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WO1997017218A1 - Tyre mileage monitoring apparatus and method - Google Patents

Tyre mileage monitoring apparatus and method Download PDF

Info

Publication number
WO1997017218A1
WO1997017218A1 PCT/GB1996/002683 GB9602683W WO9717218A1 WO 1997017218 A1 WO1997017218 A1 WO 1997017218A1 GB 9602683 W GB9602683 W GB 9602683W WO 9717218 A1 WO9717218 A1 WO 9717218A1
Authority
WO
WIPO (PCT)
Prior art keywords
tyre
output signal
periphery
processing means
signal processing
Prior art date
Application number
PCT/GB1996/002683
Other languages
French (fr)
Inventor
John Michael Jessop
Original Assignee
John Michael Jessop
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by John Michael Jessop filed Critical John Michael Jessop
Publication of WO1997017218A1 publication Critical patent/WO1997017218A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C22/00—Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
    • G01C22/02—Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers by conversion into electric waveforms and subsequent integration, e.g. using tachometer generator

Definitions

  • the present invention relates to a method and apparatus for monitoring tyre mileage and relates particularly, but not exclusively, to an apparatus and method for monitoring tyre mileage of heavy goods vehicles.
  • Mileage sensors are known which are connected to the gear box of a vehicle and provide an indication of the mileage travelled by the vehicle.
  • Such conventional mileage detectors suffer from the disadvantage, however, that an indication is only provided of the mileage travelled by the vehicle as a whole, and no indication is given of the mileage travelled by individual tyres . This causes particular problems when individual wheels of a heavy goods vehicles are replaced, such that the various wheels of the vehicle have different mileages.
  • a tyre mileage monitoring device comprising: - a mechanical transducer mounted in use adjacent the periphery of a tyre of a vehicle, for providing an electrical output signal representative of mechanical forces acting on the periphery of the tyre during rotation thereof; and signal processing means for receiving the output signal of the mechanical transducer and providing an output signal representative of changes in the mechanical forces acting on the periphery of the tyre as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground.
  • the mechanical transducer may comprise a piezoelectric crystal for generating a voltage dependent upon mechanical forces acting on the crystal.
  • the mechanical transducer may be mounted to an internal peripheral surface of the tyre.
  • the mechanical transducer may be embedded within the tyre.
  • the mechanical transducer may be mounted to a side wall of the tyre.
  • the signal processing means comprises a pulse generator for generating a series of electrical pulses, each of which represents a change in the mechanical forces acting on the periphery of the tyre, as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground.
  • the signal processing means may further comprise a counter for counting said electrical pulses.
  • the signal processing means can be constructed in a particularly simple and convenient manner for digital processing by, for example a micro-processor.
  • the pulse generator may comprise a CMOS circuit.
  • the signal processing means may further comprise an analogue / digital converter, and said pulse counter may comprise a shift register.
  • the signal processing means further comprises a micro-processor for processing the output of pulse counter and collating data relating to the number of revolutions rotated by the tyre.
  • the signal processing means may provide an output representative of a number of revolutions rotated by the tyre.
  • Data may be periodically collated by the micro-processor, each collation period corresponding to a plurality of revolutions of the tyre.
  • the output signal of the signal processing means may include an identification code unique to the tyre.
  • the device may further comprise radio frequency transmitter means for transmitting the output signal of the signal processing means to a remote station.
  • This provides the advantage of enabling data to be automatically down loaded and analysed at the remote station, such as a heavy goods vehicle depot.
  • the device may further comprise radio frequency receiver means for enabling the device to be interrogated from a remote station.
  • transmission of the output signal of the signal processing means is activated by interrogation of the device via the radio frequency receiver means from the remote station.
  • the device may further comprise pressure sensor means for providing an electrical output signal representative of the pneumatic pressure in the tyre, wherein the output signal of the pressure sensor means is supplied to the signal processing means.
  • the pressure sensor means may include a" piezoelectric element .
