Patent Description:
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.

The use of tread wear indicators that are formed on a tire tread before or after curing is known in the art. For example, prior art mechanical tread wear indicators include color indicia disposed below certain tread elements, tie bars disposed in the tread grooves, or characters formed in the tread elements, all of which provide a visual indicator of wear. Such mechanical indicators may be difficult for a vehicle operator to see, and thus do not easily provide information to the operator.

In addition, it is often desirable to collect electronic data for the wear state of the tire. The data can be communicated to electronic systems of the vehicle, such as vehicle stability and/or braking systems, in order to provide improved control of the vehicle and to monitor or track driving behavior. Mechanical tread wear indicators are not able to provide such data to electronic systems of the vehicle.

To provide an indication of tire wear to vehicle electronic systems, prior art indirect wear estimation techniques were developed. Such techniques involve estimation of tire wear through certain tire and vehicle parameters, rather than direct measurement of wear. For example, tire pressure, tire temperature, vehicle speed, vehicle mileage, vehicle acceleration and other parameters may be employed to estimate tire wear. Such indirect estimation of tire wear can be difficult to perform accurately, and typically involves complex modeling techniques.

In order to provide a wear indication to vehicle electronic systems based on a direct measurement of tire wear, prior art electronic wear sensors were developed. Such sensors are known in the art as direct wear sensors, as they attempt to directly measure tire wear, rather than providing an estimate from indirect means. By way of example, prior art direct wear sensors include resistance-based electronic sensors that typically are incorporated into tread elements of tires. As the tread element wears, resistors in the sensor also wear, leading to a change in the electrical resistance of the sensor. By measuring the resistance of the sensor and transmitting the measured resistance data to a processor, wear of the tread can be determined.

While prior art direct wear sensors are acceptable for their intended purpose, many such sensors are difficult to install in the tire. Other direct wear sensors cannot withstand the harsh operating environment of the tire for a prolonged period, such as the recommended life of the tire. Still other direct wear sensors are not capable of maintaining precise and repeatable indication of tire wear over the recommended life of the tire.

As a result, it is desirable to develop a direct wear sensor system for a vehicle tire that includes a structure which is easy to install in the tire, withstands the operating environment of the tire, accurately indicates tire wear in a repeatable manner, and is capable of transmitting a wear indication to an electronic control system of the vehicle.

<CIT> describes a tire with a tread element with a polymer plug for tread wear sensing. A chamber is formed in the tread element and a sensor unit is mounted to the tire. The polymer plug includes a wire being disposed in the chamber, the wire including proximal ends and a distal end near the radially outer surface of the tread. An electrical circuit is formed by each proximal end of the wire electrically contacting a respective one of the sensor unit electrical contacts, whereby. when the selected one of the tread elements wears down to the distal end of the wire, the distal end of the wire breaks, thereby breaking the electrical circuit.

<CIT> describes a tire with a polymer plug for wear sensing in accordance with the preamble of claim <NUM>.

Another tire comprising a sensor device integrated in a tire tread for determining tread wear of the tire is known from <CIT>.

<CIT> describes a temperature sensor and a polymer plug. An epoxy material is filled in a chamber of the tire and cured.

The invention relates to a tire in accordance with claim <NUM> and to methods of manufacturing in accordance with claims <NUM> or <NUM> respectively.

According to an aspect of an exemplary embodiment of the invention, a tire with a polymer plug for tread wear sensing is provided. The tire includes a pair of sidewalls, each one of which extends radially outwardly from a respective bead area to a ground-contacting tread. The tread is formed with a plurality of tread elements and a radially outer surface. A chamber is formed in a selected one of the tread elements. A sensor unit is mounted to the tire and includes a pair of electrical contacts. The polymer plug includes a wire disposed in the chamber. The wire includes proximal ends and a distal end near a radially outer surface of the tread. A liquid polymer is injected into the chamber and cured. An electrical circuit is formed by each proximal end of the wire electrically contacting a respective one of the sensor unit electrical contacts. When the selected one of the tread elements wears down to the distal end of the wire, the distal end of the wire breaks, which breaks the electrical circuit. A notice is transmitted by the sensor unit when the electrical circuit has broken.

"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.

"CAN bus" is an abbreviation for controller area network.

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

"Footprint" means the contact patch or area of contact created by the tire tread with a flat surface, such as the ground, as the tire rotates or rolls.

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

"Radially inward" and "radially inwardly" refer to a radial direction that is toward the central 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.

"TPMS" means a tire pressure monitoring system, which is an electronic system that measures the internal pressure of a tire and is capable of communicating the pressure to a processor that is mounted on the vehicle and/or is in electronic communication with electronic systems of the vehicle.

"Tread element" or "traction element" means a rib or a block element defined by a shape having adjacent grooves.

