A WHEEL SENSOR

Field of the Invention

The invention relates to wheel sensors and in particular sensors which sense one or more conditions within a pneumatic tyre of a wheel.

Background to the Invention and Prior Art known to the Applicant(s)

The following patent applications were identified: US4768574; EP0206002; US4953394; EP0361005; EP0376053; ES2061288T; DE19624800; EP0987475; DE10047853; US2002134428; DE202004020121U1; WO9413991; US5173856; US4235184; US4,1 17,281 ; US6218937; WO2004/016455; EP1547826; US2005/0134446; WO0074958; US2005/0023896 and US5033295.

None of the valves/sensors disclosed in the above patent documents would be suitable for sensing the tyre pressure of the outer tyre in a NASCAR two tyre setup. This is because the space between the outer most ply of the outer tyre at the rim level and the outer most ply of the inner tyre is minute. Any protrusion of a bolt or any other securing device would render very difficult if not impossible to achieve the attachment of the inner tyre to the rim prior to attaching the outer tyre. For this reason, the pressure in the inner tyre is

usually sensed without any data being provided or measured for the outer tyre. This can have the consequence of critical tyre conditions going unchecked which can have dangerous consequences particularly in a race car.

Summary of the Invention

In its broadest independent aspect, the invention provides a wheel sensor using sensing means for sensing one or more conditions within a pneumatic tyre of a wheel and an attachment means configured to secure said sensing means to the wheel rim; wherein said attachment means attaches to the rim substantially without any part projecting into the inside of the tyre beyond said rim; and established a link between the medium inside the tyre and said sensing means.

This configuration is particularly advantageous because it allows the conditions within the outer tyre of a NASCAR to be measured. It also allows for straightforward assembly of the tyres onto the rim as there is no obstacle due to a protruding bolt for example. It also allows the electronics element to be changed if necessary without having to replace either the rim or the tyre.

In a further subsidiary aspect, said attachment means is a screw for traversing an aperture in a rim and for attaching to a corresponding recess in a sensor's housing; the screw head being shaped and configured to be retained by said rim within said aperture. This provides a particularly practical structure in terms of assembly and disassembly whilst achieving the advantages listed above.

In a further subsidiary aspect, said screw incorporates a channel through the screw which forms a conduit for linking the medium inside the tyre to sensing means located in said housing. This allows the screw to have a dual function of attaching the sensing means as well as being a channel. It therefore uses minimal components for advantageous straightforward assembly and disassembly.

In a further subsidiary aspect, the wheel sensor housing is cylindrical with an end face for engaging the wheel rim; and incorporates a truncated edge portion so that when the

housing is attached to the rim in close proximity to a bend in the rim profile, the housing is prevented from rotating in use as said edge portion abuts against the rim.

In a further subsidiary aspect, the invention provides an outer and inner tyre combined wheel comprising a wheel sensor according to any of the preceding aspects located within the rim so as to establish a link between the medium inside the outer tyre and sensing means. This will allow the outer tyre conditions to be precisely assessed during, for example, a race.

In a further subsidiary aspect, a second wheel sensor is employed and configured to assess the medium of said inner tyre. The combination of these two sensors will allow the overall wheel condition to be assessed, allowing an accurate picture of the level and conditions of usage of a tyre which will improve the overall safety assessment of the tyre during use.

Brief Description of the Figures

Figure 1 shows a first perspective view of a sensor mounted on a rim.

Figure 2 shows a second perspective view of a sensor mounted on a rim.

Figure 3 shows a part cross-sectional view of a sensor mounted to the outside of the tyre within the rim.

Figure 4 shows the inside of the upper outer housing half of the sensor in a perspective view.

Figure 5 shows a further cross-sectional view of a sensor.

Figure 6 shows a perspective view of a lower outer housing half.

Figure 7 shows a part cross-sectional view of the countersunk screw as mounted between a housing and a rim.

Figure 8 shows a side view of a lower outer housing half

Detailed Description of the Figures

Figure 1 shows a wheel sensor 1 in combination with a wheel rim 2. The wheel rim depicted in the figure is a so-called NASCAR wheel rim which is designed to accommodate two tyres. The combination of tyres on a rim incorporates an inner and an outer tyre. The outer tyre engages the rim along peripheral lines 3 and 4 about the rim.

