WO2001056814A1

WO2001056814A1 - Improved monitoring system

Info

Publication number: WO2001056814A1
Application number: PCT/GB2001/000435
Authority: WO
Inventors: David Vile; John Beckley
Original assignee: Transense Technologies Plc
Priority date: 2000-02-03
Filing date: 2001-02-02
Publication date: 2001-08-09
Also published as: AU3039901A; GB0002514D0; GB2358949A

Abstract

A vehicle having at least one tyre-bearing wheel comprises: (a) a first unit (8) located to the inboard side of the wheel (1), said first unit being adapted to passively detect parameters associated with the condition of the tyre (2), the wheel (1), and/or the associated brakes (s), and to transmit radio frequency data regarding said parameters to a second unit; and (b) said second unit (9) which is located on a vehicular structure to the inboard side of the wheel (1), and is adapted to receive and analyse said data. Also disclosed are wheels (1) suitable for such vehicles, as are kits comprising the first (8) and second (9) units.

Description

IMPROVED MONITORING SYSTEM

The present invention relates to a system for monitoring the condition of tyres on vehicle wheels, as well as the conditions of such wheels themselves, and those of the brakes associated therewith. For example, the present invention relates to the improved monitoring of conditions such as tyre pressure, tyre wear, wheel speed, wheel vibration, brake wear, brake speed, brake temperature, and so forth.

In particular, the present invention relates to a system in which such conditions are passively monitored via radio frequency signals by a transponder comprising, for example, a surface acoustic wave (SAW) device or any other known passively monitored wireless device. Such transponders require no batteries or active electronics of their own.

The applicant's co-pending UK patent application no. 9917579.6 discloses a system for monitoring the air pressure within a pneumatic tyre by using such a SAW device as a passive transponder (as part of the inflation valve on the outer aspect of the tyre) to transmit a warning signal to a remote place.

In addition, in the applicant's further co-pending UK patent application no. 9915052.6, a system is disclosed in which the wear of the tread of a tyre can be monitored by using a passive transponder to also transmit a warning signal to a remote place .

However, in both these systems, the remote place where the receiving unit receives the warning signal is located under the wheel arch of the body of the vehi c 1 e concerned. This arrangement has the following disadvantages :

(a) distortion of the relatively weak signal transmitted by the passive unit may be caused by signals (e.g. from mobile phones) external (or even internal) to the vehicle; and

(b) when the passive transponder unit is formed as part of the inflation valve of the tyre, a varying signal is received by the receiving unit as the tyre rotates .

The present invention seeks to overcome these disadvantages .

Thus, according to a first aspect, the present invention provides a vehicle having at least one tyre-bearing wheel comprising:

(a) a first unit located to the inboard side of the wheel, said first unit being adapted to passively detect parameters associated with the conditions of the tyre, the wheel, and/or the associated brake (s), and to transmit radio frequency data regarding said parameters to a second unit; and

b) said second unit which is located on a vehicular structure to the inboard side of the wheel, and is adapted to receive and analyse said data transmitted by the first unit.

Vehicle wheels and vehicular structures are conventionally made of metal. Thus, in the arrangement of the system of the present invention, such wheels and structures can provide an effective means for protecting the signal of the transmitted data, by suppressing both extraneous internal and external radio frequencies from reaching the first and second units. The present invention, in this way, allows the relatively weak, passively-generated signal transmitted between the first and second units to be protected from potential distortion by extraneous frequencies.

The arrangement of the present invention has the additional advantage of being compatible in terms of tyre and wheel assembly. This is because the first unit, that is the sensor device, may fit existing wheel rim designs utilising the same recess in the wheel rim as is necessarily provided for the standard inflation valve associated with conventional pneumatic tyres. Thus, located on the wall opposite to the standard inflation valve, the sensor device may sit either beneath the tyre wall during assembly and/or be positioned on the inboard side of the wheel .

Further, the system of the present invention can be manufactured at relatively low cost, since existing methods of sealing and installing the standard inflation valve may also be used to install the sensor. Hence, only relatively minor changes to the wheel may be required, if at all.

Typically, the detected parameters are associated either

(i) with the pressure within the tyre and/or with the wear of the tread of the tyre; (ii) with the wheel speed and/or the wheel vibration; (iii) with the wear, speed and/or temperature of the associated brake (s) ; or (iv) with any combination thereof.