  • the device may further comprise temperature sensor means for providing an electrical output signal representative of the temperature of the tyre, wherein the output signal of the temperature sensor means is supplied to the signal processing means.
  • the device as defined above may be included in single transponder unit adapted to be mounted in use adjacent the periphery of the tyre.
  • This provides the advantage of a particularly compact construction, and enables the transponder unit to be conveniently mounted to the tyre during manufacture.
  • a system for monitoring mileage of individual tyres of a vehicle comprising a plurality of devices as defined above, and display means for receiving the output signal of the signal processing means of each said device and displaying mileage travelled by each tyre of the vehicle.
  • the display means may be a computer.
  • the display means may be remote from the vehicle.
  • a method of monitoring mileage of a vehicle tyre comprising: providing a mechanical transducer adjacent the periphery of a tyre for producing an electrical output representative of mechanical forces acting on the periphery of the tyre adjacent the transducer during rotation thereof; and detecting changes in the mechanical forces acting on the periphery of the tyre as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground; and providing an electrical output signal representative of the number of revolutions rotated by the tyre.
  • the step of detecting changes in the mechanical forces acting on the periphery of the tyre may comprise generating electrical pulses representative of the changes in mechanical forces, and counting said pulses.
  • the method may further comprise the step of periodically collating the output signal representative of the number of revolutions stated, wherein a period of collation may correspond to several such revolutions.
  • the method further comprises providing in the output signal an identification code unique to the tyre .
  • the method may further comprise the step of transmitting said output signal via a radio frequency transmitter to a remote station.
  • the method may further comprise a step of initiating transmission of said output signal from a remote station via a radio frequency receiver.
  • the method may further comprise the step of monitoring the pressure in said tyre.
  • the method may further comprise the step of monitoring the temperature of said tyre.
  • Figure 1 is a cross-sectional view of a tyre incorporating a transponder unit embodying an aspect of the present invention.
  • FIG. 2 is a detailed schematic view of the transponder unit of Figure 1.
  • the rubber body of a tyre 1 is shown in cross-section in bold lines, the tyre 1 having side walls 2 and tread region 3.
  • the external shape taken up by the side walls of the tyre 1 when in contact with the ground (not shown) is indicated by dotted lines 4.
  • a transponder unit 5 is mounted at a central region of an internal peripheral wall 6 of the tyre 1 by any suitable means during " manufacture of the tyre, such as fixing by means of adhesive.
  • the transponder may be embedded within the peripheral wall 6 or mounted to one of the side walls 2 internally thereof.
  • the transponder 5 comprises a mechanical detector 7 for producing an electrical output signal representative of mechanical forces acting on the transponder unit 5 when the tyre 1 is rotating.
  • the sensor 7 comprises a piezoelectric crystal of dimensions of the order of 2mm x 5mm mounted within an enclosure and having a pair of wires (not shown) attached thereto, such that when the piezoelectric crystal is subjected to forces, a voltage is generated across the two wires which is dependent upon (e.g. generally proportional to) the forces acting on the piezoelectric crystal.
  • the output of sensor 7 is connected to a CMOS pulse generating circuit 8 which generates a series of electrical pulses, each of which indicates a change in mechanical forces acting on the sensor 7 as a result of the periphery of the tyre 1 adjacent thereto coming into contact with the ground during rotation of the tyre 1.
  • CMOS pulse generating circuit 8 By using a CMOS circuit 8, power consumption of the circuit 8 is minimised.
  • the electrical output of sensor 7 has two constituent parts, a first part representing forces acting on the sensor 7 due to the random but continuous vibrations within the structure of the tyre 1 as the tyre rotates, and a second part which results from a large mechanical impulse each time the periphery of the tyre 1 in the vicinity of the transponder 5 contacts the ground.
  • This mechanical impulse produces a significant voltage pulse which is distinguishable by means of circuit 8 from the general background noise level, such that circuit 8 produces a stream of pulses from its output, each pulse representing a single revolution of tyre 1.