An exemplary embodiment of the tire <NUM> with a polymer plug for tread wear sensing of the present invention is presented in <FIG>. With particular reference to <FIG>, the tire <NUM> with a polymer plug <NUM> provides a system for indicating the wear on one or more tires supporting a vehicle <NUM>. While the vehicle <NUM> is depicted as a commercial truck, the invention is not to be so restricted. The principles of the invention find application in other vehicle categories, such as passenger vehicles, off-the-road vehicles and the like, in which vehicles may be supported by more or fewer tires than shown in <FIG>.

Turning to <FIG>, the tire <NUM> includes a pair of bead areas <NUM>, each one of which is formed with a bead core <NUM> that is embedded in the respective bead areas. Each one of a pair of sidewalls <NUM> extends radially outwardly from a respective bead area <NUM> to a ground-contacting tread <NUM>. The tread <NUM> is formed with multiple tread elements or tread blocks <NUM> and includes a radially outer surface <NUM>. The tire <NUM> is reinforced by a carcass <NUM> that toroidally extends from one bead area <NUM> to the other bead area, as known to those skilled in the art. 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> (<FIG>) as known in the art, forming an internal cavity <NUM>.

A sensor unit <NUM> preferably is mounted to the tire <NUM>. The sensor unit <NUM> detects certain real-time parameters of the tire <NUM>, and preferably includes a pressure sensor to sense the inflation pressure within a cavity <NUM> of the tire, and a temperature sensor to sense the temperature of the tire and/or the temperature in the cavity. The sensor unit <NUM> may be a commercially available tire pressure monitoring system (TPMS) module or sensing unit.

The sensor unit <NUM> preferably also includes a processor and memory to store tire identification (ID) information for each specific tire <NUM>. For example, the tire ID may include manufacturing information for the tire <NUM>, including: the 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 ID may also include a service history or other information to identify specific features and parameters of each tire <NUM>.

The sensor unit <NUM> preferably further includes an antenna for wirelessly transmitting <NUM> (<FIG>) measured parameters and tire ID data to a remote processor for analysis, such as a processor integrated into a vehicle electronic control unit and/or CAN bus.

The sensor unit <NUM> may be mounted to the tire <NUM> using a container <NUM>, which receives the sensor unit and is attached to the innerliner <NUM> by an adhesive. Preferably, the container <NUM> is flexible and is formed of an elastomer or polymer. The container <NUM> may be attached to the tire <NUM> before or after curing of the tire, and the sensor unit <NUM> preferably is inserted into the container after curing of the tire. As shown in <FIG>, the sensor unit <NUM> preferably includes a rigid housing <NUM> formed with a base <NUM>. A pair of electrical contacts <NUM> are mounted on the base <NUM> and extend through the housing <NUM>.

Turning to <FIG>, a chamber <NUM> is formed in a selected tread element <NUM>, preferably before the container <NUM> and the sensor unit <NUM> are attached to the tire <NUM>. The chamber <NUM> extends from the internal cavity <NUM> into the selected tread element <NUM>, but not completely through the selected tread element to the tread surface <NUM>.

To form the chamber <NUM>, different techniques may be employed. For example, when the tire <NUM> is a green or uncured tire, an object such as a nail may be inserted into the green tire from the direction of the cavity <NUM> and into the selected tread element <NUM>. The object includes a length that provides a corresponding radial length <NUM> for the chamber <NUM>. The length <NUM> ends at a set distance <NUM> below the tread outer surface <NUM>. The object also includes a diameter that provides a corresponding diameter <NUM> for the chamber <NUM>. The diameter <NUM> of the chamber <NUM> ensures that a wire <NUM>, to be described below, may be inserted into the chamber. Once the object is inserted into the tire <NUM>, the tire is cured. After the tire <NUM> has been cured, the object is removed, which creates the chamber <NUM>. Preferably, the object includes a surface coating, such as a low-friction coating, which enables easy removal of the nail after the tire has been cured.

When the tire <NUM> is a cured tire, the chamber <NUM> may be formed by drilling from the direction of the cavity <NUM> and into the selected tread element <NUM>. When the chamber <NUM> is formed by drilling, the chamber includes the radial length <NUM> and the diameter <NUM>. Of course, other techniques that are known to those skilled in the art may be employed to form the chamber <NUM> in a cured or uncured tire <NUM>.

With reference to <FIG>, the tire with a polymer plug <NUM> includes a conductive wire <NUM>. The wire <NUM> preferably is an insulated wire, but may be an uninsulated wire, depending on particular design considerations. The wire is formed in a U-shape and thus has proximal ends <NUM> and a distal end <NUM>. The proximal ends <NUM> of the wire <NUM> contact the electrical contacts <NUM> of the sensor unit <NUM>, as will be described in greater detail below. Optionally, the proximal ends <NUM> of the wire <NUM> may be attached to a printed circuit board <NUM> through a conductive attachment <NUM>. The printed circuit board <NUM> provides a stable connection point for the proximal ends <NUM> of the wire <NUM>. The printed circuit board <NUM> is formed with an opening <NUM>, which enables the distal end <NUM> of the wire <NUM> to be inserted through the circuit board.

