U.S. patent application number 11/244945 was filed with the patent office on 2007-04-05 for engine wear and oil quality sensor.
This patent application is currently assigned to Honeywell International. Invention is credited to James ZT Liu, Aziz Rahman, Michael L. Rhodes.
Application Number | 20070074563 11/244945 |
Document ID | / |
Family ID | 37719348 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070074563 |
Kind Code |
A1 |
Liu; James ZT ; et
al. |
April 5, 2007 |
Engine wear and oil quality sensor
Abstract
A viscosity and corrosivity sensor apparatus includes a
substrate upon which one or more electrodes are configured. The
electrode(s) are exposed to a liquid, such as automotive oil. An
oscillator can be connected to the electrode, wherein the
oscillator assists in providing data indicative of the corrosivity
and data indicative of the viscosity of the liquid in contact with
the electrode(s). A viscosity and corrosivity sensor is therefore
provided in the same package.
Inventors: |
Liu; James ZT; (Hudson,
NH) ; Rahman; Aziz; (Sharon, MA) ; Rhodes;
Michael L.; (Richfield, MN) |
Correspondence
Address: |
Attorney, Intellectual Property;Honeywell International Inc.
101 Columbia Rd.
P.O. Box 2245
Morristown
NJ
07962
US
|
Assignee: |
Honeywell International
|
Family ID: |
37719348 |
Appl. No.: |
11/244945 |
Filed: |
October 5, 2005 |
Current U.S.
Class: |
73/54.24 |
Current CPC
Class: |
G01N 2291/0226 20130101;
G01N 2291/02818 20130101; G01N 2291/0423 20130101; G01N 27/06
20130101; G01N 2291/0256 20130101; G01N 2291/0422 20130101; G01N
2291/0258 20130101; G01N 2291/0255 20130101; G01N 2291/0427
20130101; G01N 33/2876 20130101; G01N 2291/101 20130101; G01N
29/2462 20130101; G01N 29/036 20130101; G01N 29/022 20130101 |
Class at
Publication: |
073/054.24 |
International
Class: |
G01N 11/10 20060101
G01N011/10 |
Claims
1. A viscosity and corrosivity sensor apparatus, comprising: a
substrate upon which at least one electrode is configured, wherein
said at least one electrode is exposed to a liquid; and an
oscillator connected to said at least one electrode, wherein said
oscillator assists in providing data indicative of said corrosivity
and data indicative of said viscosity of said liquid in contact
with said at least one electrode, wherein said data indicative of
said corrosivity is based on a frequency generated by said
oscillator in association with said substrate and said at least one
electrode, and said frequency is utilized to provide data
indicative of an etch rate associated with said at least one
electrode.
2. The apparatus of claim 1 further comprising a resistance
measurement component connected to said at least one electrode and
said oscillator, wherein said resistance measurement component
obtains conductivity information associated with said liquid.
3. (canceled)
4. (canceled)
5. (canceled)
6. The apparatus of claim 1 wherein said data indicative of said
viscosity of said liquid is based on an acoustic wave vibration
amplitude or a damping resistance generated by said oscillator in
association with said substrate and said at least one
electrode.
7. The apparatus of claim 1 wherein said liquid comprises oil.
8. The apparatus of claim 1 wherein said at least one electrode is
coated with at least one of the following: Cr, Ni, Fe, Mg, Al, Mn,
Zn, Ti, Sn, V, Co, Sc, or Pb.
9. The apparatus of claim 1 further comprising an antenna connected
to said apparatus, wherein said antenna wirelessly transmits and
receives data for the detection of said viscosity and said
corrosivity of said liquid.
