therefore, when the deposit
is pressed against the surface of the injection valve under the
fuel pressure of 5-12 MPa, the deposit is easily caused to pierce
through 1 nm thick film of perfluoroalkyl compound to get directly
in contact with the surface body to bond therewith. In order to
solve this problem, it is contemplated according to the invention
that if a thick film of a fluorine compound having a long chain is
provided, the adhesion of the deposit can be prevented. However,
because the number of carbon in the perfluoro alkyl compounds is
generally from 14 to 16 in maximum, it is difficult to synthesize
its compound having an increased polymerization.
[0012] Hence, we noted to use a polymer of a perfluoropolyether
compound as a candidate material which can be stably used in the
above-mentioned environment. This perfluoropolyether compound is an
average number of molecule weights from 2000 to 8000, and a shape
of the compound is looklike yarn ball of more than 1.5 nm in
average size (2.times.radius of molecule rotation). Then, if a
dense film of coating of a perfluoropolyether compound can be
formed, the surface of the fuel injection valve can be coated 1.5
nm thick or more in average. Because the surface of the yarn ball
of the above-mentioned perfluoropolyether compound is covered by
fluorine atoms, it has a low surface energy, thereby preventing
adhesion of the deposits, or facilitating peel-off of the deposits.
Further, when subjected to an external mechanical pressure, the
above-mentioned yarn ball is considered to function as a buffer
film. According to this effect, even if the deposit is pressed
against the surface of the fuel injection valve at pressures of
5-12 MPa of the fuel, the deposit is considered not to penetrate
through the coating of perfluoropolyether compound, thereby
preventing its adhesion on the surface of the injection valve. In
order for this perfluoropolyether compound to be strongly bonded on
the substrate, a most general method will be to provide for alkoxy
silane bonded to its terminal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] These and other objects, aspects and embodiments of the
present invention will be described in more detail with reference
to the following drawings, in which:
[0014] FIG. 1 is a schematic diagram of a gasoline direct injection
engine according to the invention;
[0015] FIG. 2 is a schematic diagram of a fuel injection valve
according to the invention;
[0016] FIG. 3 shows a relationship between operation times (h) and
fuel flow reduction rates (%) of the embodiments of the invention
treated by perfluoropolyether compounds;
[0017] FIG. 4 shows a relationship between concentrations and film
thicknesses of the perfluoropolyether compounds according to the
invention;
[0018] FIG. 5 is a diagram showing flow reduction rates of
respective fuel injection valves of embodiments of the invention
and comparison examples;
[0019] FIG. 6 is another diagram showing flow reduction rates of
respective fuel injection valves of embodiments of the invention
and comparison examples;
[0020] FIG. 7 is still another diagram showing flow reduction rates
of respective fuel injection valves of an embodiment of the
invention and a comparison example;
[0021] FIG. 8 is a diagram showing flow reduction rates of fuel
injection valves of another embodiment of the invention and a
comparison example;
[0022] FIG. 9 is a diagram showing flow reduction rates of fuel
injection valves of still another embodiment of the invention and a
comparison example;
[0023] FIG. 10 is a diagram showing flow reduction rates of fuel
injection valves of another embodiment of the invention and a
comparison example; and
[0024] FIG. 11 is a schematic diagram of a gasoline direct
injection engine according to another embodiment of the
invention.
DESCRIPTION OF NUMERALS
[0025] 1, 47 . . . fuel injection valve; 2 . . . fuel injection
valve drive circuit; 3, 48 . . . ignition plug; 4, 46 . . . intake
valve; 5, 50 . . . exhaust valve; 6 . . . intake port; 7 . . .
exhaust port; 8, 45 . . . piston; 9 . . . electronic control unit;
10 . . . cylinder head; 11 . . . injection valve drive signal
terminal; 12, 42 . . . three-way catalyst; 13 . . . NOx catalyst;
14 . . . combustion chamber; 22 . . . housing; 23 . . . core; 25 .
. . coil; 26 . . . armature; 27 . . . valve unit; 29 . . . valve
body; 31 . . . fuel injection port; 32 . . . valve sheet; 33 . . .
needle valve; 35 . . . swirler; 40 . . . throttle actuator; 49 . .
. intake flow sensor.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The present invention provides for a fuel injection valve
suitable for use in a gasoline direct injection engine, wherein the
surface of the fuel injection valve is coated by reaction-bonding
with a perfluoropolyether group compound having alkoxy silane at
its terminal, or with a perfluoropolyether compound which is
reaction-bonded via an adhesion promotion layer so as to provide
for a low surface energy to the fuel injection valve for the
gasoline direct injection engine, thereby preventing the deposit
from accumulating on the surface of the fuel injection valve or
easily removing the deposit having been attached therefrom.
[0027] Specific chain structures of such perfluoropolyether
compounds may include the following formulas such as KRYTOX
available from E.I. du Pont de Nemours & Co. (Inc.), DEMNUM
from DAIKIN INDUSTRIES, LTD., and FOMBLIN from AUSIMONT, LTD.
KRYTOX: F(CF(CF.sub.3)--CF.sub.2--O--).sub.n-- (Comp.3)
DEMNUM: F(CF.sub.2--CF.sub.2--CF.sub.2--O).sub.n-- (Comp.4)
FOMBLIN: F(CF.sub.2--CF.sub.2--O).sub.x(--CF.sub.2--O--)--.sub.y
(Comp.5)
or
-{(CF.sub.2--CF.sub.2--O--).sub.x--(--CF.sub.2--O--).sub.y--}--,
[0028] wherein n.gtoreq.12 (integer), x+y.gtoreq.28, and x/y=0.5 to
2.0.
[0029] Examples of structures of perfluoropolyether compounds, in
cases where their chain structures are of KRYTOX and DEMNUM groups,
include the following compounds 6 to 27.
