GB2193933A

GB2193933A - A pneumatic vehicle tyre

Info

Publication number: GB2193933A
Application number: GB08716016A
Authority: GB
Inventors: Gerhard Senger
Original assignee: Uniroyal GmbH
Current assignee: Uniroyal GmbH
Priority date: 1986-07-18
Filing date: 1987-07-08
Publication date: 1988-02-24
Anticipated expiration: 2007-07-08
Also published as: IT8721997V0; IT1222015B; GB8716016D0; GB2193933B; JPS6334204A; IT8721257A0; DE3624408A1; FR2601630A1; FR2601630B1

Abstract

The tyre has a low height/width ratio and a tread 7 centrally divided into two halves 5,6 by a groove 8, the surface of each tread half having a small radius of curvature R. The resistance of the tyre to aquaplaning, its suitability in wet conditions and its travelling comfort are improved. <IMAGE>

Description

SPECIFICATION A pneumatic vehicle tyre The invention relates to a pneumatic vehicle tyre, more particularly, the present invention relates to a pneumatic vehicle tyre of a radial carcase construction, having a profiled tread surface which is reinforced by a belt-like insert and has an outer configuration which forms the tyre surface and is fixed by a predetermined, but selectable, radius for the tread surface, which radius is determined by the ratio of height relative to width of the tyre crosssection, and by radii for the tyre shoulders.

Such pneumatic vehicle tyres of a radial carcase construction with a belt-like reinforcement have a tread surface with a configuration which is substantially determined by a single, relatively large radius. A flat surface is thus formed. This configuration is determined in the shoulder region by a small radius which links up with the tread surface radius and forms the transition into the lateral wall of the tyre.

The tread surface configuration, which is thus obtained, has determined for decades the cross-section of pneumatic vehicle tyres, even that of wide pneumatic vehicle tyres. In the case of pneumatic vehicle tyres having a low height: width cross-sectional ratio and hence a broad tread surface, the tread surfaoe configuration has a relatively flat form; this is because the configuration is always flatter with a decreasing height: width ratio of approximately 0.8 to 0.5 and less with an increasing width.

The so-called 'wide' tyres have a number of advantages. However, they can be improved in respect of their aquaplaning behaviour and their suitability in wet conditions, especially at relatively high travelling speeds also, and in respect of travelling comfort. The disadvantages of a low resistance to aquaplaning and unfavourable shock absorption of the moving masses of a wide tyre may be overcome by the provision of a tread surface configuration which has a more favourable form than was the case hitherto.

The technical object resides in rendering the tread surface configuration of a wide tyre rounder in order to obtain a favourable ground hugging surface which ensures a high resistance to aquaplaning, perfect suitability in wet conditions and improved travelling comfort.

According to the present invention there is provided a pneumatic vehicle tyre of a radial carcase construction, having a profiled tread surface which is reinforced by a belt-like insert and has an outer configuration which forms the tyre surface and is fixed by a predetermined, but selectable, radius for the tread surface, which radius is determined by the ratio of height relative to width of the tyre crosssection, and by radii for the tyre shoulders, wherein the outer tread surface configuration is divided-up on a pneumatic vehicle tyre having a low height: width cross-sectional ratio, each half tyre can be fixed by at least one small radius R of a predetermined, but selectable size, and the central region of the tread surface is radially recessed.

According to the invention, this object is achieved in that, with a pneumatic vehicle tyre having a low height: width cross-sectional ratio of 0.7 and less, the tread surface configuration per half tyre is formed by at least one small radius R which determines the crosssection of the half tyre. As a result of providing at least one small radius per half tyre, a rounded configuration per half tyre is produced. Such a configuration has its own favourable ground hugging surface. It is small per half tyre and is rounded both in the direction of travel and in opposition to the direction of travel. The round configuration ensures a substantially improved displacement of water.

The transition between the tread surface halves, which are determined by small radii, is formed by an opposed, radial recess. In consequence, each half tyre has an oval-shaped to D-shaped supporting surface, and such surfaces together ensure a high resistance to aquaplaning. The positive portion of the profile which is lost through the central groove, is partly introduced again in the new, rounded configuration, thereby providing the positive portion with an increased block or rib height.

Deep groove portions enhance the suitability of the tread surface profile in wet conditions.

Furthermore, the larger positive portion does not adversely affect wear; this is because, after the run-in phase, normal central wear will commence. That is to say that, in the case of a twin bulge, only the top portions of the bulges will wear down.

Because the tread surface configuration for wide pneumatic vehicle tyres having a low height: width ratio is divided, by smell radius, into two identically-formed, rounded crosssectional regions with the central region being radially constricted, smaller tyre supporting surfaces which are homologous adjacent each other are now available in a form which is rounded in the direction of travel of the tyre.

In consequence, the risk Qf wide tyres aquaplaning at relatively high speeds is substantially less when compared with the known flat configuration for wide tyres. With the known wide tyre configuration, the tendency to aquaplane is particularly high.

