Note: Descriptions are shown in the official language in which they were submitted.
CA 02674254 2009-07-29
TIRE PRESSURE SENSOR
Technical Field
[0001] Pressure monitoring apparatus and systems are provided.
Particular embodiments provide apparatus for monitoring air pressure in
pneumatic tires.
Background
[0002] The air pressure in vehicle pneumatic tires should be
maintained within a particular range to protect against tire damage or
failure, and to promote safe and efficient operation of the vehicle. For
example, overinflated or underinflated tires may cause tire wear, internal
tire damage, increased risk of tire penetration by sharp objects, blowouts
and/or reduced vehicle fuel economy. A tire pressure monitoring system
(TPMS) can be used to monitor air pressure inside a pneumatic tire and to
generate an alert if the tire pressure falls outside of a desirable range for
the
tire. A TPMS may incorporate a tire pressure sensor placed inside a tire and
means for transmitting pressure information detected by the tire pressure
sensor to a receiver.
[0003] A TPMS may be used for monitoring air pressure in off-the-
road (OTR) pneumatic tires used on large off-road vehicles such as mining
trucks, construction vehicles or the like. The interior of OTR or other
pneumatic tires may have corrosive liquids or gases, due at least in part to
the presence of corrosive chemicals which are used to treat the tires to
facilitate mounting and dismounting of the tires to wheels. Tire pressure
sensors placed inside the tires may be exposed to corrosive liquids or gases
which may corrode the sensor components, such as the sensor's electronic
components and circuitry. Such corrosion may lead to failure of the tire
pressure sensor.
[0004] To protect against corrosion (such as may be caused by the
corrosive interior of OTR tires), some tire pressure sensors have a housing
for encasing the sensor electronic components and circuitry. An opening is
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provided in the housing, and a filter covers the opening. The filter permits
only gases (e.g. the tire's pressurized air), and not liquids, to pass through
the opening to a pressure transducer contained inside the housing.
However, corrosive gases contained in the tire may pass through the filter,
along with the tire's pressurized air, thereby causing damage to the sensor
electronic components and circuitry in the housing.
[0005] There is a general desire to provide tire pressure sensors which
overcome or at least ameliorate these and/or other drawbacks.
Brief Description of Drawings
[0006] In drawings which illustrate non-limiting embodiments,
Figure 1 is an oblique top perspective view of a tire pressure sensor
according to one embodiment;
Figure 2 is a sectional view taken along line 2-2 of Figure 1 showing
the tire pressure sensor mounted to a vehicle tire by way of a patch mount;
and
Figure 3 is an oblique bottom exploded view of the Figure 1 tire
pressure sensor and a patch mount.
Description
[0007] Throughout the following description, specific details are set
forth in order to provide a more thorough understanding to persons skilled
in the art. However, well known elements may not have been shown or
described in detail to avoid unnecessarily obscuring the disclosure.
Accordingly, the description and drawings are to be regarded in an
illustrative, rather than a restrictive, sense.
[0008] Figures 1, 2 and 3 illustrate a tire pressure sensor 100
according to a particular embodiment, for placement in an interior 152 of a
pneumatic tire 150, such as an OTR tire used in mining trucks, construction
vehicles or the like. Sensor 100 incorporates a housing 102. In the
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illustrated embodiment, and as best seen in Figures 2 and 3, housing 102 is
formed of a base or casing 123 and a cover 125 which are coupled together.
Sensor 100 may be installed in tire 150 by way of a patch mount 140
attached to tire 150 as shown in Figure 2. Patch mount 140 incorporates a
threaded rod 144 mounted to and extending from a base plate 146. Base
plate 146 is mounted to a flexible patch 148 which in turn is attached to the
inside surface of tire 150. In the illustrated embodiment, a layer of
adhesive 149 attaches flexible patch 148 to tire 150. To install sensor 100
in tire 150, sensor 100 is positioned relative to patch mount 140 so that rod
144 is received within a corresponding threaded bore 142 extending
through cover 125 of housing 102. Sensor 100 is then screwed onto
rod 144 (i.e. by rotating sensor 100 in the screw-tightening direction so as
to cause rod 144 to be screwed into bore 142). In the illustrated
embodiment, rod 144 has male threads and bore 142 has corresponding
female threads.