  • circuit 8 produces a stream of pulses from its output, each pulse representing a single revolution of tyre 1.
  • the random but continuous vibrations within the structure of tyre 1 as tyre 1 rotates produces a continuous background voltage noise level which can be used to provide energy to power suitable drive circuit-ry (not shown) for sensor 7, for example by means of charging a suitable capacitor arrangement.
  • the output signal provided by circuit 8 is supplied to an analogue / digital converter 9, which is in turn connected to a micro-processor 10.
  • the micro-processor 10 has memory 11 which includes a CMOS shift register and a counter.
  • the memory 11 of micro-processor 10 also includes an identity code unique to the tyre 1, the function of which will be described below.
  • a pressure sensor 14 comprises a piezoelectric resistance element of dimensions of the order of 3mm x 3mm, rigidly mounted within an enclosure.
  • the pressure sensor 14 is a constant current device and is a 4 terminal device with resistors in a bridge arrangement, such that changes in ambient pressure within the tyre 1 cause corresponding changes in resistance of the piezoelectric element.
  • the constant current is fed through two of the terminals of sensor 14 and the voltage difference across the other two terminals of the sensor 14 are fed into two inputs (not shown) of a differential amplifier 15, the output of which is fed to analogue / digital converter 9.
  • the pressure sensor 14 is calibrated at ambient pressure such that when the sensor 14 is subjected to an external pressure, the piezoelectric element exhibits a change in resistance which is detected at the output.
  • a temperature sensor 16 comprises a resistance bridge in which the temperature co-efficient of resistance is accurately known at room temperature and is used to detect changes in temperature of the body of tyre 1 and / or of the air within the tyre 1 adjacent to the transponder 5.
  • the output of sensor 16 is fed via amplifier 17 to the analogue / digital converter 9.
  • the transponder unit 5 also includes a coil antenna 18 for transmission and receipt of radio frequency signals to and from a remote station (not shown) , the antenna 18 being connected to the microprocessor 10 via input / output circuitry 19.
  • the micro-processor 10 is powered by means of a battery 19, and the timing pulses of micro-processor 10 are generated by a crystal oscillator 13.
  • the voltage and / or current output provided by one or more of sensors 7, 14, 16 may be used to drive the analogue / digital converter 9 and memory 11.
  • a transponder 5 is mounted to each tyre 1 of a heavy goods vehicle (not shown) and a remote station (not shown) communicating with transponder unit 5 by means of radio frequency signals through antenna 18 is mounted at a suitable road side location, such as the gate of a heavy goods vehicle depot.
  • the remote station is designed to communicate with the transponder unit 5 over a distance of the order to 1.5 metres to 3 metres. This enables the remote station to communicate with the transponder 5 at low frequency, which generally does not necessitate special permits.
  • the memory 11 of micro-processor 10 is re-set by means of a radio frequency signal from the remote station through antenna 18 to the micro-processor 10.
  • the sensors 7, 14, 16 then begin to produce output signals representative of the number of revolutions, pressure, and temperature respectively of the tyre 1 subsequently to the vehicle leaving the depot.
  • These signals pass via circuits 8, 15, 17 respectively to analogue / digital converter 9 and are stored in shift register (not shown) of memory 11 of micro ⁇ processor 10.
  • the shift register When the shift register is full, or at a suitable interval such as 1000 revolutions of the tyre 1, the number of counts stored in the shift register is transferred to the micro-processor 10 for integration and summation such that collated data on the mileage, pressure and temperature of the tyre 1 is stored in memory 11 of the micro-processor 10.
  • an interrogation signal is transmitted from the remote station to the transponder 5 via antenna 18.
  • This causes battery 12 to energise transponder 5 to transmit data stored in the memory 11 of the micro-processor 10 via antenna 18 back to the remote station, where it may be stored in a computer or otherwise displayed.
