(12) United States Patent

(12) United States Patent
111111
(12)
(54)
11111111111111111111111
United States Patent
(10)
Matsiev et al.
(45)
~<\CHINE
FLUID SENSOR AND METHOD
(75) Inventors: Leonid Matsiev, San Jose, CA (US);
James Bennett, Santa Clara, CA (US);
Daniel M. Pinkas, Menlo Park, CA
(US); Mikhail Spitkovsky, Sunnyvale,
CA (US); Oleg Kolosov, San Jose, CA
(US); Shenheng Guan, Palo Alto, CA
(US); Mark Uhrich, Redwood City, CA
(US); G. Cameron Dales, Saratoga, CA
(US); John F. Varni, Los Gatos, CA
(US); Blake Walker, Eugene, OR (US);
Vladimir Gammer, San Francisco, CA
(US); Dave Padowitz, Mountain View,
CA (US); Eric Low, Berkeley, CA (US)
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Subject to any disclaimer, the tenn of this
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(21 ) Appl. No.: 10/452,264
(22) Filed:
(65)
Patent No.:
US 7,043,969 B2
Date of Patent:
May 16, 2006
(56)
(73) Assignee: Symyx Technologies, Inc., Santa Clara,
CA (US)
(*)
111111111111111111111111111111111
US007043969B2
(Continued)
Jun. 2, 2003
Prior Publication Data
US 2004/0099050 Al
Primary Examiner-Hezron Williams
Assistant Examiner-John Fitzgerald
(74) Attorney, Agent, or Firm-Senniger Powers
May 27,2004
Related U.S. Application Data
(60) Provisional application No. 60/419,404, filed on Oct.
18, 2002.
(51) Int. Cl.
GOIN 11116
(2006.01)
(52) U.S. Cl. .................... 73/54.41; 73/53.05; 73/64.42
(58) Field of Classification Search ............... 73/24.06,
73/31.06,30.04,32 A, 54.24, 54.38, 54.41,
73/61.49, 61.75; 422/68.1
See application file for complete search history.
(57)
ABSTR<\CT
A method for analyzing a fluid contained within a machine,
comprising the steps of providing a machine including a
passage for containing a fluid; placing a sensor including a
mechanical resonator in the passage; operating the resonator
to have a portion thereof translate through the fluid; and
monitoring the response of the resonator to the fluid in the
passage. A preferred sensor includes a tuning fork resonator.
13 Claims, 5 Drawing Sheets
US 7,043,969 B2
2
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Am Bamberger, P.E. Sixth Conference on Food Engineering, 1999 AIChE Amual Meeting, Dallas, Texas.
US 7,043,969 B2
5
"Micromachined viscosity sensor for real-time polymerization monitoring", O.Brand, 1.M. English, S.A. Bidstmp,
M.G. Allen, Transducers '97, 121-124 (1997).
"Frequency response of cantilever beams immersed in viscous fluids with applications to the atomic force microscope", 1.E. Sader, 1. Appl. Phys. 84, 64-76 (1998).
"Resonance response of scamling force microscopy cantilever", G.Y. Chen, R.J. Warmack, T. Thundat, and D.P.
Allison, Rev. Sci. Instnun. 65, 2532-2537(1994).
"Lecture notes on shear and friction force detection with
quartz tuning forks" Work presented at the "Ecole
Thematique du CNRS" on near-field optics, Mar. 2000, La
Londe les Maures, France by Khaled Karrai, Center for.
1. Sorab, G.S. Saloka: "Engine Oil Viscosity Swnsors Using
Disks of PZT Ceramic as Electromechanical Vibrators"
Society of Automotive Engineers SAE, No. 971702, 1997.
E. Bolnner, "Elemente der angewandten Elektronik", Aug.
1978, with English translation.
Wullner et aI., Multi-Function Microsensor for Oil Condition Monitoring Systems, pp. 1-5.
Hauptmann et aI., Ultrasonic Sensors for Process Monitoring and Chemical Analysis; State-of-the-Art and Trends,
1998, pp. 32-48.
Jakoby et aI., Viscosity Sensing Using a Love-wave Device,
1998, pp. 275-281.
Polla et aI., Processing and Characterization of Piezoelectric
Materials and Integration into Microelectromechanical Systems, 1998, pp. 563-597.
Pujari et aI., Reliable Ceramics for Advanced Heat Engines,
American Ceramic Society Bulletin, vol. 74, No.4, Apr.
1995, pp. 86-90.
Oden et aI., Viscous Drag Measurements Utilizing
Microfabricated Cantilevers, American Institute of Physics,
1996, pp. 3814-3816.
Merhaut, Theory of Electroacoustics, pp. 100 and 101.
Manalis et aI., Two-dimensional Micromechanical Bimorph
Arrays for Detection of Thermal Radiation, Appl. Phys.
Lett., vol. 70, No. 24, Jun. 16, 1997, pp. 3311-3313.
Lin et aI., Operation of an Ultra sensitive 30-MHz Quartz
Crystal Microbalance in Liquids, Analytical Chemistry, Vo.
65, No. 11, Jun. 1, 1993, pp. 1546-1551.
Li et aI., Electromechanical Behavior of PZT-Brass
Unimorphs, Joumal of the American Ceramic Society, vol.
82, No.7, 1999, pp. 1733-1740.
Landau et aI., Fluid Mechanics, pp. 96 and 97.
Cleland et aI., Fabrication of High Frequency Nonometer
Scale Mechanical Resonators from Bulk Si Crystals, App!.
Phys. Lett., vol. 69, No. 18, Oct. 28, 1996, pp. 2653-2655.
International Search Report mailed Jul. 9, 2004, PCTI
US2004/008531 (1012.l88WOl).
Ferry, Viscoelastic Properties of Polymers, Chapters 5-8, pp.
96-176.
Thompson M., Stone D., Surface-Launched Acoustic Wave
Sensors: Chemical Sensing and Thin-Film Characterization,
Apr. 23,1997,112 pages, ISBN: 0-471-12794-9, JOlnl Wiley
& Sons, New York.