[0009] In the illustrated embodiment, base 123 of housing 102 has a
cylindrical portion 124 defining a receptacle 124A for accommodating the
components of sensor 100 (as described in more detail below). Cover 125
of housing 102 has a frustoconical portion 126 defining a receptacle 126A
for accommodating a flexible membrane 114 (as described in more detail
below). Base 123 of housing 102 has a flanged rim 127 extending around
the periphery of an opening 124B of cylindrical portion 124. Cover 125 of
housing 102 has a flanged rim 128 extending around the periphery of the
wider end of frustoconical portion 126. As shown in Figure 2, when base
123 and cover 125 are assembled to form housing 102, flanged rims 127
and 128 are aligned with, and abut against one other. Screws, bolts or other
fasteners 129 may be inserted through flanged rims 127 and 128 at
peripherally spaced apart locations to couple base 123 to cover 125. In
particular embodiments, base 123 is formed of DelrinOO acetal resin, and
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cover 125 is formed of aluminum or brass. Materials such as Delrin
acetal resin, aluminum, and brass have high gas and liquid impermeability.
[00101 In the illustrated embodiment, sensor 100's electronic
components and circuitry include a pressure transducer 104, a control and
processing unit 105 (having a programmable controller and processor), a
transmitter 106, an antenna 107, a battery 108, and connecting circuitry
board 109, all located within housing 102. More particularly, pressure
transducer 104, control and processing unit 105, transmitter 106, antenna
107, battery 108 and circuitry board 109 are accommodated within
receptacle 124A of base 123 of housing 102. Pressure transducer 104 is
electronically coupled to transmitter 106 through circuitry on circuitry
board 109. In the illustrated embodiment, control and processing unit 105
is electronically coupled between pressure transducer 104 and transmitter
106. Pressure transducer 104 generates signals (e.g. electronic analog
signals) indicative of the air pressure detected by pressure transducer 104.
Such signals are processed by control and processing unit 105 and the
processed signals are transmitted by transmitter 106 by way of antenna 107
to a receiver (not shown) external to tire 150.
[00111 The signals generated by pressure transducer 104 may translate
into pressure readings which are higher or lower than the actual air pressure
in tire interior 152 (e.g. the signals may be skewed). Control and
processing unit 105 may be configured to process (e.g. adjust) the signals
generated by pressure transducer 104 so that the processed signals translate
into pressure readings which are indicative of air pressure in tire interior
152. Such processing may be performed in accordance with a calibration
curve for sensor 100. The calibration curve may be a linear or non-linear
function. Over the life span of sensor 100, sensor 100 may be re-calibrated
by adjusting or re-programming the calibration curve. For example, over
time, membrane 114 (as described in more detail below) may lose its
elasticity, thereby affecting the signals generated by pressure transducer 104
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and requiring adjustment of the calibration curve to maintain or improve
accuracy in sensor 100's pressure readings. Control and processing unit
105 advantageously permits the on-board calibration of sensor 100's
pressure readings as determined from signals generated by pressure
transducer 104.
[0012] Control and processing unit 105 may comprise one or more
microcontrollers, one or more microprocessors, one or more
field-programmable gate arrays (FPGA), application-specific integrated
circuits (ASIC), logic circuits combinations thereof or any other suitable
processing unit(s) comprising hardware and/or software capable of
functioning as described herein.
[0013] Battery 108 is connected to deliver electrical power to pressure
transducer 104, control and processing unit 105, and transmitter 106. In
particular embodiments, battery 108 is a 3.6 V lithium inorganic battery. In
some embodiments, more than one battery 108 is provided in sensor 100.
