Patent Description:
Multiple pneumatic tires support a vehicle and are designed to perform for relatively long periods of time. However, even long-life pneumatic tires are subject to air pressure losses due to puncture by nails and other sharp objects, temperature changes, and/or diffusion of air through the tire itself.

Since air diffusion reduces tire pressure over time, the pneumatic tires may repeatedly become underinflated. Accordingly, vehicle operators or fleet operators must in turn repeatedly act to maintain recommended air pressures in the vehicle tires to avoid reduced fuel economy, tire life, and/or vehicle braking and handling performance. To assist in the maintenance of recommended tire pressure, various types of systems that monitor the air pressure inside the tire have been developed.

One approach to the monitoring and/or measurement of tire pressure has been to measure the pressure of a tire mounted on a vehicle as the vehicle drives over a station and the tire passes over a sensor mounted in the station, which is known in the art as a drive over reader. As the tire drives onto the drive over reader, the reader measures the pneumatic pressure inside the tire. For example, an array of load sensors may be disposed in the drive over reader, which measures the force exerted by the tire.

The tire pressure is determined from the measured force and may incorporate tire information and/or vehicle information. The advantages of determining tire pressure with a drive over reader include positioning of the tire over the reader contact surface during a short time interval, which enables the pressure to be determined without invading or accessing the tire cavity.

As with any measurement technique, the precision and repeatability of the pressure determination by the drive over reader are important considerations. For example, the determination of tire pressure by a drive over reader may be influenced by tire temperature. Therefore, after the pressure of a tire has been determined by the drive over reader, it is beneficial to evaluate the pressure measurements of the drive over reader.

As a result, there is a need in the art for a system and method of evaluating the pressure that is determined by a drive over reader.

<CIT> describes a system in accordance with the preamble of claim <NUM>.

Similar systems are also known from <CIT> and <CIT>.

<CIT> describes a traffic monitoring system including axle weight measurement, tire pressure monitoring and suspension monitoring.

According to an aspect of an exemplary embodiment of the invention, a system for evaluation of pressure of at least two tires supporting a vehicle is provided. The system includes a drive over reader, which includes a sensor array. A first pressure indication, which is a pressure indication for a first tire, is determined by the drive over reader. A second pressure indication, which is a pressure indication for a second tire, is determined by the drive over reader. A maximum differential threshold is provided. A pressure differential is determined by comparing the first pressure indication to the second pressure indication. A notice is generated by the drive over reader when the pressure differential exceeds the maximum differential threshold.

According to another aspect of an exemplary embodiment of the invention, a method for evaluation of pressure of at least two tires supporting a vehicle is provided. The method includes the step of providing a drive over reader, which includes a sensor array. A first pressure indication is determined with the drive over reader, and is a pressure indication for a first tire. A second pressure indication is determined with the drive over reader, and is a pressure indication for a second tire. A maximum differential threshold is provided. A pressure differential is determined by comparing the first pressure indication to the second pressure indication. A notice is generated with the drive over reader when the pressure differential exceeds the maximum differential threshold.

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

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

"Lateral edges" means a line tangent to the axially outermost tread contact patch or footprint of the tire as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane.

"Net contact area" means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread of the tire divided by the gross area of the entire tread between the lateral edges.

"PSI" means pounds per square inch. <NUM> PSI is equal to <NUM> Pascal.

With reference to <FIG>, an exemplary embodiment of the system <NUM> for evaluation of the pressure of a tire of the present invention is indicated. As shown in <FIG>, the system <NUM> evaluates the pressure of each tire <NUM> supporting a vehicle <NUM>. It is to be understood that the vehicle <NUM> may be any vehicle type and is shown by way of example as a commercial vehicle. In addition, the vehicle <NUM> may include any number of tires <NUM>, and the system <NUM> may evaluate the pressure in any number of the tires on the vehicle.

The tires <NUM> are preferably of conventional construction, and each tire is mounted on a respective wheel <NUM> as known to those skilled in the art. Each tire <NUM> includes a pair of sidewalls <NUM> that extend to a circumferential tread <NUM>. As each tire <NUM> rolls over the ground <NUM>, a footprint <NUM> is created, which is the area of contact of the tread <NUM> with the ground.

With additional reference to <FIG> and <FIG>, the system <NUM> includes a drive over reader <NUM>, which is mounted in or on the ground <NUM>. The drive over reader <NUM> includes a housing <NUM> and at least one sensor <NUM> mounted in the housing. Preferably, an array of load sensors <NUM> is mounted in the housing <NUM>. The driver of the vehicle <NUM> directs the vehicle over the drive over reader <NUM>, which causes each tire <NUM> to roll over the reader. When the tire <NUM> is positioned over the sensor array <NUM>, the array measures the force exerted by the tire.

The pressure of the tire <NUM> is determined from the force measured by the sensor array <NUM>, and may incorporate tire information and/or vehicle information. An exemplary technique for determining the pressure of the tire <NUM> is described in <CIT>. By employing the drive over reader <NUM>, the pressure of the tire <NUM> is determined without invading or accessing the tire cavity. The drive over reader <NUM> includes, or is in electronic communication with, a processor to determine the pressure of the tire <NUM> from the sensor array <NUM>.

As with any measurement technique, the precision and repeatability of the pressure determination by the drive over reader <NUM> are important considerations. Therefore, the system <NUM> is employed after the pressure of each tire <NUM> has been determined by the drive over reader <NUM> to evaluate the pressure measurements of the drive over reader. As mentioned above, the system <NUM> includes and thus is incorporated into the drive over reader <NUM>.