10. A viscosity and corrosivity sensor system, comprising: a
substrate upon which at least one electrode is configured, wherein
said at least one electrode is exposed to an oil and wherein said
at least one electrode further comprises a top electrode and a
bottom electrode configured upon said substrate; an oscillator
connected to said at least one electrode, wherein said oscillator
assists in providing data indicative of said corrosivity and data
indicative of said viscosity of said oil in contact with said at
least one electrode, wherein said data indicative of said
corrosivity is based on a frequency generated by said oscillator in
association with said substrate and said at least one electrode,
and said frequency is utilized to provide data indicative of an
etch rate associated with said at least one electrode; and an
antenna connected to said system, wherein said antenna wirelessly
transmits and receives data for the detection of said viscosity and
said corrosivity of said oil.
11. The system of claim 10 wherein said oil comprises engine
oil.
12. The system of claim 10 wherein said at least one electrode is
coated at least one of the following: Cr, Ni, Fe, Mg, Al, Mn, Zn,
Ti, Sn, V, Co, Sc, or Pb;
13. The system of claim 10 wherein said at least one electrode and
said substrate comprise an acoustic wave sensor.
14. The system of claim 13 wherein said acoustic wave sensor
comprises a quartz crystal microbalance (QCM) sensor device.
15. The system of claim 13 wherein said acoustic wave sensor
comprises a Love wave sensor device.
16. The system of claim 13 wherein said acoustic wave sensor
comprises a shear horizontal surface acoustic wave (SH-SAW) sensor
device.
17. The system of claim 13 wherein said acoustic wave sensor
comprises an acoustic plate mode (APM) sensor device.
18. The system of claim 13 wherein said acoustic wave sensor
comprises a shear horizontal acoustic plate mode (SH-APM) sensor
device.
19. The system of claim 10 wherein said acoustic wave sensor
comprises a flexural plate mode acoustic wave sensor device.
20. A viscosity and corrosivity sensor method, comprising:
providing a substrate upon which at least one electrode is
configured, wherein said at least one electrode is exposed to an
oil and wherein said at least one electrode further comprises a top
electrode and a bottom electrode configured upon said substrate;
electrically connecting an oscillator to said at least one
electrode; and electrically connecting a resistance measurement
component to said at least one electrode and said oscillator,
wherein said resistance measurement component generates
conductivity information associated with said oil; and providing an
antenna in communication with said at least one electrode and said
substrate, wherein said antenna wirelessly transmits and receives
data indicative of said viscosity and said corrosivity of said oil,
such that said oscillator assists in providing data indicative of
said corrosivity and data indicative of said viscosity of said oil
in contact with said at least one electrode, such that said data
indicative of said corrosivity is based on a frequency generated by
said oscillator in association with said substrate and said at
least one electrode, and wherein said frequency also provides data
indicative of an etch rate associated with said at least one
electrode, and wherein said data indicative of said viscosity of
said oil is based on an amplitude or a phase generated by said
oscillator in association with said substrate and said at least one
electrode.
21. The method of claim 20 wherein said at least one electrode is
coated with at least one of the following: Cr, Ni, Fe, Mg, Al, Mn,
Zn, Ti, Sn, V, Co, Sc, or Pb.
22. The method of claim 20 wherein said at least one electrode and
said substrate comprise an acoustic wave sensor.
23. The method of claim 22 wherein said acoustic wave sensor
comprises a flexural plate mode acoustic wave sensor device.
Description
TECHNICAL FIELD
[0001] Embodiments are generally related to sensing devices.
Embodiments are also related to etch rate sensors. Embodiments are
additionally related to corrosivity and viscosity sensors.
Embodiments are also related to sensors for measuring engine wear
and lube oil quality data. Embodiments are additionally related to
acoustic wave sensors.
BACKGROUND
[0002] Acoustic wave sensors are utilized in a variety of sensing
applications, such as, for example, temperature and/or pressure
sensing devices and systems. Acoustic wave devices have been in
commercial use for over sixty years. Although the
telecommunications industry is the largest user of acoustic wave
devices, they are also used for sensor applications, such as in
chemical vapor detection. Acoustic wave sensors are so named
because they use a mechanical, or acoustic, wave as the sensing
mechanism. As the acoustic wave propagates through or on the
surface of the material, any changes to the characteristics of the
propagation path affect the velocity, phase and/or amplitude of the
wave.