  • the data transmitted from memory 11 also includes an identity code unique to each transponder 5 to avoid confusion between signals transmitted from the different tyres 1 of the heavy goods vehicle. In this way, the micro-processor 10 remains dormant until activated by the remote station when the vehicle returns to the depot, thus saving power of battery 12.
  • the apparatus of Figures 1 and 2 provides a convenient system for monitoring mileage, pressure and temperature of the tyres of a heavy goods vehicle.
  • the system is still useful for monitoring tyre conditions even if the tyre is removed from a vehicle and mounted to another vehicle.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)

Abstract

A tyre mileage monitoring device is disclosed which comprises a transponder unit (5) mounted adjacent a periphery of a tyre (1) of a vehicle. The transponder unit (5) provides an electrical output signal representative of mechanical forces acting on the tyre (1) during rotation thereof. Signal processing means receives the output signal from the transponder unit (5) and provides an output signal representative of changes in the mechanical forces acting on the periphery of the tyre (1) as a result of the periphery of the tyre adjacent the transponder unit (5) coming into contact with the ground.

Description

TYRE MILEAGE MONITORING APPARATUS AND METHOD
The present invention relates to a method and apparatus for monitoring tyre mileage and relates particularly, but not exclusively, to an apparatus and method for monitoring tyre mileage of heavy goods vehicles.
When hazardous materials are transported by road in heavy- goods vehicles, tyre failure can have very serious consequences. Whilst warning in advance of potential tyre failure is often provided by carrying out regular tyre maintenance, recent improvements in the safety and reliability of heavy goods vehicle tyres has resulted in vehicle users taking tyre reliability for granted and overlooking regular maintenance.
Mileage sensors are known which are connected to the gear box of a vehicle and provide an indication of the mileage travelled by the vehicle. Such conventional mileage detectors suffer from the disadvantage, however, that an indication is only provided of the mileage travelled by the vehicle as a whole, and no indication is given of the mileage travelled by individual tyres . This causes particular problems when individual wheels of a heavy goods vehicles are replaced, such that the various wheels of the vehicle have different mileages.
It is an object of the present invention to provide more reliable monitoring of tyre mileage.
According to an aspect of the present invention, there is provided a tyre mileage monitoring device, the device comprising: - a mechanical transducer mounted in use adjacent the periphery of a tyre of a vehicle, for providing an electrical output signal representative of mechanical forces acting on the periphery of the tyre during rotation thereof; and signal processing means for receiving the output signal of the mechanical transducer and providing an output signal representative of changes in the mechanical forces acting on the periphery of the tyre as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground.
By mounting a mechanical transducer directly to a tyre of the vehicle, this provides the advantage of-more directly monitoring the number of revolutions of that tyre of the vehicle, as opposed to the gear box of the vehicle, and the mileage of the tyre can be monitored even if the tyre is removed from that vehicle and mounted to a different vehicle. The mechanical transducer may comprise a piezoelectric crystal for generating a voltage dependent upon mechanical forces acting on the crystal.
The mechanical transducer may be mounted to an internal peripheral surface of the tyre.
Alternatively, the mechanical transducer may be embedded within the tyre.
Alternatively, the mechanical transducer may be mounted to a side wall of the tyre.
In a preferred embodiment of the invention, the signal processing means comprises a pulse generator for generating a series of electrical pulses, each of which represents a change in the mechanical forces acting on the periphery of the tyre, as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground.
The signal processing means may further comprise a counter for counting said electrical pulses.
In this way, the signal processing means can be constructed in a particularly simple and convenient manner for digital processing by, for example a micro-processor.
The pulse generator may comprise a CMOS circuit.
This provides the advantage of low power consumption of the pulse generator.
The signal processing means may further comprise an analogue / digital converter, and said pulse counter may comprise a shift register.
Preferably, the signal processing means further comprises a micro-processor for processing the output of pulse counter and collating data relating to the number of revolutions rotated by the tyre.
