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. Regarding tire temperature, most drive over readers are not capable of detecting the temperature of the tire. However, operation of the vehicle often increases the tire temperature, which typically increases tire pressure. By way of example, <NUM> degree Celsius increase in temperature may increase the pressure in a tire by about <NUM> Pascal (<NUM> psi = <NUM> Pa).

Thus, when tire pressure is measured by the drive over reader after extended vehicle operation, the pressure reading may reflect an increased pressure due to the increased tire temperature. The low pressure threshold for a drive over reader is typically based on a recommended inflation pressure for the tire, which is a recommended cold pressure (RCP). Because the measured pressure may be artificially high due to temperature, a tire that has an inflation pressure below the low pressure threshold using recommended cold pressure may undesirably be designated as having an acceptable pressure level.

As a result, there is a need in the art for a system and method for a drive over reader that accounts for high temperature effects on a tire from vehicle operation.

<CIT>, <CIT> and <CIT> describe systems in accordance with the preamble of claim <NUM>.

According to an aspect of an exemplary embodiment of the invention, a system for compensation of a drive over reader tire pressure measurement is provided. The system includes a drive over reader, which includes a sensor array. A pressure indication is determined for each tire in a group of tires by the drive over reader. A recommended cold pressure for the tires is provided. An adjusted recommended pressure for the tires is determined from the pressure indication and the recommended cold pressure, and accounts for temperature effects on the tires. An adjusted low pressure threshold is set at a predetermined level below the adjusted recommended pressure. A notice is generated by the drive over reader for each tire that includes a pressure indication below the adjusted low pressure threshold.

According to another aspect of an exemplary embodiment of the invention, a method for compensating a drive over reader tire pressure measurement is provided. The method includes the step of providing a drive over reader, which includes a sensor array. A pressure indication is determined for each tire in the group of tires with the drive over reader, and a recommended cold pressure for the tires is provided. An adjusted recommended pressure for the tires is determined from the pressure indication and the recommended cold pressure, and accounts for temperature effects on the tires. An adjusted low pressure threshold is set at a predetermined level below the adjusted recommended pressure, and a notice is generated with the drive over reader for each tire that includes a pressure indication below the adjusted low pressure 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.

"Rib" means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves.

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

"Tread Arc Width" means the arc length of the tread of the tire as measured between the lateral edges of the tread.

With reference to <FIG>, an exemplary embodiment of the system <NUM> for compensation of a drive over reader tire pressure measurement of the present invention is shown. As shown in <FIG>, the system <NUM> preferably assesses 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 sensors <NUM>, preferably 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, 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.

Referring to <FIG>, 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. Each one of the tires <NUM> has a recommended cold pressure (RCP) <NUM> and a low pressure threshold <NUM>. In this example, as shown in <FIG>, each tire <NUM> includes a target recommended cold pressure <NUM> that is <NUM> MPa (<NUM> psi), with a low pressure threshold <NUM> of <NUM> MPa (<NUM> psi) below the recommended cold pressure, or <NUM> MPA (<NUM> psi).

As described above, and as shown in <FIG>, the drive over reader <NUM> determines a pressure indication <NUM> for each tire <NUM> on the vehicle <NUM>. In this example, for the front axle 34A, the drive over reader <NUM> provides a first pressure indication 36A of <NUM> MPa (<NUM> psi) for the left tire 12A, and a second pressure indication 36B of <NUM> MPa (<NUM> psi) for the right tire 12B. For the front tandem axle 34B, a third pressure indication 36C of <NUM> MPa (<NUM> psi) is provided for the tire 12C, a fourth pressure indication 36D of <NUM> MPa (<NUM> psi) is provided for the tire 12D, a fifth pressure indication 36E of <NUM> MPa (<NUM> psi) is provided for the tire 12E, and a sixth pressure indication 36F of <NUM> MPa (<NUM> psi) is provided for the tire 12F. For the rear tandem axle 34C, a seventh pressure indication <NUM> of <NUM> MPa (<NUM> psi) is provided for the tire <NUM>, an eighth pressure indication <NUM> of <NUM> MPa (<NUM> psi) is provided for the tire <NUM>, a ninth pressure indication 36I of <NUM> MPa (<NUM> psi) is provided for the tire 12I, and a tenth pressure indication 36J of <NUM> MPa (<NUM> psi) is provided for the tire 12J.

The pressure indication <NUM> in <FIG> is based on cold pressure and not compensated for temperature, and as a result, all of the tires <NUM> are designated as having an acceptable pressure. However, the pressure indication <NUM> may be artificially high due to temperature, resulting in a tire that has an inflation pressure below the low pressure threshold <NUM> being designated as acceptable.