When the passive detection is effected by way of one or more SAW devices, the latter are typically excitable by radio frequency transmitted by the second unit and are usually adapted to emit a weak signal (containing data regarding the parameters) back to the second unit after excitation. The concept of such excitation is further described in the applicant's other co-pending UK patent application no. 9925538.2.

Advantageously, the location of the second unit is such that it can easily be arranged to be compatible with additional apparatus that monitors parameters other than tyre, wheel, or brake conditions. Indeed, the arrangement of the system of the present invention greatly facilitates the integration of such other parameters into the second unit's output, which can be relayed to the vehicle's central data bus, or re-transmitted to a remote monitoring station (for example, via satellite) .

The first unit usually comprises a sensor for monitoring the tyre-condition parameters and an antenna for transmitting the data. All commonly used antenna designs may be accommodated including, for example, monopole, di- pole, helical and/or loop designs.

As mentioned above, the passive detection is preferably effected by way of one or more SAW devices. Advantageously, operating such sensor devices with their reference pressure set at the tyre nominal working pressure at room temperature alleviates the requirements for having to incorporate a correcting factor for tyre pressure with regard to changes of temperature, as described in the applicant's above-mentioned co-pending UK application no. 9917579.6.

Further, another advantage of the system of the present invention relates to the output signal. Sensors incorporating SAW devices can be arranged to transmit a signal proportional to local pressure deviations as compared to the pressure pre-set within their reference chambers . The latter pressure is normally set at the nominally correct tyre operating pressure, and such a signal can be used as a quantitative output of pressure.

Alternatively, the output signal can be used simply to activate respectively a (i) green, (ii) amber, or (iii) red light on the vehicle dashboard, as a warning to the driver that either (i) it is safe to drive, (ii) a service should be booked, or (iii) driving is unsafe at that time.

The second unit typically comprises a send and receive antenna, which is preferably static. Such a send and receive antenna may be either a single antenna or a series of sub-antennae. Preferably, it is located around the wheel axle in the form of a ring.

The latter arrangement has the advantage of increasing accuracy, signal strength and consistency of communication between the sensor and the send and receive antenna. This is particularly so when the sensor is arranged to be in close proximity to the antenna, irrespective of the angular position of the wheel. Thus, in a particularly preferred embodiment, the first and second units are in close proximity, for example at a separation distance of between 25 mm and 1500 mm, more preferably between 25 mm and 100 mm.

Thus, the antennae can be, for example, a ring-like module supported by appropriate parts of the vehicular structure. The latter may be, for example in a particularly preferred embodiment, the brake callipers, so that the sensor and antennae are in close proximity. In such an arrangement , the strength of the signal transmitted between the sensor and antenna is not influenced particularly by movements associated either with the suspension system or with the steering system of the vehicle.

However, such a ring type antenna can be situated around the axis of rotation of the wheel on other vehicular structures and with any desired radius about that axis, so long as the antenna remains to the inboard side of the wheel and so long as little distortion to the transmitted signal, for instance by intervening structures , occurs .

Further, if a multiple antennae arrangement is chosen, good communication can be provided between the sensor and antennae even if the vehicle is stationary. This is due to the arrangement providing that at least one antenna will be unimpeded by signal screening by surrounding structures such as, for example, certain arrangements of brake callipers, and thus at least one antenna will be able to send and receive clear signals to and from the sensor.

The antenna or antennae can be constructed of any convenient material, so long as the material has conductive and dielectric character, and may be, for example, in form of a metal strip or made of a metalised plastic .

Preferably, the sensor of the first unit is maintainable or can be re-calibrated in situ, for example by raising the vehicle on a ramp.

Further, the second unit is usually adapted to transmit information indicating with which specific wheel location the unit is associated, preferably said information being independent of which actual first unit is associated with that location. Thus, the vehicle driver can be warned of the tyre condition associated with each particular wheel location.

In a second aspect, the present invention provides a wheel for use on the above-described vehicle, said wheel comprising :

(a) an inflation valve located to the out -board side of the wheel ; and

(b) said first unit located to the inboard side of the wheel .

Further, in a third aspect, the present invention provides a kit comprising:

a) a first unit locatable to the inboard side of a tyre- bearing wheel, said first unit being adapted to passively detect parameters associated with the conditions of the tyre, the wheel, and/or the associated brake (s), and to receive and transmit radio frequency data regarding said parameters to and from a second unit; and

(b) said second unit which is locatable on a vehicular structure to the inboard side of the wheel, and is adapted to receive and analyse said data transmitted by the first unit.