Grate 1. w., Martin S. 1., White R. M., Acoustic
TSMSAWFPWAPM Wave Microsensors, Analytical Chemistry, Sep. 1, 1993, pp. 940A-948A, vol. 65, Nr. 21,
XP000414305, American Chemical Society, Columbus, US.
Benes E., Grosch! M., Burger W., SClnllid M., Sensors based
on piezoelectric resonators, Sensors and Actuators A, May 1,
1995, pp. 1-21, CH, vo!' 48, Nr.l, XP004303567, Elsevier
Sequoia S.A., Lausamle.
Martin S. 1., GranstaffY,E., Frye G. c., Characterization Of
A Quartz Crystal Microbalance With Simultaneous Mass
And Liquid Loading, Analytical Chemistry, Oct. 15, 1995,
pp. 2272-2281, vol. 63, Nr. 20, XP000577312, American
Chemical Society, Colmnbus, US.
Horine B. H.; Malocha D. c., Equivalent Circuit Parameter
Extraction of SAW Resonators, Dec. 4, 1990, pp. 447-482,
XPOI 00 10069 .
Ito H., Nakazawa M., An analysis of impedance-gas pressure characteristics of tuning fork-type quartz vacuum
gauge-the effects of the drag force and the viscous friction
of gas, Electronics, and Communications in Japan, Feb.
1991, pp. 10-18, Part 3, vol. 74, Nr. 2, XP009044733,
Fundamental Electronic Science.
Baltes H., Gopel w., Hesse 1., Acoustic Wave Sensors, 1996,
pp. 37-83, vol. 2, Chapter 2, ISBN: 3-527-29432-5, Sensors
Update, VCH, Weinheim.
Nomura, T. and M. Iijima, Electrolytis Determination of
Nanomolar Concentrations of Silver in Solution with a
Piezoelectric Quartz Crystal:, Analytiea Chimica Aeta,
1981, pp. 97-102,131, Elsevier Scientific Publishing Company.
U.S. App!. No. 09/174,856 entitled "Graphic Design of
Combinatorial Material Libraries" (Lacy, et al.) filed on Oct.
19, 1998.
Ulbricht, Helmar, Eningen, Crimpen-eine ausgereifte
AnschluBtechnik, XP-000902731.
International Search Report dated Jul. 12,2004 (PCTIUS031
32983), 7 pages.
* cited by examiner
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US 7,043,969 B2
US 7,043,969 B2
1
2
MACHINE FLUID SENSOR AND METHOD
resonator to have a portion thereof translate through the
fluid; and monitoring the response of the resonator to the
fluid in the passage or reservoir.
One embodiment of the invention is a method for analyzing a fluid contained within a vehicle. A tuning fork
resonator is operated at a frequency of less than 1 MHz
while the resonator is in contact with the fluid contained
within the vehicle. A response of the resonator is monitored.
Yet another method of the present invention is for analyzing a fluid of an automotive vehicle. A mechanical
resonator on a substrate having circuitry thereon is operated
at a frequency of less than about 1 MHz while the resonator
is in contact with the fluid of the automotive vehicle to have
a portion of the resonator translate through the fluid. A
response of the resonator is monitored.
Still another method of the invention is for analyzing a
circulating oil of a vehicle engine. An input signal is applied
to a tuning fork resonator on a substrate having circuitry
thereon at a frequency of less than about 100 kHz while the
resonator is in contact with the oil of the automotive vehicle
engine. A response of the resonator is monitored.
According to one preferred embodiment of the method, a
mechanical transducer is operated in a non-resonant mode
with at least a portion of the transducer being translated
through the fluid while a property such as mechanical
impedance or the like is measured preferably using the
monitored response.
The monitoring that occurs in the method above may also
employ suitable hardware package or configuration for
monitoring the change of frequency of the mechanical
resonator while maintaining the input signal to the resonator
as a constant. It may alternatively employ the monitoring of
the change in electrical feedback from the resonator while
maintaining a constant frequency.
In a particularly preferred embodiment wherein the input
signal is a variable frequency input signal and the monitoring step includcs varying the frequency of a variablc frcquency input sigual over a predetennined frequency range to
obtain a frequency-dependent resonator response of the
mechanical resonator.
Though other stmctures may be employed, in one highly
preferred embodiment the mechanical resonator is configured generally as a tuning fork, and thus preferably includes
at least two opposing free-ended tines that share a C01111110n
base.
The systems, methods and apparatus of the prcsent invention may further comprise other components, such as a
computer, a micro controller, an energy source (e.g., a
power, stimulus or excitation source) (e.g., for providing a
variable frequency input signal to the resonators), a device
for converting a signal drawn from a power source of a
vehicle into a variable frequency input sigual or the like.
CLAIM OF BENEFIT OF FILING DATE
The present application claims the benefit of the filing
date of U.S. Provisional Application Ser. No. 60/419,404
(filed Oct. 18, 2002), hereby incorporated by reference.
TECHNICAL FIELD
10
The present invention generally relates to the field of fluid
sensors and more particularly to an automotive fluid sensor
incorporating a mechanical resonator.
BACKGROUND OF THE INVENTION
The use of a quartz oscillator in a sensor has been
described in U.S. Pat. No. 6,223,589. U.S. Pat. No. 5,741,
961 also discloses a quartz resonator for use in an engine oil
sensor. Yet another piezoelectric sensor for engine oil is
disclosed in Hammond, ct aI., "An Acoustic Automotivc
Engine Oil Quality Sensor", Proceedings of the 1997 IEEE
International Frequency Control Symposium, IEEE Catalog
No. 97CH36016, pp. 72-80, May 28-30, 1997.
An improved system for measuring characteristics of
fluids using mechanical resonators is disclosed in commonly-owned U.S. Pat. Nos. 6,401,519; 6,393,895; 6,336,
353; and 6,182,499.