With particular reference to <FIG>, the system <NUM> compensates for temperature by converting the pressure indication <NUM> based on the recommended cold pressure <NUM> to an adjusted recommended pressure (ARP) <NUM>, which accounts for temperature. More particularly, a group <NUM> of the tires <NUM> is selected for a comparison. It is to be understood that any of the tires <NUM> may be compared with one another, as the selected group may include tires on the same axle <NUM> or all of the tires on the vehicle <NUM>. In this example, all of the tires <NUM> on the vehicle <NUM> are in the selected group.

The trend of the pressure indications <NUM> is assessed as to whether the indicated pressure based on the recommended cold pressure <NUM> is above the recommended cold pressure. Of the ten (<NUM>) tires <NUM>, six are above the recommended cold pressure <NUM>, the tires being 12A, 12C, 12D, <NUM>, 12I, and 12J. Two (<NUM>) tires, 12E and <NUM>, are at the recommended cold pressure <NUM>, and two (<NUM>) tires, 12B and 12F, are below the recommended cold pressure. Based on this, the trend is for the pressure indications <NUM> to be above the recommended cold pressure <NUM>.

The pressure indications <NUM> of the tires <NUM> that follow the trend are averaged. In this example, the pressure indication in tires 12A, 12C, 12D, <NUM>, 12I, and 12J are added up, yielding a total pressure of <NUM> MPa (<NUM> psi). The total of <NUM> MPa (<NUM> psi) is divided by the number of tires in trend, which is six (<NUM>), to arrive at an average pressure of <NUM> MPa (<NUM> psi) or <NUM> MPa (<NUM> psi), which is the adjusted recommended pressure <NUM>. The adjusted recommended pressure <NUM> accounts for temperature or heat effects on the tires <NUM>. An adjusted low pressure threshold <NUM> is set below the adjusted recommended pressure <NUM>. In this example, the adjusted low pressure threshold <NUM> is <NUM> MPa (<NUM> psi) below the adjusted recommended pressure <NUM>, or <NUM> MPa (<NUM> psi).

Using the adjusted recommended pressure <NUM> and the adjusted low pressure threshold <NUM>, four (<NUM>) tires, 12B, 12E, 12F, and <NUM> are below the threshold. The drive over reader <NUM> generates a notice <NUM> for each tire 12B, 12E, 12F, and <NUM> that is below the adjusted low pressure threshold <NUM>. Thus, the system <NUM> compensates the pressure indication <NUM> for temperature effects on each tire <NUM> due to operation of the vehicle <NUM>.

The system <NUM> also accounts for a situation in which the tire <NUM> has been operated in cold ambient temperatures and may yield a pressure indication <NUM> that is artificially low due to such low temperatures. When the tire <NUM> has been operated at low ambient temperatures, the trend is for the pressure indications <NUM> to be below the recommended cold pressure <NUM>. In such a case, when the pressure indications <NUM> that follow the trend are averaged, the resulting adjusted recommended pressure <NUM> may be below the recommended cold pressure <NUM>, thereby accounting for cold-temperature operation.

It is to be understood that other pressure and temperature conversions may be employed without affecting the overall concept or operation of the invention. For example, extreme high and/or low indications may be ignored, a mean instead of an average may be employed, and/or conversion of pressure differences to a temperature factor and back to an adjusted recommended pressure <NUM> may be employed.

Turning to <FIG>, as mentioned above, 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 compensation of a drive over reader tire pressure measurement <NUM> accounts and compensates for high temperature effects on a tire <NUM> from operation of the vehicle <NUM>. By using an adjusted recommended pressure <NUM> that accounts for temperature, rather than the recommended cold pressure <NUM>, the probability of a tire <NUM> with a low pressure being approved by the drive over reader <NUM> is reduced. The system <NUM> performs its compensation without the need to invade or access the tire cavity, and without a specific temperature sensor in the tires <NUM> or the drive over reader <NUM>.

Claim 1:
A system for compensation of a drive over reader tire pressure measurement, the system (<NUM>) including:
a drive over reader (<NUM>) including a sensor array (<NUM>);
a pressure indication (36A) that can be determined for each tire (<NUM>) in a group of tires by the drive over reader (<NUM>);
a recommended cold pressure (<NUM>) for the tires (<NUM>);
characterized in that the system (<NUM>) further includes
an adjusted recommended pressure (<NUM>) for the tires (<NUM>), the adjusted recommended pressure (<NUM>) having been determined from the pressure indication (36A) and the recommended cold pressure (<NUM>), the adjusted recommended pressure (<NUM>) accounting for temperature effects on the tires (<NUM>);
an adjusted low pressure threshold (<NUM>) set at a predetermined level below the adjusted recommended pressure (<NUM>); and that the system (<NUM>) is configured
to generate a notice by the drive over reader (<NUM>) for each tire (<NUM>) that includes a pressure indication (<NUM>) below the adjusted low pressure threshold (<NUM>).