TIRE

Abstract

A tyre tread (10) has a groove (12) having a snow trapping device in the form of a dam (14) in it. The dam (14) is attached to a bottom wall (16) of the groove (12), and to side walls (18, 20) of the groove (12). The dam (14) has a first, snow trapping surface (22) and a second, inclined surface (24) which face in opposite sides in the groove longitudinal direction. The second, inclined surface (24) directs the flow of water away from the bottom wall (16). A hole (32) and a sipe (34) form a passageway (30) for water through the dam (14) in the groove longitudinal direction. The passageway reduces water flow recirculation. The whole of the dam (14) is between the side walls (18, 20) of the groove (12).

Claims

1-15. (canceled)

16. A tire comprising: a tread with a groove, the groove having a snow trapping device in it adjacent to a wall of the groove, the snow trapping device having: a first surface facing a first side in a groove longitudinal direction, the first surface being configured to trap snow flowing from the first side in the groove longitudinal direction; and a second surface facing a second side opposite the first side in the groove longitudinal direction, the second surface being inclined to direct water flowing from the second side away from the wall to which the snow trapping device is adjacent, wherein parts of the snow trapping device overlap along the groove longitudinal direction to form a passageway for water through the device in the groove longitudinal direction, and wherein, in a plan view of the tread, at least half of the snow trapping device is positioned between the side walls of the groove.

17. The tire of claim 16, wherein: when the snow trapping device passes through the contact patch of the tire, the parts which overlap are joined to, or in contact with, each other wherein the passageway is formed between the joining or contact point and the adjacent wall.

18. The tire of claim 17, wherein a sipe is provided at the contact point which allows the parts to contact each other.

19. The tire of claim 16, wherein the parts of the device which overlap in the groove longitudinal direction are integrally formed.

20. The tire of claim 16, wherein the passageway comprises a hole formed in the second surface.

21. The tire of claim 16, wherein the passageway comprises a hole formed in the first surface.

22. The tire of claim 16, wherein: when viewed in the groove longitudinal direction, the snow trapping device extends at most halfway across an area of the groove from the wall to which the snow trapping device is adjacent.

23. The tire of claim 16, wherein the second surface directs water flowing from the second side outwards in a tire radial direction.

24. The tire of claim 16, wherein the first surface extends in a direction which is substantially parallel to a groove width direction.

25. The tire of claim 16, wherein the first surface is planar.

26. The tire of claim 16, wherein the second surface is planar.

27. The tire of claim 16, wherein the snow trapping device comprises at least twenty-five percent of a length of a groove section in which it is positioned from an end of the groove section.

28. A tire comprising: a tread with a groove, the groove having a snow trapping device in it adjacent to a wall of the groove, the snow trapping device having: a first surface facing a first side in a groove longitudinal direction, the first surface being configured to trap snow flowing from the first side in the groove longitudinal direction; and a second surface facing a second side opposite the first side in the groove longitudinal direction, the second surface being inclined to direct water flowing from the second side away from the wall to which the snow trapping device is adjacent, wherein the snow trapping device is attached to both a bottom wall and a side wall of the groove.

29. The tire of claim 28, wherein the second surface directs water flowing from the second side outwards in a tire radial direction.

30. The tire of claim 28, wherein the first surface extends in a direction which is substantially parallel to a groove width direction.

31. The tire of claim 28, wherein the first surface is planar.

32. The tire of claim 28, wherein the second surface is planar.

33. The tire of claim 28, wherein the groove is a width direction groove.

34. The tire of claim 28, wherein the first side is an exterior in a tire width direction.

35. The tire of claim 28, wherein the snow trapping device comprises at least twenty-five percent of a length of the groove section in which it is positioned from an end of the groove section.