The use of acoustic sensors has been addressed in applications such as viscosity measurement in "Acoustic Wave
Microsensors," 1. W. Grate, et at, Anal. Chem. 65,
940A-948A (1993)); "Viscosity and Density Sensing with
Ultrasonic Plate Waves", B. A. Martin, S. W. Wenzel, and R.
M. White, Sensors and Actuators, A21-A23 (1990),
704-708; "Preparation of chemically etched piezoelectric
resonators for density meters and viscorneters", S. Trolier,
Q. C. Xu, R. E. Newnham, Mat.Res. Bull. 22, 1267-74
(1987); "On-line Sensor for Density and Viscosity Measurement of a Liquid or Slurry for Process Control in the Food
Industry", Margaret S. Greenwood, Ph. D. James R. Skorpik, Judith Ann Bamberger, P. E. Sixth Conference on Food
Engineering, 1999 AIChE A.l1llual Meeting, Dallas, Texas;
U.S. Pat. Nos. 5,708,191; 5,886,250; 6,082,180; 6,082,181;
and 6,311,549; and "Micromachined viscosity sensor for
real-time polymerization monitoring", O. Brand, 1. M.
English, S. A. Bidstrup, M. G. Allen, Transducers '97,
121-124 (1997).
Notwithstanding the above, there remains a need in the art
for alternative or improved sensors for analyzing fluids used
in machines (such as those in automotive systems), particularly for measuring changes in fluid amounts, changes in
fluid quality or combinations thereof.
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SUMMARY OF THE INVENTION
BRIEF DESCRIPTION OF THE DRAWINGS
55
The present invention meets the above need by providing
an improved fluid sensor and method of using the same,
premised upon the employment of sensitive mechanical
resonators, whose resonance performance can be monitored
and corrclated with fluid characteristics.
One embodiment of the present invention is an improved
method for analyzing a fluid contained within a machine,
comprising the steps of providing an machine including a
passage or rescrvoir for containing a fluid; placing a sensor
including a mechanical resonator in the passage or reservoir,
a size of the resonator preferably being substantially smaller
than a wave length of an acoustic wave; operating the
60
65
FIG. 1 shows a schematic view of one preferred system of
the present invention.
FIG. 2 shows a view of an illustrative resonator element
of the present invention.
FIGS. 3A-3G illustrate alternative stmctures for a resonator according to the present invention.
FIGS. 4A and 4B depicts an illustrative graphical display
of data in accordance with the present invention.
FIG. 5 is a schematic of one system employing a sensor
according to the present invention.
FIG. 6 is a schematic of an alternative system employing
a sensor according to the present invention.
US 7,043,969 B2
3
4
FIG. 7 illustrates au example of an equivalent circuit in
accordance with the present invention.
frequency of the mechauical resonator while maintaining the
input signal to the resonator as a constant. In another
embodiment, the monitoring step includes monitoring the
change in electrical feedback from the resonator while
maintaining a constant frequency. In yet auother instance,
the monitoring can be in the substantial absence of a signal,
where for example, the frequency change, the amplitude
decay or both of a resonator is observed over a period of time
after an input signal has been terminated.
The monitoring step will typically be guided by the nature
of any input signal. In one highly preferred embodiment, for
example, the monitoring step includes varying the frequency
of a variable frequency input signal over a predetermined
frequency rauge to obtain a frequency-dependent resonator
response of the mechanical resonator.
The sensor of the present invention preferably includes at
least one mechanical resonator, stillmore preferably one that
is capable of operating at a frequency range less than 1 MHz.
For example, a highly preferred resonator according to the
present invention is operated at a frequency of less than 500
kHz, more preferably less than 100 kHz, and even still more
preferably less than 75 kHz. A particularly preferred operational range is from about 1 kHz to about 50 kHz aud more
preferably about 5 to about 40 kHz. One highly preferred
embodiment operates at about 20 to about 35 kHz.
Though other resonators are also possible, a preferred
resonator is selected from the group consisting of tuning
forks, cantilevers, bimorphs, and unimorphs. A highly preferred resonator is a tuning fork resonator.
The resonator may be uncoated or coated or otherwise
surface treated over some or all of its exterior surface. A
preferred coating is a metal, plastic, ceramic or composite
thereof, in which the coating material is substautially resistant to degradation from the fluid to which it is to be exposed
or to surface build-up, over a temperature range of about
-10° to 100° c., and more preferably over a temperature
range of about -40° to 125 or 150 0 C.
The structure of the resonator may be any suitable structure taking into account the specific environment into which
it is to be introduced. As indicated, a preferred resonator is
a tuning fork, and thus will include a plurality of tines
projecting from a common base wherein the tines and base
may be arranged in a variety of configurations.
It will be also appreciated that the resonator ofthe present
invention, though potentially free standing, will generally be
carried by a suitable support medium, such as a connector
device for cOlmecting the resonator with a source of an input
signal, a device for monitoring the response of the resonator
to the signal, or both. The nature of the connector device
may vary from application to application. In one embodiment, it is a molded plastic (e.g., polyamide or the like)
device into which electrical wires cau be inserted in electrical communication with an inserted resonator. The connector may itself be configured for providing a suitable
attachment (e.g., using a quick-cOlmect mechanism) to a
surface of the machine into which it is introduced. Alternatively, the connector may be adapted for insertion into, or
otherwise may comprise, au integrated portion of a receptacle within the machine. It is also contemplated that the
connector device, the receptacle or both may include a chip
(e.g., a computer chip) for assisting in the communication of
date to other components described herein.
The present invention is not limited to the use of a single
resonator, but rather a plurality of resonators may be used.
There may be plural resonators that are operational over the
same or a different range of frequencies. There may be a
plurality of resonators each of a different material or having
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS
As will be appreciated from the description herein, the
present invention is directed primarily for analyzing one or
more fluids that are contained (whether in a sealed system,
an unsealed system or a combination thereof) in machines.
