Patent Description:
Tires experience many conditions that are beneficial to monitor. Such tires include pneumatic tires, non-pneumatic tires, automotive tires, passenger tires, truck tires, commercial tires, off-the-road tires, aircraft tires, spacecraft tires, and the like. Reference herein is made generally to a tire by way of example, with the understanding that the invention applies to any type of tire.

In the manufacture of a pneumatic tire, the tire is typically built on the drum of a tire-building machine, which is known in the art as a tire building drum. Numerous tire components are wrapped about and/or applied to the drum in sequence, forming a cylindrical-shaped tire carcass. The tire carcass is then expanded into a toroidal shape for receipt of the remaining components of the tire, such as a belt package and a rubber tread. The completed toroidally-shaped unvulcanized tire carcass, which is known in the art at that stage as a green tire, is then inserted into a mold or press for forming of the tread pattern and curing or vulcanization.

For many modern tires, it is often desirable to mount electronic sensor units to the tires either before or after curing. Such sensor units enable temperature, pressure and/or other parameters or conditions of the tire to be continuously monitored during vehicle operation. The sensor units typically include an integrated circuit that processes and stores information. One or more sensors are integrated with or are electronically connected to the integrated circuit. An antenna for receiving and transmitting a signal to an external reader is also electronically connected to the integrated circuit and may be carried on a substrate with the integrated circuit. Other electronic components, including power means such as a battery or energy harvesting structure, signal converters, and the like, are also typically integrated with the integrated circuit.

In the prior art, such electronic sensor units have often been attached to the inside surface of a pneumatic tire, which defines the cavity containing the inflation gas. Such a location has enabled the sensor unit to continuously sense parameters such as the temperature and pressure inside the tire cavity, while not interfering with the structure of the tire.

While such prior art sensor units are acceptable for many uses, it is desirable to monitor the actual temperature and other parameters at specific structural locations inside the tire structure during use on a vehicle, which cavity-based sensors cannot do. For example, monitoring the actual temperature at the edge of the belts in the belt package would be advantageous in predicting ongoing tire performance and potential tire replacement, as well as in providing immediate information to a driver or dispatcher to adjust the speed of a vehicle before potential thermal damage to the tire may occur. However, accurate measurement of the actual temperature at such a location requires the sensor unit to be permanently embedded into the tire structure.

In addition, as the demand for monitoring data increases, the size of the components of the sensor unit has often increased. For example, the sensor size has often increased in order to collect more data and/or monitor parameters with a greater sensitivity, power-related component size has increased due to increased power requirements for increased monitoring and transmission, and input/output component size has increased due to increased transmission timing and/or range.

Prior art embedded sensor units have experienced disadvantages, particularly with such increased component size requirements. More particularly, an integrated sensor unit on a single substrate is not flexible enough to be durably embedded inside the tire structure. Such prior art sensor units often undesirably experience detachment or cracking of components and/or the substrate during curing or operation of the tire, which shortens the life of the sensor unit.

As a result, it is desirable to develop a flexible sensor unit that may be embedded in a tire structure, which maintains durability of the tire and the life of the sensor unit, while also providing increased sensor functionality.

<CIT> discloses a sensor in accordance with the preamble of claim <NUM>.

<CIT> shows an elastically deformable integrated circuit device comprising several rigid substrate islands connected via an elastically deformable connection.

<CIT> and <CIT> disclose a transmitting device for wireless transmission of measured parameters that can be fastened on a surface of a tire.

The invention relates to a flexible sensor unit in accordance with claim <NUM> and to a tire in accordance with claim <NUM>.

According to an aspect of an exemplary embodiment of the invention, a flexible sensor unit for embedding in a tire includes a plurality of individual circuit boards. Each circuit board includes at least one electronic component. The at least one electronic component includes at least one of a radio frequency identification integrated circuit, a microcontroller unit, at least one sensor, a power source and a boost converter. Each one of a plurality of electrically conductive flexible connecting ribbons extends between selected circuit boards. An end ribbon is electrically connected to at least one of the circuit boards, and an antenna is disposed on the end ribbon. The antenna transmits data from the at least one sensor, as processed by the microcontroller unit, and identification data from the radio frequency identification integrated circuit, to an external reader.

According to another aspect of an exemplary embodiment of the invention, a tire includes a flexible sensor unit. The tire and flexible sensor unit combination includes a tire, which in turn includes a pair of bead areas, a sidewall extending from each respective bead area to a tread, a carcass extending toroidally between each of the bead areas, and a belt reinforcement package disposed between the tread and the carcass. A flexible sensor unit is embedded in the tire. The flexible sensor unit includes a plurality of individual circuit boards. Each circuit board includes at least one electronic component. The at least one electronic component includes a radio frequency identification integrated circuit, a microcontroller unit, at least one sensor, a power source and a boost converter. Each one of a plurality of electrically conductive flexible connecting ribbons extends between selected ones of the circuit boards. An end ribbon is electrically connected to at least one of the circuit boards, and an antenna is disposed on the end ribbon.