F--(C.sub.3F.sub.6--O).sub.m--C.sub.2F.sub.4--CONH--C.sub.2H.sub.4--NH--C.-
sub.3H.sub.6--Si (CH.sub.3) (O--CH.sub.3).sub.2 (Comp. 6)
F--(C.sub.3F.sub.6--O).sub.m--C.sub.2F.sub.4--CONH--C.sub.2H.sub.4--NH--C.-
sub.3H.sub.6--Si(O--CH.sub.3).sub.3 (Comp. 7)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--CONH--C.sub.3H.sub.6--Si-
(O--C.sub.2H.sub.5).sub.3 (Comp. 8)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--COO--C.sub.3H.sub.6--O---
C.sub.3H.sub.6--Si (O--CH.sub.3).sub.3 (Comp. 9)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--COO--CH
(CH.sub.3)--CH.sub.2--O--C.sub.3H.sub.6--Si (O--CH.sub.3).sub.3
(Comp.10)
F--(--C.sub.3F.sub.6
--O--).sub.m--C.sub.2F.sub.4CH.sub.2--O--C.sub.3H.sub-
.6--O--C.sub.3H.sub.6--Si(O--CH.sub.3).sub.3 (Comp.11)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--COO--C.sub.3H.sub.6--O---
C.sub.3H.sub.6--Si(CH.sub.3) (O--CH.sub.3).sub.2 (Comp.12)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--CH.sub.2--O--CH(CH.sub.3-
)--CH.sub.2--O--C.sub.3H.sub.6--Si(CH.sub.3) (O--CH.sub.3).sub.2
(Comp.13)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--CH.sub.2--O--C.sub.3H.su-
b.6--Si(CH.sub.3) (O--CH.sub.3).sub.2 (Comp.14)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--CH.sub.2--O--C.sub.3H.su-
b.6--Si(O--CH.sub.3).sub.3 (Comp.15)
F--(--C.sub.3F.sub.6--O--).sub.m--C.sub.2F.sub.4--COO--C.sub.3H.sub.6--Si
(O--CH.sub.3).sub.3 (Comp.16)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)
CONH--C.sub.2H.sub.4--NH--C.sub.3H.sub.6--Si(CH.sub.3)(O--CH.sub.3).sub.2
(Comp.17)
F--(--CF (CF.sub.3)--CF.sub.2--O--).sub.n--CF
(CF.sub.3)--CONH--C.sub.2H.s-
ub.4--NH-C.sub.3H.sub.6--Si(O--CH.sub.3).sub.3 (Comp.18)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)--CONH--C.sub.3H.sub-
.6--Si (O--C.sub.2H.sub.5).sub.3 (Comp.19)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF
(CF.sub.3)--COO--C.sub.3H.sub-
.6--O--C.sub.3H.sub.6--Si(O--CH.sub.3).sub.3 (Comp.20)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)--COO--CH
(--CH.sub.3)--CH.sub.2--O--C.sub.3H.sub.6--Si(O--CH.sub.3).sub.3
(Comp.21)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)--CH.sub.2--O--C.sub-
.3H.sub.6--O--C.sub.3H.sub.6--Si(O--CH.sub.3).sub.3 (Comp.22)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)--COO--C.sub.3H.sub.-
6--O--C.sub.3H.sub.6--Si(CH.sub.3)(O--CH.sub.3).sub.2 (Comp.23)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)--CH.sub.2--O--CH(CH-
.sub.3)--CH.sub.2--O--C.sub.3H.sub.6--Si(CH.sub.3)(O--CH.sub.3).sub.2
(Comp.24)
F--(--CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)--CH.sub.2--O--C.sub-
.3H.sub.6--Si(CH.sub.3)(O--CH.sub.3).sub.2 (Comp.25)
F--(--CF(CF.sub.3)--CF.sub.2--O--)--CF(CF.sub.3)--CH.sub.2--O--C.sub.3H.su-
b.6--Si(O--CH.sub.3).sub.3 (Comp.26)
F--(--CF(CF.sub.3)--CF.sub.2--O--)--CF(CF.sub.3)--COO--C.sub.3H.sub.6--Si
(O--CH.sub.3).sub.3 (Comp.27)
[0030] where, m=14 in average, and n=24 in average.
[0031] Specific examples of the perfluoropolyether compounds in
case their chain structures are of FOMBLIN include the following
structures.
[0032]
A--CF.sub.2--{--(--CF.sub.2--CF.sub.2--O--).sub.x--(CF.sub.2--O--).-
sub.y--}--CF.sub.2--A (Comp.28)
B--CF.sub.2--{--(--CF.sub.2--CF.sub.2--O--).sub.x--(CF.sub.2--O--).sub.y---
}--CF.sub.2--B (Comp.29)
[0033] wherein, A is
--CONH--CH.sub.2CH.sub.2CH.sub.2--Si--(--OCH.sub.2CH.-
sub.3).sub.3, B is --CH.sub.2O
--CH.sub.2CH.sub.2CH.sub.2--Si--(--OCH.sub.- 3).sub.3, x=21 in
average, and y=27 in average.
KRYTOX group:
F(CF(CF.sub.3)--CF.sub.2--O--).sub.n--CF(CF.sub.3)--Z--B,
DEMNUM group:
F(CF.sub.2--CF.sub.2--CF.sub.2--O).sub.n--CF.sub.2--CF.sub.2-
--Z--B,
FOMBLIN group:
B--Z--C.sub.2F.sub.4--O--{(CF.sub.2--CF.sub.2--O).sub.x--(C-
F.sub.2--O).sub.y}--C.sub.2F.sub.4--Z--B,
[0034] wherein n is an integer equal to 11 or greater,
x+y.gtoreq.18, x/y=0.5 to 2.0, Z is a connection group which
includes an alkylane or amino group which contains at least one of
amide, ester and methylenoxide. B is remaining group of alkoxy
silane.
[0035] Examples of structures of perfluoropolyether compounds in
case their chain structures have a KRYTOX and a DEMNUM group
include the following compounds.
F(--CF.sub.2--CF.sub.2--CF.sub.2--O--)--C.sub.2F.sub.4--CONH--C.sub.3H.sub-
.6--Si (CH.sub.3)(O--CH.sub.3).sub.2 (Comp. 33)
F(--CF(CF.sub.3)--CF.sub.2--O--)--CF(CF.sub.3)--CONH--C.sub.2H.sub.4--NH---
C.sub.3H.sub.6--Si(CH.sub.3)(O--CH.sub.3).sub.2 (Comp. 34)
F(--CF(CF.sub.3)--CF.sub.2--O--)--CF(CF.sub.3)--CONH--C.sub.2H.sub.4--NH---
C.sub.3H.sub.6--Si(O--CH.sub.3).sub.3 (Comp. 35)
F(--CF(CF.sub.3)--CF.sub.2--O--).sub.p--CF(CF.sub.3)--CONH--C.sub.3H.sub.6-
--Si(O--C.sub.2H.sub.5).sub.3 (Comp. 36).
