U.S. patent application number 14/125215 was filed with the patent office on 2014-07-17 for method and apparatus for reducing emissions and/or reducing friction in an internal combustion engine.
This patent application is currently assigned to Henkel AG & Co.KGaA. The applicant listed for this patent is Shawn E. Dolan, James P. Golding. Invention is credited to Shawn E. Dolan, James P. Golding.
Application Number | 20140196439 14/125215 |
Document ID | / |
Family ID | 46384499 |
Filed Date | 2014-07-17 |
United States Patent
Application |
20140196439 |
Kind Code |
A1 |
Dolan; Shawn E. ; et
al. |
July 17, 2014 |
METHOD AND APPARATUS FOR REDUCING EMISSIONS AND/OR REDUCING
FRICTION IN AN INTERNAL COMBUSTION ENGINE
Abstract
A method and apparatus for reducing at least one of HC, CO, and
NO.sub.x emissions from an operating internal combustion engine
fueled by hydrocarbon or similar fuels, such as alcohols, wherein a
portion of the internal combustion chamber has aluminum and/or
titanium containing surfaces coated with a titanium dioxide coating
further comprising a dopant in and/or on the adherent titanium
dioxide coating.
Inventors: |
Dolan; Shawn E.; (Sterling
Heights, MI) ; Golding; James P.; (Saint Clair
Shores, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dolan; Shawn E.
Golding; James P. |
Sterling Heights
Saint Clair Shores |
MI
MI |
US
US |
|
|
Assignee: |
Henkel AG & Co.KGaA
Duesseldorf
DE
|
Family ID: |
46384499 |
Appl. No.: |
14/125215 |
Filed: |
June 15, 2012 |
PCT Filed: |
June 15, 2012 |
PCT NO: |
PCT/US2012/042681 |
371 Date: |
March 28, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61497187 |
Jun 15, 2011 |
|
|
|
61624905 |
Apr 16, 2012 |
|
|
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Current U.S.
Class: |
60/274 ;
60/299 |
Current CPC
Class: |
C25D 7/04 20130101; C25D
9/12 20130101; F02B 77/04 20130101; F01N 2570/12 20130101; F01N
2570/10 20130101; F01L 2820/01 20130101; F02M 35/10334 20130101;
F01L 2301/00 20200501; F02B 23/104 20130101; F01N 2510/06 20130101;
F02F 2200/00 20130101; F02B 75/12 20130101; F02B 77/02 20130101;
F01N 2530/06 20130101; Y02T 10/12 20130101; Y02T 10/125 20130101;
F02F 3/14 20130101; F01N 3/18 20130101; F01L 3/04 20130101; F01L
2303/00 20200501; F01N 3/10 20130101; F01N 13/10 20130101; F02B
2075/125 20130101; F01N 2570/14 20130101 |
Class at
Publication: |
60/274 ;
60/299 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Claims
1. A method to reduce emissions from an apparatus comprising an
operating internal combustion engine, said internal combustion
engine comprising a combustion chamber, an air-intake valve and an
exhaust gas valve; the method comprising depositing a chemically
adherent titanium dioxide containing coating on a portion of
aluminum surfaces of at least one of: a portion of surfaces
defining the combustion chamber; an internal surface of an
air-intake passage in communication with the combustion chamber via
an air-intake port that is opened and dosed by the intake valve; an
internal surface of an exhaust emission passage in communication
with the combustion chamber via an exhaust gas valve through an
exhaust gas port; the air-intake valve; the exhaust gas valve; and
an exhaust manifold in communication with the exhaust emission
passage; such that, during operation of said engine, intake air,
fuel/air mixture and/or exhaust gas contact said coating thereby
increasing decomposition rate of HC, CO or NO.sub.x and/or reducing
formation rate of CO or NO.sub.x emissions resulting from
combustion in the combustion chamber.
2. A method to reduce emissions from an operating internal
combustion engine, comprising the steps of: determining a state of
an engine operating parameter corresponding to an emission value of
at least one of HC, CO and NO.sub.x emitted from a combustion
chamber of an operating internal combustion engine, determining a
target reduction in concentration of at least one of HC, CO and
NO.sub.x in exhaust gas discharged from the operating internal
combustion engine corresponding to the state of the engine
operating parameter corresponding to the emission value of at least
one of HC, CO and NO.sub.x emitted from the combustion chamber of
the operating internal combustion engine, wherein the concentration
of the at least one of HC, CO and NO.sub.x is measured at a
selected location in a path of the exhaust gas that is downstream
from the combustion chamber; and depositing a chemically adherent
titanium dioxide containing coating on a portion of surfaces of a.
the combustion chamber; b. an air-intake passage in communication
with the combustion chamber; c. an exhaust passage in communication
with the combustion chamber; d. Intake and/or exhaust valves;
and/or e. an exhaust manifold in communication with the exhaust
passage; to effect said target reduction in concentration of at
least one of HC, CO and NO.sub.x in exhaust gas discharged from the
operating internal combustion engine.
3.-12. (canceled)
13. An internal combustion engine comprising: external surfaces and
internal surfaces, said internal surfaces comprising a group of
internal surfaces located on at least one of a combustion chamber,
an air intake passage, an exhaust passage, an exhaust manifold, a
valve and combinations thereof; at least a portion of said group of
internal surfaces being metal selected from aluminum, aluminum
alloy, titanium or titanium alloy; and at least some portions of
the metal being coated metal surfaces having a chemically adherent
coating comprising TiO.sub.2, said coated metal surfaces positioned
such that, during operation of said engine, intake air, fuel/air
mixture and/or exhaust gas contact said chemically adherent coating
thereby increasing decomposition rate of HC, CO or NO.sub.x and/or
reducing formation rate of CO or NO.sub.x emissions resulting from
combustion in the combustion chamber.
14. The engine of claim 13 further comprising an exhaust system
extending from the exhaust manifold to an exhaust pipe wherein at
least a portion of internal surfaces of the exhaust system being
aluminum, aluminum alloy, titanium or titanium alloy coated with
said chemically adherent coating.
15.-18. (canceled)
19. The method according to claim 1, comprising applying the
coating to at least one of a bowl surface of a piston, a crown
surface of a piston.
20. The method according to claim 1, comprising applying the
coating to top surfaces of the intake and exhaust valves.
21. The method according to claim 1, comprising applying the
coating to a surface of a cylinder head exposed to the combustion
chamber.
22. The method according to claim 1, comprising applying the
coating to a surface of walls of a cylinder and/or a cylinder
liner.
23. The method according to claim 1, further comprising a dopant in
and/or on the chemically adherent titanium dioxide containing
coating.
24. The method according to claim 1, wherein determining a state of
an engine operating parameter corresponding to an emission value of
at least one of HC, CO and NO.sub.x emitted from a combustion
chamber of an operating internal combustion engine, comprises
determining engine speed of the internal combustion engine
operating at steady state engine temperature.
25. The method according to claim 1, wherein determining a state of
an engine operating parameter corresponding to an emission value of
at least one of HC, CO and NO.sub.x emitted from a combustion
chamber of an operating internal combustion engine, comprises
determining engine exhaust gas recirculation (EGR) values of the
internal combustion engine operating at steady state engine
temperature.
26. The method according to claim 1, wherein determining a state of
an engine operating parameter corresponding to an emission value of
at least one of HC, CO and NO.sub.x emitted from a combustion
chamber of an operating internal combustion engine, comprises
determining engine load or torque of the internal combustion engine
operating at steady state engine temperature.
27. The method according to claim 1, wherein determining a state of
an engine operating parameter corresponding to an emission value of
at least one of HC, CO and NO.sub.x emitted from a combustion
chamber of an operating internal combustion engine, comprises
determining engine indicated mean effective pressure (IMEP) of the
internal combustion engine operating at steady state engine
temperature.
28. The engine according to claim 13 comprising a combustion
chamber having at least one aluminum, aluminum alloy, titanium or
titanium alloy surface, at least a portion of said surface having
deposited thereon a coating comprising at least 25 wt % TiO.sub.2
in a layer thickness such that during operation of said engine
exhaust gas emissions of HC, CO and/or NO.sub.x from the combustion
chamber are less than said emissions from a like engine having no
titanium dioxide coating on combustion chamber surfaces.
29. The engine according to claim 13, wherein the coated metal
surfaces having a chemically adherent coating comprising TiO.sub.2
are polished surfaces having an Ra of 0.01 to 1.0 micron.
30. The engine according to claim 13, further comprising a dopant
in and/or on the chemically adherent coating comprising TiO.sub.2.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method and apparatus for reducing
at least one of HC, CO, and NO.sub.x emissions from an operating
internal combustion engine fueled by hydrocarbon or similar fuels,
such as alcohols, wherein a portion of the internal combustion
chamber has aluminum and/or titanium containing surfaces coated
with a titanium dioxide coating, further comprising a dopant in
and/or on the titanium dioxide coating. The invention also provides
reduced friction titanium dioxide coated engine components and
methods of making same.
BACKGROUND OF THE INVENTION
[0002] Three major automotive pollutants are carbon monoxide (CO),
unburned hydrocarbons (HC), and oxides of nitrogen (NO.sub.x).
Gasoline, diesel and other hydrocarbon fuels contain hydrogen and
carbon, as do similar organic fuels, such as alcohol-based fuels.
Nitrogen, carbon dioxide and oxygen are all present in air. When
air and these types of fuels are mixed and burned in internal
combustion chambers, the by-products of combustion are partially
burned fuel, carbon, carbon dioxide (CO.sub.2), carbon monoxide
(CO), and water vapor. Since the combustion process in the
cylinders is rarely, if ever, 100% complete, some unburned fuels,
for example hydrocarbons (HC), are left over in the exhaust gases.
Oxides of nitrogen (NO.sub.x) are also formed and are thought to be
caused by high cylinder temperature. If the combustion chamber
temperatures are above 1,371 degrees Celsius, some of the oxygen
and nitrogen combine to form NO.sub.x. In the presence of sunlight,
HC and NO.sub.x join to form smog. A great deal of attention has
been devoted to reducing internal combustion engine emissions of
HC, CO, and NO.sub.x.
