AU703974B2 - Method of monitoring conditions of vehicle tires and tires containing a monitoring device therein - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Bridgestone/Firestone, Inc.

Actual Inventor(s): Russell W. Koch John L. Turner S.Guy J. Walenga *Hiroyoshi Takigawa Keizo Okamoto Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: METHOD OF MONITORING CONDITIONS OF VEHICLE TIRES AND TIRES CONTAINING A MONITORING DEVICE THEREIN Our Ref 529542 POF Code: 135994/1035 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 'i METHOD OF MONITORING CONDITIONS OF VEHICLE TIRES AND TIRES CONTAINING A MONITORING DEVICE THEREIN The present application is a divisional application from Australian patent application number 20302/95, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION This invention pertains to a methQd for monitoring various conditions of pneumatic tires and to tires containing a monitoring device. More particularly, the invention relates to a method of monitoring tires which uses an active, self-powered, programmable, electronic device which is generally installed in or on the interior portion of a pneumatic tire or on a tire rim.

The device can be used for monitoring, storing and telemetering information such as temperature, pressure, tire mileage and/or other operating conditions of a pneumatic tire, along with tire identification information.

BACKGROUND OF THE INVE TION It is desirable to monitor the condition of tires as to wear, internal temperature and internal pressure. It is partiularly advantageous to monitor large truck tires since these re expensive and must be regularly maintained to maximize vehicle efficiency.

In the past, such monitoring activities have generally used a passive integrated circuit embedded within the body of the tire and activated by a radio frequency transmission which energizes the circuit by inductive magnetic coupling. Passive devices which rely on inductive magnetic coupling or capacitive coupling generally have .the disadvantage of requiring lengthy coil windings, thus requiring major modifications in the tire construction and assembly process. Another serious disadvantage 1A 1A D-9 401002 with such passive devices is that the interrogator must be positioned in very close proximity to the tire, usually within a few inches of the tire, in order to allow communication between the tire and the device. Because of the proximity requirements, continuous monitoring is impractical since it would require that an interrogator be mounted at each wheel of the vehicle. Manual acquisition of data from the passive devices embedded in each of the tires of a parked vehicle is also cuinbersome and time consuming because of the proximity requirements.

other prior art devices 'used for monitoring tire conditions have comprised self-powered circuits which are positioned external of the tire, such as at the valve stem.

Externally mounted devices have the disadvantage of being exposed to damage, such as from weather and vandalism. Another disadvantage with installing devices. external of the tire is that the device itself introduces additional sealed joints from which air may leak. Additionally, externally installed devices can easily become disassociated from a particular tire which is being monitored.

Another disadvantage with known tire monitoring and identification devices is that d:ornmuiication transmissions are achieved using conventional radio frequencies which generally require a relatively large antenna which must be mounted externally or secured to- the tire in, such a manner which requires 25 relatively major modifications in the tire construction or assembly process.

SUMMARY OF THE INVENTION According to one aspect of the invention there is provided an apparatus for monitoring an engineering condition of a tire including: a flexible housing having a hardness of from about 50 to about 95 on the Shore A scale, said housing including a first surface which can be adhered to a second surface located within a pressurizable cavity of a tire so as to minimize stress, strain, cyclic fatigue, impact and vibration; and a monitoring device positioned within said housing, said monitoring device including a battery having an active mode and a dormant mode, a circuit for data band switching, an integrated circuit including data storage, sensors for sensing the engineering condition, means for converting said sensed condition to data; means for energizing the circuit for data band switching to activate the battery from the passive mode to the active mode; and means for transmitted said data responsive to a signal while the power source is active; means for energizing the circuit for data band switching to deactivate the battery from the active mode to the passive mode after transmitting said data.

The monitoring device is preferably capable of being programmed to 20 remain in a dormant mode unless a condition limit has been exceeded such that the monitoring device does not respond to routine interrogation unless a condition limit has been exceeded.

The monitoring device can ae secured to the tire wall by means of a pocket or cover which holds the device to the tire. The cover or pocket can be secured S 25 to the tire by utilizing a chemical or heat activatable adhesive. The monitoring device is secured to the tire in such a manner and location as to minimize stress, strain cyclic fatigue, impact and vibration.

Desirably, the tire information is received at a monitoring station where the information can be viewed on a color coded, visual display, and even have an audio signal and/or flashing lights to indicate an undesirable condition with respect to acceptable values. The display can show all the tires of a vehicle sequentially or at the same time. Alternatively, the monitoring device can be activated to transmit the various conditions to a host storage device located in a C IMNWtRDMELSA4BRAr,,N', *'ELE.tE !J1 -1r2*01VV0C weight station, a trucking terminal, et., which thus can record and contain the history of the transmitted condition values of the individual tires.