One highly preferred use of the present invention is the
analysis of one or more fluids (aud particularly the viscosity,
density or dielectric properties of one or more fluids) that are
used in transportation vehicles (including, but not limited to,
motorcycles, scooters, trucks, automobiles, construction
equipment, locomotives, airplaues, boats, ships, fann
machinery aud/or spacecraft), such as-fluids that are part of
a sealed and/or self-contained operating system, and more
preferably fluids that are part of a circulating or reservoir
fluid system, such as engine oiL fueL transmission oiL
radiator fluid, power steering oil, hydraulic fluid, refrigerant,
gear oil, brake fluid or the like. Accordingly, though illustrated herein in connection with such highly preferred use as
in a transportation vehicle, the present invention has a wide
variety of uses and the description is not intended to limit the
invention herein disclosed.
Tl1e present invention is particularly attractive because of
its ability to yield reproducible aud reliable fluid analysis,
particularly over a broad range of operation temperatures. It
also affords a relatively low cost alternative to other existing
sensors. In one particularly preferred embodiment, though
not required in every embodiment, the sensors of the present
invention cau be operated with success at a relatively low
frequency rauge.
One embodiment of the present invention is an improved
method for analyzing a fluid contained within a machine.
The method comprises the steps of providing a machine
including a passage or reservoir for containing a fluid;
placing a sensor including a mechauical resonator in the
passage or reservoir; operating the resonator to have a
portion thereof translate through the fluid; and monitoring
the response of the resonator to the fluid in the passage or
reservoir.
In another embodiment, the present invention is directed
to a method for sensing a fluid in a circulating or reservoir
fluid system, and includes the steps of providing a sealed
circulating or reservoir fluid system; incorporating a
mechanical resonator into the system, the mechauical resonator being in electrical communication with a source of an
input signal; coupling the mechanical resonator with diagnostics hardware; exposing the fluid of the circulating or
reservoir fluid system to the mechauical resonator; optionally applying an input signal; aud monitoring a response of
the mechanical resonator to the fluid with the diagnostics
hardware.
When employed, the input signal for the sensors of the
present invention may be any suitable signal. It may be
generated from a direct current source or an alternating
current source. It can be a constant frequency or a varying
frequency. In one highly preferred embodiment, the signal is
a varying frequency input signal. In another embodiment,
the signal is a result of a voltage spike, sine wave burst,
mechanical shock, pressure impulse, combinations thereof
or the like.
The step of monitoring may be performed under any of a
variety of different conditions. For example, in one embodiment, the monitoring step includes monitoring the change of
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US 7,043,969 B2
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a different coating or surface treatment. Plural resonators
may be carried by a COllllllon carrier, or by separate carriers.
Further, the resonators may be placed in the same general or
proximate region of the machine or at remote locations
relative to each other. An array of at least three resonators on
a common carrier may also be employed.
One particularly preferred embodiment involves the
incorporation of an oil sensor according to the present
invention into an automotive vehicle engine. Thus, one
possible approach is to locate the sensor in an engine oil pan.
However, a sensor may be located in any other suitable oil
passage in the engine.
The sensors of the present invention may be used continuously. Alternatively, a sensor can be disposable, so that
at predetermined intervals it is removed and replaced with a
different sensor.
Tl1e nature of the sensing that is performed by the sensor
can be varied depending upon the parameter or condition
that is desired to be monitored. Among the various applications are the use of the sensors herein for detecting the
presence or absence of a fluid, the level of a fluid, the
physical properties of a fluid, the presence of a contaminant
in the fluid, the fluid pressure, the fluid flow rate, the fluid
temperature, a change in physical property, condition or
parameter of a fluid or a combination thereof.
Of course, basic conditions of the fluid such as viscosity,
density, dielectric constant, conductivity or a combination
thereof may also be monitored and reported, and in a highly
preferred embodiment these are the properties that are
analyzed.
It is also possible that one of these latter basic conditions
is monitored using one or more of the present sensors and
the data output is processed by a suitable processing lmit,
which may apply an algoritlllll for correlating the outputted
data with the presence or absence of a fluid, the level of a
fluid, the replacement of a fluid, the presence of a contaminant in the fluid, the fluid pressure, the fluid flow rate, the
fluid temperature, a change in the physical property, condition or parameter of a fluid or a combination thereof.
The step of monitoring may be performed under normal
operating conditions of the machine into which the present
sensor is placed. The present invention is particularly advantageous in that it is believed operable over a broad range of
temperatures. Thus it is contemplated that the monitoring
step occurs at a temperature below -40 0 C. or possibly the
monitoring step occurs at a temperature above 125 or 1500
C. Generally the monitoring will occur between these
extremes.
It is also possible that during or following a monitoring
step the response of the sensor is compared against a known
reference value for the fluid. For example, in the context of
an automotive engine oil, fresh oil can be analyzed upon its
introduction into an engine. The observed response may then
be stored in memory or otherwise recorded. Data about a
particular fluid may be stored in memory of a suitable
processor, which can be retrieved in response to a triggering
event, such as input from a technician or reading of an
engine oil type by an optical detector, such as a bar code
scauner.
As the oil is used over a period of time, further analysis
can be made and the response compared with that of the
fresh oil. The identification of a diJl'erence between
responses could then be used as a trigger or other output
signal for communicating with diagnostics hardware, such
as one or both of an on-board diagnostic device or operator
interface (e.g., a dashboard display, an on board computer or
the like), which would provide an audible or visual signal to
the operator. It is also possible that a signal is outputted to
a remote telemetry device, such as one located external of
the vehicle. Thus, the signal that is outputted may be a
radio frequency signal or another wireless signal.
In one preferred embodiment, an output signal triggers an
engine control unit to alter one or more functions (e.g, air
intake; timing, or the like) of the engine or a combination
thereof.
Comparison of the response of the sensor to a reference
value from the original fluid is not the only approach for
generating a cOllllllunication to a user about the fluid condition. Certain expected values may be pre-progralllllled into
a device, which then compares the real-time values obtained
to the expected values. Moreover, it is possible that no
comparisons are made between real-time values and
expected values, but rather upon obtaining a certain threshold response, an output signal is generated for triggering a
user notification, for triggering an engine control unit to alter
one or more functions of the engine or a combination
thereof. It is also contemplated that a sensor in a controlled
fluid sample may be employed as an internal reference.