Description

[0060] A preferred embodiment of the present invention will now be described, purely by way of example, with reference to the drawings in which:

[0061] FIG. 1 is an isometric view of a groove with a snow trapping device of a tire according to a preferred embodiment of the present invention;

[0062] FIG. 2 shows, on the left-hand side, a tread plan view of the tire tread of the tire of the embodiment of FIG. 1, and shows, on the right-hand side, a cross-sectional view taken along line A-A′ in the left-hand view;

[0063] FIG. 3 shows, in the upper view, a schematic cross-sectional view of the groove (lug) of the embodiment of FIG. 1 along the groove longitudinal direction, and in the lower view, a schematic cross-sectional view of a groove (lug) without the snow trapping device;

[0064] FIG. 4 shows a schematic cross-sectional view of the groove (lug) of the embodiment of FIG. 1 along the groove longitudinal direction;

[0065] FIG. 5 is a plan view plot showing the snow density on the tire tread of a tire without a snow trapping device;

[0066] FIG. 6 is a plan view plot showing the snow density on the tire tread of a tire with a snow trapping device according to the embodiment of FIG. 1;

[0067] FIG. 7 is an isometric view of a groove of FIG. 1; and

[0068] FIG. 8 is an elevation view along the groove longitudinal direction of the snow trapping device.

[0069] Referring to FIG. 1, a portion of a tire tread 10 is shown. The tread 10 has a groove (lug) 12 having a snow trapping device in the form of a dam 14 in it. In the present embodiment, the snow trapping device 14 is adjacent to, and attached to, a bottom wall 16 of the groove 12, as well as being adjacent to and attached to a left-hand side wall 18 and a right-hand side wall 20 of the groove 12.

[0070] The groove 12 and snow trapping device 14 are shown when they are not in the contact patch of the tire.

[0071] The dam 14 has a first, snow trapping surface 22 facing a first side in the groove longitudinal direction. In FIG. 1, the first side of the dam 14 is towards the top of FIG. 1. The first, snow trapping surface 22 is configured to trap snow flowing from the first side in the groove longitudinal direction.

[0072] The dam 14 has a second, inclined surface 24 facing a second side in the groove longitudinal direction which is opposite to the first side. In FIG. 1, the second side of the dam 14 is towards the bottom of FIG. 1. The second, inclined surface 24 is inclined so as to direct water flowing from the second side away from the wall to which the snow trapping device is adjacent. In the present embodiment, the surface 24 is inclined with respect to the bottom wall 16 of the groove 12, and directs the flow of water away from the bottom wall 16. The surface 24 does not direct the flow of water away from the side walls 18 and 20 of the groove 12.

[0073] It can be seen from FIG. 1 that the dam 14 has a left-hand part 26 and a right-hand part 28. In the present embodiment, the parts 26 and 28 are integrally formed, but this is not essential. In FIG. 1, the parts 26 and 28 are divided by a dotted line. The parts 26 and 28 overlap along the groove longitudinal direction so as to form a passageway 30 for water through the dam 14 in the groove longitudinal direction.

[0074] It is also shown in FIG. 1 that the whole of the dam 14 is positioned between the side walls 18 and 20 of the groove 12.

[0075] In the present embodiment, the passageway 30 comprises a hole 32 and a sipe 34 which pass through the middle of the dam 14 in the groove width direction. The hole 32 adjoins the sipe 34, and the hole 32 is nearer to the bottom wall 16 of the groove 12 than the sipe 34. The hole 32 passes through the inclined surface 24 and the snow trapping surface 22, and the axis of the hole 32 is parallel to the groove longitudinal direction. The sipe 34 also passes through the inclined surface 24 and the snow trapping surface 22. The sipe 34 may simplify the manufacturing process by allowing the hole 32 to be formed more easily during moulding of the tire. The sipe 34 is sized to close when it passes through the contact patch of the tire, which prevents loss of flow rate. This closing is due to the block barrelling effect. At that time, the passageway 30 consists of just the hole 32.

[0076] In particular, when the dam 14 passes through the contact patch of the tire, the sipe 34 closes so that the parts 26 and 28 contact each other. This means that the passageway 30 consists of just the hole 32, which is formed between the contact point and the bottom wall 16.