For example, one battery 108 may be provided to deliver electrical power to
transmitter 106 and another battery 108 may be provided to deliver
electrical power to pressure transducer 104 and control and processing unit
105.
[0014] In particular embodiments, control and processing unit 105 is
configured to control the transmission of signals by transmitter 106. For
example, the frequency of transmission of signals by transmitter 106 may be
controlled by control and processing unit 105 to regulate power
consumption of battery 108 by transmitter 106.
[0015] A pressurized compartment 112 is contained within housing
102 and is sealingly covered by flexible membrane 114, which is spaced
apart from inside surface 103 of cover 125. Membrane 114 is made of a
flexible material which is impermeable to gases and liquids so as to protect
the sensor electronic components and circuitry from corrosive gases and
liquids present in tire interior 152, as well as to maintain the pressure
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sensitivity of tire pressure sensor 100 (e.g. by inhibiting de-pressurization
of compartment 112). In particular embodiments, membrane 114 is made of
Viton fluoroelastomer, a fluorocarbon-based synthetic rubber.
[0016] Membrane 114 extends across, so as to completely cover,
opening 124B of cylindrical portion 124 of base 123. In the illustrated
embodiment, a peripheral portion 114A of membrane 114 is positioned
between flanged rim 127 of base 123 and flanged rim 128 of cover 125 (see
Figure 2). Membrane 114 is secured between base 123 and cover 125 when
flanged rims 127, 128 are coupled to one another with screws 129. Screws
129 may extend through flanged rims 127, 128 and through peripheral
portion 114A of membrane 114. Figure 3 shows a plurality of screw-
receiving apertures 130 defined in peripheral portion 114A of membrane
114. Apertures 130 may be formed by driving screws 129 through
membrane 114 during assembly of sensor 100.
[0017] At least one inlet port 110 extends through cover 125 to allow
pressurized air within tire interior 152 to contact membrane 114. In the
illustrated embodiment, four inlet ports 110 extend through cover 125.
Providing a plurality of inlet ports 110 is advantageous in the event that an
inlet port 110 becomes clogged with dirt or other impurities trapped within
tire interior 152.
[0018] Membrane 114 extends outwardly in a direction 118 away
from an interior of compartment 112 and toward the inside surface 103 of
cover 125. The tire pressure (i.e. air pressure in tire interior 152)
determines
the extension of membrane 114 in outward direction 118, which in turn
governs the air pressure in compartment 112. The air pressure in
compartment 112 is therefore indicative of tire pressure. More specifically,
membrane 114 extends outwardly by a greater amount if tire pressure is
relatively low (as shown by stippled line 131 representing a relatively more
extended position of membrane 114 in Figure 2). In such a position, the air
pressure in compartment 112 is relatively decreased. Membrane 114
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extends outwardly by a lesser amount if tire pressure is relatively high (as
shown by stippled line 132 representing a relatively less extended position
of membrane 114 in Figure 2). In such a position, the air pressure in
compartment 112 is relatively increased.
[0019] Particular embodiments of sensor 100 are capable of measuring
tire pressure ranging between 13.8 kPa (2 pounds per square inch or PSI)
and 1462 kPa (212 PSI) or higher (gauge). To enable this desired range of
pressure sensitivity, a sufficient quantity of air or gas is contained within
compartment 112 so that an outward extension of membrane 114 in
direction 118 is maintained when tire pressure is between 13.8 kPa (2 PSI)
and 1462 kPa (212 PSI) or higher (gauge). Membrane 114 will "bottom-
out" or become flat at a threshold tire pressure (i.e. at the threshold tire
pressure, membrane 114 will be compressed to a non-extended position
such that any increase in tire pressure above the threshold has minimal or
no effect on membrane 114; sensor 100 thereby loses sensitivity to any
increase in tire pressure above the threshold). In particular embodiments,
compartment 112 contains a sufficient quantity of air or gas so that it does
not bottom out until a threshold tire pressure of 1462 kPa (212 PSI) (gauge)
or higher is reached.