It is also possible that the response obtained from the
monitoring is stored in a memory, with or without communicating the response to the user. In this manner, a service
technician can later retrieve the data for analysis.
Though illustrated in comlection with an automotive
vehicle, as with all such examples herein, it should be
appreciated that such illustrations are not limited only to
automotive vehicles, but that, as with the example just
provided, like steps can be performed with other machines
and motorized vehicles for transportation, hauling, lifting or
perfornling mechanized work.
Referring to FIG. 1, there is illustrated one preferred
system 100 of the present invention. The system 100
includes a component 102 having passages 104 therein
through which a fluid is passed. Disposed within one of the
passages 104 is at least one sensor 106, which is in signaling
conllllunication with a computer, controller or other like
device 108. Preferably the sensor is also in signaling communication with a suitable power source 110. Diagnostics
hardware 112 optionally may be incorporated into the device
108, or maintained separately from it. Suitable readout
electronics may optionally be employed as part of or separate from the diagnostics hardware, e.g., including a readout
board for interfacing between the computer and the resonator. Alternatively, a readout device may be associated with
an instrument panel, such as for visual display to the
operator of the machine or vehicle.
It will be appreciated that the above configuration permits
the use of one or more measurement modes (which can be
measured using electrical techniques, optical techniques or
a combination thereof) such as excitation at one or more
frequencies around resonance, passive oscillations due to
ambient noise, vibrations, EMI or the time decay of oscillation after an electrical or mechanical impulse (e.g., a
voltage spike).
It should be appreciated that, by use of the ternl "passage"
herein, it is not intended to limit to strnctures that would be
defined by walls of a conduit. Passage may include a
reservoir, a well, an open-channel, a closed-chaunel, a
container, or the like. Thus, generally the term "passage"
herein contemplates any structure into which a fluid may be
introduced, contained temporarily, contained permanently,
passed through, removed from or otherwise.
Incorporation of a sensor into an automotive vehicle is in
accordance with the inventive principles herein. It will be
appreciated that the location of the resonator, or plurality of
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US 7,043,969 B2
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resonators, may be any snitable location for the intended
measurement, such as (among others) an engine oil pan, an
oil sump, a pump, an oil filter device, an engine head, an
engine block, a transfer case differential housing, a fluid line
or hose, a heat exchanger, a dipstick, a drain plug, a sensor
housing, or any other suitable location. Preferably the resonator is surface mounted, suspended or both, and positioned
so that is analytical capability is not substantially compromised by fluid velocity, turbulence, mechanical oscillations,
harmonics, vibrations or other extreme operating conditions.
If it is necessary to subject a sensor to an extreme operating
condition, then preferably the resonator will be suitably
housed (e.g., in an enclosed chamber) or otherwise shielded
as described herein.
Diagnostics hardware for use in monitoring the response
of a resonator according to the present invention may
comprise any suitable art-disclosed hardware, and the discussion herein is not intended as limiting. Without limitation, it is possible to employ hardware such as disclosed in
commonly owned u.s. Pat. Nos. 6,401,519; 6,393,895;
6,336,353; and 6,182,499, hereby incorporated by reference.
Another approach herein for measurement hardware is to
employ an electrical readout system in communication with
a computer and any resonators. For example, one or more
hard-wired circuits may be employed, or more preferably,
one or a plurality of printed circuit boards are employed to
comprise the readout board, thereby affording a compact and
reliable structure.
It should be appreciated that the discussion herein, in
conformance with the drawings is specifically addressed to
a system including one sensor adapted for analysis of a
single fluid. However, the invention is not intended to be
limited thereby, and it will be appreciated that the present
invention also covers the use of a plurality of different
sensors for measuring one fluid or a plurality of different
fluids.
FIG. 2 illustrates one preferred resonator comprising a
resonator element 114. The resonator element 114 preferably
includes a base 116 that has at least two tines 118 having tips
120 that project from the base. The shape of the tines and
their orientation relative to each other on the base may vary
depending upon the particular needs of an application. For
example, in one embodiment, the tines 118 are generally
parallel to each other. In another embodiment the tines
diverge away from each other as the tips are approached. In
yet another embodiment, the tines converge toward each
other. The tines may be generally straight, curved, or a
combination thereof. They may be of constant cross sectional thickness, of varying thickness progressing along the
length of the tine, or a combination thereof.
Resonator elements are suitably positioned in an element
holder that is built into the component 102. Alternatively, the
elements (with or without a holder) may be securably
attached to a wall or other surface defining one of the
passages 104. In yet another embodiment, the element is
suitably suspended within a passage 104, such as by a wire,
screen, or other suitable structure.
Element holders may partially or fully surround the
resonator elements as desired. Suitable protective shields,
baffles, sheaths or the like may also be employed, as desired,
for protection of the resonator elements from sudden
changes in fluid flow rate, pressure or velocity, electrical or
mechanical bombardment or the like. It should be appreciated that resonator elements may be fabricated from suitable
materials or in a suitable mauner such that they may be
re-useable or disposable.
One or both of the resonator element holders preferably is
configured with suitable hardware so that the resonator can
be counected in signaling comlllunication with an input
signal source, an output analyzer or a combination thereof.
One preferred construction thus contemplates a device in
which an exposed resonator is formed integrally with or
attached to a chip or like surface mountable substrate that
optionally has suitable circuitry built thereon. The chip, in
turn, may also include other sensing elements, or may be
attached in signaling comlllunication with another substrate
having sensing elements associated with it.
For exanlple, an existing device if or sensing fluid temperature, fluid level or both, may be adapted so that the
sensor of the present invention (such as one for sensing oil
condition) is housed along with the other sensing elements.
All of the elements may connect to a common carrier or
substrate, or be enclosed in a common housing (e.g., an
enclosure having one or more openings to allow a fluid to
pass through the enclosure). Of course, the sensor can also
be employed as a stand-alone sensor, and not need to be
housed with other sensing elements.