[0077] The snow trapping surface 22 is planar, with the plane being normal to the groove longitudinal direction. This provides a blunt end of the dam 14 with which to trap snow. The surface 22 extends from the bottom wall 16 of the groove 12, and also, in the present embodiment, from the left side wall 18 to the right side wall 20.

[0078] The inclined surface 24 is planar and is inclined with respect to the bottom wall 16 of the groove 12. The surface 24 acts as ramp to lift water up and over the dam 14 in a smooth flow. The angle of inclination of the surface 24 is preferably less than 45°, more preferably less than 30°, to avoid abrupt changes of direction of the water flow and to provide a smooth flow.

[0079] The passageway 30 allows water to flow through the dam 14 and acts to reduce flow separation and recirculation downstream of the dam 14 (in particular, downstream of the snow trapping surface 22).

[0080] Referring to FIG. 2, the tire is a snow tire with several sipes provided in each tread block. The tire has a configuration of V-shaped grooves characteristic of a unidirectional tire. The angle of the grooves making up the V shape, with respect to the tire width direction, changes from small to large from the shoulder region to the centre region of the tire. Hence the angle is larger near the tire equatorial plane.

[0081] It can be seen from the tread plan view in FIG. 2 that the dam 14 is positioned approximately in the middle in the groove longitudinal direction of the groove section in which it is located. The groove section extends from the tread end to the intersection with a groove (circumferential groove 40) running in the tire circumferential direction. This groove section has a relatively small angle with respect to the tire width direction. Therefore, snow slides particularly in this groove section during cornering. The contact patch 38 is also shown in FIG. 2 with a dotted line.

[0082] In the present embodiment, the dam 14 is provided only in the shoulder regions of the tire, and only in tire width direction grooves. However, this is not essential, and the dam 14 may be provided elsewhere in addition or alternatively, possibly in grooves other than tire width direction grooves.

[0083] Referring again to FIG. 2, the cross-sectional view along line A-A′ shows the inside of the dam 14. The hole 32 is shown, but the sipe 34 is not. D.sub.G denotes the depth of the groove 12, and D.sub.D the depth of the dam 14. The depth D.sub.D of the dam 14 is, in the present embodiment, about 25% of the depth D.sub.G of the groove 12. Accordingly, in the present embodiment, when viewed in the groove longitudinal direction, the dam 14 extends about a quarter of the way across the area of the groove 12 from the bottom wall 16. In the present embodiment, the dam 14 occupies about 2% of the volume of the groove section. As shown, the dam 14 forms a right-angled triangle in cross-section.

[0084] FIG. 3 illustrates schematically the snow performance of the tire of the preferred embodiment, in comparison to a tire without a snow trapping device.

[0085] In the upper view of FIG. 3, snow flowing along the groove 12 from right to left encounters the dam 14. The depth of the dam 14 is less than the depth of the groove 12. The lower layer of snow encounters the snow trapping surface 22 which prevents the snow flowing any further. The upper layer of snow does not encounter the surface 22, but nevertheless its flow is slowed because of the shear force from the lower layer of snow which has been trapped by surface 22.

[0086] In the lower view of FIG. 3, in contrast, the snow can flow unimpeded along the groove.

[0087] FIG. 4 illustrates schematically the wet performance of the tire of the preferred embodiment.

[0088] In FIG. 4, water flowing along the groove 12 from left to right encounters the dam 14 and in particular the inclined surface 24. The surface 24 directs the flow upwards and away from the bottom wall 16 of the groove 12. Some of the water then flows through the hole 32 parallel to the groove longitudinal direction. The majority of the water continues up the inclined surface 24 and over the top of the dam 14 and then down towards the bottom wall 16 of the groove 12. A recirculation region 36 is shown downstream of the snow trapping surface 22. The flows of water meet in this recirculation region 36, and the flow which has passed through the hole 32 reduces the size of the recirculation region in comparison to the case where there is no flow through the dam 14. This reduces flow losses and improves water drainage from the tire.