[0003] On many commercially available vehicles, catalytic converter
devices are used to convert HC, CO and NO.sub.x to N.sub.2,
O.sub.2, CO.sub.2 and H.sub.2O. Catalytic converter devices contain
beads or honeycomb substrates, coated with a thin coating of
platinum, palladium, or rhodium, and mounted in a container. They
are typically installed downstream of the exhaust manifold and
positioned between the exhaust manifold and the muffler. This means
of reducing exhaust emissions has drawbacks. The metals used to
coat the beads/honeycombs are expensive and lose their catalytic
activity over time. Also, the catalytic converter device is
typically located outside of the engine compartment underneath the
vehicle where it is subject to damage from road hazards. Urea
injection systems found on some diesel engines using Selective
Catalytic Reduction (SCR) catalysts also have drawbacks. Injection
of a reducing agent, for example urea or ammonia is necessary for
proper function; thus a urea/ammonia source is required. Also,
although urea is the safest reducing agent to store, it requires
conversion to ammonia through thermal decomposition in order to be
used as an effective reductant. There is thus a need for
alternative or supplemental methods of reducing emissions of HC,
CO, and NO.sub.x.
[0004] U.S. Pat. No. 3,697,091 describes bearing faces of ferrous
metal compression and oil control piston rings of internal
combustion engines having a plasma-applied, bearing face coating
which consists essentially of about 75-90% aluminum oxide and
10-25% by weight titanium oxide. A ferrous metal piston ring coated
with a plasma-applied coating of alumina and titania along with
ferric oxide is disclosed in U.S. Pat. No. 4,077,637. In U.S. Pat.
No. 4,115,959, a ferrous metal piston ring coated with a
plasma-applied alumina-titania coating is described which further
includes about 10-15% of an alkaline earth metal fluoride. Rings
coated with alumina-titania plasma applied coatings have exhibited
a tendency to flake or blister during engine operation. Blisters of
about 1/16'' diameter and 0.0001'' thickness appear in the surface
of the coating which is generally 0.004'' thick. The blister
material is then scuffed off and a loss of coating results.
Delamination by blistering and spalling of portions of the coating
is undesirable. Ceramic containing organic resin paints have also
been used on pistons and cylinders to retain heat inside of the
combustion chamber, which increases cylinder temperature. A
downside of known thermal insulators is that high cylinder
temperature causes NO.sub.x formation.
[0005] None of the above-described coatings has shown usefulness in
reducing the amount of HC, CO, and NO.sub.x exhaust emissions from
internal combustion engines. In addition, these coatings, including
so-called ceramic coatings, thermal spray coatings and plasma
assisted coatings are very expensive and are physically adhered,
not chemically bonded to the surface, which results in adhesion
problems, particularly during temperature cycling. Thermal spray
coatings and plasma assisted coatings will be understood by those
of skill in the art to mean coatings deposited by using a hot gas
spray or gas plasma spray to carry a powder to a substrate where
the powder is physically deposited onto the substrate. Also,
traditional organic containing skirt coatings have poor wear and
temperature resistance when compared to the present invention.
SUMMARY OF THE INVENTION
[0006] Applicants have found that coating portions of aluminum
and/or titanium surfaces of an internal combustion engine and/or
portions of the exhaust system, e.g. the exhaust manifold, which
come in contact with intake air, fuel/air mix and/or exhaust gases
with a titanium dioxide coating as described herein provides
surprising reductions of at least one of HC, CO, and NO.sub.x
emitted in downstream exhaust gasses.
[0007] One aspect of the invention is a method of reducing
concentration of at least one of HC, CO and NO.sub.x in exhaust
gasses emitted from an apparatus comprising an operating internal
combustion engine, the method comprising or consisting of steps of:
[0008] a. determining initial concentration of at least one of HC,
CO and NO.sub.x in exhaust gasses emitted from an apparatus
comprising an operating internal combustion engine comprising a
combustion chamber and operating at a selected engine operation
parameter, [0009] b. selecting a target concentration, less than
the initial concentration, or a target reduction in the initial
concentration of at least one of HC, CO and NO.sub.x for the
selected engine operation parameter of said engine; [0010] c.
coating portions of internal surfaces of one or more of: [0011] i.
the combustion chamber, [0012] ii. an air-intake passage in
communication with the combustion chamber, [0013] iii. an exhaust
passage in communication with the combustion chamber; [0014] iv.
intake and/or exhaust valves; and [0015] v. an exhaust manifold in
communication with the exhaust passage; [0016] with a titanium
dioxide containing coating to effect the target concentration or
the target reduction of concentration of at least one of HC, CO and
NO.sub.x in exhaust gasses emitted from the apparatus.
[0017] Another aspect of the invention is a method to reduce
emissions from an apparatus comprising an operating internal
combustion engine, said internal combustion engine comprising a
combustion chamber comprising an air-intake valve and an exhaust
gas valve; the method comprising depositing an chemically adherent
titanium dioxide coating comprising at least 15 wt % titanium
dioxide on a portion of aluminum surfaces of at least one of:
[0018] a portion of surfaces defining the combustion chamber;
[0019] an internal surface of an air-intake passage in
communication with the combustion chamber via an air-intake port
that is opened and closed by the intake valve;
[0020] an internal surface of an exhaust emission passage in
communication with the combustion chamber via an exhaust gas valve
through an exhaust gas port;
[0021] the air-intake valve;
[0022] the exhaust gas valve; and
[0023] an exhaust manifold in communication with the exhaust
emission passage;
such that, during operation of said engine, intake air, fuel/air
mixture and/or exhaust gas contact said coating thereby increasing
decomposition rate of HC, CO or NO.sub.x and/or reducing formation
rate of CO or NO.sub.x emissions resulting from combustion in the
combustion chamber.
[0024] In one aspect the coating is applied to one or more of a
bowl surface of the piston; a crown surface of the piston; surfaces
of the intake and exhaust valves, in particular those surfaces in
contact with the combustion chamber; a top surface of the cylinder
head exposed to the combustion chamber, a surface of walls of the
cylinder.
[0025] In another aspect of the invention the method comprises
applying the surface coating to a top surface of each piston, a
surface portion of each intake and exhaust valve in contact with
the combustion chamber, a surface portion of the cylinder head
exposed to the combustion chamber, and a wall surface of the
cylinder.
[0026] Another aspect of the invention provides an internal
combustion engine comprising:
[0027] external surfaces and internal surfaces, said internal
surfaces comprising a group of internal surfaces contacted during
engine operation with intake air, fuel/air mix and/or exhaust
gases, said internal surfaces being located on a combustion
chamber, an air intake passage, an exhaust passage, an exhaust
manifold, a valve and combinations thereof; at least a portion of
said group of internal surfaces being metal selected from aluminum,
aluminum alloy, titanium or titanium alloy; and at least some
portions of the metal being coated metal surfaces having a coating
comprising at least 12 wt % TiO.sub.2, said coated metal surfaces
positioned such that, during operation of said engine, intake air,
fuel/air mixture and/or exhaust gas contact said coating thereby
increasing decomposition rate of HC, CO or NO.sub.x and/or reducing
formation rate of CO or NO.sub.x emissions resulting from
combustion in the combustion chamber.
[0028] The engine may further comprise an exhaust system extending
from the exhaust manifold to an exhaust pipe wherein at least a
portion of internal surfaces of the exhaust system being aluminum,
aluminum alloy, titanium or titanium alloy coated with said
coating.
[0029] Another aspect of the invention is an engine comprising a
combustion chamber having at least one aluminum, aluminum alloy,
titanium or titanium alloy surface, at least a portion of said
surface having deposited thereon a coating comprising at least 25
wt % TiO.sub.2 in a layer thickness such that during operation of
said engine exhaust gas emissions of HC, CO and/or NO.sub.x from
the combustion chamber are less than said emissions from a like
engine having no titanium dioxide coating on combustion chamber
surfaces.
[0030] Another aspect of the invention is a method to reduce
emissions from an apparatus comprising an operating internal
combustion engine, comprising the steps of:
[0031] determining a state of an engine operating parameter
corresponding to an emission value of at least one of HC, CO and
NO.sub.x emitted from a combustion chamber of an operating internal
combustion engine,
[0032] determining a target reduction in concentration of at least
one of HC, CO and NO.sub.x in exhaust gas discharged from the
operating internal combustion engine corresponding to the state of
the engine operating parameter corresponding to the emission value
of at least one of HC, CO and NO.sub.x emitted from the combustion
chamber of the operating internal combustion engine, wherein the
concentration of the at least one of HC, CO and NO.sub.x is
measured at a selected location in a path of the exhaust gas that
is downstream from the combustion chamber; and
[0033] depositing a titanium dioxide containing coating on a
portion of surfaces of
a. the combustion chamber; b. an air-intake passage in
communication with the combustion chamber; c. an exhaust passage in
communication with the combustion chamber; d. intake and/or exhaust
valves; and/or e. an exhaust manifold in communication with the
exhaust passage; to effect said target reduction.
[0034] In one embodiment, determining a state of an engine
operating parameter corresponding to an emission value of at least
one of HC, CO and NO.sub.x emitted from a combustion chamber of an
operating internal combustion engine comprises determining a state
of one or more of the following engine operating parameters: engine
speed, torque, load, exhaust gas recirculation (EGR) and indicated
mean effective pressure (IMEP).
[0035] Another aspect of the invention comprises friction and
bearing surfaces comprising surfaces coated with polished titanium
dioxide which provide a reduction in static and dynamic friction as
compared to unpolished titanium dioxide coated surfaces and
conventional friction reducing coatings for combustion
chambers.
[0036] Another aspect of the invention comprises an internal
combustion engine comprising:
[0037] external surfaces and internal surfaces,
[0038] at least a portion of said internal surfaces being aluminum,
aluminum alloy, titanium or titanium alloy; and
[0039] a coating comprising at least 12 wt % TiO.sub.2 chemically
adhered to at least some of the aluminum, aluminum alloy, titanium
or titanium alloy internal surfaces thereby forming titanium
dioxide containing coated internal surfaces;
[0040] wherein, portions of the engine that comprise titanium
dioxide coated internal surfaces include surfaces that are
contacted with intake air, fuel/air mix and/or exhaust gases during
operation of said engine.