[0036] Examples of structures of perfluoropolyether compounds in
case their chain length structures have a FOMBLIN group include the
following structures 37 to 40.
C--C.sub.2F.sub.4--O--{(CF.sub.2--CF.sub.2--O).sub.x--(CF.sub.2--O).sub.y}-
--C.sub.2F.sub.4--C (Comp.37)
D--C.sub.2F.sub.4--O--{(CF.sub.2--CF.sub.2--O).sub.x--(CF.sub.2--O).sub.y}-
--C.sub.2F.sub.4--D (Comp. 38)
C--C.sub.2F.sub.4--O--{(CF.sub.2--CF.sub.2--O).sub.j--(CF.sub.2--O).sub.k}
--C.sub.2F.sub.4--C (Comp. 39)
D--C.sub.2F.sub.4--O--{(CF.sub.2--CF.sub.2--O).sub.j--(CF.sub.2--O).sub.k}-
--C.sub.2F.sub.4--D (Comp. 40)
[0037] where, C is
--CONH--CH.sub.2CH.sub.2CH.sub.2--Si(--OCH.sub.2CH.sub.- 3).sub.3,
D is --CH.sub.2O--CH.sub.2CH.sub.2CH.sub.2--Si(--OCH.sub.3).sub.-
3x=21 in average, y=27 in average, j=8 in average, and k=10 in
average.
[0038] All of the perfluoropolyether compounds shown in compounds 6
to 40 dissolve in perfluorohexane or perfluorobutylmethylether
which is a kind of solvent having some fluorine atoms. The solvent
is expressed as fluorine solvent in this paper. In order to form a
film of either one of the above-mentioned perfluoropolyether
compounds on the surface of the fuel injection valve, the fuel
injection valve is immersed into a solution having the
perfluoropolyether compounds dissolved into the fluorine solvent
such as perfluorohexane or perfluoromethylether or the like.
Alternatively, the solution is dripped on the nozzle portion of the
fuel injection valve. Then, they are heated at 150.degree. C. for
10 minutes. By heat treatment described above, alkoxysilane which
is at the terminal group of perfluoropolyether compounds 6 to 40 is
caused to react with a hydroxyl group present on the surface of the
fuel injection valve to bind together. By a simple process as
described above, a reaction film of the perfluoropolyether compound
can be formed on the surface of the fuel injection valve according
to the invention. A thickness of a film to be formed thereon
depends on a molecular weight and a concentration of coating of the
perfluoropolyether compounds. Thermal stabilities and oxidation
stabilities of respective reaction films obtained as above are
found to have been improved. However, compounds 9, 10, 12, 16, 20,
21, 23 and 27 wherein their binding group is ester are slightly
inferior in these stabilities compared with the other
perfluoropolyether compounds of the invention.
[0039] A most preferable method for stably bonding the
perfluoropolyether compounds 6 to 40 on the surface of the
substrate is to use alkoxy silane as a reaction group. However, it
is not limited thereto, and alkoxy titanium or akloxy zirconium may
be used as well.
[0040] When there does not exist an adequate oxide film which
provides for a reaction site with respect to compounds 6-40 on the
surface of the fuel injection valve for the gasoline direct
injection engine, it is necessary to provide for an organic polymer
film or oxide film as a bonding (or binding) acceleration
(promotion) layer. This bonding acceleration layer is required to
have such properties as to be able easily to form a hydrate at its
reaction site on the surface, to have a strong adhesion with the
surface of the fuel injection valve, and to be ensured to exist
stably at 5-12 MPa of fuel pressures, at 150-200.degree. C. on the
surface of the fuel injection valve, and in a stringent environment
of gasoline combustion. As organic polymeric films that can be used
enduring such stringent environments, there are a thermo-set film
of a ladder type silicone group origomer, an epoxy resin cured film
and the like. As oxide films, there are SiO.sub.2, Al.sub.2O.sub.3,
TiO.sub.2 or the like. On either one of these bonding accelerators
provided as above, perfluoropolyether compound 6-40 is
reaction-bonded firmly so as to accomplish the fuel injection valve
which can eliminate the accumulation of deposits according to the
invention. It should be noted, however, that when the thickness of
the bonding acceleration film increases excessively, a strain is
caused to occur between the fuel injection valve and the bonding
acceleration film due to a difference in their thermal expansion
coefficients, thereby resulting in a peel-off of the bonding
accelerator film. Therefore, the thickness of the bonding
accelerator film is preferably as thin as possible.
[0041] Specific examples of the ladder type silicone group
oligomers used as the bonding accelerator include glass resin
GR100, GR650, GR908, GR950 available from SHOWA DENKO, LTD.
Well-known examples of such epoxy resins include Epicoat Series of
Yuka Shell Epoxy KK, XD9053 of Dow Chemical Japan KK, and the like.
As oxide films for the bonding acceleration, a baked film of
various metal alkoxides, aluminum chelte reagents and the like are
used. Specific examples of metal alkoxides include
tetraethoxysilane (SHINETSU KAGAKU KOGYO K.K.: KBE04),
tetromethoxysilane (SHINETSU KAGAKU KOGYO K.K.: KBM04),
tetraethoxytitane (DINAMITE NOBEL JAPAN K.K.: ET),
tetramethoxytitan (DINAMITE NOBEL JAPAN K.K.: MT), tetrapthoxytitan
(DINAMITE NOBEL JAPAN K.K.: BT) and the like. As the alminum
chelete reagent, there is alminum chelete A available from Kawa-Ken
Fine Chemical K.K.
[0042] A fuel injection valve according to one aspect of the
invention is provided with at least one of the following features
that an organic film of a 1.5 nm to 8 nm thickness is provided on
the port and in the vicinity of the fuel injection port, or on the
surface of the fuel injection valve, that the fuel injection valve
has an opening from 0.3 mm to 0.8 mm diameter capable of atomizing
fuel into particles in less than 20 .mu.m in diameter, and that the
fuel injection valve port and its vicinity are manufactured using a
ferrite stainless steel comprising of C from 0.6 to 1.5%, Si less
than 1%, Mn less than 1.5%, and Cr from 15 to 20% by weight. The
organic film which is comprised of any one of the above-mentioned
compounds is bonded with its base metal by covalent binding, the
thickness of which film is preferably 1.5-30 nm, more preferably
1.5-10 nm, and the most preferably 1.5-7 nm.
