MXPA00005599A - Pressure sensor for a tire and method therefor - Google Patents

Abstract

An apparatus (12) is attached to a tire (10) encapsulated within elastomeric material (16) located within the toroidal region of pneumatic tire (10). The apparatus is preferably embedded in the tire at its equatorial plane (EP). An integrated circuit chip of the transponder has at least the capacity to handle and transmit data relating to tire pressure.

Description

PNEUMATIC PRESSURE DETECTOR AND ITS METHOD TECHNICAL FIELD This invention relates to an apparatus for electronically transmitting radio frequency tire pressure data. The apparatus includes a radio frequency transponder, comprising an integrated circuit chip, having at least sufficient capacity to transmit pressure data for the tire or wheel and a pressure sensor. As illustrated by the references described below, it is known in the art to transmit in radio frequencies, data of a transponder or content within the structure of a tire or a wheel tire structure. In the prior art, most of the difficulties encountered in incorporating sensors in a tire are caused by the stresses encountered in the tire construction process and somewhat stringent conditions to which a tire is subjected. Detectors and transponder systems can be destroyed by heat and pressure in the tire building process, and can be destroyed by rough use, shock or grime when used on a tire. Accordingly, a detector to be embedded in a tire to record and transmit tire data must be robust enough to survive the tire's efforts, light enough not to affect the tire's balance, and sized or positioned to not interfere with the integrity of the tire. Also, the cost of the device should not be greater than a small percentage of the total cost of the tire. Some prior art pressure sensors that can be employed in a tire are exposed directly to the tire inflation chamber. Grime and tire debris can contaminate the device and affect reading accuracy or make it non-functional. Also, when the detector is embedded in a tire construction in the tire building process and it stops working, it usually can not be replaced in the cured tire without destroying the integrity of the tire. In an effort to connect a pressure sensor in a tire, in a shape that is protected, the inventors here held a pressure sensor within a rubber patch or pouch in the inflation chamber of a tire. Although the pressure detector was protected, and gave some accurate readings, the response time was very slow, and when the pressure in a tire was changed to test the accuracy of the pressure detector. the time necessary for the pressure detector to reach equilibrium with the pressure in the tire inflation chamber, sometimes for many days. PRIOR ART Tire safety indicator means, have been provided in the prior art to indicate when the contact surface with the floor of a tire wears to the point where the same or the tire must be replaced. See, for example, U.S. Pat. No. 3,770,040 of Cicco. As the technique has advanced, systems for directing tire pressure for vehicles and the like have been proposed, where a transmitter and receiver are mounted on the head of a vehicle and magnetically coupled improver and inductor circuits are transported on the vehicle wheel to provide verification of the tire pressure of the vehicle, as described by Alien in the US patent No. 4,588,978. Other devices for verifying tire pressure have been proposed by Galasko et al., U.S. Pat. No. 4,578,992, illustrating a coil mounted on a tire that forms, with a capacitor, a passive oscillatory circuit. The circuit is energized by pulses supplied by a coil placed outside the tire and fastened to the vehicle, and the frequency in the passive oscillatory circuit is varied with the tire pressure due to changes caused to the value of the capacitance of the capacitor. The frequency of the circuit is detected by a coil placed outside the tire and attached to the vehicle. Milheiser in the U.S. Patent No. 4, 730,188, illustrates the use of a passive integrated transponder that connects to or embeds in an item to be identified, and is excited by an inductive coupling from an interrogator. Fiorletta in the U.S. Patent No. 5,289,160, illustrates a wireless tire pressure verification device that warns a low pressure driver on one or more tires. Fiorletta shows that a pressure transducer, transmitter and antenna are integrally housed and mounted on the tire stem. When the pressure transducer detects a tire pressure below a preselected pressure, the transmitter sends a radio frequency signal which, when a receiver mounted on the vehicle is detected, warns the driver. In a preferred embodiment, the transmitter is a device that is interrogated periodically by an RF signal from a transmitter in the vehicle.