According to another aspect of the invention there is provided a method of monitoring at least one engineering condition of a tire, including the steps of: providing tire with a monitoring device, the monitoring device including a sensor, an amplifier, an antenna, a power source having an active mode and a dormant mode, a circuit for data band switching, and an integrated circuit including data storage; securing the monitoring device within the tire in such a manner and location as to minimize stress, strain, cyclic fatigue, impact and vibration; sensing the engineering condition of the tire; storing the sensed engineering condition of the tire as data in the data storage of the integrated circuit; activating the power source using the data band switching; transmitting the stored data in the data storage of the integrated circuit and the current sensed engineering condition of the tire as amplified electronic signals using the antenna of the monitoring device from within the tire while the power source is activated; and then 20 switching the power source from the active mode to the passive mode.

According to further still another aspect of the invention there is provided a tire having means for monitoring at least one engineering condition of the tire, including: the tire mounted on a rim defining a pressurizable cavity between the tire 25 and said rim; a monitoring device, said monitoring device in fluid communication with said pressurizable cavity and located on a boundary of said pressurizable cavity so as to minimize stress, strain, cyclic fatigue, impact and vibration, said monitoring device including a battery, a circuit for data band switching, an 30 integrated circuit including means for storing data, at least one sensor for sensing C WNWORD',)MELIS$A8RA[OO4OELETErFECI3ODV

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each engineering condition, means for converting each of said sensed conditions to data for storing, means for energizing the cir" uit for data band switching to activate the battery from a passive mode to an active mode, means for transmitting said data responsive to a signal while the battery is active, and means for energizing the circuit for data band switching to deactivate the battery from the active mode to the passive mode after transmitting said data.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial cross-sectional view of a pneumatic tire with monitoring devices installed at two alternative locations within the pressurizable cavity of the pneumatic tire; Fig. 2 is a block diagram of the electrical components and antenna of the monitoring device utilized; Fig. 3 is a side elevation view of an alternate configuration of the electrical components and antenna of the monitoring device shown in Fig. 2; Fig. 4 is a block diagram of the micro-chip contained in the monitoring device shown in Fig. 2; Fig. 5 is a block diagram of an interrogator which communicates with and *o*o retrieves information from the monitoring device; Fig. 6 is a cross-sectional view of an encapsulated electronic monitoring device assembly; Fig. 7 is a cross-sectional view of a monitoring device assembly which is mounted to the interior wall of a pneumatic tire by means of a cover secured to the interior wall of the pneumatic tire; Fig. 8 is a cross-sectional view of a monitoring device assembly which is positioned within a recess on and is mounted to an interior wall of a pneumatic i: tire by means of a cover secured to the interior wall of the pneumatic tire; S *Fig. 9 is a perspective view of the cover securing the monitoring device assembly to the interior wall of the housing; C IWIMVWROMLSSAE3RA JOI)3IELETE PEC I030,DIV 00C Fig. 10 is a cross-sectional view of a suitable cover formed on the interior wall of a pneumatic tire for securing a monitoring device thereto; Fig. 11 is a sectional view of a pocket assembly in accordance with another embodiment of the invention; Fig. 12 is a top view of the pocket assembly of Fig. 11; Fig. 13 is a sectional view of a tire having a monitoring device assembly embedded in the interior of the tire in the vicinity of the tire crown; Fig. 14 is a sectional view of a tire having a monitoring device assembly embedded in the tire on the tire inteiior in the vicinity of the tire bead; and Fig. 15 is a sectional view of another embodiment of the tire showing the monitoring device assembly attached to the interior of the tire in the vicinity of the tire crown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, in Fig. 1 there is shown a partial sectional view of a pneumatic tire 5 having a monitoring device 10 or secured to the inner wall of the pneumatict ire 5 at two preferred locations ::thereof. In practice, a pneumatic tire would generally have only one electronic monitoring device at any interior tire location or on tire rim 12.

As apparent from Fig. 1, one preferred location is in the vicinity *0 C WNWOR ELITARA MEE-EEPCISP 302UD CuC

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of the tire bead below the end of the body ply turn-up where the sidewall bending stiffness is greatest and where the rolling tire stresses are at a minimum. The lower most extent of the tire bead location wherein such properties are obtained i5 generally the bottom of the tire bead. In a specific tire, for example, a 285/7*5R24.5 R299 Truck/Bus Radial (OTBR') this preferred location is a distance of about one to about two inches above the toe bottom of the tire. Above Ithe noted range, 'the cyclic strain amplitudes grow very quickly. As also shown in Fig. 1, another preferred location of the monitoring device is on the inside of the tire at the center of the tread crown where tire stresses from mounting and dismounting are at a minimum.