Preferably, the flexible sensor unit is inserted into the tire before curing of the tire.

"Axial" and "axially" mean lines or directions that are parallel to the axis of rotation of the tire.

"Axially inward" and "axially inwardly" refer to an axial direction that is toward the axial center of the tire.

"Axially outward" and "axially outwardly" refer to an axial direction that is away from the axial center of the tire.

"Equatorial plane (EP)" means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.

"Lateral" and "laterally" are used to indicate axial directions across the tread of the tire.

"Radial" and "radially" mean lines or directions that are perpendicular to the axis of rotation of the tire.

"Radially outward" and "radially outwardly" refer to a radial direction that is away from the central axis of rotation of the tire.

By way of introduction of the flexible sensor unit for a tire of the present invention, <FIG> show a sensor construction of the prior art and a tire. Turning to <FIG>, a tire <NUM> includes a pair of bead areas <NUM> (only one shown) and a bead core <NUM> embedded in each bead area. Each one of a pair of sidewalls <NUM> extends radially outward from a respective bead area <NUM> to a ground-contacting or ground-engaging tread <NUM>. The tire <NUM> is reinforced by a carcass <NUM> that toroidally extends from one bead area <NUM> to the other bead area. The carcass <NUM> includes at least one ply <NUM> that preferably winds around each bead core <NUM>. An innerliner <NUM> is formed on the inner or inside surface of the carcass <NUM>. The tire <NUM> is mounted on the flange of a wheel or rim <NUM>, as known in the art.

When the tire <NUM> is mounted on the wheel <NUM>, a cavity <NUM> is formed and is filled with a pressurized fluid, such as air. An integrated sensor, such as a tire pressure monitoring system (TPMS) sensor unit <NUM>, may be mounted on the innerliner <NUM> to measure the pressure and/or temperature in the cavity <NUM>.

As shown in <FIG>, a belt reinforcement package <NUM> is disposed between the carcass <NUM> and the tread <NUM>. The belt reinforcement package <NUM> may employ specific configurations as desired. For example, the belt reinforcement package <NUM> may include at least one of a radially outer belt structure <NUM> and a radially inner belt structure <NUM>, and an intermediate belt structure <NUM> disposed between the radially outer belt structure and the radially inner belt structure.

As mentioned above, in the prior art, the integrated TPMS sensor unit <NUM> has been attached to the innerliner <NUM>, which enables the sensor to continuously sense parameters such as the temperature and pressure inside the tire cavity <NUM>, while not interfering with the structure of the tire <NUM>. However, the TPMS sensor unit <NUM> cannot monitor the actual temperature and other parameters at specific structural locations inside the tire <NUM> during use on a vehicle, such as at the edge of the belts <NUM>, <NUM> and <NUM> in the belt package <NUM>.

With reference to <FIG>, a prior art sensor unit <NUM> that may be embedded in the structure of the tire <NUM> (<FIG>) is shown. The prior art sensor unit <NUM> has been disposed between the belt package <NUM> and the tread <NUM>, between the belt package and the carcass <NUM>, or between belts <NUM>, <NUM> and/or <NUM> within the belt package. The prior art sensor unit <NUM> includes a single substrate <NUM> on which electronically interconnected components are formed.

For example, the prior art sensor unit <NUM> includes a temperature sensor <NUM> and a power source <NUM>, such as an energy or power harvesting unit. A boost converter <NUM>, which is a power converter that adjusts voltage and/or current between the power source <NUM> and the temperature sensor <NUM> and other powered components, is also included. A microcontroller unit (MCU) <NUM> receives the data from the temperature sensor <NUM> and processes it for transmission. A radio frequency identification (RFID) integrated circuit <NUM> includes information to identify the sensor unit <NUM>. An antenna <NUM> transmits data from the sensor unit <NUM> to an external reader and/or processor, as known to those skilled in the art.

As mentioned above, the prior art integrated sensor unit <NUM>, which includes a single substrate <NUM>, is not flexible enough to be durably embedded inside the structure of the tire <NUM>. Such prior art sensor units <NUM> often undesirably experience detachment or cracking of components and/or the substrate <NUM> during curing or operation of the tire <NUM>, which shortens the life of the sensor unit.

Turning to <FIG> an exemplary embodiment of a flexible sensor unit <NUM> for a tire of the present invention is shown. The flexible sensor unit <NUM> is a segmented sensor unit that is made up of individual circuit boards <NUM> which are electronically connected to one another by electrically conductive flexible connecting traces or ribbons <NUM>. Preferably, each circuit board <NUM> is made of a resilient yet compliant material, such as a multi-layer flexible polyimide and/or fiberglass. The material that is employed may dictate the components that are disposed on each circuit board <NUM>. For example, a multi-layer flexible polyimide may be less densely populated to retain flexibility, while fiberglass may be more densely populated to reduce the footprint of the circuit board and thereby minimize stresses on components. The connecting ribbons <NUM> are made of single-layer polyimide to provide flexibility and electrical conductivity.