The present invention will now be described in further detail by way of the following non-limiting examples with reference to the accompanying drawings, in which:

Figure la shows a cross-sectional view of a tyre-bearing wheel according to the prior art;

Figure lb shows a cross-sectional view of a tyre-bearing wheel according to one embodiment of the present invention;

Figure 2a illustrates a side view of a send and receive antenna in the form of a ring for use in the present invention;

Figure 2b shows a front cross-sectional view of the antenna of Figure 2a;

Figure 2c shows a side view of a multiple-antennae arrangement for use as a send and receive unit for the present invention;

Figure 2d is a front, cross-sectional view of the antenna of Figure 2c. Figure 3 illustrates a sensor unit according to the invention described in the applicant's co-pending UK patent application no. 9917579.6;

Figures 4a and 4b show an arrangement of SAW devices within a sensor for monitoring pressure for use in the present invention;

Figure 5 illustrates one embodiment of a sensor for use in the present invention; and

Figure 6 depicts another embodiment of a sensor for use in the present invention.

In Figures la and lb a tyre-bearing wheel is shown with a wheel body 1 mounted on a vehicle axle 3 about wheel bearings 4, and with the rim of the wheel body 1 supporting a pneumatic tyre 2. Also shown are brake disks 5 and brake callipers 6.

In conventional arrangements, a SAW device-containing sensor 7a is located, as shown in Figure la, on the external (or outboard) side of the wheel 1. The sensor 7a may be integrated as part of the inflation valve, the latter being used for regulating the air pressure within the tyre 2. Such an arrangement is described in further detail in the applicant's co-pending UK patent application no. 9917579.6. The sensor is located on the outboard side of the tyre, opposite to the internal (or inboard) side that faces the vehicular body, to allow general operator access for the inflation of the tyre 2 via conventional inflation means, such as pumps found at garage forecourts. When the sensor 7a is so located, it is used to transmit signals to an antenna that is typically in the form of a patch antenna 7b and which, of necessity, is also located on the external side of the wheel, usually under the wheel arch, as shown in Figure la.

By contrast, in Figure lb an arrangement according to the present invention is depicted, showing a sensor 8 located on the inboard side of the wheel 1. The sensor may be located adjacent the rim of the wheel in a similar manner to an inflation valve but on the inboard side of the wheel 1.

A send and receive antenna 9 is shown mounted on the brake calliper 6, and this antenna may be in the form of multiple antennae units spaced radially around the axis of axle 3 or a complete ring forming a circumference around the wheel axle 3.

Figures 2a and 2b show front and side views of an antenna in ring form. The antenna material 10 is supported on a ground plane 11a, for example a metalised surface, and is surrounded by dielectric material 13. The antenna material 10 serves to send or receive radio frequency signals. The dielectric material 13 serves to act as an impedance, with its width being adjusted to provide an impedance for the antenna of a value electrically compatible with that of the electronic control unit 14. The latter unit incorporates application-specific integrated circuitry. The greater the width of the dielectric material layer 13 provided, the greater is the impedance of the antenna . In Figure 2b the antenna structure is such that multiple antennae units 18 are arranged circumferentially and symmetrically about the axis lib of the antenna. The individual antennae units are in electrical contact via a transmission line 19. The use of multiple antennae units means that, despite any shadowing of signals by intervening structures such as, for example, the brake callipers 6, at least one antenna unit 18 will be in clear communication with the sensor 8.

The electronic control unit 14 receives a power input 15 from the vehicle's electrical system. A ground 16 is provided as well as an interface 17 for frequency output.

Figure 3 shows a sensor 8 with a facility for recharging pressure within an internal reference chamber. In the embodiment shown, SAW devices 22 are located within a SAW pressure sensor unit 21, as described in the applicant's co-pending UK patent application no. 9917579.6. The sensor 8 has an electrical connection 23 to ground (typically the rim of the wheel body 1) . A rim seal 24 is provided, as well as a protective rubber coating 25. An aperture 26 has a non-return valve for re-charging the reference chamber within the SAW pressure sensor unit 21. The antenna 20 for the sensor 8 is protected by the rubber protective coating 25.