[0043] Further, as the organic film may be formed of using
tetrafluoride-ethylene monomer by glow discharge. Other candidates
of the organic film are Teflon resin, or a solution of metal
alkoxide and fluoroalkyl group substituted alkoxide, and the
like.
[0044] According to another aspect of the invention, a gasoline
direct injection engine is provided, which is comprised of a
cylinder head having air intake means and exhaust means connected
to the combustion chamber, a piston reciprocating within the
cylinder, fuel injection means for injecting fuel into the
combustion chamber, and ignition means for igniting atomized fuel,
and wherein said fuel injection means is comprised of the
above-mentioned fuel injection valve.
[0045] According to still another aspect of the invention, a
gasoline direct injection engine is provided, wherein the same is
comprised of a cylinder head having air intake means and exhaust
means connected to the combustion chamber, a piston reciprocating
within the cylinder, fuel injection means for injecting fuel into
the combustion chamber, and ignition means for igniting atomized
fuel, and wherein the surfaces of an injection port and its
vicinity of said fuel injection are coated with an organic
film.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] Embodiment 1
[0047] FIG. 1 shows a gasoline direct injection type internal
combustion engine for automobile according to one embodiment of the
invention. A fuel injection valve 1 which is mounted on a cylinder
head 10 has an opening at its end portion for directly injecting
fuel supplied from a fuel gallery into a combustion chamber 14.
[0048] An ignition plug 3 which is provided between an intake valve
4 and an exhaust valve 5 ignites a mixture of air and fuel to start
combustion, the air being supplied from intake port 6 and through
intake valve 4 by moving of piston 8, and the fuel injected from
injection valve 1. An exhaust gas after combustion is exhausted
through exhaust valve 5 by moving of piston 8 while it is open.
[0049] An injection valve moving signal terminal 11 of fuel
injection valve 1 is electrically connected to a fuel injection
valve moving circuit 2. Further, the fuel injection valve moving
circuit 2 is electrically connected to an electronic control unit
(ECU) 9 which emits a fuel injection valve moving trigger signal
and a signal whether or not to move the fuel injection valve in
such a manner as to minimize an operation delay of the valve body.
By way of example, ECU 9, which is supplied with data representing
various operational conditions of the engine, determines a fuel
injection valve moving trigger signal in response to the
operational conditions.
[0050] An air flow from intake port 6 is controlled by
electromagnetic means M which is provided dually and operates with
the motion of an accelerator pedal. Hydrocarbon, carbon monoxide,
and NOx, which are included in the exhaust gas after combustion,
are removed by a low oxygen storage type three-way catalyst 12 and
a lean NOx catalyst 13. In this embodiment 1 of the invention, a
particle size of atomized fuel injected from the fuel injection
valve 1 is less than 25 .mu.m, preferably less than 15 .mu.m, and
more preferably less than 10 .mu.m, and whereby a super lean-burn
with an air fuel ratio of 50 is realized. In the three-way catalyst
12, Pt or Ce is supported by alumina supports. In NOx catalyst 13,
Pt is supported by alumina supports, or oxides of Na, Ti are
supported therein.
[0051] With reference to FIG. 2, a schematic view of a
cross-section of fuel injection valve 1 of the invention is shown,
which is mounted in the cylinder head 10. In FIG. 2, numeral 22
depicts a housing; 23 depicts a core; 25 a coil; 26 an armature; 27
a valve unit; wherein valve unit 27 is supported by one end of the
housing 22 by caulked joint. Further, valve unit 27 is comprised
of: a valve body 29 which is a step-wise hollow cylinder having a
minor diameter cylinder portion and a major diameter cylinder
portion; a valve sheet 32 which is firmly fixed to the end of a
center port inside the valve body 29, and has a fuel injection port
31; and a needle valve 33 which is operated by a solenoid device to
contact and separate from valve sheet 32 to open and close fuel
injection port 31. Numeral 34 indicates a space in contact with a
bottom surface of the coil assembly and surrounded by the housing
and the core, which more specifically corresponds to a pair of
O-rings disposed on the side of fuel pressure application. Numeral
35 depicts a swirler. A diameter of the fuel injection valve port
31 is 0.8 mm.
[0052] Now, the operation of the fuel injection valve will be
described. When coil 25 is given an electronic signal, a magnetic
flux is produced in the magnetic circuit including armature 26,
core 23 and housing 22, whereby armature 26 is attracted toward
core 23, thereby separating needle valve 33 which is integral with
armature 26 from valve sheet 32 so as to provide for a gap
therebetween. Then, a pressurized fuel is guided from valve body 29
through the gap into injection port 31 in the valve sheet 32 so as
to be injected therefrom as atomized particles as described
above.
[0053] Further, the fuel injection valve 1 is mounted so as to
protrude into the cylinder as much as 2-10 mm.
[0054] In particular, valve body 29, valve sheet 32, needle valve
33 and swirler 35 are manufactured using 1 wt % of C and 16 wt % of
Cr containing ferrite stainless steel of JIS Standard SUS44C, which
is cold-processed, annealed, and machined into final shapes. The
diameter of injection valve port 31 is 0.8 mm, and a roundness at
its minor diameter is less than 0.5 .mu.m.
[0055] A method for forming a coating of perfluoropolyether
compounds at the end portion of fuel injection valve 1, and its
effect and advantage will be described in the following.
[0056] Perfluoropolyether compounds such as Compound 8 having
numerical average molecular weight of 2690, Compound 19 having
numerical average molecular weight of 2190, Compound 39 having
numerical average molecular weight of 2302 are dissolved in
perfluorohexane of FC-72 (Trade name; Sumitomo 3M K.K.) to produce
a solution of 0.2 wt % concentration. The nozzle end portion of the
fuel injection valve of FIG. 2 is immersed into this solution for
one hour. Then, the fuel injection valve taken out from the
solution is heated at 150.degree. C. for 10 minutes. By this heat
treatment, alkoxy silane which is a terminal functional group of
perfluoropolyether compounds of Compounds 8, 19, 37 is caused to
have a dehydration reaction with a hydroxyl group on the surface of
the fuel injection valve, whereby the both of them undergo a
covalence binding to form a highly adhesive coating approximately
of 2 nm thickness. This coating is provided on the whole area of
the internal surface of swirler 35, the whole area of needle valve
33 corresponding to the swirler, on the valve sheet 32, on the fuel
injection port 31, and on the valve body 29 corresponding to the
part of the swirler. The fuel injection valves after treatment by
the perfluoropolyether compounds of 8, 19 and 37 are mounted on a
test engine to observe accumulation of deposits. Gasoline flow
reduction rates are measured as an index of a quantity of deposits.