The materials of the resonators of the present invention
preferably are selected from at least one of piezoelectric
materials, electrostrictive materials, magstostrictive materials, piezoresistive materials, elasto-optic materials, anisotropic materials, or combinations thereof. By way of
example, the particular material may be a metallic material,
a crystalline material, a ceramic material or a combination
thereof. Examples of suitable materials include, without
limitation, quartz, lithillll1 niobate, zinc oxide, lead zirconate
titanate (PZT) or the like.
Any suitable technique may be used to manufacture the
resonator. For example, in one aspect, the resonators are
prepared by art-disclosed processing techniques, such as are
practiced in the semiconductor device fabrication industry.
Thus, a wafer may be provided, one or more layers deposited
thereon (e.g., by vapor deposition, sputtering, spin coating,
curtain coating, laminating wafer bonding, or the like). Steps
may be performed for shaping the resonator, such as photo lithography, laser cutting, etching, dicing or the like. Other
fabrication techniques, such as casting, molding, or the like
may also be used.
A highly preferred embodiment of the present invention
contemplates employing a tuning fork as a resonator. Preferably a two tine tuning fork is employed as the resonator.
However, the method and system of the present invention
can use any type of tuning fork resonator, such as a trident
(three-prong) tuning fork or tuning forks of different sizes,
without departing from the spirit and scope of the invention.
As indicated, the present invention is not intended to be
limited to tlming fork resonators. Other types of resonators
can be used, such as tridents, cantilevers, torsion bars,
bimorphs, membrane resonators, torsion resonators, unimorphs or combinations thereof. Still other types of resonators
can be used if modified from their conventional art disclosed
forms or if they are used in combination with a preferred
resonator. Examples of such resonators include thickness
shear mode resonators, length extension resonators, various
surface acoustic wave devices or combinations thereof. A
plurality of the same type or different types of resonators can
be used in combination. For example, a low frequency
resonator may be employed with a high frequency resonator.
In this malmer, it may be possible to obtain a wider range of
responses for a given sample.
Specifically it is preferred that the resonator of the sensors
of the present invention are mechanical resonators, and more
preferably flexural resonators, torsional resonators or a com-
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US 7,043,969 B2
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bination thereof. In one embodiment, preferred resonators
may be selected from the group consisting of tuning forks,
cantilevers, unimorphs, bimorphs, disc benders, and combinations thereof.
The size of the resonators can be varied. However, it
should be appreciated that one advantage of the present
invention is the ability to fabricate a very small sensor using
the present resonators. For example, one preferred resonator
has its largest dimension smaller than about 2 cm, and more
preferably smaller than about 1 cm. One preferred resonator
has length and width dimensions of about 2 nnn by 5 nnn,
and possibly as small as about 1 lll111 by 2.5 mm.
It is thus seen that a preferred resonator is configured for
movement of a body through a fluid. Thus, for example, as
seen in FIG. 2, the resonator 114 may have a base 116 and
one or a plurality of tines 118 projecting from the base. It is
preferred in one aspect that any tine 118 has at least one free
tip 120 that is capable of displacement in a fluid relative to
the base 116. FIG. 3A illustrates a cantilever 122 having a
base 124 and a free tip 126. Other possible structures, seen
in FIGS. 3B and 3C contemplate having a disk 128, a plate
130 or the like that is adapted so that one portion of it is
displaceable relative to one or more variable or fixed locations (e.g., 132 in FIG. 3B) (e.g. 132' in FIG. 3C). As seen
in FIG. 3D, in yet another embodiment a resonator 134 is
contemplated in which a shear surface 136 of the resonator
has one or more projections 138 of a suitable configuration
in order that the resonator may be operated in shear mode
while still functioning consistent with the flexural or torsional resonators of the present invention, by passing the
projections through a fluid.
In still other embodiments, and referring to FIGS. 3E~3G,
it is contemplated that a resonator 200 may include an
elongated member 202 supported on its sides 204 by a pair
of arms 206. As shown respectively in FIGS. 3E~3G, the
elongated member may be configured to oscillate side-toside, back and forth, in twisting motions or combinations
thereof.
The embodiment of FIG. 3B may be constructed as a
monolithic device. Yet another structure of the present
invention contemplates the employment of a lanlinate or
other multi-layer body that employs dissimilar materials in
each of at least a first layer and a second layer, or a laminate
comprised of layers of piezoelectric material of different
orientations or configurations. According to this approach,
upon subjecting one or more of the layers to a stimulus such
as temperature change, an electrical signal or other stimulus,
one of the materials will respond differently than the other
and the difference in responses will, in turn, result in the
flexure of the resonator.
As can be seen, the selection of the specific resonator
material, structure, or other characteristic will likely vary
depending upon the specific intended application. Nonetheless, it is preferred that for each application, the resonator is
such that one or a combination of the following features (and
in one highly preferred embodiment, a combination of all
features) is present:
1) a coating placed upon the resonator in thickness greater
than about O.lmicron that will not substantially detract
from resonance performance;
2) the resonator is operable and is operated at a frequency
of less than about 1 MHz, and more preferably less than
about 100 kHz;
3) the resonator is substantially resistant to contaminants
proximate to the sensor surface;
4) the resonator operates to displace at least a portion of
its body through a fluid; or
5) the resonator responses are capable of de-convolntion
for measuring one or more individual properties of
density, viscosity, or dielectric constant.
Also as discussed, in certain instances it is preferable for
the resonator to be optionally coated with a material to
change the performance characteristics of the resonator. For
example, the material can be a coating, such as to protect the
resonator from corrosion, degradation or other factors potentially affecting resonator performance. Alternatively, it may
be a specialized "functionalization" coating that changes the
resonator's response if a selected substance is present in the
composition being tested by the resonator. For example,
adding a hydrophobic or hydrophilic functionality to a
resonator tine allows the tine to attract or repel selected
substances in the fluid being analyzed, changing the mass,
effective mass, geometry or a combination thereof of the
tuning fork and thereby changing its resonance frequency.