The SAW pressure sensor unit 21 is shown in a schematic form in Figures 4a and 4b. A SAW differential transducer 27 is arranged within the unit 21 so as to form a reference chamber 29 on one side of the transducer 27, with the opposite side of the transducer 27 being in open communication with the air held within the pneumatic tyre 2. The unit 21 is able to passively monitor changes of the pressure of the air within the tyre 2 relative to the pressure within the reference chamber 29.

Figure 5 shows another embodiment of a sensor 8 for use in the present invention. In this embodiment, the sensor 8 comprises a reference chamber 29 having a pre-set pressure that is not re-chargeable.

Figure 6a shows a further embodiment of a sensor 8 for use in the present invention. The primary feature of this embodiment is the screw with a boss type connection 31, which connects to the wheel rim via a sealing washer. A plan view of this embodiment is illustrated in Figure 6b.

The sensors shown in Figures 3 , 5 and 6 are not themselves adapted to additionally be used to inflate the tyre, thus a separate inflation valve is required on the wheel, typically on the outboard side of the wheel to allow ease of operator access.

The present invention provides a means for accurately monitoring parameters associated with vehicular tyres, wheels and/or brakes that involves only passive sensing, but which allows for consistent communication of signals with low distortion by extraneous radio frequencies. The system is compatible with other, known tyre and wheel monitoring methods and does not require expensive modification of existing wheel designs or manufacturing apparatus .

Claims

CLAIMS :

1. A vehicle having at least one tyre-bearing wheel comprising :

(a) a first unit located to the inboard side of the wheel, said first unit being adapted to passively detect parameters associated with the condition of the tyre, the wheel, and/or the associated brake (s) and to transmit radio frequency data regarding said parameters to a second unit; and

(b) said second unit which is located on a vehicular structure to the inboard side of the wheel, and is adapted to receive and analyse said data transmitted by the first unit .

2. A vehicle as claimed in claim 1, wherein the parameters are associated either (i) with the pressure within the tyre and/or with the wear of the tread of the tyre; (ii) with the wheel speed and/or the wheel vibration; (iii) with the wear, speed and/or temperature of the associated brakes (s); or (iv) with any combination thereof.

3. A vehicle as claimed in any preceding claim, wherein the passive detection is effected by way of one or more SAW devices .

4. A vehicle as claimed in claim 4, wherein the SAW device (s) are excitable by radio frequency transmitted by the second unit, and the SAW device (s) are adapted to emit data regarding the parameters back to the second unit after excitation.

5. A vehicle as claimed in any preceding claim, wherein the second unit comprises a send and receive antenna.

6. A vehicle as claimed in claim 5, wherein the send and receive antenna is static relative to the vehicular structure (s) .

7. A vehicle as claimed in either of claims 5 or 6 , wherein the send and receive antenna is either a single antenna or a series of sub-antennae.

8. A vehicle as claimed in any one of claims 5 to 7, wherein the send and receive antenna is located around the wheel axle in the form of a ring.

9. A vehicle as claimed in any preceding claim, wherein the first and second units are in close proximity, at least at one angular position of the wheel, for example wherein the distance therebetween is between 25 mm and 1500 mm, more preferably between 25 mm and 100 mm.

10. A vehicle as claimed in any preceding claim, wherein the second unit is compatible with the monitoring of parameters other than tyre, wheel, or brake conditions .

11. A vehicle as claimed in any preceding claim, wherein the sensor of the first unit is maintainable or can be re-calibrated in situ.

12. A vehicle as claimed in any preceding claim, wherein the second unit is adapted to transmit information indicating with which specific wheel location the unit is associated, preferably said information being independent of which actual first unit is associated with that location.

13. A wheel for use on a vehicle as claimed in any preceding claim, said wheel comprising:

(a) an inflation valve located to the outboard side of the wheel ; and

(b) said first unit to the inboard side of the wheel .

14. A kit comprising:

(a) a first unit locatable to the inboard side of a tyre-bearing wheel, said first unit being adapted to passively detect parameters associated with the condition of the tyre, the wheel, and/or the associated brake (s), and to receive and transmit radio frequency data regarding said parameters to and from a second unit; and

15. A kit as claimed in claim 13, wherein the first unit is adapted to passively detect the parameters by being excited by radio frequency transmitted by the second unit, said first unit being further adapted to emit data regarding the parameters back to the second unit after excitation.

16. A vehicle, a wheel or a kit substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawings.