GB2450723A

GB2450723A - Tyre having tread with lugs and voids

Info

Publication number: GB2450723A
Application number: GB0712944A
Authority: GB
Inventors: Aaron Royce Neumann
Original assignee: Kumho Tire Co Inc
Current assignee: Kumho Tire Co Inc
Priority date: 2007-07-04
Filing date: 2007-07-04
Publication date: 2009-01-07
Also published as: GB0712944D0

Abstract

The tread comprises a plurality of lugs 12a, b and voids 14a, b for the removal of liquid, e.g water, and to allow lug flexing, wherein at least one void has a baffle 20 positioned in it, being moveable by liquid pressure from a closed position to an open position in which liquid may pass through the void past the baffle but preventing sound propagation. A single baffle 20 can extend from one lug side wall or a pair of baffles 20'a, b can respectively extend from opposite side walls. They can be in line or staggered and lateral or angled.

Description

Title: lyre

Description of Invention

This invention relates to a tyre, particularly, but not exclusively, for a motor vehicle. More particularly, but not exclusively, this invention relates to a tyre for use on a vehicle which is intended to be used off-road', e.g. on non-tarmacadam or the like surfaces. Such tyres will hereinafter be referred to as off-road' tyres.

Off-road tyres are typically fitted as standard to 4x4 vehicles or the like to give the vehicle better traction when travelling over rough, slippery or uneven terrain. As with most tyres, off-road tyres include a pair of side walls which are connected by a tread. The tread includes a plurality of tread lugs, which provide a contact surface necessary to give traction, and a plurality of tread voids positioned in between adjacent tread lugs. The tread voids provide space for the tread lugs to flex and deform as they enter and exit the footprint, i.e. the area of the tread which contacts the ground surface. In off-road tyres the tyre voids, and the tyre lugs, are relatively deep when compared to conventional road tyres. This increase in depth is necessary to increase traction between the tyre and the terrain over which the vehicle is travelling; deeper tyre voids permit the tyre lugs to flex more, which allows for improved traction, particularly over rough terrain. In addition, deeper tyre lugs/tyre voids improve self cleaning of the tyre tread because debris, e.g. stones, trapped in the tyre voids, in between the tyre lugs, will often fall out or be expelled when the tyre lugs flex during use.

From 4 February 2004, any new vehicle sold within the EU must be supplied with tyres which meet a European Directive No. 2001/43/EC. In addition, any tyre which is sold from 1 October 2009 as a spare/replacement tyre must also L 2 meet the same European Directive. The EU Directive places an upper limit on the magnitude of sound emitted laterally from a vehicle, to reduce noise impact on local residents and pedestrians, for example. As a result of an increase in tyre lug depth, which gives rise to an increase in vibration of the tyre lugs during use, off-road tyres generally give rise to increased noise levels during use, when compared to conventional designs.

In conventional road tyres, in order to reduce noise levels, some of the tyre voids in the tread, particularly those which extend transversely towards a side wall of the tyre, are often completely or partially blocked by a rubber web which extends across the tyre void and is connected to the tyre lugs at either side of that tyre void. This ensures that sound travelling along the void is partially or completely blocked from leaking along, and out of, the tyre void.

Instead, the noise is directed towards one or more circumferentially extending tyre voids in a central region of the tread and is thus directed outwardly in a direction opposite to that in which the vehicle is travelling, i.e. rearwardly in normal use.

It is an object of the present invention to provide a tyre which addresses some or all of the above mentioned problems.

According to a first aspect of the invention we provide a tyre having a tread defined by a plurality of tyre lugs and tyre voids, wherein the tyre includes at least one baffle positioned in a void and being moveable by liquid pressure from a closed position to an open position in which liquid may pass through the tyre void, past the baffle.

Further features of the invention are set forth in claims 2 to 16 appended hereto.

According to a second aspect of the invention we provide a vehicle wheel including a tyre according to the first aspect of the invention.

According to a third aspect of the invention we provide a vehicle including one or more tyres according to the first aspect of the invention.

Specific and non-limiting embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which:-Figure 1 is a plan view of a tread of a tyre in accordance with the present invention; Figure 2 is a plan view of a section of the tyre tread of figure 1; Figure 3 is a perspective view of a section of the tyre tread of figure 1; and Figure 4 is a cross-sectional view of a part of a tyre tread.

Referring firstly to figure 1 there is shown a plan view of a section of a tread of a tyre 10. The tyre 10 is an off-road tyre and the tyre tread includes a plurality of tyre lugs 12a, 12b which are separated by tyre voids or channels 14a, 14b.

The tyre voids 14a, 14b are deep enough such that they permit the tyre tugs 12a, 12b to move/flex during use of the tyre 10, so that the tyre 10 self-cleans, and so that adequate traction is maintained between the tyre and the terrain, over which it travels.