The new tread surface profile, which is divided into two half tyre configurations, is also better from the point of view of drainage for this tread surface profile. The rounder, bulgetype configuration has shorter drainage paths to the shoulder, on the one hand, and to the open central groove, on the other hand.

With a pneumatic vehicle tyre having a conventional single radius configuration, it is known, from British Patent Specification No. 1 071 951, for example, to provide a recess in the centre of the tyre. This arrangement gives a flexible form to the tread surface in conjunction with the additional belt reinforcement ply which is provided in the region of the centre of the tread surface.

The configuration which, according to the application, is more rounded per tread surface half and has a relatively small, oval supporting surface, is advantageous, in respect of its shock absorption property, because short obstacles with transverse grooves, such as potholes and tracks over bridges, for example, may be travelled-over or traversed more satisfactorily due to the round configuration as compared with the flat, roller-like configuration of hitherto-existing wide tyres. The loading on impact, when travelling over such a transverse groove, is more evenly distributed, and the impact does not occur immediately as a sharp jolt, but it is delayed in a damped or shockabsorbent manner before the full impact is felt.

With a wide tyre according to the invention, it is possible to provide more than one configuration adjacent one another, the configuration being rounded by a small radius per half tyre. Such a tread surface half then has two or more configuration regions which are formed by small radii adjacent one another and are each interrupted by a groove.

In the central region of the tyre-the region between the tread surface halves rather more distinctive radial groove is preferably provided.

The invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which: Fig. 1 illustrates a cutaway portion of a wide tyre cross-section having a rounded tread surface configuration in the two halves of the tyre; and Fig. 2 illustrates a cutaway portion of a comparable wide tyre cross-section according to prior art.

The tyre 1 of Fig. 1, which includes a radial carcase 2, a belt-like reinforcement 3 and a tread strip 7, has a divided tread surface configuration 4. This configuration is determined by a respective small radius R for each half tyre 5 end 6. In consequence, the configuration is of a more rounded form then the corresponding tread surface region L of a known wide tyre 8 shown in Fig. 2, wherein the large redius F determines a single flat tread surface configuration.

The configurations of the wide tyre of Fig.

1, which are determined by the small radii R, ere interrupted in the centre of the tread surface by a groove 8. The transition radii are denoted by ü. The groove base may have a flat or rounded form. In Fig. 1, it is rounded through the radius a. The transition from the tread surface 5, 6 into the tyre shoulders 9 is formed in each case by a small radius s.

Such a tyre with twin bulges is similar to having two motorcycle tyres disposed adjacent each other.

As a result of the configuration 4 which, because of small radii R, is rounder than the known wide tyre configuration, the tyre 1 of Fig. 1 is provided with two small oval-shaped to D-shaped ground hugging surfeces which are disposed in a homologous manner adjacent each other and have rounded tips or end portions.

The rounded configuration of the tread surface is far superior to the flat tyre configuration of known wide tyres from the point of view of the displacament of water in the tyre supporting surface. With wide tyres having a rounded configuration, the resistance to aquaplaning at relatively high speeds is greater than that provided by the known flat configuration. In consequence, the suitability of the profile in wet conditions is also improved because the somewhat deeper profile grooves in the rounded configuration 4 increase the negative portion of the profile. In such a case, the central groove 8 improves both the displacement of water and the drainage of the profile.

The round configuration is also advantageous when traversing obstacles with short transverse grooves. Tha full impact is now not easily discernible, because it bulges or spreads-out first before it reaches its peak. In consequence, the shock absorption is more satisfactory and travelling comfort is thereby improved.

Claims

1. A pneumatic vehicle tyre of a radial carcase construction, having a profiled tread surface which is reinforced by a belt-like insert and has an outer configuration which forms the tyre surface and is fixed by a predetermined, but selectable, radius for the tread surface, which radius is determined by the ratio of height relative to width of the tyre crosssection, and by radii for the tyre shoulders, wherein the outer tread surface configuration is divided-up on a pneumatic vehicle tyre having a low height: width cross-sectional ratio, each half tyre can be fixed by at least one small radius R of a predetermined, but selectable size, and the central region of the tread surface is radially recessed.

2. A pneumatic vehicle tyre is claimed in claim 1, in which the tyre has a height: width cross-sectional ratio of 0.7 or less.

3. A pneumatic vehicle tyre as claimed in claim 1 or 2, wherein the radii, which form a rounded tread surface configuration for each half tyre are identical in size.

4. A pneumatic vehicle tyre as claimed in claim 3, in which the rounded tread surface configuration comprises a twin bulge.

5. A pneumatic vehicle tyre as claimed in any preceding claim wherein the recessed portion can be fixad by a radius (a) from radially outside.

6. A pneumatic vehicle tyre, substantially as herainbefore described with referance to Fig. 1 of the accompanying drawings.