Thus, in one particularly preferred embodiment the resonators used in the present invention include a surface that is
substantially resistant to contaminant build-up (e.g., impurities, soot, varnish, sludge, or the like) over all or a portion
thereof. Accordingly, it is preferred that at least a portion of
the resonator surface includes a material or texture that
exhibits a relatively low affinity to a contaminant, a relatively high affinity to the fluid under test, a relatively high
degree of hydrophobicity, or a combination thereof. Under
separate circumstances, however, it may be desirable that the
resonator surface include a material or texture that exhibits
a relatively high affinity to a contaminant, and a relatively
high degree of hydrophillicity.
It is possible to achieve this by the selection of a resonator
material that meets this requirement. Alternatively, a resonator may be suitably coated over at least a portion of its
surface with a coating for exhibiting high hydrophobicity, a
low coefficient of friction, or a combination thereof.
Examples of suitable coating materials include, for example,
fluoropolymers (e.g., PTFE), polyolefins (e.g., HDPE,
HDPP or the like), silicones, silanes, siloxanes, ceramics
(e.g., silicon nitride), diamond, or the like.
Coating thickness is not critical for most contemplated
applications. However, a preferred coating thickness ranges
from about O.l microns to about 10 microns. One embodiment contemplates a thickness of about 1 micron.
The resonators can also be functionalized with a polymer
layer or other selective absorbing layer to detect the presence of specific molecules. The coating or functionality can
be applied onto the resonator using any known method, such
as physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition
(PECVD), pulsed laser deposition (PLD), spraying or dipping. Further, the specific material selected for the coating or
functionality will depend on the specific application in
which the tuning fork resonator is to be used.
A single resonator may be coated or functionalized.
Alternatively, multiple resonators having the same or a
different structure but different coatings and/or functionalities can be incorporated into one sensor. For example, a
plurality of resonators may have the same structure bnt have
different functionalities, each functionality designed to, for
example, bond with a different target molecule. When the
sensor is used in such an application, one resonator can, for
example, be fi.mctionalized with a material designed to bond
with a first substance while another resonator can be functionalized with a material designed to bond with second
substance. The presence of either one of these substances in
the sample composition being tested will cause the corresponding resonator to change its resonance frequency. It is
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US 7,043,969 B2
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also possible to employ one or more sensors in which one
resonator is coated, and another is not coated.
As discussed elsewhere, the manner of operating the
sensors of the present invention may vary. In one embodiment, the sensor is operated continuously. In another, it may
be intermittently operated. In other embodiments, the sensor
may be operated only in preselected conditions, such as prior
to starting vehicle operation, upon starting vehicle operation,
during vehicle operation upon concluding vehicle operation,
while the vehicle travels at a substantially constant velocity,
while the vehicle accelerates or decelerates, or otherwise.
Under any or all of the above conditions, it will be
recognized that the integrity of the measurement may be
impaired as a result of some environmental condition, such
as temperature. The present invention thus also contemplates as one of its embodiments, the employment of an
envirOlmlent conditioner, pursuant to which at least the
environment proximate the location of the sensor is monitored or controlled to a predetennined condition. For
example, it may be preferred with certain sensors to maintain the optimal sensing capability to be within a certain
range of temperatures. A fluid that is outside of that range
preferably will be detected and a temperature regulating
device will heat or cool the fluid appropriately so that it can
be efficiently sensed by the resonators of the present invention.
It is also possible that the environmental conditioner is
operated to maintain the environment in a constant condition. In this mamler, it can be seen, for example, that it is
possible to employ a sensor of the present invention with a
suitable heater for heating a frigid fluid to a certain temperature and preferably maintaining the fluid at that temperature for the duration of a measurement.
The use of an environmental conditioner also offers the
advantage that certain properties of the sensed fluid that are
sensitive to environmental conditions (e.g., viscosity, which
is sensitive to temperature) will be relatively unaffected
during measurements, and provide a more reproducible and
reliable data.
Accordingly, in one preferred embodiment, the present
invention contemplates operation of the sensor while the
temperature of the sensed fluid is controlled at a substantially constant temperature by natural heat generated during
nonnal vehicle operation, operation with local heating ofthe
fluid or otherwise.
In certain instances, it is contemplated that data obtaining
from the sensors may be graphically displayed, such as on
a video display screen (e.g., a desk-top screen, a hand-held
screen, or both). It may also be outputted in printed format.
FIGS. 4A and 4B are exemplary displays of data obtained in
accordance with the present invention. Though illustrating
results comparing new and used engine oils, and different
types of oils, like results are believed possible for other
fluids, and at other frequencies.
Examples of suitable systems that may be employed
herein include the systems illustrated in FIGS. 5 and 6.
FIG. 5 illustrates a system 140 that employs a sweep
oscillator 142 in signaling conllllunication with a resonator
144. The signal generated from the resonator is transmitted
to an analog-to-digital converter 146. Data from another
sensor 148 (e.g., a temperature sensor) may also be sent to
the converter 146. The converter 146, the sweep oscillator
142 or both connnunicate with a suitable processor 150 (e.g.,
an embedded microcontroller), which in tum is in signaling
communication with one or both of an internal bus 152 or
external bus 154, via for example a suitable interface 156
(e.g., a CAN interface).
FIG. 6 is substantially identical as FIG. 5 (with like parts
denoted by like reference numerals), but fllrther includes a
suitable environmental conditioner 158 driven by a suitable
driver 160 in conllllunication with the processor 150.