The monitoring device 10 is comprised of a microchip an antenna 30, an amplifier 42, a battery 44, a pressure sensor 46, and optional temperature and mileage/distance sensors (not shown), populating a circuit board 48 as depicted in Fig. 2.

While not shown in the embodiment of Fig, 2, it is envisioned that the microchip 20 itself can -contain all or some of the aforementioned components.

While optional, it is desirable that the monitoring device be contained in a rigid or semi-rigid encasement to *enhance' rigidity and inhibit straining of the device. This reinforcing encasement or encapsulation is a solid material, non-foamn compounds,-,which is compatible -with- the tiretoo. 25 rubber, such as various urethanes, epoxies, -unsaturated polyester-styrene resins, and hard rubber compositions. Hard rubber compositions generally refer to any type of rubber Dr elastomer which is crossliiiked and has a Shore A hardness of from about to about 100, and desirably a Shore D hardness of from about 5 to too. 30 about 80 and preferably a Shore 1) hardness from about 40 to about We have found that the solid materials most suitable for use as reinforcement encasement or encapsulation of the device typically have an elastic modulus (Young's Modulus, E) in the range of about 100 ksi (100,000 pounds per square inch) to about 500 (500,000 pounds per square inch) ksi. The actual selected elastic modulus of the solid reinforcement encasement materials used to encase the device are a function of the stiffness of the monitoring device itself.

An example of the monitoring device being encapsulated is shown in Fig. 6, wherein monitoring device 10 is encased within encasement or encapsulating material 16 'to form monitoring device assembly 17. As shown in Fig. 6, it is an important aspect of the present invention that the sensor 46, which measurt-, pressure, have an opening, aperture, etc., 18 to allow an air path to the sensor so it can measure the internal tire pressure.

Referring now to Figs. 7 and 8, and as noted above, monitoring device assembly 17 can optionally have a flexible housing such as pocket 75 or cover 80. Suitable housing materials which function to hold the monitoring device to the tire include generally flexible and resilient rubbers suich as natural rubber or rubbers made from conjugated dienes having from 4 to 10 carbon atoms such 'as synthetic polyisoprene, polybutadiene, styrene-butadiene'ribber, and the like, flexible polyurethanes, flexible epoxides, and the like, and having a 2.hardness on the Shore A hardness scale of from about 50 to abo ut 9 5, and- pre ferably f rom -about -55 to -abou t 9 25 Fig. 9 is a perspective View of Figs. 7 and 8 showing the cover 80 secured to the interior- wall 7 of tire 5. The cover has an adhering surface which secures the monitoring device '9..assembly to a surface of the tire, preferably within the pressurizable tire cavity. Slit 84 provides an air passage so that the pressure sensor can appropriately monitor air pressure.

Fig. 7 shows monitoring device assembly 17 secured to tire 5 through cover 80. The cover has a slit 84 to allow a pressure sensor of the device to detect the internal tire pressure. Generally, cover 80 is secured to the interior portion of the tire, Except for the opening or slit 84 necessary for pressure sensing, the cover 80 surrounds the monitoring device assembly 17 as shown in Fig. 7, arnd is secured to the interior portion of the tire about the perimeter of the monitoring device asseti bly.

As apparent from Fig, 8, the monitoring device assembly 17 is located within tire pocket or recess 751. The tire pocket or recess 7- can be made by inserting a rectangular 'VEFLQNW (PTFE) billet of the appropriate dimensions onto the uncured tire inter-Liner at the location of the desired recess 75. During tire manufacturing, the curing pressure of the mold will press the billet into the tire inner liner and cure in the recess pocket as shown in Fig. 8. Cover 80 is then attached about the perimeter of the monitoring device assembly to the tire inner liner.

Cover 80 also has a slit 84 therein to allow detection of air pressure. cover 80 may be co-cured with the green tire or may be attached to the tire af ter curing by use of various types of adhesives as discussed below.