[0089] Computer simulations were carried out to model the snow and wet performance of the tire according to the preferred embodiment of the present invention but without the passageway 30. The simulations for the snow performance modelled the tire turning 20° during cornering. The results of the simulations for the snow performance are shown in FIGS. 5 and 6.

[0090] FIG. 5 shows the snow density on the tire tread of a tire without a snow trapping device, and FIG. 6 shows the snow density on the tire tread of a tire with a snow trapping device according to the embodiment of FIG. 1.

[0091] In FIGS. 5 and 6, contour lines join points of equal snow density. In FIG. 6, the area inside the dashed boxes contains the dams 14, and these areas have a low density where the dams 14 are, but have areas of higher snow density around the dams 14 than the corresponding areas in FIG. 5. In FIG. 6, the shape of the contour lines shows that the snow density is high in the circumferential groove 40 as well as in the adjacent tire width direction groove. By comparing FIGS. 5 and 6, it can be seen that the snow density in the circumferential groove 40 in FIG. 6 is higher than in the corresponding area in FIG. 5.

[0092] The results show an increase of about 22% in lateral force when the dams 14 are present in comparison to the case where they are not.

[0093] The results also showed an increase in the amount of snow flowing into the circumferential direction grooves intersecting the groove section in which the dam 14 is located. This contributed to an improvement in grip in the snow. The flow into these circumferential grooves has the following mechanism. During cornering, snow in the contact patch is subject to a force with a component in the width direction of the tire but also with a component in the circumferential direction. (During traction, the circumferential component is upwards in FIG. 2, and left to right in FIGS. 5 and 6). The component in the circumferential direction causes the snow to flow towards the groove section in which the dam 14 is located. However, the snow trapped by the dam 14 causes the snow from the contact patch to be diverted into the circumferential groove 40. This increases the snow density in the circumferential groove 40 and the snow gripping effect.

[0094] As for wet performance, the simulations did not show any significant change in performance due to the presence of the dams 14. However, the simulations were carried out with the assumption that the flow was both inviscid and laminar, because of the technical limitations of the simulation equipment. In reality, it is known that the recirculation region downstream of the dam 14 will be mainly due to viscous and turbulence effects. Therefore, it is to be expected that, in reality, the wet performance will be significantly worse than the simulations show, and also that the presence of the passageway 30 will beneficial to counteract the recirculation.

[0095] An explanation of the preferred dimensions of the features of the snow trapping device (dam) 14 will be made with reference to FIGS. 7 and 8. The dimensions are as follows:

[0096] D.sub.D (Depth of dam 14): 2 mm

[0097] L (Length of dam 14): 4 mm

[0098] W.sub.S (Width of sipe 34): 0.4 mm

[0099] W.sub.H (Width of hole 32): 1 mm

[0100] The dimensions D.sub.D and L mentioned above were used in the simulations, but W.sub.S and W.sub.H were not (because no passageway 30 was modelled in the simulations).

[0101] In the present embodiment, when viewed in the groove longitudinal direction, the dam 14 extends about a quarter of the way across the area of the groove 12 from the bottom wall 16. However, this is not essential. In addition, in the present embodiment, the dam 14 occupies about 2% of the volume of the groove section, but again this is not essential.

[0102] A tire tread 10 has a groove 12 having a snow trapping device in the form of a dam 14 in it. The dam 14 is attached to a bottom wall 16 of the groove 12, and to side walls 18, 20 of the groove 12. The dam 14 has a first, snow trapping surface 22 and a second, inclined surface 24 which face in opposite sides in the groove longitudinal direction. The second, inclined surface 24 directs the flow of water away from the bottom wall 16. A hole 32 and a sipe 34 form a passageway 30 for water through the dam 14 in the groove longitudinal direction. The passageway reduces water flow recirculation. The whole of the dam 14 is between the side walls 18, 20 of the groove 12.