The test engine used is a gasoline direct injection four-cycle,
V-type/6 cylinder engine (Nissan Motors). Water of 80.degree. C. is
circulated in the engine head to keep the temperature of the engine
head at 90-110.degree. C. Test were conducted at engine rotation of
1200 rpm, fuel flow rate at 2200 cc/h and for 40 hours of
operation.
[0057] In reference to FIG. 3, a relationship between the operation
time and the decrease in the fuel flow rate is shown for respective
cases of the fuel injection valve where its surface is treated by
perfluoropolyether compounds 8, 19 and 37, respectively. Comparison
examples shown here include non-treated one the surface of which is
not treated with any perfluoropolyether compound, and those which
are treated with the following fluoroalkyl compounds 41 and 42 in
0.2 wt % concentration, respectively.
C.sub.6F.sub.13--C.sub.2H.sub.4--Si(O--C.sub.2H.sub.5).sub.3
(molecular weight: 510) (Comp. 41),
CF.sub.3--C.sub.2H.sub.4--Si(OCH.sub.3).sub.3 (molecular weight:
218) (Comp. 42).
[0058] With reference to FIG. 3, in respective cases where the
surfaces are treated with compounds 8, 19 or 37 respectively, their
fuel flow decreasing rates are suppressed to be less than 2%, which
is substantially smaller than the cases treated with comparison
examples 41, 42 and the non-treated one. This result reveals that
when the surface is treated with the perfluoropolyether compounds,
a flow resistance due to accumulation of deposits becomes
substantially small, thereby showing an excellent effect to prevent
accumulation of the deposits.
[0059] EMBODIMENT 2
[0060] Solutions of respective perfluoropolyether compounds 8 with
numeral average molecule weight of 2690, 19 with numeral average
molecule weight of 2190 and 37 with numeral average molecule weight
of 4880 are prepared by dissolving these compounds into
perfluorohexane of FC-72 (Trade name: Sumitomo 3M K.K.) in 0.01,
0.05, 0.075, 0.1 and 0.2 wt % concentrations, respectively. Into
these solutions, the nozzle portion of the fuel injection valve
shown in FIG. 2 is immersed for one hour. Then, the valve hauling
up from the solution is heated at 150.degree. C. for ten minutes.
Through such heat treatment, alkoxy silane which is the terminal
functional group of the perfluoropolyether compounds 8, 19 and 37
is caused to have a dehydration reaction with the hydroxyl group
present on the surface of the fuel injection valve, whereby both of
them are allowed to have a covalence binding to form a coating film
of approximately 2 nm thick. The thickness of the films of the
perfluoropolyether compounds firmly coated on the surface of the
fuel injection valve was measured by the reflection adsorption
spectroscopy (RAS) method using an infrared spectroscopy 1720 of
Perkin-Elmer. In the measurement of thickness, spectra of 1250-1275
cm.sub.-1 in stretching vibration of C--F which is the main
structure of perfluoropolyether were used, and its absorption was
converted to a film thickness. The film thickness was calibrated
using ellipsometry. A relationship between concentrations of
coating and film thicknesses for each of the perfluoropolyether
compounds 8, 19 and 37 is shown in FIG. 4. Reaction-bonded film
thicknesses of the perfluoropolyether compounds 8, 19 and 37 were
in the range of 0.8 nm to 6.2 nm. A fuel injection valve treated
with perfluoropolyether compound 8 was mounted on the test engine,
and its deposit accumulation condition was observed. A gasoline
flow reduction was measured as an index of a quantity of
accumulation of deposits. The test engine used was a direct
injection 4-cycle, V-type/6 cylinder engine manufactured by Nissan
Motor Co., and the temperature of its engine head was controlled at
90-110.degree. C. by circulating water of 80.degree. C. in the
engine head. The test was done at 1200 rpm, with a fuel flow of
2200 cc/h, and for 40 hours of operation.
[0061] With reference to FIG. 5, decreases in fuel flow rates
relative to times of operation are shown for respective cases where
the perfluoropolyether compound 8 was coated on the surface in
0.01, 0.05, 0.075, 0.1 and 0.2 wt % concentrations, respectively.
Film thicknesses coated were 1.0, 1.3, 1.5, 2.0 and 3.7 nm,
respectively, and each contact angle for water is more than 100
degrees. Comparison examples used include non-treated one the
surface of which was not treated with any perfluoropolyether
compound, and another one the surface of which was coated with the
fluoroalkyl compound of 41 in 0.2 wt % concentration. Film
thickness measurements of the fluoroalkyl compound were conducted
using the infrared spectroscopy type 1720 of Perkin-Elmer, and by
the reflection adsorption spectroscopy (RAS) method. In this
measurements, spectra of 1200 cm.sub.-1 in the stretching vibration
of C--F which is the main structure of the fluoroalkyl compound
were used, and its film thickness was obtained by conversion from
its absorption. The film thickness was calibrated using the
ellipsometry. The thickness of compound 41 treated was 2.3 nm.
[0062] It is known from FIG. 5 that in the case where the surface
is treated with compound 8 to have a film thickness of 1.5 nm or
more, a decrease in its fuel flow rate is suppressed to be less
than 2%, which is substantially smaller than the cases where the
surface is treated with comparison compound 41 in a film thickness
of 2.3 nm, and the non-treated example. This result reveals that
when the surface is treated with the perfluoropolyether compound 8
to have the film thickness more than 1.5 nm, any substantial flow
resistance due to accumulation of the deposits does not occur
thereby proving its excellent advantage and effect to be able to
prevent deposition of the deposits. Further, observation of deposit
accumulation after 40 hours of operation on the injection port 3 of
the fuel injection valve which was treated with the
perfluoropolyether compound of the invention in the thickness more
than 1.5 nm revealed that its deposit accumulation was remarkably
smaller compared with the comparison examples.