There are two central tyre voids 14b, each of which extends circumferentially around the tyre 10 in a mid region of the tyre tread. As is conventional, the main purpose of the tyre voids 14b is to provide for effective removal of liquid, usually water, from the footprint (contact patch) of the tyre 10 during use. The ( 4 tyre voids 14a are channels in the tyre tread which lead into/away from the voids 14b and which extend laterally away from the main plane of the tyre 10, substantially transversely towards one of the tyre side walls (not shown). The tyre voids 14a also provide for effective removal of water from the footprint of the tyre 10 during use.

In the example shown in figure 1, in each tyre void 14a there is positioned one or more baffles 20. For the sake of clarity and conciseness, there are four configurations of baffles shown in figure 1 and each will be described separately, although it will be appreciated, of course, that a given tyre may have only one type or a combination of these types of baffle. Positioned in the tyre void 14a farthest to the left in figure 1 is a single baffle 20. The baffle 20 is connected to a side wall of one of the tyre lugs 1 2a and to a bottom of the tyre void 14a. The baffle 20 is angled outwardly towards an open end of the tyre void 14a and is thin enough such that it can be moved outwardly by water pressure. An abutment formation 21 is provided on a side wall of the opposite tyre lug 1 2a and a free edge of the baffle 20 is close to or in contact with the abutment formation 21 when the baffle 20 is in its closed position.

A pair of baffles 20'a, 20'b are positioned in the third from left tyre void 14a (also shown in figure 3). The baffle 20'a is connected to a side wall of the tyre lug 12a to a left side of the tyre void 14a and the baffle 10'b is connected to a side wall of the tyre lug 12a to a right side of the lyre void 14a. The baffles 20'a, 20'b lie substantially in the same plane and each baffle 20'a, 20'b is connected to a bottom of the tyre void 14a. Free edges of the baffles 20'a, 20'b lie close to or in contact with each other, when the baffles 20'a, 20'b are in their closed position.

In the tyre void 14a positioned farthest to the right in figure 1 is a pair of baffles 20"a, 20"b (also shown in figure 3). The baffles 20"a, 20"b are connected to their respective tyre lugs 12a in the same way as the baffles 20'a, 20'b. ( 5

However, the baffles 20"a, 20"b do not lie in the same plane as each other but are angled outwardly, i.e. in a direction along the tyre void 14a towards the outside of the tyre 10. Free edges of the baffles 20"a, 20"b lie close to or in contact with each other, when the baffles 20"a, 20"b are in their closed position.

Finally, in the second from right tyre void in figure 1 there is a further pair of baffles 20"a, 20"b. The baffles 20"a, 20"b are similar to the baffles 20"a, 20"b, but instead of the free edges of the baffles 20"a, 20"b being close to or meeting each other, the free edges overlap when the baffles 20"a, 20"b are in their closed position. In other words, the baffles 20"a, 20"b are staggered, creating a zig-zag' flow path between them.

In the closed position the baffle 20 and baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b are in their neutral position, i.e. the position they adopt when no forces are acting upon them. The baffle 20 and baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b are therefore biased to their closed position, by means, in this example of their manufacture/moulding.

Although not shown in the figures, a baffle 20 or baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b are provided in each tyre void 14a on an opposite side of the tyre (e.g. a side of the tyre which faces inwardly towards the vehicle), although this may not be necessary for noise reduction purposes. Even so, preferably, each transverse tyre void I 4a of the tyre 10 is blocked by a baffle 20 or baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b. It will also be understood that it may not be necessary to block all of the tyre voids 14a, e.g. every other tyre void 14a may be blocked by a baffle 20 or baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b, if that results in a sufficient attenuation of noise.

In these examples the baffles 20, 20'a, 20'b, 20"a, 20"b, 20"a, 20"b are an integral part of the tyre tread, i.e. the baffles 20, 20'a, 20'b, 20"a, 20"b, 20"a, ( 6 20"b are formed during the moulding process which forms the tyre tread and are thus made from a rubber composition. The baffles are thin enough such that they are moveable from their closed position to an open position by liquid pressure. In the closed position the baffle 20 or baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b close, or at least substantially close, the tyre void 14a and in the open position the baffle 20 or the baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b permit liquid to pass along the tyre void 14a, and to exit' the tread.

Due to the restraints of the moulding process it may not be possible for the edge of single baffle 20 to abut the abutment member 21 or for the free edges of the baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b to abut each other perfectly and thus a small gap is usually present. However, any gap between the free edge of the single baffle 20 and the abutment member 21, and any gap between the free edges of the baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b, should preferably be minimised.

