Systems have been developed to monitor, for example, vehicle tire pressure, and to report the tire pressure to a receiver at a central monitoring station using radio transmissions. A typical remote automotive tire condition monitoring system includes a plurality of tire-based sensory transponders and a central, vehicle-based arrangement. The sensory transponders include a component that senses a tire condition, such as tire inflation pressure or tire temperature. Each transponder is capable of outputting a coded transmission that conveys sensed tire condition information and an identifier for reception by the vehicle-based arrangement. Within the vehicle-based arrangement, an electronic control unit (“ECU”) processes the conveyed information and controls provision of information regarding the sensed tire conditions to a vehicle operator. During operation of such a system, the vehicle operator is readily notified of a current tire condition, such as a low inflation pressure in a tire.
For a vehicle operator to determine which tire has a condition of interest (e.g., a low inflation pressure), information provided to the vehicle operator must unambiguously identify the location (e.g., right front) of the tire that has the condition of interest. In order for the ECU to provide such tire location information, the ECU has a memory that stores tire identification information for comparison with the identification conveyed from the transponder. Also, within the memory, a certain tire location is associated with each stored tire identification. Thus, once a provided identification is matched to a stored identification, a location on the vehicle is associated with the provided tire condition information. Accordingly, the operator is made aware that the tire at a certain location (e.g., right front) has the certain condition (e.g., low inflation pressure).
Changes routinely occur regarding the tires and/or transponders that are associated with a vehicle. The changes can result in new, different transponders being associated with the vehicle, or a rearrangement of the locations of the transponders, via rearrangement of the tires. Examples of such changes occur when one or more new tires with new transponders are mounted on a vehicle (e.g., the placement of the initial set of tires during vehicle manufacture or replacement of one or more tires), when the tires are rotated during routine maintenance, or when a transponder is replaced on an existing tire. It should be readily apparent that new/modified identification and location information regarding the tire must be provided or “taught” to the ECU.
In order to accomplish the “teaching” of the tire identification information to a vehicle-based portion, one known tire identification system is placed in a “learn” mode via actuation of pushbutton(s) on an operator-accessible information panel of the vehicle-based portion. During the learn mode, the vehicle-based portion is in a ready state to receive a distinctive “learn” mode signal transmitted from each of tire-based transmitter of the system. In order to cause each tire-based transmitter to send the “learn” mode signal, a strong magnet is swept over the outside of the associated vehicle tire.
A monitor is located at each tire and periodically takes a measurement of the tire pressure. A pressure signal is generated that corresponds to the pressure within the tire. The monitor transmits the measurement in a radio frequency transmission to the central monitoring station that produces an alarm or a display in response to the measurement. When the tire pressure drops below a predetermined pressure, an indicator is used to signal the vehicle operator of the low pressure.
During assembly and routine maintenance such as tire rotation or tire replacement, the tire pressure system must be calibrated. Calibration involves associating the various tire positions with the pressure transmitters that are located on the tires. One proposed method for calibrating a system uses a magnet device to initiate the calibration. In this system, an internal display panel with locations corresponding to the tire location is activated. When the tire locations are illuminated on the display, the vehicle operator or service technician places the magnet near the indicated tire. The transducer then sends a code corresponding thereto to the central controller. When the indicator indicates another tire location, the magnet must be brought near each tire location until each of the tire locations have a tire registered thereto. One problem with this device is that a separate component such as a magnet must be provided to the vehicle operator that is used only in the calibration process. One problem associated with a separate magnet device is that such a device is subject to loss. Thus, the tire pressure sensing system would be rendered inoperable.
One problem with such systems is the need to program the location of the transmitters at the central station. To be useful, the tire pressure is preferably associated with the tire which originated the measurement when presenting a display or alarm. Each monitor includes identification information that can be transmitted with the measurement. The tire monitor is preferably activated to produce this information and the information is conveyed to the central station and associated with the position of the tire.
In one technique, the tire monitors include a reed switch or other magnetic device. A magnet is passed near the reed switch causing the monitor to transmit a radio frequency transmission that includes identification data. A service technician repeats this process at each wheel and then loads the identification and position information into the central monitoring station.
One drawback with such a system is that because many wheels are made from steel which is a magnetic material, tire pressure sensing systems may not operate properly because the steel wheels may shield the magnetic energy. Therefore, the system may also be rendered inoperable because the pressure transmitter is not activated by the magnet.
Various tire manufacturers have suggested various locations for the pressure sensors. Known systems include coupling a pressure sensor to the valve stem of the tire. Other known systems and proposed systems locate the pressure sensors in various locations within the tire wall or tread.
These previous techniques have been limited in effectiveness. The magnetic programming technique may be subject to interference and crosstalk, for example in a factory where many such tire monitors are being assembled with tires and vehicles. Also, users of modular products are required to purchase a separate tool to interface with tire pressure monitor systems.