In PCT applications O90 / 12474 and 90/01754, it is illustrated that electronic transponders can be embedded within or on vehicle tires with wire loop antennas and are electromagnetically driven by signals from an interrogating coil. The request indicates that the transponder responds to drive by producing a shifted frequency that is modulated with synchronization pulses and identifies digital information, and may also be used to include information on the condition and environment of the tire. Hettich et al., In the U.S. patent. No. 5,140,851, illustrates a circuit assembly for verifying air volume in vehicle tires, which provides torque correction to the tire temperature. The patent states that the measurement value of temperature and pressure of the tire is measured by a rotary detector on the wheel, which is verified and the data that is fed to a correction circuit that also receives a plurality of correction parameters. A corrected value for the temperature or for the air pressure in the tire is transmitted at the output of the correction circuit as a function of the correction parameters. PCT application WO92 / 20539 provides a warning system for abnormal tire condition, comprising a housing, a band for mounting the housing on the tire rim, a detector for verifying the condition inside the tire, circuits operatively connected to the tire. detector for generating radio signals indicative of the condition of the tire, an energy supply operatively connected to the circuits, a centrifugal switch and a receiver for the radio signals. Bunn et al., In the U.S. patent. No. 4,911,217, discloses a radio frequency tire identification system, having an integrated circuit chip transponder. Bollack et al., In the U.S. patent. No. 5,181,975 illustrates a tire having an integrated circuit transponder, comprising a helical antenna of small circumscribed area, as compared to the area circumscribed by the contact surface with the tire floor, which acts as a primary winding of a transformer . The coil is planar in shape, and when placed between the inner liner and the carcass layer of the tire, may include a pressure sensor. Brown et al., In the U.S. patent. No. 5,218,861 illustrates a tire having an integrated circuit transponder having an antenna coupled by electric or magnetic fields to the contact surface with the tire floor. Koch et al., In the U.S. patent. No. 5,500,065, illustrates locating a verification device, radially inward of the inner lining of a tire, somewhere in the crown portion of the tire. Definitions The following definitions are provided to facilitate the reading of the specification and the compression of the invention. - "Transmitter" refers to a radio frequency transmitter. "Receiver" refers to a radio frequency receiver. "Interrogator" refers to a transmitter-receiver decoder combination. "Transponder" refers to an RF energy receiver capable of transmitting coded information to an interrogator (scanner). "Equatorial plane (EP)" refers to the intersected plane in the center line of the tire. "Radially" refers to a radial line from a tire axis to a tire circumference and lines parallel thereto.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a cross section of a medium radial truck tire (RMT = Radial Medium Truck) having the apparatus of the invention embedded in the crown of the tire. Figure 2 illustrates an enlarged view of a portion of the tire of Figure 1. Figure 3 illustrates an apparatus of the invention in a tire as it is seen radially outwardly of the rim. Industrial Applicability An apparatus for electronically transmitting tire pressure data, comprises a transponder associated with a pressure detector. Externally induced radio frequency excitation, causes the data to be sent out sequentially from the apparatus as a voltage value that corresponds to the pressure in the inflation chamber of a tire. The tire comprises an outer surface that includes a contact surface with the ground, and an inner inflation chamber, and a pressure sensor encapsulated by encapsulation means associated with a radially inner surface of the inflation chamber, and an absorption medium. by capillary action associated with the pressure sensor whereby the capillary absorption means provide a path for pressure equilibrium between the pressure sensor and the inflation chamber. The capillarity absorbing means are selected from the group consisting of gas absorbent textile cords, hollow filaments and woven textile cords or filaments. The encapsulation means comprises a rubber patch surrounding the pressure sensor, the rubber patch being connected to a surface radially inward of the inflation chamber. More specifically, the tire comprises at least two parallel annular beads, at least one shell layer wrapped around the beads, surface contacting the floor arranged on the carcass layer at least in one area of the tire crown, side walls arranged between the contact surface with the floor and the beads, and an inflation chamber radially inward of the surface contacting the floor and axially between the side walls, and an encapsulated detection system associated with the inflation chamber. The detection system comprises an apparatus for transmitting tire pressure data comprising a transponder, with a flake having at least sufficient capacity to handle pressure detector data, to respond to predetermined signals that trigger a responsive signal to transmit data from pressure from the tire, and a pressure detector associated with the transponder, encapsulation means for the pressure sensor and capillary absorption means, to provide pressure equilibrium between the encapsulated pressure detector and the inflation chamber. In an illustrated embodiment, the tire has an inner liner that is positioned radially inward of the shell layer and the pressure sensor is close to the inner liner and the encapsulation means is connected to the inner liner. In the illustrated embodiment, the pressure sensor is additionally coated or surrounded by insulating rubber. The capillary absorption means may be selected from the group consisting of gas absorbent textile cords, hollow filaments and woven textile cords or filaments. Also provided is a method for connecting a pressure sensor to a tire inflation chamber, comprising the steps of (a) placing a pressure sensor in a tire construction, in a substantially flat location of low flexion, which corresponds to a surface of an air-inflating chamber in a tire, (b) attaching capillary absorption means on the pressure sensor, (c) connecting a rubber patch material, with the surface of an inflation chamber on the pressure sensor and capillary absorption means wherein the capillary absorption means have at least one end outside the dimensions of the rubber patch. In an illustrated embodiment, the method further comprises the steps of (a) constructing the tire with an inner liner comprising a radially inward surface of the inflation chamber, (b) placing the pressure sensor close to the inner liner, (c) ) placing the absorption means by capillarity on the pressure detector and (d) adhesively attaching a rubber patch to the inner liner covering the pressure sensor and partially covering the absorption means by capillary action. As is the case with similar prior art devices, the transponder is designed to receive a signal from a transmitting device to electronically activate the electronic circuit of the chip and to transmit data from the electronic circuit to a receiving device. An object of the invention is to provide a pressure sensor that can be constructed in a tire, or can be connected to a complete tire in a way that protects the detector from debris in the tire however gives quick and accurate readings, and that is sufficiently small so that it does not have a noticeable effect on the operation of the tire. Other objects of the invention will be apparent from the following description and claims. DESCRIPTION OF THE INVENTION Referring now to Figure 1, a tire 10 incorporating the apparatus 12 is illustrated, which may be employed to provide tire data such as inflation pressure within the tire. As is conventional in the art, the tire is made using at least one pair of annular beads 22, on which at least one shell layer 28 is wrapped. Bands 32 are placed on the carcass ply 28 in a crown area of the tire. pneumatic and the contact surface is placed with the floor 30 on the strips 32. Side walls 24 are placed between the contact surface with the floor 30 and the heels 22. In the illustrated embodiment, the tire also has an inner liner 14 which it is positioned radially below the carcass layer 28. The inflation chamber 20 contains the fluids used to inflate the tire when the tire is mounted on a rim. The illustrated tire is an RMT tire, but those skilled in the art recognize that the invention may have utility in passenger vehicle tires, or any tire for which data regarding pressure within the tire is required. A tire, depending on the type, can have up to four pairs of heels, up to twelve layers of carcass and up to twelve bands. The apparatus 12 is a transponder with a flake 12a having at least a capacity to collect and transmit pressure data, and a pressure detector 12d associated with the transponder. The apparatus 12 is located in the tire in a position where the flexing is minimal and where a substantially flat surface can be used to secure connection of the apparatus to the inflation chamber 15. The inner side wall near the heel and the center of the area of the tire crown are examples of possible locations for connection of the apparatus 12 in the tire 10. In the illustrated embodiment, the apparatus 12 is placed under the center of the contact surface with the floor, ie in the equatorial plane (EP) of the tire, and radially below the carcass layer 28 and the inner liner 14. The apparatus 12 comprises one or more integrated circuit flakes 12a, an antenna 12c and any auxiliary components required to make the pressure data in the tire legible. .

