Data processing: measuring – calibrating – or testing – Calibration or correction system – Sensor or transducer
Reexamination Certificate
2002-06-03
2004-08-10
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Sensor or transducer
Reexamination Certificate
active
06775632
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to monitoring pressures in pneumatic tires on motor vehicles and, more particularly in conjunction with transponders associated with the tires for transmitting pressure and temperature measurements to an external (e.g., on-board) receiver (reader, or reader/interrogater).
BACKGROUND OF THE INVENTION
Safe, efficient and economical operation of a motor vehicle depends, to a significant degree, on maintaining correct air pressure in all (each) of the tires of the motor vehicle. Operating the vehicle with low tire pressure may result in excessive tire wear, steering difficulties, poor road-handling, and poor gasoline mileage, all of which are exacerbated when the tire pressure goes to zero in the case of a “flat” tire.
The need to monitor tire pressure when the tire is in use is highlighted in the context of “run-flat” (driven deflated) tires, tires which are capable of being used in a completely deflated condition. Such run-flat tires, as disclosed for example in commonly-owned U.S. Pat. No. 5,368,082, incorporated in its entirety by reference herein, may incorporate reinforced sidewalls, mechanism for securing the tire bead to the rim, and a non-pneumatic tire (donut) within the pneumatic tire to enable a driver to maintain control over the vehicle after a catastrophic pressure loss, and are evolving to the point where it is becoming less and less noticeable to the driver that the tire has become deflated. The broad purpose behind using run-flat tires is to enable a driver of a vehicle to continue driving on a deflated pneumatic tire for a limited distance (e.g., 50 miles, or 80 kilometers) prior to getting the tire repaired, rather than stopping on the side of the road to repair the deflated tire. Hence, it is generally desirable to provide a low tire pressure warning system within in the vehicle to alert (e.g., via a light or a buzzer) the driver to the loss of air pressure in a pneumatic tire.
To this end, a number of electronic devices and systems are known for monitoring the pressure of pneumatic tires, and providing the operator of the vehicle with either an indication of the current tire pressure or alerting the operator when the pressure has dropped below a predetermined threshold level.
For example, U.S. Pat. No. 4,578,992 (Galasko, et al; April 1986), incorporated in its entirety herein, discloses a tire pressure indicating device including a coil and a pressure-sensitive capacitor forming a passive oscillatory circuit having a natural resonant frequency which varies with tire pressure due to changes caused to the capacitance value of the capacitor. The circuit is energized by pulses supplied by a coil positioned outside the tire and secured to the vehicle, and the natural frequency of the passive oscillatory circuit is detected. The natural frequency of the coil/capacitor circuit is indicative of the pressure on the pressure-sensitive capacitor.
It is also known to monitor tire pressure with an electronic device which is not merely a passive resonant circuit, but rather is capable of transmitting a radio frequency (RF) signal indicative of the tire pressure to a remotely-located receiver. Such a “transmitting device” may have its own power supply and may be activated only when the pressure drops below a predetermined threshold. Alternatively, the transmitting device may be activated (“turned ON”) by an RF signal from the remotely-located receiver, in which case the receiver is considered to be an “interrogator”. Additionally, the transmitting device may be powered by an RF signal from the interrogator. Additionally, the electronic device which monitors the tire pressure may have the capability of receiving information from the interrogator, in which case the electronic device is referred to as a “transponder”.
As used herein, a “transponder” is an electronic device capable of receiving and transmitting radio frequency signals, and impressing variable information (data) in a suitable format upon the transmitted signal indicative of a measured condition (e.g., tire pressure) or conditions (e.g., tire pressure, temperature, revolutions), as well as optionally impressing fixed information (e.g., tire ID) on the transmitted signal, as well as optionally responding to information which may be present on the received signal. The typical condition of paramount interest for pneumatic tires is tire pressure. “Passive” transponders are transponders powered by the energy of a signal received from the interrogator. “Active” transponders are transponders having their own power supply (e.g., a battery), and include active transponders which remain in a “sleep” mode, using minimal power, until “woken up” by a signal from an interrogator, or by an internal periodic timer, or by an attached device. As used herein, the term “tag” refers either to a transponder having transmitting and receiving capability, or to a device that has only transmitting capability. Generally, tags which are transponders are preferred in the system of the present invention. As used herein, the term “tire-pressure monitoring system” (TPMS) indicates an overall system comprising tags within the tires and a receiver which may be an interrogator disposed within the vehicle.
It is known to mount a tag, and associated condition sensor (e.g., pressure sensor) within each tire of a vehicle, and to collect information from each of these transponders with a common single interrogator (or receiver), and to alert a driver of the vehicle to a low tire pressure condition requiring correction (e.g., replacing the tire). For example, U.S. Pat. No. 5,540,092 (Handfield, et al.; 1996), incorporated in its entirety by reference herein, discloses a system and method for monitoring a pneumatic tire.
FIG. 1
therein illustrates a pneumatic tire monitoring system (
20
) comprising a transponder (
22
) and a receiving unit (
24
).
Examples of RF transponders suitable for installation in a pneumatic tire are disclosed in U.S. Pat. No. 5,451,959 (Schuermann; September 1995), U.S. Pat. No. 5,661,651 (Geschke, et al.; August 1997), and U.S. Pat. No. 5,581,023 (Handield, et al.; December 1996), all incorporated in their entirety by reference herein. The described transponder systems include interrogation units, pressure sensors and/or temperature sensors associated with the transponder, and various techniques for establishing the identity of the tire/transponder in multiple transponder Systems. In most cases, such transponders require battery power.
In some instances, a transponder may be implemented as an integrated circuit (IC) chip. Typically, the IC chip and other components are mounted and/or connected to a substrate such as a printed circuit board (PCB).
Some proposed systems have relatively complex transponder-sensor capabilities, including measurement and reporting of tire rotations and speed, along with tire ID, temperature, and pressure. For example: U.S. Pat. No. 3,562,787 (Koch, et al.; 1996), and U.S. Pat. No. 5,731,754 (Lee, Jr., et al.; 1998), incorporated in their entirety by reference herein.
Transponder Environmental Considerations
The environment within which a tire-mounted transponder must reliably operate, including during manufacture and in use, presents numerous challenges to the successful operation of the transducer. For example, the sensors (e.g., pressure, temperature) used with the transponder preferably will have an operating temperature range of up to 125° C., and should be able to withstand a manufacturing temperature of approximately 177° C. For truck tire applications, the pressure sensor must have an operating pressure range of from about 50 psi to about 120 psi (from about 345 kPa to about 827 kPa), and should be able to withstand pressure during manufacture of the tire of up to about 400 psi (about 2759 kPa). The accuracy, including the sum of all contributors to its inaccuracy, should be on the order of plus or minus 3% of full scale. Repeatability and stability of the pressure signal should fall within a specified accuracy range.
However
Brown Robert Walter
Pollack Richard Stephen
Yones Dale Lee
Barlow John
Cohn Howard M.
Pretlow Demetrius
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