Preferably, each circuit board <NUM> is formed with specific electronic components. For example, a first circuit board 102A may include a radio frequency identification (RFID) integrated circuit <NUM>. A second circuit board 102B may include a microcontroller unit <NUM> and at least one sensor <NUM>. A third circuit board 102C may include a power source <NUM>.

A fourth circuit board 102D may include a boost converter <NUM>.

A first ribbon 104A electrically connects the first circuit board 102A, which contains the RFID integrated circuit <NUM>, and the second circuit board 102B, which contains the microcontroller unit <NUM> and the sensor <NUM>. A second ribbon 104B electrically connects the third circuit board 102C, which contains the power source <NUM>, and the fourth circuit board 102D, which contains the boost converter <NUM>. A third ribbon 104C electrically connects the second circuit board 102B and the fourth circuit board 102D.

An end ribbon <NUM> preferably is disposed on one end of the flexible sensor unit <NUM>. The end ribbon <NUM> preferably is made of flexible single-layer polyimide. Disposed on the end ribbon <NUM> is an antenna <NUM>. The antenna <NUM> is electronically connected to the first circuit board 102A, which contains the RFID integrated circuit <NUM>, and to the third circuit board 102C, which contains the power source <NUM>.

As mentioned above, the first circuit board 102A may include the RFID integrated circuit <NUM>. The RFID integrated circuit <NUM> includes information to identify the sensor unit <NUM> and a tire <NUM> in which the sensor unit is embedded. Such identification information may include manufacturing information for the tire <NUM>, such as: the tire type; tire model; size information, such as rim size, width, and outer diameter; manufacturing location; manufacturing date; a treadcap code that includes or correlates to a compound identification; and a mold code that includes or correlates to a tread structure identification. The tire identification enables correlation of data gathered by the sensor <NUM> with the specific tire <NUM> to provide local or central tracking of the tire, its current condition, and/or its condition over time. The RFID integrated circuit <NUM> transmits data gathered by the sensor <NUM> and processed by the microcontroller unit <NUM> through a radio frequency signal using the antenna <NUM>.

Also as mentioned above, the second circuit board 102B may include the microcontroller unit <NUM> and the sensor <NUM>. The microcontroller unit <NUM> processes and stores data from the sensor <NUM>. The sensor <NUM> is electronically connected to the microcontroller unit <NUM> and may be integrated into the microcontroller unit. The sensor <NUM> preferably is a temperature sensor that measures the temperature of the tire structure in the region where the sensor is embedded, as will be described in greater detail below. Additional sensors <NUM> may be employed, and may include one or more of a pressure sensor to measure a pressure of the structure of the tire <NUM>, a wear sensor to measure wear of the tire, a force sensor to measure forces on the tire, a strain sensor to measure strains on the tire, and an acceleration sensor to measure acceleration of the tire.

The third circuit board 102C includes the power source <NUM> for the sensor unit <NUM>. Preferably, the power source <NUM> is an energy harvesting or power harvesting unit with a wireless power receiver that may be configured to receive a radio frequency power signal through the antenna <NUM>. The radio frequency power signal may be an ultra high frequency (UHF) signal in a range of from <NUM> megahertz (MHz) to <NUM> gigahertz (GHz). The power source <NUM> optionally includes a non-rechargeable battery, a rechargeable battery and/or a capacitor to store energy for the sensor unit <NUM>.

The fourth circuit board 102D includes the boost converter <NUM>. The boost converter <NUM> converts voltage and/or current from the power source <NUM> to an acceptable level for the sensor <NUM>, microcontroller unit <NUM>, and the RFID integrated circuit <NUM>.

The antenna <NUM> is formed on the end ribbon <NUM>, and is flexible, which enables the sensor unit <NUM> to be embedded in the tire <NUM>, as will be described in greater detail below. The antenna <NUM> transmits data from the sensor <NUM>, as processed by the microcontroller unit <NUM>, and identification data from the RFID integrated circuit <NUM>, to an external reader for processing and/or storage. The antenna <NUM> may also receive signals to actuate the sensor unit <NUM> and may receive a radio frequency power signal for the power source <NUM>.