[0003] Changes in acoustic wave characteristics can be monitored by
measuring the frequency or phase characteristics of the sensor and
can then be correlated to the corresponding physical quantity or
chemical quantity that is being measured. Virtually all acoustic
wave devices and sensors utilize a piezoelectric crystal to
generate the acoustic wave. Three mechanisms can contribute to
acoustic wave sensor response, i.e., mass-loading, visco-elastic
and acousto-electric effect. The mass-loading of chemicals alters
the frequency, amplitude, and phase and Q value of such sensors.
Most acoustic wave chemical detection sensors, for example, rely on
the mass sensitivity of the sensor in conjunction with a chemically
selective coating that absorbs the vapors of interest resulting in
an increased mass loading of the SAW sensor. Examples of acoustic
wave sensors include acoustic wave detection devices, which are
utilized to detect the presence of substances, such as chemicals,
or environmental conditions such as temperature and pressure.
[0004] An acoustical or acoustic wave (e.g., SAW/BAW) device acting
as a sensor can provide a highly sensitive detection mechanism due
to the high sensitivity to surface loading and the low noise, which
results from their intrinsic high Q factor. Surface acoustic wave
(SAW/SH-SAW) and amplitude plate mode (APM/SH-APM) devices are
typically fabricated using photolithographic techniques with
comb-like interdigital transducers (IDTs) placed on a piezoelectric
material. Surface acoustic wave devices may have a delay line, a
filter or a resonator configuration. Bulk acoustic wave devices are
typically fabricated using a vacuum plater, such as those made by
CHA, Transat or Saunder. The choice of the electrode materials and
the thickness of the electrode are controlled by filament
temperature and total heating time. The size and shape of
electrodes are defined by proper use of mask. Based on the
foregoing, it can be appreciated that acoustic wave devices, such
as a surface acoustic wave resonator (SAW-R), surface acoustic wave
filter (SAW-filter), surface acoustic wave delay line (SAW-DL),
surface transverse wave (STW), bulk acoustic wave (BAW), can be
utilized in various sensing measurement applications.
[0005] One promising application for micro-sensors involves oil
filter and oil quality monitoring. Except under very unusual
circumstances, oil does not "wear out", "break down" or otherwise
deteriorate to such an extent that it needs to be replaced. What
happens is that it becomes contaminated with water, acids, burnt
and un-burnt fuel, carbon particles and sludge so that it can no
longer provide the desired degree of protection for engine
components. Most oil filters in modern vehicles do not remove all
the contaminants. A filter can only remove solid particles above a
certain size. It cannot remove water, acids, or fuel dilution, all
of which pass through the full-flow filter just as readily as the
oil.
[0006] Motor oils are fortified with inhibitors to provide them
with a remarkable stability and resistance to oxidation and
deterioration. Such oils also contain acid neutralizing additives
to eliminate acidity or engine corrosion. There is a limit,
however, to the amount of contamination that even the best oil can
neutralize, and there comes a time when the only satisfactory
procedure is to drain the oil and replenish the engine with a new
charge. Thus, there arises the necessity for regular oil
changes.
[0007] The question is now "how often should engine oil be
changed?" Unfortunately, there is no simple answer to this
question. From the foregoing discussion, it is apparent that oil is
changed not because it has deteriorated, but because it has become
contaminated with various harmful substances, and that the greater
the rate at which such substances enter the oil, the sooner an oil
change is necessary.
[0008] Factors that influence the necessity of oil changes include
engine conditions and the method of engine operation. A vehicle
that is used mainly for short distance stop-start running will
require more frequent oil changes than one used for regular long
distance traveling. A warm engine with leaky piston rings, for
example, can contaminate the oil quicker than a new engine in good
mechanical condition.