[0020] Other embodiments of sensor 100 are capable of measuring tire
pressure ranging between 13.8 kPa (2 PSI) and 1034 kPa (150 PSI) (gauge).
Therefore, compartment 112 contains a sufficient quantity of air or gas so
that it does not bottom out until a threshold tire pressure of 1034 kPa 150
PSI (gauge) is reached. Certain other embodiments of sensor 100 may be
designed to have a different pressure sensitivity range appropriate for the
kind of pneumatic tires for which the sensor is used.
[0021] As best seen in Figure 2, a first conduit or air passage 116
extends from pressure transducer 104 to compartment 112. Conduit 116
allows pressurized air contained within compartment 112 to flow to
pressure transducer 104, thereby allowing pressure transducer 104 to detect
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the air pressure in compartment 112. In particular embodiments, conduit
116 is a rigid or semi-rigid pipe having an 18-gauge bore (about 1.02 mm or
0.040 inch diameter).
[0022] Over an extended period, gas may diffuse through supposedly
"gas-impermeable" and "liquid-impermeable" materials such as steel,
aluminum, brass, and plastics such as Delrin acetal resin. Therefore,
corrosive gases within tire interior 152 may eventually diffuse through the
walls of housing 102 or membrane 114 despite the "gas-impermeable" and
"liquid-impermeable" characteristics of housing 102 and membrane 114.
Moreover, gas initially contained within compartment 112 may diffuse into
the walls of housing 102, the sensor electronic components and circuitry, or
other components of sensor 100, thereby decreasing the air pressure in
compartment 112 (and eventually de-pressurizing compartment 112).
Decreased air pressure in compartment 112 affects the accuracy of pressure
readings and causes membrane 114 to bottom out at a lower threshold tire
pressure.
[0023] To provide a barrier to gas diffusion, prolong sensor 100's
operational life span, and maintain sensor 100's pressure sensitivity, sensor
electronic components and circuitry are potted in epoxy 120. Prior to
pouring liquid epoxy 120, liquid epoxy 120 is treated to remove gases from
the epoxy (e.g. induced gases or other gases, which may be present from the
manufacturing of the epoxy). Otherwise, gases remaining in the epoxy may
result in undesirable air pockets once the epoxy is cured. According to
some embodiments, liquid epoxy 120 is treated by placing the liquid epoxy
in a vacuum chamber (a chamber maintained at less than atmospheric
pressure). In some embodiments, the vacuum chamber is maintained at a
pressure of 50 kPa (7.3 PSI) (absolute) or less. In particular embodiments,
the vacuum chamber is maintained at a pressure of 7 kPa (1 PSI) (absolute)
or less.
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[00241 After liquid epoxy 120 has been treated to remove gases,
epoxy 120 is poured into receptacle 124A of base 123 to cover and fill any
spaces surrounding the sensor electronic components and circuitry. Epoxy
120 also fills the spaces surrounding conduit 116 but does not enter conduit
116. Once poured, epoxy 120 may further be treated by placing sensor 100
(containing epoxy 120) in a vacuum chamber. Epoxy 120 is then cured to
form a hard protective material encapsulating the sensor electronic
components and circuitry. In some embodiments, cured epoxy 120 has a
hardness of at least D30 durometer. In particular embodiments, cured
epoxy 120 has a hardness of at least D90 durometer. Generally, the greater
the hardness of epoxy 120, the greater is its resistance to gas diffusion or
gas solubility.