The transponder component of the apparatus 12 is similar to those illustrated in patents 5,181,975 and 5,218,861, issued to the Goodyear Tire and Rubber Company, and the file numbers of agent DN 1997-192, 1996082 and 1997-195 of common assignment, which is have been used to verify tire pressure. The pressure sensing component employed in the illustrated embodiment is a device from the Case Western Reserve University described in U.S. Pat. No. 5,528,452 granted to Ko. Referring now to Figures 1, 2 and 3, in the illustrated embodiment, the apparatus 12 can be self-contained in the tire 10 to provide only pressure data. { on Those skilled in the art will recognize that the pressure detector employed in the invention can be employed with other detection devices and can be associated with annular antennas, to provide a 360 ° reading around the tire as illustrated in the prior art discussed above or in the US application awarded to the GoodYear Tire & Rubber Company, record of the agent No. DN 1996-082. When the apparatus 12 is incorporated in a tire, the surfaces of the inner liner 14, if the tire contains an inner liner, or the radially inner surface of the carcass layer 28, is placed on the surface of the inflation chamber 15, if no inner lining is used, with or without an adhesive. In the illustrated embodiment, the apparatus 12 is surrounded by an insulator (not shown) to protect the electronic components from parasitic electrical charges and from potentials applied by test equipment used to inspect the enclosures in retreading operations. The insulating gums described in the Goodyear application previously referred to are suitable for this purpose. The rubber patch 16 is the primary means by which the apparatus 12 is kept in place. Because it is preferred that the apparatus be insulated against the inflation chamber 15, so that dirt and foreign matter do not embed the pressure receiver, the entire surface area of the patch 16 that can be placed in contact with the surface of the chamber of inflation 15 is connected securely, that is to say it is preferred that the apparatus 12 be entirely circumscribed in the rubber patch 16. The connection of the patch 16 to the inflation chamber 15 can be made adhesively and / or by vulcanization when the tire is constructed, or it can be incorporated in a complete tire adhesively, for example when a tire is worn for retreading.