[0009] It should also be kept in mind that a high performance
product (e.g., more additives) can handle more contaminates than
other products, and hence longer oil change periods can be
justified. As a final comment on this subject, it is worth
mentioning that it is normal for oil to darken in service. This is
not an indication that the oil has deteriorated. This merely
demonstrates that the oil has picked up contaminates and maintains
then in suspension, where they can do no harm, and where they can
be removed from the engine when the oil is changed.
[0010] In general, motor oil should perform two primary functions.
The oil must lubricate the engine and it also serve as a collector
of contamination. The contamination comes from the engine
combustion chambers where the gasoline is burned to produce powder.
There are two different types of fuel combustion in engines:
efficient combustion or clean burning; and inefficient combustion
or dirty burning.
[0011] When dirty combustion occurs in an engine, soot is not the
only product formed. Sticky, gummy products, which oil chemists
refer to as resins, and lead oxyhalides, may also form. Small
quantities of acidic combustion products may also be present. Water
is also a factor. For every gallon of gasoline burned, a little
over one gallon of water may be formed. Thus, during the burning of
gasoline in engines, a potential problem exists with respect to
soot, resins, acids, and water formation. If combustion products
function past the pistons and manage to penetrate the crankcase
oil, then a problem of dirty, contaminated oil will exist. If the
oil is allowed to become too dirty and contaminated, sludge
deposits can form, thereby resulting in plugged piston rings, oil
pump screens and oil filters. Engine wear and even engine damage
can then result.
[0012] A truck, bus or passenger car driven at highway speed on a
long trip can easily be lubricated and is the least demanding on an
oil of good quality. The really tough lubricating job is the
engine, which typically experiences only short runs with numerous
stops and starts, especially in cold weather. The worst conditions
for both the engine and the oil are the very conditions under which
the great majority of passenger cars are used most of the time.
[0013] Knowledge of the condition of oil in the field would
obviously be extremely beneficial information to truck fleet
maintenance managers and maintenance personnel. A permanently
installed oil quality sensor system can deliver the above
information.
[0014] Currently, fleets that do perform analysis on their lubes
utilize complete laboratory oil analysis. Primarily due to the cost
of laboratory analysis, however, these tests are only performed on
a routine basis, i.e. monthly or at each oil drain interval.
Laboratory oil analysis serves two basic functions. The first
function is to monitor the condition of the lube oil. Lube oil
within a healthy engine degrades at a slow rate with normal use.
Therefore, lab analysis can provide a forewarning and allow for
scheduling of routine oil drains. Complete lab analysis is very
effective in accomplishing this goal and first function.
[0015] It is at the second function, however, where lab analysis
fails and does not provide sufficient failure warnings such as
coolant leaks and stress related metal failures. Equipment is
normally sampled on a monthly basis and while this is a sufficient
interval to safely monitor the lube condition, many times this
frequency is not sufficient in detecting engine problems. After
all, analysis is used to detect the "Problem" before "Failure" and
"Downtime" can then occur.
[0016] An example of this situation is as follows. A company
samples its equipment on a monthly basis. On the first day of the
month a sample of the used oil is taken and sent to the lab for
analysis. On the second day, unknown to the maintenance personnel
and the oil lab, a coolant leak develops within the engine. The
next scheduled time for another complete laboratory analysis sample
to be taken is twenty-nine days away.
[0017] Within the next several days, the coolant leak degrades the
oil within the engine to the point that it causes wear to occur to
bearings and other parts of the engine. Somewhere between the
seventh and the tenth day the operator receives the results from
the lab sample taken on the first day of the month. These results
were taken before the problem occurred and shows no problems within
the engine and that the oil is suitable for further use. Two days
after receiving this report, the operator notices that the oil is
becoming cloudy and that the engine is making a little steam. The
routine monthly sampling of the used oil was not effective in
achieving its goal.