The signal processing means may provide an output representative of a number of revolutions rotated by the tyre. Data may be periodically collated by the micro-processor, each collation period corresponding to a plurality of revolutions of the tyre.
By only collating data periodically for a large number of revolutions, this provides the advantage of reducing power consumption of the device.
The output signal of the signal processing means may include an identification code unique to the tyre.
In this way, confusion between the outputs of monitoring devices mounted to different tyres of a vehicle can be minimised.
The device may further comprise radio frequency transmitter means for transmitting the output signal of the signal processing means to a remote station.
This provides the advantage of enabling data to be automatically down loaded and analysed at the remote station, such as a heavy goods vehicle depot.
The device may further comprise radio frequency receiver means for enabling the device to be interrogated from a remote station.
This has the advantage of enabling the output means to remain dormant until activated by the remote station via the radio frequency receiver means.
In a preferred embodiment, transmission of the output signal of the signal processing means is activated by interrogation of the device via the radio frequency receiver means from the remote station.
The device may further comprise pressure sensor means for providing an electrical output signal representative of the pneumatic pressure in the tyre, wherein the output signal of the pressure sensor means is supplied to the signal processing means.
This provides the advantage of enabling the pressure to be monitored in addition to the mileage travelled by the tyre so that optimum fuel consumption can be achieved, and slow punctures can be detected. It also provides the advantage of giving prior warning of catastrophic tyre failure. The pressure sensor means may include a" piezoelectric element .
The device may further comprise temperature sensor means for providing an electrical output signal representative of the temperature of the tyre, wherein the output signal of the temperature sensor means is supplied to the signal processing means.
This provides the advantage of detecting high temperatures of the tyre body, either during use or during re¬ processing (such as re-treading) which often gives advance warning of catastrophic tyre failure.
The device as defined above may be included in single transponder unit adapted to be mounted in use adjacent the periphery of the tyre.
This provides the advantage of a particularly compact construction, and enables the transponder unit to be conveniently mounted to the tyre during manufacture.
According to another aspect of the present invention, there is provided a system for monitoring mileage of individual tyres of a vehicle, the system comprising a plurality of devices as defined above, and display means for receiving the output signal of the signal processing means of each said device and displaying mileage travelled by each tyre of the vehicle.
The display means may be a computer.
The display means may be remote from the vehicle.
According to a further aspect of the invention, there is provided a method of monitoring mileage of a vehicle tyre, the method comprising: providing a mechanical transducer adjacent the periphery of a tyre for producing an electrical output representative of mechanical forces acting on the periphery of the tyre adjacent the transducer during rotation thereof; and detecting changes in the mechanical forces acting on the periphery of the tyre as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground; and providing an electrical output signal representative of the number of revolutions rotated by the tyre.
The step of detecting changes in the mechanical forces acting on the periphery of the tyre may comprise generating electrical pulses representative of the changes in mechanical forces, and counting said pulses.
The method may further comprise the step of periodically collating the output signal representative of the number of revolutions stated, wherein a period of collation may correspond to several such revolutions.
In a preferred embodiment, the method further comprises providing in the output signal an identification code unique to the tyre .
The method may further comprise the step of transmitting said output signal via a radio frequency transmitter to a remote station.
The method may further comprise a step of initiating transmission of said output signal from a remote station via a radio frequency receiver.
The method may further comprise the step of monitoring the pressure in said tyre.
The method may further comprise the step of monitoring the temperature of said tyre.
For a better understanding of the invention, a preferred embodiment of the invention will now be described in detail below, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which: -
Figure 1 is a cross-sectional view of a tyre incorporating a transponder unit embodying an aspect of the present invention; and
Figure 2 is a detailed schematic view of the transponder unit of Figure 1.