EMBODIMENT 3
[0063] Perfluoropolyether compounds of the invention: compound 8
with numeral average molecular weight of 2690; compound 19 with
numeral average molecular weight of 2190; compound 37 with numeral
average molecular weight of 4880;
[0064] and compound 38 with numeral average molecular weight of
4820, are dissolved respectively into perfluorobutylmethylether
HFE7100 (Trade name: Sumitomo 3M K.K.) to prepare a solution
thereof in 0.2 wt % concentration. In the same manner as with the
Embodiment 1, a fuel injection valve as shown in FIG. 2 is immersed
in this solution for one hour so as to form a coating comprising
the perfluoropolyether compound of the invention on the surfaces of
the fuel injection valve and the injection port. Then, the fuel
injection valve unit is hauled up from the solution, and heated at
150.degree. C. for ten minutes. A film thickness of the
perfluoropolyether compound which is reaction-bonded on the fuel
injection valve was measured using the infrared spectroscopy 1720
type from Perkin-Elmer, and by the RAS method. Spectra of 1250-1270
cm.sup.-1 in the stretching vibration of C--F which is the main
composition of the perfluoropolyether were used in the
measurements, and its film thickness is obtained by conversion from
its absorption. The film thickness is calibrated using the
elliptometry. Film thicknesses reaction-bonded on the surface of
the fuel injection valve are 3.6 nm for the compound 8, 3.2 nm for
the compound 19, 5.8 nm for the compound 37, and 5.9 nm for the
compound 38, respectively. Contact angles for water are more than
100 degrees, respectively.
[0065] In addition, comparison examples were prepared using the
following fluoroalkyl compounds of compounds 41-46, as well as
perfluoropolyether compounds of compounds 45, 46, which are
dissolved into perfluorobutylmethylether HFE7100 (Trade Name of
Sumitomo 3M K.K.) to produce each solution thereof in 0.5 wt %
concentration. Into this solution, the nozzle end portion of a fuel
injection valve as shown in FIG. 2 is immersed for one hour. Then,
the same is hauled up from the solution, and heated at 150.degree.
C. for ten minutes. In this manner the coating thereof is
reaction-bonded on the fuel injection valve. Molecular weights of
compounds 41-46 are 510, 218, 390, 610, 1860 and 1530,
respectively. Film thicknesses of reaction-bonded compounds bound
on the surface of the fuel injection valve are 18.9 nm with
compound 41, 38.2 nm with compound 42, 32.8 nm with compound 43,
10.8 nm with compound 44, 42.6 nm with compound 45, and 40.2 nm
with compound 46, respectively. Contact angles for water were more
than 100 degrees for all cases.
1 Compound 43: (CF.sub.3).sub.2CFO--C.sub.3H.sub.6--Si(OC.s-
ub.2H.sub.5).sub.3 (molecular weight: 390) Compound 44:
F(CF.sub.2).sub.8--C.sub.2H.sub.4--Si(OC.sub.2H.sub.5).sub.3
(molecular weight: 610) Compound 45: F(--CF.sub.2--CF.sub.2--CF.su-
b.2--O--).sub.m--C.sub.2F.sub.4--CONH--C.sub.3H.sub.6--
Si(OC.sub.2H.sub.5).sub.3 (m = 9 in average) (average molecular
weight: 1860) Compound 46: F(--CF(CF.sub.3)--CF.sub.2O---
).sub.m--CF(CF.sub.3)--CONH
--C.sub.3H.sub.6--Si(O--C.sub.2H.sub.5)- .sub.3 (m = 7 in average)
(average molecular weight: 1530).
[0066] The fuel injection valves the surface of which are treated
with either of the perfluoropolyether compounds of 8, 19, 37 and
38, the fluoroalkyl compounds of 41-44, and the perfluoropolyether
compounds of 45 and 46 according to the invention were mounted on
the test engine to observe the state of accumulation of the
deposits and to measure respective decreases in the fuel flow rates
as indices representing a quantity of the deposits accumulated. The
test engine used is a direct injection 4-cycle, V-type/6-cylinder
engine manufactured by Nissan Motors Co. Water is circulated at
80.degree. C. through the engine head to keep the temperature of
the engine head at 90-110.degree. C. The test was done at 1200 rpm,
and the fuel flow rate at 2200 cc/h. The test duration time was set
for 140 hours.
[0067] With reference to FIG. 6, when the perfluoropolyether
compound having numeral average molecular weight greater than 2190
is reaction-bonded on the surface in a thickness of 2.3 nm or more,
the decrease in the fuel flow rate is confirmed to be suppressed
less than 2%, which is remarkably smaller than the cases where the
surface is treated with the fluoroalkyl compounds of the comparison
examples having molecular weights of 218-610 with 10.8-38.2 nm
thickness. Further, in the case of the perfluoropolyether compounds
having a molecular weight less than 1860, even if its film
thickness is thick as 40.2 or 42.6 nm, the decrease in the flow
rate due to occurrence of the deposits is observed to become 3-5%.
Although its effect is recognized, the effect is not sufficient. It
is concluded from the result of the tests that in the case where
the perfluoropolyether compound having a numeral average molecular
weight greater than 2190 is used, a film thickness of 1.5 nm or
more can adequately prevent accumulation of the deposits, however,
that in the case where the fluoroalkyl compound with a smaller
molecular weight is used, even if its film thickness is given
sufficiently thick, a substantial occurrence of the deposits cannot
be prevented. Further, with the perfluoropolyether compounds having
molecular weights of 1530 and 1860, a sufficient effect could not
have been obtained.
[0068] EMBODIMENT 4
[0069] A solution of glass resin GR100 manufactured by Showa-Denko
Co. is prepared by dissolving the same into methyl ethyl keton in
0.02 wt % concentration. Into this solution, a fuel injection valve
the leading end of which is chrome-plated is immersed so as to coat
the surfaces of the fuel injection valve and the injection port
with glass resin GR100. Then, the fuel injection valve is hauled up
from the solution, heated at 200.degree. C. for 30 minutes, thereby
baking the coating of glass resin GR100 on the surfaces of the fuel
injection valve and its injection port. Then, compound 6 having a
molecular weight of 2670 is dissolved into
perfluorobutylmethylether HFE7100 (Trade Name of Sumitomo 3M K.K.)
to produce a solution thereof with 0.2wt % concentration. The
above-mentioned fuel injection valve which is baked on its surface
with the coating of glass resin GR100 is immersed into this
solution for one hour. Then, the fuel injection valve, after
hauling up from the solution is heated at 150.degree. C. for ten
minutes. In this manner, thin layers of glass resin GR100 and the
compound 6 are formed on the surfaces of the fuel injection valve
and its internal injection port. A film thickness of the compound 6
was 3.2 nm and a contact angle for water on the surface of the fuel
injection valve was greater than 100 degrees.