[0018] The need is immense for a permanently installed sensor
device that can determine the condition of the lube and equipment
which can be used on a more frequent basis than complete laboratory
analysis sampling. This need can be met by the use of the
disclosure here.
[0019] One promising application for micro-sensors involves oil
filter and oil quality monitoring. Diesel engines are particularly
hard on oil because of oxidation from acidic combustion. As the oil
wears, it oxidizes and undergoes a slow build-up of total acids
number (TAN). A pH sensor is capable of direct measurement of TAN
and an indirect measurement of total base number (TBN), providing
an early warning of oil degradation due to oxidation and excess of
water. The acids and water build-up is also related to the
viscosity of the oil.
[0020] Low temperature start-ability, fuel economy, thinning or
thickening effects at high and/or low temperatures, along with
lubricity and oil film thickness in running automotive engines are
all dependent upon viscosity. Frequency changes in viscosity have
been utilized in conventional oil detection systems. The frequency
changes caused by small changes in viscosity of highly viscous
liquids, however, are very small. Because of the highly viscous
loading, the signal from a sensor oscillator is very "noisy" and
the accuracy of such measurement systems is very poor. Moreover,
such oscillators may cease oscillation due to the loss of the
inductive properties of the resonator.
[0021] TAN is a property typically associated with industrial oils.
It is defined as the amount of acid and acid-like material in the
oil. Oxidation and nitration resins make up the majority of this
material. As the oil is used, acidic components build up in the
lubricant causing the TAN number to increase. A high TAN number
represents the potential for accelerated rust, corrosion and
oxidation and is a signal that the oil should be replaced. Critical
TAN numbers are dependant on oil type.
[0022] There is a need to provide a sensor apparatus which can be
utilized to monitor, in a sensitive manner, the etching effects of
etchants, such as acids contained in oils. There is also a need to
provide a sensor system which can monitor corrosion or degradation
of engines or other devices caused by exposure to such etchants. It
is believed that acoustic wave sensors may well be suited for such
monitoring as indicated by the embodiments described herein.
[0023] One of the problems with acoustic wave devices utilized in
oil monitoring applications, for example, is that frequency changes
caused by small changes in the viscosity of highly viscous fluids,
are very small. Because of highly viscous loading, the signal from
an oscillator associated with the acoustic wave sensor device is
very noisy and the accuracy of such measurements is very poor.
Moreover, the oscillators may cease oscillation due to the loss of
the inductive properties of the resonator.
BRIEF SUMMARY OF THE INVENTION
[0024] The following summary of the invention is provided to
facilitate an understanding of some of the innovative features
unique to the present invention and is not intended to be a full
description. A full appreciation of the various aspects of the
invention can be gained by taking the entire specification, claims,
drawings, and abstract as a whole.
[0025] It is, therefore, one aspect of the present invention to
provide for a combined viscosity and corrosivity sensor apparatus
and system.
[0026] It is another aspect of the present invention to provide for
a single sensor that can be utilized for multiple parameters
measurement.
[0027] It is another aspect of the present invention to provide for
a single sensor that accomplishes viscosity and etch rate
measurements.
[0028] The aforementioned aspects of the invention and other
objectives and advantages can now be achieved as described herein.
A viscosity and corrosivity sensor apparatus is disclosed, which
includes a substrate upon which one or more electrodes are
configured. The electrode(s) are exposed to a liquid, such as
automotive oil. An oscillator can be connected to the electrode,
wherein the oscillator assists in providing data indicative of the
corrosivity and data indicative of the viscosity of the liquid in
contact with the electrode(s).
[0029] A resistance measurement component is also connected to the
electrode and the oscillator. The electrodes can be provided in the
form of a top electrode and a bottom electrode configured upon the
substrate. Data indicative of the corrosivity is based on a
frequency generated by the oscillator in association with the
substrate and the electrode(s). Such a frequency is utilized to
provide data indicative of the etch rate associated with the
electrode(s). Data indicative of the viscosity of the liquid is
generally based on the amplitude or phase generated by the
oscillator in association with the substrate and the electrode(s).
