Tire Pressure Monitoring System

• US 20090072959A1
• Filed: 08/15/2008
• Published: 03/19/2009
• Est. Priority Date: 09/19/2007
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Matsumura, Takafumi
• Granted Patent: US 7,825,781 B2
• Time in Patent Office: Days
• US Class Current: 340/447
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B60C 23/0433 Radio signals
• CPC Class Codes: B60C 23/0462 Structure of transmission protocol

Abstract

A tire pressure monitoring system is capable of ensuring accuracy of the rate of transmission of data via wireless communications without an increase in the number of oscillators and an increase in the cost. The tire pressure monitoring system includes a tire pressure measuring module. The tire pressure measuring module has a microcomputer, an activation control circuit, a pressure sensor, a temperature sensor, a frequency divider, a transmitting circuit, and a battery. The microcomputer has a clock pulse generator, analog-to-digital converter circuits and a controller. The transmitting circuit has an oscillator circuit. The frequency divider divides the frequency of a carrier wave CW output from the oscillator circuit to generate a clock signal, and outputs the clock signal to the controller included in the microcomputer. The clock signal is used for the timing for outputting data to a data signal line DL. The clock signal for high precision data transmission can be generated without the need to provide an expensive oscillator in the microcomputer since the oscillator circuit is used in the transmitting circuit, and the clock signal used for data transmission by the microcomputer is generated by the inexpensive frequency divider.

Claims

1. A tire pressure monitoring system comprising:

a pressure sensor for converting pressure of a gas present in a tire into an electrical signal and outputting the electrical signal;

a converter for converting the electrical signal output from the pressure sensor into a digital value and outputting the digital value;

an oscillator circuit for outputting a carrier wave to be used to wirelessly transmit data output from the converter, the data including information on the pressure of the gas;

a transmitter for wirelessly transmitting the data to the outside of the tire;

a battery for supplying power to the pressure sensor, the converter, and the transmitter; and

a frequency divider for dividing the frequency of the carrier wave output from the oscillator circuit to generate a clock signal and outputting the clock signal to the converter, wherein

the converter uses the clock signal output from the frequency divider for the timing for transmission of the data to the transmitter.

2. The tire pressure monitoring system according to claim 1, wherein

the converter controls the pressure sensor to cause the pressure sensor to be in either one of an operating state and a non-operating state.

3. The tire pressure monitoring system according to claim 1, wherein

the converter controls the transmitter and the frequency divider to cause the transmitter to be in either one of an operating state and a non-operating state and cause the frequency divider to be in either one of an operating state and a non-operating state.

4. The tire pressure monitoring system according to claim 1, wherein

the frequency divider includes a plurality of input terminals, has a plurality of divisors, and selects any one of the input terminals to change a divisor of said plurality of divisors.

5. The tire pressure monitoring system according to claim 1, further comprising a temperature sensor for converting the temperature of the gas present in the tire into an electrical signal and outputting the electrical signal, wherein

the converter converts the electrical signal output from the temperature sensor into a digital value and outputs the digital value.

6. The tire pressure monitoring system according to claim 1, wherein

the converter encodes the data including the information on the pressure of the gas by using a non-return to zero scheme and outputs the encoded data to the transmitter.

7. The tire pressure monitoring system according to claim 1, wherein

the converter outputs information on a voltage of the battery to the transmitter.

8. The tire pressure monitoring system according to claim 1, wherein

the transmitter wirelessly transmits the data to the outside of the tire by using amplitude shift keying modulation.

9. The tire pressure monitoring system according to claim 1, wherein

the transmitter wirelessly transmits the data to the outside of the tire by using frequency shift keying modulation.

10. A tire pressure monitoring system comprising:

a pressure sensor for converting pressure of a gas present in a tire into an electrical signal and outputting the electrical signal;

a converter for converting the electrical signal output from the pressure sensor into a digital value and outputting the digital value;

an oscillator circuit for outputting a carrier wave to be used to wirelessly transmit data output from the converter, the data including information on the pressure of the gas;

a transmitter for wirelessly transmitting the data to the outside of the tire;

a battery for supplying power to the pressure sensor, the converter, and the transmitter; and

a frequency divider for dividing the frequency of the carrier wave output from the oscillator circuit to generate a clock signal and outputting the clock signal to the converter; and

a frequency multiplier for multiplying the frequency of the carrier wave output from the oscillator circuit by a certain value to generate a signal having the multiplied frequency and use the generated signal as a carrier wave to be used wirelessly transmit the data, wherein

the converter uses the clock signal output from the frequency divider for the timing for transmission of the data to the transmitter.

11. A tire pressure monitoring system comprising:

a pressure sensor for converting pressure of a gas present in a tire into an electrical signal and outputting the electrical signal;

a converter for converting the electrical signal output from the pressure sensor into a digital value and outputting the digital value;

an oscillator circuit for outputting a carrier wave to be used to wirelessly transmit data output from the converter, the data including information on the pressure of the gas;

a transmitter for wirelessly transmitting the data to the outside of the tire;

a battery for supplying power to the pressure sensor, the converter, and the transmitter; and

a frequency divider for dividing the frequency of the carrier wave output from the oscillator circuit to generate a clock signal and outputting the clock signal to the converter; and

a receiving circuit for receiving a wireless signal from the outside of the tire and outputting the received signal to the converter, the signal indicating an operation condition, wherein

the converter uses the clock signal output from the frequency divider for the timing for transmission of the data to the transmitter and the timing for a receiving operation of the receiving circuit.