[0041] An aspect of the invention includes an engine further
comprising an exhaust system comprised of an exhaust manifold and
an exhaust pipe wherein at least a portion of the exhaust system
comprises said titanium dioxide coated internal surfaces.
[0042] An aspect of the invention comprises an internal combustion
engine including a variable volume combustion chamber defined by a
piston reciprocating within a cylinder between top and bottom
center points and a cylinder head comprising an intake valve and an
exhaust valve wherein a portion of the internal combustion chamber
comprises aluminum, aluminum alloy, titanium or titanium alloy
surfaces, at least a portion of said surfaces having deposited
thereon a coating comprising at least 12 wt % TiO.sub.2. In one
embodiment, the engine is a four-stroke internal combustion engine;
in another embodiment, the engine is a two-stroke internal
combustion engine. In yet another embodiment, the combustion
chamber is defined by a rotor and a rotary chamber.
[0043] In some embodiments, the coating is deposited
electrolytically such that an amorphous coating comprising at least
15 wt % TiO.sub.2 is chemically bonded to the aluminum, aluminum
alloy, titanium or titanium alloy surfaces. In one embodiment, the
titanium dioxide coating further comprises phosphorus, present in
amounts of, in increasing order of preference, less than 10, 5,
2.5, 1 wt % and in increasing order of preference, at least 0.0001,
0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5 wt %. In one embodiment,
the titanium dioxide coated surfaces exhibit thermal shock
resistance to quenching in liquid nitrogen to -197.degree. C. from
a peak metal temperature of 550.degree. C. (the alloy itself would
melt if taken above this temperature--the titanium dioxide coating
is stable to 900.degree. C. in an oxidizing environment.
[0044] Another aspect of the invention includes a method to reduce
NO.sub.x emissions from an operating internal combustion engine,
comprising: applying the aforementioned titanium dioxide coating to
a portion of surfaces of the combustion chamber.
[0045] Except in the claims and the operating examples, or where
otherwise expressly indicated, all numerical quantities in this
description indicating amounts of material or conditions of
reaction and/or use are to be understood as modified by the word
"about" in describing the scope of the invention. Practice within
the numerical limits stated is generally preferred, however. Also,
throughout the description, unless expressly stated to the
contrary: percent, "parts of", and ratio values are by weight or
mass; the description of a group or class of materials as suitable
or preferred for a given purpose in connection with the invention
implies that mixtures of any two or more of the members of the
group or class are equally suitable or preferred; description of
constituents in chemical terms refers to the constituents at the
time of addition to any combination specified in the description or
of generation in situ within the composition by chemical
reaction(s) between one or more newly added constituents and one or
more constituents already present in the composition when the other
constituents are added; specification of constituents in ionic form
additionally implies the presence of sufficient counter ions to
produce electrical neutrality for the composition as a whole and
for any substance added to the composition; any counter ions thus
implicitly specified preferably are selected from among other
constituents explicitly specified in ionic form, to the extent
possible; otherwise, such counter ions may be freely selected,
except for avoiding counter ions that act adversely to an object of
the invention; the word "mole" means "gram mole", and the word
itself and all of its grammatical variations may be used for any
chemical species defined by all of the types and numbers of atoms
present in it, irrespective of whether the species is ionic,
neutral, unstable, hypothetical or in fact a stable neutral
substance with well defined molecules; and the terms "solution",
"soluble", "homogeneous", and the like are to be understood as
including not only true equilibrium solutions or homogeneity but
also dispersions.
BRIEF DESCRIPTION OF THE DRAWING
[0046] FIG. 1 shows a drawing of portions of a four stroke internal
combustion engine in accordance with the invention, including a
partial cross-sectional view of the engine area occupied by the
combustion chamber of the engine.
[0047] FIGS. 2 and 3 show transmission electron micrographs of the
external surface of tested titania coatings deposited on aluminum
substrates by plasma electrolytic deposition according the
invention at two different magnifications.
[0048] FIG. 4 shows a micrograph of a fast ion bombardment
cross-section through the aluminum substrate 400 and the titania
coating 300, with pores 100, deposited on an aluminum substrate by
plasma electrolytic deposition according the invention with a top
coating of platinum 200.
[0049] FIG. 5 shows a glow discharge optical emission spectroscopy
(GDOES) of a 13-14 micron thick titania coating on aluminum having
a vanadium dopant present in the electrolyte and deposited in the
titania coating.
[0050] FIG. 6 shows graphs of NOx emissions for coated cylinder
heads at varied engine RPM and air/fuel ratios.
DETAILED DESCRIPTION OF THE INVENTION
[0051] An aspect of the invention comprises a method and apparatus
for reducing at least one of HC, CO, and NO.sub.x emissions from an
operating internal combustion engine including a combustion
chamber, wherein a portion of the internal combustion chamber has
aluminum or titanium containing surfaces coated with adherent metal
oxide, chemically bonded to the surfaces, preferably containing
titanium dioxide as described herein.
[0052] Suitable combustion chambers include rotors and rotor
chambers of rotary engines and variable volume combustion chambers,
for example two or four-stroke engine combustion chambers defined
by a piston reciprocating within a cylinder between top and bottom
center points and a cylinder head. The combustion chambers
typically comprise an intake valve and an exhaust valve which may
also be coated with titanium dioxide as described herein. The
internal combustion engine may utilize any fuel that generates HC,
CO, and/or NO.sub.x exhaust emissions upon combustion in air, e.g.
organic fuels including alcohol-based and hydrocarbon fuels, such
as gasoline, gasoline/oil mixtures, kerosene or diesel, and the
like. The engine may use fuel injection, carburetor or other means
of supplying fuel, known in the art. Spark plugs, glow plugs or
other known means for igniting the fuel/air mixture in the
combustion chamber may be used. A portion of surfaces of each
combustion chamber has a surface coating of titanium dioxide
deposited thereon which functions to increase decomposition rate of
HC, CO, and/or NO.sub.x, and/or reduce formation rate of CO and/or
NO.sub.x reaction products of combustion reactions taking place in
the combustion chamber.
[0053] The general operation and construction of an engine having
surface coatings for purifying an exhaust gas according to the
present invention is that of a two or four stroke internal
combustion engine or rotary internal combustion engine, which may
be mounted on, for example, a motorized vehicle or other apparatus.
Typically, such engines comprise multiple combustion chambers made
up of multiple cylinders and a piston inserted in each cylinder, or
at least one rotor chamber having at least one rotor installed in
the rotor chamber. Optionally, the cylinder or rotor chamber may
additionally comprise a liner as is known in the art. If a liner is
present, a surface of the liner may be coated according to the
invention instead of or in addition to a surface of the cylinder or
rotor chamber.
[0054] An ignition source, such as a spark or glow plug, connected
to an ignition circuit is provided for each combustion chamber in a
manner known in the art and when actuated, ignites fuel/air mixture
in the combustion chamber. In some engines, for example diesel
engines, after initial start-up of the engine, the ignition source
is compression of the fuel/air mixture. A fuel source, for example
one or more fuel injection valves that directly inject fuel into a
combustion chamber, is provided. In some embodiments, the direct
fuel injection valve is replaced with port injection, a carburetor,
a throttle body or similar device(s) that introduces a fuel or
fuel/air mixture to the combustion chamber. The combustion chamber
is in communication with a source of air, such as for example one
or more air-intake passages, via an air-intake port. Typically an
air-intake passage supplies drawn air to the combustion chamber of
the engine. The section of the air-intake passage on the downstream
side may diverge into independent passages, each of which
corresponds to individual cylinders, in communication with the
air-intake ports of the respective cylinders. An exhaust manifold
for emitting exhaust gas from the combustion chamber communicates
with the combustion chamber through an exhaust gas port. The
exhaust manifold may be diverged at the upstream end into passages,
each of which corresponds to individual cylinders and in
communication with the combustion chamber of its respective
cylinder via an exhaust gas valve through an exhaust gas port. In
such an engine, the exhaust manifold may contain an exhaust passage
for each exhaust port in the cylinder head, and the manifold is
fitted against the exhaust port area of the cylinder head in a
manner known in the art. The exhaust passages from each port in the
manifold may join into a common single passage before they reach an
manifold flange. An exhaust pipe is connected to the exhaust
manifold flange.
[0055] The exhaust manifold conducts the exhaust gases from the
combustion chambers to the exhaust pipe. Many exhaust manifolds are
made from ferrous metal. Exhaust systems or portions thereof to be
coated according to the invention may be aluminum, titanium,
aluminum alloy, titanium alloy or may be another substrate having a
layer of one of the aforesaid metals deposited thereon. The exhaust
manifold, exhaust pipe and/or the tail pipe may be coated with a
titanium dioxide coating according to the invention. In one
embodiment, at least a portion of an interior surface of an exhaust
manifold and/or an exhaust pipe is coated with a titanium dioxide
coating as described herein.
[0056] Test data included herein demonstrates that operating
characteristics of an internal combustion engine change between an
engine having aluminum metal combustion chamber surfaces, and a
similar or the same engine having combustion chambers with at least
a portion of the aluminum surfaces covered with a titanium dioxide
coating deposited as described herein. Furthermore, it was observed
experimentally that combustion is positively affected by the
presence of the titanium dioxide coating chemically deposited as
described herein during engine tests in several ways. First, the
coating provides a protective layer when used on pistons which
extended the life of a high performance engine piston set by at
least two-fold by protecting the piston crown from heat damage.
Second, there was a reduction in noxious emission gases of CO, NO,
and unburned hydrocarbons (HC) for an engine that was operated with
pistons coated in titanium dioxide as described herein as compared
to an aluminum combustion chamber engine operated in like
circumstances with uncoated pistons. Third, for combustion chamber
surfaces which move slidably in relation to each other, for example
piston skirt portions and cylinder walls, a coating of titanium
dioxide deposited as described herein provides improved adhesion of
the coating and heat resistance as compared to conventional
coatings, including physically adhered piston coatings deposited by
thermal spray and plasma assisted spray techniques. Furthermore,
when polished according to one aspect of the invention, the coating
provides reduced static and dynamic friction as compared to the
same coating in an unpolished state. The static and dynamic
friction of a polished titanium dioxide surface was as good as or
better than the diamond-like carbon (DLC) coatings recognized in
the engine manufacturing industry as a performance benchmark for
piston coatings.