Additionally, an antenna can be connected to the viscosity and
corrosivity sensor apparatus, wherein the antenna wirelessly
transmits and receives data associated with and/or indicative of
the detection of the viscosity and the corrosivity of the
liquid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The accompanying figures, in which like reference numerals
refer to identical or functionally-similar elements throughout the
separate views and which are incorporated in and form a part of the
specification, further illustrate the present invention and,
together with the detailed description of the invention, serve to
explain the principles of the present invention.
[0031] FIG. 1 illustrates a schematic diagram of a viscosity and
corrosivity sensor apparatus that can be implemented in accordance
with a preferred embodiment; and
[0032] FIG. 2 illustrates a side view of a viscosity and
corrosivity sensor system that can be implemented in accordance
with a preferred embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0033] The particular values and configurations discussed in these
non-limiting examples can be varied and are cited merely to
illustrate at least one embodiment of the present invention and are
not intended to limit the scope of the invention.
[0034] FIG. 1 illustrates a schematic diagram of a viscosity and
corrosivity sensor apparatus 100 that can be implemented in
accordance with a preferred embodiment. The viscosity and
corrosivity sensor apparatus 100 generally includes a substrate 102
upon which one or more electrodes 104, 106. Note that electrode 106
is generally composed of one or more electrode portions 105, 107,
and 109. Electrode 104 functions as a bottom electrode and
electrode 106 functions as a top electrode. A resistance
measurement component 112 is connected to the electrode portion 109
of the top electrode 106, while an oscillator 110 is connected to
the bottom electrode 104 and the resistance measurement component.
The viscosity and corrosivity sensor apparatus 100 can be adapted
for use in monitoring engine wear in an automotive system by
analyzing, for example, oil exposed to electrodes 104, 106 as
indicated in greater detail herein. Note that the electrodes 104,
106 can be formed on substrate 102 by various deposition
techniques, for example by physical vapor deposition (PVD),
chemical vapor deposition (CVD), and sputtering or electro chemical
deposition.
[0035] The resistance measurement component is generally utilized
to obtain conductivity information. The oscillator 110 is utilized
for viscosity and corrosivity measurement. Frequency is utilized to
obtain etch rate data or corrosivity data. Amplitude or phase
measurement is utilized to obtain viscosity data. The oscillator
110 thus assists in providing data indicative of the corrosivity
and/or viscosity of a liquid in contact with electrodes 104 and/or
106. A gap 108 is generally located between electrode portions 105
and 109 of electrode 106. Gap 108 can be implemented as, for
example, a 30 to 100 um gap for conductivity measurement purposes
associated with the resistance measurement component 112. Note that
oscillator 110 can be provided as a Surface Acoustic Wave (SAW) or
Bulk Acoustic Wave (BAW) oscillator, depending upon design
considerations.
[0036] FIG. 2 illustrates a side view of a viscosity and
corrosivity sensor system 200 that can be implemented in accordance
with a preferred embodiment. Note that in FIGS. 1-2, identical or
similar parts or elements are generally indicated by identical
reference numerals. System 200 incorporates the use of the
viscosity and corrosivity sensor apparatus 100 depicted in FIG. 1.
In system 200, the viscosity and corrosivity sensor apparatus 100
can be provided in the context of a bolt type sensor configuration
202 that is screwed directly into an engine 210. In this manner,
the viscosity and corrosivity sensor apparatus 100 is exposed to a
liquid 208 (e.g., oil) located in engine 210.
[0037] Note that engine 210 can be, for example, an automotive
engine. Additionally, an antenna 204 can be connected to the bolt
type sensor configuration 202 and hence the viscosity and
corrosivity sensor apparatus 100. Antenna 204 thus provides the
wireless transmission of data from and to the viscosity and
corrosivity sensor apparatus 100. A wire 206 can be connected to
other components not depicted in FIGS. 1-2, thereby providing for a
wired application, in addition to the wireless communications
capabilities offered by antenna 204. Wire 206 is optional,
indicating that system 200 can be wired or wireless in nature.
