Abstract: A transmitter for a tire condition monitoring apparatus includes a pressure sensor for detecting of the internal pressure of a tire, a transmission circuit for generating a transmission signal, and a transmission antenna for transmitting the transmission signal as a radio wave. The transmission antenna is a planar antenna and includes a plate-like transmission conductor for transmitting the radio wave. The transmission antenna is configured such that the radio wave transmitted from the transmission conductor becomes a circularly polarized wave. As a result, the transmitter has a superior transmission performance and a reduced size.

Abstract: A tire condition monitoring device mounted on a wheel assembly with a tire and executing wireless signaling to a vehicle body, includes an electric circuit further including a sensor detecting a condition of the tire and a wireless circuit executing wireless signaling to transmit results of detection by the sensor, a DC power supply supplying power to the electric circuit, a pair of power lines connecting the DC power supply and the electric circuit to each other, and inductor elements connected to the paired power lines respectively.

Abstract: A tire valve unit (U) having a tire valve (1) and a tire sensor (2) is mounted on a wheel rim (R). In the tire valve unit, a rigid annular member (collar 30) is secured to an open end of the resilient cylindrical member (20). A housing (40) has an extended portion (42) with a passage (40a) defined therein. The extended portion is engaged with the rigid annular member in the resilient cylindrical member, such that an annular space (S1) is defined between a first engaging portion (21) and a second engaging portion (22). The annular space communicates with outside of the housing through the passage of the extended portion, and introduces air pressure into the annular space, to press the resilient cylindrical member to the rim.

Abstract: A transmitter is located in a tire of a vehicle and transmits data indicating a tire condition using a carrier wave. The transmitter has an oscillator circuit and a transmission controller. The oscillator circuit generates the carrier wave. The transmission controller compensates a deviation of the amplitude of the carrier wave generated by the oscillator circuit relative to a predetermined reference value such that the amplitude of the carrier becomes equal to the reference value. This is capable of maintaining a constant amplitude of a carrier wave.

Abstract: A pressure sensor has a diaphragm that is exposed to air in a tire of a vehicle. A transmitter wirelessly transmits data representing the air pressure of the tire. A casing accommodates the transmitter and the pressure sensor. A lid closes an opening of the casing. A metal body is provided on the lid. When the opening of the casing is closed with the lid, the diaphragm is covered with the metal body.

Abstract: A transmitter for a tire condition monitoring apparatus includes a circuit board, circuit components mounted on a main surface of the circuit board, and a transmission antenna that transmits a transmission signal as radio waves. The transmission antenna includes a loop shaped transmission conductor that transmits radio waves. The transmission conductor has a loop plane that is substantially perpendicular to the main surface of the circuit board. When the transmitter is attached to the wheel, the loop plane is substantially perpendicular to a portion of the circumferential surface of the wheel that faces the transmitter. As a result, when the transmitter is attached to the wheel, the radio wave transmission efficiency is effectively prevented from being reduced.

Abstract: A transmitter for a tire condition monitoring apparatus includes a pressure sensor for detecting of the internal pressure of a tire, a transmission circuit for generating a transmission signal, and a transmission antenna for transmitting the transmission signal as a radio wave. The transmission antenna is a planar antenna and includes a plate-like transmission conductor for transmitting the radio wave. The transmission antenna is configured such that the radio wave transmitted from the transmission conductor becomes a circularly polarized wave. As a result, the transmitter has a superior transmission performance and a reduced size.

Abstract: A tire monitoring apparatus includes transponders and a transmitter-receiver. Each transponder is provided in one of the tires of a vehicle, and the transmitter-receiver is mounted on the body frame of the vehicle. In response to a predetermined interrogating radio wave, each transponder detects a condition of the corresponding tire and wirelessly transmits data representing the detected condition of the tire. The transmitter-receiver transmits the interrogating radio wave and receives data wirelessly transmitted by each transponder. In a part of a period during which the corresponding tire rotates through one revolution, each transponder passes through a communication range. The transmitter-receiver changes the time interval at which the interrogating radio wave is transmitted such that the interrogating radio wave is transmitted while the transponder is in the communication zone. As a result, the conditions of the tires are always monitored in a reliable manner.

Abstract: A transmitter is located in a tire of a vehicle and transmits data indicating a tire condition using a carrier wave. The transmitter has an oscillator circuit and a transmission controller. The oscillator circuit generates the carrier wave. The transmission controller compensates a deviation of the amplitude of the carrier wave generated by the oscillator circuit relative to a predetermined reference value such that the amplitude of the carrier becomes equal to the reference value. This is capable of maintaining a constant amplitude of a carrier wave.

Abstract: A tire monitoring apparatus includes transponders and a transmitter-receiver. Each transponder is provided in one of the tires of a vehicle, and the transmitter-receiver is mounted on the body frame of the vehicle. In response to a predetermined interrogating radio wave, each transponder detects a condition of the corresponding tire and wirelessly transmits data representing the detected condition of the tire. The transmitter-receiver transmits the interrogating radio wave and receives data wirelessly transmitted by each transponder. In a part of a period during which the corresponding tire rotates through one revolution, each transponder passes through a communication range. The transmitter-receiver changes the time interval at which the interrogating radio wave is transmitted such that the interrogating radio wave is transmitted while the transponder is in the communication zone. As a result, the conditions of the tires are always monitored in a reliable manner.

Abstract: A pressure sensor has a diaphragm that is exposed to air in a tire of a vehicle. A transmitter wirelessly transmits data representing the air pressure of the tire. A casing accommodates the transmitter and the pressure sensor. A lid closes an opening of the casing. A metal body is provided on the lid. When the opening of the casing is closed with the lid, the diaphragm is covered with the metal body.