[0070] As a comparison example, a fuel injection valve the end
portion of which is chrome-plated is immersed in the solution of
compound 6 with 0.2 wt % concentration thereof (solvent used:
perfluorobutylmethylether HFE7100 (trade name of Sumitomo 3M K.K.))
for one hour, after hauling up from the solution, heated at
150.degree. C. for ten minutes. A film thickness of the comparison
example using compound 6 was measured using the RAS method to be
1.1 nm thick. A contact angle for water is less than 100 degrees.
This fuel injection valve was mounted on the test engine, and a
state of accumulation of the deposits thereon was observed, and
measurements of the decreases in the fuel flow rates as an index
which represents a quantity of deposits were conducted. The engine
used for evaluation of the state of accumulation of the deposits is
the direct injection 4-cycle, V-type/6-cylinder engine manufactured
by Nissan Motors Co. Water is circulated through the engine head at
80.degree. C. to maintain the temperature of the engine head from
90-110.degree. C. The tests were done at 1200 rpm, 2200 cc/h of a
fuel flow rate, and for 140 hours of operation.
[0071] In reference to FIG. 7, the fuel injection valve the end
portion of which is chrome-plated, and coated with both the layers
of glass resin GR100 and compound 6 in combination features a
thicker film layer of compound 6 compared with the comparison
example the end portion of which is chrome-plated and coated with
the layer of compound 6 alone, and a remarkably smaller decrease in
the flow reduction rates. From this result, it is concluded that
the organic polymeric layer of glass resin GR100 is very effective
as the bonding acceleration layer.
[0072] EMBODIMENT 5
[0073] A solution [A] is prepared by dissolving 0.44 g of epoxy
resin EP1004 (Yuka Shell Epoxy K.K.), 0.30 g of Malkalineka-M
(Maruzen-Sekiyu-Kagaku K.K.) which is poly-p-hydroxy-styrene resin,
and 0.004 g of triethylammoniumborate TEA-K (Hokko-kagagu K.K.)
which is a hardening accelerator, into a mixture solvent of 95 g of
methyl ethyl keton and 5 g of 2-butoxyethyl acetate. A fuel
injection valve the end portion of which is chrome-plated is
immersed in this solution [A] to provide for a coating of solution
[A] on the surface of the fuel injection valve and on the internal
wall of the injection port thereof. Then, the fuel injection valve
is hauled up from the solution, heated at 200.degree. C. for 30
minutes, so as to bake the layer of film comprising solution [A] on
the surface of the injection valve and on the internal wall of the
injection port thereof. Nextly, a solution of compound 6 having a
molecular weight of 2670 is prepared by dissolving into
perfluorobutylmethylether HFE7100 (Sumitomo 3M K.K.) with 0.2 wt %
concentration thereof. Into this solution, the above-mentioned fuel
injection valve the end portion of which is baked with the coating
comprising solution [A] is immersed for one hour. Then, the fuel
injection valve after hauling up from the solution is heated at
150.degree. C. for ten minutes. In this way, thin layers of coating
of glass resin GR100 and compound 6 are formed on the surface of
the fuel injection valve and on the internal wall of the injection
port thereof. A film thickness of compound 6 was 3.5 nm, and a
contact angle for water on the surface of the fuel injection valve
was more than 100 degrees.
[0074] A comparison example was prepared by immersing a fuel
injection valve the leading edge portion of which was chrome-plated
into a solution of compound 6 with 0.2 wt % concentration (solvent:
perfluorobutylmethylether HFE7100 (Sumitomo 3M K.K.)) for one hour,
then the same was hauled up from the solution, heated at
150.degree. C. for ten minutes. A film thickness of compound 6 for
the comparison example was measured using the RAS method to be 1.0
nm thick. Its contact angle for water is less than 100 degrees.
This fuel injection valve was mounted on the test engine, and
conditions of accumulation of deposits were observed, and decreases
in the fuel flow rates, which are indices indicative of a quantity
of accumulation of the deposits were measured. The test engine used
in the evaluation of accumulation of the deposits is the direct
injection 4-cycle, V-type 6-cylinder engine manufactured by Nissan
Motors Co. Water is circulated through the engine head at
80.degree. C. to keep the temperature of the engine head at
90-110.degree. C. The tests were done at 1200 rpm, at 2200cc/h of
fuel flow rate, and for 140 hours of operation.
[0075] As clearly shown in FIG. 8, the fuel injection valve the
leading portion of which was chrome-plated, and coated with both
layers of solution [A] and compound 6 is characterized by having a
thicker coating of compound 6 and having an extremely smaller
decrease in the flow reduction rates compared with another fuel
injection valve which is chrome-plated and coated with compound 6
alone. From this result, it is concluded that the organic polymer
layer of the invention is very effective as the bonding
acceleration layer.
[0076] EMBODIMENT 6
[0077] A solution of tetraethoxy silane KBE04 (Shinetsu
Kagagu-kogyo K.K.) of 0.05 wt % concentration was prepared by
dissolving into methanol. Into this solution, a fuel injection
nozzle the leading edge of which was chrome-plated was immersed.
After hauling up from the solution, the fuel injection valve was
heated at 250.degree. C. for one hour to form a SiO.sub.2 film on
the surface of the fuel injection valve. Nextly, a solution of
compound 26 with molecular weight of 4280 and of 0.2 wt %
concentration was prepared by dissolving the same into
perfluorobutylmethylether HFE7100 (Trade Name of Sumitomo 3M K.K.).
The above-mentioned fuel injection valve on the surface of which
the SiO.sub.2 film was formed was immersed into this solution of
compound 26 for one hour. Then, after taking out of the solution,
the fuel injection valve is heated at 150.degree. C. for ten
minutes. In this way, thin films of oxides of tetraethoxy silane
and of compound 26 were formed on the surface of the fuel injection
valve and on the internal wall of the injection port thereof. A
film thickness of compound 26 was measured using the RAS method to
be 2.8 nm. A contact angle for water was greater than 100
degrees.