[0038] The viscosity and corrosivity sensor apparatus 100 depicted
in FIGS. 1-2 can be implemented in the context of an etch rate
sensor. Electrodes 104 and/or 106 can be coated with a Cr--Ni--Fe
alloy that mimics an alloy associated with engine 210, thereby
function as an engine wear indicator. The viscosity and corrosivity
sensor apparatus 100 reflects the amount that engine 210 is
attached by acids associated with liquid or oil 208. Thus, cold or
hot, powered or not, the viscosity and corrosivity sensor apparatus
100 is active at all times and provides accumulated data associated
with engine wear information.
[0039] Note that substrate 102 can be provided as a piezoelectric
substrate. Electrodes 104 and/or 106 can be provided as
interdigital transducers patterned on substrate 102. Such
interdigital transducers may launch and receive various acoustic
waves, including a surface acoustic wave (SAW), also known in the
art as a Rayleigh wave, and may also launch and receive several
acoustic plate modes (APMs), depending upon design
considerations.
[0040] Preferably, the selective material chosen to form the
electrodes 104 and/or 106 has a reduced reactivity such that
reaction products produced at the surface of the selective material
are removed by the etchant. By utilizing a selective material
having a reduced reactivity, the etched surface remains fresh
during sensor operation, that is, the etched surface remains free
from reaction products; unlike in conventional corrosivity sensors
in which metal oxide or metal sulfides remain on the electrode
surface reducing the active surface of the sensor apparatus 100.
Since the sensing device 100 has a fresh surface for new reactions,
the sensing device has a high sensitivity and a linear frequency
response throughout the life time of the sensor apparatus 100.
[0041] Electrodes 104 and/or 106 can be implemented as etchable
electrodes, depending upon design considerations. In one particular
embodiment, for example, system 200 can be designed for use in
automotive applications in which the etchant is degraded engine
oil, which contains weak acids. The etchable electrodes 104 and/or
106 for such an application can be fabricated by the deposition of
iron (Fe) onto the substrate 103. Iron (Fe) has a reduced
reactivity with the acids contained in the engine oil 208 such that
reaction products, such as Fe.sup.2+, are dissolvable in the
oil.
[0042] Furthermore, oxides which may form on the deposited iron due
to air exposure prior to the sensing device being placed in contact
with the oil 208, such as for example Fe.sub.2O.sub.3 or FeO, react
with the acids in the oil 208 in a similar manner as Fe. Other
suitable reduced reactivity materials which may be utilized to
fabricate the electrode 104 and/or 106 include iron (Fe), Nickel
(Ni), manganese (Mn), cobalt (Co), chromium (Cr), vanadium (V),
titanium (Ti), zinc (Zn), scandium (Sc), tin (Sn), magnesium (Mg)
and Aluminum (Al). Or alternatively, metal alloys rich in one or
more of these transition and non-transition metals.
[0043] Note that initially, the viscosity and corrosivity sensor
apparatus 100 can be placed in its operating position in which
electrode 104 and/or 106 is in contact with an etchant interest, in
this case engine oil 208. An oscillating acoustic shear wave can be
generated in the substrate 102 by applying an alternating voltage
across electrodes 104 and 106. The resonant frequency can be
initially measured. The etchant reacts with an etchable electrode
104 and/or 106 causing the mass loading of the viscosity and
corrosivity sensor apparatus 100 to change and increasing the
resonant frequency of the device over time. The resonant frequency
of the apparatus 100 can be measured again after a given time
period. The change in thickness of the selective material can be
calculated theoretically or experimentally. The etch rate of the
selective material can be determined by dividing the change in
thickness by the given time period.