[00251 The hardness of epoxy 120 may render the sensor electronic
components and circuitry susceptible to shearing away from circuitry
board 109 due to the thermal expansion or contraction of epoxy 120 (which
may result from temperature fluctuations in the vehicle tire during operation
of the vehicle). Generally, the greater the hardness of epoxy 120, the
greater is the tendency that thermal expansion or contraction of epoxy 120
will lead to sensor-damaging shearing of the sensor electronic components
and circuitry. In particular embodiments, to inhibit shearing, the sensor
electronic components and circuitry are coated with rubber 122 (see Figures
2 and 3) prior to encapsulating the sensor electronic components and
circuitry in epoxy 120. In particular embodiments, rubber spray coating is
applied to surface-mount components of the sensor electronic components
and circuitry (e.g. pressure transducer 104, control and processing unit 105,
transmitter 106, antenna 107). Rubber coating 122 is flexible and is
capable of absorbing some of the shearing stresses which would otherwise
be applied to the sensor electronic components and circuitry as a result of
the thermal expansion or contraction of epoxy 120.
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[0026] As seen in Figure 2, conduit 116 extends from compartment
112, through epoxy 120 and rubber coating 122, to pressure transducer 104.
Providing conduit 116 through epoxy 120 and rubber coating 122 to
pressure transducer 104 advantageously allows for a protective layer of
epoxy 120 to surround pressure transducer 104 and other sensor electronic
components and circuitry.
[0027] Pressure transducer 104 may incorporate a diaphragm sensitive
to changes in air pressure in conduit 116 and compartment 112. The
diaphragm deflects by an amount which depends on the air pressure in
conduit 116 and compartment 112 which is imposed on one side of the
diaphragm, relative to the pressure on the other side of the diaphragm. The
deflection of the diaphragm is detected by a sensor and converted into
electronic signals which are processed by control and processing unit 105
(as discussed above). The processed signals are transmitted by transmitter
106 to a receiver. In particular embodiments, pressure transducer 104 is a
piezoelectric sensor. In other embodiments, pressure transducer 104 may
comprise any suitable pressure transducer for detecting air pressure in
conduit 116 and compartment 112, such as a strain gage sensor, variable
capacitance sensor, microelectromechanical sensor, fiber optic sensor, or
the like.
[0028] A second conduit is optionally provided in the sensor to vent
gas which may leak from sensor battery 108. Sensory battery 108 may have
a tendency to leak gas, given its restrictive environment (i.e. the battery is
potted in epoxy 120 within housing 102, providing little or no expansion
room for the battery; also the battery operates within pressurized tire
interior 152). To protect the sensor electronic components and circuitry
from the corrosive effects of leaked battery gas, the leaked gas may be
vented away from such components and circuitry. For example, leaked
battery gas may be carried away from the battery and the other sensor
electronic components and circuitry by way of a conduit. The conduit may
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carry the gas to a compartment (e.g. charcoal cannister), where the gas is
then trapped. In the illustrated embodiment, a second conduit or air passage
136 extends from a location proximate to battery 108 to compartment 112
(see Figure 2). Conduit 136 carries gas which may leak from battery 108 to
compartment 112. The leaked battery gas is trapped in compartment 112,
away from the sensor electronic components and circuitry, thereby
protecting such sensor components from the potentially corrosive effects of
battery gases.
[0029] Leaked battery gas that is trapped in compartment 112
increases the air pressure in compartment 112, thereby affecting the
pressure readings. However, as only a small quantity of battery gas tends to
be leaked and trapped in compartment 112, the resulting effect on pressure
readings is generally negligible. At lower tire pressures (e.g. pressures
below 34.5 kPa (5 PSI) (gauge)), the trapped leaked battery gas in
compartment 112 results in a greater percentage error in pressure readings
than at higher tire pressures (e.g. pressures above 34.5 kPa (5 PSI) (gauge)).
However, at such lower tire pressures, the vehicle tire would be considered
underinflated and the effects on pressure readings (even significant
percentage errors) would be considered irrelevant. For example, some types
of vehicle tires are considered underinflated if tire pressure is below 207
kPa (30 PSI) (gauge). Other types of vehicle tires are considered
underinflated if tire pressure is below 552 kPa (80 PSI) (gauge).