Referring now to Fig. 10, when a cover 80 such as shown 'in the configurations of Figs. 7 'and 8 is utilized, a non-adhering sheet 86, constructed, for example from TEFLON" (PTFE) or silicon release materials, can be placed between the cover 80 and the underlying tire inner wall 7 to ensure -that -a "cavity 'is formed to house the monitoring device assembly. The cover is th~ adhered to the interior of the tire utilizing a suitable adhesive system. After curiing of the adhesive system, the nonadhering sheet 86 is removed. The monitoring device, whether or not encapsulated, can then be inserted through the slot of flexible cover 80. Alternatively, the monitoring device, whether or not encapsulated, can be positioned in an abutting relationship with tire 5 and cover 80 installed thereover and adhered to tire 5 at the cover perimeter by a suitable adhesive.

Xn preferred embodiments as shown in F'igs. 11 and 12, the monitoring device is contained within housing pocket 90 which has a slot for mouhting the assembly within the pocket and through which the antenna of the monitoring device can project after assembly. Further, pocket 90 includes an optional substrate 110 such as to assure adhesion of pockcet 90 to tire The housing pocket 90 comprises a top portion or cap 92 having a pocket cavity 94 for receiving and retaining- monitoring device assembly through opening 96. Pocket cavity 94 is generally of a suitable size and shape to snugly hold or secure monitoring device assembly. Pocket 90 also includes band 98 for securing and biasing antenna 30 of the monitoring device assembly to raised portion 102 of pocket Mnother manner of securing the monitoring device assembly 17 to tire 5 is to physically embed monitoring device assembly 17 within tire 5 during the manufacture of the tire by placing the device between the tie-gum ply 199 and inner liner ply 200 of the uncured tire. After curing, the device is perm~anently contained in the tire structure. Figure 13 illustrates a 20 tire cross section containing an embedded monitoring device assembly 17 positioned in the inner liner body piy portion 200 located at or in the vicinity of tire crown 202 by this method.

Crown 202 is one of the preferred locations for placement of the monitoring device. Experience has 'shown- that the monitoring device should not contact the body ply 204 because such contact may degrade the durability and structural performance of body ply 204. Another preferred location is near tire bead 210 as shown in Figure 14. A small removable dowel 206 is contained in the monitoring device assembly 17 at the time of placement in the green tire. The dowel 206 presses through inner liner ply portion 200 upon the application of curing pressures to form a hole or aperture for air passage to the pressure sensor in the monitor assembly 17, The dowel 206 should have suitable dimensions and a smooth, rounded end to ensure passage through the soft inner liner rubber without damaging the mold bladder (not shown) which is used during the tire curing operation, If desired, the mold bladder can be reinforced at the location of monitoring device assembly 17 and dowel 206. Dowel 206 is remoVed after curing of the tire, leaving a finished air hole.

-enibodiment for embedding the monitoring device assembly is illustrated in Fig, 15. In this method, a dowel 220 is first inserted through an inner liner patch 222, and then into the monitoring device assembly 17, Next, monitoring device assembly 17 is sandwiched between the uncured tire inner liner ply 200 and inner liner patch 222. After curing, the monitoring device assembly 17 is permanently embedded between patch 222 and ply 200. In this procedure, a larger, contoured dowel head 224 can be employed to further reduce trauma to the mold bladder (not shown).

The various adhesive systems which can be used to adhere the monitoring device to the tire embrace numerous chemical cure adhesives including ambient temperature amine curable adhesives. Heat cure adhesives can also be used.

Suitable chemical cure adhesives include conventional sulfur cure systems such as various self vulcanizing cements, various chemical vulcanizing fluids, and the like such as those sold by The Patch Rubber Company of Roanoke Rapida North-Carolina.

25 The room temperature or ambient amine curable adhesive system comprises initially applying a treating agent to the various surfaces to be adhered tire, cover, etc.) followed by the application of various amine curable polymers or prepolymers. Suitable treating agents include various N- 30 haloamides, the various N-halohydantoins, the various Nhaloimides, and combinations thereof. Examples of various desirable N-halohydantoins include 1, 3-dichloro-5,5-dimethyl hydantoin; 1, 3-dibromo-5,5-dimethyl hydantoin; 1,3-dichloro-5and 1,3-dichloro-5-methyl-5-hexyl hydantoin. Examples of N-haloamides include N-bromoacetamide and tetrachloroglycoluril. Examples of N-haloimides include Nbromosuccinimide and the various chloro substituted striazinetriones, commonly known as mono-, di-, and trichloroisocyanuric acid. A preferred treating composition for use in the practice of the present invention are ;ne various mono-, di-, or tri-chloroisocyanuric acids,' or combinations thereof. Trichloroisocyanuric acid is especially preferred.