The patch 16 is an elastomeric material preferably of natural rubber. In the illustrated embodiment, the apparatus 12 is not connected to or vulcanized in the tire, but held in place by the surrounding relationship of the patch 16. To reduce the response time of the apparatus 12, and to provide rapid equilibrium between the pressure receiver and the inflation chamber 15, a path means 18 is provided between the pressure sensor and the inflation chamber 15, which allows the gas molecules to migrate to and from the pressure sensor and the inflation chamber 15. Although technically, the path means 18 may be provided as a sting in the elastomeric patch 16, in fact a sting has a tendency to be plugged by adhesives, the flow of rubber during vulcanization and grime, and some means must be provided to ensure that the path remains open. Accordingly, in the illustrated embodiment, path means 18 are provided as a string or string, preferably in the form of a discharge chord, a strip of woven fabric with discharge chords, or a hollow filament. These discharge chords are described by Pepe et al in U.S. Pat. No. 4,363,346 and by Sid-Ahmed in U.S. Pat. No. 5,221,382 and the refees cited therein.

Path means 18 may be longer than the patch 16 or may be positioned such that one end thereof extends beyond one edge of the patch 16 or is exposed on the surface of the patch 16. Path means 18 are placed on the apparatus 12 and the patch 16 are then placed on the path means 18 taking care that at least one end of the path means 18 remains outside the dimensions or the surface of the patch 16. In the illustrated embodiment, both ends of the path means 18 extend out of the dimensions of the patch 16. In tire tests, it has been shown that the path means 18, when filaments or discharge cords are used provide a path that makes the detector Pressure instantly responsive to changes in tire pressure. Since the discharge chords allow flow of simple molecules but prevent the flow of macro-molecules such as dirt, adhesive and rubber, the pressure detector remains free of debris and dirt. When the inner liner 14 is used in a tire, the apparatus 12 is placed close to the inner liner 14, the path means 18 are placed on the apparatus 12, the patch 16 is placed on the path means 18 and the apparatus 12 is placed on the path means 18. connects to the inner liner 14. While the invention has been specifically illustrated and described, those skilled in the art will recognize that the invention can be modified and practiced in a variety of ways, without departing from the spirit of the invention. The invention is limited only by the scope of the following claims.

Claims (9)

1. CLAIMS 1. - A tire comprising an exterior surface including a floor contact surface, an interior inflation chamber, and a pressure sensor, encapsulated by means associated with a radially inner surface of the inflation chamber, and means capillarity absorbers associated with the pressure sensor, whereby the capillarity-absorbing means provide a path for pressure equilibrium between the pressure sensor and the inflation chamber.
2. 2. The tire according to claim 1, characterized in that the means for absorbing by capillary action are chosen from the group consisting of gas absorbent textile cords, hollow filaments and woven textile cords or filaments.
3. 3. The tire according to claim 1, characterized in that the encapsulation means comprise a rubber patch surrounding the pressure sensor, the rubber patch is connected to a radially inward surface of the inflation chamber.
4. 4. A tire comprising at least two parallel annular heels, shell layers wrapped around the beads, surface contact with the floor placed on the carcass layers in a crown area of the tire, side walls disposed between the surface of the tire, contact with the floor and beads, an inflation chamber radially inward of the contact surface with the floor and axially between the side walls, and an encapsulated detection system associated with the inflation chamber, the detection system comprises a apparatus for transmitting tire pressure data, comprising: a transponder for responding to predetermined signals that trigger a response signal for transmitting pressure data, a pressure sensor, a flake associated with the transponder having at least sufficient capacity to handle feeding a pressure detector and transmitting tire pressure data, encapsulation means ion for the pressure sensor and absorbing media by capillary action to provide pressure equilibrium between the encapsulated pressure detector and the inner chamber.
5. 5. The tire according to claim 4, characterized in that an inner liner is placed radially inward of the carcass layer and the pressure detector is close to the inner liner and the encapsulation means are connected to the inner liner.
6. 6. The tire according to claim 4, characterized in that the capillary-absorbing means are chosen from the group consisting of gas absorbing textile cords, hollow filaments and woven textile cords or filaments.
7. 7. Method for connecting a pressure detector with a tire inflation chamber, characterized in that it comprises the steps of: (a) placing a pressure detector in a tire construction in a substantially flat low-flex location, which corresponds to a surface of an inflation chamber in a tire, (b) placing absorption means by capillarity on the pressure sensor, (c) connecting a rubber patch of the rubber material with the surface of an inflation chamber on the pressure sensor and the means of absorption by capillarity, wherein the means of absorption by capillarity have at least one end outside the dimensions of the rubber patch.
8. 8. - The tire according to claim 7, characterized in that it further comprises the steps of: (a) building the tire with an inner liner comprising a radially inward surface of the inflation chamber, (b) placing the pressure in the inner lining, (c) placing the absorption means by capillarity on the pressure sensor, and (d) adhesively attaching a rubber patch to the inner liner covering the pressure sensor and partially covering the absorption means by capillarity
9. 9. The tire according to claim 7, characterized in that it comprises the step of selecting the absorbent means by capillarity of the group consisting of: cotton discharge cords, polyester-based discharge cords, hollow filaments and their mixtures.