Referring in detail to Figure 1, the rubber body of a tyre 1 is shown in cross-section in bold lines, the tyre 1 having side walls 2 and tread region 3. The external shape taken up by the side walls of the tyre 1 when in contact with the ground (not shown) is indicated by dotted lines 4. A transponder unit 5 is mounted at a central region of an internal peripheral wall 6 of the tyre 1 by any suitable means during "manufacture of the tyre, such as fixing by means of adhesive. Alternatively, the transponder may be embedded within the peripheral wall 6 or mounted to one of the side walls 2 internally thereof.
Referring now to Figure 2, the transponder 5 comprises a mechanical detector 7 for producing an electrical output signal representative of mechanical forces acting on the transponder unit 5 when the tyre 1 is rotating. The sensor 7 comprises a piezoelectric crystal of dimensions of the order of 2mm x 5mm mounted within an enclosure and having a pair of wires (not shown) attached thereto, such that when the piezoelectric crystal is subjected to forces, a voltage is generated across the two wires which is dependent upon (e.g. generally proportional to) the forces acting on the piezoelectric crystal.
The output of sensor 7 is connected to a CMOS pulse generating circuit 8 which generates a series of electrical pulses, each of which indicates a change in mechanical forces acting on the sensor 7 as a result of the periphery of the tyre 1 adjacent thereto coming into contact with the ground during rotation of the tyre 1. By using a CMOS circuit 8, power consumption of the circuit 8 is minimised. The electrical output of sensor 7 has two constituent parts, a first part representing forces acting on the sensor 7 due to the random but continuous vibrations within the structure of the tyre 1 as the tyre rotates, and a second part which results from a large mechanical impulse each time the periphery of the tyre 1 in the vicinity of the transponder 5 contacts the ground. This mechanical impulse produces a significant voltage pulse which is distinguishable by means of circuit 8 from the general background noise level, such that circuit 8 produces a stream of pulses from its output, each pulse representing a single revolution of tyre 1. The random but continuous vibrations within the structure of tyre 1 as tyre 1 rotates produces a continuous background voltage noise level which can be used to provide energy to power suitable drive circuit-ry (not shown) for sensor 7, for example by means of charging a suitable capacitor arrangement.
The output signal provided by circuit 8 is supplied to an analogue / digital converter 9, which is in turn connected to a micro-processor 10. The micro-processor 10 has memory 11 which includes a CMOS shift register and a counter. The memory 11 of micro-processor 10 also includes an identity code unique to the tyre 1, the function of which will be described below.
A pressure sensor 14 comprises a piezoelectric resistance element of dimensions of the order of 3mm x 3mm, rigidly mounted within an enclosure. The pressure sensor 14 is a constant current device and is a 4 terminal device with resistors in a bridge arrangement, such that changes in ambient pressure within the tyre 1 cause corresponding changes in resistance of the piezoelectric element. The constant current is fed through two of the terminals of sensor 14 and the voltage difference across the other two terminals of the sensor 14 are fed into two inputs (not shown) of a differential amplifier 15, the output of which is fed to analogue / digital converter 9. The pressure sensor 14 is calibrated at ambient pressure such that when the sensor 14 is subjected to an external pressure, the piezoelectric element exhibits a change in resistance which is detected at the output.
A temperature sensor 16 comprises a resistance bridge in which the temperature co-efficient of resistance is accurately known at room temperature and is used to detect changes in temperature of the body of tyre 1 and / or of the air within the tyre 1 adjacent to the transponder 5. The output of sensor 16 is fed via amplifier 17 to the analogue / digital converter 9.
The transponder unit 5 also includes a coil antenna 18 for transmission and receipt of radio frequency signals to and from a remote station (not shown) , the antenna 18 being connected to the microprocessor 10 via input / output circuitry 19. The micro-processor 10 is powered by means of a battery 19, and the timing pulses of micro-processor 10 are generated by a crystal oscillator 13. In addition to providing power via battery 12, the voltage and / or current output provided by one or more of sensors 7, 14, 16 may be used to drive the analogue / digital converter 9 and memory 11.