The treating agents usually exist in solid form. They are readily soluble in solvents such as acetone and the like and thus can be applied in liquid form. Application of the treating agent generally occurs at ambient temperatures. Application can occur through any conventional manner as through brushing, spraying, and the like. The amount applied is such that the substrate is coated. Preferably, two or more coats of the treating agent or adhesive compound are used to ensure that all the cured rubber substrate surface has been coated, Said ambient temperature amine curable adhesive systems are known to the art and literature as set forth in U.S. Patent Nos. 4,718,469, 4,765,852, and 4,923,543, which are hereby fully incorporated by reference.

The heat cured adhesion systems generally utilize various adhesives which upon heating-to temperatures of at least 25 100 0 C and generally from about 115 to about 170 0 C form an adhesive bond between the tire substrate and directly or indirectly with the monitoring device, it being understood that the curing time required is dependent on temperature, with shorter times required at higher temperatures. Suitable conven- 30 tional heat cured adhesives are known to the art and include various extruder cements, various retread and vulcanizing cements, and the like, for example, those sold'by The Patch Rubber Company of Roanoke Rapids, North Carolina.

.12 The adhesive may be directly applied to the monitoring device, to the encased or encapsulated monitoring device assempbly, to the cov~r or pocket for the monitoring device, or any combination thereof. Alternatively, the monitoring device or monitoring device assembly can be attached to the tire rim with a suitable adhesive. WThen a cover or pockec is utilized, an intermediate layer such as a cushion gum layer is optionally but desirably c.ontained between the adhesive applied to the cover o~r pocket on one hand and the adhesive applied to the tire interion on the other hand to insure better adhesion of a monitoring device to the tire. Desirably, both the tire and the cover or pocket have pi-eviously been, buf fed and cleaned with a solvent and coated with an adhesive, Referring now to the monitoring device or tag 10, 1includes a board made of a suitable material to hold the various components, one of which is an integrated circntit-or micriu chip as is shown in the block diagram of Fig. 4. The integrated circuit, preferably includes one or more analog to digital converters for digitally codiug internal and or external analog sIgrials Suitable integrated circuits for use with the invention :are commercially available and/dr can be fabricated. one such oommerciplly available circuit. 20 which has been found tc be particularly well suited for use with the invention is an RFID **"Micron' chip available from-M~icron Cormunicati, ns, 'Inc. of Boise, Idaho. Fig. 4 is a block diagram~ of th(- 'Micron* chip which is suitable for use with the invention.

The chip, 20 contains a central processing unit for processing commuands, a 256 byte rrandom access nwimory and micro wave radio circuitry for transmission and reception of data. The center frequency of transmission is 2.45 GHz. Circuitry for low and high frequency transmission bands are utilized by the chip to wake up or turn -ff to outside transmissions (Instructions), according to a scheme de-,!loped by Micron and defined in their .13 t 20 25

S.

.0 3 D59 protocol publication of July 22, 1993, pre-release Ver. 0.95.

Internal sensors for monitoring tenperature, supply voltage, magnetic field strength and ambient light intensity are contained in the chip. The chip also has communication ports supporting digital and analog input/output functions. The analog port can be programmed to source up to 2 milliamps of current. Analog input voltages from 0 to 2.5 volts can be read for monitoring external sensors. Up to 256 analog ports can be sampled by multiplexing. The chip can execute up to 30 predefined commands sent by radio transmission. These commends include functions dealing with tag identification, memory read/writes, I/O port read/writes, alarm thr shold settings, password/security and enable/disable comands.

The integrated circuit 20 also preferably includes the already discussed internal sensors and/or one or more external analog ports for receiving an analog signal. from one or more external sensors. The device optionally but preferably includes a pressure transducer which is preferably a solid state device such as a piezo-resistive pressure sensor. Suitable piezo-resistive pressure sensors are available from Lucas NovaSensor.

Particu,.ilarly preferred are Lucas NovaSensor's NPC-103 series sensors.

The temperature sensor can also generally be any conventional sensor such as Model No. LM 35 CAZ made by National'.

Semiconductor. The tire mileage detector can give out a readout signal in miles, kilometers, etc., and preferably may be in the form of a mild magnetic detector responsive to an external magnetic field which field is sensed by the detector upon each full revolution of a tire. Alternatively, a detector may detect each up or down cycle of the tire and produce a signal which is counted. This counted number can then be sued to calculate tire mileage. An additional sensor which cn be utilized is a speed sensor which monitors the speed of the vehicle.