It will be appreciated from the foregoing that, in one
preferred embodiment, the present invention is employed for
sensing viscosity of a machine fluid, and is founded upon
analysis of changes in resonance characteristics that occur
when the resonator is in contact with a fluid. The response
is thus correlated with one or more fluid properties. Without
intending to be bound by theory, to help with such a
correlation, in a highly preferred embodiment, applicable for
highly preferred resonators in accordance herewith, a mathematical or equivalent electrical circuit model can be constmcted that includes the mechanical and electrical characteristics of the resonator, the properties of the surrounding
fluid, and the coupling between resonator and fluid. Comparison of the model to measured data can help to yield the
properties of interest. The parameters of the model can be
found by fitting to the measured response using standard
data fitting methods, such as (without limitation) least
squares minimization. In one procedure, the parameters
corresponding to the resonator alone are first detennined by
calibration in air or vacunm. A second calibration in a liquid
of known properties such as viscosity, density, dielectric
constant or a combination thereof, gives parameters for
mechanical and electrical coupling between resonator and
liquid. With the model parameters then established, the
properties of other liquids can be determined. Data acquisition and analysis can be simplified for incorporation in a
fluid monitoring system.
An example of one such analysis is set forth in L. F.
Matsiev, "Application of Flexural Mechanical Resonators to
Simultaneous Measurements of Liquid Density and Viscosity", IEEE Ultrasonics Symposium Proceedings, pp.
457-460 (1999), hereby incorporated by reference. By way
of illustration, for the equivalent circuit depicted in FIG. 7,
it is assumed that Cs , Ro, are equivalent characteristics of
a preferred resonator in a vacuum, Cp is the equivalent
parallel capacitance, p is the liquid density, 11 is liquid
viscosity, CD is oscillation frequency.
Accordingly, it can be seen that viscosity and density can
be de-convoluted by the following:
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M=Ap. AZ=B'!P1l
The above is not intended as limiting of the present
invention. Other alternative models might be derived with
reference to publications such as "Frequency response of
cantilever beams immersed in viscous fluids with applications to the atomic force microscope", 1. E. Sader, 1. App!.
Phys. 84, 64-76 (1998); "Resonance response of scanning
force microscopy cantilever", G. Y. Chen, R. 1. Warnlack, T.
Thundat, and D. P. Allison, Rev. Sci. Instrum. 65,
2532-2537 (1994); and "Lecture notes on shear and friction
force detection with quartz tuning forks" Work presented at
the "Ecole Thematique du CNRS" on near-field optics,
March 2000, La Londe les Maures, France by Khaled
Karrai, Center for Nanoscience, Section Physik der LudwigMaximilians-Universitat Miinchen D-80539 Munchen, Germany, the teachings of which are hereby incorporated by
reference.
US 7,043,969 B2
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Further, it will also be appreciated that the above protocol
need not be performed in every instance. For example,
where the specifics of the resonator geometry and electronics are accurately known, a reduced set of measurements,
such as the frequency and amplitude of the resonance peak
and minimum could suffice to determine particular liquid
properties. In this case, simplified detector electronics and
analysis methods advantageously might be employed to
facilitate incorporation in a system for on-line or real time
fluid condition monitoring, which is also contemplated
herein.
The sensors in accordance with the present invention
advantageously provide excellent performance characteristics. Without limitation, for example, the sensors herein
require less than 5V AC of excitation voltage, and on the
order of less than 1 micro-amp current (e.g., about 0.1
micro-amps). Accurate measurements are obtainable in less
than one second, and often less than about 0.25 seconds. The
measurement range for viscosity is from about 0 to at least
about 20 cPs (and possibly as high as at least about 5000
cPs) at 1 g/cm3. The measurement range for density is from
about 0 to at least about 20 g/cm3 at 1 cPo Dielectric
constants are measurable over at least the range of about 1
to about 100. Resolution (density,viscosity) values of less
than 1% are also possible.
It will be further appreciated that functions or structures
of a plurality of components or steps may be combined into
a single component or step, or the functions or structures of
one step or component may be split among plural steps or
components. The present invention contemplates all of these
combinations.
It is understood that the above description is intended to
be illustrative and not restrictive. Many embodiments as
well as many applications besides the examples provided
will be apparent to those of skill in the art upon reading the
above description. The scope of the invention should, therefore, be detennined not with reference to the above description, but should instead be determined with reference to the
appended claims, along with the full scope of equivalents to
which such claims are entitled. The disclosures of all articles
and references, including patent applications and publications, are incorporated by reference for all purposes.
What is claimed is:
1. A method for analyzing a fluid contained within a
vehicle, the method comprising the steps of:
a) operating a !lUling fork resonator at a frequency of less
than 1 MHz while the resonator is in contact with said
fluid contained within said vehicle; and
b) monitoring a response of the resonator.
2. The method of claim 1 wherein said monitoring step
comprises monitoring the change of frequency of the tuning
fork resonator while maintaining an input signal to the
resonator as a constant.
3. The method of claim 1, wherein said monitoring step
comprises monitoring a change in electrical feedback from
the tuning fork resonator.
4. The method of claim 1. further comprising operating
said tuning fork resonator in a non-resonant mode wherein
at least a portion of the tuning fork resonator is translated
through said fluid.
5. The method of claim 1, wherein the response is at least
related to the viscosity of the fluid.
6. The method of claim 1. wherein the vehicle is an
automotive vehicle.
7. The method of claim 1. wherein the tuning fork
resonator is located in an engine oil pan of the vehicle.
8. The method of claim 1 further comprising the step of
mounting a sensor comprising said tuning fork resonator on
the vehicle.
9. The method of claim 1, wherein the operating step
comprises applying a variable frequency input signal to the
tuning fork resonator.
10. The method of claim 9, wherein said operating step
further comprises varying the frequency of the input signal
over a predetermined frequency range, and wherein said
monitoring step comprises obtaining a frequency-dependent
resonator response of the tuning fork resonator.
11. The method of claim 1 wherein the resonator comprises a resonator element made of a material selected from
piezoelectric materials, electrostrictive material, magneto
restrictive materials, piezoresistive materials, elasto-optic
materials, anisotropic material, or combinations thereof.
12. The method of claim 11. wherein the monitoring step
comprises monitoring a response of the tuning fork resonator while the resonator is located in a temperature controlled
region.
13. The method of claim 11, wherein said resonator
element comprises a piezoelectric material.
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