[0078] A comparison example was prepared by immersing a fuel
injection valve, the leading edge of which was chrome-plated, into
a solution of compound 26 of 0.2 wt % concentration (which uses a
solvent of perfluorobutylmethylether HFE7100 of Sumitomo 3M K.K.)
for one hour, then the fuel injection valve having been hauled up
from the solution was heated at 150.degree. C. for ten minutes. A
film thickness of compound 26 of the comparison example was
measured by the RAS method and found out to be 0.9 nm. A contact
angle for water was less than 100 degrees. This fuel injection
valve was mounted on the test engine to monitor the condition of
accumulation of deposits and to measure a decrease in the gasoline
flow rate as an index representing a quantity of deposits thereon.
The test engine used was a direct injection 4-cycle, V-type
6-cylinder engine manufactured by Nissan Motors Co. By circulating
water at 80.degree. C. through the engine head, the temperature of
the engine head was controlled at 90-110.degree. C. The tests were
done at 1200 rpm, 2200 cc/h of fuel flow, and for 140 hours of
operation.
[0079] As clearly shown in FIG. 9, the fuel injection valve the
leading edge portion of which was chrome-plated and coated by
layers of both the tetraethoxy silane oxide and the compound 26 has
a thicker film of compound 26 compared to the comparison fuel
injection valve the edge portion of which was chrome-plated and
coated by compound 26 alone, and thereby having a remarkably
smaller decrease in the flow rate. From this result, it is
concluded that the oxide film of the invention is very effective as
the bonding acceleration layer.
[0080] EMBODIMENT 7
[0081] A solution of aluminum chelete A (Kawaken Fine Chemical
K.K.) of 0.05 wt % concentration was prepared by dissolving into
methanol. Into this solution, a fuel injection valve the edge
portion of which was chrome-plated is immersed. After hauling up
from the solution, this fuel injection valve is heated at
250.degree. C. for one hour to form a film of Al.sub.2O.sub.3 on
the surface thereof. Then, a solution of compound 37 with molecular
weight of 4880 and in 0.2 wt % concentration is prepared by
dissolving into perfluorobutylmethylether HFE7100 (Trade Name of
Sumitomo 3M K.K.). Into this solution, the above-mentioned fuel
injection valve coated with Al.sub.2O.sub.3 on the surface thereof
is immersed for one hour. Then, after hauling up from the solution,
the fuel injection valve is heated at 150.degree. C. for ten
minutes. In this way, both layers of a thin Al.sub.2O.sub.3 film
and compound 37 are formed on the surface of the fuel injection
valve and on the internal wall of the injection port thereof. A
film thickness of compound 37 was measured using the RAS method and
found out to be 3.2 nm thick. A contact angle for water was greater
than 100 degrees.
[0082] A comparison example is prepared by immersing a fuel
injection valve the edge portion of which was chrome-plated into a
solution of compound 37 with 0.2 wt % concentration (which uses as
its solvent perfluorobutylmethylether HFE7100 (Sumitomo 3M K.K.))
for one hour, and after taking out of the solution, heating at
150.degree. C. for ten minutes. A film thickness of compound 37 on
the comparison example was measured using the RAS method to be 0.9
nm. A contact angle for water is smaller than 100 degrees. These
fuel injection valves were mounted on the test engine, and
conditions of accumulation of deposits were monitored, and also
measurements of decreases in the gasoline flow rates as indexes
representing quantities of accumulation of deposits were conducted.
The test engine used for evaluation of the conditions of
accumulation of deposits is a direct injection 4-cycle, V-type
6-cylinder engine manufactured by Nissan Motors Co. By circulating
water at 80.degree. C. through the engine head, the temperature of
the engine head was controlled at 90-110.degree. C. The tests were
done at 1200 rpm, 2200 cc/h fuel rate, and for 140 hours of
operation.
[0083] As clearly shown in FIG. 10, the fuel injection valve the
edge portion of which was chrome-plated and coated by both layers
of Al.sub.2O.sub.3 film and compound 37 is characterized by having
a thicker film of compound 37 compared to the comparison example
which was chrome-plated and coated by compound 37 alone, thereby
advantageously having a remarkably smaller decrease in the flow
reduction rates. From the result, it can be concluded that the
oxide film of the invention is very effective as the bonding
acceleration layer.
[0084] EMBODIMENT 8
[0085] With reference to FIG. 11, a schematic block diagram of a
direct injection engine according to another embodiment of the
invention is shown. Embodiment 8 of the invention is comprised of:
an air intake sensor 49; a throttle actuator 40; an ignition plug
48; a high pressure fuel injection valve 47 for directly injecting
atomized fuel particles into a cylinder suitable of super lean burn
combustion as in the embodiment 1; a high pressure fuel supply pump
51 for supplying fuel to the high pressure injection valve; an
air/fuel ratio sensor 41; a catalyst 42; and a control unit 43,
wherein the feature of the invention is characterized in a control
method of the control unit 43 in an arrangement of the invention in
which the high pressure injection valve 47 is provided in
juxtaposition with ignition plug 48. The control unit 43 determines
a combustion mode in response to an acceleration pedal operation
and an engine speed by its combustion mode determination means.
After calculation of a target air/fuel ratio by a target air/fuel
ratio computing means in response to a combustion mode, a fuel
injection quantity is computed by a fuel injection computing means.
On the other hand, a throttle opening value is calculated by a
throttle opening value computing means in response to the
combustion mode.
[0086] With respect to numerals in FIG. 11, 46 depicts an air
intake valve, 45 depicts a piston, 50 depicts an exhaust valve.
Fuel injection valve 47 used here is the same as that of embodiment
1 as shown in FIG. 2, and a deposit accumulation prevention film of
the invention is formed on its part and vicinity thereof to be
exposed to a combustion gas, then, engine tests thereof were
conducted in the same way as the other embodiments of the
invention. A film thickness of its deposition prevention coating
was set at approximately 2 nm. A flow reduction rate after 40 hours
of operation for this embodiment was measured, and its flow
reduction rate was found to be extremely small as small as 2%.
[0087] The following features have been accomplished according to
the invention that the accumulation of deposits on the surface of
the gasoline direct injection valve during combustion of gasoline
can be prevented, and/or a gasoline direct injection valve which
can easily remove the deposits accumulated thereon is provided,
thereby ensuring optimization of a gasoline concentration and air
flow specified in the engine cylinder for a long time of operation,
enabling the super lean burn combustion control, and thereby
providing automobiles with improved fuel mileage.
* * * * *