The flexible sensor unit <NUM> may be a passive radio frequency unit that is actuated by the external reader. More particularly, the sensor <NUM>, the microcontroller unit <NUM>, and the RFID integrated circuit <NUM> may remain in a passive state. When the external reader is in proximity with the sensor unit <NUM>, the antenna <NUM> receives a wireless signal from the reader that actuates the sensor <NUM>, the microcontroller unit <NUM>, and the RFID integrated circuit <NUM>. The sensor <NUM> takes its respective measurements, and data from the sensor measurements is processed by the microcontroller unit <NUM>. The data is stored in the microcontroller unit <NUM> and/or the RFID integrated circuit <NUM> and transmitted wirelessly by the antenna <NUM> from the sensor unit <NUM> to the external reader. Alternatively, the sensor <NUM> may be powered by the power source <NUM> to take measurements at predetermined intervals, which are processed by the microcontroller unit <NUM> and are transmitted with identification information from the RFID integrated circuit <NUM> by the antenna <NUM> when the sensor unit <NUM> is in proximity with the external reader.

With particular reference now to <FIG>, the above-described structure of the flexible sensor unit <NUM> enables the unit to be inserted into a specific structural location in the tire <NUM> before curing. In such a case, and when the sensor <NUM> is a temperature sensor, the sensor unit <NUM> may optionally be employed to detect temperature profiles within the tire <NUM> during curing. In such a case, the flexible sensor unit <NUM> may be disposed in the last part of the tire <NUM> to cure, which is referred to as the point of least cure. By being located at the point of least cure in the tire <NUM>, the sensor unit <NUM> may measure the actual integrated time and temperature history during the curing of the tire, which may be used to control the cycle time of the curing press. Such a measurement of actual temperature at the point of least cure of the tire <NUM> by the sensor unit <NUM> may be more reliable than prediction techniques. In addition, because prediction techniques often add more curing time as a precautionary factor, measurement of actual temperature with the sensor unit <NUM> may reduce the curing time that is required for the tire <NUM>, thereby increasing the efficiency of the curing process.

Once the tire <NUM> is cured, the flexible sensor unit <NUM> is permanently disposed at its selected location inside the tire. The segmented construction of the sensor unit <NUM>, including the resilient circuit boards <NUM> that are interconnected by flexible ribbons <NUM>, enables placement of the sensor unit in the tire <NUM> without damage to the structural components of the tire.

The flexible sensor unit <NUM> may also be employed, when the sensor <NUM> is a temperature sensor, to detect temperature within the tire <NUM> during its use on a vehicle. For example, the sensor unit <NUM> may be disposed at the edge of the belt reinforcement package <NUM> to measure the belt edge temperature. Belt edge temperature is often an indicator of performance and/or life issues for the tire <NUM>, and by detecting temperature in the structure at the edge of the belt reinforcement package <NUM>, the flexible sensor unit <NUM> provides data indicating when tire replacement is recommended. The flexible sensor unit <NUM> may also track a temperature versus time history at a specific location, such as the belt edge or a belt splice, in order to provide data to predict when tire replacement should occur. Moreover, the flexible sensor unit <NUM> may be disposed in other structural areas of the tire <NUM> to monitor temperatures at those locations when the sensor <NUM> is a temperature sensor.

In this manner, the flexible sensor unit <NUM> provides a structure that may be embedded in a tire <NUM>, and maintains durability of the tire and the life of the sensor unit, while also providing increased sensor functionality. The segmented construction of the sensor unit <NUM>, including the resilient circuit boards <NUM> that are interconnected by flexible ribbons <NUM> provides increased structural flexibility, as well as modularity of components. The segmented construction of the sensor unit <NUM> also prevents structural issues within the tire <NUM>.

The present invention also includes a method of forming a tire <NUM> with a flexible sensor unit <NUM>. The method includes steps in accordance with the description that is presented above and shown in <FIG>.

Claim 1:
A flexible sensor unit for embedding in a tire (<NUM>), the flexible sensor unit (<NUM>) comprising:
a plurality of individual circuit boards (102A, 102B, 102C, 102D), wherein each circuit board (102A, 102B, 102C, 102D) includes at least one electronic component, the at least one electronic component including at least one of a radio frequency identification integrated circuit (<NUM>), at least one a microcontroller unit (<NUM>), at least one sensor (<NUM>), at least one power source (<NUM>) and at least one boost converter (<NUM>);
a plurality of electrically conductive flexible connecting ribbons (104A, 104B) or structures, each connecting ribbon (104A, 104B) or structure extending between selected ones of the individual circuit boards (102A, 102B, 102C, <NUM>);
an end ribbon (<NUM>) or structure being electrically connected to at least one of the circuit boards (102A, 102B, 102C, 102D); and
an antenna (<NUM>) being disposed on the end ribbon (<NUM>);
wherein the antenna (<NUM>) is configured to transmit data from the at least one sensor (<NUM>) as processed by the microcontroller unit (<NUM>) and to transmit identification data from the radio frequency identification integrated circuit (<NUM>), to an external reader, characterized in that the connecting ribbons (104A, 104B) or structures are made of a single-layer polyimide.