The operation of the apparatus shown in Figures 1 and 2 will now be described.
A transponder 5 is mounted to each tyre 1 of a heavy goods vehicle (not shown) and a remote station (not shown) communicating with transponder unit 5 by means of radio frequency signals through antenna 18 is mounted at a suitable road side location, such as the gate of a heavy goods vehicle depot. The remote station is designed to communicate with the transponder unit 5 over a distance of the order to 1.5 metres to 3 metres. This enables the remote station to communicate with the transponder 5 at low frequency, which generally does not necessitate special permits.
As the heavy goods vehicle exits or re-enters the depot and passes the remote station, the memory 11 of micro-processor 10 is re-set by means of a radio frequency signal from the remote station through antenna 18 to the micro-processor 10. The sensors 7, 14, 16 then begin to produce output signals representative of the number of revolutions, pressure, and temperature respectively of the tyre 1 subsequently to the vehicle leaving the depot. These signals pass via circuits 8, 15, 17 respectively to analogue / digital converter 9 and are stored in shift register (not shown) of memory 11 of micro¬ processor 10. When the shift register is full, or at a suitable interval such as 1000 revolutions of the tyre 1, the number of counts stored in the shift register is transferred to the micro-processor 10 for integration and summation such that collated data on the mileage, pressure and temperature of the tyre 1 is stored in memory 11 of the micro-processor 10.
When the vehicle returns to the depot, an interrogation signal is transmitted from the remote station to the transponder 5 via antenna 18. This causes battery 12 to energise transponder 5 to transmit data stored in the memory 11 of the micro-processor 10 via antenna 18 back to the remote station, where it may be stored in a computer or otherwise displayed. The data transmitted from memory 11 also includes an identity code unique to each transponder 5 to avoid confusion between signals transmitted from the different tyres 1 of the heavy goods vehicle. In this way, the micro-processor 10 remains dormant until activated by the remote station when the vehicle returns to the depot, thus saving power of battery 12.
It can therefore be seen that the apparatus of Figures 1 and 2 provides a convenient system for monitoring mileage, pressure and temperature of the tyres of a heavy goods vehicle. The system is still useful for monitoring tyre conditions even if the tyre is removed from a vehicle and mounted to another vehicle.
It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and for the purpose of illustration, and not in any limitative sense, and that various alterations and modifications of the system are possible without departure from the scope of the invention as defined by the appended claims.

Claims

C AIMS :
1. A tyre mileage monitoring device, the device comprising: - a mechanical transducer mounted in use adjacent the periphery of a tyre of a vehicle, for providing an electrical output signal representative of mechanical forces acting on the periphery of the tyres during rotation thereof; and signal processing means for receiving the output signal of the mechanical transducer and providing an output signal representative of changes in the mechanical forces acting on the periphery of the tyre as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground.
2. A device according to claim 1, wherein the mechanical transducer comprises a piezoelectric crystal for generating a voltage dependant upon mechanical forces acting on the crystal .
3. A device according to claim 1 or 2, wherein the mechanical transducer is mounted to an internal peripheral surface of the tyre.
4. A device according to claim 1 or 2, wherein the mechanical transducer is embedded within the tyre.
5. An apparatus according to claim 1 or 2, wherein the mechanical transducer is mounted to a side wall of the tyre.
6. A device according to any one of the preceding claims, wherein the signal processing means comprises a pulse generator for generating a series of electrical pulses, each of which represents a change in the mechanical forces acting on the periphery of the tyre, as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground.
7. A device according to claim 6, wherein the signal processing means further comprises a counter for counting said electrical pulses.
8. A device according to claim 6 or 7, when the pulse generator comprises a CMOS circuit .
9. A device according to any one of claims 6 to 8, wherein the signal processing means further comprises an analogue / digital converter, and said pulse counter comprises a shift register.
10. A device according to any one of claims 6 to 9, wherein the signal processing means further comprises a micro¬ processor for processing the output of the pulse generator and collating data relating to the number of revolutions rotated by the tyre.