The wheel sensor 1 is designed to be mounted on the outer side of the rim outside of the tyre within the periphery of the rim. An aperture is cut out in the rim to allow the fitting of a countersunk mounting screw 5. Screw 5 has an external thread 6 about its outer periphery. Matching inner threads will be provided within outer housing half 7 which may be made out of aluminium, an alloy or any other suitable material. Housing half 7 incorporates a flange 8 extending radially outwards at the housing half s upper most region. Two diametrically oppositely located indentations such as D-shaped indentation 9 are provided in the housing half to allow the component to be better gripped by an operator or tooling for fixing the countersunk mounting screw onto the outer housing half 7. These indentations may also allow the housing half to be secured whilst the upper housing half 10 is threaded onto the lower half 7. Lower half 7 incorporates an inner thread 11 for releaseable engagement with outer thread 12 located below flange 13 of the upper half 10 of the outer housing. Flange 13 may incorporate an annular trough in its underside in order to snugly fit over flange 8. Alternatively as shown in figure 1, an annular trough may be located within flange 8 in order to receive o-ring 14 which creates a seal between the upper and lower halves of the outer housing. Similarly, in order to create a seal between the pressurised outer tyre and the atmosphere, an o-ring 15 is provided to be squashed between lower half 7 and wheel rim 2.

The electronic sensing means is housed in a further housing generally referenced 16. Housing 16 has in its upper surface a cylindrical recess 17 for receiving at least one filter. The embodiment of figure 1 shows two filters 18A and 18B located in series on the central axis of the sensor. Housing 16 may be made of nylon and incorporate at its lower extremity four lugs such as lug 19 designed to fit into mating recesses provided in bottom face of housing half 7. In one embodiment, it is envisaged that housing half 7 may be of aluminium. The lugs and recesses may be arranged so that they fit in only position. As an alternative to the lugs and recesses of this kind, the upper surface of the sensor housing may also incorporate two smaller recesses of cylindrical shape designed to receive location pins which would fit into further recesses provided in this alternative embodiment in the inner upper face of housing half 10. These arrangements serve to prevent rotation of the electronic sensor housing within the outer housing. The upper most portion of upper outer half 10 incorporates a number of facets such as facets 40, 41 and 42 which truncate an otherwise substantially cylindrical portion of the half 10. In an alternative, embodiment the contour may be a pentagonal contour. For either of these embodiments, a correspondingly shaped tool may be provided in order to allow the tightening or loosening of the halves.

Figure 2 shows the wheel sensor of figure 1 from the opposite direction of that shown in figure 1. Identical components have retained identical numerical references for clarity.

The head of the countersunk mounting screw 5 can be seen. It incorporates a faceted hexagonal recess 5A for co-operation with a tool for tightening the screw and the housing together. Within the hexagonal recess, the upper part of a channel 22 can be seen allowing the air from the outer tyre to pass the screw in order to reach the electronic sensing means.

In figure 3, identical reference numerals are employed as in the previous figures for identical components. The inside of electronics housing 16 comprises the necessary elements to perform pressure sensing. There is provided a button lithium battery 23 for powering the sensor. A pressure sensing chip 24 is mounted on a circuit board 25. The circuit board comprises an aperture 26 located at a central position of the housing of sufficient diameter to allow air to pass through in order to detect its pressure. The circuit board is tightly attached to housing 16 so that aperture 26 is in line with passage 27 which

extends between aperture 26 and filters 18A and 18B in housing 16. An arrangement of tunnels is provided in the inner surface of the upper outer housing half 10 as shown in greater detail in figure 4 and 5.

Figure 4 shows upper outer housing half 10 showing a number of tunnels 28 and 29. Tunnel 28 extends along the inner surface of half 10 in the longitudinal direction whilst tunnel 29 extends diametrically across the inner surface of end face 30.

The air from the inner side of an outer tyre passes, as shown in figure 5, through counter sunk screw 5 through tunnel 22 into chamber 31. An aperture 32 is provided between chamber 31 and tunnel 28. The air is then allowed to pass through tunnel 28 and tunnel 29 to filters 18A and l8B.

Figure 6 shows lower outer housing half 7 in greater detail. Identical numerical references have been employed for identical components as previously described. This outer housing half incorporates an annular trough 33 suitable for receiving an o-ring. A truncated edge portion 34, which will allow, when the housing is attached to the rim in close proximity to the bend in the rim profile, as shown for example in figure 3, the housing will be prevented from rotating in use as said edge portion will abut against the rim.

When the sensor is used in an outer and inner tyre combined wheel, such as the two-tyre set-up in a NASCAR, it is ideally suited to measure the pressure in the outer tyre. The electronics may be such as to transmit pressure values to an electronic control unit of known kind or to any other receiving means for further processing. A wireless transmitter is therefore envisaged within the wheel sensor unit described above. It is also envisaged to use this kind of sensing in combination with other kinds of sensors such as a sensor located inside the inner tyre if necessary. This would allow the assessment of pressure in the inner and outer tyre to be achieved.

The sensor also incorporates a temperature sensor.

Figure 7 uses identical numerical references for the components described previously. An O-ring 35 is employed between the countersunk screw head and rim 2 to create a seal in order to prevent leaking between the two beads.

Figure 8 uses identical numerical references for the components described previously. The top surface 36 of the housing 7 is bowed in order to fit to the rim and stop the housing from rotating. This housing may be made out of aluminium or any other suitable material such as titanium. Any other suitable alloy or material may be used.

The scope of the invention is defined in the claims which now follow.