[0057] The portion of each combustion chamber which may have a
titanium dioxide coating includes a surface portion of the piston,
for example the skirt and/or crown; the surface of the walls of the
cylinder; surfaces of the intake and exhaust valves; a surface
portion of the cylinder head exposed to the combustion chamber, and
various combinations thereof. Other non-combustion chamber portions
of the engine that may be coated include the air intake passages
exhaust gas ports, and the exhaust system, meaning the exhaust
manifold, exhaust pipe and tailpipe.
[0058] FIG. 1 shows aspects of one embodiment of the invention
comprising an internal combustion engine 1 having surface coatings
for purifying an exhaust gas, which is shown for illustrative
purposes only and not for the purpose of limiting the invention.
Purifying an exhaust gas will be understood in the context of this
application to mean reducing concentration of HC, CO and/or
NO.sub.x in exhaust gas emitted from an operating internal
combustion engine. For exemplary purposes only, the internal
combustion engine shown in FIG. 1 has a reciprocating piston which
moves up and down in a cylinder, but the description of the
invention can be readily understood to apply to a rotary engine as
well.
[0059] In FIG. 1, the internal combustion engine 10 has an engine
block 12 comprising at least one cylinder 14 formed in the engine
block, an engine head 20 comprising a cylinder head 21, and a
reciprocating piston 30 inserted in the cylinder 14. In FIG. 1, the
walls 16 of the cylinder 14, the cylinder head 21 and the moveable
piston 30 define a variable volume combustion chamber 40 in the
engine. The reciprocating piston 30 comprises a crown portion 31,
having a surface area exposed to the combustion chamber facing the
cylinder head 21, and a body portion 32 which conforms to the
cylinder 14 in which it reciprocates. The body portion 32 comprises
a skirt portion 34, generally understood in the art to be that part
of the piston 30 located between the first ring groove 36 and the
bottom 38 of the piston 30. The skirt portion 34 comprises a
bearing area in contact with the cylinder wall 16. The skirt
portion 34 slides in relation to the cylinder wall 16 during
reciprocating motion of the piston.
[0060] In this embodiment, an ignition plug 60 connected to an
ignition circuit (not shown) is provided on the cylinder head 21 of
the combustion chamber 40 in such a manner that the ignition
electrode 62 faces the combustion chamber 40 and when actuated
ignites the air-fuel mixture in the combustion chamber 40.
[0061] An injector (fuel injection valve) 70 that directly injects
fuel to the combustion chamber 40 is provided; in this embodiment
it is located in the engine head 20 on the rim of the combustion
chamber 40. In some embodiments, the injector 70 is replaced with
port injection, a carburetor, a throttle body or similar device(s)
that introduces a fuel or fuel-air mixture to the combustion
chamber. The various means of introducing fuel into a combustion
chamber are known and not detailed herein.
[0062] The combustion chamber 40 is in communication with an
air-intake passage 22 via an air-intake port 24 that is opened and
closed by an air-intake valve 26. Likewise, the combustion chamber
40 is in communication with an exhaust passage 23 via an exhaust
port 25 that is opened and closed by an exhaust valve 27. Flow of
air through the air-intake port 24 is controlled by actuation of
the air-intake valve 26 and flow of exhaust gases through the
exhaust port 25 is controlled by actuation of the exhaust valve 27.
The intake and exhaust valves have a combustion surface portion,
28, 29 respectively, that is exposed to the combustion chamber 40.
Desirably, the engine head 20 comprises one or more air intake
ports 24 which supply air drawn through the air-intake passage 22
to the combustion chamber 40 and one or more exhaust ports 25
through which exhaust gases egress from the combustion chamber. The
exhaust passage 23 may merge with other such exhaust passages to
form an exhaust manifold (not shown) which leads to a common
exhaust pipe exiting the engine compartment. In FIG. 1, an emission
reducing coating 80 of metal oxide comprising titanium dioxide
according to the invention is shown on portions of the surfaces
defining the combustion chamber, namely the cylinder head 21 and
the crown portion 31 of the piston 30.
[0063] Based on the description herein, those of skill in the art
will understand application and use of the invention in alternative
embodiments of internal combustion engines such as two-stroke and
rotary engines. In one alternate embodiment, a rotary engine, for
example a so-called Wankel engine, having at least one rotor and at
least one rotor chamber may have portions of the engine coated
according to the invention. The rotary engine comprises intake and
exhaust valves, intake ports, exhaust ports and an exhaust system
as is known in the art. Each of the rotor chambers accommodates at
least one rotor. The rotor is formed by a generally-triangular
block, each side of which has a bulge at its central part when seen
in the direction of the rotation axis. The rotor has, along its
circumference, three generally-rectangular flank surfaces between
apexes. The rotor has apex seals on its respective apexes, which
move along the surfaces of the rotor chamber as the rotor moves
around the rotation axis. These apex seals together with inner
surfaces of the rotor chamber and the flank surfaces of the rotor
define three working chambers inside the rotor chamber. The three
working chambers move in a circumferential direction while each
working chamber goes through the intake, compression, combustion,
and exhaust operations, which respectively correspond to the intake
stroke, the compression stroke, the combustion stroke, and the
exhaust stroke of the reciprocating engine. Combustion takes place
serially in the working chambers (combustion chambers) thereby
turning the rotor. The rotor is geared in a manner known in the art
such that as the rotor makes one rotation, it turns a shaft in
communication with the rotor and generates rotational force, which
is the engine output. Similar to the piston/cylinder engines,
portions of the rotary engine that may be coated with a titanium
dioxide coating to reduce emissions and improve efficiency
according to the invention include surfaces that define the
combustion chamber, namely a surface portion of the rotor, a
surface portion of the rotor chamber; surfaces of the intake and
exhaust valves; intake ports; exhaust ports; the exhaust system and
various combinations thereof. In one embodiment, surfaces which
define the working chambers of the engine may be coated. In another
embodiment, additional portions of the engine that may be coated
include air intake passages, exhaust gas ports, and the exhaust
system, meaning the exhaust manifold, exhaust pipe and
tailpipe.
[0064] There is no specific limitation on the aluminum, titanium,
aluminum alloy or titanium alloy surface to be coated with the
metal oxide, preferably titanium dioxide coating in accordance with
the present invention. It is desirable for surfaces where the
chemical deposition of the titanium dioxide coating is to be made
electrolytically that the surfaces comprise a metal that contains
not less than, in increasing order of preference, 30, 40, 50, 60,
70, 80, 90, 95, 100% by weight titanium or aluminum.
[0065] The metal oxide coating desirably comprises at least 1, 5,
10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 95, 99 wt % TiO.sub.2.
In some embodiments, the titanium dioxide coating is deposited
electrolytically as described herein and exhibits an amorphous
morphology comprising surface pores 100 which extend only partially
into the coating layer 300. See FIG. 2-4. These pores are useful
for, among other things, increasing surface area of the coating and
may assist in lubrication between the piston and cylinder walls in
the combustion chamber. The surface area of the coating relates to
the amount of titanium or other active metal in the coating that is
available at the atmosphere/surface interface for contacting the
fuel and exhaust compositions in the engine to effect reduction in
concentration of HC, CO and NO.sub.x. Desirably, the metal oxide
coating provides a surface area to a substrate that is in a range
of about 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140,
150, 160, 170, 180 times greater than the surface area of the
substrate in an uncoated state. Greater surface area increases may
be utilized provided that other characteristics of the coating,
e.g. adhesion, are not reduced such that benefits of the invention
are not achieved. In one embodiment, the titanium dioxide coating
increased the surface area by 146 times versus a bare flat aluminum
panel as measured using the BET method.
[0066] In one embodiment, the titanium dioxide layer further
comprises phosphorus, present in amounts of, in increasing order of
preference, less than 10, 5, 2.5, 1 wt % and in increasing order of
preference, at least 0.0001, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1,
0.5 wt %. Other suitable additives may include effective amounts of
other metals, and metal oxides of the periodic table such as iron,
cobalt, zirconium and other transition metals. Also traditional
catalyst metals such as platinum and the like may be included in
the titanium dioxide coating provided that they do not interfere
unduly with the objects of the invention.
[0067] The titanium dioxide surface coating is sufficiently
adherent to the aluminum and titanium surfaces such that less than
10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, 0.1, 0.01% of the coated
surface area show blistering, delamination, or peeling of the
surface coating after, in increasing order of preference, 100, 150,
200, 250, 300, 350, 400, 450 500 hours of continuous operation of
the internal combustion engine at, in increasing order of
preference, 50, 60, 70, 80, 90 or 100% of maximum rpm under
temperature and lubrication conditions within engine manufacturer's
specifications. Test data shows that endurance race car pistons
after 20,000 miles exhibited no soot build up or observable changes
in the titanium dioxide coating. In one embodiment, the titanium
dioxide surface coating shows less than 5, 4, 3, 2, 1, 0.5, 0.1,
0.01% of the coated surface area show blistering, delamination, or
peeling of the surface coating after 150 hours of continuous
operation of the internal combustion engine at 100% of maximum rpm
under temperature and lubrication conditions within engine
manufacturer's specifications.
[0068] The titanium dioxide coating is insoluble in engine coolant
and lubricants and generally has an amorphous morphology. Desirably
the titanium dioxide coating is resistant to thermal shock and
thermal cycling such that no crazing or coating loss takes place
when the coated surfaces are subjected to temperature cycling
between -197.degree. C. and 550.degree. C. for at least in
increasing order of preference of 1, 2, 3, 4, 5 cycles. Desirably
the titanium dioxide coated surfaces exhibit thermal shock
resistance to quenching in liquid nitrogen to -197.degree. C. from
a peak metal temperature of 550.degree. C. Temperature resistance
was tested on aluminum pistons and found to be greater than
600.degree. C., the titania coating was still adherent to the
piston surface despite heat deformation of the piston.
[0069] In another test, resistance against thermal shocks was
tested as follows, a substrate coated with titania according to the
invention was maintained at 600.degree. C. for 84 h, followed by a
water quench at 5.degree. C., thereafter the substrate was
cross-hatched through the coating to the substrate and subjected to
reverse impact testing. A coated control panel was also subjected
to reverse impact testing. The results showed no loss of adhesion
of the coating, showing that the Plasma Electrolytic Deposition of
a titania coating on an aluminum substrate resulted in chemically
adherent coating with flexibility and adherence that meets the ball
reverse impact test both before and after thermal shock. This is a
significant improvement in adhesion as compared to plasma-deposited
and other physically adhered coatings.
[0070] Generally, the titanium dioxide coating is deposited in a
uniform layer having a thickness of between 1 and 20 microns. Lower
thicknesses may be utilized for economy, provided that the coating
is not so thin as to lose emission reduction benefits of the
invention. Thicknesses of the coatings are at least in increasing
order of preference 1, 2, 3, 4, 5, 6, 7, 8 or 9 microns and not
more than in increasing order of preference 20, 19, 18, 17, 16, 15,
14, 13, 12, 11, or 10 microns.
[0071] The titanium dioxide coating may optionally be polished to
reduce friction between a first coated surface and a second surface
that is coated or un-coated which may contact the first coated
surface. In this embodiment, the surfaces to be coated are not
limited to metal surfaces that contact intake air, fuel/air
mixtures and/or exhaust, but may include internal or external wear
surfaces. For this embodiment, the titanium dioxide coating is
desirably deposited electrolytically such that the coating is
chemically bonded to the metal surface. Suitable surfaces which may
benefit from the coating are wear or contact surfaces of, for
example, an engine, including plain bearings, rocker arms, cam
shafts, and other bearing surfaces as well as piston skirts,
cylinders or cylinder liners whose design and function are known in
the art. Contact points between the two surfaces may be
intermittent or continuous. The combination of the strongly
adherent feature of the electrolytic coating and the polished
surface of the coating provides a long lasting, low friction
coating.
[0072] Polishing may remove from at least, in increasing order of
preference, 1, 0.1, 0.01, or 0.001 wt % up to at most, in
increasing order of preference, 90, 80, 70, 60, 50, 40, 30, 20, 10,
5, 2.5 wt % of the titanium dioxide coating. In one embodiment,
approximately 5-15 wt % of the coating is removed by polishing. In
one embodiment, a polished coated surface has an Ra of 0.1 to 0.75
microns, desirably an Ra of 0.2 to 0.5 microns, where Ra is the
average surface roughness calculated using measurements taken with
standard contact or non-contact profilimetry devices.
[0073] In a preferred embodiment of the invention, the titanium
dioxide coating is deposited electrolytically. The electrolyte
solution used comprises water, a water-soluble and/or
water-dispersible phosphorus oxy acid or salt, for instance an acid
or salt containing phosphate anion; and H.sub.2TiF.sub.6;
H.sub.2ZrF.sub.6 is an optional ingredient. Preferably, the pH of
the electrolyte solution is neutral to acid (more preferably, 6.5
to 2). The combination of a phosphorus-containing acid and/or salt
and the complex fluoride in the electrolyte solution produced a
different type of electrolytically deposited coating. The oxide
coatings deposited comprised predominantly oxides of metals from
anions present in the electrolyte solution prior to any dissolution
of the metals in the metal surface on which the coating was being
deposited. That is, this process results in coatings that result
predominantly from deposition of substances that are not drawn from
the surface being coated, resulting in less change to the substrate
of the article being coated, see FIG. 5. This feature is beneficial
where the size and shape of engine components, which are typically
designed within narrow tolerances, are not changed by the
above-described coating process and the coating deposits uniformly
and at a controlled thickness. In this embodiment, it is desirable
that the electrolyte solution comprise the at least one complex
fluoride, e.g. H.sub.2TiF.sub.6, and optionally H.sub.2ZrF.sub.6,
in an amount of at least, in increasing order of preference 0.2,
0.4, 0.6, 0.8. 1.0, 1.2, 1.3, 1.4, 1.5, 2.0, 2.5, 3.0, 3.5 wt. %
and not more than, in increasing order of preference 10, 9.5, 9.0,
8.5, 8.0, 7.5, 7.0, 6.5, 6.0, 5.5, 5.0, 4.5. 4.0 wt. %. The at
least one complex fluoride may be supplied from any suitable
source. The phosphorus oxysalt may be supplied from any suitable
source such as, for example, ortho-phosphoric acid, pyro-phosphoric
acid, tri-phosphoric acid, meta-phosphoric acid, polyphosphoric
acid and other combined forms of phosphoric acid, as well as
phosphorous acids and hypo-phosphorous acids, and may be present in
the electrolyte solution in partially or fully neutralized form
(e.g., as a salt, wherein the counter ion(s) are alkali metal
cations, ammonium or other such species that render the phosphorus
oxysalt water-soluble). Organophosphates such as phosphonates and
the like may also be used (for example, various phosphonates are
available from Rhodia Inc. and Solutia Inc.) provided that the
organic component does not interfere with the electrolytic
deposition. Preferred is the use of a phosphorus oxysalt in acid
form. The phosphorus concentration in the electrolyte solution is
at least 0.01 M. It is preferred that the concentration of
phosphorus in the electrolyte solution be at least, in increasing
order of preference, 0.01M, 0.015, 0.02, 0.03, 0.04, 0.05, 0.07,
0.09, 0.10, 0.12, 0.14, 0.16. In embodiments where the pH of the
electrolyte solution is acidic (pH<7), the phosphorus
concentration can be 0.2 M, 0.3 M or more and preferably, at least
for economy is not more than 1.0, 0.9, 0.8, 0.7, 0.6 M. A preferred
electrolyte solution for use in forming a protective titanium
dioxide coating according to this embodiment on an aluminum or
titanium containing surface may be prepared using the following
components:
TABLE-US-00001 H.sub.2TiF.sub.6 0.05 to 10 wt. % H.sub.3PO.sub.4
0.1 to 0.6 wt. % Water Balance to 100%
In carrying out the electrolytic coating of engine components, the
coating bath is maintained at a temperature between 0.degree. C.
and 90.degree. C. A pH adjuster may be present in the electrolyte
solution; suitable pH adjusters include, by way of non-limiting
example, ammonia, amine or other base. The amount of pH adjuster is
limited to the amount required to achieve a pH of 1-6.5, preferably
2-6, most preferably 3-5.
[0074] The electrolytic coating process comprises immersing
portions of the engine or articles having wear surfaces having
aluminum and/or titanium containing surfaces that are to be coated
with the titanium dioxide coating in the electrolytic coating
solution, which is preferably contained within a bath, tank or
other such container. The aluminum and/or titanium containing
surfaces are connected as the anode and a second metal article or
the tank itself is connected as the cathode. Electric current is
passed between the cathode and anode through the electrolyte for a
selected period of time sufficient to cause deposition of an
adherent, amorphous titanium dioxide coating on the aluminum and/or
titanium containing surfaces. The coated article is removed from
the coating bath and rinsed. Other treatments may be performed
thereafter to these surfaces prior to assembly, including polishing
and/or painting. In depositing the titanium dioxide coating
electrolytically, direct current (DC) is preferably used, and it
may be pulsed or non-pulsed direct current. Alternating current
(AC) may also be used, with voltages desirably between 200 and 600
volts (under some conditions, however, the rate of coating
formation may be lower using AC). The frequency of the wave may
range from 10 to 10,000 Hertz; higher frequencies may be used. In
one embodiment, direct current (DC) pulsed or non-pulsed is used at
an average of 200 to 1000 volts.
[0075] In one embodiment, the current is pulsed or pulsing direct
current desirably used in the range of at least, in increasing
order of preference 200, 250, 300, 350, 400 volts and at least for
the sake of economy, not more than in increasing order of
preference 1000, 900, 800, 700, 650, 600, 550 volts. The "off" time
between each consecutive voltage pulse preferably lasts between 10%
as long as the voltage pulse and 1000% as long as the voltage
pulse. During the "off" period, the voltage need not be dropped to
zero (i.e., the voltage may be cycled between a relatively low
baseline voltage and a relatively high ceiling voltage). The
baseline voltage thus may be adjusted to a voltage that is from 0%
to 99.9% of the peak applied ceiling voltage. The current can be
pulsed with either electronic or mechanical switches activated by a
frequency generator. When using pulsed current, the average voltage
is preferably not more than 500 volts, more preferably, not more
than 450 volts, or, most preferably, not more than 400 volts,
depending on the composition of the electrolyte solution selected.
The peak voltage, when pulsed current is being used, is preferably
not more than 1000, 900, 800, 700, 600, preferably 500, most
preferably 400 volts. In one embodiment, the peak voltage for
pulsed current is not more than, in increasing order of preference
600, 575, 550, 525, 500 volts and independently not less than 300,
310, 320, 330, 340, 350, 360, 370, 380, 390, 400 volts. In one
alternating current embodiment, the voltage is, in increasing order
of preference 600, 575, 550, 525, 500 volts and independently not
less than 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400
volts. In the presence of phosphorus containing components,
non-pulsed direct current, also known as straight direct current,
may be used at voltages from 200 to 600 volts. The non-pulsed
direct current desirably has a voltage of, in increasing order of
preference 600, 575, 550, 525, 500 volts and independently not less
than 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400 volts.
The average amperage per square foot is at least in increasing
order of preference 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 105,
110, 115 Amps/ft.sup.2, and not more than at least for economic
considerations in increasing order of preference 400, 350, 300,
275, 250, 225, 200, 180, 170, 160, 150, 140, 130, 125
Amps/ft.sup.2. More complex waveforms may also be employed, such
as, for example, a DC signal having an AC component. The higher the
concentration of the electrolyte in the electrolyte solution, the
lower the voltage can be while still depositing satisfactory
coatings.
[0076] Titanium dioxide coatings, as well as other metal oxide
coatings, deposited electrolytically by the above-described method
are chemically bonded to the metal surface and have increased
surface area as compared to the uncoated aluminum panel. Desirably,
the metal oxide coating has a surface area that is in a range of
about 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150,
160, 170, 180 times greater than an uncoated flat aluminum panel
surface. Greater surface area increases may be utilized provided
that other characteristics of the coating, e.g. adhesion, are not
reduced such that benefits of the invention are not achieved. The
coating has insolubility in lubricant and coolant, adherence that
is resistant to thermal cycling and thermal shock as described
above, and wear resistance suitable for use in the combustion
chamber and/or exhaust system with blistering, delamination and
peeling resistance as described herein.
[0077] Other methods of depositing titanium dioxide containing
coatings may be acceptable provided that increased decomposition
rate and/or reduced formation rate of at least one of HC, CO, and
NO.sub.x emissions from combustion taking place in the combustion
chamber as described above is achieved and the coating has
sufficient durability to be used in the combustion chamber and/or
the exhaust system.
[0078] The invention may be practiced by coating all surfaces of an
internal combustion engine that contact intake air, fuel/air
mixture and/or exhaust gas during engine operation with the metal
oxide containing titanium dioxide or only a portion of these
surfaces. At least for economy's sake, it may be preferable to
determine a target reduction in concentration of HC, CO or NO.sub.x
in exhaust gas discharged, and coat a sufficient number of surfaces
or surface area to achieve the reduction. As shown by the test data
below, the operating parameters of the engine affect the emissions
produced. It is desirable to determine the state of engine
operating parameter(s) resulting in an emission value so that
meaningful comparisons of emissions with and without the invention
can be made to allow deposition of the coating on sufficient
surfaces to effect the target reduction in concentration of at
least one of HC, CO and NO.sub.x in exhaust gas discharged. Engine
operating parameters include, by way of non-limiting example,
engine speed, torque, load, exhaust gas recirculation (EGR) and
indicated mean effective pressure (IMEP). According to one method
of the invention, the method to reduce emissions from an operating
internal combustion engine, comprises the steps of determining a
state of an engine operating parameter corresponding to an emission
value of at least one of HC, CO and NO.sub.x emitted from a
combustion chamber of an operating internal combustion engine;
determining a target reduction in concentration of at least one of
HC, CO and NO.sub.x in exhaust gas discharged from the operating
internal combustion engine corresponding to the state of the engine
operating parameter corresponding to the emission value of at least
one of HC, CO and NO emitted from the combustion chamber of the
operating internal combustion engine, wherein the concentration of
the at least one of HC, CO and NO.sub.x is measured at a selected
location in a path of the exhaust gas that is downstream from the
combustion chamber; and depositing a titanium dioxide containing
coating on a portion of surfaces of
a. the combustion chamber; b. an air-intake passage in
communication with the combustion chamber; c. an exhaust passage in
communication with the combustion chamber; d. intake and/or exhaust
valves; and/or e. an exhaust manifold in communication with the
exhaust passage; to effect said target reduction.
[0079] In one embodiment, piston skirts and/or cylinder walls, or
the rotary chambers, coated with a titanium dioxide coating as
described herein are subsequently polished to reduce surface
roughness. The method of polishing the titanium dioxide surface
comprises physically removing, at least in increasing order of
preference 1, 2, 3, 4 or 5 wt % and not more than in increasing
order of preference 90, 80, 70, 60, 50, 40, 30, 20, 10 wt % of the
coating. Any known polishing means are suitable. One method for
polishing comprises use of abrasive having a grit of less than in
increasing order of preference 45, 40, 35, 30, 25, 20, 15, 10, 5,
4, 3, 2, 1 micron. The composition of the grit can be those known
in the art, for example, diamond, cerium oxide, zirconium oxide,
ferric oxide, silicon carbide and the like. In one embodiment, a
polished coated surface is polished such that it has an Ra of 0.01,
0.05, 0.1, 0.15, 0.2, 0.25, 0.3 microns to not more than 0.4, 0.45,
0.5, 0.6, 0.7, 0.8, 1.0 microns.
[0080] In an alternative embodiment, the titanium dioxide coated
internal surfaces of the engine may be subsequently coated with a
secondary coating to provide additional desirable properties to
coated internal surfaces of the engine. A non-limiting example
includes dry film lubricants, such as graphite, molybdenum
disulfide, polymer coatings containing graphite and/or molybdenum
disulfide, fluoropolymers, silicones or waxes and titanium dioxide
coatings deposited via Plasma-Assisted Layer Deposition (PALD) or
thermal spray.
[0081] It has been surprisingly discovered that doping the titania
coating with certain metals can improve NOx emissions even further.
Doping, that is adding other elements or compounds to the titania
coating, can be accomplished by adding soluble or finely dispersed
solids to the electrolyte which may be deposited as or provide
components incorporated as dopants in the titania coating or by
adding a dopant after coating. Generally, any metal or metalloid
element that provides a reduction in HC, CO or NOx in exhaust gases
can be used provided that the compound or structure of a resulting
dopant, containing the metal or metalloid element, that is in or on
the titania is stable to the use environment e.g. temperatures and
chemistries, such that it remains active. Examples of use
environments include one or more of a combustion chamber, exhaust
passages, exhaust manifold and downstream exhaust system
components, upstream of any catalytic converter present, of an
internal combustion engine.
[0082] Incorporating dopant into the titania coating during PED can
be accomplished by doping the electrolyte with a liquid or a solid
dopant generating composition. The liquid or solid dopant
generating composition can be soluble or small particles of
insoluble additives or substances that are easily decomposed to
release metal or metalloids. The liquid or solid dopant generating
composition is added to the electrolyte in an amount such that
during PED, the dopant is deposited in or on the titania coating.
Suitable examples of soluble dopant generating compositions include
metals and metalloids of the Periodic Table and salts and oxides
thereof, in particular transition metals including actinide and
lanthanide series, for example cerium, silver, gold, platinum,
palladium, rhodium, cobalt and/or vanadium. Small particles of
insoluble additives such as nanoparticulate metals, metalloids and
compounds thereof may be incorporated into the titania coating or
into the pores thereof from the electrolyte. Suitable particulate
compounds can be for example, nitrides, oxides, carbides, sulfides
and the like. Particle diameters typically range from about less
than in increasing order of preference 100, 90, 80, 70, 60, 50, 40
nanometers and as small as in increasing order of preference, 35,
30, 25, 20, 15, 10, 5, 4, 3, 2, or 1 nanometers.
[0083] Post-coating doping of the titania coating can be
accomplished by contacting with a liquid or a solid dopant
generating composition.
[0084] Liquid post-coating doping can be through deposition of a
liquid additive that is dried in place, a reactive liquid that
generates the dopant in situ (e.g. an alkoxy titanate can be used
to generate a secondary titania have different properties or
crystal structure in addition to the PED titania), or a liquid that
is heat or otherwise treated to generate the dopant. For example, a
liquid containing a metal nitrate may be applied and subsequently
heated. The metal from the metal nitrate is effectively deposited
into the titania matrix and the nitrate is driven off as oxides of
nitrogen. Similar processes can be run using metal alkoxides and
metal ligand systems.
[0085] Solid post-coating doping can be through deposition of a
solid additive into the porous titania matrix or by generation of
the dopant in situ. Suitable examples of solid post-coating doping
include PVD, for example sputtering, CVD, for example radio
frequency CVD, gas plasma CVD, shotblasting, burnishing, wiping.
Particle diameters typically range from about less than in
increasing order of preference 100, 90, 80, 70, 60, 50, 40
nanometers and as small as in increasing order of preference, 35,
30, 25, 20, 15, 10, 5, 4, 3, 2, or 1 nanometers.
[0086] Suitable examples of thus deposited dopants include metals
and metalloids of the Periodic Table and oxides thereof. Transition
metals including actinide and lanthanide series metals, in
particular members of Groups 2-15, or Groups 3-12.
[0087] Substances that are easily oxidized include metal nitrates
that will contribute metal oxides to the titania. Suitable examples
of soluble substances include nitrates, acetates, alkoxy or other
metal ligand systems capable of release of a metal or metalloid
into the titania matrix.
[0088] Applicants tested a stock aluminum cylinder head, a titania
coated cylinder head and several cylinder heads wherein the titania
coating further comprised one of the following metals: cobalt,
platinum and vanadium on a four-stroke internal combustion engine,
see Example 10 below. The results showed that doping the high
surface area titania coating can further reduce NOx emissions as
compared to either a stock aluminum cylinder head or a titania
coated cylinder head, at lean, stoichiometric and rich air/fuel
ratios, see FIG. 6a-6d.
EXAMPLES
Example 1
Coating Internal Surfaces
[0089] A commercially available V8 cast aluminum air intake
component, identical to the cast aluminum air intake component of
Comparative Example 1, was alkaline cleaned by immersion for 5
minutes in Ridoline 298, an alkaline cleaner commercially available
from Henkel Corporation. The part was rinsed with water and was
immersed in an aqueous electrolyte solution prepared using 20.0 g/L
H.sub.2TiF.sub.6 (60%) and 4.0 g/L H.sub.3PO.sub.4. The pH was
adjusted to 2.2 using aqueous ammonia. The article was subjected to
electrolytic treatment for 3 minutes in the electrolyte solution
using pulsed direct current having a peak ceiling voltage of 450
volts (approximate average voltage=290 volts) at 90.degree. F. The
"on" time was 25 milliseconds, the "off" time was 9 milliseconds
(with the "off" or baseline voltage being 0% of the peak ceiling
voltage). The average current density was 80 amps/ft. No auxiliary
electrodes were required; the counter electrodes were placed more
than 13 inches from the outside of the part. The part was removed
from the bath, rinsed with water and inspected. A uniform coating,
10 microns in thickness, was formed on the surface of the aluminum
intake component. The coating was deposited over the entire air
intake component, including the inside of the cooling tunnels and
other areas of the casting. The coating was found to be
predominantly titanium dioxide. Traces of phosphorus, less than 10%
were also seen in the coating.
Example 2
Gasoline Engine Air Intake Coating
[0090] A production small block Ford V-8 engine with standard cast
aluminum air intake component was tested as a comparative uncoated
example (Comparative Example 1). The titanium dioxide coated cast
aluminum intake component of Example 1 was installed on the V-8
engine in place of the stock intake and the tests were run again
(Example 2). Results are shown below indicating an increase in
horsepower and torque for the coated air intake component.
TABLE-US-00002 TABLE 1 Horsepower Max. Torque Max. Substrate RPM
5700 RPM 4400 Example 2, coated 337.35 340.92 Comparative Example
1, uncoated 326. 330. Improvement %: 3.3% 3.3%
The increase in horsepower and torque showed improved power from
similar operating conditions tending to show improved utilization
of fuel by the engine when the coated intake was used.
Example 3
Thermal Shock
[0091] Two commercially available, after-market aluminum pistons
for an automotive engine were obtained from the same supplier for
comparative testing. One piston was bare aluminum and the second
piston was substantially the same, but had an existing skirt
coating based upon organic polymers mixed with solid film
lubricants, see Example 3 and Comparative Example 2,
respectively.
Example 3
[0092] The bare aluminum piston for an automotive engine was
treated according to Example 1. The entire piston, including the
wrist pin bore, skirt and top of the piston were uniformly coated
with a layer of titanium dioxide. The piston did not require
selective coating or any oven treatment, which is typically
required to coat pistons having a conventional separate skirt
coating. The coated piston was heated to 550.degree. C. for 16
hours and then immediately placed in 5.degree. C. water. The
coating on the piston and the piston body were unaffected, i.e.
unchanged, by the high temperature treatment and were also
unaffected by the thermal shock test, i.e. no warpage, cracking,
blistering delamination or crazing was observed.
Comparative Example 2
[0093] The aluminum piston having an existing skirt coating based
upon organic polymers mixed with solid film lubricants was heated
to 450.degree. C. After 4 hours at 450.degree. C., the conventional
skirt coating was completely removed from the piston surface,
leaving the bare aluminum substrate exposed.
Example 4
Adhesion
[0094] Adhesion of metal oxide coating electrolytically deposited
was conducted with and without secondary coatings applied.
Example 4-1
Flat Panels Having Electrolytic Coating with Secondary Coating
[0095] For Examples 4A-D, clean desmutted 6063 aluminum alloy
panels were coated, using an electrolyte solution prepared using
H.sub.2TiF.sub.6 (60%) 20.0 g/L and H.sub.3PO.sub.4 (75%) 4.0 g/L.
The panels were subjected to electrolytic coating treatment at pH 2
for 3 minutes in the electrolyte solution using pulsed direct
current having a peak ceiling voltage of 450 volts (approximate
average voltage=130 volts) at 90.degree. F. The "on" time was 10
milliseconds, the "off" time was 30 milliseconds (with the "off" or
baseline voltage being 0% of the peak ceiling voltage). A uniform
coating, 7.6 microns in thickness, was formed on the surface of the
aluminum-containing panels of Examples 4A-D. For Comparative
Examples A-D, 6063 aluminum alloy panels were shot-blasted
according to standard industry practice.
[0096] Each panel of Examples 4A-D and Comparative Examples A-D was
then thermal spray coated using high velocity oxy-fuel (HVOF) with
a thermal spray coating as disclosed in Table 2. Each panel was
thereafter subjected to adhesion testing according to ASTM D3359
wherein the coatings were crosshatched and subjected to adhesion
tests wherein commercially available 898 tape was firmly adhered to
each film and then pulled off at a 90.degree. angle to the surface.
The results below show that the electrolytically deposited coating
was not removed at all and that secondary layers of thermal spray,
which are only physically adhered, had improved adhesion to the
surfaces coated with the titanium dioxide.
TABLE-US-00003 TABLE 2 Thermal Spray Test Results from Example
Electrodeposited Layer Applied Coating ASTM D 3359 Comparative Shot
blasted, Titania Thermal Spray - 0B 100% loss of A no
electrodeposited layer 99 wt % TiO.sub.2 thermal spray coating 4A
Electrodeposited TiO.sub.2 Layer Titania Thermal Spray - 5B Perfect
Present 99 wt % TiO.sub.2 0% loss Comparative Shot blasted, Alumina
Thermal Spray - 0B B no electrodeposited layer 98.5 wt %
Al.sub.2O.sub.3; 1.0 wt % SiO.sub.2 70% loss 4B Electrodeposited
TiO.sub.2 Layer Alumina Thermal Spray - 4B Present 98.5 wt %
Al.sub.2O.sub.3; 1.0 wt % SiO.sub.2 Less than 1% loss Comparative
Shot blasted, Zirconia Thermal Spray - 1B C no electrodeposited
layer 80 wt % ZrO.sub.2; 20 wt % Y.sub.2O.sub.3 50% loss 4C
Electrodeposited TiO.sub.2 Layer Zirconia Thermal Spray - 4B
Present 80 wt % ZrO.sub.2; 20 wt % Y.sub.2O.sub.3 Less than 1% loss
Comparative Shot blasted, 79 wt % Fe, 18 wt % Mo, 0B D no
electrodeposited layer 7.0 wt % C 70% loss 4D Electrodeposited
TiO.sub.2 Layer 79 wt % Fe, 18 wt % Mo, 5B Perfect Present 7.0 wt %
C 0% loss
Example 4-2
Reverse Impact Adhesion Testing of Flat Panels Having Bare
Electrolytically Deposited TiO.sub.2 Coating
[0097] An aluminum alloy panel was first electrolytically coated
with a titanium dioxide coating having film thickness of 8-12
microns. The test panel was then crosshatched per ASTM D3359 method
B, down to the underlying aluminum surface. Reverse impact testing
was performed per ASTM D2794 by directly impacting the back-side of
the crosshatched area of the coated panel. Testing was performed at
110 in lb with a 4 lb weight. Then adhesion was checked using ASTM
standard wide semi-transparent pressure sensitive tape. The
subsequent tape pull revealed no loss of adhesion of the
electrolytically deposited coating despite fracture of the panel at
the cross-hatched area due to the impact testing.
Example 4-3
Engine Component, Piston, Having Electrolytic TiO.sub.2 Coating
with Secondary Coating
[0098] A commercially available, bare aluminum piston was coated as
in Example 1. Thereafter, an aqueous mixture of 10% NeoRez.RTM.
R9679 and 10% Aquagraph 6201 was applied to the coated piston to
form a dry film seal to act as a lubricant to reduce the
coefficient of friction and improve wear resistance in the event of
a low or no oil event in the internal combustion engine.
NeoRez.RTM. R9679 is an aliphatic aqueous colloidal dispersion of a
urethane polymer containing 37% by weight solids (specific gravity
of the solids is 1.16 and acid number of resin solids is 17.0), and
is commercially available from Zeneca Resins, Inc., Wilmington,
Mass. Aquagraph 6201 is a commercially available aqueous graphite
slurry. The sealant was dried on the coated piston at 190.degree.
C. for 5 minutes. The resin bonded dry film lubricant showed good
adhesion to the coated piston; there was no flaking, peeling or
blistering of the lubricant.
Example 5
Diesel Engine Testing
[0099] A diesel fueled internal combustion engine having a variable
volume combustion chamber defined by a piston, reciprocating within
a cylinder between top and bottom points, and a cylinder head
comprising two air-intake valves and two exhaust gas valves was
selected for testing. The piston and head were aluminum alloy. The
engine was operated without any titanium dioxide coating in the
combustion chamber at various engine operating parameters including
test speeds (rpm), IMEP and EGR with varied loading as described
below, and noise level and emissions were measured (Control).
Thereafter, the piston and the cylinder head of the engine were
removed and the piston crown and cylinder head were treated
according to Example 1 (Coated). The engine was reassembled and
tested under the same operating conditions as the uncoated engine
to allow for comparison of data. The results of the testing of
coated and uncoated engines are shown in the tables below.
TABLE-US-00004 TABLE 3 2000 rpm Uncoated Coated Engine sound level
(dB) Noise 88 87 Indicated Efficiency (%) 41.5 41.9 CO (g/kWh) 5.8
3.8 HC (g/kWh) 0.75 0.65 NO.sub.x Emissions (ppm) 152 148
[0100] Another engine operating parameter, percent of Emission Gas
Recycling (EGR %) was varied across 40%, 43% and 46% at engine
speed of 1500 rpm and 6.8 bar IMEP and carbon monoxide emissions
(CO), hydrocarbon emissions (HC) and oxides of nitrogen (NO.sub.x)
emissions were measured, see the table below.
TABLE-US-00005 TABLE 4 CO HC NO.sub.x Emissions NO.sub.x Emission
(g/kWh) (g/kWh) (g/kWh) Reduction EGR (%) Uncoated Coated Uncoated
Coated Uncoated Coated Coated 40 2.85 2.7 0.64 0.55 0.65 0.61 6% 43
3.3 3.3 0.66 0.58 0.49 0.43 8.8%.sup. 46 4.2 3.9 0.7 0.6 0.30 0.29
2%
[0101] The above table shows significant reductions in HC and
NO.sub.x emissions.
[0102] EGR (%) was varied across 38% and 41% at engine speed of
1500 rpm and 4.3 bar IMEP and additional measurements of CO, HC and
NO.sub.x emissions were taken. At 41% EGR the CO and HC emissions
were similar, and within experimental error of each other for
coated and uncoated. At 38% EGR, the samples showed less CO and HC
emissions for the coated sample. Surprising reductions in NO.sub.x
emissions at both EGR values were noted when the engine with
coating was compared to the engine without the coating, see the
table below.
TABLE-US-00006 TABLE 5 NO.sub.x Emissions NO.sub.x Emission (g/kWh)
Reduction EGR (%) Uncoated Coated Coated 38 0.95 0.65 31% 41 0.69
0.40 42%
[0103] Test results also showed that for engine speed of 1500 rpm
and 4.3 bar IMEP, the engine having the titanium dioxide coated
parts had higher percentage efficiency where both engines were
tested under comparable conditions. Specifically, the engines were
tested at substantially the same values over a range of engine
operating parameters including relative air/fuel ratio, mass flow
of humid air and EGR % s; for measured amounts of NO.sub.x
emissions ranging from 0.1 g/kWh to 2.0 g/kWh, the coated engine
parts delivered greater indicated efficiency percents at NO.sub.x
emissions of 0.3 g/kWh and above. These efficiencies amounted to
greater than 1% improvement in engine efficiency.
Example 6
Gasoline Engine Testing
[0104] An LE5 four cylinder automotive gasoline (unleaded) engine
was used for testing using a dynamometer calibration from a
corresponding production vehicle. The engine was a 2.4 L
port-injected engine with variable valve timing having cast
aluminum block. Two sets of parts were tested, each set consisting
of four pistons and a head made of aluminum. One set of parts was
coated according to Example 1 (coated). A second set of parts was
an essentially unmodified production engine set (control) and
provides a Comparative Example. The valve seats in the head of the
coated part set were modified from stock design to accommodate the
thickness of the coating. The same modification was made to the
valve seats of the uncoated head. Both heads had similar flow
characteristics. The same engine was used for testing both sets of
parts to reduce variations from engine to engine. The engine was
connected to a dynamometer equipped with a controller and exhaust
missions were measured using an emission measurement apparatus
commercially available from Horiba Instruments Inc., using the
following procedure: Engine emissions from the fully warmed up
engine were evaluated. Seven different speed and load points were
evaluated which are representative of the operation of the engine
over a FUDS cycle which is used to evaluate emissions for urban
driving in the United States. The dynamometer was operated at the
target speed in speed control mode. The engine throttle was
controlled to maintain constant torque. The engine was allowed to
reach a stable condition before measurements were taken. The engine
was swept through a number of different equivalence ratios while
emissions were recorded for a sixty second period at 100 Hz.
[0105] The results below compare the data from running the engine
with the uncoated "control" parts using commercially available oil
without Moly (Comparative Example) to data from running the engine
with the "coated" parts using Moly oil. Moly oil was commercially
available motor oil containing oil soluble molybdenum compositions.
The detailed data was analyzed to determine the emissions
concentrations at an equivalence ratio of 1.0 which is the target
EQR for a stoichiometric engine. Summary results for each point at
an EQR of 1.0 are provided below.
TABLE-US-00007 TABLE 6 Total Exhaust Hydrocarbon Concentration
(ppm) for Coated Parts (Example) and Control (Comparative Example)
Parts 1000 1600 1600 1600 2200 2200 2200 rpm, rpm, rpm, rpm, rpm,
rpm, rpm, 30 kPa 20 kPa 60 Kpa WOT 20 Kpa 60 kPa WOT control 3000
2200 1800 1050 1800 1600 900 coated 1500 1900 1800 1050 1100 1100
800
TABLE-US-00008 TABLE 7 Carbon Monoxide Concentration (%) for Coated
Parts (Example) and Control (Comparative Example) Parts 1000 1600
1600 1600 2200 2200 2200 rpm, rpm, rpm, rpm, rpm, rpm, rpm, 30 kPa
20 kPa 60 Kpa WOT 20 Kpa 60 kPa WOT control 2.2 0.8 0.5 1.4 0.75
0.6 0.5 coated 1.4 0.6 0.6 0.5 0.75 0.6 0.4
TABLE-US-00009 TABLE 8 NO.sub.x Concentration (ppm) for Coated
Parts (Example) and Control (Comparative Example) Parts 1000 1600
1600 1600 2200 2200 2200 rpm, rpm, rpm, rpm, rpm, rpm, rpm, 30 kPa
20 kPa 60 Kpa WOT 20 Kpa 60 kPa WOT control 1100 1400 3200 2050
1600 3000 2400 coated 1000 1250 2600 1300 800 1800 1600
[0106] The results in the foregoing three tables demonstrate the
coated engine producing reduced amounts of HC, CO and NO.sub.x in
exhaust emissions as compared to the engine in the uncoated
state.
Example 7
Surface Area Testing
[0107] For this experiment, an aluminum-sample 1 cm.times.2 cm
(thickness 0.8 mm) was coated on both sides according to the
procedure of Example 1, resulting in an approximately 10 .mu.m
thick coating comprising predominantly titanium dioxide with traces
of phosphorus, less than 10%.
[0108] The dry, coated sample was weighed. Liquid nitrogen was
adsorbed on the surface of the coated sample. The sample was then
heated and re-weighed. The weight loss (caused by desorbing
nitrogen) was determined. From the amount of desorbing nitrogen,
the specific surface area that was covered by nitrogen was
calculated by the BET method. This value was compared to the
geometrical surface area of the sample determined by the sample
dimensions. The coating increased the surface area by 146.times.
(times) equal to 14,600% versus a bare flat panel.
Example 8
Gasoline Engine Testing
[0109] Emissions of coated parts from Example 6 were retested and
compared to those of stock parts using the test procedure of
Example 6, modified in that the engine controller was used to
operate the engine in a normal closed-loop control mode. The
emission results are shown in Tables on the next page.
[0110] On average, the coated part set showed a 3% reduction in the
carbon monoxide emissions, 13% reduction in the hydrocarbon
emissions, and a 32% reduction in the NO.sub.x emissions compared
to the stock part set.
Example 8
Tables
TABLE-US-00010 [0111] TABLE 9 Total Hydrocarbon (ppm) Results for
Coated Parts and Stock Parts 1840 1840 1698 1698 2125 2125 1698
2268 1413 1413 1555 1983 1555 1840 1983 1555 rpm, rpm, rpm, rpm,
rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, 11 115
70 112 22 75 100 95 70 113 38 110 114 72 66 51 ft-lb ft-lb ft-lb
ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb
ft-lb ft-lb Stock 2269 1748 1347 1414 3131 1194 1075 984 1325 805
1690 1357 1222 1642 1499 1417 Coated 2700 1505 1153 1151 1710 1028
1042 911 1224 881 1409 1080 1155 1162 1104 1201
TABLE-US-00011 TABLE 10 Carbon Monoxide (%) Results for Coated
Parts and Stock Parts 1840 1840 1698 1698 2125 2125 1698 2268 1413
1413 1555 1983 1555 1840 1983 1555 rpm, rpm, rpm, rpm, rpm, rpm,
rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, 11 115 70 112 22
75 100 95 70 113 38 110 114 72 66 51 ft-lb ft-lb ft-lb ft-lb ft-lb
ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb
Stock 0.70 4.73 0.59 0.76 0.64 0.61 0.52 0.69 0.48 0.63 0.69 0.69
0.65 0.64 0.61 0.74 Coated 0.62 3.39 0.53 0.57 0.52 0.59 0.59 0.89
0.65 0.71 0.60 0.69 0.67 0.60 0.59 0.69
TABLE-US-00012 TABLE 11 NO.sub.x Results for Coated Parts and Stock
Parts 1840 1840 1698 1698 2125 2125 1698 2268 1413 1413 1555 1983
1555 1840 1983 1555 rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm, rpm,
rpm, rpm, rpm, rpm, rpm, rpm, rpm, 11 115 70 112 22 75 100 95 70
113 38 110 114 72 66 51 ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb
ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb ft-lb Stock 511 696
2323 2914 123 2023 2369 1823 1490 1803 2933 3432 2702 3876 3165
3206 Coated 182 704 1624 2033 104 1653 1776 1484 840 776 1955 2343
1485 2760 2099 2046
Example 9
Friction Reduction
[0112] Three aluminum alloy panels were selected for friction
comparisons: [0113] a panel having a titanium dioxide coating
as-deposited per Example 1; [0114] a panel having a titanium
dioxide coating as-deposited per Example 1 and subsequently
polished using fine grain abrasive of less than 300 grit and [0115]
as a benchmark, a panel coated with a commercially available
diamond like carbon coating (DLC) used in coating metal substrates
for high performance, low friction applications. Each panel was
subjected to friction testing per ASTM 1894 (2008) procedure with
the test panel sample as the sled and a 4.times.12 iron substrate
as the mating surface. The test results are shown in the table
below.
TABLE-US-00013 [0115] TABLE 12 Coating Static Friction Dynamic
Friction Titanium Dioxide 0.3925 0.3786 Coating Unpolished Titanium
Dioxide 0.1991 0.1948 Coating polished Diamond like carbon 0.2039
0.2003 coating (DLC)
The above test results show that the polished titanium dioxide
coating has coefficient of friction equal to or better than the
commercially available coating both in static and dynamic friction
tests.
Example 10
Doping of Titania Coating
[0116] Five aluminum alloy cylinder heads for a four stroke
gasoline internal combustion engine were selected for dopant
testing. One cylinder head was left uncoated. A second cylinder was
coated according to the invention with titania coating. A third
cylinder head was coated according to the invention with the
addition of 10 g/l cobalt carbonate dissolved in the electrolyte.
The fourth cylinder head, after coating with titania coating and
drying, was burnished with 50 nanometer Pt powder. This
nanoparticulate powder was rubbed into the dried titania coating
using a wool polishing wheel resulting in deposition in the pores
and on surface of the titania of about 0.2 grams of 50 nanometer Pt
powder. A fifth cylinder head was coated according to the invention
with the addition of 10 g/l sodium ammonium decavanadate dissolved
in the electrolyte.
[0117] The coated cylinder heads were assembled and tested
serially, meaning one after the other sequentially in time, into
the same four stroke engine, which did not have a catalytic
converter attached. With each coated cylinder head, the engine was
operated at various RPMs, under 80 to 100 percent load, and varied
air/fuel ratios as shown in FIG. 6a-6d. Emissions were tested
downstream of the combustion chamber at each engine operating
parameter, for each coated cylinder head. Test results showed
reduction in NO.sub.x emissions at lean, stoichiometric and rich
fuel mixtures can be achieved by addition of vanadium to the
titanium dioxide coating.
[0118] Although the invention has been described with particular
reference to specific examples, it is understood that modifications
are contemplated. Variations and additional embodiments of the
invention described herein will be apparent to those skilled in the
art without departing from the scope of the invention as defined in
the claims to follow. The scope of the invention is limited only by
the breadth of the appended claims.
* * * * *