[0044] In an alternative embodiment of FIGS. 1-2, electrode 104
and/or 106 can be fabricated from an inactive material, such as,
for example, Au, so that the oil 208 is unable to etch the
electrodes 104 and/or 106. Alternatively, the inactive material can
be copper (Cu), mercury (Hg), platinum (Pt), palladium (Pd), silver
(Ag), iridium (Ir) or other similar inactive metals. Also,
metal-nonmetal compounds (e.g., ceramic based on TiN, CoSi.sub.2,
or WC) can form the inactive electrode. Alternatively, the
viscosity and corrosivity sensor apparatus 100 can be designed such
that, in operation, the etchant is unable to contact another
electrode 104 or 106, thereby rendering at least one of electrodes
104 or 106 inactive. For example, the electrode 104 can be coated
with a protective layer, such as an insulating layer, to seal the
electrode 104 from the etchant or the viscosity and corrosivity
sensor apparatus 100 can be arranged such that only the selective
material comes in contact with the etchant. Such scenarios, of
course, represent alternative embodiments.
[0045] By preventing etching of one of the electrodes 104 or 106,
reduction of the Q factor and increase in motional resistance of
the device is limited. Since the substrate 102 (e.g., a quartz
substrate) may also be possibly inactive to the acids contained in
the oil 208, the viscosity and corrosivity sensor apparatus 100 can
be highly sensitive to the effects of the oil etching the electrode
104 and/or 106. Utilizing an etchable electrode and/or etchable
substrate instead of an inactive electrode and/or substrate is
possible but may result in a less sensitive device.
[0046] The viscosity and corrosivity sensor apparatus 100 is useful
for engine wear monitoring and oil quality detection because low
temperature startability, fuel economy, and thinning or thickening
effects at high/lower temperatures, along with lubricity and oil
film thickness in running engines are factors dependent upon
viscosity. Therefore, viscosity is a good indicator of an oil's
ability to function properly. The viscosity and corrosivity sensing
capabilities are thus provided in a single package. In a
multi-function sensor design, the viscosity and corrosivity sensor
apparatus 100 can be designed to detect both viscosity and
corrosivity. Additionally, system 200 can include pressure,
temperature, lubricity, conductivity, pH, humidity and/or
particulate measurement capabilities depending upon design
considerations.
[0047] The viscosity and corrosivity sensor apparatus 100 can be
implemented in the context of a permanently installed oil sensor
utilized for many different types of equipment such as, gasoline
engines, diesel engines, natural gas engines, hydraulic systems,
transmissions, compressors, turbines, and so forth. With monthly
laboratory analysis, one only has 12 chances a year to catch a
problem. Using a permanently installed oil sensor system (e.g.,
viscosity and corrosivity sensor apparatus 100) on a real time
basis, one can increase his or her chance of detecting an engine
oil problem.
[0048] A permanently installed oil sensor system or viscosity and
corrosivity sensor apparatus 100 can prove to be an effective
configuration for monitoring and determining the condition of both
lube and equipment. A sensor system or apparatus 100 may be
utilized for monitoring the total amount of contamination present
within lube oil by measuring the viscosity and TAN of the oil.
Although complete laboratory analysis delivers a more detailed
analysis of the oil, this sensor unit is highly efficient in
determining whether the oil and equipment is in normal operating
condition. When a problem with the equipment occurs, the unit may
easily detect this problem by detecting the elevated TAN and
viscosity of the oil due to the excess amount of contamination
present within the lube oil. The permanently installed oil sensor
system or apparatus 100 can be implemented as a simple monitoring
tool that allows the automobile driver or maintenance personnel to
know whether the equipment is within a "Normal" or "Abnormal"
operating condition.
[0049] It is contemplated that the use of the present invention can
involve components having different characteristics. It is intended
that the scope of the present invention be defined by the claims
appended hereto, giving full cognizance to equivalents in all
respects.
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