During use, as the tyre 10 rotates and the tyre lugs 12a, 12b engage the terrain over which the vehicle is travelling, the tyre lugs 12a, 12b vibrate. Each tyre lug 12a, 12b will have a vibration component which resolves in a direction substantially tangential to the tyre tread and a vibration component which resolves in a direction substantially laterally of the tyre tread. This vibration creates sound waves which propagate away from each tyre lug 12a, 12b in a direction substantially perpendicular to the upright axis of each tyre lug 12a, 12b. This means that the sound waves will travel along the tyre voids 14a, 14b adjacent the tyre lug 12a, 12b. Any sound waves which propagate along the tyre voids 14b will tend to be emitted in a direction opposite to that in which the vehicle is travelling, and will therefore not create any (or much) sound laterally of the vehicle.

In a conventional tyre any sound waves which propagate along the transverse tyre voids 14a of the tread would be emitted laterally of the vehicle and would r 7 thus create noise which could exceed legislative limits. However, in the tyre 10, a substantial amount of the sound waves which propagate along the transverse tyre voids 14a are deflected back into the tyre void 14a, and into the tyre voids 14b, by the baffle 20 or the baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b (see figure 2). Thus the level of sound emitted laterally of the vehicle, when the vehicle is travelling over terrain, is reduced.

When the tyre tread contacts terrain, the tyre lugs 12a, 12b in the footprint are compressed towards each other. This means that when the footprint of the tyre 10 is travelling through a liquid, e.g. a puddle of water, any liquid trapped in the voids 14a, 14b is pressurised and must be ejected from the footprint of the tyre 10 in order to permit the tyre lugs 12a, 12b of the tyre tread to grip the terrain. Any pressurised water in the tyre voids 14b will tend to be ejected out along the tyre voids 14b in a direction forwardly or rearwardly of the vehicle.

Beneficially, due to the flexibility of the baffle 20 and the baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b pressurised water in the tyre voids 14a moves the baffle 20 or baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b to their respective open positions to permit the water to travel along the tyre void 14a. Thus the baffles 20, 20'a, 20'b, 20"a, 20"b, 20"a, 20"b, although reducing the level of sound emitted laterally of the tyre 10, when in their respective closed positions, also permit the tyre 10 to maintain traction with the terrain in wet conditions, by moving to their respective open positions, and allowing the water to be expelled.

Although the bottom of each of the baffles 20'a, 20'b, 20"a, 20"b, 20"a, 20"b is connected to a bottom of its respective tyre void 14a, this is not necessary.

Indeed, the bottom of each baffle could be spaced from the bottom of the tyre void 14a, as shown in Figure 4 for the baffles 20"a, 20"b. Such a configuration would permit the baffles 20"a, 20"b to move more easily under liquid pressure.

It should be noted that the baffles shown in the figures could take many other forms without departing from the scope of the invention. Indeed, although the baffle 20 and baffles 20'a, 20'b, 20"a, 20"b, 20'"a, 20"b are the same depth as the tyre voids 14a, this is not necessary. Indeed, the baffles could be 50%, 75% of the depth of the tyre void or any other appropriate depth, adjusted so that the tyre meets relevant noise level standards, and/or traction standards.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A tyre having a tread defined by a plurality of tyre lugs and tyre voids, wherein the Lyre includes at least one baffle positioned in a tyre void and being moveable by liquid pressure from a closed position to an open position in which liquid may pass through the tyre void, past the baffle.

2. A Lyre according to claim I wherein the baffle is connected to an integral with a tyre lug.

3. A lyre according to claim 1 or claim 2 wherein the baffle is positioned in a transverse tyre void which extends towards a side wall of the Lyre.

4. A lyre according to any preceding claim wherein the baffle is biased towards its closed position.

5. A tyre according to any preceding claim wherein the baffle is connected to or integral with a side wall of a tyre lug.

6. A lyre according to any one of claims 1 to 5 claim wherein the baffle is connected to or integral with a bottom of the tyre void.

7. A Lyre according to any one of claims I to 5 wherein a bottom of the baffle is spaced from a bottom of the tyre void.

8. A Lyre according to any preceding claim wherein an abutment formation is provided on a side wall of the opposite Lyre lug and a free edge of the baffle lies close to the abutment formation when the baffle is in its closed position.

9. A tyre according to any preceding claim wherein two baffles are positioned in the Lyre void.

10. A tyre according to claim 9 wherein each baffle is connected to or integral with a side wall of a respective tyre lug and the baffles extend towards each other.

11. A tyre according to claim 10 wherein free edges of the baffles lie close to each other in their closed position.

12. A tyre according to any one of claims 9 to 11 wherein the baffles are staggered along the tyre void.

13. A tyre according to any preceding claim wherein the baffle(s) is/are angled outwardly towards an open end of the tyre void.

14. The combination of a wheel and a tyre according to any one of claims 1 to 13.

15. A vehicle having a wheel with a tyre according to any one of claims I to 13 connected thereto.

16. A tyre substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.

17. Any novel feature or novel combination of features described herein with reference to and/or as shown in the accompanying drawings.