14 The electronic monitoring device or taq 10 contains various~ components for receiving and transferring infcA.xation to the interrogator. A specific component is the amiplifier 42 which is used to boost the analog signal received from various sensors and transmit the same to the chip and subsequently to the interrogator. The amplifier can be connected to an exteriiaj.

analog port of the microchip 20, The electronic moriitorinr device is active inasmuch as it contains a power source such a a battery and thus is self-powered. Any conventional long litL alkaline-battery 44 can be utilized such as a 0.07 amp hour, lithium thionyl chloride battery, type 7-10 made by Battery Engineering, Inc., of Hyde Park, M4A.

M~onitor 10 also includes a microwave antenna 30 which can be located either adjacent to the monitoring device shown in Fig. 2 or alternatively ou the backside thereof as shown in Fig.

3. The antenna 30 can be a suitable conducting means such as a single serpentine narrow wire ovt a thin sheet of a metal foil, for example, copper, so long as it has a resonance frequency similar to the microwave transmission frequency, Generally, any 2: microwave frequency can be utilized such as from about 1 x 109 to :about 5 x 10' hertz with a suitable frequency being from about 2.40 to about 2,49 x 10' hertz.

Another embodiment, not shown, utilizes sensors exterior of monitoring device 10 as in the-form of decals halving lead lines running to Ub~e monitoring chip, F'ig. 5 is d block d~i.agram of a generic type 4interrogator 60 which can be used to communicate with and retrieve digitially coded informuation from the electronic monitoring device, The interrogator includes microwave transmitter and receive circuits for communicating with the micro chip.

The RV? transmitter utilizes dual frequency bands so that only tags monitoring devices) programmed to responid to a certain band will be activated, leaving the others dorman~t and conserving battery power, This is called "data b~and switching"s and is defined as part of the public domain Mticron protocol. The interrogator includ~s circuitry to receive and transmit using spread spectrum modulation as defined in the Miicron protocol and as required by the F'CC for microwave communication devices. The power level of transmission is user select:able and either one or two antennas can be employed by the interrogator to improve reception, The interrogator includes 1/0 cori-aunications hardware to support interaction with a host camputer via paral.lel., serial RS-232, RS- 485 and.Ethernet links. A commercially manufactured interrogator of the type described is available fr:om Unisys Corp., Salt Lake City', Utah. The interrogator car. be interfaced with a computer 70 to allow downloading, archiving, and analysis of data transmitted from the electronic monitoring device moreover, different interrogators or a pluralihy thereof can be utilized with respect to different interrogation situations.

The interrogator can be remotely located in a vehicle, a truck, to permit intermittent monitoring at regular .:...int-ervals such as every thirty minutes, to alert the driver of the vehicle of any imminent or imapending problems such as over or :under inflation or abnormally high temperatures. Alternatively, the interrogator can be located at a vehicle service stop, e.g., fuel station, trucking terminal, or at any other convenient location for archiva, and/or-current sensor readouts-o, -tirepressure and tire revolutions, etc as through visual readouts, flashing lights, etc., as noted above. The monitoring devices in ;each tire can be interrogated for information at regular or arbitrary intervals and the data can be stored on a computer inte-Zfaced to the interrogator. The monitoring device 10 can also be programmed to act as an alarm system to warn of extreme temperature or pressure conditions, or it may be used to log pressure and/or temperature histories during tire operation.

.16 Such data can be used, for example, to evaluate the retreadability of truck tires.

The interrogator includes various features such as software protocol for sorting, identifying and communicating with multiple monitoring devices without ambiguity, thus enabling a signal interrogator to quickly sort and retrieve informnation from a plurality of monitoring devices associated wich individual tires on a vehicle or on multiple vehicles. Th-e broadcast range, from within a tire can vary, such as in excess of fifty feet, thus permitting a stationary interrogator to quickly query all tire chips on a vehicle which is passing by the interrogator or from an on board vehicle location, In accordance with the preferred mode of the invention, a tire is provided with a self-powered moniitoring 'device on the interior or within the tire or on the Lire material. The monitor-ing device includes means to sense and store data regarding a tire condition, such as temperature or pressure. in response to a triggering signal, the power source of the monitoring device is activated and the device transits the condi- 2 0 tion data. F'or example, the monitoring device may be identified by having the interrogator read the identification code associated with the tire to Tqhich the monitoring device is affixed. The identification code can, for example, be stored as a 10 byte ***.nuxrber, the first- 4 bytes containing a -standard interniationial classification (SIC) code, the next 2 bytes containing a specialty code, and the last 4 bytes identifying the particular Further in accordance with the preferred mode of the invention, the monitoring devices 10 include low to high data band switching for selective communication between multiple interrogators and multiple monitoring devices. The low band can correspond to a dormant mode wherein battery power is conserved.

Monitoring device 10 will remain dormant unless an interrogator broadcasts a low band instruction to activate the device. The mon.4toring device and interrogator frequencies can be switched upon command. This allows for selective groups of monitoring devices to become actilve and respond to an interrogator broadcast while others remain dormant. The monitoring device frequency can be switched by an externally measured event which is being monitored by a sensing device temperature) so that it activates in response to an interrogator upon a preset limit to a monitored condition being exceeded. High and low sensor thresholds can be programmued to determine when frequency switching occurs, thu~s enabling the monitoring devices to operate in an alarm mode.

P.lso in accordance with a preferred mode of the invention, corraiitnications between multiple monitoring devices and an interrogator or multiple interrogators is facilitated by means of an arbitration method, thereby permitting unambiguous vcommunications. The interrogator, monitoring device, and data communication protocol preferably allow various commands to be transmitted from the interrogator to the monitoring device.

Examples ofdesired commands include functions dealing with tire identification, memory, digital and analog port read/writes, alarm threshold settings, password and security data and enable and disable commands, These commands determine the functionality of the monitoring device and permit customization of operation for different applications. For example, through software cornmands a monitoring device can be set to ignore inquiries from an interrogator unless a tire temp~erature exceeds a certai.n threshold or an air pressure falls below a given set point. Alternatively, the monitoring,-device could be set to respond to an on board vehicle interrogator request for period-ic readings of~ temperature and pressure during tire operation in. the field.

Battery life would dictate the frequency and duration of communications that are possible, While in accordance with the patent statutes the best mode and preferred emrbodiment has been set forth, the scope of the invention is not 1.imited thereto, but rather by the s5cope of the attached claims.

0 O t 19

Claims (19)

1. An apparatus for monitoring an engineering condition of a tire including: a flexible housing having a hardness of form about 50 to 95 on the Shore A scale, said housing including a first surface which can be adhered to a second surface located within a pressurizable cavity of a tire so as to minimize stress, strain, cyclic fatigue, impact and vibration; and a monitoring device positioned within said housing, said monitoring device including a battery having an active mode and a dormant mode, a circuit for data band switching, an integrated circuit including data storage, sensors for sensing the engineering condition, means for converting said sensed condition to data; means for energizing the circuit for data band switching to activate the battery from the passive mode to the active mode; and means for transmitting said data responsive to a signal while the power source is active; means for energizing the circuit for data band switching to deactivate the battery from the active mode to the passive mode after transmitting said data. 0*

2. The apparatus as set forth in claim 1, wherein said device includes means 20 for receiving a microwave frequency signal, and means for transmitting said data in response to said microwave frequency signal.

3. The apparatus as set forth in claim 1 or claim 2, wherein the device further includes means for switching said battery from said dormant mode to said active mode to activate said monitoring device in response to said transmitted microwave frequency signal.

4. The apparatus as set forth in any one of the preceding claims, wherein said monitoring device includes a circuit board, at least one sensor for monitoring the engineering conditions of the tire, a microchip mounted on said circuit board which received said sensed condition and electronically conditions said sense condition as a signal, an amplifier for amplifying said conditioned signal in r' I~MhZ'RP~t li:;gAARbi li~lilrt :I'tlll'ZIP::IIV I'ill response to an external signal, an antenna for transmitting said amplified, conditioned signal, and a battery for powering said microchip and said amplifier. The apparatus of any one of the preceding claims, wherein said monitoring device is encapsulated by a solid material having a Shore D Hardness from about to about 80 and an elastic modulus of from about 100 ksi to about 500 ksi to form a monitoring device assembly.

6. The apparatus as set forth in any one of the preceding claims, wherein said housing includes a recess molded into the second tire surface, and a cover positioned over said recess, said cover including a slot for insertion of said monitoring device into said housing.

7. The apparatus as set forth in any one of the preceding claims, wherein said monitoring device includes an antenna and said housing includes a band for retaining said antenna in a position exterior to said housing.

8. The apparatus as set forth in any one of the preceding claims, wherein said monitoring device housed in said housing is positioned in a tire in the vicinity of a tire bead below a body ply.

9. The apparatus as set forth in any one of the preceding claims, wherein said monitoring device housed in said housing is positioned in a tire in the vicinity *of a center portion of tread crown below a body ply.

10. A method of monitoring at least one engineering condition of a tire, including the steps of: providing tire with a monitoring device, the monitoring device including a sensor, an amplifier, an antenna, a power source having an active mode and a dormant mode, a circuit for data band switching, and an integrated circuit including data storage; AWVORDELI,. AIMQ~i VN TE'EI. 'I securing the monitoring device within the tire in such a manner and location as to minimize stress, strain cyclic fatigue, impact and vibration; sensing the engineering condition of the tire; storing the sensed engineering condition of the tire as data in the data storage of the integrated circuit; activating the power source using the data band switching; transmitting the stored data in the data storage of the integrated circuit and the current sensed engineering condition of the tire as amplified electronic signals using the antenna of the monitoring device from within the tire while the power source is activated; and then switching the power source from the active mode to the passive mode.

11. The method as set forth in claim 10, wherein the power source of the monitoring device is activated by receiving a remotely transmitted microwave frequency impulse. S12. The method as set forth in claim 10 or 11, wherein the method further includes comparing the stored data and the current sensed engineering condition to preselected limits and causing said device to transmit a signal as a warning when said data exceeds said limits.

13. The method as set forth in any one of claims 10 to 12, wherein the method further includes the additional step of receiving the signal by a monitoring station having means tor comparing the data transmitted as a signal indicative of said condition to preselected limits, comparing the data to the limits, and emitting a warning signal when the limits are exceeded.

14. The method as set forth in any one of claims 10 to 13, wherein the step of activating further includes switching the power source from the dormant mode to the active mode in response to a transmitted micruwave frequency impulse, and switching the power sources from the active mode to the dormant mrnode after the monitoring device has completed electronically transmitting. 22 A tirm having means for monitoring at least one engineering condition of the tire, including: the tire mounted on a rim defining a pressurizable cavity between the tire and said rim; a monitoring device, said monitoring device in fluid communication with said pressurizable cavity and located on a boundary of said pressurizable cavity so as to minimize stress, strain, cyclic fatigue, impact and vibration, said monitoring device including a battery, a circuit for data band switching, an integrated circuit including means for storing data, at least one sensor for sensing each engineering condition, means for converting each of said sensed conditions to data for storing, means for energizing the circuit for data band switching to activate the battery from a passive mode to an active mode, means for transmitting said data responsive to a signal while the battery is active, and means for energizing the circuit for data band switching to deactivate the battery from the active mode to the passive mode after transmitting said data.

16. The tire having means for monitoring as set forth in claim 15, wherein said signal is a microwave frequency signal.

17. The tire having means for monitoring as set forth in claim 15 or claim 16, further including an antenna for receiving the signal and for transmitting said data.

18. The tire having means for monitoring as set forth in any one of claims 15 to 17, wherein said monitoring device includes means for comparing the sensed engineering condition with a preselected limit and means for transmitting the sensed engineering condition as a signal when the condition exceeds said preselected limit.

19. The tire having means for monitoring as set forth in any one of claims 15 to 18, wherein said monitoring device is located in a center portion of a tread crown below a body ply. W NAd.. t I L I: T 1 -e I b The tire having means for monitoring as set forth in any one of claims 15 to 18, wherein said monitoring device is located in the vicinity of a tire bead below a body ply.

21. An apparatus for monitoring an engineering condition of a tire substantially as hereinbefore described with reference to any one of the embodiments illustrated in the accompanying drawings.

22. A tire having means for monitoring at least one engineering condition substantially as hereinbefore described with reference to any one of the embodiments illustrated in the accompanying drawings.

23. A method of monitoring at least one engineering condition substantially as hereinbefore described with reference to any one of the embodiments illustrated in the accompanying drawings. DATED: 12 May 1998 PHILLIPS ORMONDE FITZPATRICK 20 Attorneys for: BRIDGESTONE/FIRESTONE, INC. 9 S* -jVV f4 1 XIJ L j3RAj N I t TF VE I L METHOD OF MO- 'TORING CONDITIONS OF VEHICLE TIRES AND TIRES CONT.,NING A MONITORING DEVICE THEREIN ABSTRACT A method and appara.is f' r monitoring various engineering conditions of pneumatic tires, and to a tire 5 including a monitoring device 10. More particularly, the invention relates to a method of monitoring tires 5 which uses an 10 active, self-powered programmable electronic device 10 which is installed in or on the interior surface of a pneumatic tire or on a tire rim 12. This device 10 can be used for monitoring, storing and telemetering information such as temperature, pressure, tire rotations and/or other operating conditions of a pneumatic tire, along with tire identification information. The device 10 can be activated by 15 externally transmitted radio frequency waves and in response, the device 9* S."compares or transmits information and provides a warning in the event a preselected limit is exceeded. S c* K :lt I:SAflRIt, lt::i ;h MT I