The distal end <NUM> of the wire <NUM> is inserted into the chamber <NUM> from the tire cavity <NUM>, and the printed circuit board <NUM> provides a positive mechanical stop for the wire in the chamber. The length <NUM> and diameter <NUM> of the chamber <NUM> allow the wire <NUM> to be received and seat in the chamber, with the distal end <NUM> of the wire near the tread surface <NUM>. Preferably, the distal end <NUM> of the wire <NUM> is a set distance <NUM> below the tread surface <NUM>.

Referring to <FIG>, once the wire <NUM> is seated in the chamber <NUM>, a liquid polymer <NUM> is injected through the printed circuit board opening <NUM> an into the chamber. The liquid polymer <NUM> is then cured to solidify it.

Turning to <FIG>, after the liquid polymer <NUM> has been cured, the container <NUM> is attached to the tire <NUM>. More particularly, the container <NUM> includes a base <NUM> that is attached to the innerliner <NUM> with an adhesive. The container base <NUM> is formed with an opening <NUM>, which enables the proximal ends <NUM> of the wire <NUM> to pass into the container <NUM>. The sensor unit <NUM> is installed by inserted it into the container <NUM>, which receives and secures the sensor unit. The sensor unit <NUM> is rotated to enable each sensor electrical contact <NUM> (<FIG>) to contact a respective proximal end <NUM> of the wire <NUM>.

Turning to <FIG> and <FIG>, operation of the tire with a polymer plug <NUM> is shown. With particular reference to <FIG>, a continuous electrical circuit is formed by the wire <NUM> and the contact of each proximal wire end <NUM> with each respective electrical contact <NUM> of the sensor unit <NUM>. The distal end <NUM> of the wire <NUM> is disposed at a predetermined distance <NUM> (<FIG>) below the radially outer surface <NUM> of the tread <NUM>, which corresponds to a minimum recommended tread depth.

Referring to <FIG>, as the tread <NUM> wears, the cured liquid polymer <NUM> also wears. When the tread <NUM> and the cured liquid polymer <NUM> wear down to the wire <NUM>, the distal end <NUM> of the wire <NUM> breaks, creating a break in the electrical circuit formed by the wire and the contact of each proximal wire end <NUM> with each respective sensor unit electrical contact <NUM>. The sensor unit <NUM> senses the break in the electrical circuit, and wirelessly transmits <NUM> a notice <NUM> that the electrical circuit has broken and/or that the minimum recommended tread depth has been reached.

The notice <NUM> transmitted <NUM> by the sensor unit <NUM> may be sent to a remote processor, such as a processor that is integrated into a vehicle electronic control unit, CAN bus, and/or a cloud-based server. The notice <NUM>, by communicating that the minimum tread depth has been reached, thus indicates when replacement or retreading of the tire <NUM> should take place.

In this manner, the tire with a polymer plug <NUM> for tread wear sensing of the present invention indicates tire wear with components that are mounted within the tire <NUM>, and does not require sensors that are external to the tire. The tire with a polymer plug <NUM> provides a direct wear sensor system for a vehicle tire <NUM> that includes a structure which is easy to install in the tire, withstands the operating environment of the tire, accurately indicates tire wear in a repeatable manner, and is capable of transmitting a wear indication to an electronic control system of the vehicle <NUM>.

The present invention also includes a method of determining wear of a tire using a polymer plug, and a method of forming a tire with a polymer plug for indicating tread depth. Each method includes steps in accordance with the description that is presented above and shown in <FIG>.

Claim 1:
A tire with a polymer plug for tread wear sensing,
wherein the tire (<NUM>) comprises a pair of sidewalls (<NUM>), each one of which extends radially outwardly from a respective bead area (<NUM>) to a tread (<NUM>),
wherein the tread (<NUM>) is formed with a plurality of tread elements (<NUM>) and a radially outer surface (<NUM>),
wherein a chamber (<NUM>) is formed in a selected one of the tread elements (<NUM>),
wherein a sensor unit (<NUM>) is mounted to the tire (<NUM>), the sensor unit (<NUM>) including a pair of electrical contacts (<NUM>),
wherein the polymer plug (<NUM>) includes a wire (<NUM>) being disposed in the chamber (<NUM>), the wire (<NUM>) including proximal ends (<NUM>) and a distal end (<NUM>) near the radially outer surface (<NUM>) of the tread (<NUM>),
wherein an electrical circuit (<NUM>) is formed by each proximal end (<NUM>) of the wire (<NUM>) electrically contacting a respective one of the sensor unit electrical contacts (<NUM>), whereby when the selected one of the tread elements (<NUM>) wears down to the distal end (<NUM>) of the wire (<NUM>), the distal end (<NUM>) of the wire breaks, thereby breaking the electrical circuit (<NUM>),
wherein a cured solidified liquid polymer is provided in the chamber (<NUM>),
and wherein the proximal ends (<NUM>) of the wire (<NUM>) are attached to a printed circuit board (<NUM>),
characterized in that the printed circuit board (<NUM>) is formed with an opening (<NUM>) and the distal end (<NUM>) of the wire (<NUM>) is inserted through the circuit board (<NUM>) into the chamber (<NUM>).