Referring to <FIG> and <FIG>, the system <NUM> provides an evaluation of tire pressure using a pressure differential <NUM> between tires <NUM>. More particularly, the drive over reader <NUM> determines a pressure indication <NUM> for each tire <NUM> on the vehicle <NUM>. By way of example, the vehicle <NUM> may include two front tires 12A and 12B, each of which is mounted on a front axle 34A, and eight additional tires mounted in dual-tire configurations on tandem axles 34B and 34C. The front tandem axle 34B includes two tires 12C and 12D on the left side of the axle, and two tires 12E and 12F on the right side of the axle. The rear tandem axle 34C includes two tires <NUM> and <NUM> on the left side of the axle, and two tires 12I and 12J on the right side of the axle.

In this example, for the front axle 34A, the drive over reader <NUM> provides a first pressure indication 36A of <NUM> pounds per square inch (PSI) for the left tire 12A, and a second pressure indication 36B of <NUM> PSI for the right tire 12B. For the front tandem axle 34B, a third pressure indication 36C of <NUM> PSI is provided for the tire 12C, a fourth pressure indication 36D of <NUM> PSI is provided for the tire 12D, a fifth pressure indication 36E of <NUM> PSI is provided for the tire 12E, and a sixth pressure indication 36F of <NUM> PSI is provided for the tire 12F. For the rear tandem axle 34C, a seventh pressure indication <NUM> of <NUM> PSI is provided for the tire <NUM>, an eighth pressure indication <NUM> of <NUM> PSI is provided for the tire <NUM>, a ninth pressure indication 36I of <NUM> PSI is provided for the tire 12I, and a tenth pressure indication 36J of <NUM> PSI is provided for the tire 12J.

The system <NUM> evaluates the pressure indications <NUM> based upon a pressure differential <NUM> between tires <NUM>. A maximum differential threshold <NUM> is determined for the system and is set at <NUM> PSI in this example. Any of the tires <NUM> may be compared with one another. For example, two tires <NUM> on the same axle <NUM> may be compared to one another, such as the left tire 12A and the right tire 12B on the front axle 34A. Because the left tire 12A has a pressure indication 36A of <NUM> PSI and the right tire 12B has a pressure indication 36B of <NUM> PSI, the pressure differential <NUM> between the tires is <NUM> PSI. The maximum differential threshold <NUM> is <NUM> PSI, and the pressure differential <NUM> thus exceeds the threshold. When the pressure differential <NUM> exceeds the threshold <NUM>, a notice or flag <NUM> is generated that the tires <NUM> being compared have an unacceptable pressure differential and are in a pressure condition that is not optimum for driving.

Also in the system <NUM>, multiple tires <NUM> on multiple axles <NUM> may be compared with one another. For example, the tires 12C, 12D, 12E and 12F on the front tandem axle 34B, and the tires <NUM>, <NUM>, 12I and 12J on the rear tandem axle 34C may all be compared to one another. The maximum indicated pressure <NUM> in this group of tires <NUM> is the fourth pressure indication 36D of <NUM> PSI for the tire 12D, and the minimum indicated pressure in this group of tires is the sixth pressure indication 36F of <NUM> PSI for the tire 12F, yielding a maximum pressure differential <NUM> of <NUM> PSI. The maximum differential threshold <NUM> is <NUM> PSI, and the maximum pressure differential <NUM> thus exceeds the threshold. When the pressure differential <NUM> exceeds the threshold <NUM>, the notice <NUM> is generated that the tires <NUM> in this group have an unacceptable pressure differential and are in a pressure condition that is not optimum for driving.

Turning to <FIG>, the system <NUM> includes and is incorporated into the drive over reader <NUM>. When the notice <NUM> is generated, it is sent through wireless or wired transmission <NUM> along with any other pertinent drive over reader output to a receiving device <NUM>. The receiving device <NUM> may be any device that communicates the notice <NUM> to a technician, vehicle operator, or a fleet manager, such as a computer with a display terminal, a user device, and/or a fleet management server.

In this manner, the system for evaluation of the pressure of a tire <NUM> provides an evaluation of the indicated tire pressure <NUM> as determined by the drive over reader <NUM> using a pressure differential <NUM> between tires <NUM>. The pressure differential <NUM> may be between all of the tires <NUM> or may be limited to a limited number of specifically identified tires. When the maximum pressure differential <NUM> is greater than a predetermined threshold <NUM>, a notification <NUM> is generated.

The system <NUM> evaluates the precision and repeatability of the pressure determination <NUM> by the drive over reader <NUM>, and evaluates the pressure of the tires <NUM> in a current operating condition without the need to invade or access the tire cavity. The system <NUM> provides an evaluation of the tires <NUM> at any tire temperature, as opposed to having to make reference to a recommended cold pressure (RCP) and correct the measured value for temperature compensation.

Claim 1:
A system for evaluation of pressure of at least two tires (<NUM>) supporting a vehicle (<NUM>), the system (<NUM>) including:
a drive over reader (<NUM>) including a sensor array (<NUM>);
a first pressure indication, the first pressure indication being a pressure indication for a first tire determined by the drive over reader (<NUM>);
a second pressure indication, the second pressure indication being a pressure indication for a second tire determined by the drive over reader (<NUM>);
a maximum differential threshold (<NUM>);
a pressure differential (<NUM>), the pressure differential being determined by comparing the first pressure indication to the second pressure indication; and
a notice (<NUM>) generated by the drive over reader (<NUM>) when the pressure differential (<NUM>) exceeds the maximum differential threshold (<NUM>);
wherein the first tire is disposed on a first axle and the second tire is disposed on a second axle; characterized in that
the system (<NUM>) is configured to determine the pressure differential (<NUM>) by comparing a maximum indicated pressure from the plurality of tires to a minimum indicated pressure from the plurality of tires.