[0030] One or more grooves, cavities, indentations, recesses, ridges,
protrusions or the like are optionally provided on an interior surface of
cylindrical portion 124 of base 123 of housing 102. Such features increase
the contacting surface area between epoxy 120 and the interior surface of
cylindrical portion 124, thereby helping epoxy 120 to be more securely
retained within base 123. For example, in the illustrated embodiment (see
Figure 2), a circumferential groove 138 is defined in the interior surface of
cylindrical portion 124. Groove 138 provides a space which may be filled
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with liquid epoxy 120 to facilitate adhesion of epoxy 120 to cylindrical
portion 124 once epoxy 120 has been cured.
[0031] To assemble sensor 100 according to the illustrated
embodiment, sensor 100's electronic components and circuitry (including
pressure transducer 104, control and processing unit 105, transmitter 106,
antenna 107, battery 108 and connecting circuitry board 109) may be
coupled together, or provided as a pre-assembled unit (see Figure 3), and
placed in receptacle 124A of cylindrical portion 124 of base 123. First
conduit 116 and second conduit 136 are attached to their respective points
of attachment near or on pressure transducer 104 and battery 108. Liquid
epoxy 120 (which has been treated as described above to remove gases
present in the epoxy) is poured into receptacle 124A to fill the spaces
around the sensor electronic components and circuitry, and around first
conduit 116 and second conduit 136. Once poured, epoxy 120 may be
further treated as described above. Epoxy 120 is then cured.
[0032] Membrane 114 is positioned so that membrane 114 extends
across, so as to completely cover, opening 124B of cylindrical portion 124,
and peripheral portion 114A of membrane 114 rests against flanged rim 127
of base 123. Cover 125 is then placed over membrane 114 (on an outward
side of membrane 114) so that flanged rim 128 of cover 125 abuts against
peripheral portion 114A of membrane 114 and against flanged rim 127 of
base 123.
[0033] To pressurize compartment 112, the mouth of a vacuum hose is
placed against cover 125 to cover the openings in cover 125 (e.g. bore 142
and inlet ports 110). The vacuum hose is operated to suction air through the
openings in cover 125 so that membrane 114 is drawn in outward direction
118 (toward the vacuum hose) until membrane 114 abuts against the inside
surface 103 of cover 125. Screws 129 are then inserted through flanged
rims 127, 128 and membrane 114 to couple together base 123 and cover
125, and to secure membrane 114 between flanged rims 127, 128 so that
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membrane 114 sealingly covers compartment 112. Compartment 112 is
bounded on one side by membrane 114 and bounded on another side by
epoxy 120.
100341 The vacuum hose is subsequently pulled away from cover 125
and membrane 114, causing membrane 114 to retract and assume its natural
outwardly extended configuration (as shown by the solid line representing
membrane 114 in Figure 2). As there is a quantity of trapped air in
compartment 112 which is forced to occupy a smaller space after
membrane 114 retracts, compartment 112 becomes pressurized (i.e. pressure
in compartment 112 increases relative to standard atmospheric pressure). In
particular embodiments, about 3 cm3 (0.183 in3) of air (at standard
atmospheric pressure and room temperature) becomes trapped within
compartment 112 during the assembly of sensor 100 as described above. In
particular embodiments, when sensor 100 is placed in an environment at
standard atmospheric pressure, the pressure in compartment 112 is at 2 PSI
(13.8 kPa) above standard atmospheric pressure.
[00351 Sensor 100 may be assembled at atmospheric pressure at sea
level. At sea level, atmospheric pressure is near or at standard atmospheric
pressure which is 101.3 kPA (14.7 PSI or 1 atm) (absolute). Variations in
atmospheric pressure at sea level due to weather and other causes may
contribute to variations in the quantity of trapped air within compartment
112 for each sensor 100, which in turn affect the pressure readings obtained
from pressure transducer 104. Variations in the quantity of trapped air
within compartment 112 tend to be small, as atmospheric pressure at sea
level is generally within the range of about 100.7 to 102 kPa (14.6 to 14.8
PSI) (absolute). Also, percentage error in the pressure readings caused by
the variation in quantity of trapped air within compartment 112 tends to be
greater at lower tire pressures (e.g. below 34.5 kPa (5 PSI) (gauge)) than at
higher tire pressures (e.g. above 34.5 kPa (5 PSI) (gauge)). However, at
such lower tire pressures, the vehicle tire would be considered underinflated
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and the effects on pressure readings (even significant percentage errors)
would be considered irrelevant.
[0036] In some embodiments, rather than using the vacuum hose
assembly technique described above, compartment 112 may be pressurized
by inserting a gas (e.g. nitrogen or carbon dioxide gas) into compartment
112 (i.e. the space bounded by or defined between membrane 114 and
epoxy 120). For example, nitrogen in liquid or gas form may be injected
into compartment 112 after coupling together base 123 and cover 125 with
membrane 114 therebetween.
[0037] In other embodiments, compartment 112 may be pressurized by
placing a dry ice pellet (solid carbon dioxide) in cylindrical portion 124 of
base 123 prior to covering opening 124B with membrane 114. Membrane
114 and cover 125 are then positioned over base 123. Screws 129 are
inserted through flanged rims 127, 128 and membrane 114 to couple
together base 123 and cover 125 and to form a compartment 112 between
epoxy 120 and membrane 114 containing the dry ice pellet. The dry ice
sublimes to carbon dioxide gas, thereby pressurizing compartment 112.
[0038] While a number of exemplary aspects and embodiments have
been discussed above, those of skill in the art will recognize certain
modifications, permutations, additions and sub-combinations thereof. For
example:
= A battery 108 is provided in the described embodiments to supply
electrical power to pressure transducer 104 and transmitter 106. In other
embodiments, battery 108 is not necessary. For example, a supply of
power external to sensor 100 may be provided to power pressure
transducer 104 and transmitter 106.
= A control and processing unit 105 is provided in the described
embodiments to process the signals generated by pressure transducer
104 so that the processed signals translate into pressure readings which
are indicative of air pressure in tire interior 152. In other embodiments,
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control and processing unit 105 is not necessary. For example, a
pressure transducer 104 may be provided that is already calibrated for
the specific sensor 100 in which it is installed. In other embodiments,
the signals generated by pressure transducer 104 may be transmitted by
transmitter 106 to a remote processor, and processed by suitable
software on the remote processor to obtain pressure readings indicative
of air pressure in tire interior 152. In yet other embodiments, the signals
generated by pressure transducer 104 may be adjusted by way of
capacitors, resistors and/or other circuitry electronically coupled
between pressure transducer 104 and transmitter 106.
= Instead of epoxy, the sensor electronic components and circuitry may be
encapsulated in another solid or semi-solid potting material, such as
urethane and the like.
= Flanged rims 127 and 128 may be coupled together by other means (e.g.
clamps, etc.).
= In some embodiments, a channel, recess or the like may be provided or
defined in epoxy 120 as a conduit 116 to carry pressurized air within
compartment 112 to pressure transducer 104.
= In the illustrated embodiment, housing 102 comprises a base 123 and a
cover 125 which are coupled together. However, this is not necessary.
In some embodiments, housing 102 may be a single molded piece. In
certain embodiments, housing 102 only has a base or casing 123, which
accommodates the sensor's electronic components and circuitry.
Membrane 114 may extend across an opening 124B of base 123 and may
be substantially exposed to tire interior 152. Membrane 114 may be
coupled to base 123 so as to contain a compartment 112 within base 123
which is bounded by or defined between membrane 114 and epoxy 120.
Compartment 112 may be pressurized using a suitable technique (e.g. by
injecting gas into the compartment, or by placing a dry ice pellet in the
compartment prior to covering opening 124B with membrane 114).
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It is therefore intended that the following appended claims and claims
hereafter introduced are interpreted to include all such modifications,
permutations, additions and sub-combinations as are within their true spirit
and scope.