11. A device according to claim 1, wherein the signal processing means provides an output representative of a number of revolutions rotated by the tyre.
12. A device according to claims 10 and 11, wherein the signal processing means in use periodically collates data, each collation period corresponding to a plurality of revolutions of the tyre.
13. A device according to any one of the preceding claims, wherein the output signal of the signal processing means includes an identification code unique to the tyre.
14. A device according to any one of the preceding claims, further comprising radio frequency transmitter means for transmitting the output signal of the signal processing means to a remote station.
15. A device according to any one of the preceding claims, further comprising radio frequency receiver means for enabling the device to be interrogated from a remote station.
16. A device according to claims 14 and 15, wherein transmission of the output signal of the signal processing means is activated by interrogation of the device via the radio frequency receiver means from the remote station.
17. A device according to any one of the preceding claims, further comprising pressure sensor means for providing an electrical output signal representative of the pneumatic pressure in the tyre, wherein the output signal of the pressure sensor means is supplied to the signal processing means.
18. A device according to claim 17, wherein said pressure sensor means includes a piezoelectric element.
19. A device according to any one of the preceding claims, further comprising temperature sensor means for providing an electrical output signal representative of the temperature of the tyre, wherein the output signal of the temperature sensor means is supplied to the signal processing means.
20. A device according to any one of the preceding claims, wherein the device is included in a single transponder unit adapted to be mounted in use adjacent the periphery of the tyre.
21. A system for monitoring mileage of individual tyres of a vehicle, the system comprising a plurality of devices according to any one of the preceding claims, and display means for receiving the output signal of the signal processing means of each said device and displaying mileage travelled by each tyre of the vehicle.
22. A system according to claim 21, wherein the display means comprises a computer.
23. A system according to claim 21 or 22, wherein the display means is remote from the vehicle
24. A method of monitoring mileage of a vehicle tyre, the method comprising: providing a mechanical transducer adjacent the periphery of a tyre for producing an electrical output representative of mechanical forces acting on the periphery of the tyre adjacent the transducer during rotation thereof; and detecting changes in the mechanical forces acting on the periphery of the tyre as a result of the periphery of the tyre adjacent the transducer coming into contact with the ground; and providing an electrical output signal representative of the number of revolutions rotated by the tyre.
25. A method according to claim 24, wherein the step of detecting changes in the mechanical forces acting on the periphery of the tyre comprises generating electrical pulses representative of the changes in mechanical forces, and counting said pulses.
26. A method according to claim 24 or 25, further comprising the step of periodically collating the output signal representative of the number of revolutions rotated by the tyre, wherein a period of collation corresponds to a plurality of revolutions.
27. A method according to any one of claims 24 to 26, further comprising the step of providing in the output signal an identification code unique to the tyre.
28. A method according to any one of claims 24 to 27, further comprising the step of transmitting the output signal via a radio frequency transmitter to a remote station.
29. A method according to claim 28, further comprising the step of initiating said transmission of said output signal from a remote station via a radio frequency receiver.
30. A method according to any one of claims 24 to 29, further comprising the step of monitoring the pressure in said tyre.
31. A method according to any one of claims 24 to 30, further comprising the step of monitoring the temperature of said tyre .
32. A tyre mileage monitoring device substantially as hereinbefore described with reference to the accompanying drawings.
33. A tyre mileage monitoring system substantially as hereinbefore described with reference to the accompanying drawings .
34. A tyre mileage monitoring method, substantially as hereinbefore described with reference to the accompanying drawings .
PCT/GB1996/002683 1995-11-07 1996-11-01 Tyre mileage monitoring apparatus and method WO1997017218A1 (en)

Applications Claiming Priority (2)

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GB9522808.6 1995-11-07
GB9522808A GB2307044A (en) 1995-11-07 1995-11-07 Tyre mileage monitoring apparatus and method

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